Bird foraging height predicts bird species response to woody vegetation change

Accurate a priori predictions of the sensitivity of species to vegetation management depend on an understanding of mechanisms underlying species response. To date information on where birds forage in the vegetation strata has been used to predict bird species response to vegetation change caused by livestock grazing. Profiting from this link between vegetation structural diversity and bird diversity, we test whether this variable, bird foraging height, can be used to predict the impact of a different type of habitat alteration; vegetation encroachment. Increases in vegetation density, called ‘encroachment’ or ‘thickening’, throughout savanna landscapes are considered a serious management issue for pastoral activities and a potential threat to biodiversity. We developed woody-vegetation-change models to predict the effect of vegetation encroachment on bird species through an understanding of where birds forage in intact vegetation communities. We compare model predictions with bird abundance data collected from 60 field sites representing a single woodland vegetation type, but with a gradient of woody vegetation density caused by clearing, thinning and natural climatic perturbation. Our model successfully predicted for the majority (80%) of birds considered, whether a species was likely to increase, decrease or remain unaffected by increases in woody vegetation density. We find that the majority of species respond positively to vegetation encroachment. Our approach avoids problems of post hoc data interpretation and tests a specific mechanism underlying bird species response to habitat alteration, bird foraging height. Simple predictive models such as these will assist land managers make informed decisions about management actions and consequences, particularly in cases where decisions need to be made urgently and preclude the collection and analysis of primary ecological data sets.     

Soil and vegetation responses to hydrological manipulation in a partially drained polje fen in New Zealand

Anthropogenic drainage causes loss of natural character in herbaceous wetlands due to increased soil oxygen penetration. We related vegetation gradients in a New Zealand polje fen to long-term effects of drains by using hydrological, edaphic and vegetation data, and a before-after-control-impact (BACI) design to test responses to experimental drain closure. Soil profiles and continuous water level records revealed a site subject to frequent disturbance by intense but brief floods, followed by long drying periods during which areas close to drains experienced lower water tables and more variable water levels. Classification of vegetation data identified 12 groups along a moisture gradient, from dry areas dominated by pastoral alien species, to wet communities dominated by native wetland sedges. Lower total species diversity and native representation in pastoral communities were related to the high proportion of alien competitor and competitor-disturbance species, compared with the stress tolerator-dominated flora of other groups. Species–environment relationships revealed highly significant correlations with soil water content and aeration as measured by redox potential (E_H) and steel rod oxidation depth, as well as soil nutrient content and bulk density. Comparison of root anatomy confirmed greater development of flood-tolerant traits in native species than in pastoral aliens, and vegetation N:P ratios indicated that most communities were probably nitrogen-limited. Flooding rapidly re-established wetland hydrology in dried sites in the impact area, and lowered E_H and soil oxidation depth, but had no effect on N and P availability. Presence and cover of pastoral alien species decreased in these areas. This study supports the use of hydrological manipulation as a tool for reducing soil oxidation and thus the impact of alien plant species at restoration sites with minimal intervention, but suggests the need for detailed information on species flooding tolerances and hydrological preferences to underpin this approach.     

Mollusc and plant assemblages controlled by different ecological gradients at Eastern European fens

Ecological patterns of mollusc assemblages and vegetation in relation to water chemistry, water regime, nutrient availability and climate were studied in eastern Polish lowland fens. Our goal was to examine if major compositional changes differ for molluscs and vegetation under the joint influence of multiple ecological gradients. Altogether 32 fen sites were investigated in 2010–2011, and analyzed using metric multidimensional scaling, cluster analysis and generalized additive models. Two major gradients driving the differences in mollusc species composition were revealed. The main direction of compositional changes was associated with the water table gradient, governing a species turnover from inundated and strongly water-logged sites occupied mostly by aquatic mollusc species, to moderately wet sites with the predominance of fen and meadow species. The second most important gradient for molluscs was that of mineral richness. For vegetation, three major gradients explained the changes in species composition. The highest importance was assigned to the nitrogen-to-phosphorus availability gradient (defined as a shift from N-limited to P-limited vegetation), followed by the water table gradient, and the mineral richness gradient. Our results demonstrate that the impact of mineral richness gradient, which has been often reported as the major determinant of compositional changes of fen molluscs and vegetation, can be exceeded by other ecological gradients of comparable variation. We also document for the first time that the main species turnover of fen vegetation is not accompanied by the analogous change in species composition of mollusc assemblages, due to a different sensitivity of these taxa to particular environmental factors (i.e. water level dynamics and type of nutrient limitation).     

