Effects of grazing exclusion on soil properties, fungal community structure, and diversity in different grassland types.

Soil fungi are involved in the decomposition of organic matter, and they alter soil structure and physicochemical properties and drive the material cycle and energy flow in terrestrial ecosystems. Fungal community assembly processes were dissimilar in different soil layers and significantly affected soil microbial community function and plant growth. Grazing exclusion is one of the most common measures used to restore degraded grasslands worldwide. However, changes in soil fungal community characteristics during grazing exclusion in different types of grasslands are unknown. Here, we investigated the effects of a 9-year grazing exclusion on soil properties, fungal community composition, and diversity in three grassland types (temperate desert, temperate steppe, and mountain meadow). The results showed that (1) in the 0-5 cm soil layer, grazing exclusion significantly increased the differences in SWC, SOC, KN, and N:P among the three grassland types, while the final pH, BD, TP, C:N, and C:P values were consistent with the results before exclusion. In the 5-10 cm soil layer, grazing exclusion significantly increased total phosphorus (TP) in temperate deserts by 34.1%, while significantly decreasing bulk density (BD) by 9.8% and the nitrogen: phosphorus ratio (N:P) by 47.1%. (2) The soil fungal community composition differed among the grassland types, For example, significant differences were found among the three grassland types for the Glomeromycota and Mucoromycota. (3) Under the influence of both grazing exclusion and grassland type, there was no significant change in soil fungal alpha diversity, but there were significant differences in fungal beta diversity. (4) Grassland type was the most important factor influencing changes in fungal community diversity, and vegetation cover and soil kjeldahl nitrogen were the main factors influencing fungal diversity. Our research provides a long-term perspective for better understanding and managing different grasslands, as well as a better scientific basis for future research on grass-soil-microbe interactions.

Dynamic characteristics and driving factors of vegetation greenness under changing environments in Xinjiang, China.

Global environment changes rapidly alter regional hydrothermal conditions, which undoubtedly affects the spatiotemporal dynamics of vegetation, especially in arid and semi-arid areas. However, identifying and quantifying the dynamic evolution and driving factors of vegetation greenness under the changing environment are still a challenge. In this study, gradual trend analysis was applied to calculate the overall spatiotemporal trend of the normalized difference vegetation index (NDVI) time series of Xinjiang province in China, the abrupt change analysis was used to detect the timing of breakpoint and trend shift, and two machine learning methods (boosted regression tree and random forest) were used to quantify the key factors of vegetation change and their relative contribution rate. The results have shown that vegetation has experienced overall recovery over the past 20 years in Xinjiang, and greenness increased at a rate of 17.83 10-4 year-1. Cropland, grassland, and sparse vegetation were the main biome types where vegetation restoration is happening. Nearly 10% of the pixels (about 166000 km2) were detected to have breakpoints from 2004 to 2016 of the monthly NDVI, and most of the breakpoints were concentrated in the ecotone of various biomes. CO2 concentration was the most prevalent environmental factor to increase vegetation greenness, because continuous emission of CO2 greatly enhanced the fertilization effect, further promoted vegetation growth. Besides, cropland expansion and desertification control were the vital anthropogenic factors to vegetation turning "green" in Xinjiang, and most areas under anthropogenic were mainly in oasis areas. These findings provide new insights and measures for the regional response strategies and terrestrial ecosystem protection.

[Relationship between post-traumatic stress disorder and perceived social support among middle school students in Wenchuan earthquake-stricken].

OBJECTIVE: To explore the relationship between post-traumatic stress disorder (PTSD) and perceived social support (PSS) ability among middle school students in earthquake-stricken areas after the Wenchuan earthquake accident. METHODS: A total of 1966 students from three secondary schools of Wenchuan earthquake-stricken areas were evaluated by PTSD Checklist-Civilian Version (PCL-C) and Perceived Social Support Scale (PSSS). RESULTS: The overall incidence rate of PTSD was 78.3%, with severe PTSD as 24.38%. Significant differences on the incidence rates of PTSD were found among the students who were in different PSS levels (P < 0.05) and significant negative correlation existed between the levels of severity on PTSD and PSS (gamma = -0.226, P < 0.05). Significant differences on PTSD incidence rates were found among those students who were from different families or out-family PSS levels (P = 0.009, P < 0.05). Significant negative correlation existed between the severity of PTSD and family or out-family PSS level (gamma = -0.176, P < 0.05, gamma = -0.214, P < 0.05). CONCLUSION: Relationships between the incidence rate, severity of PTSD and PSS levels existed among the middle school students in Wenchuan earthquake-stricken areas, with higher PSS, lower incidence rate and lighter severity of PTSD. Psychological intervention for earthquake-stricken students should be carried out.