To qualitatively assess vegetation degradation, degradation indicator species have been developed by comparing vegetation structures between areas near to and far away from livestock camps and water ...points in Mongolia. However, the development of qualitative degradation indicators cannot evaluate whether vegetation has degraded in areas far from livestock camps and water points over time. Thus, we aimed to identify changes in plant species composition over time using historical data collections in the area. Between 2013 and 2015, we recorded plant species compositions in 12 plots located in the steppe zone around Ulaanbaatar, and compared these with historical data collected from the same zone including the locations around Ulaanbaatar during the 1960s-1980s. Ordination analysis showed that the compositional similarity between the current and historical data was low. Moreover, current species compositions were more similar to those of areas neighboring livestock camps and water points (i.e. Heavily grazed areas). Specifically, decreases in the appearance frequency of Koeleria macrantha, Poa attenuata, and Bupleurum bicaule seemed to contribute to compositional differences between current and historical data.
We tested whether the abundance of C(4) vegetation in grasslands of the Mongolian plateau is influenced by grazing conditions. The analysis exploited the politically originated contrast that exists ...between Mongolia (low stocking rate, transhumant system) and the district of Inner Mongolia, China (high stocking rate, sedentary system). We estimated the proportion of C(4) carbon (P(C4)) in grazed vegetation from the relative carbon isotope ratio (δ(13)C) of sheep wool sampled from 298 annual shearings originating from 1996 to 2007. Annual stocking rates varying over time and between the districts of both countries were taken from regional statistics. The P(C4) pattern within the 0.7 million km(2) sampling area was geostatistically analyzed and related to stocking rates and temperature gradients. For similar climatic conditions, P(C4) was the same in both countries. Further, a unique relationship was found between P(C4) and July temperature on both sides of the border, which explained 71% of the pattern. Stocking rate and grazing system had no significant influences on present-day C(3)/C(4) abundance ratio. This finding suggests that recent changes in the C(3)/C(4) ratio of these grasslands are mainly a consequence of regional warming, not overgrazing.
The search for predictions of species diversity across environmental gradients has challenged ecologists for decades. The humped-back model (HBM) suggests that plant diversity peaks at intermediate ...productivity; at low productivity few species can tolerate the environmental stresses, and at high productivity a few highly competitive species dominate. Over time the HBM has become increasingly controversial, and recent studies claim to have refuted it. Here, by using data from coordinated surveys conducted throughout grasslands worldwide and comprising a wide range of site productivities, we provide evidence in support of the HBM pattern at both global and regional extents. The relationships described here provide a foundation for further research into the local, landscape, and historical factors that maintain biodiversity.
Abstract
Mongolian herder households maintain the health and condition of their livestock by adapting to the characteristics of the local vegetation distribution. Thus, predicting future vegetation ...changes is important for stable livestock grazing and sustainable rangeland use. We predicted the distributional extent of rangeland vegetation, specifically desert steppe, steppe and meadow steppe communities, for the period 2081–2100, based on vegetation data obtained from a previous study. Rangeland vegetation data collected in Mongolia (43–50° N, 87–119° E) between 2012 and 2016 (278 plots) were classified into community types. Species distribution modeling was conducted using a maximum entropy (MaxEnt) model. Distribution data for desert steppe, steppe and meadow steppe communities were used as objective variables, and bioclimatic data obtained from WorldClim were used as explanatory variables. CMIP6-downscaled future climate projections provided by WorldClim were used for future prediction. The area under the curve values for the desert steppe, steppe and meadow steppe models were 0.850, 0.847 and 0.873, respectively. Suitable habitat was projected to shrink under all scenarios and for all communities with climate change. The extent of reduction in potential suitable areas was greatest for meadow steppe communities. Our results indicate that meadow steppe communities will transition to steppe communities with future climate change.
Abstract
In Mongolia, overgrazing and the resulting degradation of rangelands are recognized as serious issues. To address rangeland degradation, we sought to develop a broad-scale vegetation ...classification of Mongolian rangeland communities focusing on regional characteristics. Moreover, we sought to clarify the spatial distributions of communities and the environmental drivers of the distributions. Between 2012 and 2016, we surveyed vegetation in 278 plots (each 10 m × 10 m) in different regions of Mongolia (43–50° N, 87–119° E) in plots where grazing pressure is low relative to adjacent areas. The data were grouped into vegetation units using a modified two-way indicator species analysis (TWINSPAN). We then explored the regional characteristics of species compositions and community distributions, as well as relationships between distributions and climatic variables. The modified TWINSPAN classified the vegetation data into three cluster groups, each of which corresponds to a particular type of zonal vegetation (i.e. forest steppe, steppe and desert steppe). The aridity index was identified as an important driver of the distributions of all cluster groups, whereas longitude and elevation were important determinants of the distribution of clusters within cluster groups. Western regions, which are characterized by higher elevation and continentality compared with eastern regions, have lower mean temperature and precipitation during the wettest quarter, leading to differences in species composition within cluster groups. Regional differences in species composition reflect differences in phytogeographic origin. Thus, the framework of species composition and distributional patterns in Mongolian rangeland communities was demonstrated in relation to climatic and geographical factors.
Aim
Plant species continue to be moved outside of their native range by human activities. Here, we aim to determine whether, once introduced, plants assimilate into native communities or whether they ...aggregate, thus forming mosaics of native‐ and alien‐rich communities. Alien species might aggregate in their non‐native range owing to shared habitat preferences, such as their tendency to establish in high‐biomass, species‐poor areas.
Location
Twenty‐two herbaceous grasslands in 14 countries, mainly in the temperate zone.
Time period
2012–2016.
Major taxa studied
Plants.
Methods
We used a globally coordinated survey. Within this survey, we found 46 plant species, predominantly from Eurasia, for which we had co‐occurrence data in their native and non‐native ranges. We tested for differences in co‐occurrence patterns of 46 species between their native (home) and non‐native (away) range. We also tested whether species had similar habitat preferences, by testing for differences in total biomass and species richness of the patches that species occupy in their native and non‐native ranges.
Results
We found the same species to show different patterns of association depending on whether they were in their native or non‐native range. Alien species were negatively associated with native species; instead, they aggregated with other alien species in species‐poor, high‐biomass communities in their non‐native range compared with their native range.
Main conclusions
The strong differences between the native (home) and non‐native (away) range in species co‐occurrence patterns are evidence that the way in which species associate with resident communities in their non‐native range is not species dependent, but is instead a property of being away from their native range. These results thus highlight that species might undergo important ecological changes when introduced away from their native range. Overall, we show origin‐dependent associations that result in novel communities, in which alien‐rich patches exist within a mosaic of native‐dominated communities.
Tredennick et al. criticize one of our statistical analyses and emphasize the low explanatory power of models relating productivity to diversity. These criticisms do not detract from our key ...findings, including evidence consistent with the unimodal constraint relationship predicted by the humped-back model and evidence of scale sensitivities in the form and strength of the relationship.
The search for predictions of species diversity across environmental gradients has challenged ecologists for decades. The humped-back model (HBM) suggests that plant diversity peaks at intermediate ...productivity; at low productivity few species can tolerate the environmental stresses, and at high productivity a few highly competitive species dominate. Over time the HBM has become increasingly controversial, and recent studies claim to have refuted it. Here, by using data from coordinated surveys conducted throughout grasslands worldwide and comprising a wide range of site productivities, we provide evidence in support of the HBM pattern at both global and regional extents. The relationships described here provide a foundation for further research into the local, landscape, and historical factors that maintain biodiversity.
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