Tree species diversity and stand structure along major community types in lowland primary and secondary moist deciduous forests in Tripura, Northeast India

Abstract

Tree species diversity and population structure at different community types were described and analyzed for primary and secondary lowland moist deciduous forests in Tripura. Overall 10,957 individual trees belonging to 46 family, 103 genera and 144 species were counted at ≥30 cm DBH (diameter at breast height) using 28 permanent belt transects with a size of 1 ha (10 m × 1000 m). Four different tree communities were identified. The primary forests was dominated by Shorea robusta (mean density 464.77 trees·ha−1, 105 species) and Schima wallichii (336.25 trees·ha−1, 82 species), while the secondary forests was dominated by Tectona grandis (333.88 trees·ha−1, 105 species) and Hevea brasiliensis (299.67 trees·ha−1, 82 species). Overall mean basal area in this study was 18.01m2·ha−1; the maximum value was recorded in primary Shorea forest (26.21 m2·ha−1). Mean density and diversity indices were differed significantly within four different communities. No significant differences were observed in number of species, genera, family and tree basal cover area. Significant relationships were found between the species richness and different tree population groups across the communities. Results revealed that species diversity and density were increased in those forests due to past disturbances which resulted in slow accumulation of native oligarchic small tree species. Seventeen species were recorded with <2 individuals of which Saraca asoka (Roxb.) de Wilde and Entada phaseoloides (L.) Merr. etc. extensively used in local ethno-medicinal formulations. The present S. robusta Gaertn dominated forest was recorded richer (105 species) than other reported studies. Moraceae was found more speciose family instead of Papilionaceae and Euphorbiaceae than other Indian moist deciduous forests. Seasonal phenological gap in such moist deciduous forests influenced the population of Trachypithecus pileatus and capped langur. The analysis of FIV suggested a slow trend of shifting the population of Lamiaceae group by Moraceae species in secondary T. grandis L. dominated community.