An invasive and native plant differ in their effects on the soil food-web and plant-soil phosphorus cycle

Abstract

Although invasive species threaten the functional integrity of ecosystems significantly, their impacts on essential ecosystem processes such as soil phosphorus (P) cycling are not well understood. In a field experiment, we used a randomized complete block design to study how an invasive plant species may disrupt soil functioning, particularly P cycling compared to a native plant species. After three years of experiments, we compared soil P properties and soil micro food-webs (microorganisms and nematodes) induced by these two species. We also compared plant biomass and P allocation in the different tissues for these plants. A second microcosm experiment was performed to check whether the interactions of nematode and microorganisms affected the ecological processes of soil organic P mineralization. Compared to native species, invasive species had higher alkaline phosphomonoesterase (ALP)-producing bacteria, bacterivorous nematodes, and ALP activity and induced a stronger acceleration of soil organic P decomposition through the more interactions between ALP-producing bacteria and bacterivores. Moreover, the mycorrhizal colonization rate of the invasive species was higher than the native species, allowing it to absorb more P and allocate more to above-ground biomass, and thus maintaining its faster expansion. The invasive species had lower nucleic acid P, structural P, and residual P in foliar than the native species because invasive species allocate more P to metabolic P for photosynthesis. Our study suggests that invasive plants can enhance the organic P decomposition through microbial-microfaunal interactions. In addition, invasive plants might have higher P utilization efficiency than native ones. Although these findings need to be generalized with more native and invasive plant species, they still provide novel mechanistic explanations into how invasive species can expand quickly in P-poor lower latitudes.