Grazing exclusion-induced shifts, the relative importance of environmental filtering, biotic interactions and dispersal limitation in shaping desert steppe communities, northern China

Abstract

Grazing exclusion is one of the most efficient approaches to restore degraded grassland but may negatively affects the recovery of species diversity. Changes in plant species diversity should be a consequence of the ecological assembly process. Local community assembly is influenced by environmental filtering, biotic interactions, and dispersal. However, how these factors potentially contribute to changes to species diversity is poorly understood, especially in harsh environments. In this study, two management sites within a Stipa breviflora desert steppe community (typical natural steppe) were selected in northern China. In one of the two management sites, grazing has been excluded since 2010 and in the other with open grazing by sheep. In August 2016, three plots were established and 100 sampling units were created within each plot in a 5 m×5 m area at the two management sites. To assess the effects of grazing exclusion on S. breviflora steppe, we analyzed the vegetation biomass, species diversity, soil organic carbon, and soil particle size distribution using paired T-tests. In addition, variation partitioning was applied to determine the relative importance of environmental filtering and dispersal limitation. Null mode analysis was used to quantify the influence of biotic interactions in conjunction with EcoSim niche overlap and co-occurrence values. Our results demonstrated that (1) species diversity significantly decreased and the main improvements in soil quality occurred in the topsoil 0-10 cm after the grazing exclusion; (2) environmental filtering was important for community assembly between grazed and fenced grassland and this appears particularly true for soil particle size distribution, which may be well correlated with soil hydrological processes; and (3) however, competitive exclusion may play a significant role within the exclusion. The multiple pathways of assembly may collectively determine negative effects on the restoration of species diversity. Therefore, designers should be aware of the risk of reducing grazing exclusion-induced species diversity and account for manipulating processes. This in turn will reduce dominant species and promote environmental heterogeneity to maximize species diversity in semi-arid regions.

Effect of different grazing intensities on bacterial community composition and diversity in rhizosphere and non-rhizosphere soils in desert steppe of China

“…In addition, Bacillus was clearly dominant in the nonrhizospheric soil bacterial composition, and was the main reason for the changes in soil bacterial abundance. The bacterial abundance of non-rhizospheric soil at the 0-10 cm depth increased in LG, probably because grazing had a significant effect on topsoil quality (Wang et al, 2018). We found that differences in grazing intensity had nonsignificant effect on the bacterial community structure of non-rhizospheric soil.…”

Nostoc flagelliforme – ein Bakterium unter Naturschutz

“…Allerdings werden die Maßnahmen auch kritisch gesehen . So verändern zum Beispiel absolutes Weideverbot und Stickstoffdüngung die Zusammensetzung der Pflanzengesellschaften mit negativen Folgen für die Erosionsresistenz des Bodens . Ebenso wird der aktiven Wiederansiedlung des natürlichen Stickstofflieferanten N. flagelliforme noch wenig Beachtung geschenkt.…”

Phenotypic plasticity of Artemisia ordosica seedlings in response to different levels of calcium carbonate in soil

“…Artemisia ordosica, is a dominant species of psammophyte communities that form on sandy lands in arid and semi-arid areas of Northwest China. The restoration of plant communities dominated by A. ordosica is currently of great importance for controlling degraded vegetation ecosystems in the region of study (Wang et al, 2018).…”