Tree diversity and carbon stock in a subtropical broadleaved forest are greater than a subtropical pine forest occurring in similar elevation of Meghalaya, north-eastern India

Studies on relationship between tree diversity and carbon stock has not been consistent. The present study was undertaken to quantify and compare the plant diversity and carbon stock in a subtropical broadleaved and a subtropical pine forest of Meghalaya, northeast India. Biomass-based carbon estimation was undertaken in two subtropical broadleaved forest stands viz., Mawnai (MBF) and Nongkrem (NBF) and adjacent Pinus kesiya dominated forest stands (MPF and NPF), occurring in similar topography, climatic conditions and soil type. The aboveground and belowground tree biomass was estimated using existing allometric models. Carbon was estimated as 47.4% of the total biomass. Tree species richness was greater in the subtropical broadleaved forest stands at MBF and NBF (117 and 21 species) than in the adjacent pine forests, MPF and NPF (15 and 16 species). The density values were 1294 and 1127 individuals ha(-1) in the broadleaved forest stands, and 894 and 1032 individuals ha(-1) in the adjacent pine forest stands, respectively. The broadleaved forest stands, MBF and NBF had tree biomass carbon stock of 140.4 Mg C ha(-1) and 133.6 Mg C ha(-1), respectively, which were significantly greater (F = 26.6; P < 0.05) than the pine forest stands, MPF and NPF (74.7 Mg C ha(1) and 63 Mg C ha(-1)). The contribution of trees belonging to the higher DBH classes (> 66 cm) to the total biomass carbon was greatest in MBF, while the lower diameter trees belonging to 5-15 cm and 16-25 cm were the major contributors to the total biomass carbon in the pine dominated stands.