Ungrazed Grassland Research Articles

The Grassland Birds of Rollapadu Wildlife Sanctuary, Andhra Pradesh, India, with Special Reference to the Impact of Grazing-Free Enclosures

Grassland bird composition was studied in grazed (village grazing lands) and ungrazed grasslands (grassland enclosures of the Forest Department) at Rollapadu Wildlife Sanctuary from August 1992 to July 1994, using belt transect sampling. A total of 32 grassland dependent birds (21 resident, 4 winter migrant, and 7 seasonal migrant) were recorded in both the habitat types. Of these, 25 species were recorded in each of the two habitat types with 20 of them common to both. Although based on small sample size, our study showed that the species composition differed between grazed and ungrazed grasslands. Five species common in grazed grassland (Indian Courser Cursorius coromandelicus , Redwattled Lapwing Vanellus indicus , Red-winged Bush-Lark Mirafra erythroptera , Rufous-tailed Finch-Lark Ammomanes phoenicurus , and Plain Prinia Prinia inornata ) were not recorded in ungrazed grassland, while two species common in ungrazed grassland (Zitting Cisticola Cisticola juncidis and Black Drongo Edolius macrocercus ) were not recorded in grazed grassland. The abundance of certain bird species differed between the grazed and ungrazed grassland. Ungrazed grassland had higher numbers of Oriental Skylark Alauda gulgula , while the numbers of Sykes's Crested Lark Galerida deva , Ashy-crowned Sparrow-Lark Eremopterix grisea , and Yellow-wattled Lapwing Vanellus malabaricus were greater in grazed grassland. These differences could be due to the impact of livestock grazing, protection, the interaction of relative abundance of food resources and foraging strategy of birds, and/or other unknown factors. The study suggests that mosaics of grazed and ungrazed grasslands may result in an increase in grassland bird diversity. However, since the majority of Indian grasslands are grazed, we recommend the establishment of more grazing-free refuges encompassing different grassland types, to conserve bird species intolerant to grazing. There necessarily has also to be a landscape-level conservation strategy since the majority of India's grasslands have high human dependence, and thus, their conservation requires the support of local communities in the long run.

Grazing‐induced changes in plant–soil feedback alter plant biomass allocation

Large vertebrate herbivores, as well as plant–soil feedback interactions are important drivers of plant performance, plant community composition and vegetation dynamics in terrestrial ecosystems. However, it is poorly understood whether and how large vertebrate herbivores and plant–soil feedback effects interact. Here, we study the response of grassland plant species to grazing‐induced legacy effects in the soil and we explore whether these plant responses can help us to understand long‐term vegetation dynamics in the field.In a greenhouse experiment we tested the response of four grassland plant species, Agrostis capillaris, Festuca rubra, Holcus lanatus and Rumex acetosa, to field‐conditioned soils from grazed and ungrazed grassland. We relate these responses to long‐term vegetation data from a grassland exclosure experiment in the field.In the greenhouse experiment, we found that total biomass production and biomass allocation to roots was higher in soils from grazed than from ungrazed plots. There were only few relationships between plant production in the greenhouse and the abundance of conspecifics in the field. Spatiotemporal patterns in plant community composition were more stable in grazed than ungrazed grassland plots, but were not related to plant–soil feedbacks effects and biomass allocation patterns.We conclude that grazing‐induced soil legacy effects mainly influenced plant biomass allocation patterns, but could not explain altered vegetation dynamics in grazed grasslands. Consequently, the direct effects of grazing on plant community composition (e.g. through modifying light competition or differences in grazing tolerance) appear to overrule indirect effects through changes in plant–soil feedback.

