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

Litterfall, forest-floor litter biomass and nutrients, short-term litt er 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. hondu rensis) and Hyeronima alchorneoides (O), growing in a young experiment al plantation in the Atlantic humid lowlands of Costa Rica. Total annu al leaf litterfall was higher in V ferruginea plots, followed by S. mi crostachyum, V guatemalensis and H. alchorneoides; all with values com parable to those reported for other tree species grown in agroforestry combinations in humid tropical regions. Forest-floor litter accumulat ion was highest under V ferruginea and V guatemalensis. Both litterfal l and forest-floor litter material had similar patterns in nutrient co ncentrations: N was higher in S. microstachyum, Ca was higher in V. gu atemalensis, K was higher in H. alchorneoides; Mg was higher in V. gua temalensis 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 sh owed an increase in litter N and a decrease in litter P, and S. micros tachyum showed a net decrease in both N and P over the same time perio d. The patterns found in the litter bag study were confirmed by result s obtained in a tethered-leaves experiment. S. microstachyum and V. fe rruginea 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 gro wth, confirming patterns found in decomposition and nutrient release s tudies. The results show that these species could be used in agrofores try combinations with different advantages according to the specific o bjectives desired, whether these are soil protection, nutrient recycli ng, or enhancement of the growth of associated crops.