Tree species diversity and biomass carbon assessment in undisturbed and disturbed tropical forests of Dibru-Saikhowa biosphere reserve in Assam North-East India

Abstract

In the present study, the tree species phytosociological attributes, tree density, basal area, and tree biomass carbon (above- and below-ground) distribution pattern was explored in the undisturbed and disturbed forest sites in Dibru-Saikhowa biosphere reserve of Assam, northeast India. The study area is globally recognized biodiversity hotspots in India and situated in the flood plain of the Brahmaputra and Lohit River. The tree species attributes like tree density, basal area, and tree biomass carbon were estimated in three undisturbed and disturbed forest sites. Principal component analysis, redundancy analysis, and correlation analyses were conducted to explore the relationship between biodiversity indices, forest stands characteristic, and tree biomass. The undisturbed forest stand showed the highest biological attributes (29–39 species and 25–33 genera) compare to disturbed forest stands (27–32 species and 21–27 genera). Combretaceae, Lauraceae, Phyllanthaceae, Salicaceae, Myrtaceae, and Moraceae has shown a higher importance value index. The biodiversity indices were significantly higher in undisturbed forest stands and the Shannon–Wiener diversity index (H′) ranged from 1.97 to 3.57, Simpson index (Cd) ranged from 0.76 to 0.88, and evenness index (e) ranged from 0.65 to 0.97 in all the stands. The mean tree density and forest basal area were significantly higher in the undisturbed forest (796.66 ha−1 and 56.56 m2 ha−1, respectively) compared to disturbed forest stands (436.66 ha−1 and 38.91 m2 ha−1, respectively). Tree biomass carbon in undisturbed forest (184–214.62 Mg C ha−1) was also more than disturbed forests (124–137.53 Mg C ha−1). Moreover, the biomass carbon was greatly affected by the tree composition, diversity, density, and the disturbances in forest stands. The present study will provide the baseline information for effective and sustainable tree species diversity conservation and evaluate tree carbon stock in the Dibru-Saikhowa biosphere reserve.