Letteratura scientifica selezionata sul tema "Tussock grasslands"
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Articoli di riviste sul tema "Tussock grasslands"
1
Gutiérrez-Salazar, Patricia, e Paul M. Ramsay. "Physiognomic responses of páramo tussock grass to time since fire in northern Ecuador". Revista Peruana de Biología 27, n. 2 (24 maggio 2020): 205–14. http://dx.doi.org/10.15381/rpb.v27i2.17876.
Testo completoAbstract (sommario):
Ecologically-sound management plans for high-altitude grasslands of the Andes depend on an understanding the responses of plants to fire, especially the dominant tussock grasses. This study considers physiognomic responses of tussock grass in 13 sites in northern Ecuador with a known fire history, with time since fire 0.5–10 y, and a control site which had not been burned for at least 40 y. At each site, we assessed vegetation height, basal cover of the tussocks, and the ratio of dead:live leaves in tussocks. We also measured light at ground level. As recovery time increased, tussock cover and number decreased, while tussock height increased. Light levels fell sharply below the tussock canopies as recovery took place, and dead leaves accumulated quickly, reaching 60 – 70% by just two years after fire. The modification of physical tussock structure is likely to influence a much wider ecosystem response to fire, and determines directly the fuel load for future fires. Despite these clear changes in tussock characteristics, they were too variable to be used as a reliable bioindicator of time since fire. However, a better understanding of the responses of tussock grasses to fire and particularly its impact on other species should become the focus of further attention in future.
2
Rogers, G. M., e J. R. Leathwick. "North Island serai tussock grasslands: 2. Autogenic succession: Change of tussock grassland to Shrubland". New Zealand Journal of Botany 32, n. 3 (luglio 1994): 287–303. http://dx.doi.org/10.1080/0028825x.1994.10410472.
Testo completo
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Hunter, John T., e Vanessa H. Hunter. "Tussock and sod tussock grasslands of the New England Tablelands Bioregion of eastern Australia". Pacific Conservation Biology 22, n. 1 (2016): 12. http://dx.doi.org/10.1071/pc15037.
Testo completoAbstract (sommario):
We surveyed temperate montane natural grasslands across the New England Tablelands Bioregion (NETB) and assessed the phytosociology, occurrence and threats to these assemblages. In total, 123 full floristic survey plots were placed within natural grasslands across the NETB. Mapping was undertaken within a subset of the NETB using ADS40 imagery. Analysis of the floristic data was performed using the Kulzynski association measure and UPGMA fusion strategy. Canonical correspondence analysis was performed with species data in association with 42 environmental variables. An estimated 25 000 ha of native tussock and sod tussock grasslands within six floristic assemblages were found within the NETB. The maximum extent of predicted high-quality stands may only be 2500 ha with most occurrences degraded and threatened by agricultural practices, exotic species and changes in above- and below-ground water resources. Native taxa were significantly associated with altitude, rock type and differential temperature tolerances. Altitude, eastness (longitude) and radiation of the wettest period were significant drivers of exotic species occurrence.
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Lowther, W. L., M. E. Wedderburn e K. D. Trainor. "Reproductive phenology and natural reseeding of ‘Grasslands Maku’Lotus pedunculatusin tussock grassland environments". New Zealand Journal of Agricultural Research 35, n. 2 (luglio 1992): 157–62. http://dx.doi.org/10.1080/00288233.1992.10417713.
Testo completo
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Wearne, L. J., e J. W. Morgan. "Floristic composition and variability of subalpine grasslands in the Mt Hotham region, north-eastern Victoria". Australian Journal of Botany 49, n. 6 (2001): 721. http://dx.doi.org/10.1071/bt01025.
