海拔梯度变化对武夷山黄山松林土壤磷组分和有效性的影响

土壤磷（P）是植物生长必需的养分元素，也是亚热带森林生产力的主要限制元素。目前，关于不同海拔土壤P组分和P有效性的变化规律尚无统一定论，其原因主要是忽略了植被类型变化导致的P组分和P有效性对海拔的响应更为复杂。因此，以武夷山不同海拔黄山松林为研究对象，通过测定土壤环境因素、理化性质、微生物生物量（SMB）、酸性磷酸单酯酶（ACP）和磷酸双酯酶（PD）活性以及土壤P组分，探究土壤P组分和P有效性的变化及其影响因素。结果表明，随海拔降低，速效P含量显著增加，而易分解P、中等易分解P、难利用P和总磷含量显著减少。冗余分析结果表明，微生物生物量磷和微生物生物量氮是影响土壤P组分和P有效性变化的关键因素。研究表明，随海拔降低，黄山松林土壤微生物通过提高ACP、PD活性和降低SMB含量的能量分配策略，促进更多较难分解P组分的矿化，从而提高速效P含量，以满足微生物对P的需求。因此，在低海拔地区，微生物通过能量分配策略获取更多有效P，可能有利于提高武夷山黄山松林土壤速效P的供应，但从长期来看，可能使P矿化速率提高和P损耗增加，导致P库的储备不足，不利于土壤P素养分的可持续供应。

Effects of different elevational gradients on soil phosphorus fractions and availab ility in Pinus taiwanensis forest on Wuyi Mountain

Soil phosphorus (P) is an essential nutrient for plant growth and a major limiting element for productivity in subtropical forests. Currently, there is no unified conclusion on the change of soil P fractions and P availability at different elevations, primarily because the response of P fractions and availability at different elevational gradients caused by the change in vegetation types is complex. This study analyzed Pinus taiwanensis forest in Wuyi Mountain with different elevational gradients to explore the transformation and availability of soil P fractions and its influencing factors. We examined the soil environmental factors, physicochemical properties, microbial biomass (SMB), acidic phosphomonoesterase (ACP), phosphodiesterase (PD) levels, and soil P fractions. The results showed that the content of soluble P increased significantly with the decrease of elevation, while the content of labile P, moderately labile P, occluded P, and total phosphorus noticeably decreased. Redundancy analysis showed that microbial biomass phosphorus (MBP) and nitrogen (MBN) were the determining factors affecting soil P fractions. Our findings suggested that with a decrease in elevation, soil microorganisms promoted the transformation of P fractions. This occurred mainly through their energy allocation strategy, which increased the activities of ACP and PD and decreased SMB content; soil microorganisms in turn accelerates the mineralization of non-labile P, thereby increasing the content of soluble P that meets microbial demand. As a result, due to the relative lack of P element in lower altitudes, microorganism can obtain more available P through energy allocation strategy, which could help increase the supply of soil soluble P in Pinus taiwanensis forest of Wuyi Mountain. However, it may lead to an insufficient P reserve pool over the long term, which may have an adverse effect on the sustainable supply of soil P.