Impact of anthropogenic disturbance on species diversity and vegetation structure of a lowland tropical rainforest of eastern Himalaya, India

Impact of anthropogenic disturbance on species diversity and vegetation structure of a lowland tropical rainforest was studied in the foothills of Eastern Himalaya, India. Tree species richness,density, basal area and the diversity indices were found significantly(P<0.05) decreased with the increasing level of disturbances whereas, shrub density, basal area and herb density significantly increased with increasing disturbance level. In case of shrubs, Simpson's dominance index significantly(P<0.007) increased along the disturbance gradient,whereas Pielou's evenness index significantly(P<0.005) decreased with an increasing level of disturbance. Shannon-Weiner diversity index for herbs significantly(P<0.016) increased with increasing disturbance whereas, Simpson's dominance index was significantly(P<0.013) declined along the disturbance gradient. Results revealed that10-50 cm dbh classes constituted the highest stem density, and highest basal area was recorded in the >100 cm dbh class in all three sites. Density of the matured trees decreased with increasing DBH whereas, tree basal area tended to increase with increasing DBH in all three sites. Tree species richness was highest in the lower DBH classes.62.07% of the total tree species regenerated in the largely undisturbed site followed by 50% in the mildly disturbed and 26.32% in the highly disturbed site.The overall regeneration condition was found to be good in the largely undisturbed site. Mildly disturbed site exhibited fair regeneration and so was in the highly disturbed site. Discernable variations in species composition, diversity, regeneration and tree population structure revealed the impact of anthropogenic disturbances on rainforest vegetation dynamics. Higher degree of disturbance was furtherly found not only affecting species diversity but also promoting the growth of invasive weed species.Dominance of Hydnocarpus kurzii and Crypteronia paniculata in the highly disturbed site also indicated that these less-valued timber species may benefit from the vegetation mosaic produced by the disturbance; so differences in abundance of these species may be useful for bio-indication. Furthermore,present study suggests the need of adequate biodiversity conservation measures and adaptation of sustainable forest management approaches in disturbed areas of lowland tropical rainforest in the foothills of eastern Himalaya, India.

Assessment of Growth, Carbon Stock and Sequestration Potential of Oil Palm Plantations in Mizoram, Northeast India

A study was conducted to assess growth, carbon stock and sequestration potential of oil palm plantations along a chronosequence in Mizoram, Northeast India for which a total of 148 oil palms drawn from different age group plantations (1 to 11 years) were sampled for their biometric parameters and assessment of carbon stock through partial non-destructive methods. All the growth parameters of oil palm (trunk height, crown depth, total height, trunk diameter) and biomass drew from different parts of the palm showed a significant (p belowground biomass (BGB) > standing litter biomass > deadwood biomass > understorey biomass. AGB, BGB and deadwood biomass followed an increasing trend while understorey biomass decreased with age. An 11-year oil palm plantation accumulated 111.96 Mg ha-1 biomass with a carbon density of 49.90 Mg C ha-1 and could sequester 3.70 Mg C ha-1 year-1 in 10 years after planting in Mizoram, Northeast India. The findings showed considerable carbon storage with comparative higher values in oil palm plantations than shifting cultivation fallows. This will enable policy and decision makers in framing climate change mitigation and adaptation policies regarding the extension of oil palm plantations in Mizoram.

Effect of Land Use Changes on Carbon Stock Dynamics in Major Land Use Sectors of Mizoram, Northeast India

Land use change activities have greatly affected the total ecosystem carbon stock (TECS) and also contribute to global change through emission of greenhouse gases. The present study assessed the change in vegetation biomass carbon stock (VBCS) and soil organic carbon stock (SOCS) following conversion in major land use sectors (agriculture, agroforestry, forest and plantation) in Mizoram, Northeast India. SOCS was the highest in agroforestry (50.85 Mg C ha-1) and the lowest in agriculture (33.99 Mg C ha-1). VBCS was the highest in plantation (131.66 Mg C ha-1) and the lowest in agriculture (7.44 Mg C ha-1). The highest positive TECS change rate was observed when agriculture was converted to plantation (6.61 Mg C ha-1·yr-1), while negative rate of change in carbon stock was observed following the establishment of agriculture from other land use. A positive rate of change was observed in both VBCS and SOCS with TECS rate of 3.58 Mg C ha-1·yr-1 when agriculture got converted to agroforestry. The absolute carbon stock change rates were higher in VBCS than SOCS signifying the importance to maintain tree based vegetation cover.

