Dissertations / Theses on the topic 'Forest ecology Australia, Southern'

There is growing interest in airborne lidar for forest carbon accounting and precision forestry purposes. Airborne lidar systems offer a cost-effective, versatile, operationally flexible and robust sampling tool for forest managers. The objective of this study was to develop and test lidar canopy surface enhancement and segmentation processes for estimating dominant above-ground biomass (DAB) in a harvested eucalypt forest on the Central Coast of New South Wales (Australia). The Crown Infill, Trim and Smooth (CITS) process, incorporating a series of filters, algorithms, and selective multi-stage smoothing, was used to enhance lidar canopy surfaces prior to segmentation. Canopy segmentation was achieved using a vertical crown template approach termed the Spatially and Morphologically Isolated Crest (SMIC) process. SMIC delineates dominant tree crowns by detecting elevated crown crests within a 3D lidar canopy surface. Consolidated crown units constitute the basic sampling, analysis and reporting units for wall-to-wall forest inventory. The performance, sensitivity and limitations of these procedures were evaluated using a combination of simulated forest models and actual lidar forest data. Automated crown polygons were used as a sampling template to extract dominant tree height values which were converted to DAB estimates via height-to-biomass relationships derived from field survey and on-site destructive sampling. Results were compared with field based tree height and biomass estimates. Compared against a manually derived crown map from a 2ha field plot, canopy segmentation results revealed a producer???s accuracy of 76% and overall accuracy of 67%. Results indicated a trend toward greater crown splitting (fragmentation) as trees increase in age, height, stem diameter and crown size. Extracted dominant tree height values were highly correlated with ground survey height estimates (r2 0.95 for precision survey and r2 0.69 for standard survey). There was also no significant difference between SMIC and manual crown height estimates. SMIC units overestimated ground-based DAB by 5%; this increased to 36% with the inclusion of segmentation errors. However, SMIC estimation of total plot above-ground biomass (AGB) was within 9% of the ground-based estimate. Results are encouraging considering the mixed-species, multi-aged composition of the forest, and the combined effects of SMIC segmentation and lidar height errors.

This thesis explores issues relating to the application of physiological-process models (???process models???) of forest growth to mixed species, mixed age forests, in particular the coastal blackbutt forests of New South Wales. Using a dataset provided by State Forests of New South Wales (Carter 1994 unpubl.) a numeric description of the forest was developed and stand-level parameters of interest were derived, in particular the plot by plot stemwood volume growth from 1975 to 1999. The amounts of harvested volume, volume that died and volume that grew into the measurement population were identified separately, and several different means of accounting for volume change over time were investigated. A method for quantifying the impact of harvesting and other silvicultural practices on the growth of the forest was developed and programs were written to convert the stand-level summary of the harvest impact into a semi-random selection of trees that would be ???harvested??? from the database under the set of silvicultural assumptions (Dore et al. 1999). A number of process models were investigated and reviewed before selecting one particular model, SUSTAIN (Dewar 1997) for adaption to these forests. This model is a relatively simple process model with a small number of input parameters. The model was adapted so that it could be used to compare the SUSTAIN estimate of growth with the growth of an individual stand of trees in the Kendall Forest Management Area, between Wauchope and Taree on the mid-north coast of NSW. To improve the accuracy of the prediction of growth by SUSTAIN, a method of re-setting the state of the stand to the actual condition at the time of remeasurement was developed. In addition, the SUSTAIN model was extended to enable two separate levels of canopy to be described and grown separately. Ultimately the model was only partially successful in mirroring the growth predicted by the empirical data. Its partial success is attributed primarily to the difficulties associated with correctly determining the allocation parameters used by the model to assign net photosynthate to the roots, foliage and stemwood. The nature of the change in allocation parameters when the forest stand is disturbed by harvest or fire needs further investigation.

I used age structure to examine the role of fire disturbance and climate on the population dynamics of the subalpine forest in the southern Sierra Nevada. I cored trees on ten 0.1 ha plots (3300-3400 m elevation) that varied in species composition, from single-species foxtail pine (Pinus balfouriana) or lodgepole pine (Pinus contorta, var. murrayana), to mixed-species stands of both pines. Crossdating was used to produce accurate dates of tree recruitment and fire events. Age structure varied by plot species composition: lodgepole pine recruitment pattern is pulsed, sometimes forming single-cohort patches in response to fire; foxtail pine plots have a more steady pattern of recruitment; mixed-species plots show an intermediate recruitment pattern. Fire may maintain a species composition mosaic in the subalpine forest. Foxtail pine regeneration may increase in areas opened by fire, although not immediately following fire. Low-intensity fire may spread over areas larger than previously reported under certain conditions in the subalpine zone. In addition, unusually frequent, extreme, and/or extended periods of drought may severely limit subalpine tree regeneration. Growing season frost events and grazing before 1900 may also have affected trees establishing in the subalpine zone.

This study investigated the ecology of the marsupial brush-tailed phascogale (Phascogale tapoatafa; phascogale) in jarrah forest of Western Australia (WA). The thesis provides a descriptive account of the species' population dynamics, the phascogale’s size and growth, foraging ecology and nesting behaviour. The main work was undertaken between 1992-1995 and information was gathered by capture and by using radiotelemetry. The availability of food sources and refuge sites was examined and the species' immediate response to a logging operation was investigated. On a broader scale, the taxonomy of phascogales in WA was reviewed and their past and present distributions were explored by modelling and examination of museum records. The species has previously been subject to only one detailed study and this was undertaken in the State of Victoria. Both similarities and differences were observed between the phascogales in WA and Victoria. Many of the differences appeared to have a nutritional basis. Phascogales are primarily arboreal insectivores and some of the invertebrates most commonly found in scats and stomachs were not abundant on trees. Nectarivory was very rarely observed (cf. Victoria). While phascogales are generalists in diet, they clearly show preferences for certain foods. The strongly seasonal climate in the southwest (long dry summers and wet winters) and the lack of diversity in tree species and low nectar availability probably limit food for WA phascogales. The dispersed nature of tree invertebrates and the apparent scarcity of some preferred prey, such as beetles, possibly explain the exclusive and often large size of female territories. Phascogales in the study area were smaller and less sexually dimorphic than those in Victoria. Males were 30%, and females 20%, less in weight than those in Victoria. They were similarly smaller in skeletal size. Overall size was also found to vary' between habitat type and between years. In a year of drought phascogales did not achieve typical body size with mature males in that year weighing an average 25% less than usual. The evidence strongly suggests that annual and local availability of food is a major determinant of body size and growth. Such variability in food availability may also be the evolutionary basis behind the litter sizes of WA phascogales. These are smaller than those in Victoria (mode WA = 6, Victoria = 8). The timing of major life-history events was as described for Victorian phascogales, although births occur a little later in the year. All males died at the end of the single annual breeding season (male semelparity) and young took some five to six months to raise to weaning. Some females survived to breed in a second year but the number encountered was low. The toll of lactation probably reduces lifespan and females were often in poor condition at late lactation and maximum maternal effort appears selectively invested in the first litter. Typical of the semelparous species, females initially tried to raise as many young as they have teats. However, there was variation in litter sizes among females. The basis for this was anatomical as females had six, seven or eight teats. Such variation occurred throughout the study area, within litters and appears a State-wide phenomenon. Except in a hybrid Antechinus population, there appears to be no marsupial precedent for intrapopulation and intralitter variation in teat number. In such a strongly selected trait, it is speculated that such variation could only persist if the environment was spatially and/or temporally unstable in terms of food availability. There was no evidence that reduction in teat number was a direct trade-off that improved the chance of surviving to breed on a second occasion, but data were limited. The teat trait is presumably under genetic control and the promiscuous mating behaviour of phascogales may contribute, via multiple paternity, to the intralitter variability observed. In the year of drought litters were significantly female biased. Neither sex were sexually dimorphic until they began foraging for themselves, therefore such bias was unlikely to reduce maternal stress during the drought conditions. The adaptive advantage of the bias was undetermined, but current literature indicates that such bias occurs at conception. However, female offspring probably have better post-weaning survival than males. Examination of refuge requirements showed that natural nest sites were located in tree hollows. The profile of the trees chosen agree with most studies on hollow-nesting species. There was no apparent preference for particular tree species but there was a preference for nesting in older and senescent or dead trees. Females with dependent young showed particular preference for these trees' forms. However, once a tree was used, no tree characteristics measured were predictors of the tree being used on further occasions. Excluding females with young, phascogales typically spent 2-5 days nesting in the one refuge before moving to another. Females moved between alternative refuges more than males and home range maintenance is proposed to account for the difference (males were not territorial cf. females). For both sexes, parasite avoidance might account for the generally low level of nest-site fidelity. Individuals were estimated to use around 27 (males) and 38 (females) different nest-sites during one year of adult life. The parameters of hollows examined showed a preference for using hollows with small entrances. More than predator avoidance, interspecific competition for hollows may explain such selectivity. Following the year of drought, communal nesting was common in autumn and winter. This was in marked contrast to data gathered early in the study and to the nesting behaviour of Victorian phascogales. Communal nesting was probably an energy conserving strategy adopted to compensate for unusually small body size. This behaviour may have been a single year event. However, as phascogales in the area are normally much smaller in body mass than those studied in eastern Australia, they may tend to nest communally in winter or when under conditions of hardship. The immediate response of phascogales to logging was examined. Those affected continued to travel through and feed in the logged areas, which reinforces the concept of high site fidelity among animals. Phascogales were commonly found feeding among ground debris in cut areas indicating flexibility in foraging mode. With rare exceptions they ceased nesting in trees in the logged parts of their territories and confined such nesting to surrounding uncut forest. This suggests that the forestry practice of retaining a select number of hollow-bearing trees/ha may be insufficient to meet the species' refuge requirements in logged areas. Of concern is that currently unlogged sections in logged forest can be cut within 10-20 years yet trees take some 200 years to develop hollows. Additionally, the value of young regrovvth as a food source to this species is questionable. The study highlights the concerns that many scientists have regarding the preservation of hollow-nesting fauna in areas that are impacted by logging. A revision of the species taxonomy (including the subspecies P. t. pirata) indicates that southern WA phascogales warrant subspecies status. Differences in basiacranial features were found between the regional groups in Australia. However, the issue of long-term geographic and reproductive isolation is perhaps the greater argument for suggesting subspecific status for WA phascogales. This is currently being examined using mitochondrial DNA techniques. This will provide not only a DNA profile of similarities and presumed differences between WA and southeastern phascogales, but will give an estimation of the time that the two groups have been separated. A modelling exercise undertaken to examine the potential past distribution of WA phascogales showed that climatic conditions favourable to this species are found throughout the southern part of WA. For many of these areas there are no records of phascogales although a single historical work (1909) indicated that they were present in these areas. At that time they were apparently already extinct in some areas and dying out in others. A survey of the northern jarrah forest and a few other areas (by using nestboxes) failed to detect phascogales. The population examined during this study was therefore quite unusual in density, as phascogales were readily found in nestboxes. A myriad of factors culminating in low feral predation in the area seems the most likely explanation for the high densities observed. The conservation status of phascogales in areas other than the study region requires examination. Predation by exotic predators might account for the species' rarity, but food appears a generally limiting factor for phascogales and processes that alter habitat productivity may significantly impact this species.

