The agroforestry and intercropping systems are recognized as important options for greenhouse gas mitigation. The primary objective of this study was to assess the impacts of land use change from Orange (O) monoculture to Coffee-Orange (CO) intercropping and Coffee-Forest (CF) agroforest systems, implemented 20 years ago, on soil properties at three different soil depth layers (0–10 cm, 10–20 cm, 20–30 cm), with a particular focus on microbial biomass carbon (MBC) and soil organic carbon (SOC) levels. Although there were no changes in most of the soil’s physical properties, the soil’s chemical properties varied significantly across different land use types. SOC was higher in CF and CO systems compared to the O system; however, only in the CO system was the SOC incorporated evenly across all depths. Regression analysis showed that, in the CO system, microbial biomass carbon increased significantly, suggesting that these systems are more promising for carbon sequestration. The low pH and phosphorus values in the agroforest system were identified as limiting factors for microbial biomass enhancement. Importantly, the integration of coffee into orange cultivation not only enhances economic benefits but also contributes to long-term carbon sequestration by increasing SOC in deeper soil layers.

Drought-resilient varieties are of great significance in the context of climate change and the increasing frequency of droughts. This study evaluated the drought tolerance in twelve rice landraces from three distinct agro-climatic zones (Tarai, Inner-Tarai, and Mid-Hill) in Far-west Nepal. The landraces were subjected to control, intermittent drought, and complete drought treatments to assess their yield and drought tolerance indices. The yield reductions were observed across all varieties. Based on the generalized linear model (GLM), varieties like Chamade, Ratomarso, Jhumke from Mid-Hill, Jhini, Shanti from Inner-Tarai, Lalchand and Anjana varieties from Tarai have significantly higher yield loss. Varieties like Temase, Chiudi, Batebudo, Sauthyari and Ghiupuri have less yield reduction than the baseline mean of the studied system i.e., 15.9%. Drought tolerance indices effectively differentiated landrace responses. Ghiupuri, Lalchand, and Sauthyari exhibited superior tolerance based on consistently higher index values. Principal component analysis and cluster analysis revealed distinct patterns of response among landraces, highlighting the importance of considering multiple traits and employing multivariate methods for comprehensive drought tolerance evaluation and selection of resilient varieties for water-scarce environments. By identifying drought-tolerant landraces, this research supports sustainable agriculture and food security, aligning with Sustainable Development Goals 2 (Zero Hunger), 13 (Climate Action), and 15 (Life on Land) by promoting climate-resilient crop production and biodiversity conservation.

Assessments of soil physicochemical and microbial properties represent an approach to identify the soil status of agroecosystem through which sustainable soil management can be achieved. This study aimed to characterize the soil physicochemical properties and soil microbial biomass carbon at three soil depths (0–10 cm, 10–20 cm, and 20–30 cm) of an irrigated agroecosystem in the mid-hill region of Nepal. The results revealed that the topsoil (0–10 cm) exhibited the highest levels of temperature (21.7 ± 0.4 °C), electrical conductivity (106.8 ± 5.1 µS/cm), and moisture content (29.8 ± 5.4%), with a gradual decrease in these properties at deeper layers. The range of soil organic carbon (SOC) and organic matter (OM) contents ranged from 2.0 to 0.9% and 3.4 to 1.5%, respectively, with the highest concentrations observed in the surface layer (SOC: 2.0 ± 0.3%; OM: 3.4 ± 0.5%). Both parameters declined significantly with depth, indicating a moderate level of SOC and OM in the topsoil and markedly lower levels in deeper layers. Similarly, total nitrogen (TN), available phosphorus (AP), and available potassium (AK) also declined with soil depth, suggesting lower nutrient levels in deeper layers. Microbial biomass carbon (MBC), a key indicator of soil biological activity, decreased sharply from 527.8 ± 142.2 mg kg^− 1 in the topsoil to 110.1 ± 42.6 mg kg^− 1 at 20–30 cm soil depth. The ratios of SOC and TN, as well as SOC and MBC, were also higher in the top soil layer and decreased with depth. Correlation analysis revealed significant positive relationships among SOC, OM, TN, AP, MBC, and moisture content, indicating their collective role in maintaining soil health. Principal Component Analysis (PCA) further confirmed that the topsoil and deeper layers were distinctly differentiated by nutrient and organic matter content, with the mid-layer (10–20 cm) showing intermediate characteristics. The findings indicate that the topsoil in this paddy field has higher fertility, while the deeper layers show nutrient depletion and reduced microbial activity. This pattern highlights the urgent need for targeted soil management strategies to maintain soil fertility throughout the entire soil profile.