Forest Dwellers’ Perception on Climate Change and Their Adaptive Strategies to Withstand Impacts in Mizoram, North-East India

We studied the perception of forest-dependent communities on climate change with its associated risk and their adaptation strategies in Mizoram, Northeast India. A total of 360 respondents (household heads) were randomly selected from 24 villages across the three different agro-climatic zones prevalent. The community perceived awareness of climate change phenomena in the region with a positive correlation between age, education and occupation of the respondents. The overall perception of climate change in temperature was medium (0.49), while low for change in precipitation (0.26) and seasonal durability (0.23). The community showed over-all low score of perception on risk of climate change (0.10) where risk on livelihood and socio-economic factors was higher than risk to environment or forest. Perception on impact of climate change was high for forest abi-otic ecological factors (0.66) and flora and fauna (0.62), while medium on livelihood of forest-dependent communities (0.44). The majority (more than 75%) of the respondents agreed that human beings are involved and responsible for climate change. Adoption of adaptive strategies to cope climate change ranged from 0.07 to 0.91, amongst which zero tillage, use of traditional knowledge, forest fire prevention, soil and water conservation techniques, agroforestry practices and social forestry are popular. However, rain water harvesting and investments for crop insurance were adopted on low scores clearly implied by the educational and socio-economic status of the farmers in the majority. The study brings out the knowledge and perceptions to climate change by forest-dependent communities and their adaptive strategies to cope had been assessed. The finding results seek the attention of researchers and policy makers to integrate technological and financial interventions in supporting farmer’s effort to cope with climate change with a long term objective for improving their livelihood and climate sensitive resources at the same time.

Vegetation and ecosystem carbon recovery following shifting cultivation in MizoramManipur-Kachin rainforest eco-region,Southern Asia

Background:Shifting cultivation(locally known as“jhum”)is a major driver of deforestation and loss of ecosystem services in rainforests.For developing any effective conservation of biodiversity and carbon service program,an indepth understanding to the recovery of vegetation and carbon after abandonment of jhum is essential.We estimated species richness,abundance and composition of trees,shrubs and herbs,carbon distribution in aboveground and belowground components along a chronosequence of jhum fallow in northeast India,and elucidated the factors affecting the recovery processes of jhum fallows.Methods:Species composition and other plant community attributes,carbon storage in different pools were studied in 5 jhum fallows(<5,5-10,11-15,16-20,21-25 years old)and an old-growth forest.The data were subjected to linear mixed effect modeling using R-package“nlme”for identifying the important factors contributing to the recovery of vegetation and carbon.Results:Species composition varied significantly(P<0.05)between jhum fallows and old-growth forest.Tree density varied from 28 stems ha−1 in 5 years old jhum fallow to 163 stems ha−1 in old-growth forest.Both biomass carbon in all components and soil organic carbon were significantly(P=0.01)lower in jhum fallows than in the old-growth forest except living non-woody biomass component.The recovery of aboveground biomass carbon was faster during early successive years than the mid-successive jhum fallows.Total ecosystem carbon and soil organic carbon stock in the oldest jhum fallow was 33%and 62%of those in the old-growth forest,respectively.The fallow age was found to be the most important explanatory factor in the recovery process of vegetation and carbon stock in re-growing fallows.Conclusion:The shifting cultivation fallows gradually recovered both vegetation and carbon and are potential repository sites for biodiversity conservation,which may take much longer time to reach up to old-growth forest in northeast India.