This study documented effects of fragmentation and disturbance on a coastal eucalypt dry open-forest plant community at Port Stephens-Myall Lakes, south-eastern Australia. The study evaluated the relative influence of fragment size (range <1-75ha), fragment or edge age (< 1-25y), time since fire (5-25y) and anthropogenic disturbance (minor, major) on microclimate, native plant species richness and weed invasion. Plots were sampled for native and exotic species richness per 25 m2 and edge transects for light, soil moisture, soil temperature, vegetation structure, native species richness and exotic species richness and cover. Depths of edge influence (DEI) were all < 20m inside the forest edge. Younger edge zones were lighter, had hotter and drier soils and more native species than forest interiors. Older edge zones were shadier, had warmer and moister soils and fewer native species than forest interiors, due to vegetation thickening in the edge zone. Light and soil moisture followed linear or monotonic edge-to-interior gradients in younger edges, but more complex patterns in older edges. Soil-temperature DEI decreased with increasing edge age. Fragment size had little influence on edge effects, but those for light developed more rapidly in smaller fragments, and recent fire was associated with reduced richness in edge zones of smaller fragments. Both anthropogenic disturbance and fire enlarged DEI for native species richness. Major anthropogenic disturbance coupled with fragmentation produced a stronger and more immediate loss of native species than fragmentation alone. Small fragments with minor disturbance had fewer native species per 25 m2 than larger fragments, but only after >10y since fragmentation. Analysis of forest interior portions of transects revealed that edge effects, and possibly disturbance, were largely responsible for this loss of native species with time, rather than effects of area. Despite a viable soil seed bank in fragments and the surrounding matrix, weed invasion in fragments was minimal. Exotic species were concentrated in edge zones, and were promoted by major anthropogenic disturbance within fragments. Results were highly dependent on fragment or edge age, and external influences of fragmentation (edge effects and disturbance), were more important than biogeographic (area-driven) factors. Impacts of fragmentation were compounded when combined with disturbance.

This thesis sets out to test the hypothesis that the vegetational patterns in the forested region of south western Australia are primarily determined by the interaction of climate and landform. The region is an area of 4.25 million hectares subject to recent agreement between the Commonwealth of '4ustralia and the state of Western Australia regarding long-term protection and management of forest (Regional Forest Agreement). The climate of the South Western forest region is warm temperate and summer dry, matching Koeppen's category Cs, usually described as mediterranean. The dominant geological features of South Western Australia are crystalline and sedimentary plateaus and coastal plains. They are subject to a complex process of weathering, denudation and re-deposition, which is the key determinant of landforms and soil patterns. Deep but infertile soils are prevalent. The dominant vegetation formation of the region is open forest, which reduces to woodland in the drier north and east and increases to tall open forest in the moister south. Floristically the vegetation is very rich, comprising over 3000 vascular plant species. The richness resides in the forest and woodland understorey and in the shrublands, heathlands and sedgelands of edaphically extreme sites. By comparison, the forest overstorey is very simple, only one or two species being often dominant over extensive areas. The validation of the hypothesis that climate and landforms determine the vegetation patterns in South Western Australia is carried out in the following stages: 1) review of past studies of vegetation patterns in relation to the underlying environmental factors, relating them to one another in terms of floristics, 2) conversion of landform and climate maps for the region into vegetation maps by means of toposequences, that is gradients of topography, soils and vegetation within individual landform/climate combinations, 3) production of two sets of vegetation maps, namely six maps of vegetation complexes (1:250,000) and one map of vegetation systems (1:500,000), 4) testing the predictive capability of the resulting maps by comparing the occurrences of individual species of trees, shrubs and herbs predicted by map legends, with their records in FloraBase, the geographic information system of the Western Australian Herbarium, and 5) using the outcomes of the above studies to assess the validity of the hypothesis. Because the above hypothesis is so broad, it will be considered under seven headings: a) nature of the vegetation patterns (continuum or discrete categories), b) regional effect of climate and local effect of landform, c) effect of landforms on soil depth, texture and fertility, d) joint effect of slope, soil depth and texture on water balance, e) interactive effect of landform and climate on vegetation patterns, f) response of individual species to climate and landform, and g) effect of other factors of environment, such as fire, on vegetation patterns. The subsidiary hypotheses are defined in Chapter 5. It is concluded that the vegetation of the region forms a lumpy continuum from the wet south west to the dry north east. Within that broad continuum there are localised continua from waterlogged sites in depressions to drought-prone sites on steep stony slopes. However, the dominant vegetation of the region is open forest on plateau uplands with deep infertile soils. Although climate and landforms have a strong effect on vegetation patterns, they do not determine all vegetation patterns directly. Some tree species have ranges of occurrence that are too broad for that, and others have ranges that are too restricted. A more probable explanation is that climate and landforms, together with fire, set the stage on which the interplay of species takes place and determines the structure and composition of the vegetation. An attempt is made to predict the likely effect of climatic changes on vegetation patterns. The applicability of the methodology developed to the mapping of other regions, especially the adjacent ones, is examined. A review is made of how the products of the study, in particular the maps, are currently being used, and suggestions are made how they could be used in the future.

In order to fully understand the magnitude of the benefits that forests provide, it is crucial to understand the full suite of ecosystem services that they offer. A southern Appalachian red spruce-Fraser fir forest was intensively analyzed using a variety of methodologies to determine the nature and quantity of some of these services. Many hypotheses exist regarding the future of these spruce-fir forests, which were heavily disturbed by the non-native balsam wooly adelgid during the 1980s. Direct measurements over the course of a decade assessed these hypotheses and indicate that this forest is recovering structure and function. The forest is accruing overstory biomass, with vegetation composition on a trajectory towards historic conditions. By using a total forest inventory of all vegetation from overstory trees to understory mosses, rates of productivity and nutrient cycling were determined. Productivity of this forest at low elevations has returned to pre-adelgid levels, while at high elevations productivity is approaching these levels. In the absence of an intact overstory, forest understory vegetation can compensate by disproportionately cycling and retaining nutrients such as nitrogen that would otherwise leach offsite. The understory of this forest provides an important service in nutrient cycling. Our ability to actively manage forests in order to manipulate levels and rates of carbon sequestration was assessed using stand data and the Forest Vegetation Simulator Growth and Yield Model. Silvicultural intervention proved effective at sequestering additional carbon over a no action alternative by the end of our simulation period. This forest provides a variety of ecosystem services and has retained its ability to recover their function after catastrophic disturbance.

Thesis (M.S.)--West Virginia University, 2010.
Title from document title page. Document formatted into pages; contains vii, 45 p. : col. ill., col. maps. Includes abstract. Includes bibliographical references (p. 42-45).

The forests of south-eastern Australia, having evolved in one of the most fire-prone environments in the world, are characterized by many adaptations to recovery following burning. Thus forest ecosystems are characterized by rapid regenerative capacity, from either seed or re-sprouting, and mechanisms to recover nutrients volatilized, including an abundance of N2 fixing plants in natural assemblages. Soil physical, chemical and biological properties are directly altered during fire due to heating and oxidation of soil organic matter, and after fire due to changes in heat, light and moisture inputs. In natural ecosystems, carbon (C) and nitrogen (N) lost from soil due to fires are recovered through photosynthesis and biological N2 fixation (BNF) by regenerating vegetation and soil microbes.
This study investigated post-fire recovery of soil C and N in four structurally different sub-alpine plant communities (grassland, heathland, Snowgum and Alpine ash) of south-eastern Australia which were extensively burnt by landscape-scale fires in 2003. The amount and isotopic concentration of C and N in soils to a depth of 20 cm from Alpine ash forest were assessed five years after fire in 2008 and results were integrated with measurements taken immediately prior to burning (2002) and annually afterwards.
Because the historical data set, comprised of three soil samplings over the years 2002 to 2005, consisted of soil total C and N values which were determined as an adjunct to 13C and 15N isotopic studies, it was necessary to establish the accuracy of these IRMS-derived measurements prior to further analysis of the dataset. Two well-established and robust methods for determining soil C (total C by LECO and oxidizable C by the Walkley-Black method) were compared with the IRMS total C measurement in a one-off sampling to establish equivalence prior to assembling a time-course change in soil C from immediately pre-fire to five years post-fire. The LECO and IRMS dry combustion measurements were essentially the same (r2 >0.99), while soil oxidizable C recovery by the Walkley-Black method (wet digestion) was 68% compared to the LECO/IRMS measurements of total C. Thus the total C measurement derived from the much smaller sample size (approximately 15 mg) combusted during IRMS are equivalent to LECO measurement which require about 150 mg of sample.
Both total C and N in the soil of Alpine ash forests were significantly higher than soils from Snowgum, heathland and grassland communities. The ratio of soil NH4+ to NO3- concentration was greater for Alpine ash forest and Snow gum woodland but both N-fractions were similar for heathland and grassland soils. The abundance of soil 15N and 13C was significantly depleted in Alpine ash but both isotopes were enriched in the heathland compared to the other ecosystems. Abundance of both 15N and 13C increased with soil depth.
The natural abundance of 15N and 13C in the foliage of a subset of non-N2 fixing and N2 fixing plants was measured as a guide to estimate BNF inputs. Foliage N concentration was significantly greater in N2 fixers than non-N2 fixers while C content and 13C abundance were similar in both functional groups. Abundance of 15N was depleted in the N2 fixing species but was not significantly different from the non-N2 fixers to confidently calculate BNF inputs based on the 15N abundance in the leaves.
The total C pool in soil (to 20 cm depth) had not yet returned to the pre-fire levels in 2008 and it was estimated that such levels of C would be reached in another 6-7 years (about 12 years after the fire). The C and N of soil organic matter were significantly enriched in 15N and 13C isotopes after fire and had not returned to the pre-fire levels five years after the fire. It is concluded that the soil organic N pool can recover faster than the total C pool after the fire in the Alpine ash forests.

Deadwood has increased over the last 25 years, but it remains unclear to what extent this is driven by forestry practices or storms. Therefore, I wanted to study the change in volume, decay stage and tree species during a 22-year period, to see if there was a correlation between increase of deadwood and storm. This study included data from southern Sweden, collected by the Swedish National Forest Inventory between 1994-2016. Deadwood in production forest have doubled over the last 25 years and almost quadrupled in protected forest. The increase does not depend on storm since much of the fallen wood was probably removed following year. In protected forest there was an increase in deadwood of broadleaved trees and a drastic decrease in Pinus sylvetstris. While in production forest, conifer trees dominate and there was no lasting effect due to the storm Gudrun (2005) on Picea abies. Hard deadwood decreased in production forest, possibly due to increased removal of branches and treetops, used as forest fuel in forest management. Possible reasons for the increase in deadwood could be the awareness in forestry, especially certification system and voluntarily set asides. Though, there is still necessary to increase the volume of deadwood in production forest, since it covers the largest parts of Swedish forests and does not seem to reach the national environment objective in 2030.

