Nitrogen (N) deposition affects forest stoichiometric flexibility through changing soil nutrient availability to influence plant uptake. However, the effect of N deposition on the flexibility of carbon (C), N, and phosphorus (P) in forest plant-soil-microbe systems remains unclear. We conducted a meta-analysis based on 751 pairs of observations to evaluate the responses of plant, soil and microbial biomass C, N and P nutrients and stoichiometry to N addition in different N intensity (0–50, 50–100, >100 ​kg⋅ha⋅year of N), duration (0–5, >5 year), method (understory, canopy), and matter (ammonium N, nitrate N, organic N, mixed N). N addition significantly increased plant N:P (leaf: 14.98%, root: 13.29%), plant C:P (leaf: 6.8%, root: 25.44%), soil N:P (13.94%), soil C:P (10.86%), microbial biomass N:P (23.58%), microbial biomass C:P (12.62%), but reduced plant C:N (leaf: 6.49%, root: 9.02%). Furthermore, plant C:N:P stoichiometry changed significantly under short-term N inputs, while soil and microorganisms changed drastically under high N addition. Canopy N addition primarily affected plant C:N:P stoichiometry through altering plant N content, while understory N inputs altered more by influencing soil C and P content. Organic N significantly influenced plant and soil C:N and C:P, while ammonia N changed plant N:P. Plant C:P and soil C:N were strongly correlated with mean annual precipitation (MAT), and the C:N:P stoichiometric flexibility in soil and plant under N addition connected with soil depth. Besides, N addition decoupled the correlations between soil microorganisms and the plant. N addition significantly increased the C:P and N:P in soil, plant, and microbial biomass, reducing plant C:N, and aggravated forest P limitations. Significantly, these impacts were contingent on climate types, soil layers, and N input forms. The findings enhance our comprehension of the plant-soil system nutrient cycling mechanisms in forest ecosystems and plant strategy responses to N deposition.

中文翻译：

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大气氮沉降影响森林植物和土壤系统碳：氮：磷化学计量灵活性：荟萃分析

氮（N）沉降通过改变土壤养分有效性来影响植物吸收，从而影响森林化学计量的灵活性。然而，氮沉降对森林植物-土壤-微生物系统中碳（C）、氮和磷（P）灵活性的影响仍不清楚。我们基于 751 对观测结果进行了荟萃分析，以评估植物、土壤和微生物生物量 C、N 和 P 养分以及化学计量对不同氮强度（0–50、50–100、>100）下氮添加的响应​kg·ha·N 年）、持续时间（0–5，>5 年）、方法（林下、冠层）和物质（铵态氮、硝酸盐态氮、有机态氮、混合态氮）。氮添加显着增加了植物N:P（叶：14.98％，根：13.29％），植物C：P（叶：6.8％，根：25.44％），土壤N：P（13.94％），土壤C：P（ 10.86%），微生物生物量N:P（23.58%），微生物生物量C:P（12.62%），但减少了植物C:N（叶：6.49%，根：9.02%）。此外，植物C:N:P化学计量在短期氮输入下发生显着变化，而土壤和微生物在高氮添加下发生巨大变化。冠层氮添加主要通过改变植物氮含量来影响植物 C:N:P 化学计量，而林下氮输入则通过影响土壤 C 和 P 含量而改变更多。有机氮显着影响植物和土壤的C:N和C:P，而氨氮则改变植物的N:P。植物 C:P 和土壤 C:N 与年平均降水量 (MAT) 密切相关，施氮条件下土壤和植物的 C:N:P 化学计量灵活性与土壤深度相关。此外，氮的添加消除了土壤微生物与植物之间的相关性。氮的添加显着增加了土壤、植物和微生物生物量中的C:P和N:P，降低了植物C:N，并加剧了森林P的限制。值得注意的是，这些影响取决于气候类型、土壤层和氮输入形式。这些发现增强了我们对森林生态系统中植物-土壤系统养分循环机制以及植物对氮沉降的策略响应的理解。