Relationship between forest biodiversity attributes and potential carbon stocks in dry tropical reserve forests of Assam, northeast India

Abstract

Potential forest carbon stocks are significantly correlated to forest biodiversity attributes such as diversity, density, and richness. However, there is little such information on dry tropical reserve forests of Assam, a state in northeast India. We studied this relationship in two reserve forests. Pearson correlation, cluster analysis, and regression analysis were used to explore these relationships. The estimation of plant carbon stocks was made using both destructive methods for herbaceous and non-destructive allometric methods for trees. The most dominant plant species in the Bhomoraguri reserve forest were Cynodon dactylon, Datura stramonium, Clitoria ternatea, and Tectona grandis for grasses, forbs, climbers, and trees, respectively. Cymbopogon nardus, Colocasia esculenta, Mikania micrantha, and Shorea robusta, were dominant species in the Balipara reserve forest for grasses, forbs, climbers, and trees, respectively. The presence of Lantana camara, Smilax ovalifolia and Piper betle in the studied forests suggests disturbed ecosystems. Other observed species such as Aristida spp., Cenchrus spp., Ipomoea cheirophylla, and Sida spp. are indicators of disturbed ecosystems as well. The biomass stock differed significantly among plant growth forms. Carbon stocks were 302.93 and 283.97 t ha^–1 in the Bhomoraguri reserve forest and Balipara reserve forest, which were equivalent with 555.87 and 521.30 t ha^–1 of CO₂ sequestration, respectively. Tree species contributed the greatest amount (54.80%), followed by forbs (21.36%), climbers (19.35%), and least for grasses (4.49%). Correlation analysis indicated a strong positive relationship between the density of trees and climber species with carbon stock potentials, suggesting that increase of their density favoured carbon sequestration in forest ecosystems. Diversity of grasses was negatively correlated with potential carbon stock in the examined forests. The unique contribution of each group to carbon stock was 91.8, 58.01, 51.3, and 11.11% for climbers, trees, grasses, and forbs, respectively. Thus, it is important to examine biodiversity attributes in estimation of forest carbon stocks.