Conclusion
Our multi-method approach provides evidence that community pathogen load is more commonly associated with host community composition (evenness and proneness) than with linear changes along the elevational gradient. In contrast, we did find that increasing elevation was associated with soil fungal pathogen richness (but not relative abundance), via the effects of temperature and soil properties. These results highlight elevational patterns of above- and belowground plant pathogens may be regulated by distinct mechanisms, and are consistent with a growing body of studies of foliar diseases (Mitchell et al., 2002; Rottstock et al., 2014; Cappelli et al., 2020; Halliday et al., 2021) and soil pathogens (Tedersoo et al., 2014; Delgado-Baquerizo et al., 2020). More importantly, there is increasing evidence that environmental gradients can modify how host community structure affects disease (Halliday, Heckman, et al., 2020; Halliday et al., 2021). These interaction effects may help explain the variation among different studies, highlighting that only looking at environmental factors or community structure would miss key information relevant to diseases. Nevertheless, for the first time, to the best of our knowledge, we distinguish the different mechanisms driving different groups of plant pathogens in an alpine meadow. Because of rapid changes in both plant communities and climate change in the Anthropocene, our study implies that incorporating different information to build models predicting above- and belowground plant pathogens is of great importance for understanding ecosystem health.