Testo completoAbstract (sommario):
Subalpine grasslands in the Mt Hotham area, Victoria, are a common feature of cold-air drainage valleys at elevations of 1260–1660 m. Here, the pooling of cold air prevents trees from establishing and results in a distinct grassland community, composed of tussock grasses and a wide variety of intertussock species. Despite their common occurrence in the region, such grasslands have yet to be fully described. This study focused on identifying the floristic composition of subalpine grasslands across 51 sites in the vicinity of Mt Cope, Dinner Plain and Mt Hotham. The vegetation was sampled from 172, 20-m2 quadrats which were analysed by multivariate ordination techniques. Environmental variables were quantified (i.e. soil depth, pH, aspect, slope, biomass, grazing intensity, altitude). Analysis revealed that the grassland sites varied greatly in their composition and richness. There was a gradual rather than abrupt change in species composition across grassland sites, thought to be related to both the geographic proximity of the sites and environmental factors such as geology. The following five grassland types were identified from the entire data set and defined primarily by the dominant species: Poa hiemata, Poa costiniana, Poa sieberiana, Poa labillardierei and Themeda triandra. Vector-fitting revealed significant correlations between the location of the quadrats in ordination space and altitude, biomass, pH and soil depth. Both increasing altitude and biomass were associated with the P. costiniana grasslands and some of the P. hiemata grasslands. The P. hiemata grasslands were widely distibuted across altitudes and geology (i.e. basalt and metamorphic). The lower-altitude grasslands (P. labillardierei, P. sieberiana, T. triandra) were associated with increasing pH and increasing soil depth. These grasslands were of limited extent and usually occupied small areas within larger grasslands dominated by P. hiemata or P. costiniana. The floristic composition of the Hotham grasslands (1260–1630 m a.s.l.), when compared with previously published data from the higher-elevation subalpine grasslands of both the Dargo High Plains (1450–1680 m a.s.l.) and Bogong High Plains (>1700 m a.s.l.), showed that there was no distinct differentiation between grasslands of these areas. However, there was a suggestion of gradual floristic change across this geographic range. This study highlights the need for ongoing conservation of grasslands in the Hotham area, particularly those at lower altitudes (1260–1450 m a.s.l.), which represent the upper limits of many temperate grassland species.
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Mark, AF. "Effects of Burning and Grazing on Sustainable Utilization of Upland Snow Tussock (Chionochloa spp) Rangelands for Pastoralism in South Island, New Zealand". Australian Journal of Botany 42, n. 2 (1994): 149. http://dx.doi.org/10.1071/bt9940149.
Testo completoAbstract (sommario):
The upland (800-2000 m) snow tussock (Chionochloa spp.) rangelands of South Island, New Zealand have a long history of burning that pre-dates human occupation during the last millennium. Their present extent in part reflects their ability to displace a range of woody vegetation, including forest, through tolerance of periodic fne. Research has confirmed the general tolerance of these grasslands to fire, though recovery of some features (e.g. biomass and flowering potential) may take more than 14 years. Mammalian grazing, by contrast, is a recent phenomenon, associated with European settlement and pastoralism over the last 150 years, on these mostly Crown (i.e. public-owned) lands. Such grazing, particularly when combined with regular burning, has usually resulted in prolonged reductions in tussock biomass, vigour and stability, as well as in the control and yield of water, potentially the most valuable product for humans from the upland grasslands. Fire promotes vegetative growth, flowering and seed germination within 2 years of burning. It also increases the palatability of these long-lived dominant grasses which are vulnerable to severe grazing by introduced ruminants, especially in the immediate post-fire recovery period when nutrients are reallocated from roots to leaf tissue. Management constraints, particularly restriction of grazing during the post-fie recovery period, have been inadequate to prevent continued degradation of the grasslands through weakening or displacement of the dominant tussock grass cover and a consequent loss of stability in many areas. Under pastoralism, the productive potential of the grasslands, together with their water, soil and nature conservation values have generally declined. Existing pastoral practices in many areas clearly represent non-sustainable utilisation of the rangelands for pastoralism. Recovery will be difficult and costly, both economically and socially. Some representative areas have been formally reserved and are being monitored to serve as baseline references.
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Rogers, G. M., e J. R. Leathwick. "North Island seral tussock grasslands. 3. The influence of heather (Calluna vulgaris) on rates of change from tussock grassland to shrubland". New Zealand Journal of Botany 34, n. 4 (dicembre 1996): 473–87. http://dx.doi.org/10.1080/0028825x.1996.10410128.
Testo completo
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García, Andrés, Alejandro Loydi e Roberto A. Distel. "Temporal and spatial variation in the soil seed bank of Nassella trichotoma (serrated tussock) in its native range". Australian Journal of Botany 69, n. 1 (2021): 45. http://dx.doi.org/10.1071/bt20046.
