Key Laboratory of Ecosystem Network Observation and Modelling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences (CAS), PO Box 9725, Beijing, 100101, China.
Department of Soil Science of Temperate Ecosystems, Göttingen, Germany.
New Phytol. 2013 May;198(3):656-669. doi: 10.1111/nph.12235. Epub 2013 Mar 22.
Demand of all living organisms on the same nutrients forms the basis for interspecific competition between plants and microorganisms in soils. This competition is especially strong in the rhizosphere. To evaluate competitive and mutualistic interactions between plants and microorganisms and to analyse ecological consequences of these interactions, we analysed 424 data pairs from 41 (15)N-labelling studies that investigated (15)N redistribution between roots and microorganisms. Calculated Michaelis-Menten kinetics based on K(m) (Michaelis constant) and V(max) (maximum uptake capacity) values from 77 studies on the uptake of nitrate, ammonia, and amino acids by roots and microorganisms clearly showed that, shortly after nitrogen (N) mobilization from soil organic matter and litter, microorganisms take up most N. Lower K(m) values of microorganisms suggest that they are especially efficient at low N concentrations, but can also acquire more N at higher N concentrations (V(max)) compared with roots. Because of the unidirectional flow of nutrients from soil to roots, plants are the winners for N acquisition in the long run. Therefore, despite strong competition between roots and microorganisms for N, a temporal niche differentiation reflecting their generation times leads to mutualistic relationships in the rhizosphere. This temporal niche differentiation is highly relevant ecologically because it: protects ecosystems from N losses by leaching during periods of slow or no root uptake; continuously provides roots with available N according to plant demand; and contributes to the evolutionary development of mutualistic interactions between roots and microorganisms.
所有生物体对同一养分的需求构成了植物和土壤微生物之间种间竞争的基础。这种竞争在根际尤为强烈。为了评估植物和微生物之间的竞争和互利相互作用，并分析这些相互作用的生态后果，我们分析了来自 41 项（15）N 标记研究的 424 对数据，这些研究调查了根和微生物之间（15）N 的再分配。根据 77 项关于根和微生物对硝酸盐、氨和氨基酸吸收的 K(m)（米氏常数）和 V(max)（最大吸收能力）值计算的米氏门控动力学，清楚地表明，在土壤有机质和凋落物中氮从有机态动员后不久，微生物就吸收了大部分氮。微生物较低的 K(m)值表明，它们在低氮浓度下特别有效，但与根相比，它们也可以在较高的氮浓度（V(max)）下获得更多的氮。由于养分从土壤单向流向根，植物从长期来看是氮获取的赢家。因此，尽管根和微生物之间存在强烈的氮竞争，但反映它们世代时间的时间生态位分化导致了根际的互利关系。这种时间生态位分化在生态学上具有高度相关性，因为它：在根系吸收缓慢或没有吸收的时期，防止生态系统因淋失而损失氮；根据植物的需求，持续为根系提供可用的氮；并有助于根和微生物之间互利相互作用的进化发展。
