Factors driving the biomass and species richness of desert plants in northern Xinjiang China.

The desert ecosystem is an important part of the terrestrial ecosystem. Accurate estimations of the biomass and species richness of desert plants are of great value for maintaining ecosystem stability; however, current assessments remain a challenge due to the large spatial heterogeneity in biomass and species richness and difficulties posed by time-consuming field surveys, particularly in remote areas. In the present study, There were 527 sampling sites, and each sampling site contained approximately 9 quadrats. Approximately 4500 quadrats in total were taken from the Junggar Desert of northern Xinjiang, and the spatial distribution and factors driving the biomass and species richness of the desert ecosystem were quantitatively analyzed. The results showed that the average aboveground biomass, belowground biomass, litter, and the Patrick index of the Junggar Desert in northern Xinjiang were 115.42 gm-2, 924.77 gm-2, 13.06 gm-2, and 63, with values ranging from 2-708.12 gm-2, 120.25-3537.3 gm-2, 2-56.46 gm-2, and 0-377, respectively, The mean of the variation coefficient was 56.19%, 41.16%, 62.16% and 73.83%, suggesting moderate variation. The result is affected by the differences between the desert environment and climate. Climate factors had a relatively large impact on species richness, and the variation coefficient of species richness was large, indicating a large degree of dispersion of species richness. The direct influence of environmental and climatic factors on underground biomass (BGB) is relatively small, and its coefficient of variation is small. The spatial distribution of biomass and species richness in northern Xinjiang gradually decreased from west to east. Redundancy analysis showed that climate was the main factor driving desert biomass and species richness in northern Xinjiang, with an average independent explanatory power of 20.38% and 18.57%, respectively. Structural equation modeling indicated that climate factors, elevation, and community coverage had a direct positive effect on the aboveground biomass of the desert plants in northern Xinjiang and a direct negative effect on the belowground biomass. Moreover, climate factors and biological factors showed a direct positive effect on the species richness in northern Xinjiang.

[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.