Microbial mechanisms regulate soil organic carbon mineralization under carbon with varying levels of nitrogen addition in the above-treeline ecosystem.

Climate change is leading to the upward migration of treelines in mountainous regions, resulting in changes to the carbon and nitrogen inputs in soils. The impact of these alterations on the microbial mineralization of the existing soil organic carbon (SOC) pool remains uncertain, making it challenging to anticipate their effects on the carbon balance. To enhance our prediction and understanding of native SOC mineralization in Himalayan regions resulting from treeline shifts, a study was conducted to quantify soil priming effects (PEs) at high elevations above the treeline ecosystem. In laboratory incubation, soils were treated with a combination of 13C-glucose and varying nitrogen rates, along with carbon-only treatments and control groups without any amendments. The addition of carbon with varying nitrogen addition rates exhibited diverse PEs on native SOC. A highly positive PE was observed under low nitrogen input due to a high carbon/nitrogen imbalance and increased L-leucine aminopeptidase (LAP) activity, coupled with low nitrogen availability and carbon use efficiency (CUE). In contrast, a positive PE declined following high nitrogen input due to a low carbon/nitrogen imbalance and LAP activity, coupled with high nitrogen availability and CUE. These findings support the concept that multiple mechanisms (i.e., microbial nitrogen mining and microbial metabolic efficiency) exist that regulate SOC mineralization under the addition of carbon with varying nitrogen rates. Thus, an increase in nitrogen availability fulfils microbial nitrogen demand, reduces the microbial carbon/nitrogen imbalance, decreases enzyme activity that requires nitrogen and enhances microbial metabolic efficiency. Consequently, this mechanism reduces the positive PE, thereby serving as a potential tool for stabilizing native SOC in above-treeline ecosystems.

Habitat suitability of four threatened Himalayan species: Asiatic black bear, common leopard, musk deer, and snow leopard.

Background: Biodiversity conservation is becoming challenging day by day. For this, it is essential to understand the distribution, habitat, and impact of anthropogenic activities on animals at risk. We assessed the suitable habitats and anthropogenic impacts on Asiatic black bears, common leopards, musk deer, and snow leopards in and outside the protected areas of Gandaki Province, Nepal. Methods: We collected the presence locations of Asiatic black bears, common leopards, musk deer, and snow leopards based on scats and other signs. We employed the Maximum Entropy (MaxEnt) tool to identify suitable habitats of our studied species and their anthropogenic impacts on them. Results: The total suitable habitat of the common leopard was found to be 6,052 km2, followed by the Asiatic black bear (5,819 km2), snow leopard (4,447 km2), and musk deer (1,690 km2) in Gandaki Province. Most of the areas of suitable habitat for common leopards and Asiatic black bears were outside the protected areas, and for musk deer and snow leopards were inside the protected areas. Elevation was the most important variable determining habitat suitability of Asiatic black bear, common leopard, and musk deer, whereas the distance to water was the most important variable determining habitat suitability of snow leopard. Asiatic black bears, common leopards, and musk deer face significant anthropogenic impacts, but snow leopards face some anthropogenic impacts. Conclusion: Managing these animals' habitats inside and outside protected areas is essential. Hence, biodiversity conservation and livelihood opportunities should be balanced in the Himalayas on a win-win basis.

Suitable habitat of wild Asian elephant in Western Terai of Nepal.

BACKGROUND: There is currently very little available research on the habitat suitability, the influence of infrastructure on distribution, and the extent and connectivity of habitat available to the wild Asian elephant (Elephas maximus). Information related to the habitat is crucial for conservation of this species. METHODS: In this study, we identified suitable habitat for wild Asian elephants in the Western Terai region of Nepal using Maximum Entropy (MaxEnt) software. RESULTS: Of 9,207 km2, we identified 3194.82 km2 as suitable habitat for wild Asian elephants in the study area. Approximately 40% of identified habitat occurs in existing protected areas. Most of these habitat patches are smaller than previous estimations of the species home range, and this may reduce the probability of the species continued survival in the study area. Proximity to roads was identified as the most important factor defining habitat suitability, with elephants preferring habitats far from roads. CONCLUSIONS: We conclude that further habitat fragmentation in the study area can be reduced by avoiding the construction of new roads and connectivity between areas of existing suitable habitat can be increased through the identification and management of wildlife corridors between habitat patches.