Temporal and spatial fluctuations in moisture affect humus microfungal community structure in microcosms

The effects of temporal and spatial fluctuations in moisture on the microfu ngal community were studied in birch litter plus pine humus microcosms over 6 months. Two treatments were used: a uniform treatment in which moisture was maintained at the original moisture content throughout the profile over the course of the experiment; and a fluctuating moisture treatment in whic h the moisture content of the whole microcosm fluctuated weekly around the original moisture content. At 6 months, fungal species richness was higher and diversity was lower under moisture fluctuations than under uniform mois ture. The number of fungal isolates and proportional diversity was signific antly higher in the bottom layer in the fluctuating moisture treatment. The fluctuating moisture treatment and the bottom layer correlated significant ly with the first PCA axis, which accounted for 66% of the variation in the fungal species data. The experiment suggests that even without drying, flu ctuations in moisture can affect fungal community structure.