Testo completoAbstract (sommario):
Serrated tussock (Nassella trichotoma (Nees) Hack. ex Arechav) is an unpalatable grass species that has been expanding in its native range and invading non-native ranges. In this study in its natural environment, we aimed to describe the spatial relationship between seed density, the cover and density of standing individuals of serrated tussock, the seasonal variation in the seed density in the soil seed bank, and to compare these results with those reported in non-native ranges. We took soil samples seasonally and recorded the cover and density of standing individuals of serrated tussock at two sites in the native Pampas grasslands in central-east Argentina. Seed density was evaluated by seedling emergence and seed extraction. Seed density showed a seasonality trend, with maximum values in the end of summer and minimum values in winter and spring. Seed density was independent of the cover and density of standing individuals of serrated tussock. The values of seed density were lower than those reported in the invaded ranges. Since seeds of serrated tussock are present in the seed bank regardless of the cover and density of its standing individuals, the maintenance of a high cover of desirable species may play a key role in preventing the establishment of serrated tussock in both its natural and invaded ranges.
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Martin, HA, e A. McMinn. "Late Cainozoic Vegetation History of North-Western Australia, From the Palynology of a Deep Sea Core (ODP Site 765)". Australian Journal of Botany 42, n. 1 (1994): 95. http://dx.doi.org/10.1071/bt9940095.
Testo completoAbstract (sommario):
In the late Miocene, casuarinaceous forests were predominant in north-western Australia. Through the Pliocene and Pleistocene, Casuarinaceae declined and Poaceae increased, until grasslands predominated. Acacia and some other shrub species were present, suggesting possible shrublands. Surprisingly, however, there were very few Myrtaceae; hence, eucalypt dominated vegetation was never present in this part of Australia. The present vegetation of Acacia shrublands and tussock/hummock grasslands developed, therefore, from casuarinaceous forests. The late Cainozoic palaeovegetation is compared with others of equivalent age elsewhere in Australia.
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Yang, Ting Ting, Peng Li, Peng Tao Liu e Xin Hong Wu. "Distribution of Grassland Biomass Carbon Storage in China". Advanced Materials Research 518-523 (maggio 2012): 183–88. http://dx.doi.org/10.4028/www.scientific.net/amr.518-523.183.
Testo completoAbstract (sommario):
Grassland ecosystems plays a very important role in the global carbon cycle，But measured data is very lack. In this paper, based on the ground survey data of grassland in fourteen provinces in 2008 and satellite remote sensing data, biomass carbon storage in grassland ecosystem in China is estimated. The main conclusions are as follows: China's total grassland area is about 331.41×104 km2, the total biomass carbon storage in grassland ecosystem in China in 2008 was 951.73 TgC, The carbon storage in aboveground and belowground were 161.99 and 789.74 TgC respectively. Carbon storage of Underground was about 5 times more than that of aboveground. China's grasslands are mainly located in the northern arid and semi-arid regions and Qinghai-Tibet Plateau. Inner Mongolia has the highest total vegetation carbon storage. Heilongjiang province is the area which has the highest above-ground biomass density, while the lowest area is Ningxia province. warm-temperate shrub-tussock provides the largest portion of carbon storage in Chinese grassland vegetation (29.66%).
Tesi sul tema "Tussock grasslands"
1
Dickinson, Yvette L. "The spatial patterning of Hieracium pilosella invaded short tussock grasslands". Thesis, University of Canterbury. School of Forestry, 2008. http://hdl.handle.net/10092/1526.
