Floristic structure and root dynamics in slope stabilization of landslide-prone areas in the Phewa watershed, Nepal

The Phewa watershed is under constant landslide threat because of its complicated topography, climate, and biology. The floral structure of landslide-prone areas possesses a significant impact on determining the ecological processes involved in slope stabilization. Plant roots, for example, serve as physical anchors in the soil, enhancing slope stability. Therefore, this study aims to determine appropriate plant species that can enhance soil stability in Phewa Watershed by examining their floral structure in landslide areas. Floral diversity was assessed throughout field visits. Ten of the 46 landslides were selected with 15 plots based on aspect, watershed zones, and normalized difference vegetation index (NDVI) value. Six plant species were selected to evaluate root traits, uprooting force, and cellulosic testing based on their Important Value Index (IVI) value, native characteristics, and regeneration. The uprooting force was calculated using a 'winch' with a force transducer, while the root characteristics were measured manually and using 'ImageJ software'. Results show that 319 species from 92 families are registered in the buffer zones and landslide scars, and the NDVI suggest that vegetation covers more than 49% of the landslide areas. The floral composition of the landslides in the 15 plots contains 140 species from 52 families, with Poaceae dominating. In six plant species, the Ochiai index suggests a significant level of association. The uprooting force is correlated to the root diameter and number but is insignificant in terms of root length and area. Saccharum spontaneum is the best option for landslide stability based on uprooting force (882.63±245.175) N, cellulose content (67.038±4.766) % and root number characteristic (69.333±24.338) whereas Themeda arundinacea is preferred due to its root diameter traits (0.054±0.022) cm. Finally, it emphasizes the significance of selecting key species in lowering the risk of landslides, strengthening soil stability, and building resilient ecosystems in susceptible watershed areas.