Status and Impacts of Invasive Alien Plant Species in the Parsa Wildlife Reserve, Central Nepal

Abstract

The study area is located in the tropical zone of Nepal where the forests are found more vulnerable due to invasive alien plant species (IAPS) infestation. The forest of Pars Wildlife Reserve (PWR) is dominated by Shorea robusta. This work was focused to study the status and impacts of IAPS in the forest ecosystem of PWR. Seven posts of the Reserve were taken as sampling sites; these were Adhabhar, Mahadev Khola, Charbhaiya, Gaduwaline, Nirmalvasti, Bhata and Pratappur post. In each post site, the stratified systematic sampling plots of 10m×10m were laid for the study. Different parameters such as coverage and frequency of IAPS, presence of flowering plant species, tree canopy cover, DBH of the trees and saplings, fire marks and stumping were measured from each plots. The flowering plants were enumerated; invasion level, species richness, factor governing IAPS and its impacts were analyzed. Altogether 231 spp. of flowering plants, 51 spp. of naturalized plants and 14 species of IAPS were reported from the forest of PWR. Ageratum houstonianum Mill. was added to the list of IAPS listed by Tiwari et al. (2005). The coverage and species richness of IAPS in each sampling post areas were significantly different. The invasion of IAPS was found more near settlement than away from settlement in the Reserve. Among 7 sampling post areas, Bhata and Pratappur areas were reported as most problematic sites due to IAPS invasion followed by Adhabhar zone that were considered as sites near settlement. Among 14 spp. of IAPS, Chromolaena odarata was the most abundant and problematic species in each post areas except Bhata. In Bhata post area, Mikania micrantha was found most problematic species. The frequency and coverage of Chromolaena odorata was also the highest near the settlement than away from settlement. The highest number of IAPS belongs to family Asteraceae followed by Leguminosae. The species richness of naturalized plants was found as the best factor to increase the richness and coverage of IAPS in reserve with strong and positive correlation having significant relationship. Similarly, the tree canopy cover of 10-50% was found to permit the best understory light intensity for the growth and reproduction of IAPS with negative trend of relationship. The richness of IAPS was increased by coverage of IAPS itself with positive relationship. Similarly, the impacts of IAPS in tree regeneration were found by suppressing the growth of saplings and seedlings. Native herb species also found to be affected by IAPS negatively.