The establishment of seedling regeneration is a key process in and indicator of ecologically sustainable forest management. The availability of seed and the creation of a suitable seedbed are recognised as important factors limiting seedling recruitment. A silvicultural method commonly used across northern and eastern jarrah forest blocks is shelterwood cutting. The primary objective of treating jarrah forest to shelterwood is to promote seedling regeneration in areas lacking sufficient advanced growth. Despite the widespread and progressive implementation of the shelterwood method, its application in jarrah forest has shown varying degrees of success. This thesis sought to investigate and better understand the roles of seed supply and seedbed condition in promoting successful seedling regeneration in shelterwood-treated jarrah forest. It addressed two questions from an ecological and management perspective. Firstly, could adequate seed supply and favourable seedbed conditions be effectively managed and produced in shelterwood-harvested coupes? Secondly, could adequate seed supply and suitable seedbed conditions be reliably produced to facilitate successful seedling regeneration following disturbance events, in this case post-harvest burning? A major effort was dedicated to developing a more accurate and practical method of assessing seed crops in individual trees. The final model produced a high degree of predictability (R² = 0.85), while still maintaining a high level of practicality for field application, with three easily measured variables being used (stem diameter combined with subjective assessments of capsule clump density and capsule clump distribution). The refined model dramatically improved estimates of crown capsule numbers from the previous model, with the R² value increasing from 0.29 to 0.85. The second major focus of the study was to assess the capacity of prescribed burns, under mild conditions, to produce seedbed conditions suitable for regeneration. Low intensity prescribed burns resulted in the production of suitable conditions for seedling regeneration; that is, leaf litter and understorey vegetation were reduced and ash beds were created. Ash bed production was heterogeneous within sites. This heterogeneity has been attributed to the capacity of low intensity prescribed burns to account for fine-scale variations in fuel quantity, continuity and condition. Patterns of pre-burn aerial seed crop size and seed fall following low intensity prescribed burning were also assessed. Canopy capsule crops showed a high degree of spatial and temporal variability, both in terms of seed quantity and maturation. Such variability has been attributed to individual trees or groups of trees responding differently to localised climatic events and/or interspecific site factors at each stage of the flowering cycle. The main source of this variability was shown to be the numbers and spatial distribution of super trees; that is, trees defined as having a stem diameter >60 cm and >20 000 capsules. The average rate of seed fall increased substantially following prescribed burning under mild conditions. Postharvest burning under the mild conditions of the current survey did not result in en masse seed fall. Rather, peaks in seed fall were observed in the first few weeks post-burn, followed by low level falls throughout the following year. Sites burnt in spring showed a higher and more consistent release of seed in the first few weeks following fire, whereas seed fall after autumn burning was more sporadic. The comparative and interactive roles that seed supply and seedbed conditions play in limiting recruitment of jarrah were also studied. Low seedling densities were recorded across all six burnt study sites. The fact that ample levels of post-burn seed fall produced such low seedling numbers suggested that adequate seed supply did not coincide with seedbed conditions suitable for mass seedling regeneration. Conditions favourable for seedling recruitment were highly variable within sites, since both seed supply and seedbed conditions were spatially heterogeneous. Fine-scale areas burnt to mineral soil showed an additive influence to the overwhelmingly dominant factor of seed supply on seedling recruitment. However, the capacity of low intensity burns to produce these seedbed conditions at a broad scale is limited. Results of this study suggest that successful stocking of shelterwood-treated jarrah forest is not always achievable following a disturbance event, such as post-harvest burning under mild conditions. The chances of a large seed supply coinciding with broad-scale seedbed conditions favourable for mass germination, emergence and establishment appear to be low. Successful stocking of shelterwood-treated jarrah forest is more likely to be a longer term outcome achieved through episodic recruitment, when favourable environmental conditions coincide with optimal seedbed conditions. Such episodic recruitment strategies may be common in resource-limited systems such as jarrah forest and other dry eucalypt forest systems, where conditions controlling the regeneration niche are often variable and unpredictable.

Vegetation along the River Murray floodplains has been shown to be in a severe state of decline. This decline is amplified by the impositions of river regulation. In South Australia, where vegetation losses have been great, regeneration is limited and may result in not only individual tree losses but also widespread population decline. This study aimed to examine the relationship between river flows and the regeneration process in populations of Eucalyptus camaldulensis and Eucalyptus largiflorens. The current structure of the populations was examined to determine if a viable number of varying age-classed trees were present. Tree surveys conducted at Banrock Station determined that while densities were low for both species, E. camaldulensis had a more sustainable population structure than E. largiflorens. Growth stages for both species illustrated highly clumped distribution, which is believed to correspond with river flooding magnitudes and frequencies. To address the potential link between tree distribution and flooding within the River Murray, a hydrological analysis was conducted for Banrock Station using river flows at the South Australian border from 1900 to 2003. The amount of time growth stages for each species were inundated was found to be greatly reduced under regulated flows compared to natural flows. This has resulted in shifted localized regeneration patterns corresponding with E. camaldulensis' greater demand for inundation than E. largiflorens. Moderate magnitude flows have been most impacted by regulation, and consequently these are the very flows needed for floodplain tree population maintenance. Flowering and seed fall for E. camaldulensis and E. largiflorens were monitored at Banrock Station for 22 months to identify losses in reproductive potential resulting from tree decline. While seed viability was not affected by vigour, trees with visually reduced vigour were found to produce less fruit and had reduced seed fall, as well as a reduced rate of fruit development. Dendrochronological techniques were applied to floodplain trees. Age and size relationships could be established, implying that such techniques can be applied in South Australia to high quality sites. Growth responses within cohorts were similar and easily matched between individuals illustrating cyclic, but not necessarily seasonal correlations. This work verified the preferential selection of younger trees for dendroecological studies, and identified a relationship between on moderate flows and measurable girth expansion in both floodplain tree species.
Thesis (Ph.D.)--School of Earth and Environmental Sciences, 2004.

Isohydric and anisohydric regulation of plant water status has been observed over several decades of field, glasshouse and laboratory studies, yet the functional significance and mechanism of both remain obscure. W e studied the seasonal trends in plant water status and hydraulic properties in a natural stand of Eucalyptus gomphocephala through cycles of varying environmental moisture (rainfall, groundwater depth, evaporative demand ) in order to test for isohydry and to provide physiological information for the mechanistic interpretation of seasonal trends in plant water status. Over a 16-month period of monitoring, spanning two summers, midday leaf water potential correlated with pre-dawn leaf water potential, which was correlated with water table depth below f:,>rnund level, which in tum was correlated with total monthly rainfall. Eucalyptus gomphocephala was therefore not isohydric. Despite strong stomatal downregulation of transpiration rate in response to increasing evaporative demand, this was insufficient to prevent midday leaf water potential from falling to levels below -2. 0 MPa in the driest month, well into the region likely to induce significant xylem air embolisms. However, even though midday leaf water potential varied by over 1 .2 MPa across seasons, the hydrodynamic plant water potential gradient (delta psi plant), inferred as the difference between pre-dawn and midday leaf water potential, was relatively constant across seasons, averaging about 0.6 MPa. This unusual pattern of hydraulic regulation, referred to here as isohydrodynamic, is predicted by a hydromechanical stomatal control model, but only when plant hydraulic conductance is dependent on transpiration rate. We observed a correlation between midday transpiration rate and whole-plant hydraulic conductance that was consistent with this requirement, although conditions did not allow dependence of one on the other to be established . The accuracy of the model is improved slightly with the addition of a root-shoot signal allowing guard cell osmotic pressure to decline in response to soil water potential. The implications of the observed pattern of hydraulic regulation are discussed in the context of mechanistic requirements in the stomatal control system, and its possible function in related physiological processes .

This study aims at explaining the distribution and composition of the southern Cape forests, the largest forest complex in southern Africa. These are the only forests in southern Africa which are actively and scientifically managed for their products and values. Population growth due to forestry, agricultural and economic development and a growing tourism industry exerts increasing pressures on the natural environment of the southern Cape coast and therefore affect the dynamics and conservation of the forests. Conservation and sustained utilization of the forests require a sound knowledge of the composition, structure and dynamics of the forests. This study was aimed at an understanding of the biogeography of the forests at the landscape level in order to isolate those variables which contributed to the present distribution and composition of the forests. Determinants of the forest location pattern in the southern Cape were identified as rainfall above 500 mm, which determines the potential limits of the forests, and the bergwind fire pattern, which determines the actual forest distribution. Fires driven by the hot, dry, northwesterly, föhnlike bergwinds interacted with the terrain physiography since prehistorical times and the forests persisted in topographic shadow areas. The largest forests in the area therefore occur on the coastal platform at the foot of the mountains, in the river valleys and on the coastal scarp. Forests in the mountains, with high rainfall, are small and scattered. The results have shown that the bergwind driven fires control the distribution of forests which have important implications for the understanding of forest dynamics and for conservation management of forests in multiple-use management systems. Forest composition at the landscape level was studied by means of plant species lists. A species list for the southern Cape forests was annotated with information on the growth form, breeding system, propagule type, forest type, moisture tolerance, abundance and spread in the study area, and the distribution range in southern Africa, of each species. Analyses of the list showed that the species/family ratios for the southern Cape forest flora are very low, that woody plants have mostly fleshy propagules and herbaceous plants mostly dry propagules, and that several species have adaptations to adverse conditions. The species richness and composition, and floristic similarity and relationships were compared between the southern Cape forest flora and the floras of 13 other forests representing particular geographic regions in southern Africa. Forest size explained relatively little of the variation in species richness of the forests. Stepwise multiple regression analyses indicated that the number of dispersal corridors, the proximity to other forests and mean altitude explained most of the variation in number of woody species, whereas the number of landscape types and dispersal corridors explained most of the variation in number of herbaceous species. The high similarity between the southern Cape forest flora and those of the forests along the escarpment from the eastern Cape to northern Transvaal, and the southern attenuation of species suggest that the forests were once continuous. It is suggested that the Sundays river valley east of Port Elizabeth isolated the southern Cape forests from those to the east already during the Pliocene or earlier.

[Truncated abstract] Recovery of soil nutrients, microbial populations and carbon (C) and nitrogen (N) cycling processes are critical to the success of rehabilitation following major ecosystem disturbance. Bauxite mining represents a major ecosystem disturbance to the jarrah (Eucalyptus marginata) forest in the south-west of Western Australia. Mining has created a mosaic of mined areas in various stages of succession surrounded by non-mined forest areas. Initial site preparations within rehabilitation areas such as contour ripping alter soil structure (creation of mound and furrows) and over time also influence the distribution of vegetation and litter. Current performance criteria developed by industry, government and other stakeholders have determined that before post-bauxite mined areas of jarrah forest can be integrated back into normal forest management practises they should be functional and demonstrate resilience to normal forest disturbances such as fire. Furthermore, resilience should be of a manner comparable to non-mined analogue forest sites. Currently little is known of the resilience of microbial communities and C and N cycling in rehabilitation sites to normal forest disturbances such as prescription burning. As such, before rehabilitated jarrah forests can be successfully integrated into broad scale forest management regimes, a more thorough knowledge of the potential impacts of burning practises on the soil microbial community and C and N cycling processes in these systems is required. ... While there are similar rates of C and N cycling the underlying microbial community structure was distinctly different; implying a high degree of functional redundancy with respect to C and N cycling. Differences in the C and N cycling and structure of the microbial communities were likely to be due to differences in soil environmental conditions (i.e. soil alkalinity/acidity, soil moisture) and C substrate availability which influence the physiological status of the microbial community and in turn are related to successional age of the forests. Results also suggest that the measurement of CLPP can be a useful approach for assessment of changes in the functional ability of microbial communities. However, the interpretation of how well these rehabilitation forests have recovered heterotrophic abilities was greatly affected by the methodological approach used (e.g. MicroRespTM or Degens and Harris, 1997). Importantly, results from Chapter 4 and 5 suggested that the effects of a moderate prescription fire on C and N processes, CLPP and microbial community structure of 18 year old rehabilitation forests are likely to be short-lived (< 2 years). Furthermore, the effects of the moderate spring prescription fire were not large enough to decouple C and N cycling processes over the short-term (< 1 years) which suggests that by 18 years of age rehabilitation forests demonstrate comparable functional resilience to a moderate prescription burn.

Thesis (Ph.D.)--Indiana University, School of Public and Environmental Affairs, 2007.
Source: Dissertation Abstracts International, Volume: 68-10, Section: B, page: 6564. Adviser: Vicky Meretsky. Title from dissertation home page (viewed May 20, 2008).

