The processes governing soil bacteria biogeography are still not fully understood. It remains unknown how the importance of environmental filtering and dispersal differs between bacterial taxonomic and functional biogeography, and whether their importance is scale-dependent. We sampled soils at 195 plots across the Tibet plateau, with distances among plots ranging from 20 m to 1,550 km. Taxonomic composition of bacterial community was characterized by 16S amplicon sequencing, and functional community composition by qPCR targeting 9 functional groups involved in N dynamics. Twelve climatic and soil characteristics were also measured. Both taxonomic and functional dissimilarities were more related to environmental dissimilarity than geographic distance. Taxonomic dissimilarity was mostly explained by soil pH and organic matter, while functional dissimilarity was mostly linked to moisture, temperature and N, P and C availabilities. The roles of environmental filtering and dispersal were, however, scale-dependent and varied between taxonomic and functional dissimilarities, with distance affecting taxonomic dissimilarity over short distances (<~300 km) and functional dissimilarity over long distances (>~600 km). The importance of different environmental predictors varied across scales more for functional than taxonomic dissimilarity. Our results demonstrate how biodiversity dimension (taxonomic versus functional) and spatial scale strongly influence the conclusions derived of bacterial biogeography.

The processes governing soil bacteria biogeography are still not fully understood. It remains unknown how the importance of environmental filtering and dispersal differs between bacterial taxonomic and functional biogeography, and whether their importance is scale-dependent. We sampled soils at 195 plots across the Tibet plateau, with distances among plots ranging from 20 m to 1 550 km. Taxonomic composition of bacterial community was characterized by 16S amplicon sequencing, and functional community composition by qPCR targeting 9 functional groups involved in N dynamics. Twelve climatic and soil characteristics were also measured. Both taxonomic and functional dissimilarities were more related to environmental dissimilarity than geographic distance. Taxonomic dissimilarity was mostly explained by soil pH and organic matter, while functional dissimilarity was mostly linked to moisture, temperature and N, P and C availabilities. The roles of environmental filtering and dispersal were, however, scale-dependent and varied between taxonomic and functional dissimilarities, with distance affecting taxonomic dissimilarity over short distances (<~300 km) and functional dissimilarity over long distances (>~600 km). The importance of different environmental predictors varied across scales more for functional than taxonomic dissimilarity. Our results demonstrate how biodiversity dimension (taxonomic versus functional) and spatial scale strongly influence the conclusions derived from bacterial biogeography studies.

Global change drivers such as anthropogenic nutrient inputs simultaneously alter biodiversity, species composition, and ecosystem functions such as aboveground biomass. These changes are interconnected by complex feedbacks among extinction, colonization, and shifting relative abundance. Here, we use a novel temporal application of the Price equation to quantify the functional contributions of species that are lost, gained, and persist under ambient and experimental nutrient addition in 59 global grasslands. Under ambient conditions, compositional and biomass turnover was high, but species losses (i.e., local extinctions) were balanced by gains (i.e. colonization). There was biomass loss associated with species loss under fertilization. Few species were gained in fertilized conditions over time but those that were, and species that persisted, contributed to net biomass gains, outweighing biomass loss. These components of community change are key to understanding the relationship between change in composition, diversity and functioning.

The artificial planting of grassland serves as the most important means of grassland ecological restoration; however, the impact of artificial planting on soil microbial communities is not well understood. In this study, the evolution of the microbial community structure was studied using 16S and ITS gene sequencing techniques, and the microbial community differences between different forage grasses were analyzed, including different density cropping schemes, multi-year degraded grassland and natural grassland. It was found that the high-density planting scheme of multiple pastures exerts a great impact on soil nutrients as well as on the soil microbial community, effectively increasing the relative abundance of Actinobacteria and Basidiomycota, while the microbial community structure was found to be similar to that of natural grassland. However, in artificial planting treatment, the key node microflora group was noted to be bacteria, which was different from that in natural grassland, in which the key node microflora group was fungi. In comparison, fungi were found to be more sensitive than bacteria to different plantings.The rise in soil fungal diversity did not improve phosphate mineralization.Overall, this study may contribute to understanding the influence of artificial grassland on soil properties as well as the succession of microbial communities, How to accelerate the succession process of grassland ecosystem. which are of great significance in promoting artificial technology to restore the ecological environment.