Grassland responses to grazing disturbance: plant diversity changes with grazing intensity in a desert steppe

AbstractThis study quantifies the impact of four different grazing regimes (heavy, moderate, light and ungrazed) on the vegetation dynamics of rangeland ecosystems along the southern boundary area of the Mu Us Desert, China. As the grazing intensities decreased, the soil quality, canopy cover, height, density, above‐ and below‐ground biomass, litter, root/shoot ratio and native plant (Aneurolepidium dasystachys) and grass abundances significantly increased; the above‐ground biomass of grasses increased, but the above‐ground biomass of forbs decreased. Ungrazed grassland has significantly improved from grasslands experiencing three other levels of grazing pressure, especially in the grassland biomass. Species richness increased as the grazing intensity decreased in the grazing grasslands, but peak species richness appeared under moderate and light grazing against lower productivity. Grazing exclusion causes desirable transitions in plant communities of desert steppe rangelands. Therefore, appropriate and efficient grazing exclusion is an available way to counteract local grassland degradation and promote rangeland sustainability.

Loblolly pine germination and establishment in plantations and grasslands of northern Uruguay

Afforestation, the practice of planting trees where they did not occur recently, is a common practice around the globe. In recent decades, afforestation has begun to occur in the Campos grasslands of South America. Exotic species are used for these plantations and potential encroachment of these trees into remaining grassland areas is a concern. We quantified the germination and establishment of loblolly pine (Pinus taeda) in and adjacent to five plantations in northern Uruguay. Transects were placed in grazed areas and in areas where grazing was experimentally excluded. Areas were sampled semi-annually for 2years to examine germination (seedling density in Spring) and establishment (seedling density in Autumn). In grasslands, seedlings were present only near the forest edge (<10m). Germination densities were significantly higher in forests than grasslands, and establishment densities tended to be higher in forests and ungrazed areas. Protection from livestock increased seedling establishment, particularly in the first year after the exclosures were built. However, the mechanisms controlling encroachment differ with grazing management: in ungrazed grasslands, the dense cover of herbaceous and grass species likely prevent establishment whereas in grazed grasslands, the intensive livestock grazing prevents tree establishment. Our results suggest that loblolly pine encroachment into adjacent grasslands is relatively unlikely, although further work is necessary to examine the long-term survival and growth of those individuals that do manage to survive in this habitat. Finally, similar studies should be undertaken with other species used to afforest these grasslands.

Differences in spatial autocorrelation (SAc), plant species richness and diversity, and plant community composition in grazed and ungrazed grasslands along a moisture gradient, North Dakota, USA

AbstractQuestionsHow are plant species richness and diversity related to spatial autocorrelation under grazed and ungrazed conditions in grassland communities? Is spatial autocorrelation dissimilar within different plant communities?LocationThe grasslands of southeast North Dakota, USA.MethodsThe study was conducted during the summer of 2009 in six grasslands under different management (grazed vs ungrazed with fire) along a moisture gradient. Spatial autocorrelation at each site was measured along 50‐m transects among three different landscape positions representing different moisture levels. Dissimogram multivariate analysis was used to measure the nugget, dissimilarity and patch diameter. Additionally, richness and Shannon diversity indices and nonmetric multidimensional scaling analysis were compared to the dissimogram results.ResultsMean patch diameter was significantly higher in grazed mid‐slope sites than in ungrazed sites. Spatial autocorrelation was not different between the landscape positions (higher, dry areas were not different from lower, mesic areas). However, plant species richness, diversity and community composition were found to be different between landscape positions and management, with key differences in the presence of certain invasive species.ConclusionsDisturbance and moisture level were reflected differently in the spatial autocorrelation analysis compared to the richness, diversity and ordination analyses. This indicates that disturbance and management impacted spatial autocorrelation separate from plant community composition and species diversity. This also highlights changes in the plant community caused by different management actions and the spread of invasive species.

Effects of grassland restoration programs on ecosystems in arid and semiarid China

We explored the ecological effects of grassland restoration programs using satellite imagery and field plots sampling data and analyzing the patterns and mechanisms of land cover change and vegetation activities in arid and semiarid China during the period from 1982 to 2008. The grassland cover in the 1980s, 2000 and 2005 was compared before and after the restoration programs. The variability of net primary production (NPP) and rain use efficiency (RUE) were analyzed as indicators of vegetation productivity. Our study showed that changes in grassland cover were closely related to the relative area of farmland, with increases in grassland being caused by returning farmland to grassland and decreases being caused by reclamation for agriculture. The results of NPP and RUE measurements over the past 30 years showed systematic increases in the area of grassland in most regions, especially from 2000 to 2008. This fact was reflected by intensified vegetation activity and cannot be completely explained by the warmer and wetter climate, which suggested a contribution from restored, ungrazed grasslands. Our analysis indicates that both vegetation activity and grassland cover increased in regions in which grassland and rangeland restoration programs were implemented.

