[Environmental selection and dispersal limitation drive the assemblage of bacterial community in temperate forest soils]. / 环境选择和扩散限制驱动温带森林土壤细菌群落的构建.

Environmental selection and dispersal limitation are two basic processes underlying community assembly. The relative importance of those two processes differs across scales, community identities, and community types. The processes responsible for structuring microbial communities in soil of temperate subalpine forest are poorly understood. Here, we investigated the relationship between soil bacterial community structure and environmental factors, and quantified the relative role of edaphic factors, vegetation, and spatial variables in shaping the structure of six soil bacterial communities (LpMC1, LpMC2, PwMC, PmMC, PtMC, and BMC) in five forest types including Larix principis-rupprechtii, Picea wilsonii, Picea meyeri, Pinus tabulaeformis, and Betula platyphylla in Pangquangou Nature Reserve by using PCR-DGGE technology. Our results showed that the structure and biodiversity of bacterial communities were significantly different among six communities. The biodiversity of bacterial community were higher in LpMC2 and PtMC, lowest in PmMC, and highest in LpMC1. Soil environmental factors, such as pH, soil water content, total carbon, total nitrogen, soil organic matter, available phosphorous, and soil enzymes, were significantly correlated with biodiversity and structure of soil bacterial community. The beta diversity of bacterial communities were significantly correlated with geographic distance, indicating the influence of dispersal limitation on the structure of bacterial community. The order of driving force on the structure of bacterial community was edaphic factors (0.27), spatial factor (0.19) and vegetation (0.15) in six samples. Using regional soil microbes from 10 samples around reserve as source community, results from the microcosm experiments showed that the edaphic factors were the predominant driving factors (0.35) on structure of artificial dispersal bacterial community, while the high diversity of source microbial community affected the structure of microcosm soil. In summary, at local scale, environmental selection predominantly determined the structural and biodiversity of soil bacterial communities in temperate subalpine forest, while dispersal limitation played a significant role. Such a result indicated that deterministic processes and stochastic processes played important roles in shaping the structure of soil bacterial community at local scale, with the former having the leading role. The composition of dispersal soil bacteria community was source-dependent but also modulated by local environmental selection.

[Characteristics of Fungi Community Structure and Genetic Diversity of Forests in Guandi Mountains].

Soil microorganisms drive the biogeochemical process of carbon, nitrogen, phosphorus and sulfur, and play a key role in maintaining soil carbon sink and ecosystem function. The study on effects of environmental and spatial factors on the structure of microbial community in boreal coniferous forest soil will provide theoretical basis for making management measures in local forest ecosystem. Our research analyzed five soil fungi communities (LpMC1, LpMC2, PwMC, PtMC, and BMC) in four forest types, including Larix principis-rupprechtii forest, Picea wilsonii forest, Pinus tabulaeformis forest and Betula spp. forest, respectively, in Pangquangou Nature Reserve in Guandi Mountains with Illumina high-throughput sequencing technology. Meanwhile, soil environmental factors and diversity of undergrowth plants were determined to analyze the relationship between fungi community structure and vegetation as well as soil environmental factors. The results showed that:①There were seven eumycota and thirty-three advantageous fungal genera in the five sample sites; ②Redundancy analysis results showed that soil pH, temperature, moisture, total nitrogen, the content of NH4+, total carbon, invertase activity, urease activity, undergrowth dominance and evenness were significantly associated with soil fungi community structure; ③Cluster analysis and principal component analysis showed that forest vegetation type, soil environmental factors and undergrowth had significant effects on soil fungi community structure; ④The results of PCNM analysis showed that at a local scale, dispersal limitation had no significant influence on fungi community structure in the study area. The forest soil fungi community structure in the study area was significantly affected by environmental selection (soil pH, temperature, moisture, total nitrogen, the content of NH4+, total carbon, invertase activity, urease activity, undergrowth dominance and evenness, forest type).

[Effects of organic manure on wheat growth under lead stress].

A pot experiment was conducted to study the effects of organic manure on the wheat growth under different levels of lead stress. With increasing lead stress level, whether fertilization or not, the plant height, shoot dry mass, adventitious root number, root total length, root dry mass, root activity, root total and active absorbing area, and root SOD and POD activities decreased, and root MDA content presented an increasing trend. The decrement of the above-mentioned parameters differed with fertilization treatments. Applying organic manure mitigated the impact of lead stress on wheat growth to some extent, delayed the senescence of wheat roots, and promoted root development and growth, ultimately leading to the increase of wheat yield and the decrease of lead content in grain.