Different life-form plants exert different rhizosphere effects on phosphorus biogeochemistry in subtropical mountainous soils with low and high phosphorus content

Abstract

Soil phosphorus (P) is among the most important but least understood nutrients supporting the productivity and function of terrestrial ecosystems. To understand soil P cycling, it is essential to quantify the effects of plants on soil P fractions (labile inorganic P [Pi], intermediately available Pi, organic P, and occluded P). The study aimed to compare how the rhizosphere effect of different life-form plants influences P fractions in P-depleted and P-enriched soils in southwest China’s subtropical mountainous region. For all three selected species (native conifer, Pinus yunnanensis; native shrub, Myrsine africana; invasive herb: Eupatorium adenophorum), total P and P-fraction concentrations were much higher in the high-P site than in the low-P site. Occluded and organic P were the dominant fractions at the low-P site, while occluded and intermediate P were the dominant P fractions at the high-P site. Species identity significantly affected all five soil P fractions in both sites, except organic P at the high-P site. Total P, labile P, and intermediate P changed significantly with time. Additionally, plants were able to increase the rhizosphere effect on labile and intermediate P at the low-P site, as well as organic P at the high-P site. Eupatorium adenophorum exerted a significantly positive rhizosphere effect on labile and intermediate P at the low-P site, as well on labile P and organic P in the high-P site. Thus, compared with native M. africana and P. yunnanensis, the invasive E. adenophorum can more effectively alter rhizosphere soil P fractions in response to different soil P levels. Linear regression showed that the rhizosphere effect on labile P was correlated with the rhizosphere effect on pH, and the rhizosphere effect on organic P was related to the rhizosphere effect on soil organic matter and exchangeable Feox and Alox. In conclusion, different life-form plants generally exert a different rhizosphere effect through geochemical and biological processes, thus influencing P biogeochemical cycling in different soil P contents.