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1.
Soil properties are thought to affect annual plant productivity in rangelands, and thus soil variables that are consistently correlated with plant biomass may be general indicators of rangeland health. Here we measured several soil properties (e.g. aggregate stability, organic carbon, total nitrogen) and tested each as a would-be predictor of local variation in peak aboveground grassland biomass. Individual properties explained a slight (≤10%) amount of variation in plant biomass. Plant biomass was mainly (negatively) associated with two soil properties, subsurface soil carbonate concentration and the stability of soil macroaggregates near the soil surface. Less important predictive variables included: elevation, plant community composition, surface soil organic carbon, and soil carbon:nitrogen. Plot-to-plot variation in plant biomass is seemingly difficult to predict based on soil properties, including popular indicators of soil and rangeland health and even root biomass. While protection of soil is critical to overall rangeland ecosystem function, our findings suggest that the relationship between soil properties and plant biomass in natural grasslands is complex. Thus, there may not be one or even several soil properties that consistently predict appreciable variation in peak grassland biomass, especially variation within an ecosystem independent of precipitation.  相似文献   

2.
Scattered trees are considered keystone structures and play an important role in Mediterranean sylvopastoral systems. Such systems are associated with high biodiversity and provide important natural resources and ecosystem services. In this study, we measured the contribution of scattered trees and different grazing management (cattle, sheep and wildlife only) to the diversity of the grassland sward in a dehesa (open holm oak woodland) located in Central Spain. We analyzed alpha and beta diversity through measurement of species richness, Shannon-Wiener, and Whittaker indices, respectively; and the floristic composition of the herb layer using subplots within two adjacent plots (trees present vs. trees absent) under three different grazing management regimes, including wildlife only, during a year. We found a 20–30% increment in the alpha diversity of wooded plots, compared to those without trees, regardless of grazing management. All beta indices calculated showed more than 60% species turnover. Wooded plots were occupied by different herbaceous species in different heterogeneous microsites (under the canopy, in the ecotone or on open land) created by the trees. Livestock grazing modified species composition (e.g. more nitrophilous species) compared to wildlife only plots. In addition to all their other benefits, trees are important to maintaining grassland diversity in Mediterranean dehesas.  相似文献   

3.
刘兴元  龙瑞军 《生态学报》2013,33(11):3404-3414
根据藏北那曲高寒草地的生产力、季节放牧重要性、生态服务价值、生态环境敏感性,构建了基于草地亚类的功能分区模型,从空间上将高寒草地划分为适度生产功能区、减畜恢复功能区和禁牧封育功能区,据此构建了基于高寒草地功能分区的分级生态补偿模式,设计了高寒草地生态补偿的组织管理体系及流程、生态补偿的损益评估机制和约束奖惩机制;提出了针对不同功能区的生态补偿方案.根据藏北那曲高寒草地功能分区结果和不同功能区生态补偿内容和目标,确定生态补偿周期为5a,核算出适度生产功能区、减畜恢复功能区和禁牧封育保护功能区分别需要补偿资金19.4亿元、15.77亿元和0.6亿元,每年分别需补偿资金3.88亿元、3.16亿元和0.12亿元,5a全区共需补偿资金35.77亿元,年需7.16亿元.通过对高寒草地的功能分区分级生态补偿,对提高高寒草地的生态保护能力,增加牧民的经济收入,促进藏北高寒草地生态系统的可持续发展具有重要的理论和实践意义.  相似文献   

