ALLELOPATHIC EFFECT OF CASTANOPSIS KAWAKAMH FOREST LITTER ON SEED GERMINATION OF SMALL PHILIPPINE ACACIA (ACACIA CONFUSA)

Nutrient limitation constrains the regeneration of Castanopsis kawakamii seedlings in subtropical forests. Small Philippine acacia (Acacia confusa), a common tree species in mixed forests, is known for its nitrogen fixation capabilities. Therefore, we attempted to intercrop A. confusa in a C. kawakamii natural forest. However, this forest contained abundant litter, harboring ample tannins and total phenols. Whether the allelopathy of litter could constrain the seed germination of A. confusa seed was unknown. Therefore, we aimed to explore the influence of forest litter extracts on the seed germination and radicle growth of A. confusa. The results indicate that low concentration litter extracts promote whereas high concentrations inhibit A. confusa seeds. The stock solution produced the strongest inhibition, whereas the 1:160 litter extract concentration had promoted the germination rate and radicle growth. The A. confusa radicle increase was remarkable in the first eight days, and tended to decrease from day 9 to 15. Overall, the allelopathic effect of litter is not a factor limiting the mixing of C. kawakamii and A. confusa. This could provide an alternative method to improving soil nutrition, thus promoting the regeneration of C. kawakamii seedlings.