Testo completoAbstract (sommario):
Hieracium pilosella is an invasive weed of New Zealand's short tussock grasslands. Since the 1960s, the abundance of H. pilosella has dramatically increased; it is now thought to occur in 6 million hectares of New Zealand (Espie, 2001), predominantly in grasslands. It is at least common in 42% of this area (Espie, 2001). Ecology is inherently spatial and as plants closely interact with their direct neighbours, the spatial arrangement of plants is vital to their functioning. A handful of recently published articles have implicated spatial structure of plant communities in theories of plant competition, resource use and the invasion of plant communities. The aims of this thesis were to: 1) determine if there are consistent spatial patterns in New Zealand's short tussock grasslands at relatively small scales (i.e. spatial relationships between individuals); 2) investigate how the invasion of H. pilosella may be altering these spatial patterns; and 3) establish if the spatial patterns of species, life-forms and root systems are being altered in different ways. Spatial patterns of both tussock and inter-tussock species, life-forms and root functional groups were evaluated at a range of short tussock grassland sites across a gradient of H. pilosella invasion levels in Canterbury, using both join-count statistics and Ripley's K-function. A classification system for the root functional groups of vascular species in these communities was developed and applied. It was found that species, life-forms and root functional groups in short tussock grasslands had generally consistent spatial patterns across sites both within and between species. These patterns were variable between significantly different levels of H. pilosella ground cover. The type of spatial pattern exhibited, and the way it was altered differed between species, life-form and root functional groups. For example, tussocks exhibited increased regularity up to scales of 160 cm and increasing aggregation at scales up to 500 cm, with increases in H. pilosella abundance. In contrast, both Agrostis capillaris and herbaceous chamaephytes had increased aggregation across scales up to 160 cm. These differences in spatial patterns along the gradient of invasion are a strong indication that H. pilosella is structurally fragmenting New Zealand's short tussock grasslands. This fragmentation is likely to have far reaching effects including the disturbance of invertebrate communities and the disruption of ecosystem services including pollination, vegetation regeneration, and nutrient cycling.
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Steer, Zuni. "Merino Sheep Habitat Use in Canterbury High Country Tall Tussock Grasslands". Thesis, University of Canterbury. Forestry, 2012. http://hdl.handle.net/10092/7270.
Testo completoAbstract (sommario):
Summary
1. The goals of this thesis were to determine whether Merino sheep use habitat at random. Specifically, this research was undertaken to identify areas of intensive use, determine daily activity patterns, explore habitat use between activities, between sheep, define home ranges and to explore the influence of weather on habitat use.
2. Sixteen Merino ewes were monitored using GPS collars recording locations every 15 minutes. A weather station was set up at 1380 m a.s.l. to record weather variables at the study site.
3. Merino ewes do not select and utilise habitat in proportion to its availability. Short tussock grassland was preferentially selected for despite having a low occurrence. Overall, ewes selected habitat that was within 400 metres of a water source, on slopes less than 30° and preferred easterly habitat.
4. Merino ewes utilised different habitat for different activities. The day was divided into grazing, resting and night camping, as determined from hourly movement, backed up by 10 days of visual observations. Grazing occurred mostly on flat to low slopes in short tussock grassland. Resting occurred mostly on the riverbed or on surrounding short tussock grassland. Night camping occurred at higher altitudes (~ 100 m higher) than the resting sites and was on steeper slopes, partly due to the U-shaped nature of the valley. Night camping occurred in tall tussock grassland and native mix habitat. Several night camps were used while a smaller number of grazing sites were used.
5. Sheep differed in their individual habitat use. Two sheep were explorers, one crossing the river to occupy adjacent land, and one sheep moved out of the original study area, passing through a narrow rocky gap. Some sheep stayed close to the main mobs, while others spread out in small groups.
6. Home ranges were affected by the presence of large mobs; those sheep in the main mob had smaller home ranges than those in smaller groups. Home ranges were also smaller in areas of higher quality forage.
7. Weather variables did affect sheep habitat use with rain having the most influence. One cold, wet, windy day resulted in sheep being less active while occupying the middle of the fan, so displayed a preference for grazing and resting at higher altitude than normal. Temperatures and wind had little effect on sheep habitat use.
3
Day, Nicola J. "Two decades of vegetation change across tussock grasslands in New Zealand's South Island". Master's thesis, Lincoln University. Bio-Protection and Ecology Division, 2008. http://theses.lincoln.ac.nz/public/adt-NZLIU20080304.145252/.
