Natural-enemies affect the seed and litter fall dynamics of Melaleuca quinquenervia in the wetlands, and influence long-term species diversity in leaf-litter

The exotic tree Melaleuca quinquenervia (melaleuca) has invaded and formed monotypic forest stands in ecologically sensitive wetlands of Florida. We hypothesized that natural-enemy impact would influence melaleuca's litter and seed fall dynamics via chronic attacks, and enhance native species diversity, which will be reflected in leaf litter composition. This hypothesis was tested during 1997-2013 by studying melaleuca stands in occasionally inundated habitats infested by its natural enemies. Results from our study showed: (1) an initial increase in the leaf and seed fall during the first-half of the study period, followed by about 70% decline during remainder of the study period, (2) a positive correlation between the amount of leaf and seed fall, (3) a negative correlation between the proportion of natural-enemy damaged melaleuca leaf litter and the quantity of fallen seeds, and (4) a slow but steady increase of the non-melaleuca leaf litter amount by 81% and with a corresponding decrease in melaleuca leaf litter by 15%. Of the 17 non-melaleuca species recovered, we recorded two perennials at the onset of the study, which increased to seven during the second half of the study period, one of which was non-native. Cladium and Myrsine species produced significantly more leaf-litter by the end of the study period. Over 80% of the melaleuca leaf litter manifested natural-enemy damage during the last 7-year of the study period. These results provide evidence of a negative influence of natural enemy attack on melaleuca leaf and seed fall dynamics and a positive influence on native species diversity in the fallen leaf litter.