Alpha, Beta and Gamma Diversity Differ in Response to Precipitation in the Inner Mongolia Grassland

Abstract

Understanding the distribution pattern and maintenance mechanism of species diversity along environmental gradients is essential for developing biodiversity conservation strategies under environmental change. We have surveyed the species diversity at 192 vegetation sites across different steppe zones in Inner Mongolia, China. We analysed the total species diversity (γ diversity) and its composition (α diversity and β diversity) of different steppe types, and their changes along a precipitation gradient. Our results showed that (i) β diversity contributed more than α diversity to the total (γ) diversity in the Inner Mongolia grassland; the contribution of β diversity increased with precipitation, thus the species-rich (meadow steppe) grassland had greater contribution of β diversity than species-poor (desert steppe) grassland. (ii) All α, β and γ species diversity increased significantly (P<0.05) with precipitation, but their sensitivity to precipitation (diversity change per mm precipitation increase) was different between the steppe types. The sensitivity of α diversity of different steppe community types was negatively (P<0.05) correlated with mean annual precipitation, whereas the sensitivity of β and γ diversity showed no trend along the precipitation gradient (P>0.10). (iii) The α diversity increased logarithmically, while β diversity increased exponentially, with γ diversity. Our results suggest that for local species diversity patterns, the site species pool is more important in lower precipitation areas, while local ecological processes are more important in high precipitation areas. In addition, for β diversity maintenance niche processes and diffusion processes are more important in low and high precipitation areas, respectively. Our results imply that a policy of “multiple small reserves” is better than one of a “single large reserve” for conserving species diversity of a steppe ecosystem, and indicate an urgent need to develop management strategies for climate-sensitive desert steppe ecosystem.

Woody Species Composition in Relation to Spatial and Environmental Gradients in Acacia-Commiphora Vegetation Ecosystem of Ethiopia

“…In line with this result, the study conducted at two sites in Nepal found significant variation in woody species composition between northeast and southwest facing slopes [28]. This pattern may also indicate the indirect impact of altitudinal gradients and topographic aspects on the species composition by limiting the habitat quality and suitability such as soil fertility, precipitation and temperature to support the vegetation which thereby shape the spatial structure of the community assemblages [29][30][31][32][33]11]. Moreover, our study is in congruent with the findings of the previous studies [33][34][35][36] that indicated the effect of altitude gradient on species composition.…”

“…Here, the species composition may be determined by the ecological processes such as environmental filters, biotic interactions and species specific neutral mechanism properties such as dispersal limitation [20,30,37,38]. Specifically, the variation in edaphic and microclimatic factors across spatial scales, altitude gradient and the topographic aspects differently affect the species adaptability and thereby the composition structure and distribution as this was also found by the previous findings from China and South Africa [11,12,35]. In line with this, our results pointed out that the majority of the rare species are specific to each site that may attribute towards the heterogeneities in species composition among these sites.…”

“…The knowledge of the species diversity across spatial scales is crucial to develop conservation strategies and ensure biodiversity conservation [10,11]. Despite there is high diversity of vegetation ecosystems in the tropical regions our understanding of the spatial pattern and extent of change in species composition is poor [12].…”

Drivers of diversity at the local- and landscape-scale in a fire-prone landscape

“…Yet knowledge gaps remain on the relative importance of these different drivers of 54 species richness at intermediate or landscape scales-the scales at which management decisions are most often made (Heikkinen and Birks 1996;Niemelä 1999;Koivula 2001 Haslem and Bennett 2008). As landscape heterogeneity increases within a given area, the amount of between-habitat (beta) diversity of species within that area is likely to increase (Tews et al 2004;Zhang et al 2014). This is one common explanation for species-area relationships: as the area sampled increases, so does the number of different habitats (Williams 1964;McGuinness 1984;Boecklen 1986;Olszewski 2004).…”

“…By definition, the mean alpha diversity (number of different species per site sampled) in landscapes with more preferred habitat is higher. A greater extent of the preferred habitat type will support more individuals, which through passive sampling will include more species (Osman 1977;Connor and McCoy 1979;McGuinness 1984;Maron et al 2013;Zhang et al 2014). …”