Large-scale patterns of biodiversity and the underlying mechanisms that regulate these patterns are central topics in biogeography and macroecology. The Qinghai-Tibetan Plateau (QTP) is a natural laboratory for studying these issues. However, most previous studies have focused on the entire QTP, and the independent physical geographical subunits in the region are not well understood. We studied the current plant diversity on the Kunlun Mountains, an independent physical geographical subunit located in northwest China, on the northern edge of the QTP. We integrated measures of species distribution, geological history, and phylogeography, and analyzed the taxonomic richness, origin time, and community phylogenetic structure of the plants present in the area. The distribution patterns of 1,911 seed plants highlighted that species were located mainly in the eastern regions of the Kunlun Mountains. Chinese endemic species of seed plants accounted for 29.8% of the total species on the Kunlun Mountains. The biodiversity patterns and mean divergence times (MDT) indicated that the eastern region of the Kunlun Mountains was the center for biodiversity conservation, particularly in the southeastern region, which has served as a museum for plant diversity on the Kunlun Mountains. According to the MDT, the origin time of the Kunlun Mountains’ flora (KMF) was early Miocene (19.40 Ma), and the KMF is ancient. The biogeographical roles of the Kunlun Mountains were corridor and sink, and the corresponding key processes were species immigration and extinction. The extant biodiversity on the Kunlun Mountains has occurred through species recolonization after climatic fluctuations and glaciations during the Quaternary. The Kunlun Mountains also formed a barrier, representing a boundary among multiple floras, and converted the QTP into a closed physical geographical unit. The nearest taxon index indicated that habitat filtering may have played an important role in biodiversity patterns.

Biodiversity and community assembly are central topics in ecological studies, and mountains present natural laboratories for studying these issues. Most previous studies have focused on biodiversity hotspots and tropical regions, and relevant research in the middle and high latitudes is relatively limited. We hypothesized that species dispersion and habitat filtering simultaneously might drive the assembly of the current plant community in temperate region mountains. We studied the plant community of the Kunlun Mountains, an independent physical geographic unit located in northwest China on the northern edge of the Qinghai-Tibetan Plateau. We integrated measures of species distribution, geological history, and phylogeography, and analyzed the taxonomic richness, phylogenetic diversity, and phylogenetic community structure of the current plant community in the area. The distribution patterns of 1,911 seed plants showed that species were distributed mainly in the eastern and the southeastern parts of the Kunlun Mountains, which were considered as conservation targets for biodiversity. Similarities of genera and species strongly indicated that mass species migrations exist among the Kunlun Mountains and adjacent biodiversity hotspots. This indicated that the current patterns of species diversity were from species recolonization, and the plant species of the Kunlun Mountains originated primarily from the Hengduan Mountains which are a biodiversity hotspot. The net relatedness index (NRI) indicated that 17 of the 28 communities were phylogenetic clustering, and the others were phylogenetic dispersion. The nearest taxon index (NTI) indicated that 27 of the 28 communities were phylogenetic clustering, and the phylogenetic community structure of Banma County was the only example of overdispersion. By combining the standard effect size phylogenetic diversity (SES-PD) with the two indexes, we showed that species recolonization was likely to be an important evolutionary process affecting the assembly of current plant communities, and that habitat filtering may have drove the ecological processes of these communities.

1. The reduction of plant diversity following eutrophication threatens many ecosystems worldwide. Yet, the mechanisms by which species are lost following nutrient enrichment are still not completely understood, nor are the details of when such mechanisms act during the growing season, which hampers understanding and the development of mitigation strategies. 2. Using a common garden competition experiment, we found that early-season differences in growth rates among five perennial grass species measured in monoculture predicted short-term competitive dominance in pairwise combinations and that this effect was stronger under a fertilisation treatment. 3. We also examined the role of early-season growth rate in determining the outcome of competition along an experimental nutrient gradient in an alpine meadow. Early differences in growth rate between species predicted short-term competitive dominance under both ambient and fertilized conditions and competitive exclusion under fertilized conditions. 4. The results of these two studies suggests that plant species growing faster during the early stage of the growing season gain a competitive advantage over species that initially grow more slowly, and that this advantage is magnified under fertilisation. This finding is consistent with the theory of asymmetric competition for light in which fast-growing species can intercept incident light and hence outcompete and exclude slower-growing (and hence shorter) species. We predict that the current chronic nutrient inputs into many terrestrial ecosystems worldwide will reduce plant diversity and maintain low biodiversity state by continuously favouring fast-growing species. Biodiversity management strategies should focus on controlling nutrient inputs and reducing the growth of fast-growing species early in the season.

The combinations of taxonomic, functional and phylogenetic method have been frequently advocated to assess how changes in biodiversity affect community structure and ecosystem function. Using a large grassland community database involving 917 species and 118 sites across the eastern and central Tibetan plateau, we found an overall positive biodiversity-productivity relationship in species', functional and phylogenetic space. The relationship, however, was nonlinear, in which biodiversity explained better the variation in community biomass when species diversity was more than a threshold, showing a weak effect of biodiversity on ecosystem function in low species diversity communities. We also found a filled triangle for the limit of the relationship between species' and functional diversity, implying that functional diversity differs significantly among communities when their species diversity is low but finally converges to be a constant with increasing communities' species diversity. Our research suggests that multiple niche processes may structure the Tibetan grassland communities, and their forces tend to balance in high-biodiversity communities.