Добірка наукової літератури з теми "Semi arid woodland"

The predicted future loss of native Australian species of plants and animals, in part as a result of adverse land management strategies, has led to attempts to identify areas of high biotic richness (numbers of species). Bioindicators are measures of the physical environment, or of a subset of the plants or animals, that best predict biotic richness. Ideally, bioindicators should aim at predicting as large a component of the plant or animal fauna as is possible at minimum cost. For two contrasting vegetation types, we examined remnant area, vegetation structural diversity, species richness of plants, lizards and terrestrial arthropods, and the relative abundance of individual arthropod species, as indicators of faunal richness, using correlation, principal component regression and stepwise regression analyses. The study was carried out in gimlet Eucalyptus salubris woodlands (29 sites) and shrublands (27 sites) in semi-arid, agricultural Western Australia. Sites varied considerably in grazing history (woodland) and in farming history (shrubland). Fauna sampled were lizards (woodland), scorpions (woodland), isopods (woodland), cockroaches (woodland), termites (woodland, shrubland), earwigs (woodland), hemipterans (shrubland), beetles (woodland, shrubland), butterflies (shrubland) and ants (woodland, shrubland). None of the indicator variables in any analyses effectively predicted total faunal richness for either vegetation type (<35% of variation in total richness explained). In correlation analyses for woodlands, vegetation structural diversity and plant richness, but no fauna variable, explained a high percentage of the variation in the richness of lizards (56% explained by richness of native plants, +ve), scorpions (48%, richness of native plants, +ve), termites (55%, vegetation structural diversity, +ve) and beetles (59%, litter, –ve). The richness of the shrubland fauna was poorly predicted by all indicator variables (<25% explained). When using the total richness and abundance of ant functional groups, the abundance of a subset of species within ant functional groups, and of termite and beetle species, in principal component regressions, various ant functional groups explained 42% each of the richness of scorpions and beetles, and eight beetle species explained 50% of termite richness. When remnant area, vegetation structural diversity and the richness of native plants in woodland were tested in step-wise regressions as indicators of total faunal richness, remnant area was the only significant indicator variable, explaining 33% of total richness. The richness of native plants and vegetation structural diversity explained a total of 76% of the pooled richness of lizards + scorpions + termites. No significant indicator variable was found by regression procedures for total richness, or for a subset, of the shrubland fauna. We argue that differences in the predictive qualities of vegetation structure and plant richness between the vegetation types was due, in part, to differences in the spatial heterogeneity of biotic richness, and possibly the scale at which structure was measured. The use of structural diversity or plant richness as predictors of faunal richness for different woodland types, or those with different disturbance histories, or in different geographic or climatic regions, should not be adopted without verification of their efficiency at predicting the richness of the local fauna.

There are considerable uncertainties about the C cycle in semi-arid ecosystems. Hence, studies that have focused on Juniperus in Mediterranean woodlands are non-existent. This study provides a survey of the effect of the juniper woodland type (young and mature woodlands; joint effect of maturity and forest productivity) on stem respiration. We checked the seasonal variation of stem respiration, evaluating the effects of stem temperature on stem CO2 efflux. For this, we measured the stem CO2 efflux (µmol CO2 m−2 s−1) over the four seasons on 16 junipers using LI-6400 equipment. The results showed that in the more productive site (young woodland), the stem CO2 efflux was higher. This variable followed a clear seasonal trend, being higher during the spring and progressively decreasing in cold periods. In both juniper woodlands, and especially in the older forests, the Q10 coefficients were low (<2), typical of cold forests and slow-growing species. The exponential model also confirmed that the Q10 was significantly higher in young juniper trees. Thus, stem CO2 efflux was an indicator of the growth in this juniper woodland that is well adapted to a semi-arid climate.

The knowledge on diversity and distribution of spiders in Rajasthan is sparse as compared to other regions. There is a dire need of research regarding species composition, distribution pattern so that their role in controlling insect pests could be ascertained. Present study examined a novel approach for documenting the diversity of spider fauna in arid and semi- arid (Ajmer and Jodhpur) region of Rajasthan, India. A regular survey of spider faunal complex was conducted in four major habitats namely, woodland, wetland, pasture and caves/crevices/rocky area. Maximum number of spiders was found in woodland habitat and the minimum number of spiders were collected and identified from caves/crevices/rocky area with 31.86 and 17.61 relative abundance, respectively. Similarly, diversity indices viz., richness, evenness, Shannon-Weiner and Simpson indexalso indicated the maximum species richness in woodland and minimum in caves/crevices/rocky area. In woodland, Araneidae and Oxyopidae were found as most abundant families with 41.44 and 15.78 percent of total spider fauna while Lycosidae wasfound as the most abundant family in wetland but was at par with Araneidae in pasture habitats. In Caves/crevices/rocky area, family Pholcidae was found as the most abundant.

THE eastern grey kangaroo (Macropus giganteus) is one of Australia?s widest-ranging large macropodids, occurring in open forests, woodlands, subalpine woodland, farmland, and semi-arid regions throughout most of eastern Australia (Menkhorst and Knight 2001). However current general accounts (e.g., Poole 1995, Menkhorst and Knight 2001) regard M. giganteus as being absent from the northern Cape York Peninsula.