The quokka (Setonix brachyurus Quoy & Gaimard 1830) is a medium-sized, macropodid marsupial that is endemic to the mesic, south-western corner of Australia. While being a tourist icon on Rottnest Island, the species is threatened with extinction. It has been intensively studied on Rottnest Island in the 1960s and 1970s, however very little is known of its ecology on the mainland. Additionally the insular and mainland environments are extremely different suggesting that ecological differences between the two populations are likely. Consequently, this study sought to determine the basic autecology of the quokka and identify what factors have attributed to its threatened conservation status. The northern jarrah forest of Western Australia was selected as the study region due to it being at the northern limit of extant quokka distribution and because it was thought that the factors threatening the quokka would be exacerbated there. Fossil deposits suggest that the quokka originally occupied an area of approximately 49,000 km2 in the south-western corner of Australia. Historical literature show that they were widespread and abundant when Europeans colonised the region in 1829 but a noticeable and dramatic decline occurred a century later. The arrival of the red fox to the region coincided almost exactly with this decline and so it was probably ultimately responsible. Continued predation by both it and the feral cat are likely to have continued the decline, along with habitat destruction and modification through altered fire regimes. Specific surveys and literature searches show that since the 1950s, the area occupied by the quokka has declined by 45% and since 1990 by 29%. Based on the criteria of the IUCN (Hilton-Taylor 2000), the conservation status of the quokka should remain as vulnerable. An endangered status may be more applicable if the quokkas restriction to patches through its existence as a metapopulation is considered. Trapping of eight sites supporting quokka populations in the mid-1990s revealed three sites now locally extinct despite the ongoing, six year old, fox control programme. Another three are at serious risk of extinction. Extant population sizes ranged from one to 36 and population density ranged from 0.07 to 4.3 individuals per hectare. This is considered to be below the carrying capacity of each site. The overall quokka population size in the northern jarrah forest may be as low as 150 adult individuals, of which half are likely to be female. Even the largest extant populations are highly susceptible to stochastic extinction events. This small size was surprising considering the six year old, introduced predator control programme. Historically, the restriction to discrete habitat patches, the occasional inter-patch movement, the lack of correlation between the dynamics of each population and reports of frequent localised extinctions and colonisations suggest that the quokka population once existed as part of a classic metapopulation. The massive decline of the quokka in the 1930s pushed the metapopulation structure into a non-equilibrium state such that today, the extant populations are the terminal remnants of the original classic metapopulation. Wild mainland quokkas breed throughout the year. A significant reduction in the number of births occurs over summer and this coincides with a decline in female body weight. Despite this, the mainland quokka is relatively fecund and is able to wean two offspring per year. The level of recruitment from pouch young to independence was low and this may explain the apparent lack of population increase following the initiation of fox control. A total of 56 trapped quokkas were fitted with a radio collar. Mean home range size for quokkas was 6.39 ha with a core range of 1.21 ha and this was negatively related to population density. Male home ranges were larger than females but not significantly when the sexual size dimorphism was considered. Nocturnal ranges were larger than diurnal ranges reflecting nocturnal departures from the swamp refugia. Home range sizes varied seasonally, probably due to changes in the distance required to move to obtain sufficient nutrients and water over the dry summer compared to the wet winter and spring. Telemetry confirmed trapping results that showed no movement between swamps or populations. Home range centres shifted to the periphery of the swamp following the winter inundation and this may increase the species susceptibility to predation. The lack of dispersal is probably caused by quokka populations existing below carrying capacity and following selection for philopatry under the threat of predation for dispersing individuals. Without dispersal to recolonise or rescue unpopulated patches, the collapse of the original quokka metapopulation appears to have occurred. On a macrohabitat scale, the quokka in the northern jarrah forest is restricted to Agonis swamp shrubland habitats that form in the open, upper reaches of creek systems on the western side of the forest. This restriction was probably initially due to the high water requirements of the quokka but is likely to have been exacerbated by increased predation pressure since the arrival of the fox. On a microhabitat scale, the quokka is a habitat specialist, preferring early seral stage swamp habitats, probably for foraging, as part of a mosaic of old age swamp that provides refuge. Despite the six year old, introduced predator control programme, foxes and cats are still the major cause of mortality to quokkas. Road kills was the other identifiable cause. Individuals alive at the start of the study had an 81% chance of staying alive until the end. The likelihood of dying was minimised by grouping together with conspecifics, maximising home range size and maximising the time spent within the swampy refuge. Current rates of adult and juvenile survivorship should allow population recovery and so it seems pouch young mortality, reflected by low recruitment, has inhibited the anticipated population increase following predator control. The confounding effect of inadequate unbaited controls meant that little statistical evidence was available on the impact of introduced predators on the quokka, however the models provided support for earlier hypotheses of these. The presence of a quokka population at a site was related to the amount of poison baits delivered ??? reflecting predation pressure, the average age of the swamp and a mosaic of early and late seral stages within the swamp habitat. Recently burnt habitat is thought to provide food for quokkas and long unburnt habitat provides refuge from predation.

Thesis (Ph.D.)--Murdoch University, 2003.
Thesis submitted to the Division of Science and Engineering. "Supported by CRC for Sustainable Tourism and Dept of Conservation and Land Management (Western Australia)". Bibliography: leaves 334-355.

Despite the long time since the introduction and spread of pine plantations in southern hemisphere countries there has been no study of the suitability of this exotic and novel type of vegetation on the native avifauna. This thesis aims to add understanding of this habitat replacement and its effects on the forest bird community. This research included a series of studies to assess the quality of mature pine plantations for the forest avifauna in comparison to what is in native forests. The first two studies determine the effects on the forest bird community of the fragmentation and replacement of native forest in a gradient of substitution. The results showed a direct relationship between level of substitution and loss of functional diversity, and that fragmentation predicts the bird assemblage in pine stands. The next two studies used data from an intensive ringing season to assess differences in the condition of populations inhabiting each habitat. Birds, in general, were found in better condition in native fragments than in pine plantations. Moreover, a despotic distribution was determined for a migrant species and a gradient in habitat quality was found in relation to proximity to native forest. The next two studies used information from a nest-box survey set in a gradient of sites with substitution of native forest. The results showed that the type of forest cover and their proportion in the landscape may affect the breeding performance of some species. Finally, in the last study I evaluated the foraging niche of bird species in each habitat. Compared with native forest, niche breath reduced while the niche overlap increased in pine plantations for most species. The results suggest that pine plantations are poor quality habitat for the bird community and that the substitution of native forests increases selective pressure.

[Truncated abstract] Spatial structuring of genetic variation is commonly observed in plant species due to limited dispersal and local adaptation. Intraspecific genetic variation has significant implications for ecological restoration because the source of seed or plants influences patterns of gene flow, and may affect performance if there is adaptive divergence among source populations. This study assessed quantitative trait variation, local adaptation and molecular variation within three common, widespread, long-lived forest tree species from south-western Australia to understand the distribution of intraspecific genetic variation and predict the consequences of seed transfer for restoration. The geographic distribution of quantitative trait variation of jarrah Eucalyptus marginata was assessed through measurement of 15-year-old trees grown in a provenance trial. Survival of trees from the northern jarrah forest was significantly higher than that of trees from southern jarrah forest provenances, where mean annual rainfall is much higher, but stem diameter at breast height (d.b.h.) of southern jarrah forest trees was greater, implying faster growth. D.b.h. of trees from within the northern jarrah forest also exhibited a positive relationship with mean annual rainfall, with maximum d.b.h. observed in trees from provenances in the high rainfall zone. These patterns may reflect selection for faster growth under high rainfall conditions or environmentally-induced parental effects. The percentage of trees bearing buds and flowers varied among latitudinal divisions. ... Neither genetic variation within nor among populations of any species could explain variation of emergence and establishment in reciprocal transplant trials. Collectively, the findings of this study suggest structuring of genetic variation in these species at a broad, rather than a very local, scale. This is expected for widespread, long-lived species, where extensive gene flow and temporal variation are likely to favour high within, relative to among, population genetic variation. However, there is evidence that the source of seed may have a significant influence on the success of restoration of these species, whether as a result of genetic variation among populations or due to other factors affecting seed quality. These results highlight the importance of integrating studies of molecular and adaptive trait variation when seeking to understand the causes and consequences of genetic variation within plant species and contribute to the development of seed sourcing practices for improved restoration success.

Swamp rabbit and eastern cottontail populations have declined substantially in Illinois within the last half-century. Habitat loss and fragmentation, particularly of bottomland hardwood (BLH) forest, have left swamp rabbit populations patchily distributed along major rivers in the southern portion of the state. In addition, the decline of early-successional upland habitats due to changes in farming techniques have led to as much as 90% declines in cottontail populations in Illinois. Managers need information on basic vital rates and habitat use to conserve both species in southern Illinois; however, many questions regarding demography and behavior have not been investigated. My research examined the importance of several factors that may influence survival and habitat use among swamp rabbits and eastern cottontails. My specific research objectives were to 1) estimate seasonal and annual survival rates and identify primary mortality agents, 2) examine the influence of intrinsic factors and habitat variables on annual and seasonal 50% core area (CA) and 95% home range (HR) sizes, 3) assess differences in space use and habitat use by season, and 4) evaluate differences in space and habitat use between species for swamp rabbits and cottontails in BLH forests in southern Illinois. During December-March 2009-2013, I live-trapped and radiocollared adult swamp rabbits (>1.9 kg) and cottontails (>1.0 kg) at 7 BLH sites along the Cache River and Cypress Creek within the Cypress Creek National Wildlife Refuge in southern Illinois. I monitored rabbits for survival every 24-48 hr and estimated radiolocations by triangulation more than twice weekly during morning (0500-0900 hr), daytime (0900-1700 hr), and evening (1700-2400 hr) time periods on a rotating schedule. I delineated annual and seasonal 50% CA and 95% HR isopleths using kernel density estimators, comparing winter-spring (W/S; 21 Dec-19 Jun) and summer-fall (S/F; 20 Jun-21 Dec) seasons. During May-August 2012, I sampled microhabitat in 0.02-ha circular plots (3.5 plots/ha) randomly placed throughout home ranges of rabbits at each site. In ArcGIS, I classified macrohabitat patches into 1 of 4 cover types: agriculture, early-successional BLH (EBLH), mature BLH (MBLH), or upland. I also measured the distance from all radiolocations to the nearest patch of each cover type and the nearest river or creek. I modeled the influence of species, sex, and season on annual survival using parametric survival regression models. Then, I used the best model (based on AICc) to examine the influence of habitat covariates on survival. I also modeled the influence of habitat on annual and seasonal CA and HR sizes using generalized linear and generalized linear mixed effects models with AIC model selection. Finally, I estimated conspecific and heterospecific CA and HR overlap for swamp rabbits and cottontails, and examined differences between species in space and habitat use. I documented causes of mortality and estimated survival for 129 swamp rabbits and 75 cottontails during the period of study. Predation (71%) was the primary mortality agent for both species, followed by weather (9%) and hunter harvest (6%). Models with survival rates differing by species and season received the most support; swamp rabbits had higher estimated annual survival (0.37  0.05) than did cottontails (0.20  0.05), and survival for both species was lowest during the W/S season (βW/S=-2.28  0.46). None of the habitat covariates that I measured apparently influenced survival. Core areas and HRs were estimated for 60 swamp rabbits (SR; 34 M, 26 F) and 21 cottontails (CT; 10 M, 11 F) during the W/S season; of these, 57 swamp rabbits and 11 cottontails lived long enough to estimate S/F seasonal and annual home ranges. The average annual CA and HR for swamp rabbits were 2.49  1.42 ha and 11.60  5.81 ha, respectively. Cottontails had an average annual CA and HR size of 2.48  1.26 ha and 13.54  7.24 ha, respectively. Core areas and HRs for both species during the were larger during W/S than S/F (CA: βW/S=0.59  0.11, wi=1.0; HR: βW/S=0.53  0.11, wi=1.0). Seasonal CA sizes increased with decreasing proportions of woody ground cover within CAs (SR: βShrubs=-2.75  0.50, wi=1.0; CT: βShrubs=-2.30  0.74, wi=0.91). Few macrohabitat variables influenced space use for either species. The coefficient of variation in patch size within 1 km of study sites was positively associated with space use for both swamp rabbits (CA; β=0.01  0.004, wi=0.81; HR: β=0.01  0.003, wi=0.95) and cottontails (CA; β=0.02  0.01, wi=0.29; HR: β=0.02  0.01, wi=0.23); I did not detect significant differences between species in pairwise conspecific overlap within CAs or pairwise conspecific volume of intersection (VI) over the entire utilization distribution. Median conspecific CA overlap was higher during W/S than S/F, with mean CA overlap proportions of 0.20 ± 0.21 (range: 0−0.87) and 0.10 ± 0.18 (range: 0−0.73) respectively. Median conspecific VIs also differed between seasons, with mean pairwise VIs of 0.32 ± 0.19 (range: 0−0.77) during winter-spring and 0.19 ± 0.18 (range: 0−0.73) during S/F. Heterospecific CA overlap was 48% and 46% lower than conspecific overlap during W/S and S/F, respectively. Differences in habitat use between species were apparent. Swamp rabbits had HRs and CAs in areas with higher basal area compared to cottontails during both seasons (all U≥483, Z≥2.83, p≤0.005). Multivariate tests for both CAs and HRs indicated a significant effect of species on habitat use (CA: T2=0.58, F3, 71=13.70, p<0.001; HR: T2=0.24, F3, 71=5.80, p=0.001). During W/S, swamp rabbits had CAs and HRs composed of significantly higher proportions of EBLH (CA: F1, 73=16.46, p<0.001; HR: F1, 73=8.55, p=0.005) and MBLH (CA: F1, 73=17.99, p<0.001; HR: F1, 73=7.78, p<0.007). Swamp rabbits were located significantly closer to a permanent watercourse (F1, 79=24.18, p<0.001) than cottontails. Indeed, 95% of all swamp rabbit radiolocations were ≤332.0 m away from a permanent watercourse (mean=169.0  100.0 m; range=1.0−571.0 m; Figure 18), whereas 95% of cottontail radiolocations were ≤536.0 m away from a permanent watercourse (mean=289.0  142.0 m; range=1.7−670.0 m; Figure 18). Swamp rabbits also were significantly closer to MBLH patches (F1, 79=9.05, p=0.003) and farther from agriculture (F1, 79=12.36, p=0.001) than cottontails. My study represents the most complete record to date on survival and habitat use by swamp rabbits. Rabbit survival was positively associated with basal area so management actions that provide woody cover for concealment and thermoregulation may benefit both species. Although cottontails in my study used early-successional BLH, patterns of space and habitat use described here demonstrate that cottontails remained on the periphery of bottomlands. My study confirms the utility of early-successional BLH to both species; however, stands that are located too far from a permanent water sources are unlikely to be used by swamp rabbits, and may be less suitable for other BLH specialists as well. Allowing grasslands and crop fields to succeed into old fields containing bushes, vines, and other woody species will benefit both cottontails and swamp rabbits. Within BLH forests, canopy gaps can be created to promote tree regeneration and woody ground vegetation such as vines and shrubs. Finally, upland early-successional habitats that border bottomland forests are especially important as refugia for swamp rabbits during flooding.

