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Forest's ecosystem is changing at an alarming rate and anthropogenic alteration of forests to other land use is a major driver of carbon (C) emission and biodiversity loss. We estimated ecosystem-level C stock and factors affecting C stock in six major forest types; tropical wet evergreen forest, montane subtropical forest, temperate forest, bamboo forest, quercus forest, and jhum land of the eastern Himalayan region (India). We determined ecosystem structure, biodiversity, and plant and soil C stock by laying random plots in each forest site. The average C stock was estimated in the range of 79.0-373.4 Mg C ha -1 and found significantly different among the forest types. Partitioning ecosystem C stocks in plant (24-55%), soils (43-75%), deadwood (1-4.8%) and litter (0.20-1.25%) components varied largely. Pearson correlation analysis shows a significant positive relation of basal area with species diversity, tree density, and ecosystem C stock. Linear mixed-effect model demonstrates the high influence of species density and soil moisture content on the ecosystem C stock. We recommend the inclusion of forest structural attributes and pedological characteristics while predicting synergies between C stock and future climatic conditions. Additionally, conversion of natural forests to jhum land should be minimized because they stored lesser ecosystem C stocks thus plays a minimum role in C accumulation and cycling. The study provides estimates of C stocks in major forests that can be useful in suggesting a path forward to partially fulfill India's commitments to REDD + policy., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Globally, while experts debated whether planted forests (PF) restore biodiversity or create biological deserts, their potential role in mitigating climate change is mostly overlooked. In this study, we investigated the long-term impact of PF on the species composition, plant diversity, biomass stock, and carbon (C) storage potential in the Brahmaputra flood plain of North-East India. The phytosociological study was conducted using a modified Gentry plot method and species-specific allometric models were used to estimate biomass stock in the 39-year old PF and equivalent age of natural forest (NF). We identified 57 trees, 22 shrubs, and 23 herb species in the PF, and 54 trees, 17 shrubs, and 8 herb species in the NF. Species richness and biodiversity indices showed greater values in PF whereas species dominance and evenness were higher in NF. After 39-year of plantation, total biomass C was estimated at 165 Mg C ha -1 in PF and 197 Mg C ha -1 in equivalent age of NF. Bombax ceiba, Dalbergia sissoo, Samanea saman, Tetrameles nodiflora, and Gmelina arborea were the dominant tree species that contribute 56% of the total biomass C in the PF. The ecosystem carbon pool (plant biomass + deadwood + litter + SOC) was 17% higher in NF and showed the greater potential of carbon dioxide sequestration (959 Mg CO 2 ha -1 ) compared to the PF (818 Mg CO 2 ha -1 ). Our study suggested PF in flood plain degraded lands can act as a major C sink and stored a substantial amount of carbon dioxide after 39-year of the plantation. It is concluded that PF can be a preferable ecosystem management tool to fulfill the objectives of biodiversity conservation and provisioning climate services like C sequestration., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Soil organic carbon plays an important role in the stability and fertility of soil and is influenced by different management practice. We quantified active and passive carbon pools from total soil organic carbon (TOC) in seven different land use systems of northeast India. TOC was highest (2.75%) in natural forest and lowest in grassland (1.31%) and it decreased with increasing depth in different pools of lability. Very Labile Carbon (VLC) fraction ranged from 36.11 to 42.74% of TOC across different land use system. Active carbon (AC) pool was highest in Wet Rice Cultivation (61.64%) and lowest (58.71%) in natural forest. Higher AC pools (VLC and less labile) in most land use systems barring natural forests suggest that the land use systems in the region are vulnerable to land use change and must adopt suitable management practice to harness carbon sequestration., Competing Interests: The authors have declared that no competing interests exist.