The golf ball method for rapid assessment of grassland structure

A key task for native grassland managers is to assess when biomass reduction is necessary to maintain plant and animal diversity. This requires managers to monitor grassland structure. Parks Victoria and La Trobe University developed a method for rapid assessment of grassland structure using golf balls. Baker‐Gabb et al. (Ecological Management & Restoration, 17, 2016, p235) provide an example of where the method has been used to manage grassland structure to favour an endangered bird, the Plains‐wanderer (Pedionomus torquatus). In this study, we provide further critical analysis of the method using three data sets collected across different parts of Victoria that relate golf ball scores to various habitat attributes. We demonstrate how the golf ball score provides a good surrogate for key aspects of grassland structure. We show that the method does not provide a reliable surrogate for above‐ground biomass or vegetation cover, although we discuss how biomass and cover are not particularly good indicators of grassland structure. We argue that elements of grassland structure may be better correlated with desired conservation outcomes (e.g. plant species diversity or the presence of a particular species) than biomass or cover alone. We discuss examples of how the golf ball method has been used, and how it can be improved. The method will be particularly useful where a link can be demonstrated between golf ball scores and desired conservation outcomes, such as in the case of the Plains‐wanderer.     

A Plains‐wanderer (Pedionomidae) that did not wander plains: a new species from the Oligocene of South Australia

The remarkable fauna of Australia evolved in isolation from other landmasses for millions of years, yet understanding the evolutionary history of endemic avian lineages on the continent is confounded by the ability of birds to disperse over geographical barriers even after vicariance events. The Plains‐wanderer Pedionomus torquatus (Charadriiformes) is an enigmatic, predominantly sedentary, quail‐like bird that occurs exclusively in sparse native grasslands of southeastern Australia. It is the only known species of its family (Pedionomidae), and its closest relatives are the South American seedsnipes (Thinocoridae). Here we describe a further representative of this lineage, Oligonomus milleri gen. et sp. nov., from the Late Oligocene of South Australia (26–24 Ma), which pre‐dates the earliest record of P. torquatus by c. 22 Ma and attests to the presence of this lineage during Australia's period of isolation (50–15 Ma). Based on the morphology of the coracoid and the palynological record, we propose that O. milleri and P. torquatus were ecologically disparate taxa and that, similar to coeval marsupials, O. milleri inhabited well‐wooded habitats, suggesting that the preference for grassland in the extant P. torquatus and thinocorids is likely to be convergent and not ancestral. The speciation event leading to the evolution of the extant Plains‐wanderer was probably triggered by the spread of grasslands across Australia in the Late Miocene–Pliocene, which this record pre‐dates. The presence of a pedionomid in the Late Oligocene of Australia strengthens the hypothesis of a Gondwanan divergence of the lineages giving rise to Thinocoridae and Pedionomidae.     

Disturbance,microclimate and historical habitat connectivity determine the population performance of the threatened grassland specialist Carex caryophyllea in remnant grasslands

Many grassland specialist plant populations in Europe have become restricted to remnant habitats. The performance of these populations depends on both species‐specific traits and local and landscape level aspects of habitat quality. Understanding which specific local or landscape level conditions determine the performance of grassland species populations in remnant habitats would help design the restoration of the habitats and to detect the conditions that favour the long‐term persistence of grassland species in them. Such information is especially needed in urbanised landscapes, where remnant habitats engulfed by urban land use types may experience increased erosion, higher temperatures and invasion by alien species. This study investigates the population performance determinants of Carex caryophyllea (VU), a grassland specialist, in 43 remnant grasslands in an urban‐rural gradient in Finland. The population performance was assessed with metrics of persistence, establishment and reproduction, and related to environmental conditions with generalized additive models and redundancy analysis. The most important positive determinants for the performance of C. caryophyllea populations were disturbance through management or ground erosion, a warm microclimate, large habitat area and high historical connectivity to suitable grassland habitats. Present connectivity to other C. caryophyllea populations had a weak and near‐significant positive relationship with population performance. Urbanisation of the surrounding landscape correlated with population performance as well, possibly due to the high historical cover of grasslands in presently urbanised landscapes. The results imply that the most effective restoration method of remnant C. caryophyllea populations would be reinstating disturbance regimes in overgrown habitats with warm microclimates close to suitable habitats and other existing populations, whether urban or rural. This would counteract the species future decline due to possible extinction debts and help the species persist in the study area in the long term.     

