Kedar Rijal’s research while affiliated with Tribhuvan University and other places

Forest fire frequency in Nepal has increased in recent years. Field-level assessments of fire impacts on plant community assemblage and postfire recovery dynamics across different ecological zones are limited in Nepal, creating a research gap in understanding the ecological processes affected due to wildfires. This study investigates the impacts of forest fire on woody species composition, diversity and regeneration potential in forest stands of central Himalaya, Nepal. Field assessments were carried out in Terai (Nawalpur), Mid-hill (Lamjung) and Mountain (Manang) ecological zones. Trees were sampled in 20 m × 20 m plots, whereas saplings and seedlings were sampled in two nested sub-plots of dimensions 5 m × 5 m and 1 m × 1 m, respectively. A total of 183 plots were laid for sampling trees, of which 89 plots were in the non-fire stands (no fire event in the past 15 years) and 94 plots in the fire stands (at least one fire event in the past 3 years). Similarly, each 183 sub-plots were used for saplings and seedlings assessment. We observed variability in the results caused by fire in the tree stratum. Considering the sapling and seedling layers, significantly higher densities were observed in the non-fire stands of Terai, Mid-hill and Mountain compared to the fire stands, except for the seedling density in Terai. Permutational MANOVA showed a difference in the woody plant species composition between the fire and non-fire stands, except the sapling and seedling composition in the fire and non-fire stands of Terai. We observed a higher diversity of trees in the non-fire sites of Terai compared to the fire sites. However, in Mid-hill and Mountain, significant differences were not observed for the tree species diversity. Woody species sapling diversity in non-fire sites was higher compared to fire sites across the studied ecological zones. Similarly, woody plant seedling diversity showed that non-fire sites of Mid-hill and Mountain have higher diversity compared to the fire sites, but not observed in Terai sites. This study highlights the importance of fire control in shaping plant community assemblage and recovery. Understanding the species-specific impact of forest fires and regional differences in such impacts is essential for developing successful fire management strategies.

Forest fire produces varying ecological effects determining vegetation patterns in ecosystems. Plant community assemblages in forests are altered by fire influencing growth and development. Some plant communities are suppressed and some are encouraged to develop due to fire. Little empirical evidence exists revealing the condition of fire-mediated loss of small-sized individuals, and response of fire to demographic structure of woody plant species in Nepal. The aim of this research, therefore, is to quantify fire-mediated biomass loss of small-sized individuals of woody species (seedlings), and investigate the associated impacts on the demographic structure of plants in the Terai forests of central Nepal. Impacts on small-sized individuals of woody plant species were evaluated based on evidence from 25 sites with 50, 1 m × 1 m subplots for seedlings nested in 10 m × 10 m plots (n = 50) for saplings and adults. Of the 50 sampling plots, 25 represented fire-affected and the remaining 25 represented control plots. Mean density of resprouting and newly grown seedlings developed in one year after the surface fire was 46,800 ± 4071 inds. ha−1. Shorea robusta Gaertn. was the most abundant species regenerated with seedlings in the control forest sites. The estimated average yearly loss of above ground biomass (AGB) for woody plant seedlings in the forest due to surface fire was 1,651.5 ± 360.2 kg ha−1. Of the total fire-affected AGB of S. robusta, 700.0 kg ha−1 was the immediate burnt loss and 322.5 kg ha−1 was dead AGB left unburnt. Similarly, among the other most abundant species, higher proportion of immediate fresh AGB loss was observed for Mallotus philippensis (Lam.) Müll.-Arg. and Casearia graveolens Dalzell. compared to dead AGB left unburnt. The Weibull probability density function shows the existence of saplings recruitment bottleneck in the fire-prone forest sites, i.e., growth of seedlings to saplings was restricted. Surface fire impacted the development of DBH class > 0–5 cm saplings. Surface fires are one of the potential environmental filters of the plant species regeneration and composition in the forests of lowland Terai Nepal. These demographic variations and bottlenecks should be considered while formulating management actions to conserve vegetation assemblages in fire-mediated ecosystems.

