FUNGAL COMMUNITIES IN WET TROPICAL FORESTS - VARIATION IN TIME AND SPACE

Understanding variation in tropical forest fungal populations and comm unities is important for assessing fungal biodiversity, as well as for understanding the regulatory roles fungi play in tropical forests. In wet tropical forests, the canopy is typically occupied by certain woo d decomposers, endophytes, epiphylls, and pathogens. Aphyllophoraceous canopy fungi are a subset of species found in the understory. Marasmi oid agarics in the understory often form extensive networks of rhizomo rphs that trap litter; these and other aerial species are rare on the forest floor. Decomposers are stratified within the forest floor, with some species colonizing only fresh litter, others preferring decompos ed litter, and others restricted to soil organic matter. Specificity t o particular host substrates is frequent among tropical forest litter decomposers and contributes to spatial heterogeneity in fungal communi ties over the landscape. Litter basidiomycete and microfungal communit ies in patches of 1 m(2) or less do not significantly resemble communi ties in similar patches located at distances greater than LOO m. Distu rbances induce changes in the environment and the abundance of differe nt substrates, resulting in changes in fungal communities through time , and variation over the landscape. Severe disturbances, as well as th e slight daily variations in rainfall, profoundly affect populations o f fungal decomposers and their influence on plant nutrient availabilit y.