Phosphorus acquisition strategies of arbuscular mycorrhizal and ectomycorrhizal trees in subtropical plantations

Abstract

AbstractTrees form symbioses with different fungi to exploit soil nutrients, such as phosphorus (P). There is no precise information about the exact strategies by which arbuscular mycorrhizae (AM) and ectomycorrhizae (EM) species facilitate P acquisition and thereby regulate soil P availability in the P‐limited subtropical forests. We investigated the plant traits and rhizosphere soil properties related to the P acquisition strategies of seven AM and seven EM tree species in a subtropical plantation in China. The available P content, which was related to acid phosphomonoesterase activity, was higher in the rhizosphere soils of the AM trees than in those of the EM trees. The higher P content in the absorptive fine roots indicated that the AM trees absorbed more P from the soil than the EM trees. The leaf P adsorption efficiency indicated that AM trees resorbed more aboveground P than EM trees. Results from structural equation modelling demonstrated that AM trees were dominated by bacteria, which contributed to the low pH, while EM trees were dominated by ectomycorrhizal and saprophytic fungi that secreted acid phosphomonoesterase to mine P in the rhizosphere soil. The AM trees had higher mycorrhizal colonisation rates than the EM trees, while the EM trees had higher specific root lengths than the AM trees, which suggests that the AM trees tended to depend on mycorrhizae, while EM trees tended to depend on roots, to scavenge P from soil. Our findings suggest that, to influence the P availability and alleviate P deficiencies, the AM trees resorbed more P aboveground and mined and scavenged more P belowground than the EM trees.Highlights P availability was higher in the rhizospheres of AM trees than EM trees. AM trees resorbed more aboveground P than EM trees. AM trees mined soil P mainly by decreasing pH, whereas EM trees by secreting ACP. AM trees depended more on mycorrhizae, whereas EM trees on roots, scavenging soil P.