Abundance,territory sizes,and pairing success of male Henslow's Sparrows in restored warm‐ and cool‐season grasslands

Henslow's Sparrows (Ammodramus henslowii) are known to breed in restored grasslands consisting of either warm‐ or cool‐season grasses, but additional information is needed concerning their breeding biology in these two types of grasslands. We compared the abundance, territory sizes, and pairing success of male Henslow's Sparrows in grasslands in west‐central Missouri in 2010 and 2011 using a paired‐treatment design, where warm‐ and cool‐season grasslands were located in close proximity. Selection indices indicated no apparent preference by male Henslow's Sparrows for either type of grassland, and the territory sizes and pairing success of males in cool‐ and warm‐season grasslands did not differ. In addition, we found no significant differences in habitat structure between these grassland types. Thus, our results suggest that the warm‐ and cool‐season grasslands in our study provided suitable habitat for Henslow's Sparrows. Other investigators have drawn similar conclusions for Henslow's Sparrows and for grassland birds in general, with the structural characteristics and, for some species, the size of grasslands being more important for grassland birds than plant species composition.     

Direct and indirect effects of land‐use intensification on ant communities in temperate grasslands

Land‐use intensification is a major driver of local species extinction and homogenization. Temperate grasslands, managed at low intensities over centuries harbored a high species diversity, which is increasingly threatened by the management intensification over the last decades. This includes key taxa like ants. However, the underlying mechanisms leading to a decrease in ant abundance and species richness as well as changes in functional community composition are not well understood. We sampled ants on 110 grassland plots in three regions in Germany. The sampled grasslands are used as meadows or pastures, being mown, grazed or fertilized at different intensities. We analyzed the effect of the different aspects of land use on ant species richness, functional trait spaces, and community composition by using a multimodel inference approach and structural equation models. Overall, we found 31 ant species belonging to 8 genera, mostly open habitat specialists. Ant species richness, functional trait space of communities, and abundance of nests decreased with increasing land‐use intensity. The land‐use practice most harmful to ants was mowing, followed by heavy grazing by cattle. Fertilization did not strongly affect ant species richness. Grazing by sheep increased the ant species richness. The effect of mowing differed between species and was strongly negative for Formica species while Myrmica and common Lasius species were less affected. Rare species occurred mainly in plots managed at low intensity. Our results show that mowing less often or later in the season would retain a higher ant species richness—similarly to most other grassland taxa. The transformation from (sheep) pastures to intensively managed meadows and especially mowing directly affects ants via the destruction of nests and indirectly via loss of grassland heterogeneity (reduced plant species richness) and increased soil moisture by shading of fast‐growing plant species.     

Structure and composition of grassland habitats used by wintering Smith's Longspurs: the importance of native grasses

ABSTRACT Smith's Longspurs (Calcarius pictus) are a species of concern in North America because of their limited range and apparent low population size. To better understand winter habitat needs and guide management of this species, we examined habitat associations of Smith's Longspurs in eastern Arkansas by comparing grassland patches where Smith's Longspurs flushed to randomly located patches in the same area. Smith's Longspurs were found in sparse grassland patches of relatively low height adjacent to airport runways where the native grass prairie three‐awn (Aristida oligantha) dominated ground cover and vertical structure. Smith's Longspurs were not found in vegetation plots dominated by non‐native Bermuda grass (Cynodon dactylon). Prairie three‐awn grass may provide concealment from predators and their seeds may be an important food source. Occurrence of Smith's Longspurs was also correlated with less litter, perhaps because deeper litter could make walking and searching for seeds more difficult. Availability of suitable habitat for Smith's Longspurs along airport runways may be declining due to natural succession of grassland habitat in the absence of disturbance and recent changes in management that favor Bermuda grass. Conversion and degradation of native prairie has resulted in the decline in abundance and distribution of Chestnut‐collared Longspurs (C. ornatus) and McCown's Longspurs (Rhynchophanes mccownii). Our findings suggest that conversion of native grasslands to non‐native grasslands results in loss and degradation of habitat for wintering populations of Smith's Longspurs.     

