Plant roots interact with rhizosphere microorganisms to accelerate soil organic matter (SOM) mineralization for nutrient acquisition. Root‐mediated changes in SOM mineralization largely depend on root‐derived carbon (root‐C) input and soil nutrient status. Hence, intraspecific competition over plant development and spatiotemporal variability in the root‐C input and nutrients uptake may modify SOM mineralization. To investigate the effect of intraspecific competition on SOM mineralization at three growth stages (heading, flowering, and ripening), we grew maize (C4 plant) under three planting densities on a C3 soil and determined in situ soil C‐ and N‐mineralization by ¹³C‐natural abundance and ¹⁵N‐pool dilution approaches. From heading to ripening, soil C‐ and N‐mineralization rates exhibit similar unimodal trends and were tightly coupled. The C‐to‐N‐mineralization ratio (0.6 to 2.6) increased with N availability, indicating that an increase in N‐mineralization with N depletion was driven by microorganisms mining N‐rich SOM. With the intraspecific competition, plants increased specific root lengths as an efficient strategy to compete for resources. Root morphologic traits rather than root biomass per se were positively related to C‐ and N‐mineralization. Overall, plant phenology and intraspecific competition controlled the intensity and mechanisms of soil C‐ and N‐ mineralization by the adaptation of root traits and nutrient mining.

中文翻译：

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植物种内竞争和生长阶段改变根际碳和氮的矿化

植物根系与根际微生物相互作用以加速土壤有机质 (SOM) 矿化以获取养分。根介导的 SOM 矿化变化很大程度上取决于根源性碳 (root-C) 输入和土壤养分状况。因此，植物发育的种内竞争以及根碳输入和养分吸收的时空变异可能会改变 SOM 矿化。为了研究种内竞争对三个生长阶段（抽穗、开花和成熟）SOM 矿化的影响，我们在 C3 土壤上以三种种植密度种植玉米（C4 植物），并通过以下方法确定原位土壤 C 和 N 矿化¹³ C-自然丰度和¹⁵N池稀释方法。从抽穗到成熟，土壤 C 和 N 矿化率表现出类似的单峰趋势并且紧密耦合。C 与 N 矿化比（0.6 到 2.6）随着 N 可用性的增加而增加，表明 N 矿化随着 N 消耗的增加是由微生物开采富含 N 的 SOM 驱动的。随着种内竞争，植物增加特定根长作为竞争资源的有效策略。根系形态特征而非根系生物量本身与 C 和 N 矿化呈正相关。总体而言，植物物候学和种内竞争通过适应根性状和养分挖掘来控制土壤碳和氮矿化的强度和机制。