Data from: Reconsidering the phosphorus limitation of soil microbial activity in tropical forests

1. It has long been believed that soil microbial activity in tropical forest ecosystems is limited by phosphorus (P) rather than nitrogen (N) availability. In this study, we reviewed the methods used to determine the limiting nutrients and evaluated the validity of the widespread P-limitation hypothesis in tropical forest soils.
2. The most commonly used analysis method entails testing whether fertilization increased microbial biomass or soil respiration. Fertilization using microbial biomass as an indicator was not a satisfactory method because standing microbial biomass does not always signal microbial activity. An increase in soil respiration after fertilization was also an insufficient indicator because the negative response shown by organic matter decomposition to nutrient addition can also be driven by nutrient shortage (nutrient mining). Nutrient amendment can also shift microbial communities toward more copiotrophic organisms, which may exhibit lower microbial respiration rates.
3. We suggest that P addition may accelerate soil organic matter decomposition compared with N, which is independent of the nutrient limitation of soil microbial activity. The negative response of organic matter decomposition to N addition through nutrient mining is driven by N shortage, which is less likely to occur with P. N addition inhibits microbial activity via chemical reactions, whereas P addition may stimulate activity through replacement by C bound to sorption sites in the soil, improving C availability. Thus, the P-limitation hypothesis must be reconsidered because of the contrasting effects of exogenous N and P addition on soil microbial activity, which could lead to misdetection of P limitation on soil microbial activity in tropical forest ecosystems.
4. We recommend caution in applying the statement that soil microbial activity in tropical forest ecosystems is limited by P until a novel method is established to accurately determine the nutrients limiting soil microbial activity at the ecosystem level. We propose alternative ways to describe nutrient shortage for soil microbes.

1. 长期以来，学界普遍认为热带森林生态系统的土壤微生物活性受磷（P）而非氮（N）有效性限制。本研究梳理了用于界定限制性养分的研究方法，并评估了热带森林土壤中广为流传的磷限制假说的合理性。
2. 当前最常用的分析方法为验证施肥是否会提升微生物生物量或土壤呼吸速率。以微生物生物量为指标的施肥实验并非理想方法，因为原位微生物生物量并不总能反映微生物活性。施肥后土壤呼吸速率的提升同样不足以作为有效指标——有机质分解对养分添加的负响应，同样可能由养分匮乏（养分挖掘作用）驱动。此外，养分添加还会使微生物群落向更具富营养特性的类群偏移，这类类群的微生物呼吸速率往往更低。
3. 我们提出，相较于氮添加，磷添加或许会加速土壤有机质分解，这一效应并不依赖于土壤微生物活性的养分限制类型。通过养分挖掘作用，氮添加会对有机质分解产生负响应，该负响应由氮匮乏驱动，而这种情况在磷添加时则极少发生。氮添加可通过化学反应抑制微生物活性，而磷添加则可能通过置换土壤吸附位点结合的碳，提升碳的可利用性，进而刺激微生物活性。因此，外源氮与磷添加对土壤微生物活性的影响存在显著差异，这意味着当前热带森林生态系统中磷限制的检测可能存在偏差，因此需重新审视磷限制假说。
4. 我们建议，在建立可在生态系统尺度上精准界定限制土壤微生物活性的养分的新方法之前，应谨慎使用“热带森林生态系统土壤微生物活性受磷限制”这一表述。此外，我们还提出了用于描述土壤微生物养分匮乏状态的替代方案。