Ecosystem Carbon and Nitrogen Accumulation after Grazing Exclusion in Semiarid Grassland

The grazing exclusion in degraded grassland has been extensively used to prevent the loss of grassland resources and to improve grassland services. The effects of grazing exclusion on C and N balance, however, have not been well addressed but are essential for assessing grassland C sinks, the sustainable use of grassland resources and the support of grassland services. To understand the response of ecosystem C and N to grazing exclusion in semiarid grassland, we determined the C and N in litter, aboveground biomass, roots and soils from ungrazed grassland fenced at different times in northwest China. Our results showed that the aboveground biomass, root biomass and plant litter were 70–92%, 56–151% and 59–141% higher, respectively, in grazer excluded grassland than in grazed grassland. Grazing exclusion significantly increased C and N stored in plant biomass and litter and increased the concentrations and stocks of C and N in soils. Grazing exclusion thus significantly increased the C and N stored in grassland ecosystems. The increase in C and N stored in soil contributed to more than 95% and 97% of the increases in ecosystem C and N storage. The highest C and N stocks in ecosystems were observed in 17-year grazer excluded grassland. The results from this study indicate that grazing exclusion has the potential to increase C and N storage in degraded semiarid grassland and that the recovery of ecosystem C and N was mainly due to the accumulation of C and N in soils.

Inter-specific competition, but not different soil microbial communities, affects N chemical forms uptake by competing graminoids of upland grasslands.

Evidence that plants differ in their ability to take up both organic (ON) and inorganic (IN) forms of nitrogen (N) has increased ecologists’ interest on resource-based plant competition. However, whether plant uptake of IN and ON responds to differences in soil microbial community composition and/or functioning has not yet been explored, despite soil microbes playing a key role in N cycling. Here, we report results from a competition experiment testing the hypothesis that soil microbial communities differing in metabolic activity as a result of long-term differences to grazing exposure could modify N uptake of Eriophorum vaginatum L. and Nardus stricta L. These graminoids co-occur on nutrient-poor, mountain grasslands where E. vaginatum decreases and N. stricta increases in response to long-term grazing. We inoculated sterilised soil with soil microbial communities from continuously grazed and ungrazed grasslands and planted soils with both E. vaginatum and N. stricta, and then tracked uptake of isotopically labelled NH4 + (IN) and glycine (ON) into plant tissues. The metabolically different microbial communities had no effect on N uptake by either of the graminoids, which might suggest functional equivalence of soil microbes in their impacts on plant N uptake. Consistent with its dominance in soils with greater concentrations of ON relative to IN in the soluble N pool, Eriophorum vaginatum took up more glycine than N. stricta. Nardus stricta reduced the glycine proportion taken up by E. vaginatum, thus increasing niche overlap in N usage between these species. Local abundances of these species in mountain grasslands are principally controlled by grazing and soil moisture, although our results suggest that changes in the relative availability of ON to IN can also play a role. Our results also suggest that coexistence of these species in mountain grasslands is likely based on non-equilibrium mechanisms such as disturbance and/or soil heterogeneity.

Impacts of grazing abandonment on ecosystem service provision: Coastal grassland as a model system

A coastal grassland was used as a model system to examine how grazing management, un-grazed (for six years), rabbit grazed or fully grazed (ponies 0.2ha−1, cattle 0.05ha−1 and rabbits 45ha−1), affected biodiversity and ecosystem service provision, by measuring an extensive suite of biophysical variables as proxies for ecosystem services. For ‘supporting services’, nutrient cycling was greatest in un-grazed grassland but primary productivity did not differ. The ‘provisioning service’ of food production was only provided by fully grazed grassland. For grazing effects on ‘regulating services’ total carbon (C) stock did not differ and effects on pest regulating invertebrates and pollinator abundance were variable. The potential for flood control was considered greatest in the un-grazed grassland; with faster water infiltration than in the fully grazed grassland. The ‘cultural service’ of environmental appreciation was considered higher in fully grazed grassland due to significantly greater plant species richness, more forb species and more forbs flowering than in un-grazed grassland.

