Effect of cultivating croplands and grazing in arid grassland habitats on the conservation of melitaeine butterflies in a mountainous area in Northern China

In the study area (Yanjiaping Village, Hebei Province, China), grazing extensity varies at different locations, small and discontinuous croplands are imbedded in some arid grassland, which are habitats for the melitaeine butterflies, Euphydryas aurinia and Melitaea phoebe. These two species of butterfilies coexist in this area, in which grazing and cultivation are the main disturbances. Grazing and cultivation have a reciprocal effect on E. aurinia, rather than M. phoebe. We observed that E. aurinia preferred to occupy patches with moderate grazing and imbedded with small and discontinuous croplands, where E. aurinia also has high population density. The percentage of E. aurinia larval groups in the ribbings was significantly higher than that of M. phoebe, whereas larvae of both species tended to increase in recent years. Our data also showed that the population density and the patch occupancy rate of both E. aurinia and M. phoebe were the highest under moderate grazing. It indicates that cultivation of small and discontinuous croplands within the patch has a significant effect on the population density of both species of melitaeine butterflies. Thus, to artificially create or maintain semi-natural habitats, complemented by moderate grazing, might be an ecological strategy to conserve melitaeine butterflies effectively. Considering the distinct impacts of cultivation and grazing on the population distribution and dynamics of the two different species, human disturbance in the mountainous area might be strategically involved in proposing conservation plans for the target species in the future.     

Effects of prairie and barrens management on butterfly faunal composition

During 1990–1997, we recorded 122 138 adult butterflies in transect surveys at 125 pine-oak barrens in northern Wisconsin and 106 tallgrass prairies in six midwestern states grouped into three prairie subregions. Before analysis, we classified the butterflies into three ecological subgroups: specialist of native herbaceous vegetation, grassland (widely occurring in native and degraded herbaceous vegetation), and generalist. We analyzed this dataset both by ecological subgroups and as total butterflies, and by relative density and species richness, to investigate how these different ways of ordinating the same dataset might affect the results. In multiple linear regressions, density and richness of total butterflies and the subgroups related significantly to many non-management factors. In comparisons of more vs. less recent burning, all significant results for most recent burning were negative. No significant negative relationships were attributed to the longest period since burning. In comparisons of burning vs. idling, all significant results in prairie favored idling, but in barrens favored burning. In comparisons of burning vs. mechanical cutting, all significant results in prairie favored cutting, but no significant differences occurred in barrens. In regressions including all management types, rotational burning (alone or combined with cutting) was significantly positive most often for generalists and never for specialists. Increasing years since last management was always negative in barrens and the southern prairie subregion but always positive in the two northern prairie subregions. Significant management patterns occurred more often in prairie than barrens, which were less fragmented. Specialists were favored by grazing in one northern prairie subregion (but disfavored in the other), haying, single wildfire (testable in barrens only), and increasing years since last treatment in one northern prairie subregion (but disfavored in barrens). Within subregion and subgroup, significant management results for density and richness never conflicted, but density had more significant results than richness. In no instances were the signs opposite when total butterflies and/or any subgroup(s) significantly related to the same management factor in the same type of regression. But what was significant for one sample was often not for another. Thus, management favorable for specialists and total butterflies did not conflict, but the subgroups had varying degrees of sensitivity, rather than opposite responses. Since the specialist (and total) butterflies did not consistently favor one management type over another among subregions, caution should be used in preserve management, to avoid overreliance on one management type over others.     

The impact of grazing management on Orthoptera abundance varies over the season in Mediterranean steppe-like grassland

