Effect of elevation on soil quality under bamboo (Bambusa nutans subsp. cupulata) stands outside forest area in Eastern Nepal

Globally, bamboo covers 37 million hectares (about 1% of the world’s forests), with over 50% growing outside official forests on degraded, marginal, and agricultural lands. However, little research has explored the relationship between soil properties and bamboo in these non-forest areas, as most studies focus on bamboo forest. Using stratified random sampling, this study assessed soil quality under bamboo stands outside forests in the Udayapur district of Nepal across three elevation zones: lower (0-400 m), middle (400–800 m), and higher (800–1200 m). A total of thirty 100 m² circular plots (10 in each zone) were sampled at two soil depths; the surface layer (0–15 cm) and the subsurface layer (15–30 cm) to assess soil quality using different soil quality indicators. At the 0–15 cm depth, soil organic carbon, total nitrogen, and available potassium were significantly higher at middle elevation (p < 0.05). Available phosphorus and soil pH were significantly higher at middle elevation, while available potassium was significantly higher at higher elevation at 15–30 cm depth (p < 0.05). SQI was higher at the 0-15cm depth (0.53) compared to the 0–30 cm depth (0.49), though this difference was not statistically significant (p > 0.05). Elevation had a significant effect (p < 0.05) on SQI only at the 0–15 cm depth. This study observed significantly higher SQI at middle elevation (0.57) whereas lower SQI at lower elevation (0.48). Further studies with larger samples and broader geographic coverage, incorporating additional soil indicators and environmental variables, could more effectively inform sustainable land management and local livelihood improvements in bamboo stands outside forest areas.