Decomposition, nutrient release patterns and nutrient fluxes from leaf litter of secondary forests in Ghana

Abstract

Studies were conducted on leaf litter fall, decomposition, nutrient release patterns and nutrient fluxes of Akyaakrom (AS) and Dopiri (DS) secondary forest leaf litter in Dwinyama watershed. Leaf litter production were 9.1 and 6.8 t ha^-1 y^-1 in AS and 8.9 and 6.5 t ha^-1 y^-1 in DS in the 1st (September 1998-August 1999) and 2nd (September 1999-August 2000) years, respectively. Mean annual leaf litter production were 7.9 t ha^-1 in AS and 7.7 t ha^-1 in DS. Leaf litter fall was higher in the drier months (December-April) and lower in rainy months (June-September) in each year. Decomposition pattern of leaf litter did not show clear relation to the monthly rainfall. The leaf litter of Griffornia simplicifolia (legume) in AS showed rapid decomposition, and was decomposed by more than 90 per cent of its dry mass within 6 months of exposure on the soil surface. In DS, another leguminous tree species, Albizia zygia, showed slower decomposition than G. simplicifolia. Albizia zygia had a higher concentration of total extractable phenols (TEPH) than did G. simplicifolia. Mean annual N fluxes from the decomposed leaf litter to the soil were estimated as 170 and 226 kg ha^-1 in AS and DS, respectively; and mean annual P fluxes were 5.3 and 5.2 kg ha^-1 in AS and DS, respectively. Annual fluxes of K were 40 and 12 kg ha^-1. Annual fluxes of Ca were 114 and 142 kg ha^-1 in AS and DS, whilst Mg were 18 and 39 kg ha^-1, respectively. The peak monthly fluxes of all the nutrients were mostly observed during March to June, overlapping with the rainy season. Monthly fluctuations of N fluxes were more pronounced. Nutrient imbalances of P and Ca fluxes from decomposed leaf litter in the forests suggested their scarcities. Temporal N starvation in May in AS, pronounced fluctuation of N fluxes and nutrient imbalances may indicate the degradation of the ecosystems of the two forests.

Ghana Journal of Science Vol. 44, 2004: 59-72