As semi-natural grassland has a high level of biological diversity, understanding the effects of grazing and its variation over time is important in order to identify sustainable grazing practices. We measured temporal variation in Orthoptera abundance and spatial vegetation structure during seasonal grazing in an extensive sheep-farming system. We studied five grazed pasture areas (pre-grazing and post-grazing) and two adjacent ungrazed grasslands. We recorded the total abundance of Orthoptera and described the vegetation structure of 175 replicate plots (25 per pasture/grassland) during six field sampling sessions. We demonstrated that the impact of grazing on Orthoptera abundance is species-specific and greatly varies over the grazing season. The decrease of phytovolume is significant after 4–7 weeks of sheep grazing. Total Orthoptera abundance was higher in pre-grazed plots than in ungrazed plots, and higher in ungrazed plots than in post-grazed plots. These differences were particularly high during the peak of adult abundance. No difference in species richness was observed between grazing intensities. Total Orthoptera abundance positively correlated to phytovolume only when grazing pressure was high. However, the relationship between abundance and phytovolume differed between species. Extensive grazing by sheep tends to homogenize spatial vegetation structure and to temporarily reduce total Orthoptera abundance at pasture scale. However, rotational grazing allows spatial and temporal heterogeneity in vegetation structure to be maintained at farm scale, heterogeneity that is beneficial for Orthoptera. In contrast, absence of grazing has a negative impact on Orthoptera abundance as it favours the accumulation of litter, which is detrimental for a high proportion of xerothermophilic Orthoptera associated with bare ground and short vegetation.     

Long‐term stock grazing management in Travelling Stock Reserves and influence on conservation values

We examined the nature of long‐term grazing management implemented in 51 Travelling Stock Reserves (TSRs) in the Albury region, and investigated potential relationships between grazing intensity and conservation values. In general, grazing intensities in most TSRs decreased over the 22 year study period. Most TSRs were lightly grazed (density = 1.1 DSE/ha/year), and stocked for <2 months per year, but some were much more heavily grazed. Spring grazing intensity was found to be negatively associated with TSR conservation values. Our results suggest that grazing management aims to achieve both production and conservation outcomes are not necessarily exclusive to each other.     

Spider biodiversity potential of an ungrazed and a grazed inland salt meadow in the National Park 'Neusiedler See-Seewinkel' (Austria): implications for management (Arachnida: Araneae)

To assess the biodiversity potential of an ungrazed and a grazed inland salt meadow in the Seewinkel (Eastern Austria), spider assemblages were recorded by pitfall trapping for 1 year. Both species assemblages consisted, to a large extent, of rare species of conservation interest. The species assemblage of the grazed site was dominated by Pardosa agrestis, but highly specific halotopobiontic species also occurred in higher numbers. Halotolerant species were also present in the ungrazed meadow, but their individual number was much lower. The species composition of this site reflects the more balanced microclimatical situation of the high sward. Comparison of the two assemblages with 207 other meadow spider assemblages of Central Europe shows a separated position, especially of the grazed site assemblage. High similarities with assemblages of meadows with a similar vegetation structure indicate a high importance of management. Considering the high proportion of rare species on both sites, the best management of the salt meadow and pan shores of the Seewinkel should combine areas of light grazing with ungrazed areas. However, the proportion of these parts and the intensity of grazing still remains to be determined by quantitative experiments.     

放牧和刈割对内蒙古典型草原土壤可提取碳和氮的影响

依托内蒙古典型草原的长期野外放牧控制试验,探讨了放牧和刈割对土壤有机碳、全氮、可提取碳和氮、微生物生物量碳和氮的影响.结果表明: 放牧使可提取有机碳降低11.4%～37.1%,而刈割使可提取有机碳升高5.8%.放牧和刈割分别使可提取氮升高10%～340%和10%～240%.放牧强度不高于6.0 sheep·hm^-2的条件下有利于维持甚至增加微生物生物量碳,而重度放牧(7.5和9.0 sheep·hm^-2)则减少微生物生物量碳.刈割处理下微生物生物量碳和氮分别升高31.0%和9.8%.通径分析表明,放牧处理下微生物生物量碳的主要影响因素是有机碳、可提取全氮和全氮,其中直接影响因素是有机碳和可提取全氮;微生物生物量氮的主要影响因素是土壤pH、可提取有机碳、有机碳和可提取全氮,其中直接影响因素是有机碳和可提取全氮.刈割及轻度和中度放牧有利于维持或改善土壤功能,重度放牧将引起土壤退化.     

