Leaf litter presence in the non-growing season prolongs plant legacy effects on soil fungal communities and succeeding plant growth

Soil microbes can profoundly affect species coexistence and alien plant invasion via plant-soil feedbacks (PSFs). Theoretically, plants can modify soil biotic communities (e.g. fungal and bacterial communities) sequentially via rhizo-inputs in the growing season and via litter decomposition in the non-growing season, and in this way affect the performance of plant individuals that establish in the same soil in the following growing season. However, how plants affect soil microbes via sequential rhizosphere and litter inputs and how these soil microbial legacies feedback to subsequent plants remains unclear. Here, we first explored the sequential effects of living individuals and their leaf litter on soil fungal communities, using 42 common alien and native species in China, and then estimated their PSF effects on three common test species. Our results show that living plants growing in field soil developed distinct rhizosphere fungal communities within one season. After the removal of conditioning plants, the fungal communities in these conditioned soils changed more dramatically in the absence than in the presence of leaf litter, suggesting that leaf litter inputs prolonged the species-specific legacies that conspecific living individuals exerted in the soil. Moreover, leaf litter induced general negative effects on all test species in the second growing season. Conditioning plant origin (native vs. alien) and life cycle (annual vs. perennial), respectively, had a slight or no impact on fungal community composition, and conditioning plant origin did not affect PSF responses of the test species. Synthesis: These findings show that leaf litter prolongs soil fungal legacies of conspecific living individuals, which can lead to carryover effects on heterospecific plant growth in the next season. Our findings highlight the importance of leaf litter for plant-soil interactions and thereby stress the potential importance of plant litter as a driver of plant community dynamics.

Automated summary

Soil microbes play a profound role in species coexistence and alien plant invasion through plant-soil feedbacks. Plants can modify soil fungal communities through rhizo-inputs and litter decomposition, influencing the performance of subsequent plants in the same soil. However, the specific mechanisms of how plants affect soil microbes and the subsequent feedback effects remain unclear.