Parameter assumptions for analytical simplifications.

Table notes and references: The subscript i refers to nitrogen (N) and phosphorus (P).1In non-agricultural systems, internal recycling of both N and P (between plants and soils) typically exceeds total inputs and losses (to or from the atmosphere or waterways) many fold, both globally [44], [101] and at individual sites [102]. Consequently, litter decomposition is much greater than litter loss (δiLi >> hiLi), plant uptake is much greater than losses of plant-available nutrients (BνiAi >> kiAi), SOM mineralization is much greater than SOM loss (miDi >> φiDi), and SOM mineralization is much greater than the balance of abiotic inputs and plant-available losses (miDi >> |Ii – kiAi,i|). Exceptions to this pattern will occur where losses are very high (e.g., when ground fires or heavy erosion frequently remove substantial amounts of litter, it is unlikely that δi >> hi), where plant or SOM pools are very small (e.g., at the beginning of primary succession, it is unlikely that miDi >> |Ii – kiAi,i|; see text and analysis), or in heavily polluted regions.2See ref [51].3Plants typically have an order of magnitude higher N content than P content [44], [103].4P is more readily cleaved from organic matter than N (see text).5For decomposition, we have defined the parameters such that ε controls the relative mineralization of N versus P and δ is the overall litter decomposition rate.6N and P loss rates via leaching and erosion should be similar because they come from the same organic material. In ecosystems where fire is important, organic N loss rates may be relatively higher than P.

表注与参考文献：下标i指代氮（N）与磷（P）。1 在全球尺度[44]、[101]以及单个研究站点[102]中，非农业生态系统内氮与磷的内部循环（在植物与土壤之间）通常远超总输入与（向大气或水道的）总输出数倍。因此，枯落物分解量远大于枯落物损失量（δᵢLᵢ >> hᵢLᵢ），植物对养分的吸收量远大于植物有效养分的损失量（BνᵢAᵢ >> kᵢAᵢ），土壤有机质（Soil Organic Matter, SOM）矿化量远大于土壤有机质损失量（mᵢDᵢ >> φᵢDᵢ），同时土壤有机质矿化量也远大于非生物输入与植物有效养分损失的差值（mᵢDᵢ >> |Iᵢ – kᵢAᵢ,ᵢ|）。当损失量极高时（例如，当地面野火或严重侵蚀频繁移除大量枯落物时，大概率不存在δᵢ >> hᵢ的情况）、当植物或土壤有机质库规模极小时（例如，原生演替初期，大概率不满足mᵢDᵢ >> |Iᵢ – kᵢAᵢ,ᵢ|，详见正文与分析），或在重污染区域，该规律会出现例外。2 详见参考文献[51]。3 植物的氮含量通常比磷含量高出一个数量级[44]、[103]。4 磷比氮更易从有机质中裂解（详见正文）。5 针对分解过程，我们对参数的定义为：ε用于调控氮与磷的相对矿化程度，δ为枯落物总分解速率。6 氮与磷通过淋溶与侵蚀产生的损失速率应当相近，因为二者均源自同一有机质组分。在火干扰作用显著的生态系统中，有机氮的损失速率可能相对高于有机磷。