Stoichiometric controls upon low molecular weight carbon decomposition
Stoichiometric controls upon low molecular weight carbon decomposition
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DOI：
10.1016/j.soilbio.2014.08.019
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发表时间：
2014-12
影响因子：
9.7
通讯作者：
C. Creamer;Davey L. Jones;J. Baldock;M. Farrell
中科院分区：
文献类型：
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作者：
C. Creamer;Davey L. Jones;J. Baldock;M. Farrell
土壤碳（C）和氮（N）循环有着千丝万缕的联系，但氮的有效性对土壤C固存和周转的影响知之甚少。根据化学计量理论，在没有养分限制的情况下，基质分解将达到最大速率，以CO2产生为代价将C同化为微生物生物量。在这项研究中，我们添加了一个14 C标记的低分子量底物（葡萄糖）的桑迪土壤沿着与11个增加水平的N，磷（P），硫（S）的相对比例所需的微生物生物量的生产。添加一个简单的可溶性底物，使我们能够明确检查添加C的微生物转化的变化，而不是由胞外酶活性或底物分解的程度引起的变化。我们假设，随着养分添加量的增加，所提供的葡萄糖-C的比例增加，将被纳入微生物生物量的CO2生产的代价和稳定的土壤有机碳（SOC）。相反，从葡萄糖-C的CO2生产增加显着与营养素添加没有可测量的变化，葡萄糖衍生的微生物生物量或SOC。这表明，如果有更大的葡萄糖衍生的微生物生物量下产生的更高的营养素添加它是由微生物生物量周转率较高的抵消。我们还发现，更大的土壤来源的微生物生物量在较低的养分添加水平，潜在的支持土壤有机质（SOM）的微生物开采的概念，在低养分供应的养分。总之，我们的数据表明，在一个桑迪土壤的SOM的物理保护能力低，养分添加并没有立即促进土壤微生物群落中的C封存，和C稳定和养分添加之间的相互作用需要进一步的工作，特别是预测生态系统的响应。
Soil carbon (C) and nitrogen (N) cycles are inextricably linked, yet the impacts of N availability upon soil C sequestration and turnover are poorly understood. According to stoichiometric theory, in the absence of nutrient limitation substrate decomposition will reach maximum rates, with C assimilated into microbial biomass at the expense of CO2production. In this study, we added a14C labelled low molecular weight substrate (glucose) to a sandy soil along with eleven increasing levels of N, phosphorus (P), and sulphur (S) in relative proportions as required for microbial biomass production. Adding a simple soluble substrate allowed us to explicitly examine changes in microbial transformations of added C, rather than changes resulting from extracellular enzyme activity or the extent of substrate decomposition. We hypothesized that as nutrient addition increased, an increasing proportion of the glucose-C provided would be incorporated into microbial biomass at the expense of CO2production and stabilized as soil organic carbon (SOC). Instead, CO2production from glucose-C increased significantly with nutrient addition without measurable changes in glucose-derived microbial biomass or SOC. This suggests that if there was greater glucose-derived microbial biomass produced under higher nutrient addition it was offset by a higher rate of microbial biomass turnover. We also found greater soil-derived microbial biomass at lower nutrient addition levels, potentially supporting the concept of microbial mining of soil organic matter (SOM) for nutrients under low nutrient availability. In conclusion, our data suggest that in a sandy soil with low capacity for physical protection of SOM, nutrient addition does not immediately promote C sequestration in the soil microbial community, and that the interaction between C stabilization and nutrient addition requires further work, especially for predicting ecosystem responses.