4.
Although remote sensing technology has been used to evaluate regional ecosystem health for a long time, it is still necessary to find a suitable index system to better evaluate ecosystem health. This study aims to improve the ecosystem health measurement ability of remote sensing technology. This research was carried out in Fuzhou under the traditional Vigor-Organization-Resilience (VOR) framework by optimizing and improving the construction method of sub-indexes. Sub-indexes were constructed using spectral index analysis, landscape theoretical ecology model and spatial measurement. Three remote sensing datasets were used (1996, 2008 and 2021) to carry out remote sensing diagnosis of regional ecosystem health in the Fuzhou administrative region. The main research findings and conclusions were as follows. A new comprehensive vigor index (CVI) was developed by the principal component analysis (PCA) based on the four indicators: fractional vegetation cover (FVC), global vegetation moisture index (GVMI), vegetation temperature condition index (VTCI), normalized differential build-up and bare soil index (NDBSI). A new organizational index was constructed based on the landscape index. Four types of indexes, namely landscape heterogeneity (LH), landscape connectivity (LC), the shape characteristics of forest patches (CS) and the connectivity of forest patches (CC) were used as the main factors for calculating the organizational index. A resilience index calculation framework was proposed based on the habitat quality model. The temporal and spatial characteristics of ecosystem health were evaluated and analyzed. The regional ecosystem health value of the whole region reduced gradually, with average values of 0.3521 (1996), 0.3445 (2008) and 0.3345 (2021) respectively. The average reduction rate was 0.0007 per year (1996–2021). The proposed remote sensing diagnosis method provides a complete framework for solving the problems of measuring the dynamic evolution process and characteristics of regional ecosystem health.  相似文献   

5.
Grasslands are constructed for soil and wildlife conservation in agricultural landscapes across Europe and North America. Constructed grasslands may mitigate habitat loss for grassland-dependent animals and enhance ecosystem services that are important to agriculture. The responses of animal species richness and abundance to grassland habitat quality are often highly variable, however, and monitoring of multiple taxa is often not feasible. We evaluated whether multiple animal taxa responded to variation in constructed grassland habitats of southwest Ohio, USA, in ways that could be predicted from indicators based on quality assessment indices, Simpson diversity, and the species richness of ants and plants. The quality assessment indices included a widely used Floristic Quality Assessment (FQA) index, and a new Ant Quality Assessment (AntQA) index, both based on habitat specificity and species traits. The ant and plant indicators were used as predictor variables in separate general linear models of four target taxa—bees, beetles, butterflies and birds—with response variables of overall species richness and abundance, and subsets of taxa that included the abundance of ecosystem-service providers and grassland-associated species. Plant Simpson diversity was the best-fitting predictor variable in models of overall bee and beetle abundance, and the abundance of bees classified as ecosystem-service (ES) providers. FQA and plant richness were the best predictors of overall butterfly species richness and abundance. Ant species richness was the best predictor of overall bird species richness and abundance as well as the abundance of ES birds, while the AntQA index was the best predictor for the abundance of grassland bird and butterfly species. Thus, plant Simpson diversity and ant species richness were the most effective indicators for complementary components of grassland animal communities, whereas quality assessment indices were less robust as indicators and require more knowledge on the habitat specificity of individual ant and plant species.  相似文献   

6.
治理草原退化是我国草原管理的重点和难点。我国目前关于草原退化判断、退化程度、原因及治理等系列问题的确定几乎皆以科学研究结果为依据,而忽视了牧户作为草原直接使用者和管理者的重要性。牧户对草原有自己的判断和认知,其与科学方法研究之间的矛盾已经影响到草原生态保护政策的有效实施。以内蒙古东部草甸草原牧户尺度草原为研究对象,借助牧户调研和野外调查相结合的方法,将牧户划分为高、中、低3个经济水平,并运用Condition-Vigor-Organization-Resilience (CVOR)指数评价法,分析评价草原生态系统健康状况。研究结果显示,牧户对草原健康状况的感知主要从植被、土壤、牲畜等方面,与科学方法评价指标选取具有相似性;牧户感知和CVOR指数法评价结果具有一致性,均判定草原生态系统呈现不同程度退化;统计检验显示牧户对植被、土壤、牲畜影响等指标变化感知方面均不存在显著差异(P0.05),CVOR指数法下不同经济水平牧户草场健康指数之间亦无显著差异(P0.05),两种方法均显示不同经济水平牧户草场退化程度无显著差异(P0.05)。研究证实了牧户感知在指标选取、评价结果方面具备用于准确评价草原健康状况的可行性和可信度。两种方法相互补充,将有利于更加准确、实时动态监测和评价牧户尺度草原生态健康状况,为调整优化畜牧业生产实践提供指导和草原生态保护和建设政策的有效实施提供保障。  相似文献   