Epiphytic lichens as indicators of grazing pressure in the Mongolian forest-steppe

The ecological impact of the traditional land use by pastoral nomads on forest ecosystems is little studied. We analyzed the influence of livestock density on epiphytic lichen diversity in larch forests of the Mongolian forest-steppe, which we selected as a case example because pastoral nomadism is here most widespread within Central Asia. Canonical correspondence analysis showed that the epiphytic lichen vegetation was strongly influenced by the livestock density within a radius of 1 km around the sampled forests. Goats together with horses were most significant at shaping lichen vegetation in the forest edges as were horses alone in the forest interiors. This result matches with the results of interviews with 169 herder families and own field observations, which substantiate that goats preferably graze at the edges, whereas horses often browse the interiors. The livestock impact is thought to be primarily exerted through fertilization by the animals and mechanical abrasion. Based on an indicator species analyses, we propose to use epiphytic lichens as indicators of the grazing impact at different livestock densities in the Mongolian forest-steppe. The proposed indication system can be used as a tool for the rapid assessment of the livestock grazing impact. It has the advantage that it is thought to average the livestock impact of several years, which is important with regard to the nomadic style of livestock husbandry. The use of lichens as indicator species can at least partly substitute the time-consuming interviewing of the herder families to assess livestock densities and their impact on forest biodiversity. The proposed indicator system could thus be used as a planning tool for purposes of nature conservation.     

Relationships between plant diversity,vegetation cover,and site conditions: implications for grassland conservation in the Greater Caucasus

Overgrazing, land use abandonment and increasing recreational activities have altered the vegetation of high-montane and subalpine grassland of the Caucasus. The failure of previous restoration efforts with unsuitable and exotic plant species indicates the need for information on the present vegetation and in which way it might change. Within the Greater Caucasus, we have described and quantified the mountain grassland which develops under characteristic overgrazed and eroded site conditions. Further, we have proposed potential native plant species for revegetation to restore and conserve valuable mountain grassland habitats. We used non-metric dimensional scaling ordination and cluster comparison of functional plant groups to describe a gradient of grassland vegetation cover. For our study region, we identified four major vegetation types with increasing occurrence of ruderal pasture weeds and tall herb vegetation on abandoned hay meadows within the subalpine zone. Within high-montane grassland a decline of plant diversity can be observed on sites of reduced vegetation cover. Due to a low potential of the grassland ecosystem to balance further vegetation cover damage, the long-term loss of diverse habitats can be expected. We conclude with management recommendations to prevent erosion and habitat loss of precious mountain grasslands.     

Predicting the geographical distribution of plant communities in complex terrain – a case study in Fushian Experimental Forest, northeastern Taiwan

Ecosystem management and biodiversity conservation are usually implemented using information of several targeted species or cover-types and usually do not include information about communities. This is not because community-level information is unimportant for management purposes, but because the detailed fieldwork required for gathering community-level information at the scale for ecosystem management is usually impractical. We propose two methods to estimate the geographical distribution of plant communities with the objectives of covering large areas with minimal field efforts. The first method estimates the geographical distribution of plant communities by combining clustering methods with vegetation modeling, and the second extrapolates the geographical distribution of gradients in plant communities by combining gradient analysis with vegetation modeling. Vegetation modeling with clustering methods can be used to allocate sites with potentially higher alpha diversity, with the benefit of having a list of species associated with the clustered type. Vegetation modeling with gradient analysis can be used to identify regions with potentially the highest beta diversity by means of selecting regions with the widest range or highest variability in major DCA axes scores, and thereby help to preserve the scope of environmental conditions that lead to diversity in species assemblages. This is especially important because biological entities such as species, communities, or even ecosystems may cease to exist in the long run, and the preservation of processes that lead to biodiversity will eventually become more meaningful. We conclude that new methods to study and manage the processes that contribute to biodiversity at all scales should be and can be developed.     