Short-term effects of nitrogen enrichment, litter removal and cutting on a Mediterranean grassland

Semi-natural grassland communities are of great interest in conservation because of their high species richness. These communities are being threatened by both land abandonment and nitrogen eutrophication, and their continued existence will depend upon correct management. However, there is a distinct lack of studies of the ecological mechanisms that regulate species diversity and productivity in Mediterranean grasslands. We have conducted a 3-year field experiment in a species-poor grassland in central Italy to investigate the effects of nitrogen fertilization coupled with removal of plant litter and artificial cutting on species diversity and community productivity. Vegetation cutting reduced living biomass but increased species diversity. In fact, cutting had positive effects on the cover of almost all of the annual and biennial species, while it had a negative effect on the dominant perennial grasses Brachypodium rupestre and Dactylis glomerata. Litter removal had similar effects to cutting, although it was far less effective in increasing species diversity. In contrast, nitrogen enrichment strongly increased the living biomass while maintaining very low species diversity. Our results have indicated that semi-natural Mediterranean grasslands need specific management regimes for maintenance and restoration of species diversity. In the management of these grasslands, attention should be paid to the potential threat from nitrogen enrichment, especially when coupled with land abandonment.     

新疆草地净初级生产力(NPP)空间分布格局及其对气候变化的响应

分析植被物候与净初级生产力对气候变化的响应一直是研究全球变化的核心内容之一。新疆草地生态系统极为脆弱,对气候和环境变化的影响十分敏感,在新疆地区开展草地物候和净初级生产力及其对气候变化的响应有着独特的意义。基于遥感数据和野外台站实测数据,利用CASA模型模拟了新疆草地植被净初级生产力(NPP),阐述了2001—2014年新疆地区草地的NPP的空间格局及与气象因子的关系。(1)通过实测生物量精度检验表明,CASA模型基本可以反映新疆地区草地植被NPP。(2)2001—2014年新疆草地NPP平均值为102.49 gC m~(-2) a~(-1)。不同草地类型的NPPA存在明显差异。其中,山地草甸平均NPP最高,达到252.37 gC m~(-2) a~(-1);温性草甸草原次之,为204.93 gC m~(-2) a~(-1)。高寒荒漠和温性荒漠的平均NPP最低,分别为43.94 gC m~(-2) a~(-1),53.11 gC m~(-2) a~(-1)。(3)新疆NPP的空间分布格局具有如下特点:山区NPP高于盆地NPP,北疆NPP高于南疆NPP;(4)降水能够促进新疆草地NPP增加,其中,夏季和秋季的降水对草地NPP的影响最为明显,温度对新疆地区草地NPP影响不大。降雨可以促进新疆草原NPP的增加。特别是在降水量较少但温度较高的草原,如温带荒漠草原、温带草原沙漠、温带沙漠、低地草甸等,年降水量和夏秋降水量对草地NPP有显著影响。温度对新疆草地NPP的影响不大。通过对新疆草地空间格局的分析,研究了草地NPP对气候变化的响应,为合理规划新疆草地的生产和利用,以及草地生态系统的健康发展和应对气候变化提供决策依据。     

Conservation and restoration of Nardus grasslands in the Swiss northern Alps

Aim: Species‐rich Nardus grasslands are high nature‐value habitats. In Switzerland, many of these grasslands are degraded even though they have been under protection since the 1980s. Degradation shows two divergent trends: Nardus grasslands are either dominated by Nardus stricta or by eutrophic plants, both trends leading to the disappearance of typical Nardus grassland species. With this study, we aim to identify the factors that could be adjusted to conserve the integrity of this habitat. Location: Bernese Alps, Switzerland. Methods: In 2016, we investigated the underlying causes of this degradation process by assessing vegetation composition in 48 Nardus grasslands located in the Swiss northern Alps of canton Bern and linking it to soil, management and environmental variables. To explore the effect of the degradation on higher trophic levels, orthopteran species richness and densities were assessed. Results: Results show that Nardus meadows (mown) are rarely degraded compared to Nardus pastures (grazed). Within pastures, eutrophic plants are most abundant on small pastures with low soil carbon/nitrogen ratio, indicating high nutrient availability. Nardus stricta dominance is most problematic on north‐exposed slopes and in summer pastures. A plausible driver of both degradation trends is the grazing management regime: within small pastures at low elevation where the grazing periods are short but intense, soil carbon/nitrogen ratio is low because of high dung deposition, thus the eutrophic species become dominant. Contrastingly, on large summer pastures with low‐intensity and long‐term grazing, N. stricta becomes dominant due to selective grazing. Both degradation trends show a negative impact on the orthopteran density. Conclusion: Species‐rich Nardus grasslands are a precious alpine habitat for specialised plant species and orthopterans. With an extensive mowing regime or a more controlled grazing regime that homogenises intensity in time and space, species‐rich Nardus grasslands can be conserved in Switzerland.     