The COVID-19 pandemic caused a setback for Nepal, leading to nationwide lockdowns. The study analyzed the impact of lockdown on air quality during the first and second waves of the COVID-19 pandemic in the Kathmandu Valley. We analyzed 5 years of ground-based air quality monitoring data (2017–2021) from March to July and April to June for the first and second wave lockdowns, respectively. A significant decrease in PM2.5 (particulate matter with an aerodynamic diameter ≤ 2.5 μm) concentrations was observed during the lockdowns. The highest rate of decline in PM2.5 levels was observed during May and July compared to the pre-pandemic year. The PM2.5 concentration during the lockdown period remained within the WHO guideline limit and NAAQS for the maximum number of days compared to the lockdown window in the pre-pandemic years (2017–2019). Likewise, lower PM2.5 levels were observed during the second wave lockdown, which was characterized by a targeted lockdown approach (smart lockdown). We found a significant correlation of PM2.5 concentration with community mobility changes (i.e., walking, driving, and using public transport) from the Spearman correlation analysis. Lockdown measures restricted human mobility that led to a lowering of PM2.5 concentrations. Our findings can be helpful in developing urban air quality control measures and management strategies, especially during high pollution episodes.

Various forest management strategies are in place for the conservation of forest ecosystems across the globe. Nepal is also implementing different forest management and restoration practices and has various impacts on vegetation characteristics. This study aims to compare the richness and diversity of woody plant species, and variability in abundance of woody species assemblages in different forest management stands, viz. restored stands inside Buffer Zone Community Forest (BZCF), natural stands of BZCF and core stands of Parsa National Park. Thirty sampling plots of 30 m × 30 m were laid on each stand, maintaining at least 50 m distance between the plots, where woody plant species having height 1.5 cm was identified and their DBH measured. Species composition was assessed comparing Importance Value Index (IVI) of woody plant species across the forests. Similarly, species diversity and structural diversity across stands were determined using Shannon Diversity index and basal areas of the plant species were calculated. The study showed Shorea robusta and Lagerstroemia parviflora with highest frequency (>80%) in all the sites, and the species diversity was highest in the core stands inside the national park followed by the natural stands of BZCF, and the restored stands of BZCF. Basal area of overall species and density of S. robusta were, however, highest on the restored stands of BZCF, whereas overall density was highest in the natural stands of the BZCF. The study revealed that the forest management practices need improvement in enhancing the plant species diversity of the ecosystems. We recommend to assess the functional attributes of the different forest management stands to evaluate the effectiveness of forest management strategies.

Methane (CH4) emission in livestock arises from enteric fermentation (EnF) and manure management (MM). This study develops the country-specific CH4 emission factors (EFs) in both EnF and MM for domestic water buffalo (Bubalus bubalis) and estimates total CH4 emission in Nepal using Intergovernmental Panel on Climate Change (IPCC) Tier 2 methodology. Seasonal field data were collected on morphological characteristics, feed characteristics, and manure management practices of the buffalo. The buffalo population was divided into five age groups, and at least 35 buffalo individuals were measured from each age group in the Hilly and Plain regions of Nepal in the winter and summer seasons. Buffalo adult male (BAM) had the highest body weight of 530 ± 53 kg in the plain region and 514 ± 65 kg in the Hill region. Similarly, the weight of buffalo calf (BC) was 91 ± 25 kg in the plain region and 77 ± 26 kg in the Hill region. For different age groups of buffalo, EnF EFs ranged from 34 ± 8 to 90 ± 10 kg CH4 head⁻¹ year⁻¹ and MM EFs ranged from 2.5 ± 0.5 to 7.5 ± 0.5 kg CH4 head⁻¹ year⁻¹. The estimated EnF and MM EFs of buffalo were not statistically different by region (p > 0 .05). The total CH4 flux from buffalo was 347.8 Gg year⁻¹ in Nepal, contributing 322.2 Gg year⁻¹ from EnF and 25.6 Gg year⁻¹ from MM. The country-specific EFs are highly recommended for precise computing of the national emissions and carrying out mitigation action. Graphical Abstract

One of the prominent impacts of climate change induced glacier retreat in the Himalayas is the formation and expansion of glacial lakes. The newly formed glacial lakes are mostly located in higher altitudinal regions (4200-5800 m) of Himalaya, however, a new glacial lake (Kapuche, 28.446° N and 84.116° E) have been reported to be emerged in the relatively low elevation area of ∼2450 m above sea level (masl) in the Nepal Himalaya. This short communication presents the remote sensing-based evolution and field-based bathymetry of Kapuche lake, and further discusses its formation process and lake type for being a glacial lake at the lowest elevation in Nepal Himalaya.

