Litterfall and Nutrient Returns in Isolated Stands of Terminalia catappa Trees in the Rainforest Area of Southern Nigeria
This study assesses litter production, concentrations and returns of nutrient elements with respect to seasons, so as to provide empirical information on nutrient flux by the isolated exotic stands of Terminalia. Litterfall samples were collected from the isolated stands of Terminalia catappa and adjoining native rainforest which serves as control for the experimental research for 12 months. Data collected were analyzed in the laboratory and the results were subjected to both descriptive and inferential statistical analyses using the SPSS 15.0 version. Average litter production for the Terminalia catappa and the adjoining rainforest were 83.04 g/m²/yr and 77.31 g/m²/yr respectively. Results of the Independent Samples T-Test showed significant difference in litter production, nutrient concentrations and the returns of nutrient elements via litterfall between the two sample sites (P value). Both litter production and the return of nutrient elements varied with the seasons of the year. While Terminalia catappa stands produced the highest litter in the months with heavy rainfall, the adjoining rainforests produced the highest litter in the dry season months. The order of nutrient elements return via litterfall by Terminalia catappa stands was Ca > N > K > Mg > P > Na, while that of the adjoining rainforest was N > Ca > K > Mg > P > Na. Results of Pearson’s bivariate analyses showed significant positive relationships between litter production and nutrients return through litterfall at the 5% levels, with the correlations ranging between 0.984 – 0.999 in Terminalia catappa stands and 0.944 – 0.991 in the adjoining rainforest. Therefore, the cultivation of Terminalia catappa which is an exotic tree species to this study area has implications in returning nutrient elements to the soils of the rainforest ecosystem.
Keywords: Litterfall, Nutrient returns, Seasonal variation, Southern Nigeria, Terminalia catappa, Tropical rainforest.