Vegetation morphology and soil features along unstable road slope: A case study from Mugling Narayanghat road Section, Central Nepal

Abstract

In mountain parts of Nepal, road network passes through the geologically young and unstable parts of the landscapes. Every year most of the road sections are blocked by landslide and debris deposition. In this study, one such unstable road called Mugling-Narayanghat road, located at central part of Nepal is selected to understand its erosion state, vegetation morphology, and soil characteristics. For this, four sampling sites are selected by random methods at the accessible sites, representing from different geological units and terrain conditions. This study mainly describes about 1) types of geology distributed along road section, 2) major vegetation types and morphological features of herbaceous plants, and 3) physical characteristics of the soil that are linked with vegetation growth. The studied road section passes by cut slopes of Mahabharat range of rolling and hilly terrain and characterizes with sharp bends and curved alignment along the bank of the Trishuli River. The area receives average annual rainfall of about 2400 mm. Highly weathered phyllite, metasandstone, quartzite, are major geological types along the road section. For an individual species, we examined mean shoot height, maximum rooting depth, number of root tendrils contained, maximum diameter of a single root, root:shoot ratio, and pull out resistive force. For the sake of evaluation of plant species, they are categorized into different groups based on their morphological properties. We classified the plants based on mean shoot height (≥50 cm), maximum rooting depth (≥20 cm), number of root tendrils (≥30 no.), maximum diameter of a root (≥ 7mm), root shoot ratio (≥ 0.5, dry), and pull out resistive force (≥ 100N). It was revealed that the species like Eulaliopsis binata, Elaeagnus parvifolia, Saccharum spontaneum, Colebrookea oppositifolia, were characterized with relatively higher number of roots, root longetivity and greater resistance to pulling force. These species are easy to grow and are available on varying site conditions.