Joyeeta Singh Chakraborty

Warming-induced expansion in vegetation coverage and activity can accelerate the montane hydrological regimes. However, the climate impacts on ecohydrology of forested valleys of the Himalaya are uncertain. In this study, utilizing results of about three centuries of cellulose isotope chronologies (δ¹³C andδ¹⁸O) of dominant tree species, geo-chronological proxies, bio-geophysical dataset and simulations including satellite observations, we show an activation in the ecophysiological processes including evapotranspiration (ET) since the 1950s. Observation suggests rapid greening, while isotopic records indicate enhanced assimilation and transpiration in deciduous species vis-à-vis conifers post 1950s. Given strong vegetation-precipitation feedback and superimposed on the increasing trends of conducive atmospheric factors affecting valley-scale convective processes, intensification in forest ET is manifesting in a progressive enhancement in extreme rainfall events (EREs) since the last few decades. Results suggest that representation of ecophysiological processes and dynamics of seasonal moisture loading in observational and modelling framework is critical for understanding EREs under climate change.

Sustainable food system ensures adequate and safe food supply in an eco-friendly manner. We assessed food sustainability perception and practices of local community through structured interviews in sub-alpine settlements of Uttarakhand Himalaya. Major perceived challenges towards food sustainability were identified using Rank-Based Quotient analysis. Association with various socio-demographic factors (e.g., age, gender, education, socio-economy, and socio-culture) was tested. An overall neutral perception (mean score 2.9) and moderately sustainable practices (mean score 3.1) were observed. Respondents with higher socio-cultural score showed more sustainable food sourcing practices and more positive social and economic sustainability perception, as well as higher participatory willingness. Female respondents were more dependent on sustainable food sources than the males. Education level influenced food quality choice. People identified higher food production cost as major economic constraint; while small landholdings and labor migration were main social challenges. Land and water management issues and climate uncertainty were the major environmental constraints. Socio-cultural exposure played significant role in ranking these sustainability constraints. We encourage direct involvement of socio-culturally active people and conducting extensive outreach programs for future sustainable local food system in vulnerable Himalayan valleys.

Mound-building termites are ecosystem engineers whose abundance and spatial ecology are not adequately addressed in many forest ecosystems. We studied Odontotermes obesus mounds at two moist tropical deciduous forests (pure Sal and Sal-Teak mixed) in the Doon valley, northern India. Mound abundance, spatial pattern and termite population density were determined by direct count, nearest neighbour analyses and destructive sampling, respectively. Relations between mound attributes and stand characteristics such as woody vegetation diversity, density and tree stumps (representing food quality, quantity, open-space availability and disturbance) were tested at fine spatial scale using regression analyses. Active mounds were more abundant in the pure Sal stand (~8.0 mounds/ha) than in the mixed stand (~5.0 mounds/ha). Mean population density (both sites combined) was 2.01 × 10⁵ individuals per mound. Population density was strongly correlated with mound volume. Predominance of young colonies was indicated by high occurrence (≥ = 65%) of small mounds (< 1.25 m³). Mounds were predominantly randomly distributed. However, the pure Sal stand showed a partial tendency towards aggregation. Our results revealed that woody species richness is an important, site-specific regulatory factor. Local-scale variations should be cautiously considered while up-scaling the contribution of O. obesus mounds to various ecosystem processes.

Carbon cycle studies over the climate-sensitive Himalayan regions are relatively understudied and to address this gap, systematic measurements on carbon balance components were performed over a deciduous pine forest with an understory layer. We determined annual net carbon balance, seasonality in components of carbon balance, and their environmental controls. Results indicated a strong seasonality in the behavior of carbon exchange components. Net primary productivity (NPP) of pine forest exceeded soil respiration during the growing phase. Consequently, net ecosystem exchange exhibited a net carbon uptake. In the initial phase of the growing season, daily mean uptake was −3.93 (±0.50) g C m⁻² day⁻¹, which maximizes (−8.47 ± 2.3) later during post-monsoon. However, a brief phase of carbon release was observed during peak monsoon (August) owing to an overcast condition. Nevertheless, annually the forest remained as a carbon sink. The understory is extensively distributed and it turned out to be a key component of carbon balance because of sustained NPP during the pine leafless period. Temperature and evaporative fraction exhibited a prime control over the seasonal carbon dynamics. Our observations could lend certain useful insights into the application of coupled climate-carbon cycle models for the Himalaya and ecological functions in the region.