In Nepal, a South Asian country located in the central Himalayan region, a countrywide lockdown was imposed from 24 March to 20 July 2020 to contain the spread of the SARS-CoV-2 virus during the first wave of the novel coronavirus disease (COVID-19) pandemic. This study used the rare incidence of countrywide lockdown to investigate the air quality change in Nepal and its topographically unique urban center, the Kathmandu Valley, during the lockdown period, segregated by dry (pre-monsoon) and wet (monsoon) seasons, based on satellite remote sensing and ground-based air quality monitoring data. Our analysis showed a remarkable improvement in air quality during the lockdown in the dry season over the country. The mean aerosol optical depth (AOD), nitrogen dioxide (NO2), and carbon monoxide (CO) levels over the entire country decreased by 27.7%, 12.7%, and 5.12%, respectively, compared to the pre-pandemic levels. Likewise, in the Kathmandu Valley, PM2.5 (particulate matter with diameter ≤ 2.5 μm), AOD, NO2, and CO levels decreased by 38.1%, 38.0%, 16.5%, and 6.03%, respectively, during the dry season segment of the lockdown. It is worth noting that the change in AOD and NO2 levels was notably higher in the Kathmandu Valley than in the entire country. However, during the wet season segment of the lockdown, relatively subtle changes in AOD (-7.41%), NO2 (-6.87%), and CO (-2.80%) levels were observed over the country. Since the lockdown restricted people's mobility and operation of many industries, it might have reduced emissions from transport and industrial sectors. Therefore, our findings provide insights into the potential improvement in air quality that could be achieved by controlling emissions from those sectors and can be useful in formulating urban air quality management strategies.

The chemical characterization and assessment of the water quality in the headwater areas of the Himalaya are necessary for securing the water in the future. This study aims to assess the hydrochemistry and water quality concerning drinking and irrigational uses in the Seti River Basin (SRB), Nepal. A total of 45 water samples were collected in 2016 from the SRB during pre-monsoon, monsoon, and post-monsoon seasons, and pH, EC, TDS, and DO were measured on-site, whereas Ca2+, Mg2+, K+, Na+, Cl˗, SO42˗, NO3˗, and dissolved Si were analyzed in the laboratory. The results revealed mildly alkaline pH (8.40 ± 0.43) with the pattern of average ionic dominancy: Ca2+ > Mg2+ > Na+ > K+ and HCO3− > SO42− > Cl˗ > NO3˗ for cations and anions, respectively. Gibbs diagram implied that the lithogenic weathering mainly controlled the solute acquisition process, which was further confirmed by the Piper diagram, exhibiting Ca–HCO3 as the governing hydrochemical facies (91%). The average molar ratios were 0.88, 8.33, and 6.86 of (Ca2+ + Mg2+)/TZ+, (Ca2+ + Mg2+)/(Na+ + K+), and HCO3−/(Na+ + K+), respectively, which specified that the carbonate weathering largely controlled the solute acquisition processes with a minor contribution of silicates. The mass budget calculation also confirmed the dominance of carbonate weathering (72.0%, 78.9%, and 62.0% in Pre-Monsoon, Monsoon, and Post-Monsoon, respectively) and the high monsoon rainfall’s dilution effect to anthropogenic input of cations. Principal component analysis and correlation matrix exhibited that the major sources of ions in the basin were geogenic with minor anthropic signatures. Furthermore, water quality in connection to drinking and irrigation uses revealed that the basin has mostly retained its natural water quality. This investigation suggests that regular monitoring and assessment are essential for maintaining the water quality and ecological integrity in the Himalayan river basins.

The fish sanctuary delineation protocol encloses background information on Nepal's aquatic biodiversity conservation, the status of aquatic biodiversity, and existing institutional arrangements in conservation. Introduction of the fish sanctuary, benefits and pitfalls, the process for fish sanctuary declaration, fish sanctuary approval, and management/governance structure are explained briefly in the protocol. Nature (biodiversity value, topography, ecology, and land use), wealth (infrastructure and livelihoods), and power (local institutions, ethnicity, social inclusion, and governance) are the primary fish sanctuary delineating factors, which are also used by the Paani program for prioritizing the watersheds. This report is an entry point of the fish sanctuary establishments and a guideline for identifying the river stretches potential for fish sanctuary declaration in Nepal.