Distinct pathways of nutrient additions impact phyllosphere endophytic and epiphytic fungi in an alpine grassland

Phyllosphere fungi, including both endophytic and epiphytic groups, are key components of plant-associated microbiota with important roles in both plant health and ecosystem functioning. However, how nutrient enrichment influences these fungal communities remains poorly understood. In this study, we conducted a nitrogen (N) and phosphorus (P) additions experiment in an alpine grassland on the Qinghai-Tibetan Plateau to investigate the responses of phyllosphere fungal communities to nutrient inputs and to disentangle the underlying mechanisms. Our results revealed that N addition increased the diversity of endophytic fungi, while P addition reduced the diversity of epiphytic fungi. Moreover, nutrient additions affected fungal diversity and community composition through distinct pathways: endophytes responded primarily to changes in plant functional traits, whereas epiphytes were influenced directly or indirectly via shifts in soil properties and soil fungal communities. Our findings highlight the divergent responses of fungal communities to nutrient inputs, providing new insights into microbial responses to global change in alpine ecosystems.