7.
Livestock grazing affects over 60% of the world's agricultural lands and can influence rangeland ecosystem services and the quantity and quality of wildlife habitat, resulting in changes in biodiversity. Concomitantly, livestock grazing has the potential to be detrimental to some wildlife species while benefiting other rangeland organisms. Many imperiled grouse species require rangeland landscapes that exhibit diverse vegetation structure and composition to complete their life cycle. However, because of declining populations and reduced distributions, grouse are increasingly becoming a worldwide conservation concern. Grouse, as a suite of upland gamebirds, are often considered an umbrella species for other wildlife and thus used as indicators of rangeland health. With a projected increase in demand for livestock products, better information will be required to mitigate the anthropogenic effects of livestock grazing on rangeland biodiversity. To address this need, we completed a data‐driven and systematic review of the peer‐reviewed literature to determine the current knowledge of the effects of livestock grazing on grouse populations (i.e., chick production and population indices) worldwide. Our meta‐analysis revealed an overall negative effect of livestock grazing on grouse populations. Perhaps more importantly, we identified an information void regarding the effects of livestock grazing on the majority of grouse species. Additionally, the reported indirect effects of livestock grazing on grouse species were inconclusive and more reflective of differences in the experimental design of the available studies. Future studies designed to evaluate the direct and indirect effects of livestock grazing on wildlife should document (i) livestock type, (ii) timing and frequency of grazing, (iii) duration, and (iv) stocking rate. Much of this information was lacking in the available published studies we reviewed, but is essential when making comparisons between different livestock grazing management practices and their potential impacts on rangeland biodiversity.  相似文献   

8.
Land‐use change has resulted in rangeland loss and degradation globally. These changes include conversion of native grasslands for row‐crop agriculture as well as degradation of remaining rangeland due to fragmentation and changing disturbance regimes. Understanding how these and other factors influence wildlife use of rangelands is important for conservation and management of wildlife populations. We investigated bat habitat associations in a working rangeland in southeastern North Dakota. We used Petterson d500x acoustic detectors to systematically sample bat activity across the study area on a 1‐km point grid. We identified calls using Sonobat autoclassification software. We detected five species using this working rangeland, which included Lasionycteris noctivagans (2,722 detections), Lasiurus cinereus (2,055 detections), Eptesicus fuscus (749 detections), Lasiurus borealis (62 detections), and Myotis lucifugus (1 detection). We developed generalized linear mixed‐effects models for the four most frequently detected species based on their ecology. The activity of three bat species increased with higher tree cover. While the scale of selection varied between the four species, all three investigated scales were explanatory for at least one bat species. The broad importance of trees to bats in rangelands may put their conservation needs at odds with those of obligate grassland species. Focusing rangeland bat conservation on areas that were treed prior to European settlement, such as riparian forests, can provide important areas for bat conservation while minimizing negative impacts on grassland species.  相似文献   

9.
We describe an approach to assessing biological health in a heavily utilized, large lowland river setting, using the example of the lower Yellow River, China. In this study, the river was divided into four reaches, and a field survey of fish, benthic macroinvertebrates, and riparian plants was undertaken. Data from historical records were used for reference. The scoring system used weighting to adjust for differences in the importance of the chosen indicators and the relative efficiency of the sampling effort. The results indicated that the biological health of the lower Yellow River is distant from historical reference conditions, with its condition generally declining in the downstream direction. This result is consistent with the river’s history of impairment of hydrology, water quality, wetland area and character, and physical form. We conclude that the reference river state based on historical conditions is unlikely to equate to the best attainable river health because certain changes have occurred in the river that may prohibit a return to the previous state of ecological health. On the basis of the results of this assessment as well as a review of the literature, we propose field data collection methodologies and indicators that can be applied in future assessments.  相似文献   