Scaling hierarchy of factors controlling riparian vegetation patterns of the Fynbos Biome at the Western Cape,South Africa

Question: How can vegetation gradients be described in riparian zones located in a species‐rich mountain range and how do these gradients explain the variation found in the vegetation? Location: Hottentots Holland Mountains, Western Cape, South Africa. Methods: Three gradients (geographic, longitudinal, lateral) were defined to describe the complex vegetation patterns found here. The gradients are related as follows: (1) the geographic gradient: related to the climatic and topographical changes across the entire mountain range; (2) the longitudinal gradient related to the changes along the different river reaches; (3) the lateral gradient related to the processes along the profile of the riverbed. These three gradients operated on three different hierarchical levels. Partial Canonical Correspondence Analysis (pCCA) was used to determine the amount of variation that is explained on each of the hierarchical levels. Results: The geographical gradient explained the highest fraction (more than 50%) of the total variation explained. This can be ascribed to the high species turnover across landscapes in the Fynbos Biome; this is most likely an outcome that is specific for this region. The second most important gradient was the lateral gradient, which reflects stream power and inundation frequencies of the river. This gradient is represented by ca. 48% of the explained variation and this gradient explains the major disturbances occurring in a riverine ecosystem. The longitudinal gradient was the least important of the gradients and shows overlap with the geographical gradient. Conclusions: In the species‐rich environment of the Fynbos Biome geographical factors do not only account for variation in zonal vegetation but also for variation within azonal vegetation, like riparian corridors.     

A vegetation analysis of the pastoral landscapes of upland Wales,UK

Abstract. The upland moorlands of Wales are situated on the oceanic fringe of western Europe, and have experienced a long history of pastoral management. Recent vegetation data are analysed to assess the relative contribution of abiotic and anthropogenic factors to variation in habitat composition among the major upland ranges of this region. From a numerical analysis of plant community cover data, recorded from 65 sites covering 260 000 ha, a six‐cluster site classification emerged with striking biogeographical coherence. Direct gradient analysis and variance partitioning revealed strong correlation between vegetation composition and spatially‐structured climatic gradients, in particular temperature, rainfall and oceanicity; differences in bedrock geology appear to have a lesser role. The analysis also indicates a close correlation between habitat variation and anthropogenic parameters, especially grazing intensity, burning frequency, and sulphur and nitrogen deposition levels. At this regional scale, anthropogenic impacts appear to have accentuated, rather than obscured, vegetation patterns which are primarily determined by climate and other abiotic variables. The findings have considerable relevance for conservation planning and also for predictive studies on the consequences of climatic change for the biota of the uplands of southern Britain.     

Is livestock grazing compatible with biodiversity conservation? Impacts on savanna ant communities in the Australian seasonal tropics

Grazing by domestic livestock is one of the most widespread forms of anthropogenic disturbance globally, and can have a major impact on biodiversity and therefore conservation values. Here we use ants to assess the extent to which livestock grazing is compatible with biodiversity conservation in a tropical savanna of northern Australia, where there is growing pressure to intensify pastoral production. We focus on the extent to which ant responses conform with four general patterns identified in a recent global review: (1) soil and vegetation type have a far bigger impact on ant community composition than does grazing; (2) grazing modifies ant species composition but often not species richness or total abundance; (3) a species’ response often varies among habitats; and (4) between 25–50% of the species that can be statistically analysed are responsive to grazing. We sampled ants using pitfall traps at 38 sites in two land systems, based on cross-fence comparisons of areas of different grazing intensities. A total of 130 ant species from 24 genera were recorded, with the fauna dominated by species of Iridomyrmex and Monomorium. Land system was the primary driver of variation in ant species richness and composition, and grazing intensity was related to neither species richness nor total abundance. Only 10% of common species appeared to be impacted by grazing. Overall, ant responses to grazing in our study region were generally consistent with the four global patterns, except that the local fauna seems to be particularly resilient. Such resilience indicates that current grazing management practices are compatible with the conservation of ant biodiversity.     

