Gall inducers are widely used as biocontrol agents to suppress the vegetative and reproductive growth of invasive weeds. Procecidochares utilis Stone (Diptera: Tephritidae) is a gall forming fly that was released as a biocontrol agent against the noxious invasive weed Ageratina adenophora (Sprengel) R. King and H. Robinson (Asterales: Asteraceae). However, the effectiveness of P. utilis in controlling A. adenophora has been reported to vary according to geographic regions, with very low effectiveness in the Himalaya. In this study, we measured the abundance of P. utilis stem galling on A. adenophora along the elevation gradient (240–2965 m asl) in central Nepal. We found that elevation had a significant effect on gall abundance as well as gall size. Gall abundance and size peaked at mid-elevation (1940–2000 m asl). Stem galling by the fly reduced the stem diameter of the weed and all the three nutrients (N, P and K) in galls were significantly higher than in ungalled stems. Our study indicates that elevation is an important abiotic factor that strongly influences the P. utilis stem gall abundance, as well as gall size, and galls formed by P. utilis act as nutrient sinks. These findings provide insights in insect gall ecology, which may help the successful biocontrol of A. adenophora.

Although the effects of invasive alien plants on natural ecosystems are well known, the effects of specific plant species can vary across habitat types and disturbance intensity. This study was carried out to analyze the effects of Lantana camara on associated vegetation and soil physico-chemical properties at invaded and non-invaded sites across three different habitat types (forest edge, fallow land, and roadside) in central Nepal. We sampled 50 pairs of 5 m × 5 m (for shrub species) and 1 m × 1 m (for herbs species) plots at invaded and non-invaded sites in each habitat and recorded community variables for each species within the sampling plots for both wet (monsoon) and dry (pre-monsoon) seasons. Further, we collected soil samples from each quadrat and determined the soil physico-chemical properties. We recorded 137 species of flowering plants (119 from non-invaded and 97 from invaded plots) and classified them in accordance with life form/habit. In invaded sites, we found a significant decline in species diversity as indicated by the Simpson and Shannon diversity indices. Specifically, L. camara reduced the species richness, Simpson index, and Shannon diversity index by 36.84%, 11.84%, and 40.21%, respectively. Soil nutrients such as total nitrogen, soil organic carbon, and available phosphorus were significantly higher in invaded sites than non-invaded ones except for available potassium and soil pH. This study provided evidence that Lantana L. camara has a substantial impact on the understory plant community assemblage and the physico-chemical properties of soil. The results suggest that the protection of native plant community requires management of L. camara by implementing appropriate measures.

Insect pollinators are important means for a stable ecosystem. The habitat types play a crucial role in the community composition, abundance, diversity, and species richness of the pollinators. The present study in Shivapuri‐Nagarjun National Park explored the species richness and abundances of insect pollinators in four different habitats and different environmental variables in determining the community composition of the pollinators. Data were collected from 1,500 m to 2,700 m using color pan traps and hand sweeping methods. Non‐Metric Multidimensional Scaling (NMDS) and Redundancy Analysis (RDA) were conducted to show the association between insect pollinators and environmental variables. The results firmly demonstrated that species richness and abundances were higher (158) in Open trail compared to other habitats. The distribution of the pollinator species was more uniform in the Open trail followed by the Grassland. Similarly, a strong positive correlation between flower resources and pollinators' abundance (R² = .63, P < .001) was found. In conclusion, the Open trail harbors rich insect pollinators in lower elevation. The community structure of the pollinators was strongly influenced by the presence of flowers in the trails.

The forest carbon stock usually depends on the forest types, forest density, age of forest, size of trees, site quality, wood density, annual precipitation, and species composition. This research aims to analyze the relationship among tree carbon stock, species richness, soil chemical properties such as soil organic carbon, and soil pH in the Forests of Chandragiri Hills, Kathmandu, Central Nepal. Along this forest, five square plots (20 × 20 m2 ) each were established along the two transects at a maximum interval of 100 m. Carbon stock of each tree was estimated by using allometric equation based on measured tree height and DBH. The mean tree carbon stock was found to be highest in Mixed Forest (87.13 t/ha) followed by Oak Forest (52.75 t/ha), and Pine Forest (22.5 t/ha). The tree carbon stock showed significant negative correlation with tree species richness (r = -0.56, p = 0.001). The tree carbon stock showed significant positive correlation with soil organic carbon (r = 0.57, p = 0.001) and soil pH (r = 0.37, p = 0.05). Tree carbon was found positively highly significant correlation with altitude, Soil organic carbon, pH, and Shannon diversity index.