Anthropogenic habitat modification is a significant threat to the conservation or global biodiversity. The fragmentation and alteration of woodland habitat has resulted in the substantial decline of many woodland bird species in the agricultural regions of southern Australia. The Rufous Treecreeper Climacteris rufaa, a once common woodland resident, has declined in abundance in the wheatbelt of Western Australia and appears to be sensitive to habitat fragmentation. The reasons for this are unclear because our knowledge of the species and the threats posed by fragmentation arc limited. In this study, I compared the social organisation, habitat selection, reproductive success, dispersal and population dynamics of two Rufous Treecreeper populations living in the Western Australian wheatbelt. The first population occupied a large (8,500 ha), relatively undisturbed and unfragmented landscape. The second occurred in an equivalent sized area that had been substantially modified by agriculture. I hypothesised that habitat fragmentation and alteration would adversely affect the viability of the population living in the agricultural landscape. In the unfragmented landscape, treecreepers lived in cooperatively breeding, territorial groups. A group usually comprised a primary (assumed to be breeding) male and female, and philopatric offspring (helpers) from previous breeding seasons. Helpers assisted in the feeding and caring of nestlings and there was a positive relationship between group size and reproductive output. Breeding groups often fanned interactive neighbourhoods whereby resident individuals from one territory would feed nestlings in adjacent territories. A total of 77.7% of 148 nesting attempts produced at least one fledgling. Annual productivity per breeding group (n = 90 group years) was 2.1 ± 0.18 fledglings. Fledgling and juvenile survival rates (0.76 ± 0.04 and 0.46 ± 0.03 respectively) were comparatively high, as was the annual survival rate of primary males (0.77 ± 0.06) and females (0.75 ± 0.05). A multi-scaled analysis of habitat use in the unfragmented landscape identified preferential habitat selection by the species at three spatial scales. At the landscape scale, treecreepers used Wandoo Eucalyptus wandoo woodland at a significantly higher rate than predicted by the availability of this woodland type. Territory selection was positively correlated with the density of hollow bearing logs and nest sites, and tree age. These structural characteristics were also positively correlated with reproductive success und survival in treecreepers, indicating that habitat structure may be a useful measure of territory quality. Nest sites (hollows) were preferentially used if they had a spout angle of ≥ 50° and an entrance size or 5-10 cm, but nest-site selection was not related to nest success. The ecological traits of the treecreeper population living in the agricultural landscape differed from the population in the unfragmented area in a number of ways. Habitat fragmentation in the agricultural landscape disrupted territory contiguity with adverse consequences for social interaction. Nest success and annual productivity were significantly lower in the agricultural landscape, although they varied between different categories of habitat remnants. Reproductive success was lowest in grazed remnants supporting comparatively high population densities. Landscape differences in success did not appear to be a result of a disparity in nest predation levels, but may be related to variation in food availability and habitat quality. The spatial structure and dynamics of the subdivided population in the agricultural landscape were consistent with certain aspects of metapopulation theory. Treecreepers lived in spatially discrete local populations that were unlikely to persist without immigration owing to low reproductive and survival rates. However, movement between habitat remnants appeared to be sufficient to rescue these local populations from extinction. Although declining in numbers during the study, the subdivided population in the agricultural landscape appeared to be fluctuating around equilibrium owing to immigration from outside the study area. The consequences of habitat fragmentation for the Rufous Treecreeper are complex and interactive. A reduction in habitat area and an increase in remnant isolation disrupts the social organisation of the species and results in small localised populations that are susceptible to extinction. Modification of the remaining vegetation may reduce habitat quality leading to poor reproductive success. In addition to increasing habitat area and maintaining landscape connectivity, future management of fragmented landscapes must focus on improving the quality of remnant vegetation by removing degrading process and ensuring the recruitment of endemic plant species.

The macroinvertebrate fauna of Carey Brook, a 28 km tributary of the Donnelly River (and typical of the streams found in the southern forest region of Western Australia) was sampled at twelve sites between November 1988 and August 1989. The distribution of taxa among invertebrate families was similar to that of jarrah forest streams further north although more dipteran and fewer coleopteran taxa were collected in Carey Brook. Most environmental variables and flow descriptors followed longitudinal gradients, however, seasonality appeared to have the most influence on community structure. The abundance and distribution of most functional feeding groups supported the predictions of the River Continuum Concept (RCC). Categorisation of invertebrates into flow exposure groups and physical descriptors of water movement supported stream hydraulics theory and indicated that elements of both this theory and the RCC could be usefully combined to explain longitudinal changes in macroinvertebrate distributions. The immediate effects of forestry activities on community structure were examined in the headwaters of Carey Brook. The fauna at four sites on an upland stream which ran through a logging coup were compared with the fauna at four nearby undisturbed sites, before and after clearfelling in 1989 and 1990. Taxonomic richness and invertebrate abundance did not appear to be affected greatly by clearfelling, however, the composition of the macroinvertebrate fauna in the affected stream changed in comparison to the undisturbed sites after logging commenced but returned to pre-logging composition after winter and spring rains had ceased. The changes in the composition of the fauna in the disturbed stream were associated with increases in suspended solids. Changes in the macroinvertebrate communities eight years after logging were examined in two sets of paired catchments near Carey Brook. Both paired catchments contained an undisturbed stream and another where clearfelling had been taken to the stream edges. One of the paired catchments also contained a third stream where a 100 m wide riparian buffer zone had been retained during clearfelling. Differences in taxonomic richness and abundance of invertebrates between undisturbed and clearfelled streams were obscured by differences between sites within each stream. However, differences in community composition were observed in both catchments and these were associated with differences in conductivity, the amount of benthic organic material and total nitrogen. The 100 m wide buffer appeared to be effective in ameliorating long term disturbance due to clearfelling. The nature of the invertebrate community structure of the fauna in the streams of the southern forest region of Western Australia are discussed in relation to the longitudinal and seasonal distribution of taxa and the results of both immediate and long term effects of forestry activity on the macroinvertebrate fauna. The fauna appears to be individualistically arranged with both equilibrial and non-equilibrial attributes. Management implications of this study for future forestry activities are also discussed, particularly the importance of protecting the fauna and integrity of first order streams and others from forestry activities with riparian buffer strips.

Since the introduction of management practices by the Forest Service to stabilize red-cockaded woodpecker (RCW) populations, the number of cavity trees killed by southern pine beetles (SPB) has increased. A model of the landscape ecology of RCW and SPB in the Homochitto National Forest was created using data collected from the Forest Service and Global Atmospherics. The conclusions of the study were that the RCW and SPB utilize the same type of habitat and the stand hazard maps are an accurate means of determining the locations of SPB infestations. The functional heterogeneity maps created for the SPB and RCW would be useful predictors of future occurrences of either species if complete data were obtained.

Processes structuring bee communities in agricultural landscapes are well-documented compared to those in other anthropogenic landscapes, like production forests. Forests across the temperate zone have historically been under-sampled, in part due to the perception that they provide little habitat to support diverse bee communities. While research suggests that early successional habitats support high levels of bee species richness and abundance, little empirical evidence exists to support the notion that forests, in turn, do not. To understand the relationship between forest successional age and major elements of the bee community, I sampled bees in a southern production pine forest in Hancock County, MS across 2012 and 2013. I found that while bee abundance declines with successional age, species richness does not. Combining this work with other recent research, I propose a generalized framework for understanding the role of disturbance and forest structure in structuring bee communities of southern forests.