10.
Species‐rich semi‐natural grasslands in Europe are becoming more fragmented and many species that depend on this habitat type are rare and threatened today. Management methods like mowing and grazing are needed to preserve remaining grasslands. Because management is costly it is important to use the most cost‐effective as well as the most beneficial management method, but few studies have compared mowing and grazing. We investigated the effect of mowing and grazing on grassland vegetation using data from 11 long‐term field trials situated in southern Sweden. We calculated the change in the odds of finding species belonging to three different groups of indicators at the start of the treatment and after 8 and 14 years. The used indicator groups were indicators of good management, excess nitrogen and poor management. The results revealed an increase in the odds of finding indicators of good management in mowed plots and an increase in finding indicators of excess nitrogen in grazed plots. The odds of finding indicators of poor management remained unchanged. Results from sub‐analysis of the grazing intensity showed a more negative effect from grazing with low grazing intensity than normal/high grazing intensity. Therefore, mowing is the best long‐term management method for semi‐natural grasslands in Sweden and grazing using a low grazing intensity should be avoided.  相似文献   

11.
随着全球变化对生物多样性的影响不断加剧, 生物多样性与生态系统功能之间相互关系(BEF)的研究显得极为重要。过去的20多年, BEF的研究大多集中在对物种多样性与单一或少数生态系统功能之间关系的探讨, 但生态系统最为重要的价值是同时维持多种服务和功能的能力, 基于此, 该文首次在国内引入近年来不断完善的生态系统多功能性(multifunctionality)的概念, 并对目前主流的评价方法进行了改进, 从而对内蒙古三种利用方式(刈割、围封、放牧)下的草地群落进行了多功能性评价, 并探讨了多功能性与物种多样性之间的关系。结果显示本研究改进的方法和目前主流方法评价得出的多功能性指数在样方和样地尺度上都有很高的相关性(R2 = 0.6956, p < 0.0001; R2 = 0.9231, p < 0.0001), 表明该文作者改进后的方法是可靠的。重度放牧的草地群落物种多样性水平最低, 绝大多数土壤功能指标较差, 表现出退化特征; 7年的围封和刈割群落均有较高的物种多样性水平和改善的土壤功能指标; 三者的多功能性指数为刈割(0.2178) >围封(0.0704) >放牧(-0.8031)。植被样方主要沿水肥梯度分布; 多样性指数中, 均匀度指数(Pielou index)和丰富度指数(Margelf index)对多功能性的影响作用最大, 均为样方尺度(R2 = 0.1871, p < 0.0001; R2 = 0.1601, p < 0.0001)小于样地尺度(R2 = 0.5921, p = 0.0093; R2 = 0.7499, p = 0.0007), 有尺度依赖性; 多功能性在样方和样地尺度上均与物种均匀度呈线性正相关关系, 而与物种丰富度呈单峰曲线关系。该文研究结果表明, 相对于重度放牧和围封, 刈割更有利于维持该地区生态系统的多功能性; 物种丰富度适中且物种分布均匀的生态系统可能有更好的多功能性。  相似文献   

