Clay Content, Bulk Density and Carbon Storage Relationships in Mangrove and Rainforest Soils During Dry and Wet Seasons

Abstract

Evaluation of carbon stock in soil is an essential step in estimating the carbon storage potential of an ecosystem. A field study was carried out on a humid tropical Rainforest and Mangrove soils at the Forestry Unit of the Rivers State University Teaching and Research Farm and the Eagle Island quantify the effects of vegetation and seasons on soil organic carbon, organic carbon stock and other physical to attributes of the soils. Results revealed that seasons and vegetation did no change the soil texture, but influenced other properties of the soils. Bulk density was significantly low (p<0.05) at 0.64 g cm-3 in Mangrove soils in the peak of dry season. Saturated hydraulic conductivity (Ksat) was moderately rapid (20.88 cm h-1) in Rainforest soil, and moderately slow (15.59 cm h-1) in the Mangrove soils. Soil organic carbon (SOC) was significantly higher (p<0-05) in mangrove soils at 53 g kg-1 during the rains, and 16 g kg-1 in Rainforest soils during the same season. Soil organic carbon stock (SOCS) was significantly higher at 65.4 kg m-2 in Rainforest soils (p<0.05), compared to 8.4 kg m-2 in Mangrove soils during the same season. SOCS correlated positively bulk density (BD) (r = 0.679, p<0.05) and clay content (r = 0.892, p<0.01). The model: Y = 0.165+4.068x can be used to predict SOCS and bulk density, also the model Y = -0.246+0.361x can be used to predict the effects of clay content on SOCS in the two soils during the seasons. The Rainforest was found to have the potentials to store carbon in the soil than the Mangrove.