We studied soil disturbance by rabbits, echidnas, goannas, ants and termites at three different spatial scales across four vegetation communities (dense woodland, open woodland, shrubland, grassland) in semi-arid rangeland in western NSW. For analyses, bare and litter-covered surfaces (micro-scale) were nested within canopy and open patches (intermediate scale), which were nested within vegetation communities (landscape scale). Landscape-scale disturbances (rabbit warrens) were six and three times more abundant in open woodlands and shrublands, respectively, than in dense woodlands. Although individual warrens had a similar mass of excavated soil across all vegetation communities, in total, more soil was excavated in the grasslands than in the dense woodlands or shrublands. There were four times as many intermediate-sized disturbances (foraging pits and resting sites) under canopies than out in the open, and this was consistent across all vegetation communities. Echidna foraging pits and kangaroo resting sites dominated the canopy patches. Intermediate-sized disturbances scaled up to the landscape scale were marginally more abundant in the dense and open woodlands than in grasslands and shrublands. However, total mass of soil moved by all species did not differ among vegetation communities. The density of small-scale disturbances (ant nests, termite foraging galleries) did not differ at the landscape-, intermediate- or micro-scales. Our study documents the extent of animal activity in the semi-arid woodlands, and reinforces the notion that, as soil disturbance is scale-dependent, differences among species, habitats and communities will depend on the scale at which disturbances are examined.

There is widespread concern about population decline in a number of woodland-dependent birds in southern Australia. Of all declining species, approximately half forage on the ground. This study examined the avifaunal assemblages of temperate woodlands of the Northern Plains, Victoria, to investigate the importance of woodland habitats for ground-foraging species. Four main types of woodland were surveyed (white cypress-pine, black box, grey box and river red gum) and, in total, 89 bird species were detected. All four woodland types differed in habitat structure and, in turn, supported significantly different avifaunal assemblages. Forty of the 89 species (45%) foraged, at least in part, on the ground. Species richness and abundance of ground-foragers differed significantly between woodland types, being highest in white cypress-pine and black box. There was a greater richness of ground-foragers during the breeding than non-breeding season, but abundance did not vary seasonally. Overall, ground-foraging birds comprised a greater proportion of species (>55%) and individuals (>60%) in white cypress-pine and black box woodland than in grey box and river red gum (42–48% of species, <50% individuals). Those ground-foragers regarded as declining also occurred in greatest richness in white cypress-pine woodlands, one of the most depleted habitats in the region. The lowest richness of ‘declining’ ground-foraging species was in river red gum woodland, the most widespread woodland type. Throughout Australia, the proportion of ground-foraging species in bird assemblages tends to be greater in temperate, semi-arid or arid woodlands than in moist forests and rainforests. However, in many regions woodland habitats are severely depleted and their open ground layer is particularly vulnerable to degradation. The extent of suitable habitat for ground-foraging birds in temperate woodlands may be much less than is apparent from current measures of tree cover. Sustainable management of drier (non-riverine) temperate woodlands is required to conserve this important element of the Australian avifauna.

Abstract Soil moisture plays a key role in the ecological capability of arid and semi-arid woodland. Reducing soil moisture due to frequent droughts causes pest prevalence and disease outbreak and the consequence of forest dieback. On the other hand, soil moisture is strongly correlated with the amount of radiation received on the Earth’s surface. The sun’s radiation is traditionally described often by aspect and sometimes by toposhape. The use of the hillshade map for estimating solar radiation is possible through developing GIS. The present study aimed to compare the relationship and the ability of these indices to describe the phenomenon of arid and semi-arid woodland decline better and more accurately in a case study in the west of Iran. To this aim, the aspect and toposhape layers were generated in 5 and 12 classes, respectively. Then, the hillshade map in range of 0-255 was made during the peak of summer heat. The comparison of the dieback ratio in the three characteristic histograms showed that the shade index, unlike the other two indicators, had a significant effect on forest drought (R2=0.91 for linear equation and R2=0.94 for quadratic equation). The results indicated that the application of hillshade in describing and analysing ecological processes by relying on soil moisture such as woodland dieback is superior to the other two indicators. It is suggested that this index be used to obtain a risk model to predict woodlands dieback which are under the pressure of frequent droughts due to climate change or other mortal factors.

Twenty year old floristic data were reassessed to determine whether inclusion of remnant non-eucalypt semi-arid woodlands in national parks had enabled recovery from a degraded state, after decades of overgrazing. In Hattah- Kulkyne and Murray-Sunset National Parks (north-western Victoria), landscape condition had substantially improved by 2006. Formerly mobile dune systems in Hattah-Kulkyne are now stabilized by perennial field strata and increasingly dense shrubs (mostly Dodonaea viscosa subsp. angustissima). In Murray-Sunset, chenopod shrubs now dominate and there are signs of regeneration of some of the formerly dominant trees. Semi-arid woodland condition has not (yet) fully recovered, but there are encouraging signs of partial recovery, and indications that further improvements in landscape condition will occur, as long as overgrazing (particularly by rabbits) can be reduced further or maintained at low levels. There are indications that rabbit numbers have greatly increased post-Rabbit Haemorrhagic Disease, threatening the recovery to date.

The diet of sheep was recorded by direct observation in a shrub-dominated Eucalyptus populnea woodland between Nyngan and Bourke, N.S.W., on 7 occasions over a 2-year period. Different nutritional opportunities were provided by the effects of rainfall on 3 contrasting grazing treatments. The sheep did not graze equally over the whole area available but foraged selectively so that they encountered unacceptable plants rarely. In particular variable spear grass (Stipa variabilis) was avoided once the inflorescence had emerged and only extreme hunger pressured sheep into foraging in dead stands of this grass.matured, sheep ate firstly increasing quantities of perennial forbs and then mulga (Acacia aneura). When these foods were depleted, sheep subsisted on dead perennial grass, tree litter and broad leaf hopbush (Dodonaea vlscosa). All other shrub species were unacceptable. The ability of sheep to forage successfully during dry periods put excessive pressure on perennial grass, causing it to die out. I suggest this has contributed to the increased frequency of shrub establishment in the poplar box woodlands since they have been used for pastoral production.

