Apr 2020, Volume 2 Issue 1

Cover illustration

  • How species assemble into a community? This is a key topic of community ecology and biodiversity conservation. Though soil biodiversity is one of the largest reservoirs of biodiversity on earth, our understanding of how this hidden biodiversity is shaped is still limited. Ground-dwelling beetles are widely distributed and charismatic model organisms in biodiversity and conservation studies. The cover article aimed to uncover the processes that shape ground-dwelling beetle p [Detail] ...

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    Yong-Guan Zhu
    Philippe C. Baveye
    Peng Cai, Yichao Wu, Marc Redmile-Gordon
    Jie-liang Liang, Jun Liu, Tao-tao Yang, Pan-deng Wang, Sheng-chang Zhang, Pu Jia, Bin Liao, Wen-sheng Shu, Jin-tian Li

    Little is known about the responses of soil fungal communities to revegetation of mine wastelands, representing a major gap in the knowledge needed to improve the performances of revegetation schemes for mine wastelands. To shed some light on this matter, we re-established 4000 m2 of vegetation on an extremely acidic (pH 2.5) copper mine tailings pond and collected soil samples from three different types of habitats: amended layer of the reclaimed tailings (ALRT), unamended layer of the reclaimed tailings (ULRT), and unreclaimed tailings (UT). Soil fungal communities in the 120 samples collected in two consecutive years were characterized via high-throughput sequencing. The fungal diversities at ALRT and ULRT were found to be significantly higher than those at UT. Ascomycota whose relative abundance ranged from 74.5% to 98.4% was the most predominant phylum across all habitats, exhibiting the lowest predominance at ALRT. Two acidophilic fungal genera, Acidomyces and Acidiella, dominated UT with relative abundances being as high as 37.8% and 15.2%, respectively. In contrast, three genera with plant growth-promoting species (Talaromyces, Trichoderma and Penicillium) were abundant at ULRT and ALRT. Remarkably, their relative abundances at ULRT could be up to 29.0%, 26.9% and 9.7%, respectively. The three types of habitats differed considerably in the overall soil fungal community composition at species level, which became more pronounced as time progressed. The abovementioned differences between habitats in soil fungal community features were related to the reduced availability of soil copper and zinc. These results improved our understanding of fungal ecology of mine wastelands.

    Aihua Zhao, Lei Liu, Baodong Chen, Wei Fu, Wei Xie, Tianle Xu, Wei Zhang, Qing Ye, Haiyan Feng, Shenglei Fu

    Nitrogen (N) deposition and intensified rainfall can strongly affect soil microbial community, but compared with available studies on bacteria, those on soil fungi are quite limited. Here we carried out a field experiment in a mixed deciduous forest of China to study the influences of increased N deposition and rainfall on soil fungi by using quantitative PCR and high-throughput sequencing method. The results demonstrated that (1) N addition significantly increased fungal abundance and alpha diversity (richness, Shannon index and Invsimpson index), changed fungal community composition at OTU level, and marginally increased the relative abundance of Ascomycota and Zygomycota, while water addition showed no remarkable effects on fungal abundance, biodiversity and community composition. (2) N addition significantly increased the richness of saprotrophic fungi and pathogenic fungi, and the relative abundance of saprotrophic fungi, but water addition only slightly increased the abundance of pathogenic fungi. (3) Fungal composition dissimilarity closely correlated with the disparity of soil parameters as a whole. Soil NH4+-N exhibited strong positive correlation with the richness of pathogenic fungi and mycorrhizal fungi, while both soil moisture and NH4+-N tightly correlated with soil fungal abundance and alpha diversity indices. We concluded that in this N-limited but non-water-limited forest ecosystem, N deposition posed stronger effects on soil fungi than increased rainfall, partially mediated by changes in soil properties.

    Jiangnan Li, Peiqin Peng, Jie Zhao

    Although soil nematode diversity has been used as an indicator of habitat characteristics and environmental change, the diversity of entire soil nematode communities has not been comprehensively evaluated at different taxonomic levels, or for different functional groups, or at a fine taxonomic level within functional groups. In this study, two taxonomic diversity indices, the Shannon-Wiener index (H′) and Simpson index (l), were used to evaluate the following: 1) nematode diversity at different taxonomic levels for the whole community, 2) nematode diversity of different functional groups, and 3) nematode generic diversity of functional groups in the following four land-use types: forage land, cropland, secondary forest, and grass-shrubland. The results showed that significant differences in nematode diversity among land-use types were detected by assessment at the order level but not at the family or genus level. The results also showed that significant differences in nematode diversity were better revealed by assessment of trophic groups rather than cp groups. The generic diversities (H′) of omnivorous nematodes and cp3 nematodes also significantly differed among land-use types. Our results indicate that diversity at a high taxonomic level (i.e., order) may be a more useful indicator than diversity at a low taxonomic level (i.e., family or genus) of differences among land-use types. In addition, the functional group diversity (i.e., trophic group, cp group, and the combination of these two groups) for the whole community and the taxonomic diversity within functional groups were useful indicators of differences among land-use types.