Substrate controls growth rates of the woody pioneer Leptospermum lanigerum colonizing montane grasslands in northern Tasmania

Woody encroachment into grasslands is occurring across the world and is of concern to land managers. Studies of forest–grassland boundaries have informed models describing factors that govern tree establishment and the maintenance and origin of grassland ecosystems. Central to these models is the role of fire relative to ‘bottom up’ resources such as soil and the geological substrate in determining the extent of grassland and forest in the landscape. The view that human lit fires have shaped vegetation across the Australian continent has been bolstered by early 19th century observations of Aboriginal‐set fires in Tasmanian montane grasslands and the documented encroachment of trees into these grasslands in the 20th century. We examined the pattern of lateral encroachment of woolly tea‐tree (Leptospermum lanigerum (Sol. ex Aiton) Sm.) into these grasslands and used tree ring chronologies to investigate (i) past fire activity and (ii) how the geological substrate mediates growth rates of L. lanigerum. Changes in fire regimes inferred from L. lanigerum recruitment were corroborated by historical records. Encroachment (and increases in woody cover) of trees into grasslands was highest on granitic substances, although L. lanigerum growth rates were highest on basalt substrates, followed by conglomerate, granite and Mathinna sediments. Frequent burning up to the 1980s may have stymied the encroachment of trees in grasslands underlain by basalt. Growth rates decreased with increasing distance from the forest edge. This may be due to incremental changes in soil resources, grass competition and/or microclimate. The dynamics between grasslands and forests in montane Tasmania are consistent with tree growth–fire interaction models that highlight the interplay of edaphic factors, growth rates and fire history. Such complexity cautions against generalizations concerning the direct effects of landscape fire in shaping vegetation distribution across Australia.     

Fine-scale habitat associations of Oklahoma's longspurs

Overwintering is a key demographic stage for migratory birds but remains poorly understood, especially among multiple declining grassland bird species. The non-breeding ranges all 4 species of longspur (i.e., chestnut-collared [Calcarius ornatus], Smith's [C. pictus], Lapland [C. lapponicus], thick-billed [Rhynchophanes mccownii]) overlap in Oklahoma and the Texas Panhandle, USA, making this region ideal to study their wintering ecology. We evaluated the relationship between wintering longspur occurrence and fine-scale habitat characteristics using a combination of standardized bird surveys and vegetation plot sampling. Our study encompassed large, representative tracts of 3 prairie ecosystems (i.e., shortgrass, mixed-grass, and tallgrass prairies) that intersect within the Southern Great Plains, during winters of 2018–2019 and 2019–2020. Using randomization tests and classification trees, we characterized longspur habitats and compared these associations across the 3 prairie ecosystems. Fine-scale winter habitats (horizontal structure, vertical structure, and species compositions) varied among all 4 longspur species, varied at very fine scales, and differed between grassland types. Our findings can be applied to the management of grasslands such as decreasing vegetation height in mixed-grass prairies for chestnut-collared longspurs or removing woody vegetation in shortgrass prairies for thick-billed longspurs to help develop full-life cycle conservation for longspurs, which have experienced population declines.     

The role of vegetation–microclimate feedback in promoting shrub encroachment in the northern Chihuahuan desert

Many arid and semi‐arid landscapes around the world are affected by a shift from grassland to shrubland vegetation, presumably induced by climate warming, increasing atmospheric CO₂ concentrations, and/or changing land use. This major change in vegetation cover is likely sustained by positive feedbacks with the physical environment. Recent research has focused on a feedback with microclimate, whereby cold intolerant shrubs increase the minimum nocturnal temperatures in their surroundings. Despite the rich literature on the impact of land cover change on local climate conditions, changes in microclimate resulting from shrub expansion into desert grasslands have remained poorly investigated. It is unclear to what extent such a feedback can affect the maximum extent of shrub expansion and the configuration of a stable encroachment front. Here, we focus on the case of the northern Chihuahuan desert, where creosotebush (Larrea tridentata) has been replacing grasslands over the past 100–150 years. We use a process‐based coupled atmosphere‐vegetation model to investigate the role of this feedback in sustaining shrub encroachment in the region. Simulations indicate that the feedback allows juvenile shrubs to establish in the grassland during average years and, once established, reduce their vulnerability to freeze‐induced mortality by creating a warmer microclimate. Such a feedback is crucial in extreme cold winters as it may reduce shrub mortality. We identify the existence of a critical zone in the surroundings of the encroachment front, in which vegetation dynamics are bistable: in this zone, vegetation can be stable both as grassland and as shrubland. The existence of these alternative stable states explains why in most cases the shift from grass to shrub cover is found to be abrupt and often difficult to revert.     

