Characterizing plant biomass and soil parameters under exotic trees within rainforest environment in southern Nigeria

This research characterized biomass and soil parameters under exotic species of Terminalia cattapa, Mangifera indica and Persea gratissima in Southern Nigerian rainforest environment. The study area was stratified into 5 zones. In each zone, control plot measuring 30 m × 30 m and divided into 3 quadrants of 10 m × 30 m, was established from mature adjoining rainforest above 100 years, while 3 stands of each exotic species were selected. Collection of plant biomass parameters and soil samples was from 15 stands of each exotic species and control plots. Litterfall was collected daily from February 2019 to January 2020 using litter traps, heights and diameters of trees were determined using appropriate methods, while samples of soil were taken from the 0–15 cm and 15–30 cm depth using core sampler. Soil properties were analyzed by adopting standard laboratory techniques. Data analysis involved the descriptive, correlation and one-way analysis of variance (ANOVA) statistics using the SPSS 15.0 version software. Findings revealed that plant biomass and soil parameters varied significantly at 5% level of significance among the exotic and rainforest trees. Litter productions varied seasonally. Plant biomass characteristics correlated positively with soil properties. Litter production correlated with water holding capacity, total porosity, organic matter, nitrogen, phosphorus and potassium at 0.559, 0.652, 0.818, 0.805, 0.902 and 0.743 respectively for topsoil and 0.549, 0.631, 0.807, 0.801, 0.900 and 0.732 respectively for subsoil. Since the biomass parameters of the exotic trees correlated positively with soil properties, they are therefore recommended as farm trees to encourage agro-forestry practices within the rainforest environment. These agro-forestry practices prevent inorganic fertilizers' usage which is not environment friendly.