    Manuel Aira, Jorge Domínguez

    Here we studied whether soil systems differ if they are under the influence of live (plants) or dead organic matter systems (nest) in terms of C and N mineralization, microbiological characteristics and nematode trophic group structure. We analyzed physicochemical and microbiological properties of soils inside and outside nests of the European shag (Phalacrocorax aristotelis, L.) on the Cíes Islands (NW Spain). We sampled fresh soil below dead (nests) and live organic matter (plants) (paired samples, n=7). Soil of nests had lower organic matter and higher electric conductivity and dissolved organic C and extractable N contents than the soil of plants. Microbial biomass and activity were greater in soil of nests than in soil of plants. The abundance of nematode trophic groups (bacterivores, fungivores, omnivores and herbivores) differred between soils of nests and plants, and the soil of plants supported a more abundant and diverse nematode community. The present results points to that source of organic matter promote differences in the decomposer community, being more efficient in soil of nests because C mineralization is greater. Further, this occurred independently of the complexity of the systems, higher in the soil of plants with more groups of nematodes.

    Meixiang Gao, Zhihong Qiao, Hongyu Hou, Guangze Jin, Donghui Wu

    Disentangling the relative roles of environmental and spatial processes in community assembly is a major task of community ecology. It is necessary to uncover this question at multiple spatial scales; however, the relative importance of spatial and environmental processes on ground-dwelling beetle assembly at a small scale is still unclear. Based on two permanent plots (each 300 m) located in primary mixed broadleaved-Korean pine forests, the topographic, soil, and plant factors were collected, and the spatial variables (MEMs, distance-based Moran’s eigenvector maps) were calculated. A redundancy analysis (RDA) was used to evaluate the influence of topographic, soil, and plant variables on ground-dwelling beetle compositions. A variation partitioning analysis was used to quantify the relative contributions of environmental and spatial processes on the assembly of ground-dwelling beetles. The results of the RDA reported that the soil, plant, and topographic variables affected Staphylinidae and Silphidae beetle compositions in both plots. According to the results of variation partitioning, pure soil and plant variables were important for the assembly of Silphidae beetles in the LS plot. The contributions of pure topographic, soil, and plant variables were significantly lower than those of pure spatial variables. The contributions of pure spatial variables were significant for the assembly of Staphylinidae and Silphidae beetles in both plots. In addition, the relative importance of environmental and spatial processes was not significantly changed after including more environmental variables and the unexplained variations. Finally, this study suggests that both spatial and environmental variables are important for the assembly of ground-dwelling beetle communities, while pure spatial variables are more important than pure environmental variables at a small scale (300 m).

    Weiwei Dai, Edith Bai, Wei Li, Ping Jiang, Guanhua Dai, Xingbo Zheng

    Soil-emitted N2O contributes to two-thirds of global N2O emissions, and is sensitive to global change. We used DayCent model to simulate major plant–soil N cycling processes under different global change scenarios in a typical temperate mixed forest in north-eastern China. Simulated scenarios included warming (T), elevated atmospheric CO2 concentration ([CO2]) (C), increased N deposition (N) and precipitation (P), and their full factorial combinations. The responses of plant–soil nitrogen cycling processes including net N mineralization, plant N uptake, gross nitrification, denitrification and soil N2O emission were examined. Concurrent increase of elevated [CO2] and N deposition displayed most strong interactive effects on most fluxes. Using the results from experimental studies for evaluation, simulation uncertainty was highest under elevated [CO2] and increased precipitation among the four global change factors. N deposition had a fundamental impact on soil N cycle and N2O emission in our studied forest. Despite forest soil acting as a N sink for added N, scenarios which included increased N deposition showed higher cumulative soil N2O emissions (summed up from 2001 to 2100). In particular, the scenario which included T, P, and N had the largest cumulative soil N2O emission, which was a 24.4% increase over that under ambient conditions. Our study points to the importance of the interactive effects of global change factors on plant–soil N cycling and the necessity of multi-factor manipulation experiments.