Links between species and the effect they have on ecosystem function is becoming increasingly recognised. Examples of such links include the complex, often multi-staged process of animal mediated seed dispersal, seed-caching by mammals and the tripartite relationship that occurs between many fungus-eating (mycophageous) mammal species, mycorrhizal fungi and woody plants. In this thesis, the role a small omnivorous marsupial, Bettongia penicillata ogilbyi (woylie), plays in ecosystem function, using its interaction with Santalum spicatum (Western Australian sandalwood) as a model, was examined. The study was conducted in a semi-arid open wandoo (Eucalyptus wandoo) woodland, in Western Australia. Dryandra Woodland, (32°48'8, l16°54'E) 160 km southeast of Perth, is one of the largest and most diverse remnants supporting over 800 native plant species and 24 mammal species, seven of which are threatened. Dryandra Woodland experiences a Mediterranean climate with warm to hot, dry summers and mild, wet winters. Bettongia penicillata Grey 1837 is a small, nocturnal marsupial within the family Potoroidae. Since European settlement, the distribution and numbers of woylies have decreased dramatically. Factors attributed to this decline include habitat loss, the introduction of feral predators such as the cat (Felis catus), the European red fox (Vulpes vulpes) and competing herbivores. From its original distribution across the south-western third of the continent, only three remnant natural populations remain in the south-west of Western Australia at Perup Nature Reserve, Tutanning Nature Reserve and Dryandra Woodland representing a reduction in range of approximately 97%. Santalum spicatum (R. Br) DC (Western Australian sandalwood), family Santalaceae, is a small, hemiparasitic tree which has virtually disappeared from the 300-600 mm rainfall zone due to widespread clearing of natural woodland and excessive unregulated harvesting. Furthermore, it has been suggested that seed dispersal is limited in areas where woylies have become extinct. Four broad objectives were addressed in this thesis: 1. To determine the population and dietary requirements of woylies in Dryandra Woodland 2. To determine the impact woylies have on the regeneration of sandalwood, by measuring recruitment of sandalwood in an area where woylies are present compared with an area where they are absent 3. To examine, in detail, seed dispersal and seed caching behaviour in the woylie by radiolabelling seeds with scandium 46. This will include the types of seeds cached, how caches are located, whether secondary or tertiary caching occurs, seed preference, germination rate from caches and seedling predation 4. To develop a rationale for woylie conservation and reintroduction based on an understanding on the woylie's role in ecosystem function and species' coexistence. Two experimental sites, with both woylies and sandalwood, and a control site, with sandalwood but no woylies were used in this study. Site A is outside the main block of Dryandra Woodland, 1.65 km from the main entrance to the Woodland. This site lies parallel to the main Wandering-Narrogin road and across from farmland situated next to woodland. The sandalwood was planted in the 1950s and has numerous mature sandalwood trees, saplings and seedlings. Site B is within the woodland, 3.2 km from the Dryandra village. Site B was planted in the late 1970s to early 1980s and has very few new sandalwood recruits and the few seedlings that did occur were found on soil mounds along the fenced area parallel to and across from a dirt road. The control site, with sandalwood but no woylies was at the Wickepen Water Reserve, 40 km south-east of Dryandra Woodland. This site had many mature sandalwood trees but very little recruitment growing away from the parent crown. Trapping sessions, lasting four nights per experimental site, were commenced in May 2002 and repeated at regular intervals until December 2005 giving a total of 1300 trap nights at site A and 1400 at site B. The 2005 trapping sessions were carried out four times a year to cover the seasons for dietary analysis for Bettongia penicillata ogilbyi (woylie) and Trichosurus vulpecula (brushtail possum). Because the number of trapped and re-trapped woylies were so low, the Jolly-Seber method, used to estimate possum numbers, could not be used to estimate woylie populations at either site. Instead, the minimum number of animals known to be alive (KTBA) was calculated by counting the number of times an individual woylie was trapped over at least three sessions. Findings from this study indicate that woylie numbers are declining in Dryandra. Site A had a very low number of woylies KTBA with only two females trapped once in June 2002 and one individual male, trapped intermittently until February 2004. Subsequent trapping failed to catch woylies until December 2005. Because of the low number of woylie captures at this site no population data could be analysed. The number of woylies KTBA at site B was consistently higher than site A, although still low. A total of 11 individual females and 17 individual males were trapped between May 2002 and December 2005 giving a sex ratio of 1:1.5 females to males. The trapping effort in the spring of 2003 resulted in an estimated population of brushtail possums ranging from 17 at site A to 70 at site B thus giving a density of approximately 1.4 and 5.8 brush tail possums ha- 1, respectively. The trapping effort in spring 2005 resulted in an estimated population of brushtail possums of 25 at site A and 35 at site B, thus giving a density of 2.1 and 2.9 brushtail possums ha -1, respectively. The trap success per 100 trap nights for brushtail possums was significantly (p <0.0001) higher than that of woylies at both experimental sites during 2003 and 2005. Total trap success was compared between sites for woylies and brushtail possums. There was a significant ex;= 16.41, p <0.01) difference in the trap success between the sites for woylies, and a highly significant ex;= 42.04, p <0.001) difference for brushtail possums for the 2003 trapping. The trap success for woylies, per 100 trap nights, was not significantly ex;= 4.1358, p >0.100) different between seasons for site B in 2005. Similarly, the trap success for brushtail possums, per 100 trap nights, was not significantly ex; =2.8565, p >0.200) different. However, brushtail possums, for all seasons, had a significantly (ex12 =103.9, p <0.0001) higher trap success compared with woylies for site B. Site A was not analysed due to the lack of woylies at this site from 2004 onwards. Trapping at the control site failed to catch woylies, and only one possum was caught during the trapping effort. Fungal spores occurred in 100% en= 16) of woylie scats for winter, spring and summer. During the three seasons analysed, woylies consumed an equal balance of spore types from hypogeal (n = 7) and epigeal en= 7) fungi. Overall, woylies ate eight spore types in winter and 12 spore types in spring. Fungi appeared to be important in the diet of brushtail possums during autumn and summer as a higher percentage of brushtail possums had fungal spores in their scats during these seasons compared with spring (x12= 13.94,p <0.001) and winter (x12 =8.65, p <0.005). The percentage of brushtail possums that consumed fungi during winter and spring did not (x12 = 1.128, 0.250 > p <0.500) differ, nor did the percentage of brushtail possums that ate fungi in autumn and summer (X12 = 0.00046, 0.925> p <0.99). The major spore type consumed throughout the year by both the brushtail possum and the woylie was Mesophellia. However, the amount of Mesophellia consumed by the brushtail possum differed between seasons (F = 83.472, df=1, p <0.001) as it was only dominant in the diet during the hotter months (i.e. summer and autumn). Austrogautieria and Mesophellia were the only spore types present in both brushtail possum and woylie scat samples in summer. In contrast to Mesophellia, spores of Gastrotylopilus dominated the brushtail possum and woylie scat samples during the cooler seasons (winter and spring) and were absent in summer and autumn. They occurred in significantly higher densities in winter than spring (F= 10.390, df = 1 p = 0.002) in brushtail possum scats. Overall, woylie scats contained a higher density of spores for all spore types than in brushtail possum scats. The total spore densities per gram of scat for woylies were 348.4 x 104 ± SE 277.1 x 104 for winter, 170.7 x 104 ± SE 110.3 x 104 for spring and 1353.4 x 104 ± SE 450.6 x 104 for summer. At site A the spatial distribution of adult sandalwood trees, adult to juvenile, adult to seedling and juvenile to juvenile were aggregated (p <0.05), whilst seedling to seedling distribution was highly aggregated (p <0.005). The density of adults was approximately 24 trees ha-1, there were approximately 107 saplings ha-1 and approximately 128 seedlings ha- 1. The furthest sandalwood seedling found growing away from an adult was 91 m. At site B the distribution of mature adult trees, adults to saplings and saplings to saplings were all highly aggregated (p <0.005). Adults occurred at an approximate density of 81 trees ha-1, and saplings at 38 trees ha-1. At the control site, mature trees were highly aggregated (p <0.005) with a density of 15.7 trees ha-1. There were very few seedlings and saplings at the site, all of which were clumped under or around the crown of the parent tree. Log-linear analysis indicated a significant two-way interaction between the presence of woylies and the distance the offspring were found in relation to adult trees (x; = 288.4,p <0.0001) and between the presence of woylies and the age of the offspring (saplings and seedlings) (x; = 34, p <0.0001). Thus, in Dryandra, where woylies were present, there were higher numbers of both seedlings and saplings growing more than 1 m from adult trees, compared with Wickepin Water Reserve, where woylies were not present. Conversely, in the absence of woylies, more seedlings and saplings grew less than 1 m from adult trees. For the three year survival rates of seedlings surveyed for the three sites, log-linear analysis indicated a significant two-way interaction between site and seedling survival (x23 = 218, p <0.0001) and between seedling survival and under/away from parent crown (x23 = 107, p <0.0001). Site A experienced significantly higher mortality of seedlings growing away from the crown after three years compared with site B, whilst the control site suffered significant seedling mortality under the crown. There was a highly significant (one-way ANOVA, F(2,99)= 125.58, p <0.0001) difference between Dryandra Woodland and Wickepin Water Reserve in the mean number of whole seeds found under adult sandalwood trees. The mean number of whole seeds under the parent crown at site A was 0.97 ± 0.16, range 1 to 2 (n = 34). At site B the mean was 0.76 ± 1.67, range 1 to 9 (n = 34), while at the control site the mean was 59.97 ± 11.19, range 10 to 330 (n = 34). A posteriori analysis indicated that the mean number of whole seeds under the parent crown at Wickepin Water Reserve, where woylies were extinct, was significantly greater than those at Dryandra Woodland where woylies were still present (p <0.0001). Log-linear analysis indicated a significant two-way interaction between the presence of woylies and the distance the offspring were found in relation to adult trees (x22 = 288.4, p <0.0001) and between the presence of woylies and the age of the offspring (saplings and seedlings) (x22= 34, p <0.0001). To enable large numbers of seeds to be tracked effectively over a period of time, two experiments were undertaken using a labelling technique with the isotope scandium-46 (Sc46). Scandium-46 is a moderate beta and a high level gamma-emitting radionuclide with a half life of 83.6 days and a maximum photon energy of 1.12 Mega electron volts (MeV) 100%. It is the high gamma emissions that allow seeds labelled with Sc46 to be tracked using a Geiger Muller (GM) counter to determine their fate. Scandium-46 is absorbed by the seed hull and each seed typically received ~ 1 microcurie (uCi) [37 ki1obecquerel (kBq)] of activity, sufficiently strong to allow detection of buried seeds from about 30 cm with a GM counter. The seeds labelled for the May 2005 experiment were sandalwood, S. acuminatum (quandong), Acacia acuminata (jam) and Gastrolobium microcarpum whilst in the February 2006 experiment only sandalwood seeds were used. In the May 2005 experiment, woylies ate or cached all the sandalwood seeds before any interaction with either S. acuminatum (quandong), Acacia acuminata (jam) or Gastrolobium microcarpum seeds ocurred. In the first night all the sandalwood seeds had been removed with 26 cached and 24 seeds eaten in situ under or within 1 m from the source tree. The woylies took three nights to remove all the quandong. On the third night the rate of removal increased which resulted in 6 cached seeds and 39 seeds were consumed in situ. The next type of seed to be removed was the Acacia acuminata which were all consumed by one woylie. No Acacia seed caches were found. On the fifth night of the experiment the majority of Gastrolobium seeds were observed to be eaten in situ by one woylie. Two caches of Gastrolobium seeds were located, one cache with 22 seeds and one with 15 seeds buried within 8 m of each other. In the February 2006 experiment, of the 500 seeds deployed under the source tree over four nights, 211 (42.2%) were eaten in situ, 185 (37%) were cached and 104 (20.8%) had an unknown fate. Individual seeds were buried between 1 and 6 cm deep (mean 3.15 ± SE 0.11 em). By November 2006, 185 primary, 120 secondary, 52 tertiary, 35 quaternary and 17 quintic caches had been located. Of the 185 seeds initially buried, 40 (21.6%) seeds had been dug-up and eaten in situ, 5 (2.7%) were left undisturbed in the caches, 20 (10.8%) were removed from the area, their fate unknown, and the remaining 120 (65%) seeds were re-cached into secondary caches. Of the 120 secondary caches, 38 (32%) seeds were dug up and eaten in situ, 12 (10%) were left undisturbed, 18 (15%) were removed from the area, their fate unknown, and 52 (43%) had been re-cached into tertiary caches. Subsequently, seven (13.5%) of the seeds were consumed from these caches, 10 (19.2%) were left undisturbed and 35 (67%) seeds were re-cached to quaternary caches. From the quaternary caches, 12 (34.2%) seeds were dug-up and eaten in situ, 6 (17.1%) caches were left undisturbed and 17 seeds were dug-up and recached for a fifth time. Of these quintic caches, 4 were dug-up and eaten, 5 (29.4%). The most common site for primary through to quintic caches was A. acuminata. The next most common area for primary to quaternary caches was out in the open not near any particular vegetation type. The exception was the location of quintic caches which had a higher percentage of caches under fallen logs (24% n = 4) compared with out in the open (18% n = 3). There were a relatively high number of seeds cached within 30 em of a sandalwood tree in all types of caches. The fate of 17 individual seeds that were cached and re-cached in five different caches was mapped, however, it remains unknown whether the same woylie that made the primary cache went on to move the seeds five times or whether it was several different woylies moving the seeds around. The fate of cached seeds was monitored for germination rates in situ. All the seeds were eventually consumed from the May 2005 experiment before any germination could take place. For the 2006 experiment, overall germination rates were low with only 6 (15.8%) of seeds from the 38 undisturbed caches germinating. Of these, two from the secondary caches germinated out in the open and did not survive. The single seed from an undisturbed tertiary cache germinated beneath a fallen log as did one of the seeds that germinated and survived from the undisturbed quintic cache while another successfully germinated beneath a G. microcarpum bush. Olfaction appeared to be the principle method used by woylies to locate buried seeds, a process which they are very efficient at. There was a significant (x12 = 6.5, 0.025> p <0.01) difference in the number of artificially cached seeds dug-up by woylies compared with disturbance of the control 'caches'. Of the 80 caches, 65 (81.2%) were located by woylies over three nights. During the same time period, 39 (48.7%) of the control 'caches' showed signs of being disturbed, thus suggesting that woylies were, at least in part, responding to the smell of disturbed soil as well as the actual seed. Furthermore, there was also a highly significant (x12 = 7.5, 0.01> p <0.005) difference between the number of seeds located by woylies under leaf litter compared to the control. All of the 20 seeds under the leaf litter were located within two nights compared with only six (30%) of the control 'caches' in the leaf litter showing signs of disturbance. The predation rates of buried seeds and emerging seedlings was measured. After distributing 100 sandalwood seeds under a random sandalwood tree at each site, there was significantly (x12 = 12.25, p <0.0001) less seed disturbance at Site A on the first night compared to site B. Conversely, on the third night there was significantly (x12 = 10.96, p <0.0001) more seed disturbance at site A compared with site B. All of the 100 seeds had been eaten in situ or removed by woylies at the end of the third night at site B whilst at site A the 100 seeds were eaten in situ or removed by woylies by the end of the fourth night. It is without doubt that woylies are prolific seed cachers and that their relationship with sandalwood is complex and mutual in nature. The woylies benefit by consuming some of the large nutritious seeds sandalwood produces. In-turn, sandalwood benefits by having a vector, the woylie, to disperse their seeds many of which are buried in areas conducive to germination, for example, under fallen logs and near sandalwood's host species. Woylies are able to very efficiently locate buried seeds by using olfaction and possibly visual clues of disturbed earth during random foraging for hypogeous fungi, although there was no evidence to suggest they use spatial memory to locate seeds. To determine if woylies use emerging seedlings as markers, seedlings were grown in the greenhouse and transplanted in Dryandra. Of the 46 seedlings transplanted at site A, 14 (30%) were intact and growing after one month. A total of 23 seedlings (50%) were dug-up by woylies. Of these, 17 (37%) were discarded whilst the remainder of the endosperm was eaten in situ leaving the endocarp on the ground. In the remaining six (13%) seedlings the endocarps were removed from the area, presumably to be eaten elsewhere rather than re-cached as they would have been split open during the germination process and, therefore, no longer suitable for storage. Similar numbers and fates were recorded at site B with 10 ( 43%) left intact, 22 (51%) of the seedlings had been dug-up by woylies and discarded whilst the remainder of the epicarp was eaten in situ leaving the endocarp on the ground. Three (7%) of the seedlings were dug-up by woylies but again the endocarps were removed from the area. Six (14%) seedlings at site B were also grazed and two (5%) seedlings died. There was no significant (x12 = 3.96, p <0.25) difference between sites for the fate of seedlings. The majority of seeds that were retrieved by woylies from the seedlings were eaten in situ at both sites. There was no significant (x12 = 1.583, 0.25 < p > 0.10) difference between sites for seeds eaten in situ or removed from the area. The fate of the seeds removed from the area was unknown. It was concluded that woylies have both a mutualistic and antagonistic relationship with sandalwood and its propagules and as a result may strongly influence the recruitment and spatial distribution of sandalwood by reducing the number of seeds and seedlings available for dispersal and regeneration, respectively. Woylies are both pre and postdispersal predators consuming seeds under the parent trees, seeds that have been dispersed away from the parent trees and buried and germinating seeds. Evidence has been provided to support the early anecdotal reports that woylies use emerging seedlings as 'markers' to locate buried seeds. This is the first study of its type in Australia to demonstrate, unequivocally, the consequences of the loss of a key seed-dispersal vector, the woylie, on sandalwood recruitment and regeneration in Dryandra Woodland. Through seed-caching and seed-predation, woylies have been shown to substantially alter the fate and distribution of sandalwood seeds and seedlings. The loss of woylies from 97% of their former range will undoubtedly have serious implications for sandalwood and possibly other plant species. In losing this seed-dispersing and seed-caching animal from our ecosystems we have lost a keystone species. The woylie sandalwood interaction seems to have shaped the morphology of the sandalwood seed and fruiting phenology by making the propagules attractive and rewarding to the woylie. In this way both the woylie and sandalwood benefit from this interaction. Such close interactions have a positive impact on the health and functioning of ecosystems and landscapes.

