Aboveground Woody Biomass, Carbon Stocks Potential in Selected Tropical Forest Patches of Tripura, Northeast India

To estimate woody plant biomass stocks in different patches of forest ecosystems, total 20, 500 × 10 m (0.5 ha) sized line transects were laid in a protected area of Tripura, Northeast India. Overall, 9160 individuals were measured at ≥10 cm diameter at breast height (dbh) in 10 ha sampled area. Estimation of biomass suggested that highest coefficient for allometric relationships between density and biomass in 10 dbh classes was observed in bamboo brakes (R2 = 0.90) than lowest for semi evergreen patch (R2 = 0.48). The stock of carbon (C) was differ significantly along the forest patches (F = 7.01, df = 3.19;p < 0.01). Most of biomass stock (69.38%) was accumulated in lower dbh class (<30 cm) and only 23% of biomass was estimated at higher dbh classes (> 70 cm). Range of biomass stock (37.85 - 85.58 Mg ha-1) was low, compared to other tropical forest ecosystems in India, which implies that the proper management is required to monitor regional ecosystem C pool.

Effects of land use on the Soil Organic Carbon storage potentiality and soil edaphic factors in Tripura, Northeast India

The regulatory functions of soil are getting attention among the scientists and Soil Organic Carbon (SOC) is an important indicator of soil health. The impact of differential use of land on SOC and other edaphic properties were analysed in three important Land use land cover (LULC) system of Tripura, northeast India. Soil cores were divided into four depth profiles (0 - 10, 10 - 30, 30 - 50 and 50 - 100 cm) to observe the changes of edaphic properties into the soil depth gradient. Our results suggest that SOC in the top profile of Managed Plantation (MP) and Jhum Fellow (JF) was 51.68% and 48.55%, less than Natural Forest (NF). From 0 - 10 to 10 - 30 cm soil depth, 43.3%, 8.4% and 39.4% decrease in NF MP and JF found. Total stock of SOC (Mg C·ha﹣1) was found highest in JF (121.87), followed by NF (117.12) and MP (85.34). In top profile, conversion of NF into MP and NF into JF led to 39% and 11% decrease in SOC. The significant variation in SOC stock was found among different LULC under this study (F2,12 = 16.94, P ≤ 0.001). In 0 - 10 cm soil depth, maximum value of bulk density (gm·cm﹣3) was found in MP (1.39) followed by JF (1.27) and NF (1.23). In top profile, significant variation was found among LULC (p < 0.001). Soil pH and moisture content significantly varied (p < 0.05) in 0 - 10, 10 - 30 and 50 - 100 cm soil depth. In contrast to that significant change in soil temperature was found at 30 - 50 cm (p < 0.001) and 50 - 100 cm (p < 0.001). It was observed that JF had highest overall SOC stock than NF and MP. Conversion of NF into MP and JF results significant loss of SOC at 0 - 10 and 10 - 30 cm depth profile. We also found that NF conversion had significant impact on the change in the soil C pool.

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

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 accumu- lation of native oligarchic small tree species. Seventeen species were recorded with 〈2 individuals of which Saraca asoka （Roxb.） de Wilde and Entada phaseoloides （L.） Men＇. etc. extensively used in local ethnomedicinal 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.

Effects of anthropogenic disturbances on vegetation diversity and structure:a case study in the remnant forests surrounding the village ecosystems of Tripura,Northeast India

The types,frequency,and intensity of human interference with forests markedly affect the vegetation dynamics.Assessment of the impact of anthropogenic disturbances on forest diversity and structure is one of the central issues related to human behaviour and forest ecosystems and management.Both species diversity and density are very sensitive to local anthropogenic disturbance,which can be reduced depending on land-use systems.We used 10 line transects of 500 x 10 m to record and measure all plants >10 cm girth in some of the remaining forests surrounding villages in Tripura,Northeast India.To predict the effects of anthropogenic pressure on species richness and forest structure,we recorded and scored all ongoing disturbances in all transects of the forests.Although our study did not show any significant effects on the mean number of species,all diversity indices were significantly affected by disturbance.Total stem density(F = 128.60,p < 0.0001) and basal area(F = 65.30,p < 0.0001) of the forest stands were significantly affected by disturbance.Disturbance significantly(F= 84.81,p < 0.0001) impacts the abundance of mature voluminous trees removed by extensive illegal logging.Further,stem density at the middle(F= 10.01,p < 0.05) and upper(F= 131.70,p < 0.0001) canopy stories was also reduced by high disturbance intensity.The present analysis will be useful to policy-makers and planners for implementation of sustainable forest management at both the local and regional scale.

Changes of woody species diversity, horizontal and vertical distribution of stems across interior to outside within a primate rich habitat of Northeast India

The interior forest of protected area（PA）recover quickly in terms of greater diversity and structural complexity than peripheral and outsides, which may be due to high plant-frugivore interactions in the interior forest than the disturbed outsides. To describe the structural and functional differences in tree communities from interior to outside forests with in small PA, we quantitatively analyzed the vegetation of Trishna Wildlife Sanctuary, a rich primate habitat of Northeast India. Vegetation was sampled at C10 cm girth at breast height by 10 m 9 500 m sized20 line transects（10 ha） laid in the interior（N = 7）,peripheral（N = 7） and outside（N = 6） zones of this sanctuary. All transects were ordinated by Principal Component Analysis based on correlation between diversity and existing disturbance indices. We found significant differences（P ／ 0.05） in taxonomic richness and diversity indices between the habitat. Van diagram confirmed greater unique species richness in the interior zone（64） than peripheral（28） and outside（6） zones. Overall density（ha-1） did not differed across the zones, but basal area（m2ha-1） was significantly（P ／ 0.01） high in peripheral zone. Vertical distribution of stem density was linearly declined across zones（r2adj[ 0.70; P ／ 0.01） with increase in the canopy height. Horizontal distribution of adult stems showed significant inverse quadratic relationship（r2adj[ 0.80; P ／ 0.001）, which suggests very low density of canopy forming voluminous trees in the interior zone.Immediate protection, restoration and management of interior regions are required to preserve local plant genetic diversity and also to maintain suitable habitat for threatened wildlife.

Effects of patch size, disturbances on diversity and structural traits of tropical semi-evergreen forest in the lowland Indo Burma hotspot: implication on conservation of the threatened tree species

Information on geographic distribution, population and threat status of most globally red listed species in the Indo Burma zone are inadequate. Given the increase in the prevalence of isolated forest patches in the part of this hotspot, evaluation is necessary on how size of the remnant forest patches and on-going disturbances affects structure and diversity of remaining habitats including the population of some globally threatened tree species. Quantitative vegetation inventory by 500 m long and lO m wide （0.5 ha） line transects were randomly set in nine fragmented tropical semi-evergreen forest patches in Tripura, Northeast India. The studied forests patches grouped into small, medium and large based on their respected sizes. Spatial variability was analysed in woody species diversity and structure along the patch size gradients and their response to both patch size and anthropogenic disturbances. Out of 167 species, 13 identified as red-listed species by IUCN under the present inventory. Most of the diversity and structural parameters showed statistically significant positive response with the forest patch size, except for stand dominance, disturbance, sapling density and number of aggregated distribution pattern decreased when patch size increased. In addition, most of the diversity and structural attributes showed negative response with disturbances. Present baseline data would serve as an effective tool for management and protection of this important forest type. Future habitat restoration programme and strategies for relocation of additional population and re-introduction of those globally threatened trees are recommended.