To achieve a balance between sustainable development and conservation of threatened species, management depends on understanding the predicted response and interaction of that species with their environment in order to develop appropriate mitigating solutions. The Carnaby’s cockatoo Calyptorhynchus latirostris is declining across much of its range due to the detrimental effect of habitat degradation and loss. Since the decline of food resource availability in non-breeding areas is believed to be contributing to the reduction in the number of Carnaby’s cockatoos knowledge of the birds’ foraging ecology and the influence of external factors on food resource availability is essential for effective management. Despite extensive studies and conservation work on the Carnaby’s cockatoos, there remain many gaps in our understanding of the birds’ foraging behaviour. The aim of this thesis is to fill some of those gaps. Carnaby’s cockatoos are destructive feeders, removing plant parts with strong beaks by holding them while extracting seed and insect larvae. Surveys of the birds feeding preferences were analysed by recording feeding residues of the number of eaten and uneaten infructescences left behind on the ground following foraging bouts. It was noted that Carnaby’s cockatoo diets were highly variable in terms of plant structures and species manipulated and consumed. Twenty-four species of food plants were manipulated by Carnaby’s cockatoo. Of these, 15 species of plant were consumed for seeds, with 53% of the total being made up of proteaceous species. Six of the 15 species (all Banksia species) were also manipulated as inflorescences. Grubbing for insects that were living in or on the woody stem tissue was observed in 63% of the food resource plant species collected. Carnaby’s cockatoo displayed a strong preference for food resources of the Banksia and Hakea genera. The relationship between Carnaby’s cockatoos and Banksia species was further examined to understand infructescence availability and variability in seasonal and total annual counts to determine the amount of potential food available to Carnaby’s cockatoos. Banksia attenuata, B. grandis, B. ilicifolia, B. menziesii, B. prionotes and B. sessilis were targeted in this study. Infructescence availability was determined through examination of Carnaby’s cockatoo feeding residues and numbers of mature infructescences that make up the standing crop of infructescences containing seeds. Banksia infructescences were available throughout the study for five out of the six species, although seasonal and annual amounts available varied. The numbers of infructescences available were not significantly (P > 0.05) influenced by soil type. However, infructescence numbers were significantly (P < 0.05) reduced by the presence of Phytophthora cinnamomi. In general the number of infructescences significantly (P < 0.05) increased as post-fire age increased. Plant allometric relationships between morphological characteristics and number of infructescences were investigated to help identify factors which best predict infructescence numbers. For B. attenuata, canopy volume, canopy area and girth emerged as the best individual predictive models for explaining the variability of the number of infructescences. Multiple linear regression of all B. attenuata plant morphological variables accounted for 29% of the variability in the number of infructescences. Canopy volume, canopy area, girth and foliage height were the best individual predictive models for determining the number of infructescences for B. menziesii. The combination of all B menziesii plant morphological characteristics explained 44% of the variability in the number of infructescences. All the models tested for B. sessilis revealed significant (P < 0.05) relationships with correlation coefficients > 53%. Canopy area was the best individual predictive factor for B. sessilis, accounting for around 90% of the variation. Multiple linear regression analysis combining all B. sessilis plant morphological variables revealed a correlation coefficient of 92%. In comparison to B. attenuata and B. menziesii (resprouters), B. sessilis is an obligate reseeder which is killed by fire. As a consequence of reseeding post-fire, B. Sessilis commonly occurs in dense thickets and are often more uniform in plant size, age and infructescence availability than resprouters and therefore displays stronger allometric relationships. Determining the influence of external factors on infructescence numbers helps in establishing the amount of food resources available for Carnaby’s cockatoos and in turn highlights the importance of various food resource habitats. Banksia species investigated as part of the food resource availability study were further examined to determine temporal variability of infructescence use by Carnaby’s cockatoo. Carnaby’s cockatoos showed themselves to be tolerant of changing resource availability which allowed them to effectively utilise food resources across the landscape throughout all seasons. Approximately 50% of resources available were utilised by Carnaby’s cockatoo throughout the year, with around 80% of handled infructescences consumed. Carnaby’s cockatoos showed flexibility in diet, with temporal variability in food resource use throughout the year. Infructescence resource use was highest between April and September. Level of consumption was a direct result of infructescence availability with no significant differences recorded in infructescence use in the presence of P. cinnamomi and different post-fire age stands. Seed energetics and proportion of seeds and follicles available and consumed were investigated to determine the number of infructescences required to meet daily metabolic requirements of Carnaby’s cockatoo. Over 65% of infructescences handled were consumed for seed for each Banksia species. B. sessilis recorded the largest number of infructescences and follicles manipulated by Carnaby’s cockatoos. The energy content of Banksia seeds ranged from 20-23 kJ g-1. Seed weight varied from 0.075g ± SE 0.016 for B. attenuata to 0.007g ± SE 0.002 for B. sessilis. The number of infructescences required to meet the birds’ daily energy intake ranged from 14 for B. grandis to 3821 for B. sessilis, based on mean number of follicles manipulated for seed and one-hundred percent seed availability. Incorporation of the potential number of seeds per follicle increased the number of infructescences required: B. attenuata, B. ilicifolia, B. menziesii and B. sessilis increased by almost 200%, while B. prionotes and B. grandis increased by 200% and 300%, respectively. Information collected on plant morphology, structure and infructescence availability combined with infructescence consumption and seed energy reward by Carnaby’s cockatoos allowed the development of food resource algorithms to guide habitat quality assessment. Establishment of quantitative criteria for assessing habitat quality for Carnaby’s cockatoo, such as methods for determining food resource availability, allows for effective integration of biodiversity issues into planning and impact assessment processes. The research undertaken for this thesis will add to the understanding and conservation of Carnaby’s cockatoo, an iconic South Western Australian species.

[Truncated abstract] Mediterranean southwest Australia, a global biodiversity hotspot, has nutrient deficient soils, exacting climatic conditions and is species rich with 7380 native vascular plant species, of which 49% are endemic. The region is expected to experience one of the world's highest degrees of biodiversity loss and change in the coming decades, with introduced species presenting a major threat. Limited knowledge is available on the mechanisms of ecosystem change associated with invasion and fire in this biodiversity hotspot region. Banksia woodland, an iconic complex species-rich natural ecosystem is one of the major vegetation types of the coastal sandplain, extending from 15 to 90 km inland and 400 kms along the west coast. The following hypothesis was tested to explore the ecological impacts of invasion: Is invasion of Banksia woodland by the introduced species Ehrharta calycina and Pelargonium capitatum accompanied by an alteration in ecosystem properties and processes, whereby the degree of change is related to fire frequency and abundance of introduced species? Different vegetation conditions, i.e. Good Condition (GC), Medium Condition (MC), Poor Condition invaded by Ehrharta calycina (PCe) and Poor Condition invaded by Pelargonium capitatum (PCp) were utilized for field assessments. ... In the soil seed bank, species numbers and germinant density decreased significantly for native and seeder (fire sensitive) species between GC sites and invaded sites. Surprisingly 52% of germinants at GC sites were from introduced species, with much of the introduced soil seed bank being persistent. Native species were dominated by perennial shrubs, herbs and sedges, while introduced species were dominated by perennial and annual grasses and herbs. Invasion by introduced species, associated with frequency of fire, altered the ecosystem, thus disadvantaging native species and improving conditions for even greater invasion within the Banksia woodland. Significantly higher soil phosphorus P (total) and P (HCO3) were found at PCe and PCp sites compared to GC sites. Leaf nutrient concentrations of phosphorus were significantly higher, and potassium and copper significantly lower in PCe and PCp sites, with introduced species having significantly greater concentrations than native species (except Manganese). This study demonstrated the key role of phosphorus in the Banksia woodland, in contrast to other research which identified nitrogen as the major nutrient affected by invasion. Higher levels of soil and leaf phosphorus, loss of species diversity and function, changes in fire ecology and canopy cover and a limited native soil seed bank make restoration of a structural and functional Banksia woodland from the soil seed bank alone unlikely. Without management intervention, continuing future fire is likely to result in a transition of vegetation states from GC to MC and MC to PC. The knowledge gained from this study provides a better ecological understanding of the invasive process. This enhanced understanding will enable the development of adaptive management strategies to improve conservation practices within a biodiversity hotspot and reduce the impact of the key threatening process of invasion.

High-severity disturbances are the primary drivers of Engelmann spruce-subalpine fir ecosystems in the southern Rocky Mountain. Recently, an unprecedented, landscape-wide (at least 250 km2) spruce beetle outbreak killed virtually all the Engelmann spruce on the Markagunt Plateau in southwestern Utah, USA. Results from dendroecological analyses suggested the combination of antecedent disturbance history and drought-driven stand development was responsible for creating suitable host conditions prior to the recent outbreak. Multiple and consistent lines of evidence suggested mixed- and high-severity fires shaped the development of the Markagunt Plateau. Subsequent stand development, influenced by species-specific differential tree-ring response to drought, resulted in the gradual increase of Engelmann spruce dominance across the landscape. Spatiotemporal outbreak dynamics included the early, independent and spatially synchronous building of beetle populations in moist sites with large Engelmann spruce across the landscape. As the outbreak evolved over time, it is likely temperature anomalies accelerated beetle population growth, leading to more rapid spruce mortality. In the wake of the spruce beetle outbreak, results from simulated potential fire behavior suggested there was a reduction in probability of active crown fire for one or two decades on near-pure Engelmann spruce sites after the outbreak. This counterintuitive result suggested extreme fire behavior is not an inevitable consequence of spruce beetle outbreaks. Regardless of the occurrence of fire, forest response is likely to be dominated by advance regeneration in the seedling bank. Furthermore, because spruce was virtually absent from the understory, forest reorganization is likely to be dominated by subalpine fir. In response to recent outbreaks such as the Markagunt Plateau, silviculturists are questioning what they can do to limit the loss from these likely inevitable spruce beetle outbreaks. Concepts of resistance and resilience can be used in planning vegetation management intended to indirectly control beetle populations by manipulating their habitat (vegetation). Resilient landscapes will ideally have spruce age class diversity and size class diversity in spatially discontinuous patches.

Bushfire is, in terms of human lives lost, property destroyed, and damage to natural systems, by far the most urgent environmental problem in Australia. This thesis tries to answer a number of questions about bushfire behaviour, history, effects, and management, in the Wungong Catchment of Western Australia. It does so by an overtly cross-disciplinary approach, involving a mixture of the three main streams of human knowledge, namely the humanities, natural science, and social science.First, I offer a literature review of several hundred books and papers drawn from the three main streams of knowledge mentioned above. The review includes some discussion of ‘bushfire epistemology’, a currently vague and neglected matter.The concept of ‘place’ is important to humans, so I then give a straightforward geographical description of Wungong Catchment, with some mention of the history of bushfire. To describe the vegetation, I use inductive statistics, and a method developed by me from the ideas of Delaunay (1929) and Dirichlet (1850). Given that there are hundreds of plant species within the catchment, I use a landscape approach, and only sketch the main tree species, and two iconic plants, the balga and the djiridji, both of which are important to the original custodians of the catchment, the Nyoongar people. There is discussion of other people’s research into the effect of bushfire on seed banks, and the flowering intervals of some plants of the jarrah forest.To see if Western Australia is anomalous, or fits into the worldwide pattern of humans using fire as a landscape management tool, I then examine some records of bushfire in other lands, including Africa, Madagascar, India, and Europe. The thesis then looks at the history of fire in the jarrah forest of Western Australia, based on observations by early European explorers and settlers from 1826 onward, the views of various foresters, and some opinions of current Nyoongar Elders.Using a mixture of natural science, applied mathematics, and archaeology, I give the results of cleaning the stems of those ancient plants called grasstrees, or balga (Xanthorrhoea spp.). These carry the marks of former bushfires, stretching back to 1750. They confirm historical reports of frequent fire in the jarrah forest, at 2-4 year intervals, and a recent decline in fire frequency. This contradicts the view, held by some, that European arrival increased the frequency of fire.As support for the balga findings, I present a simple mathematical model of self-organization in bushfire mosaics. It shows how lengthy bushfire exclusion can lead to disastrous situations, in which large areas of landscape become flammable and unstable. It shows how frequent, patchy burning can maintain a stable bushfire mosaic, with mild, beneficial fires. In the next chapter, I offer mathematical suggestions on how current unstable mosaics can be restabilized, by careful reintroduction of such burning.In dry, south-western Australia, water supply is an important topic, and a better understanding of the hydrological effects of bushfire may help with both bushfire and water management. I draw upon the natural science of forest hydrology, and the effects of fire in catchments. The evidence comes not only from Australia, but also from the United States, and South Africa.Turning to social science, I introduce Professor Peter Checkland’s ‘Soft Systems Methodology’, and suggest how it could be applied in resolving complicated conflict about bushfire management. I finish in legal style, with a summing up, and a verdict on the use of bushfire as a land management tool in Wungong Catchment, and possibly in other flammable landscapes.