Arid areas are often overgrazed and dysfunctional with poor recruitment of desirable species, diminished control over resources and altered soil properties. Restoration ecology re-establishes these valued processes. State-and-transition models summarise knowledge of vegetation dynamics and tools for restoration, and encourage the incorporation of new information. The model developed here for semi-arid woodlands of north-west Victoria highlighted the unknown cause of observed, natural recruitment and the need for a technique, other than direct seeding and handplanting, for enhancing the recruitment of desirable species. I pursued these knowledge gaps for two dominant, woodland trees: Allocasuarina luehmannii and Casuarina pauper. Natural recruitment of juvenile C. pauper was found to be limited and primarily from root suckers. Extensive recruitment of A. luehmannii was shown to be mostly seedlings established following substantial reductions in grazing pressure since 1996. Seedlings were associated with areas devoid of ground flora near a female tree. The importance of competition between seedlings and ground flora, spatial variation in soil moisture and individual variation in the quantity of seed produced deserves further investigation to enhance future restoration success. Root suckers of both C. pauper and A. luehmannii can be artificially initiated, albeit in low numbers and this was found to be a feasible, new tool for restoration. Suckers are preceded by the growth of callus tissue on exposed or damaged, living, shallow roots. Both male and female trees can produce suckers and spring treatments may be more successful. Genetic fingerprinting of mature A. luehmannii and C. pauper trees in six populations did not identify any clonal individuals indicating that recruitment in the past has been from seedlings. Despite this, the high level of gene flow suggests that the impact of introducing small numbers of root suckers into existing populations is unlikely to impact negatively on the population genetics of these species.
Doctor of Philosophy

