Effects of degradation on carbon stocks and structure of miombo woodlands: a case study of Mapogoro woodlands

Abstract

Miombo woodlands fonn an integral part of the rural landscape in Tanzania and play crucial role in providing wide range of products and ecological services including carbon sequestration. Woodlands and forests in Tanzania are going through great changes due to encroachment which cause a loss of approximately 420 OOOhaof forests and woodlands per year. This study aimed at assessing the effects of degradation on carbon stocks and stand structure ofmiombo woodlands in southern Tanzania. Data were collected from 100 rectangular plots (40mx20m), 50 plots in Manga Reserve and 50 in Mapogoro General land. Tree stump diameter, diameter at breast height (DBH), tree height and local and botanical names were recorded. Analysis was done by using Excel spread sheet and R software. Results showed that gradual tree removal from the woodland contributed to a loss of 3A±0.9 t C ha-' equivalent to 12.S±3.3 tC02e ha-' and 3.91±0.1 t C ha-' equivalent to 14.3±OA t C02e ha-' in Manga Reserve and Mapogoro general land, respectively. There was no significant difference in carbon loss between the two woodlands (p=O.OS) despite being under different management regimes. Standing volume was 33±0.3 m3ha-' and 28±2.9 m3 ha-' in Manga Reserve and Mapogoro general Land respectively. Basal area was S.0±0.3 m2ha-' and 4A±2.9 m2ha-' in the Manga reserve and Mapogoro General land respectively. Stem size distribution showed a reverse J shape implying active regeneration of the miombo woodlands. The annual wood removal was estimated at 6.63±3.0 m3 ha-' and 8.2±2.2 m3 ha-' in Manga reserve and Mapogoro general land, respectively which exceeds the mean annual increment (MAl) of miombo 1.88-4.35 m3 ha-' year'. There is a substantial carbon emission from the Miombo woodlands resulting from anthropogenic activities which is a threat to climate change mitigation through forest management. Managing the miombo woodland carbon stocks in Tanzania and elsewhere for reduction of CO2 emissions and climate change mitigation requires rigorous effort to reduce human related degradation.