黄土高原半干旱区退化草地恢复与利用过程研究

草地退化表现为土壤和植被遭到彻底破坏,草地演替过程受到强烈抑制.实验采用长期(30年)封禁措施,定位监测退化草地从次生半裸地演变为近似原生植被(进展演替)的变化过程.结果表明,随着封禁时间的变化,退化草地恢复演替经历了4个阶段,群落盖度、植株密度、物种丰富度和多样性指数、地上生物量和地下生物量在草地群落恢复过程中逐渐增加,其特征变化出现的峰值均在封禁第20年(地下生物量峰值在第15年),其中地上生物量最高达520.5 g/m2;直到封禁的第20~25年,以本氏针茅为建群种的草原群落衰败退化现象明显,而大针茅种群密度剧增;在封禁的第26年以上以大针茅为优势的群落生长较为稳定,从目前群落演替进程看,大针茅有替代本氏针茅的趋势.另外,在草原沟道两侧以斑块状聚集分布有中旱生灌木,群落的演替进入了一个新的阶段.随着封禁时间的延续,退化草地从自然封禁恢复的0~26年,通过侵入-竞争-扩散-定居的几个演替阶段,目前形成以大针茅为建群种相对稳定的"亚顶级".虽然草地生物量有一定下降,但草地质量提高,物种多样性丰富,促进草地的进展演替.草地植物群落主要由禾本科、豆科和菊科组成;多年生植物、C3和旱生物种可以作为草地演替过程和植被恢复的指示物种.长期封育对草地物种更新和生态系统稳定性有负面影响,因此,合理的封育时间是草地生态恢复中非常重要的一个因素.本研究提出,在黄土区退化草地封育10~15年后可以开始进行合理的利用,例如通过两年一次刈割和轻度放牧(2只羊/hm2).本研究可为干旱区、半干旱区相似的退化草地恢复提供理论依据.     

The influence of nematodes on below-ground processes in grassland ecosystems

This review summarises recent information on beneficial roles that soil nematodes play in the cycling of carbon and other plant nutrients in grassland ecosystems. In particular, we focus on the role of the two dominant functional groups of nematodes, namely the microbial- and root-feeders, and how their activities may enhance soil ecosystem-level processes of nutrient cycling and, ultimately, plant productivity in managed and unmanaged grassland ecosystems. We report recent experiments which show that low amounts of root herbivory by nematodes can increase the allocation of photoassimilate carbon to roots, leading to increased root exudation and microbial activity in the rhizosphere. The effects of these interactions on soil nutrient cycling and plant productivity are discussed. Evidence is presented to show that the feeding activities of microbial-feeding nematodes can enhance nutrient mineralization and plant nutrient uptake in grasslands, but that these responses are highly species-specific and appear to be strongly regulated by higher trophic groups of fauna (top-down regulation). We recommend that future studies of the roles of nematodes in grasslands ecosystems should consider these more complex trophic interactions and also the effects of species diversity of nematodes on soil ecosystem-level processes. This revised version was published online in June 2006 with corrections to the Cover Date.     

Influence of livestock grazing on meadow pipit foraging behaviour in upland grassland

Changes in grazing management are believed to be responsible for declines in populations of birds breeding in grassland over the last decades. The relationships between grazing management regimes, vegetation structure and composition and the availability of invertebrate food resources to passerine birds remain poorly understood. In this study, we investigated the foraging site selection of meadow pipits (Anthus pratensis L.) breeding in high intensity sheep-grazed plots or low intensity mixed (i.e. sheep and cattle)-grazed plots. We sampled above-ground invertebrates, measured vegetation height and density and conducted a vegetation survey in areas where meadow pipits were observed to forage and areas that were randomly selected. Birds foraged in areas with a lower vegetation height and density and in areas containing a lower proportion of the dominant, tussock-forming grass species Molinia caerulea. They did not forage in areas with a total higher invertebrate biomass but at areas with preferred vegetation characteristics invertebrate biomass tended to be higher in foraging sites than random sites. The foraging distance of meadow pipits was higher in the intensively grazed plots. Our findings support the hypothesis that resource-independent factors such as food accessibility and forager mobility may determine patch selection and are of more importance as selection criteria than food abundance per se. Food accessibility seems to become an even more important selection criterion under high grazing intensity, where prey abundance and size decrease. In our upland grazing system, a low intensity, mixed grazing regime seems to provide a more suitable combination of sward height, plant diversity, structural heterogeneity and food supply for meadow pipit foraging activity compared to a more intensive grazing regime dominated by sheep.     