Arid areas are often overgrazed and dysfunctional with poor recruitment of desirable species, diminished control over resources and altered soil properties. Restoration ecology re-establishes these valued processes. State-and-transition models summarise knowledge of vegetation dynamics and tools for restoration, and encourage the incorporation of new information. The model developed here for semi-arid woodlands of north-west Victoria highlighted the unknown cause of observed, natural recruitment and the need for a technique, other than direct seeding and handplanting, for enhancing the recruitment of desirable species. I pursued these knowledge gaps for two dominant, woodland trees: Allocasuarina luehmannii and Casuarina pauper. Natural recruitment of juvenile C. pauper was found to be limited and primarily from root suckers. Extensive recruitment of A. luehmannii was shown to be mostly seedlings established following substantial reductions in grazing pressure since 1996. Seedlings were associated with areas devoid of ground flora near a female tree. The importance of competition between seedlings and ground flora, spatial variation in soil moisture and individual variation in the quantity of seed produced deserves further investigation to enhance future restoration success. Root suckers of both C. pauper and A. luehmannii can be artificially initiated, albeit in low numbers and this was found to be a feasible, new tool for restoration. Suckers are preceded by the growth of callus tissue on exposed or damaged, living, shallow roots. Both male and female trees can produce suckers and spring treatments may be more successful. Genetic fingerprinting of mature A. luehmannii and C. pauper trees in six populations did not identify any clonal individuals indicating that recruitment in the past has been from seedlings. Despite this, the high level of gene flow suggests that the impact of introducing small numbers of root suckers into existing populations is unlikely to impact negatively on the population genetics of these species.
Doctor of Philosophy