Grazing increases the temperature sensitivity of soil organic matter decomposition in a temperate grassland

We tested the effects of ungulate grazing and nutrient availability on the temperature sensitivity of soil respiration (CO2) and methane (CH4) emissions in semi-natural temperate grassland. To do this, soil taken from long term grazed and ungrazed grassland was incubated at four temperatures (4, 10, 15 and 20 °C) with two levels of nutrient (NP) addition. The results showed that the variation in soil CO2 and CH4 emissions was explained by temperature and grazing, with grazing increasing the temperature sensitivity of CO2 and CH4 production by between 15 and 20 °C. This response was constrained by nutrient availability for CO2, but not CH4. These findings suggest that grazing could potentially have important impacts on the temperature sensitivity of greenhouse gas emissions in nutrient limited grasslands.

Contrast in edge vegetation structure modifies the predation risk of natural ground nests in an agricultural landscape.

Nest predation risk generally increases nearer forest-field edges in agricultural landscapes. However, few studies test whether differences in edge contrast (i.e. hard versus soft edges based on vegetation structure and height) affect edge-related predation patterns and if such patterns are related to changes in nest conspicuousness between incubation and nestling feeding. Using data on 923 nesting attempts we analyse factors influencing nest predation risk at different edge types in an agricultural landscape of a ground-cavity breeding bird species, the Northern Wheatear (Oenanthe oenanthe). As for many other bird species, nest predation is a major determinant of reproductive success in this migratory passerine. Nest predation risk was higher closer to woodland and crop field edges, but only when these were hard edges in terms of ground vegetation structure (clear contrast between tall vs short ground vegetation). No such edge effect was observed at soft edges where adjacent habitats had tall ground vegetation (crop, ungrazed grassland). This edge effect on nest predation risk was evident during the incubation stage but not the nestling feeding stage. Since wheatear nests are depredated by ground-living animals our results demonstrate: (i) that edge effects depend on edge contrast, (ii) that edge-related nest predation patterns vary across the breeding period probably resulting from changes in parental activity at the nest between the incubation and nestling feeding stage. Edge effects should be put in the context of the nest predator community as illustrated by the elevated nest predation risk at hard but not soft habitat edges when an edge is defined in terms of ground vegetation. These results thus can potentially explain previously observed variations in edge-related nest predation risk.

Monitoring of Net Primary Production in California Rangelands Using Landsat and MODIS Satellite Remote Sensing

In this study, we present results from the CASA (Carnegie-Ames-Stanford Approach) model to estimate net primary production (NPP) in grasslands under different management (ranching versus unmanaged) on the Central Coast of California. The latest model version called CASA Express has been designed to estimate monthly patterns in carbon fixation and plant biomass production using moderate spatial resolution (30 m to 250 m) satellite image data of surface vegetation characteristics. Landsat imagery with 30 m resolution was adjusted by contemporaneous Moderate Resolution Imaging Spectroradiometer (MODIS) data to calibrate the model based on previous CASA research. Results showed annual NPP predictions of between 300 - 450 grams C per square meter for coastal rangeland sites. Irrigation increased the predicted NPP carbon flux of grazed lands by 59 grams C per square meter annually compared to unmanaged grasslands. Low intensity grazing activity appeared to promote higher grass regrowth until June, compared to the ungrazed grassland sites. These modeling methods were shown to be successful in capturing the differing seasonal growing cycles of rangeland forage production across the area of individual ranch properties.

