Phosphorus supply increases nitrogen transformation rates and retention in soil: a global meta-analysis

Interactions between nitrogen (N) and phosphorus (P) are important for
plant growth and ecosystem carbon (C) sequestration. While effects of N
supply on P dynamics have been much studied, much less is known about the
opposite (P-effect on N). We conducted a meta-analysis by compiling a
total of 1734 individual experimental observations from 116 peer-reviewed
publications to assess P-addition effects on soil N dynamics. Globally, P
additions increased the soil total N (TN) pool, potentially as a result of
enhanced plant and microbial immobilization and reduced N losses, with a
stronger effect detected under longer duration of P addition (≥ 5 years).
A coupled increase in soil organic C with TN signifies the fundamental
role of exogenous P supply in enhancing soil C sequestration. Phosphorus
addition accelerated some of the soil N cycling processes including gross
N mineralization, gross nitrification, and denitrification, with the
effect sizes varying among ecosystem types and increasing with P addition
rates. Our results indicate the fundamental role of P in affecting soil N
pools and processes, and highlight the efficacy of P supply in
sequestering soil C and mitigating global C emission.

氮（N）与磷（P）的交互作用对植物生长及生态系统碳（C）固存至关重要。尽管学界已针对氮供给对磷动态的影响开展了大量研究，但对其反向路径（磷对氮的影响）的认知仍较为匮乏。本研究通过整合116篇同行评议文献中的1734组独立实验观测数据，开展了一项荟萃分析（meta-analysis），以评估磷添加对土壤氮动态的影响。全球尺度下，磷添加提升了土壤总氮（TN）库，这一效应可能源于植物与微生物固持作用增强以及氮损失减少，且在磷添加时长≥5年的实验中，该效应更为显著。土壤有机碳与总氮同步增加的现象，表明外源磷供给在增强土壤碳固存方面发挥着基础性作用。磷添加还加速了部分土壤氮循环过程，包括总氮矿化（gross N mineralization）、总硝化作用（gross nitrification）与反硝化作用（denitrification），其效应量因生态系统类型而异，并随磷添加速率提升而增大。本研究结果证实了磷在调控土壤氮库与氮循环过程中的核心作用，并凸显了磷供给在固存土壤碳与减缓全球碳排放方面的有效性。