Soil respiration, the carbon dioxide emitted by the biological activity of soil, is one of the primary ways of carbon release from forest ecosystems. Soil respiration can be partitioned into its two components: autotrophic respiration by roots (RA) and heterotrophic respiration by soil microorganisms (RH). This study aims to assess the seasonal fluctuations of RA and RH in the subtropical forest of Nepal dominated by Schima wallichii and Castanopsis indica. The trenching method (root exclusion method) was applied to partition RA and RH. The closed chamber method was applied to measure soil carbon emission. A Portable Infra-Red Gas Analyzer (IRGA) was used to measure CO2 concentration in control and trenched chambers every month for one-year period. Soil temperature and soil water content were measured to analyze the effect of these environmental variables on soil respiration rate. The results revealed that the mean RA and RH were 116.1±10.61 and 130±6.9 mg CO2m-2h-1, respectively, with higher contribution (52%) of RH to total soil respiration. Significant seasonal variation with summer peak was remarkable in both components of soil respiration. RA and RH showed significant exponential relationships with soil temperature and soil water content. Soil temperature had a greater influence on RH than RA. Correspondingly, the temperature sensitivity of soil respiration (Q10) values of RA and RH were 3.218 and 2.083, respectively. This suggests that the soil CO2 emissions in these subtropical forests may increase with future climate warming with more temperature sensitivity of autotrophic respiration.

Mycorrhizal symbiosis in rice enhances drought adaptation but there are limited studies regarding the frequency and amplitude of mycorrhizae colonization in traditional landraces. This study investigates mycorrhizal colonization frequency (FMS) and intensity (IRS) in 12 rice landraces across three agroecological zones (Tarai, Inner-Tarai, Mid-hill) of Far-West Nepal under drought stress. Field experiments exposed landraces to control, intermittent, and complete drought treatments, with soil properties and root colonization analyzed. Results revealed FMS and IRS variations driven by soil composition and genotype. Mid-hill soils (acidic, high organic matter) showed lower FMS but elevated IRS under drought, while neutral pH in Tarai and silt/clay-rich soils supported higher FMS. Sandy soil in Inner-Tarai also promoted FMS. Drought significantly increased IRS, particularly in Anjana and Sauthiyari (Tarai), Chiudi and Shanti (Inner-Tarai), and Chamade and Jhumke (Mid-hill), which exhibited IRS surges of 171–388%. These landraces demonstrated symbiotic resilience, linking mycorrhizal networks to enhanced nutrient/water uptake. Soil organic matter and nutrient levels amplified IRS responses, underscoring fertility’s role in adaptation. FMS ranged from 50 to 100%, and IRS 1.20–19.74%, with intensity being a stronger drought-tolerance indicator than frequency. The study highlights the conservation urgency for these landraces, as traditional varieties decline due to hybrid adoption. Their drought-inducible mycorrhizal symbiosis offers a sustainable strategy for climate-resilient rice production, emphasizing soil–genotype interactions in agroecological adaptation.

The amount of carbon stored in forests depends on their age, species composition, and geographical locations. This study analyzed the tree species composition and carbon stock in three different forests in different elevation zones of Phulchoki Hill, Nepal. Tree species composition was assessed by quadrat sampling in the forests and carbon stock was determined by using allometric equation. Twenty-three tree species were found in the forests with high tree density and richness in Schima-Castanopsis Forest of Lower zone (1400-1800m). Above-ground tree carbon stock differed significantly among the forest types, ranging from 74.8 t/ha (lower zone) to 404.3 t/ha (upper zone). Tree basal area and biomass carbon stock increased with elevation and Quercus semecarpifolia contributed maximally (94%) to total carbon density at upper elevation zone. Hence, evergreen oak forests at higher elevations contribute to reduce and mitigate climate change by storing significant amount of carbon. Bangladesh J. Bot. 54(2): 177-183, 2025 (June)