Assemblages of algae are altered by both bottom - up ( e.g. nutrient availability ) and top - down ( e.g. herbivory ) processes. As a result of the increasing human population in coastal areas, massive changes are forecast to benthic habitats in response to increasing coastal nutrient concentrations and a reduction in consumers. To identify the scales over which nutrients may have an effect, abundance of turf - forming algae growing as epiphytes on kelp ( Ecklonia radiata ) were related to water nutrient concentration across temperate Australia. In general, the percentage cover of epiphytes was greatest at sites with the greatest nutrient concentrations. By experimentally elevating mean nitrate concentration from the low 0.064 ± 0.01 µmol L [superscript - 1 ] to 0.121 ± 0.04 µmol L [superscript - 1 ], which was still only ~ 5 % of that measured on a more eutrophic coast, I was able to increase the percentage cover of epiphytes to match those seen on nutrient rich coasts, despite not matching the nutrient concentrations on those coasts. Hence, it appears that the effects of elevated nutrients will be disproportionately large on relatively oligotrophic coasts. Nutrient concentrations were also experimentally elevated to test whether the presence of an algal canopy or molluscan grazers were able to counter the effects of nutrient enrichment on algal assemblages. The loss of canopy - forming algae is likely to be a key precursor to nutrient driven changes of benthic habitats, because nutrients had no direct effect on algal assemblages in the presence of canopy - forming algae. In the absence of canopy - forming algae, space was quickly monopolised by turf - forming algae, but in the presence of elevated nutrients grazers were able to reduce the monopoly of turf - forming algae in favour of foliose algae. This switch in relative abundance of habitat may reflect greater consumption of nutrient rich turf - forming algae by grazers, possibly creating more space for other algae to colonise. Importantly, greater consumption of turf - forming algae in the presence of elevated nutrients may act as a mechanism to absorb the disproportionate effect of nutrients on oligotrophic coasts. In southern Australia, canopy - forming algae have a negative impact on the abundance of turf - forming algae. To assess the mechanisms by which an algal canopy may suppress turf - forming algae, abrasion by the canopy and water flow were experimentally reduced. Abrasion by the canopy reduced the percentage cover and biomass of turf - forming algae. In contrast to predictions, biomass and percentage cover of turf - forming algae were also reduced when water flow was reduced. Light intensity was substantially reduced when there was less water flow ( because of reduced movement in algal canopy ). However, the reduction in available light ( shading ) did not account for all of the observed reduction in biomass and percentage cover of turf - forming algae, suggesting that other factors are modified by water flow and may contribute to the loss of turf - forming algae. Habitat loss and fragmentation are well known to affect the diversity and abundance of fauna in habitat patches. I used experimental habitats to assess how fragmentation of turf habitats affects the diversity and abundance of two taxa of macroinvertebrates with different dispersal abilities. I established that increased isolation of habitats reduced the species richness and abundance of invertebrates with slow rates of dispersal, while the species richness and abundance of invertebrates with fast rates of dispersal were greatest in habitats that were far apart. In summary, this thesis provides an insight into some of the impacts associated with human populations in coastal areas, namely increased nutrient inputs, loss of grazers ( e.g. harvesting ), and loss of canopy algae and fragmentation of habitats. I show that increased nutrient concentrations in coastal waters can alter the relative abundance of algal species, and that some effects of elevated nutrients can be absorbed by the presence of grazers. I also show that elevated nutrients have no effect on algal assemblage in the presence of canopy - forming algae, and that canopies can suppress the colonisation of turf - forming algae. Finally, I show that the fragmentation of turf habitats affects taxa of invertebrates with different dispersal abilities in different ways. Whilst the contemporary ecology of much of the temperate Australian subtidal coast is considered to be relatively unaffected by human activity, this thesis shows that changes to top - down and bottom - up processes could have large consequences for habitats and their inhabitants.
Thesis (Ph.D.)--School of Earth and Environmental Sciences, 2005.

Assemblages of algae are altered by both bottom - up ( e.g. nutrient availability ) and top - down ( e.g. herbivory ) processes. As a result of the increasing human population in coastal areas, massive changes are forecast to benthic habitats in response to increasing coastal nutrient concentrations and a reduction in consumers. To identify the scales over which nutrients may have an effect, abundance of turf - forming algae growing as epiphytes on kelp ( Ecklonia radiata ) were related to water nutrient concentration across temperate Australia. In general, the percentage cover of epiphytes was greatest at sites with the greatest nutrient concentrations. By experimentally elevating mean nitrate concentration from the low 0.064 ± 0.01 µmol L [superscript - 1 ] to 0.121 ± 0.04 µmol L [superscript - 1 ], which was still only ~ 5 % of that measured on a more eutrophic coast, I was able to increase the percentage cover of epiphytes to match those seen on nutrient rich coasts, despite not matching the nutrient concentrations on those coasts. Hence, it appears that the effects of elevated nutrients will be disproportionately large on relatively oligotrophic coasts. Nutrient concentrations were also experimentally elevated to test whether the presence of an algal canopy or molluscan grazers were able to counter the effects of nutrient enrichment on algal assemblages. The loss of canopy - forming algae is likely to be a key precursor to nutrient driven changes of benthic habitats, because nutrients had no direct effect on algal assemblages in the presence of canopy - forming algae. In the absence of canopy - forming algae, space was quickly monopolised by turf - forming algae, but in the presence of elevated nutrients grazers were able to reduce the monopoly of turf - forming algae in favour of foliose algae. This switch in relative abundance of habitat may reflect greater consumption of nutrient rich turf - forming algae by grazers, possibly creating more space for other algae to colonise. Importantly, greater consumption of turf - forming algae in the presence of elevated nutrients may act as a mechanism to absorb the disproportionate effect of nutrients on oligotrophic coasts. In southern Australia, canopy - forming algae have a negative impact on the abundance of turf - forming algae. To assess the mechanisms by which an algal canopy may suppress turf - forming algae, abrasion by the canopy and water flow were experimentally reduced. Abrasion by the canopy reduced the percentage cover and biomass of turf - forming algae. In contrast to predictions, biomass and percentage cover of turf - forming algae were also reduced when water flow was reduced. Light intensity was substantially reduced when there was less water flow ( because of reduced movement in algal canopy ). However, the reduction in available light ( shading ) did not account for all of the observed reduction in biomass and percentage cover of turf - forming algae, suggesting that other factors are modified by water flow and may contribute to the loss of turf - forming algae. Habitat loss and fragmentation are well known to affect the diversity and abundance of fauna in habitat patches. I used experimental habitats to assess how fragmentation of turf habitats affects the diversity and abundance of two taxa of macroinvertebrates with different dispersal abilities. I established that increased isolation of habitats reduced the species richness and abundance of invertebrates with slow rates of dispersal, while the species richness and abundance of invertebrates with fast rates of dispersal were greatest in habitats that were far apart. In summary, this thesis provides an insight into some of the impacts associated with human populations in coastal areas, namely increased nutrient inputs, loss of grazers ( e.g. harvesting ), and loss of canopy algae and fragmentation of habitats. I show that increased nutrient concentrations in coastal waters can alter the relative abundance of algal species, and that some effects of elevated nutrients can be absorbed by the presence of grazers. I also show that elevated nutrients have no effect on algal assemblage in the presence of canopy - forming algae, and that canopies can suppress the colonisation of turf - forming algae. Finally, I show that the fragmentation of turf habitats affects taxa of invertebrates with different dispersal abilities in different ways. Whilst the contemporary ecology of much of the temperate Australian subtidal coast is considered to be relatively unaffected by human activity, this thesis shows that changes to top - down and bottom - up processes could have large consequences for habitats and their inhabitants.
Thesis (Ph.D.)--School of Earth and Environmental Sciences, 2005.

