[Distribution Characteristics and Source Apportionment of Perfluoroalkyl Substances in Surface Soils of the Northeast Tibetan Plateau].

Surface soil samples collected at 18 sites from the northeast Tibetan Plateau were used to analyze perfluoroalkyl substances (PFASs) via ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) to study the concentration levels and sources of PFASs. The results showed that 11 PFASs were detected in the soil, and the ω(Σ11PFASs) ranged from 0.043-1.573 ng·g-1 with an average concentration of 0.398 ng·g-1. PFBA displayed the highest concentration level with a mean content of 0.164 ng·g-1, whereas PFHxA was at the lowest level (0.005 ng·g-1). The concentrations of the other PFASs were similar to each other (0.011-0.057 ng·g-1). Generally, PFASs contents in the west and north were higher than that in the southeast, and the alpine condensation effect existed for PFBA. The principal component analysis showed that PFASs in surface soils in the northeast Tibetan Plateau region mainly originated from the atmospheric transport of PFASs and their precursors. Few areas were affected by direct emissions of point source pollution, and the main sources were the industrial production of metals/minerals and other human activities.

Effects of grazing patterns on grassland biomass and soil environments in China: A meta-analysis.

BACKGROUND: Grazing has important influences on the structures and functions of grassland ecosystems, but the effects of grazing patterns on grassland biomass and soil environments in China remain unclear. OBJECTIVE: We employed a meta-analysis to identify the response of biomass and soil environments to different grazing patterns in China. METHODS: Peer-reviewed journal articles were searched using the Web of Science and China National Knowledge to compile a database. A total of 1011 sets of sample observations satisfied the sampling standards; these were derived from 140 study sites and were obtained from 86 published articles. We conducted random effects meta-analyses and calculated correlation coefficients with corresponding 95% confidence intervals. RESULTS: Grazing significantly decreased the total biomass, aboveground biomass (AGB), belowground biomass (BGB), soil organic matter, soil total nitrogen, soil total phosphorus and soil water content but increased the root-to-shoot ratio, soil available nitrogen, soil pH and bulk density. Generally, increasing grazing intensity and duration significantly increased the effects of grazing on the biomass and soil environment. Additionally, the smallest effects of grazing on the biomass and soil environments were observed under light grazing and cattle grazing alone. Moreover, non-growing season grazing significantly increased AGB, while annual grazing and growing-season grazing significantly reduced AGB. Furthermore, AGB was positively correlated with soil organic matter, soil available phosphorus and bulk density, while BGB was negatively correlated with pH. CONCLUSIONS: These findings highlight the importance of grazing patterns in the biomass and soil environment response to grazing and suggest that cattle grazing alone and grazing during the non-growing season are beneficial for improving the quality of grassland in China.

[Neighborhood comparison of Cryptomeria fortunei plantation by using different variables].

Neighborhood comparison is defined as the proportion of the nearest greater neighbors to a given reference tree measured by a certain variable. By this way, the dominant differentiation degree of individual wood could be measured well. In this paper, the variables DBH, biomass, canopy breadth, and tree height were used to make the neighborhood comparison of Cryptomeria fortunei plantation in Chongzhou forest farm. The results showed that the neighborhood comparison measured by DBH and biomass had a slight fluctuation range and the highest reliability. Nevertheless, due to the effects of various tree types, the neighborhood comparison measured by canopy breath and tree height was not as reliable as that measured by the former two variables. The average value of the neighborhood comparison measured by DBH and biomass was visibly higher than that by canopy breath and tree height, indicating that the differentiation degree of individual's DBH and biomass was further greater than that of individual's canopy breath and tree height. It was possible that increasing individual's DBH to enhance its biomass, and thus, to achieve its predominance status among individuals' competition was the main strategy of individual's differentiation. Neighborhood comparison should also be taken as an instructive reference in modifying the spatial structure of stand.

[Resources utilization of main tree populations in Pinus armandii mixed forest after controlled burning and aerial-sowing afforestation].

In Hongchiba region of Wuxi County, the controlled burning and aerial sowing in 1972 rehabilitated degraded forest vegetations, and various types of Pinus armandii mixed communities were formed. By employing Petraitis' general and specific overlap indices, this paper analyzed the resources utilization of 10 main tree populations in Pinus armandii mixed forest. The results showed that Pinus armandii and most native trees had a wide niche breadth, and the interspecies general overlap value was 0.728, indicating that there was a fully and effective habitat resources utilization in the communities. The interspecies specific overlap value of Pinus armandii overlapping other native trees was very low, while that of native trees overlapping Pinus armandii was quite high, which demonstrated that the resources utilization and competition capability of Pinus armandii were weaker than those of native trees, and Pinus armandii population was at its inferior state during the process of their competitions. The interspecies specific overlap value between native trees was very low, generally because of their sound niche differentiation on resources utilization. As a result, the niche characteristics of native trees should be regarded as a favorable sample for the application of ecological rehabilitation and reconstruction. The advantages and disadvantages of Petraitis' overlap indices were discussed in this paper preliminarily.

[Community characteristics in Hongchiba area of Wuxi County during ecological restoration after controlled burning].

This paper studied the species composition and the structure and species diversity of communities in Hongchiba area of Wuxi County after controlled burning and aerial-sowing afforestation. The results showed that after burning and afforestation, pure Pinus armandii forest was not developed, but various mixed needle board-leaved forests which comprised P. armandii and native board-leaved trees grew. Various native species contributed to the communities with great species diversity. Shannon-Wiener index was 2.305-3.145, ecological dominance was 0.063-0.151, and evenness was 0.600-0.749. The natural regeneration of P. armandii population was very poor, and there was a trend that P. armandii would be gradually replaced by other native board-leaved trees. It was demonstrated that P. armandii should not be taken as a unique afforest tree, and controlled burning was not a favorite ecological measure in subtropical area. Native trees should play more important roles in the process of ecological restoration.