Levels of carbon dioxide in the atmosphere have been steadily increasing since the beginning of the Industrial Revolution in the 1800s. The earth's climate is sensitive to alterations in these levels of carbon dioxide and other greenhouse gases (GHG), with significant changes in climate predicted long term. The adoption of the Kyoto Protocol in 1997 heralded a new age in terms of greenhouse gas accounting and emissions responsibility, for all nations. In Australia, carbon emissions from the Land Use and Land Use Change and Forestry sector are responsible for a large proportion of the national total emissions. Radar remote sensing has demonstrated considerable potential in the estimation and mapping of vegetation biomass and subsequently carbon. The aim of this research is to investigate the potential of airborne polarimetric radar for quantifying and mapping the biomass and structural diversity of woodlands in semi-arid Australia. Initial investigation focussed on the physical structure of the woodland, which revealed that despite a diversity of woodland associations, the species diversity was relatively low. Both excurrent and decurrent growth forms were present, which subsequently resulted in varying allocation of biomass to the components (i.e., branches, trunks). In view of this, both empirical and modelling methodologies were explored. Empirical relationships were established between SAR backscatter and the total above ground biomass. Considerable scatter was present in these relationships, which was attributed to the large range of species and their associated structures. Comparison of actual and model simulations for C-, L- and P-band wavelengths, reveal that no significant difference existed for these wavelengths, except at CHH, and the cross-polarised data at L- and P-band. The study confirmed that microwaves at C-band interacted largely with the leaves and small branches, with scattering at VV polarization dominating. Compared to the lower frequencies, the return from the ground surface (as expected) was significant. The differences in scattering mechanisms (i.e., branch-ground versus trunk-ground) between excurrent and decurrent structures were due largely to the larger angular branches associated with Eucalyptus and Angophora species, which were absent from Callitris glaucophylla.

