Constraining Carbon and Nutrient Flows in Soil With Ecological Stoichiometry
Constraining Carbon and Nutrient Flows in Soil With Ecological Stoichiometry
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DOI：
10.3389/fevo.2019.00382
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发表时间：
2019-10-10
影响因子：
3
通讯作者：
Keiser, Ashley D.
中科院分区：
文献类型：
--
作者：
Buchkowski, Robert W.;Shaw, Alanna N.;Keiser, Ashley D.
土壤有机质（SOM）是土壤碳储量和陆地养分循环的核心。新的研究结果颠覆了传统的稳定化模型，即认为稳定的有机质主要由未分解的植物分子组成。我们现在知道，微生物的副产品和死细胞组成了意想不到的大量稳定的SOM，因为它们可以附着在矿物表面或在土壤团聚体中受到物理保护。SOM模型已经建立，将微生物的矿物稳定的有机质，但现在面临着一个新的挑战，准确地捕捉微生物的生产力和代谢。化学计量学，即生物体生长和维持的相对营养需求，可以提供一条前进的道路。化学计量限制了自然界中SOM的形成和周转，但新一代SOM模型中往往缺少氮（N）、磷（P）和硫（S）等重要营养物质。在这种合成中，我们试图促进这些营养物质的SOM模型（1）审查化学计量偏差的倾向，有利于一个元素超过另一个SOM循环的新框架中的四个关键过程和（2）应用这些知识来建立一个化学计量明确的预算的C，N，P，和S流通过主要SOM池。通过量化化学计量在SOM循环中的作用，我们发现，限制微生物和SOM的C：N：P：S比为特定值，可以有效地降低C和营养流的不确定性，因为使用微生物C利用效率（CUE）参数。我们发现，化学计量与CUE的附加约束的价值在不同的生态系统，这取决于如何精确的可用数据是该生态系统和生物地球化学途径。此外，由于CUE总结了许多不同的过程，化学计量测量的关键土壤池很可能是更强大的外推时，从土壤培养的情节或生物群落规模的估计。我们的研究结果表明，测量SOM的化学计量应该是未来的经验工作的优先事项，包括新的营养物质在SOM模型可能是一种有效的方法，以提高精度。
Soil organic matter (SOM) is central to soil carbon (C) storage and terrestrial nutrient cycling. New data have upended the traditional model of stabilization, which held that stable SOM was mostly made of undecomposed plant molecules. We now know that microbial by-products and dead cells comprise unexpectedly large amounts of stable SOM because they can become attached to mineral surfaces or physically protected within soil aggregates. SOM models have been built to incorporate the microbial to mineral stabilization of organic matter, but now face a new challenge of accurately capturing microbial productivity and metabolism. Explicitly representing stoichiometry, the relative nutrient requirements for growth and maintenance of organisms, could provide a way forward. Stoichiometry limits SOM formation and turnover in nature, but important nutrients like nitrogen (N), phosphorus (P), and sulfur (S) are often missing from the new generation of SOM models. In this synthesis, we seek to facilitate the addition of these nutrients to SOM models by (1) reviewing the stoichiometric bias-the tendency to favor one element over another-of four key processes in the new framework of SOM cycling and (2) applying this knowledge to build a stoichiometrically explicit budget of C, N, P, and S flow through the major SOM pools. By quantifying the role of stoichiometry in SOM cycling, we discover that constraining the C:N:P:S ratio of microorganisms and SOM to specific values reduces uncertainty in C and nutrient flow as effectively as using microbial C use efficiency (CUE) parameters. We find that the value of additional constraints on stoichiometry vs. CUE varies across ecosystems, depending on how precise the available data are for that ecosystem and which biogeochemical pathways are present. Moreover, because CUE summarizes many different processes, stoichiometric measurements of key soil pools are likely to be more robust when extrapolated from soil incubations to plot or biome scale estimates. Our results suggest that measuring SOM stoichiometry should be a priority for future empirical work and that the inclusion of new nutrients in SOM models may be an effective way to improve precision.