Forest Litterfall Production, Nutrient Analysis and Litter Turnover at Mt. Apo Permanent Plot, North Cotabato, Philippines

Litterfall is an important component of the nutrient cycle in forest ecosystems. Thus, this study was carried out to assess the litterfall production, analyze the leaf nitrogen (N), phosphorus (P) and potassium (K) contents, and compute the litter turnover in the established 2-ha permanent plot of the Long Term Ecological Research (LTER) site in Mt. Apo, North Cotabato, Philippines. Plant litter were collected from the traps installed below the dominant tree species, processed at the laboratory, and oven-dried between November 2012 – June 2013 and January – October 2015. The leaves (62%) contributed the largest fraction to total litterfall production, followed by woody (21%), reproductive (12%) and miscellaneous (5%) parts. Mean annual litterfall production was 758.41 g ODW/m² which had an estimated mean daily litterfall production of 1.99 g ODW/m². Phyllocladus hypophyllus Hook.f. contributed the highest litterfall production with 24.35% and least by Lithocarpus apoensis (Elmer) Rehder with 16.89%. The order of nutrient contents in leaves was highest in N, followed by K and lowest in P. The highest content of N was observed in L. apoensis (3.04%) and lowest in P. hypophyllus (2.10%). Amount of K was also highest in L. apoensis (1.70%) and lowest in A. philippinensis (0.58%), and the highest amount of P was also observed in L. apoensis (0.143%) and lowest in P. hypophyllus (0.076%). Litter turnover rate was faster in L. apoensis (3.29%) which will decompose within 68.38 days whereas slower in A. philippinensis(2.91%) which will decompose within 89.69 days. The mean annual litterfall production in Mt. Apo falls within the range of evergreen tropical forest studies and is dominated by gymnosperm species. Further, this study implies that Mt. Apo, having evergreen trees, is an old forest ecosystem as its aboveground leaf component accounts for less than 70% of the total litterfall production.

Keywords: Gymnosperms, leaf N, P and K, litter turnover, oven-dry weight, tropical forest