12.
《植物生态学报》2016,40(8):735
Aims Over the past twenty years, most biodiversity and ecosystem functioning (BEF) research has focused on the effects of species diversity on single or just a few ecosystem functions. However, ecosystems are primarily valued for their ability to maintain multiple functions and services simultaneously (i.e. multifunctionality here- after). This paper first introduced the constantly perfected concept of “multifunctionality”, and then tried to make some modifications to the current mainstream quantitative method in order to evaluate the multifunctionality of grassland communities with the management of clipping, enclosure and grazing in Inner Mongolia, investigating the relationship between the multifunctionality and species diversity. Methods In free grazing grassland, four sites were set and each site was divided into two parts to conduct enclosure and clipping management respectively. After seven years, 15 quadrats (1 m × 1 m) were established for each type of management in each site (total 60 quadrats for each type) using the regular arrangement method; as a control, we also established 20 quadrats (two sites) in grazing grassland. For each quadrat, we carried out plants census and collected soil mixture sample, measuring 16 soil variables, and then calculated the biodiversity indices and multifunctionality index (M-index) by means of factor analysis. Important findings The results showed that M-indexes by the two evaluation methods were strongly correlated at both quadrat and site scale, suggesting that our modified method was reliable. Over-grazed communities had the lowest biodiversity indices and their most soil indicators were also low, showing obvious degradation features. Enclosure and clipping communities (seven years) had higher biodiversity and better soil indicators. The rank of M-indexes was clipping community (0.2178) > enclosure community (0.0704) > grazing community (-0.8031). The vegetation was distributed mainly along the gradients of water and fertility. Among the biodiversity indices, evenness (Pielou) index and richness (Margelf) index were most strongly correlated with multifunctionality, and their explanatory power (R2) for M-index were higher at site scale (R2 = 0.5921, p = 0.0093; R2 = 0.7499, p = 0.0007) than at quadrat scale (R2 = 0.1871, p < 0.0001; R2 = 0.1601, p < 0.0001), indicating study scale played an important role in the determinants of multifunctionality. At both quadrat and site scales, M-indexes is a linear positive function with species evenness and a hump-shaped function of species richness. Therefore, in contrast to enclosure, clipping was more conducive to maintain the ecosystem multifunctionality in this region, and the ecosystem with moderate specie richness, where these species are evenly distributed might have better multifunctionality.  相似文献   

13.
14.
Rangelands provide the main forage resource for livestock in many parts of the world, but maintaining long-term productivity and providing sufficient income for the rancher remains a challenge. One key issue is to maintain the rangeland in conditions where the rancher has the greatest possibility to adapt his/her management choices to a highly fluctuating and uncertain environment. In this study, we address management robustness and adaptability, which increase the resilience of a rangeland. After reviewing how the concept of resilience evolved in parallel to modelling views on rangelands, we present a dynamic model of rangelands to which we applied the mathematical framework of viability theory to quantify the management adaptability of the system in a stochastic environment. This quantification is based on an index that combines the robustness of the system to rainfall variability and the ability of the rancher to adjust his/her management through time. We evaluated the adaptability for four possible scenarios combining two rainfall regimes (high or low) with two herding strategies (grazers only or mixed herd). Results show that pure grazing is viable only for high-rainfall regimes, and that the use of mixed-feeder herds increases the adaptability of the management. The management is the most adaptive with mixed herds and in rangelands composed of an intermediate density of trees and grasses. In such situations, grass provides high quantities of biomass and woody plants ensure robustness to droughts. Beyond the implications for management, our results illustrate the relevance of viability theory for addressing the issue of robustness and adaptability in non-equilibrium environments.  相似文献   