Fire ecology encompasses the study of the factors, biotic and abiotic, that influence the occurrence of fire in an area, as well as the effects fire has on the flora and fauna native and non-native to the region (Whelan 1995). Fire has had a major influence on shaping biomes as we see them today. Fire has had an effect on vegetation much before the evolution of Homo on Earth (Keeley and Rundel 2005, Pausas and Keeley 2009, Midgley and Bond 2011). With the evolution and expansion of Homo across Earth, fire has been tamed, and then generated and used over time to yield landscapes that were suitable for their existence (Pyne 1991, Bowman et al. 2009, Archibald et al. 2012). Thus, fire, vegetation and humans were, and still are, inextricably linked in certain biomes on Earth. The best examples are observed in tropical savannas and grasslands, biomes that experience distinct seasonality in climate and are thus prone to frequent fires caused either by lightning or by humans (Keeley and Rundel 2005, Archibald et al. 2012). At the other end of the spectrum of tropical vegetation types are rainforests where the occurrence of fires is constrained by a perpetually moist environment (Meyn et al. 2007, van der Werf et al. 2008), in the absence of manipulation of the forest landscape by humans. Frequent fires have been documented to alter structure and cause a decline in forest diversity in rainforests (Cochrane and Schulze 1999, Cochrane 2003), whereas fire exclusion in mesic savannas leads to increases in biomass and transition to forest ecosystems (Bond et al. 2003, Bond et al. 2005 and references therein). A tropical biome that lies between these two extremes of vegetation types is the Seasonally Dry Tropical Forest (SDTF) where the occurrence of fire is common, but for which there are contrasting views on the effect of fire on this system (Saha and Howe 2003, Otterstrom et al. 2006 as examples). Current forest management policies in SDTF areas, especially in India, actively aim to exclude fire from these forests mostly because of the perception held by forest managers and the general public that fire has negative effects on forests. However, very few scientific studies have explored the ecology of fire in SDTFs. In order to formulate fire management policies, it is necessary to have a more comprehensive understanding of the ecology of fire in this tropical forest type. This thesis addresses two components of fire ecology as applied to SDTFs. The first is how fire is influenced by the environment, and the second, how fires influence the biotic community particular to SDTFs. The study was carried out in an SDTF in southern India where fire is a common occurrence -the forests of Mudumalai – a protected area that exhibits a range of SDTF vegetation types, from moist deciduous to dry thorn forest, corresponding to a rainfall gradient. Fire influenced by the environment: For this section, the influence of fuel load, fuel moisture and ambient weather on area burnt, fire occurrence and fire temperatures were studied in the SDTF vegetation types of Mudumalai. The extent of fire (area burnt) in an ecosystem differs according to the relative contribution of fuel load and fuel moisture available (Meyn et al. 2007). At a global scale, these factors vary along a spatial gradient of climatic conditions and are thus “varying constraints” (Krawchuk and Moritz 2011) on fire activity in natural ecosystems (Meyn et al. 2007, Krawchuk and Moritz 2011). Moist ecosystems such as tropical rainforests are at one end of the spectrum where fire activity is constrained by fuel moisture. At the other end are arid ecosystems, such as deserts, where fire activity is limited by the presence of fuels. The potential for the globally widespread seasonally dry tropical forests (SDTFs) to be placed as a single entity in this framework was examined by analyzing the interacting effects of fuel load and fuel moisture on the extent of fire in Mudumalai. Logistic regression was used to model proportion area burnt in a given year with factors that would influence fuel load and fuel moisture – these were proportion area burnt the previous year, wet season rainfall the previous year and early dry season rainfall. Modelling was conducted at two levels – the overall landscape and within four defined moisture regimes (between 700 and 1700 mm yr-1) – using a dataset of area burnt and seasonal rainfall from 1990 to 2010. The landscape scale model showed that the extent of fire in a given year within this SDTF is dependent on the combined interaction of seasonal rainfall and extent burnt the previous year. However, within individual moisture regimes the relative contribution of these factors to the annual extent burnt varied – early dry season rainfall (i.e. a moderator of fuel moisture) was the predominant factor in the wettest regime, while the previous year’s wet season rainfall (i.e. a proxy for fuel load) had a large influence on fire extent in the driest regime. Thus, the diverse structural vegetation types associated with SDTFs across a wide range of rainfall regimes would have to be examined at finer regional or local scales to understand the specific environmental drivers of fire. While the extent burnt in SDTFs is largely dependent on climatic influences, the probability of ignition has not been characterized for SDTFs. Anthropogenic fires are a regular occurrence during the dry season in SDTFs (Stott et al. 1990). We investigated if the occurrences of anthropogenic fire in Mudumalai were associated with any particular weather conditions during the dry season. Logistic regression between probability of a fire day and weather variables -seasonal rainfall, ambient relative humidity and temperature -was examined during the dry seasons of 20042010 in Mudumalai. Fire incidence data was obtained from the Fire Information for Resource Management System (FIRMS; NASA 2002) and weather data from two automatic weather stations within Mudumalai. The analysis showed that days with high probabilities of fire occurrence were associated with low levels of early dry season rainfall, low daily average relative humidity, and high daily average temperatures. These weather conditions are known to influence moisture levels of fine fuels (Viney 1991, Archibald et al. 2009). In Mudumalai as well as other SDTFs the primary fuels for fires are fine fuels such as litter and dried grass that accumulate on the forest floor during the dry season. Our results suggest that the occurrence of fire is moderated by environmental conditions that reduce or enhance the flammability of fine fuels in the dry tropics. A quantitative framework for assessing risk of a fire day has been proposed as an outcome of this analysis to assist forest managers in anticipating fire occurrences in this SDTF, and possibly for those across south Asia. Of the various components of a fire regime, fire intensity is an important aspect. High fire temperatures (one measure of fire intensity, Keeley 2009) and resulting soil temperatures would have an effect on soil properties as well as plant species demography and community structure (Moreno and Oechel 1991, Neary et al. 1999, Morrison 2002). Fires that occur frequently in a region could vary in their intensity and severity depending upon the amount of fuel available and ambient weather conditions (Stinson and Wright 1969, Stott 1986, Stronach and McNaughton 1989, Ansley et al. 1998, Wotton et al. 2012). However, this relationship has not been examined in a multiple regression framework for SDTFs. Fire temperature was recorded and its relationship with ambient weather and fuel load was studied in two SDTFs of southern India -Mudumalai and Biligiri Rangaswamy Temple (BRT) Wildlife Sanctuary in Karnataka. During “controlled burns” conducted by the forest department staff in these reserves in February and March 2010, temperature indicating lacquers on mica sheets were used to measure fire temperature at several points at ground level and one cm below the ground. Biomass was harvested close to the temperature measurement points to estimate fuel load and fuel moisture. Ambient weather conditions were recorded during the controlled burn when the flame passed over the indicators. Temperatures recorded at ground level ranged from <79oC to 760oC, with the most frequently recorded temperatures between 343-399 oC and 510566 oC. Temperatures measured one cm below the ground ranged from <79oC to 302oC, with a majority of the indicators recording temperatures in the <79oC category. Ground-level temperatures increased with increasing biomass. A linear regression of ground-level temperatures with fuel load and ambient weather conditions of relative humidity and temperature was found to explain most of the variation in the data. Ground-level fire temperatures increased with increasing fuel load, but were also found to be lower at higher relative humidities at a given temperature. In order to reduce the intensity of forest fires that occur accidentally during the dry season, we recommend that fuel loads be reduced in the forest by prescribed burning early in the dry season. This applies especially to areas where there is accumulation of biomass over years, such as that of the tall grass Themeda cymbaria found predominantly in dry deciduous forest types. If prescribed burning is incorporated in fire management policies for these forests, then the season of burning will be important to consider. It is known from ecosystems where prescribed burning is regularly applied that early dry season fires are less intense than late dry season fires (Williams et al. 1998). However, this has not been systematically investigated for SDTFs. Through a burning experiment carried out in private land with vegetation type similar to tropical dry thorn forest, we investigated differences in area burnt, ground-level fire temperatures and soil temperatures one cm below the ground in the early dry season in January, late dry season in April and and early wet season in June. We also examined differences in fuel load, fuel moisture, soil moisture and weather conditions of ambient relative humidity (RH), temperature and wind speed in these phases; these factors could be responsible for observed differences in fire and soil temperatures or area burnt. Although area burnt was not significantly different between the early and late phases of the dry season, fire and soil temperatures were significantly lower in the former. The late dry season was characterized by distinctly higher fuel loads, lower fuel moisture, lower relative humidity, higher ambient temperatures and higher wind speeds compared that measured in the early dry season. Differences in soil temperature between these months may be attributed to the increase in fuel load since there were no significant differences in soil moisture. Fire spread was limited in the experimental plots in the early wet season in June, probably due to significantly higher levels of fuel moisture in this month; the resultant fire and soil temperatures recorded were low. Forest management should, therefore, consider early dry season burns in the month of January for prescribed burns in the sanctuary, although this would have to be tested in other SDTF vegetation types with more variable fuel load, fuel moisture and weather conditions. Fire’s influence on the biotic community: Concerns regarding the regeneration capacity of woody species in SDTFs have been voiced with respect to increasing frequencies of fire (Saha and Howe 2006, Kodandapani et al. 2008). Fire is known to cause high mortality of individuals of small size (Swaine et al. 1990, Suresh et al. 2010). However, mortality has been examined for large size classes, and not for seedlings. It is essential to understand the dynamics of seedlings and their contribution to the regeneration potential of SDTFs. Woody species in SDTFs are known to have traits that help them recover from recurring disturbances, such as sprouting from underground root stocks (Vieira and Scariot 2006). Another trait may relate to growth rates of seedlings. Growth rates of seedlings (defined in this study as established individuals between 10 and 100cm height) after dry season (February-March) fires were compared between adjacent pairs of burnt and unburnt transects established at eight sites in Mudumalai across vegetation types of moist deciduous, dry deciduous and dry thorn forest. The growth of grasses, a possible competitor for resources, was also monitored at each site. Seedling and grass heights were monitored at 3-month intervals between August 2009 and August 2010. A second fire in March 2010 affected transects at two sites in Mudumalai. Seedling and grass heights were monitored for two enumerations till August 2010 subsequent to the second fire at these two sites. A total of 1032 individuals across 58 woody species were enumerated. High seedling survivorship (>95%) was observed in both burnt and unburnt areas. Although seedling heights were significantly different between burnt and unburnt areas at the start of the enumeration in August 2009, heights were comparable within a year and a half of the fire. Comparable seedling heights in such a short time span were because of distinctly higher growth rates of seedlings in burnt areas compared to unburnt areas after the fire event, particularly during the pre-monsoon season. Grass biomass (volume), on the other hand, was significantly different between burnt and unburnt areas at both the first and last enumerations. Grass growth (change in volume) did not differ between burnt and unburnt areas. Rapid growth by seedlings after a fire implies adaptation through the use of stored resources for growth, possibly aided by lower competition from grasses, in order to attain a certain size before the subsequent return of unfavourable factors such as a recurrent fire event. Conclusions: The results from the study point to climatically driven fire regimes in an SDTF in southern India, with daily influences of weather conditions during the dry season on fire occurrences. Fire intensities increase with increasing fuel loads in these forests, moderated by weather conditions such as RH and temperature. Since fires are an anthropogenic phenomenon in these forests, active management with the use of prescribed fires in the early phase of the dry season is a possible option to control late dry season fires that would be higher in intensity. The current woody tree species assemblage in this southern Indian SDTF is resilient to fires at the seedling stage, with established individuals exhibiting high survivorship and rapid growth after a fire. However, the effects of fires of varying intensities on the regenerative capacity of the seedlings are not known. The effect of fire on habitat utilisation by large herbivores, or the impact of fire on the faunal community in general has not been studied for vegetation types that comprise SDTFs. The effect of fire exclusion on the ecology of SDTFs will provide useful information that can feed into management policies for this ecosystem type. These are potential areas of research for the future. Fire, if managed wisely, can be an effective tool for the conservation of SDTFs across south and southeast Asia.

No - till systems have been widely adopted by farmers in Australia over the past decade to reduce soil erosion, improve soil physical and chemical properties, conserve soil moisture and save on fuel costs. These changes in tillage practices can have a major influence on the ecology and management of weeds. Studies were undertaken on the seed biology of six important Australian weed species to provide underpinning knowledge of their response to tillage. Field studies were also undertaken to investigate the effect of no - till on weed seedling emergence, seed bank persistence and herbicide behaviour. Seed germination of threehorn bedstraw and wild turnip, the latter only at sub - optimal temperatures, was inhibited by light. In contrast, seed germination of common sowthistle and Indian hedge mustard was stimulated by light. Seed germination of small - flowered mallow was not influenced by the light conditions. Seedling emergence of threehorn bedstraw, wild turnip, small - flowered mallow and annual ryegrass was low on the soil surface but increased with shallow burial, which suggests that farming practices that achieve shallow burial of seeds are likely to promote greater seedling emergence of these weed species. In contrast, seedling emergence of common sowthistle and Indian hedge mustard was greatest for the seeds present on the soil surface and emergence decreased with increased burial depth. In field experiments, low soil disturbance tillage systems left more seeds on the soil surface after crop sowing, whereas high soil disturbance systems buried most of the seeds. Seedling emergence of annual ryegrass, threehorn bedstraw and wild radish was greater under minimum tillage than no - till system. In contrast, seedling emergence of Indian hedge mustard, common sowthistle, silvergrass, small - flowered mallow and turnipweed was greater under the no - till system. Seedling emergence of wild oat and wild turnip was not influenced by the tillage system. Even though seedling emergence of annual ryegrass was much lower under no - till, the persistence of residual viable seeds of annual ryegrass from one season to the next was similar between the tillage systems. This was because of much greater seed decay under no - till ( 48 to 60 % ) than that recorded under minimum tillage ( 12 to 39 % ). All dinitroaniline herbicides ( trifluralin, pendimethalin and oryzalin ) were more effective in reducing the number of plants, spikes, dry matter and seed production of annual ryegrass when incorporated at sowing with tines than with the discs. At Minlaton in 2004 and 2005, bioavailable trifluralin was greater under tillage systems with greater levels of soil disturbance than under lower soil disturbance systems. In the absence of the herbicide, annual ryegrass was less competitive with wheat under the disc - sown systems. The response of grain yield to herbicides was greater under the tine - sown systems than the disc - sown systems. The performance of S - metolachlor on annual ryegrass control was investigated under no - till. The control of annual ryegrass was greater than 80 % when S - metolachlor was applied at sowing ( incorporated by sowing or post - sowing pre - emergence ). However, application of the herbicide at sowing resulted in phytotoxic effects on crop emergence and grain yield of wheat. Application of S - metolachlor at 20 or 23 days before sowing not only provided effective control ( 74 to 83 % ) of annual ryegrass, it was also safe on wheat. Application of this herbicide at 40 or 46 days before sowing was relatively ineffective in controlling annual ryegrass ( 33 to 49 % weed kill ) but safe on wheat. In conclusion, soil disturbance caused by tillage was found to have a major influence on the behaviour of the seed bank of different species including seedling emergence and decay rates of weed seeds. However, the response to tillage tended to be species - specific and was related to their seed biology. Tillage systems also had a major influence on the efficacy and bioavailability of trifluralin, which is prone to volatilisation losses. The findings of this research program are expected to contribute to the improvement in weed management under no - till systems.
Thesis (Ph.D.)--School of Agriculture, Food and Wine, 2006.

Includes copies of author's previously published works
Guano deposits in caves form a rich food resource supporting diverse arthropod communities. Guano piles consist of distinct micro - habitats, fresh, moist, highly basic guano and older, dry, slightly acidic guano. Micro - habitat variation is strongly controlled by seasonal guano deposition that, in turn, effects the structure of arthropod communities. The maternity chamber of Bat Cave, Naracoorte, South Australia, contains extensive guano deposits supporting 38 species from three classes and 12 orders. This community was studied to determine spatial and temporal variation of arthropod communities, and biogeographic relationships between different regions in Australia. Species richness forms a positive linear relationship with pH, in situ moisture content and guano deposition. Many species show strong associations with fresh guano and hence are strongly seasonal, although some species are present throughout the year. Arthropod community structure in winter was found to be more closely related to prior summer arthropod structure than to subsequent seasons. Starlight Cave near Warrnambool, western Victoria, the only other maternity site for Miniopterus schreibersii bassanii, contained 43 species from 39 families and 14 orders. Seven species are common to both caves. The community structure of Starlight Cave was found to be more homogeneous than Bat Cave with samples clustering by season rather than sample year as was the case at Bat Cave. Different cave morphology was found to significantly alter the micro - habitat conditions and, hence, community structure in Starlight Cave compared with Bat Cave. Migration of guano associated arthropods at local, regional and continental scales was assessed using mtDNA and allozyme electrophoresis the pseudoscorpion genus Protochelifer as a model organism. Phylogenetic tree reconstruction revealed a wide geographic distribution of cavernicolous species across southern Australia. Cave colonisation is believed to have occurred only once, followed by dispersal to the Nullarbor Plain and other caves in south - eastern Australia. Dispersal was possibly phoretic on cave bats or occurred prior to aridification of surface environments that currently restricts migration. The distribution of guano - associated arthropods from arid, semi - arid and monsoonal karst areas in Australia are compared with temperate south - eastern Australia. Different climatic areas show large biogeographical differences in community structure, although similar families ( Urodinychidae, Reduviidae, Anobiidae, Carabidae and Tineidae ) are present in many Australian guano communities. Several potential mechanisms of dispersal are discussed including phoresy, colonisation from soil, terrestrial migration and interstitial cavities. Endemism to specific caves cannot be definitely assigned to any species, although 13 species show restricted distribution.
Thesis (Ph.D.)--University of Adelaide, School of Earth and Environmental Sciences, 2006.