Diospyros crassiflora (HIERN) surface and subsoil leaf litter decomposition pattern along a time gradient in a humid rainforest

Litter decomposition is a crucial bedrock of nutrient recycling, organic matter accumulation, soil physicochemical properties, biodiversity and life support of forest and agroforestry systems. We therefore investigated Diospyros crassiflora surface and subsoil leaf litter decomposition pattern along a duration gradient in a humid rainforest. The study was conducted in the nursery of the humid forest research station of the Forestry Research Institute of Nigeria (FRIN) in Umuahia, Abia State. One gram (1g) of D. crassiflora fresh leaf litter was placed on the surface and subsoil of 4kg of topsoil contained in 32cm x 20cm polyethene bags; there were a total of 108 bags in a completely randomized experimental design layout and the treatments were the duration gradient of litter decomposition which were: 2, 4, 6, 8, 10, 12, and 14 weeks; on each of the duration, litter was collected from nine of the polyethene bags for laboratory analysis and estimate of decomposition rate. The results showed a significantly high initial decomposition rate (3.19±0.13 %day-1; 4.28±0.03 %day-1) in the 2 week duration followed by significant continuous decline until the lowest (0.04±0.00%day-1; 0.28±0.02%day-1) in the 14 week in the surface and subsoil respectively. There was a positive correlation (r=0.80) in decomposition rate between the surface and subsoil leaf litter, which yielded a model with a significant R2 (0.64), for site-specific estimates of decomposition rate D. crassiflora leaf litter. A steeper and smoother subsoil cumulative percentage decomposition curve showed that leaf litter decomposition was significantly faster in the subsoil than surface soil.