From savannah to farmland: effects of land‐use on mammal communities in the Tarangire–Manyara ecosystem,Tanzania

Land‐use change is considered a major driver of biodiversity loss. In the western part of the Tarangire–Manyara ecosystem, we assessed large mammal species richness along a land‐use gradient (national park, uninhabited pastoral area and settled pastoral‐ and farmland). We found the highest species richness in the national park and in the pastoral area and lowest species richness in the settled and farmed area. There was little evidence of seasonal changes in species diversity. Except for top‐order carnivores, all functional feeding guilds were still represented in pastoral and settled areas. Although we did not find significant differences in body mass distributions and species’ representation of feeding guilds between the study sites, there was a trend that omnivores, mesopredators and top‐order carnivores tended to occur at lower species richness in agricultural areas than in the pastoral and fully protected areas. These results indicate that areas used for livestock keeping can maintain high wildlife species richness and that direct and indirect effects of agricultural and settlement expansions are the main drivers of species richness loss in the Tarangire–Manyara ecosystem and possibly other African savannah ecosystems. These results are useful for informed land‐use planning that aims to maintain species diversity and ecological connectivity between protected areas.     

Diversity of wetland vegetation in the Bulgarian high mountains, main gradients and context-dependence of the pH role

We fill a gap in understanding wetland vegetation diversity and relationship with environmental determinants in Bulgarian high mountains. A total of 615 phytosociological samples were taken from springs, mires, wet meadows and tall-forb habitats throughout Bulgaria, of which 234 relevés are from mire and spring vegetation above timberline. The vegetation was classified by TWINSPAN and the resulting vegetation types were reproduced by the formal definitions using the combination of Cocktail species groups based on phi-coefficient of joint co-occurrence of the species. Nine vegetation types of springs and fens have been clearly delimited above the timberline. All vegetation types include Balkan endemic species, the representation of which varies. Fens generally harbour more Balkan endemics than do springs, with the exception of species-poor high-altitude Drepanocladetum exannulati. The gradient structure of the vegetation was revealed by DCA and by CCA with forward selection of environmental factors. The major determinants of vegetation variation strongly differ above and below the timberline and likewise between springs and fens. The base-richness gradient controls the floristic variation of Bulgarian submontane fens, whereas the complete data set including both submontane and subalpine fens is governed by the altitude gradient from lowland and basin fens to subalpine fens rich in Balkan endemics. When focusing on sites above the timberline only, the first DCA axis separates fens from springs without organic matter. The major species turnover in springs follows the variation in water pH and mineral content in water, whereas fen vegetation variation is primarily controlled by succession gradient of peat accumulation. Altitude remains an important factor in all cases. Weak correlation between water pH and conductivity was found. This correlation was even statistically insignificant in fens above the timberline. Water pH is not influenced by mineral richness in Bulgarian high mountains, since it is buffered by decomposition of organic matter in fens. In springs, pH reaches maximum values due to strong aeration caused by water flow. The plant species richness decreases significantly with increasing altitude. The increase of species richness towards circumneutral pH, often found in mires, was not confirmed in Bulgarian high mountains. The correlation between species richness and pH was significant only when arctic-alpine species and allied European high-mountain species were considered separately. The richness of boreal species was independent on pH. Some of them had their optima shifted to more acidic fens as compared to regions below the timberline. Our results suggest that subalpine spring and fen vegetation should be analysed separately with respect to vegetation-environment correlations. Separate analysis of fens below and above timberline is quite appropriate.     

