Effects of short-term grazing prohibition on soil physical and chemical properties of meadows in Southwest China

Background Grassland plays an important role in the ecosystem, but overgrazing harms the grassland system in many places. Grazing prohibition is an effective method to restore grassland ecosystems, and it plays a great role in realizing the sustainable development of grassland systems. Therefore, it is necessary to carry out research on the influence of regional grazing prohibition on the physical and chemical properties of different grassland systems. Methods In Potatso National Park, Southwest China, we selected experimental plots in the artificial grazing meadow area to study the effects of grazing prohibition on plant and soil indexes in subalpine meadows and swamp meadows. We investigated the biomass and species diversity of grazing prohibition treatment and grazing treatment plots and sampled and tested the soil index. The variation percentage was used to remove the original heterogeneity and yearly variation, allowing us to compare differences in plant index and soil index values between grazing prohibition and grazing treatments. Results Grazing prohibition increased the aboveground biomass, total biomass, total meadow coverage, average height, richness index, Shannon diversity index and evenness index and reduced the belowground biomass and root/shoot ratio in the subalpine meadow and swamp meadow. Additionally, grazing prohibition reduced the pH and soil bulk density and increased the soil total carbon, soil organic carbon, soil total nitrogen, soil hydrolyzable nitrogen, soil total phosphorus and soil available phosphorus in the subalpine meadow and swamp meadow. Nonmetric multidimensional scaling (NMDS) analysis showed that both plant indexes and soil indexes were significantly different between grazing and grazing prohibition treatments and between meadow types. Short-term grazing prohibition had a great impact on improving the fertility of meadow soil in the study area. We suggest that long-term and extensive research should be carried out to promote the restoration and sustainable development of regional grassland systems.

Functional diversity and redundancy of subalpine meadows subjected to anthropogenic disturbances

Aims The aims of this study were to assess how functional diversity and redundancy respond to subalpine meadow ecosystem degradation under anthropogenic disturbance and how species contribute to functional redundancy along the disturbance gradient. Methods The study was carried out in the subalpine meadow in Mount Jade Dragon, which is located at the southeastern edge of the Tibetan Plateau. Four disturbance intensities [no disturbance (ND), weak disturbance (WD), moderate disturbance (MD), and severe disturbance (SD)] were identified. Species richness, soil properties, and five key plant functional traits were assessed along the disturbance gradient. Simpson’s diversity index, functional diversity based on the Rao algorithm, functional redundancy, community weighted mean of each functional trait, and species-level functional redundancy were determined. Important Findings Unimodal change pattern of functional diversity and functional redundancy along the disturbance gradient were found in the present study, with their maximum in MD and WD, respectively. Species diversity showed a decreasing trend with increasing disturbance intensity. As disturbance intensified, species with traits related to conservative growth strategies, such as low specific leaf area (SLA) and high leaf dry matter content (LDMC), decreased, whereas species with resource acquisitive strategies, such as small plant, high SLA and low LDMC, increased in the community. At the species level, species showed species-specific roles in functional redundancy. Notably, some species were important in the community in terms of their unique function. For instance, Ligularia dictyoneura in ND and Potentilla delavayi in MD and SD.

The current state of mountain meadow soils of subalpine pasture ecosystems of the Central Caucasus (elbrus altitudinal zonality)

Intensive recreational, agricultural and logistics land use in uplands leads to their transformation and degradation. Subalpine meadow ecosystems of Central Caucasus are traditionally used for grazing and mowing. The work determined the current state of soils on pastures (mountain meadow-steppe subalpine soil and mountain meadow subalpine soil) and the level of changes of their properties under different stages of pasture degradation were defined. The efficacy of 4-stage assessment system for evaluating the pasture degradation of grasslands dominated by Bromus variegatus M. Bieb. was shown for the assessment of soil cover condition. The reduce of estimated soil indicators and degradation of soils under pastures with maximal degradation stage (DS3) of meadow ecosystems was statistically significant.

Soil Bacterial Community Response and Nitrogen Cycling Variations Associated with Subalpine Meadow Degradation on the Loess Plateau, China

ABSTRACT Grassland degradation is an ecological problem worldwide. This study aimed to reveal the patterns of the variations in bacterial diversity and community structure and in nitrogen cycling functional genes along a subalpine meadow degradation gradient on the Loess Plateau, China. Meadow degradation had a significant effect on the beta diversity of soil bacterial communities (P < 0.05) but not on the alpha diversity (P > 0.05). Nonmetric multidimensional scaling (NMDS) and analysis of similarity (ANOSIM) indicated that the compositions of bacterial and plant communities changed remarkably with increasing meadow degradation (all P < 0.05). The beta diversities of the plant and soil bacterial communities were significantly correlated (P < 0.05), while their alpha diversities were weakly correlated (P > 0.05) along the meadow degradation gradient. Redundancy analysis (RDA) showed that the structure of the bacterial community was strongly correlated with total nitrogen (TN), nitrate nitrogen (NO3−-N), plant Shannon diversity, plant coverage, and soil bulk density (all P < 0.05). Moreover, the abundances of N fixation and denitrification genes of the bacterial community decreased along the degradation gradient, but the abundance of nitrification genes increased along the gradient. The structure of the set of N cycling genes present at each site was more sensitive to subalpine meadow degradation than the structure of the total bacterial community. Our findings revealed compositional shifts in the plant and bacterial communities and in the abundances of key N cycling genes as well as the potential drivers of these shifts under different degrees of subalpine meadow degradation. IMPORTANCE Soil microbes play a crucial role in the biogeochemical cycles of grassland ecosystems, yet information on how their community structure and functional characteristics change with subalpine meadow degradation is scarce. In this study, we evaluated the changes in bacterial community structure and nitrogen functional genes in degraded meadow soils. Meadow degradation had a significant effect on bacterial community composition. Soil total nitrogen was the best predictor of bacterial community structure. The beta diversities of the plant and soil bacterial communities were significantly correlated, while their alpha diversities were only weakly correlated. Meadow degradation decreased the potential for nitrogen fixation and denitrification but increased the potential for nitrification. These results have implications for the restoration and reconstruction of subalpine meadow ecosystem on the Loess Plateau.