This study was undertaken with the objective of evaluating the tree structure and biodiversity within community forests, as well as analyzing the spatial distribution of local disturbances. To achieve this, three community forests – Banelpokhari, Okhardhara, and Suntalidada – located in Godawari Municipality, Nepal, were selected as the research sites. The research utilized a systematic random sampling approach, resulting in the establishment of a total of 90 sample plots across the three community forests. These sample plots encompassed circular areas of 500 m2 for trees, 100 m2 for poles, and 25 m2 for saplings, wherein the diameter and height of plants at different growth stages were measured. Additionally, smaller 10 m2 sample plots were designated for seedling counts. The forest disturbances were identified by closely observing the study site and encompassed factors such as road development, transmission lines, soil erosion, encroachment, disease, weeds, recreation, and illegal logging. Satellite images from Sentinel 2A for the years 2017 and 2022 were obtained and utilized. Biodiversity indices were computed, including the Importance Value Index (IVI). Normalized Difference Vegetation Indices were derived from the imagery and subsequently used for classification mapping.
The findings of the study revealed that Pinus roxburghii was the most prevalent species across all three community forests. In particular, Okhardhara CF exhibited the highest IVI for Pinus roxburghii, measuring at 281.25. When considering the Shannon-Weiner Diversity Index (H’), Suntalidada CF exhibited the highest diversity with a value of 3.52, followed by Okhardhara CF at 3.22, and Banelpokhari CF with the lowest diversity at 1.95. Furthermore, Suntalidada CF displayed the highest levels of evenness (0.96) and species richness (25). Concerning tree structure, a higher density was observed within the diameter class of 0–10 cm and the height class of 0–5 m. In contrast, the lowest densities were found in the diameter class exceeding 40 cm and height class surpassing 20.1 m. Throughout all three community forests, common factors influencing forest structure and biodiversity included road development, transmission lines, soil erosion, encroachment, disease, weeds, recreation, and illegal logging. The dense forest area in Banelpokhari CF, Okhardhara CF, and Suntalidada CF was measured at 71.92 ha, 72.20 ha, and 104.69 ha, respectively, during 2017. However, by 2022, these areas had transformed into sparse forests, measuring 65.63 ha, 56.83 ha, and 92.34 ha, respectively. This indicates a reduction rate of approximately 9%, 19%, and 11% for the three community forests over the five-year period.