Data from: Contrasting responses of phosphatase kinetic parameters to nitrogen and phosphorus additions in forest soils

1. Global changes include increasing nitrogen (N) and phosphorus (P) deposition, which affect microbial nutrient demand and biogeochemical cycles. The responses of P-mineralizing enzymes to these global change components are poorly defined and are not specified in forest soils differing in P content.
2. We chose one site in a P-rich and two sites in P-poor forests and established sixteen 20 × 20 m plots at each site. Control, either N only, P only, or combined N and P, were randomly distributed through each forest site with 4 replicates. We investigated the effects of N and P additions over four years on the phosphomonoesterase potential activity (Vmax), its half-saturation constant (Km), and its catalytic efficiency (Vmax/Km).
3. Without N and P additions, the enzyme kinetic parameters Vmax, Km, and Vmax/Km were higher in P-rich than in P-poor forest soils. These parameters increased with soil pH, SOC, TN, and TP contents increased.
4. Remarkably, P additions caused the Vmax and Km to increase in P-rich soils, but had no effect on Vmax/Km. P additions to P-poor soils resulted in a decrease in the Vmax/Km via the inhibitory effects of inorganic P on the Vmax. N additions had no effect on the Vmax/Km in P-rich and P-poor soils because of the similar increases in the Vmax and Km. The effects of combined N and P and P only additions to P-poor soils on the Vmax and Km were similar, but were stronger than the effects of N only or P only additions on the P-rich soils.
5. Phosphatase kinetic parameters were positively related to the availability of N and P in P-rich soils, but inorganic P inhibited phosphatase activity and caused a decrease in the catalytic efficiency in P-poor soils. More microbial community groups could contribute to the secretion of a broader spectrum of iso-enzymes under combined additions of N and P in P-rich soils. We conclude contrast responses of phosphatase kinetics to P and N inputs in P-rich and P-poor forest soils, while long-term N deposition might mitigate P limitation by increasing phosphatase secretion.

1. 全球变化涵盖氮（N）、磷（P）沉降的加剧，该过程会影响微生物的养分需求与生物地球化学循环。目前磷矿化酶（P-mineralizing enzymes）对这类全球变化因子的响应机制尚不明确，且在磷素含量各异的森林土壤中尚未得到针对性阐释。
2. 本研究选取1个富磷森林样地与2个贫磷森林样地，在每个样地内设置16个20×20米的样方。各森林样地内均随机布设4个重复的对照组、单施N组、单施P组以及氮磷配施组。我们开展了为期4年的N、P添加试验，探究其对磷酸单酯酶（phosphomonoesterase）潜在活性（Vmax）、半饱和常数（Km）及催化效率（Vmax/Km）的影响。
3. 在未施加N、P的对照组中，富磷森林土壤的酶动力学参数Vmax、Km及Vmax/Km均高于贫磷森林土壤。上述参数随土壤pH、土壤有机碳（Soil Organic Carbon, SOC）、全氮（Total Nitrogen, TN）及全磷（Total Phosphorus, TP）含量的升高而增大。
4. 值得注意的是，在富磷土壤中，单施P会使Vmax与Km升高，但对Vmax/Km无显著影响。而在贫磷土壤中，单施P会通过无机磷（inorganic P）对Vmax的抑制作用，导致Vmax/Km降低。单施N对富磷与贫磷土壤的Vmax/Km均无显著影响，这是因为Vmax与Km的增幅相近。在贫磷土壤中，N+P配施与单施P对Vmax、Km的影响效果相似，但二者的作用强度均强于富磷土壤中单施N或单施P的处理效应。
5. 在富磷土壤中，磷酸酶动力学参数与N、P的有效性呈正相关；而在贫磷土壤中，无机磷会抑制磷酸酶活性，导致催化效率下降。在富磷土壤中施加N+P配施处理时，更多的微生物类群可参与合成谱更广的同工酶（iso-enzymes）。综上，富磷与贫磷森林土壤中磷酸酶动力学对N、P输入的响应存在显著差异；长期氮沉降或可通过提升磷酸酶分泌量，缓解土壤磷限制。