Conserving biodiversity in a changing world: land use change and species richness in northern Tanzania

Even though human induced habitat changes are a major driver of biodiversity loss worldwide, our understanding of the impact of land use change on ecological communities remains poor. Yet without such information it is difficult to develop management strategies for maintaining biodiversity in the face of anthropogenic change. To address this gap, we explored how land use practices impacted species richness in a mammalian community in northern Tanzania. Using camera traps, we estimated the number of mammalian species inhabiting three land use types subjected to increasing levels of anthropogenic pressure: (1) Tarangire National Park, (2) pastoral grazing areas; and (3) cultivated areas outside the park. Results showed that land use practice is correlated with different levels of species richness. Interestingly, mammal species richness was highest in the grazing areas and lowest in cultivated areas. When we focused our analyses on carnivores, we found little significant difference in species richness between the park and pastoral grazing areas, however, carnivore richness were significantly lower in the cultivated areas. We found no significant link between species body weight and presence in the three areas considered. Altogether, our results show that biodiversity conservation can be achieved outside national parks, with pastoral grazing areas holding a significant proportion of mammal communities; however increasing cultivation of pastoral rangelands may represent a major threat to mammalian communities.     

Declining plant species richness in the tussock grasslands of Canterbury and Otago, South Island, New Zealand

We studied vegetation change on 142 permanently marked transects spread throughout tussock grasslands of Otago and Canterbury, in areas subject to both pastoral and conservation management. The transects were established between 1982 and 1986 and remeasured between 1993 and 1999, providing a record of vegetation change at each site over an interval varying from 10 to 15 years. Each transect consisted of 50 quadrats, each 0.25m(2), in which the presence of all vascular plant species had been recorded. For each transect, we calculated the change between measurements in the mean number of species recorded per quadrat, and the change in the total number of species recorded per transect. Averaged across all transects, there was a significant decline in species richness between measurements at both the quadrat and transect scales. Small herbs (those less than or equal to2 cm tall, excluding Hieracium species) showed the greatest decline. On average, more than one quarter of the small herb species present in a quadrat at the first measurement had disappeared within 10 years. Larger herbs, ferns, rushes, sedges and grasses (excluding Chionochloa species) also declined significantly in species richness, reflecting declines in the abundance of species in these groups. Woody species richness remained constant, while species in the genera Chionochloa and Hieracium increased significantly in mean quadrat species richness, reflecting increases in the abundance of these species along transects. The rate of decline in mean quadrat species richness was unrelated to changes in the abundance of either Chionochloa or Hieracium species, or to an overall increase in total vegetation cover on transects. The rate of decline in species richness was also unrelated to the level of grazing or burning between measurements. However, the rate of decline in species richness was greater at lower elevation, on schist rock and on yellow-brown and yellow-grey soils. Our results suggest that a major compositional change is occurring in these grasslands at a rate that is independent of local variation in management and independent of the widespread invasion of these grasslands by Hieracium species.     

Human impacts on Persoonia falcata. Perspectives on post-contact vegetation change in the Keep River region, Australia, from contemporary vegetation surveys

Persoonia falcata R. Br. and Buchanania obovata Engl. seeds are consistently preserved in abundance from archaeological sites across the Keep River region from 3500 b.p. up until the contact period. Although artefacts continued to be deposited after establishment of the pastoral industry, remains of these two plant species disappear in the upper levels of all excavated deposits. The contemporary vegetation in the vicinity of these sites appears to lack P. falcata, although B. obovata remains in abundance. These observations raise questions regarding (1) the impact of changing land-use and fire regimes, (2) the impact of Aboriginal land management on particular plant species and (3) the reorientation of Aboriginal site use across the region after settlement. These issues are explored in this paper using a comparative analysis of stand structure of the contemporary vegetation around previously excavated sites, as well as from published information on recent regional fire history. Results show improved recruitment of P. falcata (that is, seedlings are recruited into adult life stages) in the only site where Aboriginal people have re-introduced customary management. Both the timing of burning and significant unburnt periods appear important to the post-contact decline and also in the future success of populations of P. falcata in the region.     

