House-warming: Wild king cobra nests have thermal regimes that positively affect hatching success and hatchling size

Incubation temperature in nests of oviparous reptiles affects reproductive success indicators, including hatching time and success, offspring size, fitness, and behaviour. The female king cobra builds an above ground nest to incubate and protect its eggs. However, it is not clear how thermal regimes inside king cobra nests respond to external environmental temperature regimes, especially in subtropical regions that witness high diel and seasonal temperature fluctuations. To better understand the relationship between inside nest temperatures and hatching outcomes for this snake, we monitored the thermal regimes of 25 natural king cobra nests in the subtropical forests of the Western Himalayas in Uttarakhand state, northern India. We hypothesized that inside nest temperatures would be higher than outside (ambient) temperatures and that thermal regimes inside nests would affect hatching success and hatchling size. Internal and external temperatures at nest sites were measured every hour until hatching, via automatic data loggers. We then calculated hatching success of eggs and measured hatchling length and weight. Mean inside nest temperatures were consistently higher by about 3.0 °C than outside environmental temperatures. External temperature reduced with increasing elevation of nest sites and was the best determinant of inside nest temperature, which had a smaller range of variability. Physical characteristics of nests (size and leaf materials used) did not influence nest temperature significantly, but nest size was positively related to clutch size. Mean inside nest temperature was the best predictor of hatching success. Average daily minimum nest temperature, which indicates a possible lower threshold for thermal tolerance by eggs, was also correlated positively with hatching success. Mean daily maximum temperature was a significant predictor of mean length of hatchlings, but not of mean hatchling weight. Our study provides unequivocal evidence for the critical thermal benefits of king cobra nests for increased reproductive success, in subtropical environments with lower and sharply fluctuating temperature regimes.

Surface ozone in the Doon Valley of the Himalayan foothills during spring

Elevated ozone (O₃) pollution is observed every spring over the Northern Indian region including the Himalayan foothills, with a maximum typically in the month of May. However, studies investigating influences of photochemistry and dynamics in the valleys of Central Himalaya are limited. Here, in situ surface O₃ observations conducted at Dehradun (77.99° E, 30.27° N, 600 m above mean sea level) in the Doon Valley during April-July 2018 are presented. These O₃ observations reveal the prevalence of an urban environment over Dehradun with enhanced levels during noontime (66.4 ppbv ± 11.0 ppbv in May) and lower levels during night (26.7 ppbv ± 11.5 ppbv). Morning time O₃ enhancement rate at Dehradun (7.5 ppbv h^-1) is found to be comparable to that at Bode (7.3 ppbv h^-1) in another valley of Himalayan foothills (Kathmandu), indicating stronger anthropogenic emissions in the Doon Valley as well. Daily average O₃ at Dehradun varied in the range of 13.7-71.3 ppbv with hourly values reaching up to 103.1 ppbv during the study period. Besides the in situ photochemical O₃ production, the entrainment of O₃-rich air through boundary layer dynamics also contributes in noontime O₃ enhancement in the Doon Valley. Monthly average O₃ at Dehradun (49.3 ppbv ± 19.9 ppbv) is observed to be significantly higher than that over urban sites in Northern India (35-41 ppbv) and Bode (38.5 ppbv) in the Kathmandu Valley during May. O₃ photochemical buildup, estimated to be 30.3 ppbv and 39.7 ppbv during April and May, respectively, is significantly lower in June (21.2 ppbv). Copernicus Atmosphere Monitoring Service (CAMS) model simulations successfully reproduce the observed variability in noontime O₃ at Dehradun (r = 0.86); however, absolute O₃ levels were typically overestimated. The positive relationship between CAMS O₃ and CO (r = 0.65) together with an O₃/CO slope of 0.16 is attributed to the influences of biomass burning besides anthropogenic emissions on observed O₃ variations in the Doon Valley. O₃ observations show an enhancement by 35-56% at Dehradun during a high-fire activity period in May 2018 as compared to a low-fire activity period over the Northern Indian region in agreement with the enhancement found in CAMS O₃ fields (10-65%) over the region in the vicinity of Dehradun.

Elevated temperature modulates rice pollen structure: a study from foothill of Himalayan agro-ecosystem in India

Rice cultivation is practiced in various agro-climatic zones ranging from tropical to temperate. Anthesis is a critical stage for deciding productivity which is controlled by numerous biotic and abiotic stresses. Elevated temperature is one of the key abiotic stresses that adversely modulate the pollen formation and structure, i.e., infertility, results in productivity decline. The present study was conducted to investigate the effects of elevated temperature on morphological changes in pollen grains of rice grown in temperature gradient tunnel (TGT) constructed in filed condition. The ambient and TGT temperature varied from 31.84 °C_(max) to 20.56 °C_(min) and 41.91 °C_(max) to 22.37 °C_(min), respectively, during study period. The scanning electron and light microscopic study showed extreme morphological abnormalities viz. shape and size in pollen grains of rice exposed to elevated temperature as compared to ambient. These abnormalities induced by elevated temperature may drastically decline grain filling potential which ultimately reduces grain yield in future climate change. This study will enlighten rice researchers for further screening of rice genotypes thermotolerant to foothills of Himalayan agro-ecosystem.

Aerosol optical properties and radiative effects over Manora Peak in the Himalayan foothills: seasonal variability and role of transported aerosols

The higher altitude regions of Himalayas and Tibetan Plateau are influenced by the dust and black carbon (BC) aerosols from the emissions and long-range transport from the adjoining areas. In this study, we present impacts of advection of polluted air masses of natural and anthropogenic emissions, on aerosol optical and radiative properties at Manora Peak (~2000 m amsl) in central Himalaya over a period of more than two years (February 2006-May 2008). We used the most updated and comprehensive data of chemical and optical properties available in one of the most climatically sensitive region, the Himalaya, to estimate atmospheric radiative forcing and heating rate. Aerosol optical depth (AOD) was found to vary from 0.04 to 0.45 with significantly higher values in summer mainly due to an increase in mineral dust and biomass burning aerosols due to transport. In contrast, single scattering albedo (SSA) varied from 0.74 to 0.88 with relatively lower values during summer, suggesting an increase in absorbing BC and mineral dust aerosols. As a result, a large positive atmospheric radiative forcing (about 28 ± 5 Wm(-2)) and high values of corresponding heating rate (0.80 ± 0.14 Kday(-1)) has been found during summer. During the entire observation period, radiative forcing at the top of the atmosphere varied from -2 to +14 Wm(-2) and from -3 to -50 Wm(-2) at the surface whereas atmospheric forcing was in the range of 3 to 65 Wm(-2) resulting in a heating rate of 0.1-1.8 Kday(-1).