LITTERFALL, LITTER DECOMPOSITION AND THE USE OF MULCH OF 4 INDIGENOUS TREE SPECIES IN THE ATLANTIC LOWLANDS OF COSTA-RICA

Litterfall, forest-floor litter biomass and nutrients, short-term litter decomposition and the effects of leaf mulches on initial growth of maize were studied for four indigenous tree species with agroforestry potential: Stryphnodendron microstachyum Poepp. et Endl. (S. excelsum), Vochysia ferruginea Mart, Vochysia guatemalensis Donn. Sm. (V. hondurensis) and Hyeronima alchorneoides (O), growing in a young experimental plantation in the Atlantic humid lowlands of Costa Rica. Total annual leaf litterfall was higher in V ferruginea plots, followed by S. microstachyum, V guatemalensis and H. alchorneoides; all with values comparable to those reported for other tree species grown in agroforestry combinations in humid tropical regions. Forest-floor litter accumulation was highest under V ferruginea and V guatemalensis. Both litterfall and forest-floor litter material had similar patterns in nutrient concentrations: N was higher in S. microstachyum, Ca was higher in V. guatemalensis, K was higher in H. alchorneoides; Mg was higher in V. guatemalensis and H. alchorneoides; H. alchorneoides and V. guatemalensis had the highest P. V ferruginea litter decomposed more slowly, while S. microstachyum apparently decomposed faster than the other species. The two Vochysia species showed increases in N and P concentration in decomposing litter after seven weeks in the field, H. alchorneoides showed an increase in litter N and a decrease in litter P, and S. microstachyum showed a net decrease in both N and P over the same time period. The patterns found in the litter bag study were confirmed by results obtained in a tethered-leaves experiment. S. microstachyum and V. ferruginea litters lost more weight when mixed in a 1:1 proportion than either of them alone. Maize seedlings growing in plots mulched with S. microstachyum and H. alchorneoides leaves showed greatest initial growth, confirming patterns found in decomposition and nutrient release studies. The results show that these species could be used in agroforestry combinations with different advantages according to the specific objectives desired, whether these are soil protection, nutrient recycling, or enhancement of the growth of associated crops.