15.
Dry savannahs are highly sensitive to climate change and under intense anthropogenic pressure. Therefore, the methods for assessing their status should be easy and repeatable. Monitoring through satellite data and field measurements are limited in accurately assessing the spatiotemporal dynamics of ecosystems. Fortunately, emerging technologies like Unmanned Aerial Systems (UAS) allow to transcend these limitations. But their calibration with field data for application in rangelands is still relatively new and less common than for example in precision agriculture. In this study we developed a drone-based workflow for mapping the condition of rangelands in dryland savannah. We evaluated how accurately and efficiently the two common indicators (i.e., potential forage biomass and rangeland cover type) of rangeland condition can be estimated from drone imagery across a range of conditions (i.e., highly degraded to healthy rangelands). To develop the drone-based potential forage biomass model we tested the accuracy of four vegetation indices to predict field biomass, with the optimized soil adjusted vegetation index (OSAVI) showing the highest prediction accuracy (R2 = 0.89 and RMSE = 194.05). The OSAVI-based model yielded a significant strong relationship (R2 = 0.80, p < 0.001) between predicted and field observed potential forage biomass across the rangeland system. For land cover, we applied a decision tree classification based on thresholds determined using data mining, with a mean overall accuracy of 95.8%. The drone-based estimates of bare cover, herbaceous cover and woody cover showed strong agreements (R2 ranging between 0.86 and 0.97) with the two image-truthing methods (line-point intercept and visual estimations) tested. We show that the drone-based approach is more efficient, unbiased, and repeatable than the field methods. Based on these results, the drone-based workflow presented here offers a reproducible, accurate and efficient approach for near-real time monitoring of rangeland condition at a landscape level. This may assist with climate-adapted management to prevent further land degradation and associated threats to biodiversity and human livelihoods.  相似文献   

16.
The restoration of floodplain grasslands has benefited from many studies of the underlying mechanisms. Among the operational tools that resulted, hay transfer is now used increasingly to alleviate the effects of limited seed dispersal and recruitment. To improve this method, we still need to understand how it can affect restoration trajectories, and particularly their direction and magnitude during the early stages of restoration. Based on concepts from the field of community ecology theory, we investigated the effects of early‐stage management through grazing or mowing on restoration trajectories after soil harrowing and hay transfer. We established a randomized block design experiment and quantified several community‐related metrics to formalize restoration trajectories for 3 years after hay transfer on a previously arable alluvial island in southwestern France. Whatever the management treatment, the species richness and evenness were significantly higher in hay‐inoculated than in control plots. This effect was linked to the recruitment of species originating not only from the reference grassland through hay transfer, but also from the seed bank, a well‐known effect of soil harrowing. Although generally oriented toward the reference grassland, the origin, direction, and magnitude of the trajectory of hay‐inoculated plots all depended on the management applied. Sheep grazing applied at the same time as hay transfer enhanced the recruitment of reference species as from the first experimental year, because it controlled aboveground competition and maintained the window of opportunity open for a sufficiently longer period of time. Our findings show that the type of management applied simultaneously to hay transfer influences the origin of a grassland trajectory, while its direction and magnitude are dependent on the management applied in subsequent years. Grazing immediately after hay transfer may be appropriate to accelerate the recruitment of species from the reference grassland.  相似文献   

17.
Despite abundant literature on indicators for sustainable resource management, practical tools to help local users to apply its general concepts at a local to regional level are scarce. This means that decisions over land evaluation and land use at a local level are often not based on the formal application of indicators or decision support systems for environmentally sound management but instead on the opinion of local expertise, for instance forest managers, cattle breeders, farmers and/or academics. This is particularly seen to be the case in the tropics where access to modern communication and information technologies is restricted.As the opinions of experts are often based on and influenced by personal experience, intuition, heuristics and bias, their evaluations and decision are often unclear to the non-expert working at a local level. In order to make their reasoning more comprehensible to the non-expert, the ecological condition of 176 plots in the tropical Southeast of Mexico were evaluated by experts on soil fertility, forest management, cattle breeding and agriculture. With the assistance of a knowledge engineer (one who converts expert knowledge and reasoning into a model), these expert opinions and reasoning were then translated into a formal computer model.As an alternative approach we applied a knowledge discovery technique, namely the induction of regression trees and automatically developed models using the expert evaluations as training data. Where knowledge engineering was tedious and time consuming, regression models could be rapidly generated. Moreover, the correspondence between regression trees and expert opinions was considerably higher than the correspondence between expert opinion and their own models. The regression trees used less explicative variables than the models generated by the experts. The minimisation of sampling effort due to variable space reduction means that the application of regression tree induction has a high potential for a rapid development of indicators for narrowly defined ecological assessments, needed for decision making on a local or regional scale.  相似文献   

