Species allometric models and the effect of wildfires on carbon sequestration and floristic diversity in miombo woodlands of Kigoma region

This study was conducted in order to develop specific allometric models and assess the impact of wildfires on carbon stock and plant species diversity in miombo woodlands of Kigoma Region. Three forests namely Kitwe, a fire suppressed forest, Mgaraganza, a less frequently burnt forest and Ilunde, a frequently burnt miombo were used in this study. Plant species diversity was determined using ShannonWiener diversity index and compared statistically, while similarity of plant species was compared using Czekanowski’s similarity coefficient. Community structure to include stocking rate and basal area was compared among the forests. Vegetation carbon stock was estimated using biomass allometric model so far developed for miombo woodlands and compared using ANOVA. Sequestered carbon in the soil was obtained by using Walkley-Black method. The satellite remotely sensed data of the above-ground carbon was compared with the ground-truthing above-ground carbon data. Linear regressions were used to develop above-ground carbon allometric models for Diplorhynchus condylocarpon and Pseudolachnostylis maprouneifolia. The similarity coefficients were low in all three forests. The most diverse forest was Ilunde, while the least diverse was Mgaraganza forest. Highest stocking rate was recorded in Mgaraganza forest while the lowest was recorded in Ilunde forest. The highest basal area and stock of carbon in vegetation and soils were estimated in Kitwe forest, while the lowest were estimated in Ilunde forest. The above-ground carbon stock obtained by ground-truthing exceeded the remotely sensed carbon in all forests studied. The best fit allometric model in D. condylocarpon was obtained when DBH was used only as the predictor variable. For P. maprouneifolia, both DBH and H were used as predictor variables. It can be concluded that rampant wildfires altered species composition and structure, thereby increasing the diversity of plant species. Since the negative effect of wildfires is species-specific and involves litter reduction, the overall effect is the reduction of vegetation and the soil carbon. High plant species diversity and composition under enhanced vegetation and soil carbon sequestration when early dry season fire is applied requires further studies. For accurate estimations of carbon stock at regional and global scale, many species-specific allometric models should be developed.