Effect of grazing on carbon stocks and assimilate partitioning in a Tibetan montane pasture revealed by 13CO2 pulse labeling

AbstractSince the late 1950s, governmental rangeland policies have changed the grazing management on the Tibetan Plateau (TP). Increasing grazing pressure and, since the 1980s, the privatization and fencing of pastures near villages has led to land degradation, whereas remote pastures have recovered from stronger overgrazing. To clarify the effect of moderate grazing on the carbon (C) cycle of the TP, we investigated differences in below‐ground C stocks and C allocation using in situ 13CO2 pulse labeling of (i) a montane Kobresia winter pasture of yaks, with moderate grazing regime and (ii) a 7‐year‐old grazing exclosure plot, both in 3440 m asl. Twenty‐seven days after the labeling, 13C incorporated into shoots did not differ between the grazed (43% of recovered 13C) and ungrazed (38%) plots. In the grazed plots, however, less C was lost by shoot respiration (17% vs. 42%), and more was translocated below‐ground (40% vs. 20%). Within the below‐ground pools, &lt;2% of 13C was incorporated into living root tissue of both land use types. In the grazed plots about twice the amount of 13C remained in soil (18%) and was mineralized to CO2 (20%) as compared to the ungrazed plots (soil 10%; CO2 9%). Despite the higher contribution of root‐derived C to CO2 efflux, total CO2 efflux did not differ between the two land use types. C stocks in the soil layers 0–5 and 5–15 cm under grazed grassland were significantly larger than in the ungrazed grassland. However, C stocks below 15 cm were not affected after 7 years without grazing. We conclude that the larger below‐ground C allocation of plants, the larger amount of recently assimilated C remaining in the soil, and less soil organic matter‐derived CO2 efflux create a positive effect of moderate grazing on soil C input and C sequestration.

Spatial and temporal variation of soil moisture in dependence of multiple environmental parameters in semi-arid grasslands

Grazing of grasslands changes soil physical and chemical properties as well as vegetation characteristics, such as vegetation cover, species composition and biomass production. In consequence, nutrient allocation and water storage in the top soil are affected. Land use and management changes alter these processes. Knowledge on the impacts of grazing management on nutrient and water fluxes is necessary because of the global importance of grasslands for carbon sequestration. Soil water in semi-arid areas is a limiting factor for matter fluxes and the intrinsic interaction between soil, vegetation and atmosphere. It is therefore desirable to understand the effects of grazing management and stocking rate on the spatial and temporal distribution of soil moisture. In the present study, we address the question how spatio-temporal soil moisture distribution on grazed and ungrazed grassland sites is affected by soil and vegetation properties. The study took place in the Xilin river catchment in Inner Mongolia (PR China). It is a semi-arid steppe environment, which is characterized by still moderate grazing compared to other regions in central Inner Mongolia. However, stocking rates have locally increased and resulted in a degradation of soils and vegetation also in the upper Xilin River basin. We used a multivariate geostatistical approach to reveal spatial dependencies between soil moisture distribution and soil or vegetation parameters. Overall, 7 soil and vegetation parameters (bulk density, sand, silt and clay content, mean weight diameter, mean carbon content of the soil, vegetation cover) and 57 soil moisture data sets were recorded on 100 gridded points on four sites subject to different grazing intensities. Increasing stocking rates accelerated the influence of soil and vegetation parameters on soil moisture. However, the correlation was rather weak, except for a site with high stocking rate where higher correlations were found. Low nugget ratios indicate spatial dependency between soil or plant parameters and soil moisture on a long-term ungrazed site. However, the effect was not found for a second ungrazed site that had been excluded from grazing for a shorter period. Furthermore the most important soil and vegetation parameters for predicting soil moisture distribution varied between different grazing intensities. Therefore, predicting soil moisture by using secondary variables requires a careful selection of the soil or vegetation parameters.

