Effects of leaf size and decay rate on colonization by aquatic hyphomycetes

Oak and maple leaf squares of graded sizes were exposed in a Black Forest stream. Their colonization by aquatic hyphomycetes was studied in summer and in autumn, and in the presence or absence of leaf-eating invertebrates. The cumulative number of fungal species was significantly correlated with the initial size of the substrate. However, the goodness of fit of the regression equation was considerably improved when integrated decay curves instead of initial areas or weights of the squares were used. Spore production of a leaf square was directly proportional to its integrated decay curve. All fungal communities on the various squares showed close agreement with a logseries species distribution. Time of arrival of a fungal species was significantly correlated with its overall reproductive output.