Long-term nitrogen fertilization indirectly affects soil fungi community structure by changing soil and pruned litter in a subtropical tea (Camellia sinensis L.) plantation in China

Abstract

The tea plant is a perennial leaf-harvest crop with high nitrogen (N) demand and a requirement for periodic pruning. While the effect of N fertilization on soil fungal communities has been studied extensively, little is known about the effects of returning the pruned litter to plots on the soil fungal community. Moreover, we do not understand how N fertilization might affect fungal communities by mediating changes in the soil and the properties of pruned tea litter. Surface soil (0-20 cm in depth) samples were taken from a long-term tea plantation field experiment featuring four N treatments (0, 119, 285, and 569 kg N ha–1 y–1). We investigated the soil fungal community by high-throughput sequencing and partial least square path modeling (PLS-PM) to clarify how N fertilization affects soil fungal community composition. N fertilization significantly increased inorganic N levels but significantly decreased soil pH, the total amount (TP_A) and concentration (TP) of total polyphenols, and the ratio of litter total polyphenols to total nitrogen (TP/TN) in pruned litters. Ascomycota, Basidiomycota, and Zygomycota represented ~69% of the fungi in tea soils. Higher rates of N fertilization reduced fungal community diversity (Chao1 index: r=0.67, p<0.01) and significantly changed the fungal composition (PERMANOVA: R2=0.33, p=0.003). PLS-PM results showed that changes in soil pH and NO3– and the TP/TN of pruned litter were the most important factors exerting a direct impact on the composition of soil fungal communities after N fertilization. Higher N fertilization reduced the diversity of soil fungi and shifted community composition. These changes were predominantly due to alterations in soil properties (pH and NO3-) and pruned litter quality (TP/TN). Our results also highlight the importance of the returning pruned materials with abundant TP to plots for soil microbial transformation in tea plantation ecosystems.