A model of nitrogen flows in grassland

Abstract. The model comprises three submodels, which together give an integrated picture of nitrogen pools and fluxes in grassland under grazing or cutting. The first submodel represents the interaction of the grazing animal with the sward through intake and the production of excreta: the second is concerned with the growth of the vegetative grass crop and its response to light, temperature and nitrogen; these two submodels are interfaced with a submodel of soil carbon and nitrogen pools and processes, including dead shoot and root material, dead and live soil organic matter, and three pools representing mineral nitrogen. No account is taken of water, which is assumed to be non-limiting, or the possible effects of soil pH and soil aeration. The model is used to simulate a range of management strategies as applied to stocking density and fertilizer application, examining both steady-state and non-steady-state conditions. The model highlights the long time scales associated with grassland systems, the role of the grazing animal in modifying carbon and nitrogen flows, and the importance of soil conditions to grassland productivity and fertilizer response. The productivity of grazed swards may be greater or less than that of cut swards depending on stocking density and fertilizer application, although nitrogen recovery (as calculated here) is always lower in grazed swards. The model is able to stimulate mineralization and immobilization, and place these in the context of plant processes and the grazing animal.     

Late Quaternary vegetation, biodiversity and fire dynamics on the southern Brazilian highland and their implication for conservation and management of modern Araucaria forest and grassland ecosystems

Palaeoecological background information is needed for management and conservation of the highly diverse mosaic of Araucaria forest and Campos (grassland) in southern Brazil. Questions on the origin of Araucaria forest and grasslands; its development, dynamic and stability; its response to environmental change such as climate; and the role of human impact are essential. Further questions on its natural stage of vegetation or its alteration by pre- and post-Columbian anthropogenic activity are also important. To answer these questions, palaeoecological and palaeoenvironmental data based on pollen, charcoal and multivariate data analysis of radiocarbon dated sedimentary archives from southern Brazil are used to provide an insight into past vegetation changes, which allows us to improve our understanding of the modern vegetation and to develop conservation and management strategies for the strongly affected ecosystems in southern Brazil.     

Holocene vertebrate fossils aid the management and restoration of Australian ecosystems

European‐settlement‐related impacts over the past 200 years pose many challenges for the conservation and restoration of Australia's ecosystems. Landscape modification, associated habitat loss and the introduction of exotic species have caused the extinction and mainland extirpation of numerous vertebrates. This process happened so quickly that many species became locally or functionally extinct before their presence was documented. A growing body of research on Holocene fossil accumulations is providing insights into the composition and biogeography of Australian ecosystems prior to European settlement. This review explores the similarities between palaeo‐ and neo‐ecology and how Holocene (last 10,000 years) assemblages can be used by neo‐ecologists, conservation managers and policy makers to identify and fill gaps in knowledge and contribute to the management and restoration of Australia's degraded ecosystems.     

Simulated effects of precipitation and nitrogen on Serengeti grassland productivity

In the Serengeti National Park, Tanzania, precipitation and soil nitrogen vary greatly between northwestern tallgrass areas and southeastern shortgrass areas, with the tallgrass having higher total precipitation and lower soil fertility. We used a model of grassland productivity, carbon/nitrogen cycling, and abiotic factors to test the hypothesis that tallgrass productivity is limited primarily by nitrogen availability while shortgrass productivity is limited by water. Under observed grazing intensities and ungrazed conditions, precipitation exerted primary control over grassland productivity for both regions, with differences in soil texture mediating soil water availability to the grasses. Mineral nitrogen availability interacted with water availability to influence productivity at precipitation levels 130% of the mean. Nitrogen mineralization and precipitation were positively related for each grassland type, however, nitrification varied both between grassland types and between grazed and ungrazed conditions. Combined mineralization and nitrification could not maintain soil mineral nitrogen levels in the face of plant nitrogen uptake stimulated by increased precipitation, thus providing the mechanism by which nitrogen becomes a secondary limiting factor for both grasslands. Model experiments indicated that the pattern of primary limitation by precipitation and secondary limitation by nitrogen was robust to model assumptions concerning ungulate deposition of urine and dung nitrogen to the soil.