Characteristics of Momentum and Heat Transfer over Semiarid Grasslands with Different Grazing Intensities in Inner Mongolia, China

The drag coefficient (C d) and heat transfer coefficient (C h) with the bulk transfer scheme are usually used to calculate the momentum and heat fluxes in meteorological models.The aerodynamic roughness length (z 0m) and thermal roughness length (z 0h) are two crucial parameters for bulk transfer equations.To improve the meteorological models,the seasonal and interannual variations of z 0m,z 0h,coefficient kB 1,C d,and C h were investigated based on eddy covariance data over different grazed semiarid grasslands of Inner Mongolia during the growing seasons (May to September) from 2005 to 2008.For an ungrazed Leymus chinensis grassland (ungrazed since 1979),z 0m and z 0h had significant seasonal and interannual variations.z 0m was affected by the amount and distribution of rainfall.kB 1 exhibited a relatively negative variation compared with z 0h,which indicates that the seasonal variation of z 0h cannot be described by kB 1.To parameterize z 0m and z 0h,the linear regressions between ln(z 0m),ln(z 0h),and the leaf area index (LAI) were performed with R 2 =0.71 and 0.83.The monthly average kB 1 was found to decrease linearly with LAI.The four-year averaged values of C d and C h were 4.5×10 3 and 3.9×10 3,respectively.The monthly average C d only varied by 8% while the variation of C h was 18%,which reflects the different impacts of dead vegetation on momentum and heat transfer at this natural grassland.Moreover,with the removal of vegetation cover,grazing intensities reduced z 0m,z 0h,C d,and C h.

Assessment of Grazing Effect on Two Sub-Shrubs (Astragalus schottianus and Thymus sipyleus) Dominated Mountain Bozoğlan Grasslands in the Semi-Arid Central-Southern Anatolian Region of Turkey

In the central-southern Anatolian region of Turkey, vegetation of Mountain Bozoğlan grasslands has severely deteriorated, and two sub-shrubs (Astragalus schottianus and Thymus sipyleus) have become dominant species. We hypothesized that the spatial distribution of these dominant shrubs is closely associated with a long history of grazing, and these species might cause alteration of the grassland plant community. Therefore, our objectives were to determine: (1) the patterns in grassland vegetation; (2) how the dominant species contribute to these patterns; and (3) the differences of patterns between ungrazed and protected grassland areas. Plant cover in ungrazed plots was 6% higher than that of grazed plots. Total sub-shrub cover did not differ significantly, but grazing considerably reduced forbs (5% less) and grass cover (5% less). Though A. schottianus and T. sipyleus did not change between the treatments, Festuca valesiaca had greater cover in ungrazed areas (6%) than in that of grazed plots (3%). Grazing effect, soil properties and bare ground appeared to account for most of the variation on the established gradients. Even after 23 years, grazing and protection had little influence on pattern formation, and grazing have expanded dwarf-shrubs at the expense of forbs and grasses. Grazing neither increased nor decreased spatial heterogeneity, so the patterns in both treatments are similar to one another, and relatively stable assemblages of species were likely derived by high grazing pressure experienced before the exclosure establishment.

Dictyostelid cellular slime molds associated with grasslands of the central and western United States

Dictyostelid cellular slime molds (dictyostelids) associated with grassland ecosystems of the central and western United States were investigated at nine sites that included examples of the three major ecological types of grasslands (tall grass, mixed grass and short grass) generally recognized for the region. Samples of soil/humus collected from each site were examined with the Cavender method of isolating dictyostelids. For each of those six sites with well developed gallery forests present, an additional set of forest soil/humus samples was collected. A more intensive sampling effort was carried out at one site (Konza LTER) to assess the possible effects of burning and grazing on dictyostelid diversity and density. Twelve species of dictyostelids were recovered from grassland sites, whereas gallery forest sites yielded only nine species. Four cosmopolitan species (Dictyostelium giganteum, D. mucoroides, D. sphaerocephalum and Polysphondylium pallidum) were represented by the greatest densities of clones, with D. sphaerocephalum particularly common. The general pattern across all sites was that both species richness and density of dictyostelids decreased with decreasing precipitation. Samples collected from ungrazed grassland plots yielded higher numbers of both species and clones as compared to grazed plots, and the general pattern was for both values to increase as the interval between fires increased. For numbers of clones this correlation was statistically significant.