Testo completoAbstract (sommario):
New Zealand's South Island tussock grasslands have been highly modified by human activities, including burning, grazing and introductions of exotic plants for pastoralism. Studies suggest that tussock grasslands are degraded, in that native species have declined, and exotic species have increased in both diversity and abundance. These trends are primarily thought to be related to the impacts of grazing and subsequent grazing removal. Few studies have assessed long-term changes that have occurred in tussock grasslands, and those that have are generally limited to one particular location. This thesis aimed to investigate temporal changes in community structure in tussock grasslands, and relate these changes to environmental variables and land tenure. Data were used from 90 permanently-marked vegetation transects, which were set up on 19 geographically widespread properties in areas of tussock grassland across Canterbury and Otago in the South Island of New Zealand. The transects were on land in both conservation and pastoral tenure. Each transect was 100 m, and consisted of 50 0.25 m² quadrats. The transects were measured between 1982 and 1986 (first measurement), were re-measured between 1993 and 1999 (second measurement) and again between 2005 and 2006 (third measurement). A total of 347 vascular species were observed over the 90 transects and three measurement times. Species richness declined between the first and second measurements (first time interval), and increased between the second and third measurements (second time interval), at both the small (quadrat) and large (transect) scales. Both native and exotic species declined in mean quadrat species richness during the first time interval, and then increased during the second time interval. Changes in mean quadrat species richness were similar on transects in both conservation and pastoral tenure. Multivariate analysis of species' occurrences in quadrats identified a long gradient in species composition for these 90 transects. Four key plant communities were identifed along this gradient and differed in their mean elevation: (1) Highly-modified pastoral community, (2) Short-tussock grassland community, (3) Tall-tussock grassland community, (4) Alpine mat-forming species community. A detailed investigation into temporal changes that occurred on 53 transects that occurred in short- and tall-tussock grassland communities showed that changes in species composition were not consistent over time. Transects on different properties changed in species composition by different amounts. Specifically, in ordination space, transects on two properties changed in composition significantly more than transects on one other property. The property that a transect was on also affected the way that it changed in composition, i.e. native species were more likely to have increased on transects on some properties. Transects in conservation tenure did not change in species richness or composition differently from those in pastoral tenure. Considering that many native plants in tussock grasslands are relatively slow-growing, and that these areas have been grazed and burned for more than a century, we may expect it to be some time before we can detect differences in vegetation dynamics on conservation land from that on pastoral land. The changes in the community structure of these tussock grasslands were related to a combination of environmental factors, such as soil chemistry, climate, and management factors. This study has allowed greater understanding of vegetation change in tussock grasslands, and demonstrates the importance of long-term ecological monitoring in making reliable and accurate predictions about landscape-scale changes in tussock grassland community structure.
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Bloor, Marcus. "Review of current vegetation monitoring on privately protected land under ongoing economic use (grazing)". Thesis, University of Canterbury. School of Forestry, 2009. http://hdl.handle.net/10092/3681.
Testo completoAbstract (sommario):
There has been a noticeable shift in focus in biodiversity research in New Zealand over recent decades. Research has traditionally focused on biodiversity protection on the public estate, which was comprised primarily of ecosystems with lower productive potential (generally over 500m asl). Private lands generally have higher production potential and are often used for intensive cultivation and agricultural practices. They still however have significant potential for protecting biodiversity values. One of the key tools for protecting biodiversity values on privately owned lands in the Canterbury region are through legally binding QEII open space covenants and there is significant potential through industry certifications. QEII covenants are placed on the land in perpetuity and provide legally binding protection for biodiversity or landscape values within the covenant. This protection is voluntary and allows the land owner to continue to use the land for economic benefit providing it does not prove detrimental to biodiversity through monitoring outcomes. Case studies of QEII covenants that contain grazing clauses in the Canterbury region were used to determine what values are present and what monitoring is occurring in the field within these ecosystems. Photopoints and informal visual monitoring were the primary methods used by the QEII representatives to monitor vegetation in all of the covenants. Monitoring forms a critical feedback for all biodiversity protection. It is especially important to have an accurate feedback on vegetation condition and change from monitoring on properties that are grazed. Monitoring needs to be capable of providing sufficient information on vegetation change on these sites so that the most suitable grazing levels can be obtained by land managers. This thesis focuses on monitoring methods to ensure that this feedback is suitable and that the methods are cost effective. Current vegetation monitoring techniques were reviewed to determine which methods would be most suited to monitoring in these ecosystems where resources are tightly restricted and observers may not have existing skills and experience in monitoring these ecosystems. Methods reviewed were quadrats, transects, height-frequencies, photopoints, needle point, biomass, tagged plants, visual rank and remote sensing. Each method is described and then assessed on its suitability for monitoring tussock shrublands, with cost effectiveness being an important criterion. Of these methods quadrats, transects and height-frequencies were the most robust but also the most intensive and least cost effective methods. Visual rank, needle point and photopoints were the most cost effective, but are generally suited to monitoring single objectives. In most cases a combination of methods would be ideal to suit the objectives of the monitoring. QEII photopoint monitoring should follow guidelines more closely and include more complimentary information with their photographs. Clear monitoring objectives should be developed for every covenant that is grazed and these need to be determined before it is possible to accurately select appropriate monitoring methods. These objectives will also provide the monitoring program with more structure and direction. If possible a detailed management plan for each grazed covenant would be beneficial for values present. QEII are in a unique position, where they have the potential to develop a data base of biodiversity information for private land and contribute to other projects like the National Vegetation Survey (NVS).
