Litter cover variability affects seedling performance and herbivory

We assessed the effects of litter cover on herbivory and performance (annual survival and relative growth rate in height and leaf number) for established seedlings (greater than or equal to 9 cm tall, and greater than or equal to 4 mo old), of four shade-tolerant, large-seeded, co-occurring Sapotaceae species. Seedlings were divided into three liner treatments: (1) litter addition, (2) control, and (3) continuous liner removal. The mean survival For all treatments in descending order were: Chrysophyllum pomiferum (83%), Pouteria peruviensis (84%), P. caimito (75%), and Micropholis venulosa (40%). For all variables, species differed significantly within litter treatments. In M. venulosa, survival and relative growth rare in leaf number significantly decreased with the removal of litter, whereas herbivory increased. Relative growth rate in height: of P. peruviensis decreased significantly with litter removal, while the levels of herbivory were higher with the addition of litter. Conversely litter quantity had no effect on the performance of C. pomiferum but herbivory was lower in the removal treatment. Finally in P. caimito, litter treatment did not affect performance or herbivory. Results suggest that differences in litter quantity differentially affect tree species with similar biology (i.e., large-seeds, shade tolerance) in life stages other than germination and early establishment. The variability in species' responses to litter might be an important factor in determining species richness, abundance, and distribution of tropical rain forest tree species at the seedling level.