While grassland afforestation can enhance the net mineralization of soil organic phosphorus (P), the mechanisms involved and impacts of different tree species are not clear. Soil samples were taken from replicated adjacent field plots that had been maintained under unfertilized grazed grassland, radiata pine (Pinus radiata), and eucalyptus (Eucalyptus nitens) for 19 years. Soil phosphorus fractions were determined together with alkaline phosphatase activity and associated phoD and phoX gene analysis. Afforestation significantly decreased soil organic P, microbial biomass P, and soil alkaline phosphatase activity, and increased inorganic P bioavailability, although no differences were measured between radiata pine and eucalyptus. While distinct separation of phoD and phoX gene bacterial communities was associated with afforestation of grassland, separation between tree species was less pronounced. Shifts in phoD and phoX gene community structure were more related to soil moisture and pH than P status. Overall, we found that changes in soil moisture and pH associated with afforestation, rather than tree species per se, significantly affected the occurrence and diversity of bacterial alkaline phosphatase. This highlights the potential effects of changes in land-use and management on soil P dynamics and bioavailability.

虽然草地绿化可以增强土壤有机磷（P）的净矿化作用，但是不同树木的参与机制和影响尚不清楚。从重复的相邻田地上采集土壤样品，这些田地在未施肥的放牧草地，辐射松（Pinus radiata）和桉树（Eucalyptus nitens）下维持了19年。测定土壤中的磷含量，碱性磷酸酶活性以及相关的phoD和phoX基因分析。绿化显着降低了土壤有机磷，微生物生物量磷和土壤碱性磷酸酶活性，并增加了无机磷的生物利用度，尽管辐射松和桉树之间没有差异。虽然phoD和phoX基因细菌群落的明显分离与草地的造林有关，但树种之间的分离不太明显。轮班phoD和PHOX基因群落结构更关系到土壤水分，pH值小于P状态。总体而言，我们发现土壤水分和pH值的变化与造林相关，而不是树木本身，显着影响细菌碱性磷酸酶的发生和多样性。这突出了土地利用和管理方式变化对土壤磷动力学和生物利用度的潜在影响。