Using Grazing to Manage Herbaceous Structure for a Heterogeneity-Dependent Bird

Grazing management recommendations often sacrifice the intrinsic heterogeneity of grasslands by prescribing uniform grazing distributions through smaller pastures, increased stocking densities, and reduced grazing periods. The lack of patch-burn grazing in semi-arid landscapes of the western Great Plains in North America requires alternative grazing management strategies to create and maintain heterogeneity of habitat structure (e.g., animal unit distribution, pasture configuration), but knowledge of their effects on grassland fauna is limited. The lesser prairie-chicken (Tympanuchus pallidicinctus), an imperiled, grassland-obligate, native to the southern Great Plains, is an excellent candidate for investigating effects of heterogeneity-based grazing management strategies because it requires diverse microhabitats among life-history stages in a semi-arid landscape. We evaluated influences of heterogeneity-based grazing management strategies on vegetation structure, habitat selection, and nest and adult survival of lesser prairie-chickens in western Kansas, USA. We captured and monitored 116 female lesser prairie-chickens marked with very high frequency (VHF) or global positioning system (GPS) transmitters and collected landscape-scale vegetation and grazing data during 2013–2015. Vegetation structure heterogeneity increased at stocking densities ≤0.26 animal units/ha, where use by nonbreeding female lesser prairie-chickens also increased. Probability of use for nonbreeding lesser prairie-chickens peaked at values of cattle forage use values near 37% and steadily decreased with use ≥40%. Probability of use was positively affected by increasing pasture area. A quadratic relationship existed between growing season deferment and probability of use. We found that 70% of nests were located in grazing units in which grazing pressure was <0.8 animal unit months/ha. Daily nest survival was negatively correlated with grazing pressure. We found no relationship between adult survival and grazing management strategies. Conservation in grasslands expressing flora community composition appropriate for lesser prairie-chickens can maintain appropriate habitat structure heterogeneity through the use of low to moderate stocking densities (<0.26 animal units/ha), greater pasture areas, and site-appropriate deferment periods. Alternative grazing management strategies (e.g., rest-rotation, season-long rest) may be appropriate in grasslands requiring greater heterogeneity or during intensive drought. Grazing management favoring habitat heterogeneity instead of uniform grazing distributions will likely be more conducive for preserving lesser prairie-chicken populations and grassland biodiversity. © 2021 The Wildlife Society.     

围栏对青藏高原不同类型草地土壤原核微生物多样性的影响

草地退化是草地植被的倒退演替,导致生物多样性丧失和生态系统功能退化,围栏是恢复退化草地生态系统功能的有效管理措施。微生物是土壤中的重要组成部分,在维持草地生态系统稳定性和功能方面发挥着重要作用。然而,目前尚不清楚围栏如何影响不同类型草地土壤微生物群落。以青藏高原草甸、草原和荒漠草地三种草地类型的退化草地为研究对象,设置围栏和放牧两种处理,采用Illumina HiSeq高通量测序技术研究了围栏对土壤原核微生物群落多样性和群落结构的影响。结果表明：围栏未显著影响草甸土壤原核微生物的丰富度、Shannon多样性和均匀度,但显著增加了草原土壤的原核微生物的丰富度、Shannon多样性和均匀度（P<0.05）,稍降低了荒漠草地土壤原核微生物的丰富度、Shannon多样性和均匀度（P=0.086、0.072和0.099）。在围栏处理的草地中,土壤原核微生物丰富度、Shannon多样性和均匀度与年均温、干旱度和pH显著负相关（P<0.01）,与年平均降水量、溶解性有机碳、地上生物量和植物多样性显著正相关（P<0.01）。在放牧处理的草地中,土壤原核微生物丰富度、Shannon多样性和均匀度与年均温和干旱度显著负相关（P<0.05）,但原核微生物丰富度和Shannon多样性与所有土壤理化和植被因素均无显著相关性。冗余分析（RDA）表明,不同类型草地土壤原核微生物群落结构发生了显著的变化,并沿草甸、草原和荒漠草地的过渡逐渐转变（P<0.001）。方差分解分析（VPA）进一步表明,原核微生物群落结构变化主要受年均温、年平均降水量、干旱度和pH的驱动。围栏显著改变了不同类型草地中部分样点土壤原核微生物群落结构。三种草地类型的主要原核微生物优势门均为放线菌门（Actinobacteria）、变形菌门（Proteobacteria）和酸杆菌门（Acidobacteria）。放线菌门（Actinobacteria）的相对丰度在荒漠草地土壤中最高,而变形菌门（Proteobacteria）和酸杆菌门（Acidobacteria）的相对丰度在草甸土壤中最高。此外,不同类型围栏和放牧草地土壤原核微生物类群的相对丰度均无显著差异。研究表明不同类型草地土壤原核微生物群落对围栏的响应不同,这为因地制宜制定草地管理措施提供了数据支持,为草地退化的防治提供了理论支持。     

