Browsing by Author "Wu, Liyou"

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    The diversity and co-occurrence patterns of N2-fixing communities in a CO2-enriched grassland ecosystem
    (springer, 2016) Tu, Qichao; Zhou, Xishu; He, Zhili; Xue, Kai; Wu, Liyou; Reich, Peter B; Hobbie, Sarah; Zhou, Jizhong
    Diazotrophs are the major organismal group responsible for atmospheric nitrogen (N2) fixation in natural ecosystems. The extensive diversity and structure of N2-fixing communities in grassland ecosystems and their responses to increasing atmospheric CO2 remain to be further explored. Through pyrosequencing of nifH gene amplicons and extraction of nifH genes from shotgun metagenomes, coupled with co-occurrence ecological network analysis approaches, we comprehensively analyzed the diazotrophic community in a grassland ecosystem exposed to elevated CO2 (eCO2) for 12 years. Long-term eCO2 increased the abundance of nifH genes but did not change the overall nifH diversity and diazotrophic community structure. Taxonomic and phylogenetic analysis of amplified nifH sequences suggested a high diversity of nifH genes in the soil ecosystem, the majority belonging to nifH clusters I and II. Co-occurrence ecological network analysis identified different co-occurrence patterns for different groups of diazotrophs, such as Azospirillum/Actinobacteria, Mesorhizobium/Conexibacter, and Bradyrhizobium/Acidobacteria. This indicated a potential attraction of non-N2-fixers by diazotrophs in the soil ecosystem. Interestingly, more complex co-occurrence patterns were found for free-living diazotrophs than commonly known symbiotic diazotrophs, which is consistent with the physical isolation nature of symbiotic diazotrophs from the environment by root nodules. The study provides novel insights into our understanding of the microbial ecology of soil diazotrophs in natural ecosystems.
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    Elevated Carbon Dioxide Alters the Structure of Soil Microbial Communities
    (2012) Deng, Ye; He, Zhili; Xu, Meiying; Qin, Yujia; Van Nostrand, Joy D; Wu, Liyou; Roe, Bruce A; Wiley, Graham; Hobbie, Sarah E; Reich, Peter B; Zhou, Jizhong
    Pyrosequencing analysis of 16S rRNA genes was used to examine impacts of elevated CO2(eCO(2)) on soil microbial communities from 12 replicates each from ambient CO2(aCO(2)) and eCO(2) settings. The results suggest that the soil microbial community composition and structure significantly altered under conditions of eCO(2), which was closely associated with soil and plant properties.
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    Fungal communities respond to long-term CO2 elevation by community reassembly
    (2015) Tu, Qichao; Yuan, Mengting; He, Zhili; Deng, Ye; Xue, Kai; Wu, Liyou; Hobbie, Sarah E; Reich, Peter B; Zhou, Jizhong
    Fungal communities play a major role as decomposers in the Earth's ecosystems. Their community-level responses to elevated CO2 (eCO2), one of the major global change factors impacting ecosystems, are not well understood. Using 28S rRNA gene amplicon sequencing and co-occurrence ecological network approaches, we analyzed the response of soil fungal communities in the BioCON (biodiversity, CO2, and N deposition) experimental site in Minnesota, USA, in which a grassland ecosystem has been exposed to eCO2 for 12 years. Long-term eCO2 did not significantly change the overall fungal community structure and species richness, but significantly increased community evenness and diversity. The relative abundances of 119 operational taxonomic units (OTU; ∼27% of the total captured sequences) were changed significantly. Significantly changed OTU under eCO2 were associated with decreased overall relative abundance of Ascomycota, but increased relative abundance of Basidiomycota. Co-occurrence ecological network analysis indicated that eCO2 increased fungal community network complexity, as evidenced by higher intermodular and intramodular connectivity and shorter geodesic distance. In contrast, decreased connections for dominant fungal species were observed in the eCO2 network. Community reassembly of unrelated fungal species into highly connected dense modules was observed. Such changes in the co-occurrence network topology were significantly associated with altered soil and plant properties under eCO2, especially with increased plant biomass and NH4+ availability. This study provided novel insights into how eCO2 shapes soil fungal communities in grassland ecosystems.