The effects of weather on fungal abundance and richness among 25 communities in the Intermountain West

BACKGROUND: Because moisture and temperature influence the growth of fungi, characterizing weather conditions favorable for fungi may be used to predict the abundance and richness of fungi in habitats with different climate conditions. To estimate habitat favorability to fungi, we examined the relationship of fungal abundance and species richness to various weather and environmental parameters in the Intermountain West. We cultured fungi from air and leaf surfaces, and collected continuous temperature and relative humidity measures over the growing season at 25 sites. RESULTS: Fungal richness was positively correlated with fungal abundance (r = 0.75). Measures of moisture availability, such as relative humidity and vapor pressure deficit, explained more of the variance in fungal abundance and richness than did temperature. Climate measurements from nearby weather stations were good predictors of fungal abundance and richness but not as good as weather measurements obtained in the field. Weather variables that took into account the proportion of time habitats experienced favorable or unfavorable relative humidity and temperatures were the best predictors, explaining up to 56% of the variation in fungal abundance and 72% for fungal richness. CONCLUSION: Our results suggest that the abundance and richness of fungi in a habitat is limited by the duration of unfavorable weather conditions. Because fungal pathogens likely have similar abiotic requirements for growth as other fungi, characterizing weather conditions favorable for fungi also may be used to predict the selective pressures imposed by pathogenic fungi on plants in different habitats.