Evaluation of Carbon, Nitrogen and Phosphorus in Disturbed and Intact Tropical Coastal Forest Sites in Tanzania

Abstract

This study investigated and established the variation of soil nitrogen, total carbon and phosphorus across closed forest; crop-agriculture and livestock disturbed sites. The study provides useful information for local management strategies. It sets initial basic data on the soil status of Uzigua Forest Reserve after 50 years of crop-agriculture and livestock grazing pressure. Forty-seven (50 m × 50 m) quadrats were established on each land uses for soil samples collection. Total nitrogen was analyzed by Kjeldahl acid-digestion, total carbon by the Walkley-Black procedures and phosphorus by Bray-II method. The mean values (percentage) were nitrogen = 16.07 ± 0.34, 1.75 ± 0.25, 6.5 ± 0.20; carbon =14.48 ± 0.23, 11.81 ± 0.13, 12.24 ± 0.30; phosphorus =14.12 ± 6.57, 17.74 ± 3.96, and 13.31± 2.86 for closed forest; agriculture disturbed and grazed sites respectively. There was a slightly lower amount of total carbon on crop agriculture disturbed sites than on the livestock grazed land uses. Carbon-nitrogen ratio was higher in closed forests than in the disturbed sites. The relationship between forest degradation and soil nutrient status is an indication that the below-ground nutrient pools are mainly determined by activities, which disturb the above-ground components mainly vegetation. To restore soil fertility status, it is important to establish the management of the disturbed sites through restoration of vegetation and minimization of disturbances.