Analyzing the Relationship, Distribution of Tree Species Diversity, and Above-Ground Biomass on the Chitwan-Annapurna Landscape in Nepal

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Forests provide numerous ecosystem goods and services. Their roles are considered as important for both climate mitigation and adaptation program. In Nepal, there are significant forest resources which are distributed in different regions; however, the studies on the spatial tree species distribution and the above-ground biomass and their relationship at the landscape level have not been well studied. This study aims to analyze the relationship, distribution of tree species diversity, and above-ground biomass at a landscape level. The data used for this study were obtained from the Forest Research and Training Center of Nepal, International Centre for Integrated Mountain Development (ICIMOD), and Worldwide Wildlife Fund (WWF-Nepal). The landscape has a mean of 191.89 tons ha−1 of the above-ground biomass. The highest amount of the above-ground biomass measured was 650 tons ha−1 with 96 individual trees, and the least was 3.428 tons ha−1. The measured mean height of the tree was 11.77 m, and diameter at breast height (DBH) was 18.59 cm. In the case of the spatial distribution of the above-ground biomass, plots distributed at the middle altitude range greater than 900 meters above sea level (m. a. s. l) to 3000 meters above sea level taking more amount of the above-ground biomass (AGB). Similarly, the highest plot-level Shannon diversity index (H’) was 2.75 with an average of 0.96 at the middle altitude region followed by the lower region with an average of 0.89 and least 0.87 at a higher elevation. Above-ground biomass (R2 = 0.48) and tree height (R2 = 0.506) significantly increased with increasing elevation up to a certain level increased of elevation. Diameter at breast height (DBH) showed significance (R2 = 0.364) but small increase with increasing elevation, while the relationship among tree species diversity index, above-ground biomass, and elevation showed a weak and very weak positive relationship with R2 = 0.018 and R2 = 0.002, respectively. Based on the overall results, it is concluded that elevation has some level of influence on the forest tree diversity and above-ground biomass. The finding of this study could be useful for landscape-level resource management and planning under various changes.