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Stoichiometry constraints challenge the potential of agroecological practices for the soil C storage. A review
Agronomy for Sustainable Development ( IF 7.3 ) Pub Date : 2019-11-13 , DOI: 10.1007/s13593-019-0599-6
Isabelle Bertrand , Valérie Viaud , Tanguy Daufresne , Sylvain Pellerin , Sylvie Recous

To date, the stoichiometry concept has been poorly used to explore C, N, and P cycles in agroecosystems. As agriculture is now under pressure to reduce the use of synthetic inputs, ecological processes and alternative agricultural practices will become the main regulators of the relationships between C, N, and P and thereby of nutrient availability and C storage in soils. In this paper, we review the ecological theories underpinning the concepts of homeostasis and stoichiometric flexibility, their application to agroecosystems, and how stoichiometry could constraint agroecological practices related to nutrient availability and soil C storage. Our main findings are (1) optimal C:N:P ratios exist at the species level, reflecting a range of ecological strategies and representing a keystone constraint for the coupling of C, N, and P cycles, resulting in canonical ratios at the community level. Stoichiometric flexibility nevertheless exists from the organism level—autotrophs having higher flexibility than heterotrophs—to the community level, depending on assembly rules. (2) Agroecosystems are stoichiometrically constrained especially in the soil compartment, due to the low stoichiometric flexibility of microorganisms at the community level. (3) Agricultural practices such as fertilization decrease N:P ratios in soil surface when total P is considered, while C:N ratios remained constant. (4) Stoichiometry homeostasis constraints for soil C storage require the availability of N and P. They can be supported by agroecological practices that promote nutrient recycling (organic fertilization, permanent soil cover, N fixation). The 45-Tg N and 4.8-Tg P needed to increase the C stock of cropped soils by “4 per mille per year” can be also provided by suppressing nutrient losses. We conclude that two soil compartments should be more investigated to evaluate their potential to bypass stoichiometric constraints and foster C storage while reducing chemical inputs: deep soil horizons and particulate organic matter fraction.

中文翻译:

化学计量学上的限制挑战了农业生态实践对土壤碳存储的潜力。回顾

迄今为止,化学计量的概念已很少用于探索农业生态系统中的C,N和P循环。由于农业现在面临减少使用合成投入物的压力,因此生态过程和替代性农业实践将成为碳,氮和磷之间关系的主要调节者,从而成为土壤中养分有效性和碳储存的主要调节者。在本文中,我们回顾了基于动态平衡和化学计量灵活性概念的生态理论,它们在农业生态系统中的应用以及化学计量如何限制与养分有效性和土壤碳储存相关的农业生态实践。我们的主要发现是(1)最佳的C:N:P比存在于物种水平上,反映了一系列生态策略,并代表了C,N和P循环耦合的关键因素,导致社区一级的规范比率。然而,根据装配规则,从化学水平到自体水平比异养水平更高的自养生物到社区水平,存在化学计量的灵活性。(2)农业生态系统受到化学计量的限制,尤其是在土壤室内,这是由于微生物在群落水平上的化学计量柔韧性较低。(3)当考虑总磷时,施肥等农业实践会降低土壤表层的N:P比率,而C:N比率保持恒定。(4)土壤碳储存的化学计量稳态约束要求氮和磷的有效性。它们可以通过促进营养循环(有机肥,永久土壤覆盖,固氮)的农业生态实践得到支持。45 Tg N和4。通过抑制养分流失,还可以提供使作物土壤的碳储量增加“每年每百万米4”所需的8-TgP。我们得出结论,应进一步研究两个土壤隔间,以评估它们绕过化学计量约束和促进碳储存同时减少化学物质投入的潜力:深层土壤和有机质颗粒物。
更新日期:2019-11-13
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