Management of modern agricultural landscapes increases nest predation rates in Black‐tailed Godwits Limosa limosa

Effective conservation of endangered species requires a solid understanding of the demographic causes of population change. Bird populations breeding on agricultural grasslands have declined because their preferred habitat of herb‐rich meadows has been replaced by grassland monocultures. The timing of agricultural activities in these monocultural grasslands is critical, as they often coincide with the nesting phase of breeding birds. Here, we aim to identify the effect of habitat management and targeted nest protection on nest survival of Black‐tailed Godwits Limosa limosa in the Netherlands, a population that has shown a 70% reduction in breeding population size since the 1970s. To protect nests in monocultures from destruction, farmers are paid to either delay mowing or leave a patch of unmown grass around the nest, a patch which in practice varied in size. In herb‐rich meadows, which are typically managed for bird conservation purposes, mowing occurs after hatching. Nest survival declined as the season advanced, more steeply on monocultures than on meadows. Targeted nest protection was only partially successful, as nest predation was considerably higher on mown grassland monocultures with small unmown patches around the nest than in mown monocultures with large unmown patches and in unmown fields. Increased predator densities over the years have been suggested as an important cause of the trend towards lower nest survival, but here we show that nest survival was higher on herb‐rich meadows than on monocultures, and similar to the 1980s. It thus seems that increased predator densities are an increased threat during the egg stage only if habitat quality is low. High‐quality habitat in the form of herb‐rich meadows therefore provides a degree of protection against predators.     

Don’t judge toxic weeds on whether they are native but on their ecological effects

The sharp rise in anthropogenic activities and climate change has caused the extensive degradation of grasslands worldwide, jeopardizing ecosystem function, and threatening human well‐being. Toxic weeds have been constantly spreading in recent decades; indeed, their occurrence is considered to provide an early sign of land degeneration. Policymakers and scientific researchers often focus on the negative effects of toxic weeds, such as how they inhibit forage growth, kill livestock, and cause economic losses. However, toxic weeds can have several potentially positive ecological impacts on grasslands, such as promoting soil and water conservation, improving nutrient cycling and biodiversity conservation, and protecting pastures from excessive damage by livestock. We reviewed the literature to detail the adaptive mechanisms underlying toxic weeds and to provide new insight into their roles in degraded grassland ecosystems. The findings highlight that the establishment of toxic weeds may provide a self‐protective strategy of degenerated pastures that do not require special interventions. Consequently, policymakers, managers, and other personnel responsible for managing grasslands need to take appropriate actions to assess the long‐term trade‐offs between the development of animal husbandry and the maintenance of ecological services provided by grasslands.     

Is the removal of aboveground shrub biomass an effective technique to restore a shrub‐encroached grassland?

