Nitrogen addition regulates soil nematode community composition through ammonium suppression.
Nitrogen addition regulates soil nematode community composition through ammonium suppression.
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DOI：
10.1371/journal.pone.0043384
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发表时间：
2012
期刊：
影响因子：
3.7
通讯作者：
Han X
中科院分区：
文献类型：
--
作者：
Wei C;Zheng H;Li Q;Lü X;Yu Q;Zhang H;Chen Q;He N;Kardol P;Liang W;Han X
人类活动导致的氮(N)富集极大地改变了土壤群落的组成和功能。线虫是土壤生物中数量最多、种类最多的一类，在土壤碎屑食物网中占有重要的营养地位。因此，线虫被认为是富氮条件下土壤生态系统功能变化的有用指标。采用多尺度施氮试验，对内蒙古草原土壤线虫群落的时间动态进行了监测。测量是在实验开始三年后进行的。利用结构方程模型（SEM）探讨了线虫对氮富集反应的调控机制。在整个N富集梯度中，8月份线虫总丰度、多样性（H′和分类丰富度）、成熟度指数（MI）以及根食、真菌和杂食-捕食者丰度均显著降低。根系食草动物在9月恢复，这是线虫总丰度在N梯度上的时间变化。在8月和9月，细菌食用量与N添加速率呈驼峰型关系。8月铵态氮浓度与总线虫和草食性线虫丰度呈负相关，9月不呈负相关。铵抑制解释了61%的线虫丰富度变异和43%的线虫营养类群组成变异。草食线虫以根液为食时可能发生铵中毒，这可能解释了8月份草食线虫与铵浓度呈负相关关系的原因。我们发现真菌食材与真菌磷脂脂肪酸（PLFA）之间存在显著的正相关关系，表明真菌食材存在自下而上的控制。在细菌性线虫和细菌PLFA之间没有发现这种关系。本研究结果有助于了解半干旱草地富氮对土壤线虫营养类群的影响，以及碎屑土壤食物网的级联效应。
Nitrogen (N) enrichment resulting from anthropogenic activities has greatly changed the composition and functioning of soil communities. Nematodes are one of the most abundant and diverse groups of soil organisms, and they occupy key trophic positions in the soil detritus food web. Nematodes have therefore been proposed as useful indicators for shifts in soil ecosystem functioning under N enrichment. Here, we monitored temporal dynamics of the soil nematode community using a multi-level N addition experiment in an Inner Mongolia grassland. Measurements were made three years after the start of the experiment. We used structural equation modeling (SEM) to explore the mechanisms regulating nematode responses to N enrichment. Across the N enrichment gradient, significant reductions in total nematode abundance, diversity (H' and taxonomic richness), maturity index (MI), and the abundance of root herbivores, fungivores and omnivores-predators were found in August. Root herbivores recovered in September, contributing to the temporal variation of total nematode abundance across the N gradient. Bacterivores showed a hump-shaped relationship with N addition rate, both in August and September. Ammonium concentration was negatively correlated with the abundance of total and herbivorous nematodes in August, but not in September. Ammonium suppression explained 61% of the variation in nematode richness and 43% of the variation in nematode trophic group composition. Ammonium toxicity may occur when herbivorous nematodes feed on root fluid, providing a possible explanation for the negative relationship between herbivorous nematodes and ammonium concentration in August. We found a significantly positive relationship between fungivores and fungal phospholipid fatty acids (PLFA), suggesting bottom-up control of fungivores. No such relationship was found between bacterivorous nematodes and bacterial PLFA. Our findings contribute to the understanding of effects of N enrichment in semiarid grassland on soil nematode trophic groups, and the cascading effects in the detrital soil food web.
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