Pastoral Practices to Reverse Shrub Encroachment of Sub-Alpine Grasslands: Dung Beetles (Coleoptera,Scarabaeoidea) Respond More Quickly Than Vegetation

In recent decades, pastoral abandonment has produced profound ecological changes in the Alps. In particular, the reduction in grazing has led to extensive shrub encroachment of semi-natural grasslands, which may represent a threat to open habitat biodiversity. To reverse shrub encroachment, we assessed short-term effects of two different pastoral practices on vegetation and dung beetles (Coleoptera, Scarabaeoidea). Strategic placement of mineral mix supplements (MMS) and arrangement of temporary night camp areas (TNCA) for cattle were carried out during summer 2011 in the Val Troncea Natural Park, north-western Italian Alps. In 2012, one year after treatment, a reduction in shrub cover and an increase in bare ground cover around MMS sites was detected. A more intense effect was detected within TNCA through increases in forage pastoral value, and in the cover and height of the herbaceous layer. Immediately after treatment, changes in dung beetle diversity (total abundance, species richness, Shannon diversity, taxonomic and functional diversity) showed a limited disturbance effect caused by high cattle density. In contrast, dung beetle diversity significantly increased one year later both at MMS and TNCA sites, with a stronger effect within TNCA. Multivariate Regression Trees and associated Indicator Value analyses showed that some ecologically relevant dung beetle species preferred areas deprived of shrub vegetation. Our main conclusions are: i) TNCA are more effective than MMS in terms of changes to vegetation and dung beetles, ii) dung beetles respond more quickly than vegetation to pastoral practices, and iii) the main driver of the rapid response by dung beetles is the removal of shrubs. The resulting increase in dung beetle abundance and diversity, which are largely responsible for grassland ecosystem functioning, may have a positive effect on meso-eutrophic grassland restoration. Shrub encroachment in the Alps may therefore be reversed, and restoration of grassland enhanced, by using appropriate pastoral practices.     

Monitoring vegetation recovery in the early stages of the Dirk Hartog Island Restoration Programme using high temporal frequency Landsat imagery

Dirk Hartog Island is the largest island off the West Australian coast. From the 1860s to 2008, the island was managed as a pastoral lease. In 2009, the island was gazetted as a National Park and the process of removing introduced animals, to allow for the reintroduction of a suite of 12 native mammal species, began. With the removal of high numbers of goats and sheep concerns were raised regarding the proliferation of weed species (which would no longer be controlled through grazing) and the ability of the island’s native vegetation to recover. A vegetation monitoring programme was developed which integrated detailed floristic surveys, repeated site photography and Landsat time series data to provide a comprehensive picture of how the island’s vegetation cover had changed since destocking. The integration of these elements has allowed present‐day observations to be put into context of longer term landscape dynamics. Through statistical analysis of temporal sequences of Landsat satellite imagery, the timing of changes to phenology and cover at monitoring sites was related directly to the management action of stock removal. With the use of field observations, the species responsible for the increase in cover were identified. These data sources, when analysed together, allowed management to have confidence that, following destocking, native vegetation cover is increasing.     

The vegetation of Flat Top Hill: An area of semi-arid grassland/shrubland in Central Otago, New Zealand

An account is given of the vegetation of Flat Top Hill, in the driest part of semi-arid lowland Central Otago, New Zealand. Although highly modified, the area was acquired for conservation in 1992, following almost 150 years of pastoral use. The vegetation was sampled in a composite scheme using permanent monitoring sites placed to include the majority of habitats and communities present. A number of environmental factors were measured in each sample. Native species comprise 53% of the vascular flora of the area (211 species). From multivariate analyses of the data collected over three seasons, fourteen 'communities' are recognised. Although there are few constant or faithful species, strong relationships are shown with certain environmental parameters. Moisture stress is the major environmental influence on the vegetation; soil depth and past disturbance are secondary determinants. The communities differ by a factor of 10 in vascular species richness; the richest communities, and those with the greatest native component, are those around rock tors. Many of the communities present have not been reported from other vegetation surveys in Central Otago Moisture stress at xeric sites in the dry core of the region has excluded some exotic species, and allowed the survival of the native component, including three tiny spring ephemerals. Near elimination of grazing, as a result of reservation, will probably lead to an increase in the cover of taller, palatable exotic grasses and Thymus vulgaris, which may threaten the survival of some native species. Optimum management, for recovery or persistence of native species, may comprise exclusion of grazers in some areas, but continuity of grazing in others.     