Influence of vegetation clutter on the capacity of ground foraging bats to capture prey

Summary1. The management of the habitat of insectivorous species often targets increasing the availability of arthropod prey. However, this may be hindered by lack of knowledge of the mechanisms that determine food availability for insectivores. Prey abundance is often used as a surrogate for availability, but this may be incorrect wherever habitat factors limit access to prey. Ground vegetation clutter is likely to be such a limiting factor for ground foraging insectivorous bats, and we investigated this possibility usingMyotis myotisas a model.2. We performed captivity experiments to determine how ground vegetation density affects foraging. Bats were provided with crickets hidden in sparse, medium and dense grass cover. In addition, we used bat radio tracking data, prey abundance measurements, and geographic information system (GIS) modelling to determine if clutter influences how bats select foraging areas in a Mediterranean region.3. The experiments demonstrated that ground vegetation clutter greatly reduces access to prey, affecting both capture success and time to capture. Bats detected prey in the dense vegetation, but did not attempt to capture them or did so only after a prolonged delay. Their attempts often failed, because the bats landed over prey with open wings, presumably to increase the catching surface, and the dense vegetation prevented them from reaching the ground.4. In the study area, cover types with the densest ground vegetation harboured the most prey, but clutter made access to prey byM. myotisdifficult. Corroborating this, the GIS models showed that bats avoided foraging in habitats with high prey abundance but in which availability was decreased by dense ground vegetation.5. Ungrazed grasslands reach vegetation densities that limit access to prey by ground foraging bats, as observed in the study area. However, grazing by cattle reduced clutter to levels equivalent to the sparse treatment in our captive experiments, in which bats captured prey easily.6. Synthesis and applications. Conservation of ground foraging bats may require the management of their feeding grounds, to increase or maintain prey availability, particularly near important colonies. While dense ground vegetation may promote prey density, it dramatically reduces access to prey and usage by bats; hence, this should be considered by managers. Moderate grazing can be used to reduce ground vegetation cover to levels that permit foraging by bats.

Effects of grazing on soil physical properties and soil erodibility in semiarid grassland of the Northern Loess Plateau (China)

Grazing animals provide a livelihood for farmers, but they may also produce adverse environmental effects. We investigated whether grazing leads to deterioration of soil physical properties that subsequently increases topsoil erodibility. We sampled three sites (an ungrazed grassland, a continuously grazed grassland, and a track trampled by stock) on the northern Loess Plateau of China. The bulk density, water content, proportion of stable aggregates, infiltration rate, and resistance to scouring were determined for each soil sample. The results showed that the track had the highest soil bulk density and the lowest soil water content, proportion of stable aggregates, infiltration rate, and ability to resist scouring. The ungrazed plots had the best results for these parameters, in terms of reduced erosion. Soil bulk density and the proportion of stable aggregates differed significantly with depth beneath the track. However, the effect of depth on water content, infiltration rate, and the soil resistance to scouring was not significant at any sampling site. The ability of the soil to resist scouring was negatively correlated with the soil's bulk density and positively correlated with the soil's water content, infiltration rate, and proportion of stable aggregates. Thus, soil physical properties played an important role in determining soil erodibility. Grazing and trampling by livestock therefore appear to cause deterioration of soil physical properties and to increase soil erodibility.

Integrated assessment of water framework directive nitrate reduction measures

AbstractThis article illustrates a statistical approach for deriving farm economic impacts of policy options aiming to reduce nitrate diffuse pollution. Building upon Fezzi et al. (2008), who assess the costs of Water Framework Directive‐related measures on farm accounts data, we estimate regression models allowing such costs to be predicted for any region for which land use patterns and livestock numbers are known. We derive economic impacts in terms of changes in farm gross margin for (a) reducing inorganic fertilizer application, (b) reducing livestock stocking rates, and (c) converting arable land to ungrazed grassland. A case study of the agriculturally diverse Yorkshire Derwent catchment, in the North of England, demonstrates the overall approach. In addition, for this illustration, we combine these cost estimates with prediction of the water quality changes arising from each measure, derived via an integrated hydrological model of the Derwent. This allows a comparison of cost‐effectiveness. Finally, we implement our spatially explicit approach to target the measures to specific subcatchments identified as being of particular environmental policy interest.