Human-induced fires are a major disturbance in Baikiaea plurijuga woodland savannas that are economically important for timber production. Most fires occur during the late dry season, when they may severely damage woody plants. Prescribed burning during the early dry season is a management strategy to reduce fuel loads and thus the incidence of intense fires during the late dry season. There is, however, little information on fire behaviour characteristics of early dry season fires.We studied the relationship between experimental fuel conditions and fire behaviour by lighting 15 fires during the early dry season in a Baikiaea woodland. Fire intensity ranged from 25 to 1341 kW m[superscript (-1)], while rate of spread of fire varied between 0.01 and 0.35ms[superscript (-1)]. Fire intensity and rate of spread were positively related to flame height, leaf-scorch height and proportion of the area burnt. The relationships suggest that fire characteristics can be retrospectively determined using a variable such as scorch height. The grass fuel load, wind speed, relative humidity and to a lesser extent fuel moisture were important predictors of rate of spread, flame height, leaf-scorch height and proportion of the area burnt, with no impact due to the litter fuel load. The grass fuel load and wind speed had a positive effect on rate of spread, whereas relative humidity and fuel moisture had a negative effect. These findings indicate that managers can predict the likely damage to woody plants during an early dry season burn by assessing the grass fuel load and weather conditions at the time of burning.

Human-induced fires are a major disturbance in Baikiaea plurijuga woodland savannas that are economically important for timber production. Most fires occur during the late dry season, when they may severely damage woody plants. Prescribed burning during the early dry season is a management strategy to reduce fuel loads and thus the incidence of intense fires during the late dry season. There is, however, little information on fire behaviour characteristics of early dry season fires.We studied the relationship between experimental fuel conditions and fire behaviour by lighting 15 fires during the early dry season in a Baikiaea woodland. Fire intensity ranged from 25 to 1341 kW m[superscript (-1)], while rate of spread of fire varied between 0.01 and 0.35ms[superscript (-1)]. Fire intensity and rate of spread were positively related to flame height, leaf-scorch height and proportion of the area burnt. The relationships suggest that fire characteristics can be retrospectively determined using a variable such as scorch height. The grass fuel load, wind speed, relative humidity and to a lesser extent fuel moisture were important predictors of rate of spread, flame height, leaf-scorch height and proportion of the area burnt, with no impact due to the litter fuel load. The grass fuel load and wind speed had a positive effect on rate of spread, whereas relative humidity and fuel moisture had a negative effect. These findings indicate that managers can predict the likely damage to woody plants during an early dry season burn by assessing the grass fuel load and weather conditions at the time of burning.

Semi-arid woodlands are an important part of the Australian landscape and they have been the focus for scientific research by CSIRO since the 1960s. This book reviews that research and sets it in a historical perspective. It examines the development of pastoral science, with particular reference to the farming frontier in western New South Wales, as well as research conducted by CSIRO over the past thirty years aimed at helping manage increasing shrub densities while improving productivity. The author discusses past, current and future research directions and looks at how management perceptions and approaches continue to change as understanding of ecological processes and new strategies evolve.