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Dixon, Katherine Marguerite, e n/a. "Biodiversity along a gradient of modification : plant invertebrates and reptile diversity in mid-altitude tall tussock (Chionochloa rigida) grasslands, eastern Central Otago, New Zealand". University of Otago. Department of Botany, 2005. http://adt.otago.ac.nz./public/adt-NZDU20070130.154858.
Testo completoAbstract (sommario):
This thesis set out to examine the soils, plants, lichens, invertebrates and common skinks along a gradient of habitat modification. This gradient was represented by ten study sites, of varying management histories, in a mid altitude tall tussock (Chionochloa spp.) grassland in eastern Central Otago. One extreme of the gradient was represented by intact tall tussock plants with a high density of inter tussock vegetation. The other extreme was represented by intensively managed exotic pasture.
Native plants, invertebrates and reptiles were present along the entire gradient of modification and there was a clear threshold in the diversity of native plants along the gradient. This threshold was reached after the management practice of ploughing was applied to a site. Sites that had not been ploughed were found to be similar in their native plant diversity, and all unploughed sites had significantly higher native plant diversity than unploughed sites.
There was considerable variation in the abundance of individual plant and Coleoptera species along the modification gradient. The most intensively modified sites had the lowest plant diversity, the lowest abundance and diversity of Orthoptera, as well as the lowest abundance of common skinks. Sites with low levels of modification contained a higher abundance of common skinks, and, native forbs, lichens and bryophytes than the more intensively modified sites.
With regard to individual plant and Coleoptera species recorded, there were generally not clear thresholds for their presence and absence along the modification gradient. Rather, there was a gradual turnover for most species along the gradient such that the plant and Coleoptera community at opposing ends of the gradient had less species in common sites of similar modification levels.
A high proportion of the Coleoptera species observed were present in all sites, suggesting that disturbance has selected for an adaptive generalist life trait, and that the species remaining comprise the resilient portion of the Coleoptera fauna. The relationship between Coleoptera communities and the gradient of modification was scale dependent, with the strongest relationship being observed at the largest scale measured.
The hypothesis that faunal diversity and abundance would be best predicted by the structural diversity of the vegetation rather than by plant species diversity was tested. Structural diversity was strongly correlated (p < 0.01) with Coleoptera diversity, and Coleoptera abundance whereas plant species diversity was not. However, plant species diversity was a stronger correlate of common skink abundance than plant structural diversity. The structural diversity of the vegetation has the potential to be measured remotely and could be a correlate for faunal diversity and abundance when undertaking landscape scale studies.
This thesis demonstrates that native biota exists within the agricultural environment of the mid-altitude tall tussock (Chionochloa rigida) grasslands of eastern Central Otago despite intensive modification in some areas. The findings suggest that it is possible to integrate the objectives of agriculture and the conservation of some faunal groups especially for the more resilient species. However, this study also indicates that relatively unmodified sites are valuable reservoirs of biodiversity in the mid altitude zone and it is recommended that the limited number of lightly modified sites that remain in the mid altitude zone be conserved.
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Mason, Norman, e n/a. "Functional diversity and ecosystem-level processes in a short-tussock grassland". University of Otago. Department of Botany, 2006. http://adt.otago.ac.nz./public/adt-NZDU20061024.114054.
Testo completoAbstract (sommario):
Increased functional diversity has been linked to an increase in ecosystem level processes (ELPs), such as productivity, ecosystem reliability and invasion resistance. However, there has been no exact definition of functional diversity and it is not known which indices are appropriate for its measurement. Consequently, continuous indices have rarely been applied in examination of relationships between functional diversity and ELPs and little is known of the mechanisms linking functional diversity to ELPs. This thesis begins by providing an exact definition of functional diversity, identifying its primary components and devising appropriate continuous indices for the measurement of these components. These indices are used to examine relationships between functional diversity and three ELPs - biomass production, the reliability of biomass production and invasion resistance. Initially these examinations are conducted using a mechanistic community assembly and dynamic model. This model is based on physiological and morphological character data for species occurring in the short-tussock grassland communities of the Luggate field experiment, in the southern South Island, New Zealand. Finally, relationships between functional diversity, mean annual community cover and the reliability of cover are examined in the Luggate field experiment.
