Plant-microbial competition for nitrogen increases microbial activities and carbon loss in invaded soils
Plant-microbial competition for nitrogen increases microbial activities and carbon loss in invaded soils
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DOI：
10.1007/s00442-017-3861-0
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发表时间：
2017-07-01
期刊：
影响因子：
2.7
通讯作者：
Fraterrigo, Jennifer M.
中科院分区：
文献类型：
--
作者：
Craig, Matthew E.;Fraterrigo, Jennifer M.
许多入侵植物相对于其竞争对手表现出较高的养分获取率。然而，人们对这一现象背后的机制及其对生态系统功能的影响知之甚少，特别是在营养有限的系统中。在这里，我们验证了一个假设，即入侵植物物种（微stegium vimum）通过与土壤有机质降解微生物竞争氮来提高其氮(N)获取率，从而加速土壤N和碳(C)循环。我们估计了植物覆盖作为植物氮获取速率的指标，并量化了入侵和未入侵地块的植物组织氮、土壤C和N含量及其转化，以及胞外酶活性。在低环境氮有效性条件下，入侵样地植物盖度提高77%，组织碳氮比降低，表明入侵提高了植物氮获取率。与此同时，我们观察到入侵样地的质量比酶活性显著提高，长期氮有效性提高71%，短期氮有效性降低21%，颗粒有机质N降低16%。结构方程模型表明，这些变化与入侵区颗粒有机质C降低27%相关。我们的研究结果表明，这种植物对氮的获取增加了微生物对氮的需求，导致氮从有机形式到无机形式的通量增加和土壤C的损失。我们得出结论，入侵植物的高氮获取率可以驱动土壤氮循环的变化，这与土壤C的影响有关。
Many invasive plant species show high rates of nutrient acquisition relative to their competitors. Yet the mechanisms underlying this phenomenon, and its implications for ecosystem functioning, are poorly understood, particularly in nutrient-limited systems. Here, we test the hypothesis that an invasive plant species (Microstegium vimineum) enhances its rate of nitrogen (N) acquisition by outcompeting soil organic matter-degrading microbes for N, which in turn accelerates soil N and carbon (C) cycling. We estimated plant cover as an indicator of plant N acquisition rate and quantified plant tissue N, soil C and N content and transformations, and extracellular enzyme activities in invaded and uninvaded plots. Under low ambient N availability, invaded plots had 77% higher plant cover and lower tissue C:N ratios, suggesting that invasion increased rates of plant N acquisition. Concurrent with this pattern, we observed significantly higher mass-specific enzyme activities in invaded plots as well as 71% higher long-term N availability, 21% lower short-term N availability, and 16% lower particulate organic matter N. A structural equation model showed that these changes were interrelated and associated with 27% lower particulate organic matter C in invaded areas. Our findings suggest that acquisition of N by this plant species enhances microbial N demand, leading to an increased flux of N from organic to inorganic forms and a loss of soil C. We conclude that high N acquisition rates by invasive plants can drive changes in soil N cycling that are linked to effects on soil C.