Grass encroachment in heathland and microbial community structure

In many ecosystems, the identity of the dominant plant is changing because of global change. If the new dominant species has different litter and root traits than the one it replaces, it is likely to have an influence on soil microbial communities and the functions they perform. We established a 13-plot field observatory spanning across a 0-100% gradient of grasscover percentage. In each plot, we characterized amongst others, plant, fungal and bacterial communities, using metabarcoding. Our results showed that microbial taxonomic and functional diversities are not affected by grass colonization. Microbial communities were also similar at high phylogenetic level, including for ericoid mycorrhizas and typical oligo- and copiotrophic species. At a finerphylogenetic level, some abundant extremophilic OTUs ( e.g Acidothermus bacteria) were progressively replaced by fungal black yeasts. Functional response of microbial communities was more obvious. The C mineralization potential significantly increased across the grass gradient.

受全球变化影响，诸多生态系统中的优势植物类群正发生更替。若新优势种与其所取代的原有物种在凋落物与根系性状上存在差异，则很可能会对土壤微生物群落及其执行的生态功能产生影响。本研究搭建了包含13个样地的野外观测平台，覆盖0至100%的草本覆盖度梯度。在每个样地中，我们借助宏条形码（metabarcoding）技术对植物、真菌与细菌群落等进行了表征分析。研究结果表明，草本定植并未对微生物的分类多样性与功能多样性产生显著影响。在较高的系统发育水平上，微生物群落结构也表现出相似性，涵盖杜鹃花类菌根以及典型的贫营养与富营养微生物类群。而在精细系统发育水平下，部分丰度较高的嗜极端环境操作分类单元（OTUs，如嗜酸热菌属（Acidothermus）细菌）逐渐被真菌黑色酵母菌所取代。微生物群落的功能响应则更为显著：随草本覆盖度梯度升高，碳矿化潜力显著提升。