Effects of human–livestock–wildlife interactions on habitat in an eastern Kenya rangeland

Human–livestock–wildlife interactions have increased in Kenyan rangelands in recent years, but few attempts have been made to evaluate their impact on the rangeland habitat. This study identified drivers of increased human–livestock–wildlife interactions in the Meru Conservation Area between 1980 and 2000 and their effects on the vegetation community structure. The drivers were habitat fragmentation, decline in pastoral grazing range, loss of wildlife dispersal areas and increase in livestock population density. Agricultural encroachment increased by over 76% in the western zone adjoining Nyambene ranges and the southern Tharaka area, substantially reducing the pastoral grazing range and wildlife dispersal areas. Livestock population increased by 41%, subjecting areas left for pastoral grazing in the northern dispersal area to prolonged heavy grazing that gave woody plant species a competitive edge over herbaceous life‐forms. Consequently, open wooded grassland, which was the dominant vegetation community in 1980, decreased by c. 40% as bushland vegetation increased by 42%. A substantial proportion of agro pastoralists were encountered around Kinna and Rapsu, areas that were predominantly occupied by pastoralists three decades ago, indicating a possible shift in land use in order to spread risks associated with habitat alterations.     

Do we know enough about vegetation dynamics to manage fire regimes in central Australia?

Ecologists have long been concerned that contemporary fire regimes of central Australia have poor consequences for some plant species, vegetation communities and the native animals they support. Fire frequency, size and intensity (the ‘fire regime’) have all been implicated in the decline of native biota and in vegetation changes that potentially constitute ecological drift. However, not all perceived declines and changes are quantified or proven. The fire regimes themselves defy quantification and are arguably unknowable. We examine the relationships between fire, vegetation and the physical landscape and consider the adequacy of available knowledge for guiding fire management. Devising targeted ‘fire management regimes’, which take into account vegetation type and management objectives such as pastoral production, conservation and cultural observance, and which actively use fire to achieve those objectives, is a more realistic goal than controlling unquantifiable fire regimes in spatially diverse landscapes.     

A novel approach to assess livestock management effects on biodiversity of drylands

In drylands livestock grazing is the main production activity, but overgrazing due to mismanagement is a major cause of biodiversity loss. Continuous grazing around water sources generates a radial gradient of grazing intensity called the piosphere. The ecological sustainability of this system is questionable and alternative management needs to be evaluated. We apply simple indicators of species response to grazing gradients, and we propose a novel methodological approach to compare community response to grazing gradients (double reciprocal analysis). We assessed degradation gradients of biodiversity under different management strategies in semiarid rangelands of the Monte desert (Argentina) by analyzing changes in vegetation, ants and small mammal richness and diversity, and variation due to seasonality. At the species level, we determined the trend in abundance of each species along the gradient, and the potential cross-taxa surrogacy. At the community level, the new methodological consists of assessing the magnitude of biodiversity degradation along different piospheres by comparing the slopes of linear functions obtained by the double reciprocal analysis. We found that most species showed a decreasing trend along the gradient under continuous grazing; while under rotational grazing fewer species showed a decreasing trend, and a neutral trend (no change in the abundance along the gradient of grazing intensity) was the most common. We found that vegetation cannot be used as a surrogacy taxon of animal response. Moreover, weak cross-taxa surrogacy was found only for animal assemblages during the wet season. The double reciprocal analysis allowed for comparison of multi-taxa response under different seasons and management types. By its application, we found that constrains in precipitation interacted with disturbance by increasing the negative effect of grazing on vegetation, but not on animal assemblages. Continuous grazing causes biodiversity loss in all situations. Rotational grazing prevents the occurrence of vegetation degradation and maintains higher levels of animal diversity, acting as an opportunity for biodiversity conservation under current scenarios of land use extensification. Our approach highlights the importance of considering multi-taxa and intrinsic variability in the analysis, and should be of value to managers concerned with biodiversity conservation.