Functional composition (i.e. the actual functional characters of the species within a community) appeared to exercise the greatest influence on ecosystem reliability in the community assembly and dynamic model. However, there was evidence that functional diversity increased the reliability of productivity via the co-variance effect. Functional composition also exercised the greatest influence over mean annual productivity in the model, almost completely accounting for the negative relationship between functional diversity and mean annual productivity. These results are respectively analogous to the positive and negative selection effects seen in species richness / ELP relationships. Both functional diversity and functional composition influenced community invasion resistance in the model. Here, increased functional diversity acted to increase community resistance to invasion. In the Luggate field experiment, neither functional diversity nor functional composition was related to mean annual cover, though species richness was positively related to it. Increased functional diversity acted to increase the reliability of cover. However, this did not appear to occur via the co-variance effect, but as a result of increased functional diversity increasing consistency in the species composition of experimental plots through time.
These results demonstrate that studies examining functional diversity must account for the effects of species identity. A framework is proposed to accommodate selection effects associated with functional diversity / ELP relationships. The usefulness of the co-variance effect as a testable mechanism linking functional diversity to ecosystem reliability in the field is questionable, as there is no objective way of measuring it.
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Graham, Scott Luiken. "Components of ecosystem carbon dioxide exchange in a New Zealand tussock grassland under soil warming and nitrogen addition". Thesis, University of Canterbury. Biological Sciences, 2012. http://hdl.handle.net/10092/7367.
Testo completoAbstract (sommario):
Global temperatures are expected to increase by 1.1 to 6.4°C over the next century and, over the same period, nitrogen inputs to terrestrial ecosystems are expected to increase as a result of increased crop fertilisation and atmospheric nitrogen deposition. Both of these global change drivers are expected to affect net carbon balance by increasing both gross primary production and ecosystem respiration, yet the balance between these processes, and the potential interactive effects of the drivers, require quantification.
The ability to accurately predict the effects of warming and nitrogen addition on all components of terrestrial carbon balance will be critical in determining the likely positive feedback to rising atmospheric CO₂ from terrestrial ecosystems. Tussock grasslands are a widespread and important carbon store within New Zealand and are representative of temperate grasslands worldwide. This thesis addresses the question: Will tussock grasslands act as a positive feedback to rising atmospheric CO₂ concentration in response to soil warming and nitrogen addition?
Using a combination of controlled-environment and field-scale studies of tussock grassland, net ecosystem carbon exchange was partitioned into gross primary production, ecosystem respiration and the autotrophic and heterotrophic components of soil respiration. Soil respiration in the field increased by 41% in response to a 3°C soil warming treatment and by 12% in response to a 50 kg N ha⁻¹ y⁻¹ nitrogen addition treatment. Only warming resulted in enhanced heterotrophic decomposition of soil organic matter (37% increase). However, a controlled-environment study indicated that caution must be used when interpreting temperature responses of heterotrophic respiration from root-free soils, as priming effects were shown to decrease the sensitivity of heterotrophic respiration to temperature. Measurements of net ecosystem exchange in the field showed that warming-enhanced heterotrophic respiration lead to a significant 49 g m⁻² reduction in net ecosystem carbon uptake. Neither nitrogen addition nor combined warming and nitrogen addition treatment resulted in significant changes in net ecosystem carbon balance.
These results suggest that tussock grasslands will act as a positive feedback to rising atmospheric CO₂ concentration. However, increased nitrogen deposition will serve as a potential mitigating factor for climate driven feedbacks.
8
Meffin, Ross. "Invasion success and impacts of Hieracium lepidulum in a New Zealand tussock grassland and montane forest". Lincoln University, 2010. http://hdl.handle.net/10182/1808.
