LITTERFALL, LITTER DECOMPOSITION AND MAIZE BIOASSAY OF MULCHES FROM FOUR INDIGENOUS TREE SPECIES IN MIXED AND MONOSPECIFIC PLANTATIONS IN COSTA RICA

SUMMARY

Three plantations with native timber species were established in the Atlantic humid lowlands of Costa Rica to compare growth and nutrient cycling in pure and mixed stands. As part of the project, leaf litter decomposition, litterfall and accumulation of leaf litter on the plantation floor were studied in a young plantation of Pithecellobium elegans D. C. Benth, Genipa americana L., Vochysia ferruginea Mart., and Hyeronima alchorneoides Fr. Allemao. Of the four species studied, V. ferruginea had the highest annual litterfall (867.6 g m^-2), G. americana had the lowest (386.7 g m^-2), and the mixed plots had an intermediate level (660 g m^-2). P. elegans ‘leaves decomposed the most rapidly, V. ferruginea's leaves decomposed the slowest, and the mixed litter decomposed at an intermediate rate. Mulch bioassays testing maize seedling growth showed higher survival and growth rates than the unmulched control in every treatment except for the G. americana mulch. Overall, P. elegans appears to be a good candidate for agroforestry combinations: the sparse canopy allowed light to penetrate, and its mulch showed the most positive effect on growth of maize seedlings. The large amount of litter produced by H. alchorneoides and V. ferruginea makes them helpful in protecting against soil erosion. A mixed species treatment may combine beneficial effects of the different species’ characteristics, with the additional advantage of product diversification, especially important for the subsistence-oriented farmers of the region.

Key words:

• humid tropics
• decomposition
• mixed plantation
• mulch
• native species