18.
In France, numerous Protected Designation of Origin (PDO) cheese value chains have revised their specifications to address environmental protection, particularly at the farm level. In this stage, it is nevertheless impossible to state whether the proposed modifications may ensure the sustainability of environmental protection as no environmental sustainability diagnostic has been conducted. The aim of this study is to construct an assessment method for the Cantal PDO farms.A multi-criteria assessment approach was implemented in the following 5 steps: definition of the framework of the study, determination of the principles and criteria, definition of the indicators, aggregation of all elements of the assessment, and finally, test of the assessment method on farms. Focus groups meetings were organised for the first four steps. The panel discussions were based on data obtained from both the literature and surveys of stakeholders operating in the value chain and within the territory.The obtained assessment method comprises 4 principles characterised by 33 indicators. The most important principle (45%), management of grassland resources, is a key economic and environmental point of the studied farms. It reflects the necessary intensive use of grass by the animals in the PDO farms. Few existing methods addressed this principle that required the design of several new indicators. The second principle, impact of agricultural practices (25%), is often included in environmental sustainability assessment methods The adopted indicators are, thus, drawn from existing methods and adapted to the context of the farms studied. The management of the farm buildings and the landscape principle (18%) is often considered in social sustainability. Its role in environmental sustainability can be explained by its strong link with the image of PDO products. Primarily drawn from the literature, the used indicators have been extended to make the assessment method as objective as possible. Finally, the management of local, energy and water resources principle has the lowest weighting (12%). This can be explained by the limited number of indicators.This assessment method was constructed for the Cantal PDO farms by considering their environment and particularities. In consequence, the stakeholders have taken ownership of it. It could be used by other ruminant systems based on grassland. The development of numerous indicators enhanced the pool of existing indicators. This assessment method was sensitive and allowed for the discrimination between farms.  相似文献   

19.

Hardin’s Tragedy of the Commons has often been cited as the rationale for the privatization of pastures throughout the world, yet rangeland degradation is still widespread. A significant body of ecological research has demonstrated negative impacts from limiting herd movement through fencing. The privatization of pastures has often followed heterogeneous patterns. We use a natural experiment in common grazing areas on the eastern Qinghai-Tibetan Plateau where land use was privatized beginning in 1999 following different land use division patterns. We measure the relationship between land use privatization paths and grassland quality using satellite data from 1989 to 2011 in five different villages, and compare how well herder environmental perceptions match satellite data. We find that rangeland degradation has significantly increased following privatization of land use, and that grassland in small individually managed fenced plots is deteriorating more significantly than in larger fenced areas with group herding. We further find that herders’ had accurate perceptions of the state of their pastures that closely match remotely sensed data.

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20.
Zaal Kikvidze 《Oikos》2000,89(1):123-127
In this study I used small squares (4 cm×4 cm) as a sampling technique within plots (128 cm×128 cm) of different elevation, aspect and slope angle in grassland communities (20 plots examined). Then I used a rectangular hyperbole equation (the Michaelis-Menten model) to describe species richness and the Inverse of Simpson Concentration (ISC) as functions of sample size. I checked robustness and precision of the model both by interpolation and extrapolation. Interpolation was similarly good in both cases, while extrapolation produced reliable predictions of ISC but underestimated species richness. Dominance analysis indicated that the underestimation of richness depends on the proportion of bottom species, and that the predicted values of richness roughly coincide with the numbers of dominant species found in plots. Therefore, the model may be used to assess number of dominant species when precision is less important than saving time during a survey. However, the rectangular hyperbole equation appears to be precise and robust in the prediction of ISC, at least in grassland communities. This property may also be employed for extrapolation of diversity indices with a limited sampling effort.  相似文献   

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