Testo completoAbstract (sommario):
Invasive species represent a major concern; they can result in serious ecological and economic losses and are recognised as one of the most serious threats to global species diversity. Plant invasions are of particular concern in New Zealand, which has high proportions of both naturalised and endemic plant species. In this thesis I focussed on the invasive plant Hieracium lepidulum, an exotic weed introduced from Europe to New Zealand prior to 1941. It is invasive in a variety of habitats in the South Island, where it has steadily increased in distribution and abundance over the last 50 years, and is thought to have detrimental impacts on native plant communities. I investigated factors influencing its invasion success and tested for impacts on native plant communities, making extensive use of existing plots into which H. lepidulum was experimentally introduced in 2003. I examined how community richness, turnover, resource availability and propagule pressure of the invader interacted to determine the invasion success of H. lepidulum. Results differed markedly above and below treeline. Above treeline, plots with higher richness and turnover were more invaded; below treeline, plots with higher available light were more invaded. In both habitats, these findings were modified by the influence of propagule pressure; at low propagule pressure, site characteristics were non-significant in explaining invasion success, while at higher propagule pressure these effects became significant. To test for impacts resulting in altered community composition and structure, I looked for changes in community richness, diversity and evenness subsequent to H. lepidulum introduction. As impacts may be more apparent at fine spatial scales, I made measurements at a 5 x 5 cm cell scale in addition to the established 30 x 30 cm plot scale. Plot species richness increased from 2003 to 2009 and a component of this increase was associated with H. lepidulum density. Other relationships between the plant community and H. lepidulum were generally non-significant. Results showed that H. lepidulum has had no negative effects on community richness, evenness or diversity. Despite being able to opportunistically colonise grassland sites with high turnover, and forest sites subject to canopy disturbance, dependant on propagule pressure, it appears H. lepidulum has not impacted community composition or structure.
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Thorpe, Andrea. "A study on the main factors affecting the competitive growth of Themeda triandra (Kangaroo grass) and the introduced weed, Nassella trichotoma (Serrated tussock)". Thesis, 1994. https://vuir.vu.edu.au/32996/.
Testo completoAbstract (sommario):
Little published information is available on the levels of soil nutrients and soil
moisture on remnants of native (Basalt Plains) grasslands.
This study investigated the association of soil nutrients and moisture with stands
of the native grass Themeda triandra (Kangaroo Grass) and the noxious weed
Nassella trichotoma (Serrated Tussock). Both mature and immature (i.e. recently
burnt) stands of T. triandra and N. trichotoma were investigated, on disturbed and
undisturbed soil.
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Dickinson, Yvette. "The spatial patterning of Hieracium pilosella invaded short tussock grasslands : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Science in Environmental Sciences in the University of Canterbury /". 2008. http://hdl.handle.net/10092/1526.
Testo completoLibri sul tema "Tussock grasslands"
1
Ashdown, Michael. Tussock grasslands: Landscape values and vulnerability. [Wellington]: New Zealand Environmental Council, 1987.
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2
White, E. G. New Zealand tussock grassland moths: A taxonomic and ecological handbook based on light-trapping studies in Canterbury. Lincoln, N.Z: Manaaki Whenua Press, 2002.
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3
Payton, I. J. Fire-induced changes to the vegetation of tall-tussock (Chionochloa rigida) grassland ecosystems. Wellington, N.Z: Publishing Team, Dept. of Conservation, 2009.
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4
New Zealand. Office of the Parliamentary Commissioner for the Environment., a cura di. Sustainable land use for the dry tussock grasslands in the South Island. Wellington, N.Z: Office of the Parliamentary Commissioner for the Environment, 1991.
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5
P, Barratt Barbara I., e New Zealand. Dept. of Conservation., a cura di. Impact of fire on tussock grassland invertebrate populations. Wellington, N.Z: Publishing Team, Dept. of Conservation, 2009.
Cerca il testo completoCapitoli di libri sul tema "Tussock grasslands"
1
Murray, T. J., K. J. M. Dickinson e B. I. P. Barratt. "Associations between weevils (Coleoptera: Curculionidea) and plants, and conservation values in two tussock grasslands, Otago, New Zealand". In Arthropod Diversity and Conservation, 109–23. Dordrecht: Springer Netherlands, 2006. http://dx.doi.org/10.1007/978-1-4020-5204-0_8.
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2
Allen, Will, e Chris Jacobson. "Learning About the Social Elements of Adaptive Management in the South Island Tussock Grasslands of New Zealand". In Adaptive Environmental Management, 95–116. Dordrecht: Springer Netherlands, 2009. http://dx.doi.org/10.1007/978-1-4020-9632-7_6.
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