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.