Increasing phosphorus limitation along three successional forests in southern China

Phosphorus (P) is commonly one of most limiting nutrients in tropical and subtropical forests, but whether P limitation would be exacerbated during forest succession remains unclear.Soil phosphatase activity is often used as an indicator of P limitation. Here we examined soil acid phosphatase activity (APA) underneath tree species in pine forest (PF), mixed pine and broadleaf forest (MF) and monsoon evergreen broadleaf forest (MEBF) which represented the early, middle and late successional stages of subtropical forests in China, respectively. We also analyzed other indicators of P status (soil available P and N and P stoichiometry of the tree species).APA or APA per unit soil organic carbon under tree species was relatively low in the early successional forest. Different from PF and MF, soil available P beneath the tree species was lower than in the bulk soils in MEBF. Soil APA was closely related to N:P ratios of tree species across all three forests.Our results imply that P limitation increases during forest succession at our site. The dominant tree species with low soil APAs in MEBF are likely more P-limited than other tree species.

磷（P）通常是热带和亚热带森林中最具限制作用的养分之一，但在森林演替过程中磷限制是否会加剧仍不明确。土壤磷酸酶活性常被用作磷限制的一个指标。在此，我们研究了松林（PF）、针阔混交林（MF）和季风常绿阔叶林（MEBF）中树种下方的土壤酸性磷酸酶活性（APA），这三种森林分别代表了中国亚热带森林演替的早期、中期和晚期阶段。我们还分析了磷状况的其他指标（土壤有效磷以及树种的氮磷化学计量比）。在演替早期的森林中，树种下方的APA或单位土壤有机碳的APA相对较低。与松林和针阔混交林不同，季风常绿阔叶林中树种下方的土壤有效磷低于林分整体土壤。在这三种森林中，土壤APA与树种的氮磷比密切相关。我们的研究结果表明，在我们研究地点的森林演替过程中，磷限制有所增强。在季风常绿阔叶林中，土壤APA较低的优势树种可能比其他树种更受磷限制。