Encroachment of woody plants into grasslands is a global phenomenon that has substantial impacts on pastoral productivity and ecosystem services. Over the past half century, pastoralists and land management agencies have explored various options to control woody plants in order to improve ecosystem services in shrub‐encroached grasslands. We examined the effectiveness of controlling the encroachment of the shrub Caragana microphylla into grassland in Inner Mongolia, China. We cut and removed all of the aboveground biomass from 450 shrubs, predicting that the effectiveness of this technique to control shrubs would depend on shrub morphology. Specifically, we expected that larger shrubs with more biomass would be more difficult to kill by cutting than smaller shrubs. A year after treatment, we found that cutting killed only 11% of the 450 treated shrubs, and of these, three‐quarters of the locations that they occupied reverted to grasses and one‐quarter to bare soil. Shrubs that survived the cutting treatment produced more stems and leaf biomass, and therefore had a greater leaf to stem ratio. Shrubs that died after cutting had a lower crown area and basal area, and less stem biomass than shrubs that resprouted within 12 months of cutting. There were no effects of shrub height on the fate of treated shrubs. Cutting had no effect on understory plant cover or richness, but reproductive plants were taller under shrubs that were not cut. Overall, our study showed that removing aboveground shrub biomass by cutting is an ineffective technique for “restoring” the original grassland community unless shrubs are very small. Strategic targeting of small shrubs would be a more effective technique for controlling the spread of C. microphylla in the long term.     

Relationships between vegetation and bird community composition in grasslands of the Serengeti

The Serengeti–Mara ecosystem holds one of the largest natural grasslands of the world, which is well known for its large herds of mammals. However, the bird community structure of these grasslands has hardly ever been studied. For the first time, a large‐scale study on grassland bird communities has been conducted in all typical open grasslands of the Serengeti National Park. We used ten grassland plots representing a gradient of increasing vegetation height and also including shrubs and trees to analyse the influence of vegetation structure on the composition of grassland bird communities. Three communities of breeding birds were identified in relation to (a) short grass, (b) intermediate and long grass and (c) wooded grasslands. The bird communities of intermediate, long and wooded grassland were very similar, because of identical dominant bird species. Our results suggest that breeding birds of East African grasslands exhibit two contrasting habitat relationships: (1) birds that are restricted to short grass, and (2) species that are tolerant to vegetational shifts from intermediate grass via long grass to early stages of woody vegetation. Because the vegetation is often driven beyond this range in managed tropical grasslands through high grazing pressure or through shrub encroachment, we expect that the long‐grass bird communities will not generally resist anthropogenic disturbance.     

西藏河谷地区人工种草的投入产出比较分析

分析了西藏河谷地区六种草地的经济投入、产出和生态系统服务价值,模拟了投入增加下村落草地利用结构的改变与经济、生态产出的响应。结果表明:草地恢复管理中,围栏草地成本最低,为67元/hm~2,是一年生人工刈割草地的0.9%。围栏等草地恢复管理的经济产出为772元/hm~2,其中补贴收入占14.6%,另85.4%来自打工收入;而多年生人工放牧和一年生人工刈割草地的经济产出为4250元/hm~2与13135元/hm~2。相比经济产出,不同草地管理方式下生态系统服务价值差距有限,最大仅为27%。草地投入增加下,天然放牧草地转变为围栏草地及一年生人工刈割草地,并最终保持约1∶1的面积比。合理配置围栏草地与一年生人工刈割草地,可以实现区域较大的经济收入增长和生态系统服务的保障。     

放牧对草地生态系统影响的研究进展

全球草地占据30%左右的陆地面积, 在全球气候变化、碳氮及养分循环、保持水土、调节畜牧业生产等方面具有重要的作用。目前草地的主要利用方式之一就是放牧, 不同的牲畜种类、放牧强度、年限、历史和制度等, 会影响草地植物群落、生物多样性及土壤微生物, 进而影响草地生态系统结构、功能和过程。该文围绕放牧对草地生态系统结构、功能和过程的影响, 1)回顾了20世纪50年代到现在各个历史阶段放牧对草地生态系统影响的研究; 2)利用文献计量分析的方法, 剖析了放牧对草地影响研究的热点内容、重要区域和关键词等; 3)阐明了放牧对草地植物生长、群落特征、碳氮及养分循环、生产力及土壤质量等的各方面影响的研究进展及国内相关研究的优势及存在的主要问题和不足; 4)基于上述分析, 从草地放牧精准管理、经典假说验证、放牧和全球变化研究相结合等方面, 提出未来研究的前沿方向和优先领域。该文在系统总结放牧对草地生态系统影响的研究进展、研究优势及存在问题的基础上, 提出未来的研究应与全球变化相结合, 为我国的草地放牧生态学研究、适应性管理和可持续利用等提供科学基础。