SPATIO-TEMPORAL SCORCHED LAND AND RESULTANT SEQUESTERED SOIL ORGANIC CARBON IN SELECTED MIOMBO WOODLANDS OF WESTERN TANZANIA

Ecological impacts of soil degradation in forests have been variably reported. The present study aimed at exploring the consequence of fire extent on the sequestration of soil organic carbon. Data for scorched land was captured by Landsat in Kitwe and Ilunde forests with different levels of fire extent in western Tanzania. Both forests were severely disturbed previously. Soil samples were collected from thirty plots located 150 m and 100 m apart in Ilunde and Kitwe forests respectively, for determination of soil bulky density and percentage organic carbon. In each plot soil samples were collected from four points, thereafter treated differently depending on the purpose of sampling. Percentage organic carbon was obtained using Walkley-Black method, and then the sequestered soil organic carbon was estimated in tonnes per hectare as a product of percentage organic carbon, soil depth and bulky density. The difference in sequestered soil organic carbon between the two forests was analyzed using t-test. Spatio-temporal scorched and vegetated land lands of the forests were produced from satellite images after computing Normalized Difference Vegetation Index (NDVI) for the years 1990, 2000 and 2011. In 30 cm soil depth, more soil organic carbon of 17.9 ± 0.9 t ha- (two folds) was recorded from Kitwe than Ilunde forests (P < 0.01, t = 9.935, D.F. = 29). In Ilunde forest, the extent of fire increased with time, while scorched and vegetated lands increased and decreased with time respectively. In Kitwe forest, the trend was opposite whereby the scorched land decreased and vegetated land increased with time. Prevalence of wildfires over large areas in forests lowers soil organic carbon sequestration. The contribution of ash in enrichment of soil organic carbon sequestration in forests could be only overstated.