Response of ants to grazing disturbance at the central Monte Desert of Argentina: community descriptors and functional group scheme

Livestock ranching is one of the main productive activities in arid regions of the world.Grazing produces changes in animal as well as plant communities(e.g.richness,abundance and species dominance relationships).Ants are good biological indicators due to the environmental fidelity of some of their community parameters.We described the functional structure of the ant community in the central Monte of Mendoza,Argentina,and examined the effect of grazing using richness,diversity and the functional group scheme.We used pitfall traps to sample ants at a reserve with 30-year cattle exclusion and at an adjacent ranch.Eleven of the 27 recorded species showed significant differences in their abundance and two species were absent at the ranch.While richness and diversity did not reflect these differences,functional groups did.Hot Climate Specialists were more abundant at the ranch while Cryptic Species and Generalized Myrmicinae increased at the reserve.This study supports the utility of the functional group scheme to study the effects of grazing disturbance in ant communities of arid regions.

Effect of Different Stocking Rates on Deyeuxia angustifolia Bog Meadow in Sanjiang Plain of China

This paper investigated the effects of cattle grazing on herbage production and its nutrient and soil characteristics over the grazing season. The grazing experiment was conducted on Deyeuxia angustifolia Bog meadow grassland established in 2010 in Sanjiang Plain. Four grazing treatments were light grazing （LG）, moderate grazing （MG）, heavy grazing （HG）, and a non-grazed exclosure （CK） with corresponding stocking rates of 0.6, 1.0, 1.4, and 0 AU·hm2. month-1, selected as three replications. And then found out the optimum carrying capacity after analyzed the nutrition balance between livestock and grassland. Heavy grazing led to a decline in grassland productivity and soil nutrients. The SOM and the TN content in the soil layer of 0-10 cm were much higher than that in the soil layer of 20-30 cm. More attention should be paid to the nutrient changes in the soil layer of 20-30 cm. Currently, studies showed that the reliable carrying capacity in this type of grassland was 1.0 AU·hm-2. month-l. Inclusion of rangeland health monitoring and optimum stocking rate into grassland management model could facilitate the sustainable development of the grassland.

Soil Macrofaunal Communities are Heterogeneous in Heathlands with Different Grazing Intensity

Moderate grazing by cattle increases the heterogeneity of soil and vegetation. This has been suggested as an ecologically sustainable mean of managing natural environments endangered by tree encroachment, such as heathlands. Our study was performed to test the impact of grazing intensity on soil macroinvertebrate communities in heterogeneous landscapes in a private property eligible to the Natura 2000 European Network of Special Protection Areas within the Brenne Natural Regional Park （Indre, ~rance）. We sampled macroinvertebrates along a broken line crossing 5 different land-use types, from pasture to pine forest, passing through a besom heath （Erica scoparia） heathland at 3 levels of cattle pressure. We hypothesized that： i） litter-dwelling （mostly arthropods and mollusks） and soil-dwelling macroinvertebrates （mostly earthworms） would respond in an opposite manner to various grazing intensities, and ii） intermediate cattle pressure （pastured heath） would increase soil and community heterogeneity. The results supported the first hypothesis, which was explained by land-use impacts mediated by soil properties. However, our results supported only partly the second hypothesis since maximum dissimilarity （whether in the composition of soil macroinvertebrate communities or in soil features） was observed in only one out of the two pastured heaths where cattle pressure was intermediate.

A comparison of the nutritive value of perennial ryegrass,perennial ryegrass and white clover and multispecies-based farmlet systems

Background:Limited information is available regarding the nutritive value and structural characteristics of multispecies swards when rotationally grazed.Methods:Three farmlet types were investigated in terms of their nutritive value:Lolium perenne(LP);L.perenne+Trifolium repens(LP+TR);and a multispecies sward containing grasses,legumes and herbs(MSS).Farmlets were stocked with beef steers(2.5 livestock units ha−1),grazed on a 1 ha scale to 6 cm(MSS)and 4 cm(LP and LP+TR)residuals.Results:A greater ash concentration was found in MSS than LP(84 vs.75 g kg−1 DM).Both LP+TR and MSS had higher crude protein and lower neutral detergent fibre concentrations than LP.The relative ranking of water soluble carbohydrate and dry matter(DM)concentration was LP>LP+TR>MSS.Despite the leaf component of the LP farmlet contributing more to herbage DM,the organic matter digestibilities of the swards were similar.Conclusions:The MSS and LP+TR farmlets achieved similar forage quality under intensive grazing to LP.However,it is worth noting that MSS had a higher concentration of acid detergent lignin,which can negatively impact digestibility.Further investigation is needed to determine optimal grazing management practices that can minimise the effects of higher lignin concentration on digestibility in multispecies swards.

Regional-scale relationship among biological soil crusts,invasive annual grasses,and disturbance

Introduction:Sagebrush ecosystems in western North America are being replaced by the invasion of annual grasses,particularly Bromus tectorum.In experimental situations and in localized landscapes,prior studies have documented that biological soil crusts(biocrusts)can reduce annual grass presence and that biocrusts are highly vulnerable to physical disturbance.Practical conservation would benefit from verification of these patterms at scales that matter to local economies.This study tests if these patterns appear at a regional scale.Methods:A previously collected data set of vegetation provided sampling of biocrust cover across the Great Basin within the state of Nevada,USA Data were analyzed with non-par ametric methods including odds ratios and generalized aditive models(GAM).Results:From a data set of 608 vegetation plots within the Great Basin ecoregion,proportion of plots with high annual grass cover differed between sites with high versus low biocrust cover(p=0.0015).A negative relationship between annual grass cover and biocrust cover was confirmed with GAM(p=0.009).For a model of biocrust cover,cattle disturbance was found to be an explanatory variable(p<0.00001).Conclusions:The patterns do appear at the regional scale,with high levels of cattle activity corresponding to low cover of biocrusts,and low cover of biocrusts corresponding to high cover of annual grasses.