From the end of the last glacial stage until the mid-Holocene, large areas of arid and semi-arid North Africa were much wetter than present, during the interval that is known as the African Humid Period (AHP). During this time, large areas were characterized by a marked increase in precipitation, an expansion of lakes, river systems, and wetlands, and the spread of grassland, shrub land, and woodland vegetation into areas that are currently much drier. Simulations with climate models indicate that the AHP was the result of orbitally forced increase in northern hemisphere summer insolation, which caused the intensification and northward expansion of the boreal summer monsoon. However, feedbacks from ocean circulation, land-surface cover, and greenhouse gases were probably also important.Lake basins and their sediment archives have provided important information about climate during the AHP, including the overall increases in precipitation and in rates, trajectories, and spatial variations in change at the beginning and the end of the interval. The general pattern is one of apparently synchronous onset of the AHP at the start of the Bølling-Allerød interstadial around 14,700 years ago, although wet conditions were interrupted by aridity during the Younger Dryas stadial. Wetter conditions returned at the start of the Holocene around 11,700 years ago covering much of North Africa and extended into parts of the southern hemisphere, including southeastern Equatorial Africa. During this time, the expansion of lakes and of grassland or shrub land vegetation over the area that is now the Sahara desert, was especially marked. Increasing aridity through the mid-Holocene, associated with a reduction in northern hemisphere summer insolation, brought about the end of the AHP by around 5000–4000 years before present. The degree to which this end was abrupt or gradual and geographically synchronous or time transgressive, remains open to debate. Taken as a whole, the lake sediment records do not support rapid and synchronous declines in precipitation and vegetation across the whole of North Africa, as some model experiments and other palaeoclimate archives have suggested. Lake sediments from basins that desiccated during the mid-Holocene may have been deflated, thus providing a misleading picture of rapid change. Moreover, different proxies of climate or environment may respond in contrasting ways to the same changes in climate. Despite this, there is evidence of rapid (within a few hundred years) termination to the AHP in some regions, with clear signs of a time-transgressive response both north to south and east to west, pointing to complex controls over the mid-Holocene drying of North Africa.

Arid and semi-arid ecosystems in South America are best illustrated by two desert regions, the Peruvian and Atacama Deserts of the Pacific coast and the Monte Desert of central Argentina. The caatinga of northeast Brazil is often described as semi-arid, but mostly receives 500–750 mm of annual rainfall and is better regarded as dry savanna. Small areas of Venezuela and Colombia near the Caribbean coast, and nearby offshore islands, support desert-like vegetation with arborescent cacti, Prosopis, and Capparis, but generally receive up to 500 mm annual rainfall. Substrate conditions, as much or more than climate, determine the desert-like structure and composition of these communities, and thus they are not discussed further here. Extensive areas of Patagonian steppe also have semi-arid conditions, as discussed in chapter 14. The Peruvian and Atacama Deserts form a continuous belt along the west coast of South America, extending 3,500 km from near the northern border of Perú (5°S) to north-central Chile near La Serena (29°55’S), where the Mediterranean- type climate regime becomes dominant. The eastward extent of the Peruvian and Atacama Deserts is strongly truncated where either the coastal ranges or Andean Cordillera rise steeply from the Pacific coast and, as a biogeographic unit, the desert zone may extend from 20 to 100 km or more inland. A calculation of the area covered by these deserts depends in part on how this eastern margin is defined. Thus the Peruvian Desert covers between 80,000 and 144,000 km2, while the Atacama Desert of Chile extends over about 128,000 km2 if the barren lower slopes of the Andes are included. Actual vegetated landscapes are far smaller and for the lomas of Perú change dramatically between years depending on rainfall. Only about 12,000 km2 of the Atacama contain perennial plant communities, largely in the southern portion known as the Norte Chico but also including a narrow coastal belt of lomas extending northward almost to Antofagasta and the Prosopis woodlands of the Pampa del Tamarugal. The vegetated areas of the coastal lomas of Perú and Chile together probably do not exceed 4,000 km2 as a maximum following El Niño rains.

Most of South America lies within the tropics, and lowland tropical ecosystems make up the majority of its landscapes. Although there is great concern for the Amazon ecosystem, the largest of the world’s tropical forests, there are many other fascinating and in some cases more endangered types of lowland forest. Such forests may be defined as lying below 1,000 m above sea level, although it is difficult to set arbitrary limits (Hartshorn, 2001). The two main lowland moist evergreen forests are the Hylea (a term coined by Alexander von Humboldt to denote rain forests of the Amazon Basin) and the much smaller Chocó forest on the Pacific coast between Panama and Ecuador. Two related yet distinctive types of forest are the Mata Atlântica or Atlantic moist evergreen forest and the Mata Decidua or dry deciduous forest, including the caatinga woodland, which is both deciduous and xerophytic (Rizzini et al., 1988). The latter two formations are among the most threatened of all South American forests. Lowland forests vary from dense and multilayered to open and single-layered, from evergreen to deciduous, and from flooded or semi-aquatic to near-arid. Tree heights range from 30 to 40 m with emergent trees reaching over 50 m, to forests where the tallest trees barely attain 20 m (Harcourt and Sayer, 1996; Solorzano, 2001). However, because of its extent and importance, Amazonia will form the principal focus of this chapter. Amazonia covers a vast area (>6 × 106 km2) and contains some 60% of the world’s remaining tropical forest. The Amazon and Orinoco basins influence not only regional climates and air masses, but also atmospheric circulation patterns both north and south of the Equator. The sheer size and diversity of Amazonia exhausts a normal repertoire of grandiose adjectives. The Amazon may or may not be the longest river in the world but it is by far the greatest in terms of discharge, sending around one fifth of the world’s fresh water carried by rivers to the oceans(see chapter 5; Eden, 1990; Sioli, 1984). The drainage basin is twice as large as any other of the world’s catchments.