Forest regrowth reduces richness and abundance of invasive alien plant species in community managed Shorea robusta forests of central Nepal

Abstract

Background: Natural forests are generally considered to be less prone to biological invasions than other modified ecosystems, particularly when canopy cover is high. Few decades of management of degraded forests by local communities in Nepal has increased canopy cover and altered disturbance regimes. These changes might have reduced the abundance of invasive alien plant species (IAPS) in forests. To understand the status of IAPS in such forests, we studied two community managed Shorea robusta forests (Sundari and Dhusheri) of Nawalpur district in central Nepal. In these two forests, vegetation sampling was done using circular plots 10 m radius at forest edge, gaps, and within canopy. Variation of IAPS richness and cover across these microhabitats were compared, and their variation with tree canopy cover and basal area analyzed. Result: Altogether 14 IAPS were recorded in the study forests; among them Chromolaena odorata, Ageratum houstonianum, and Lantana camara had the highest frequency. Mikania micrantha was at the early stage of colonization in Sundari Community Forest (CF) but absent in Dhuseri CF. Both IAPS cover and richness was higher at forest edge and gap than in canopy plots and both these attributes declined with increasing canopy cover and tree basal area. Conclusion: The results indicate that increase in canopy cover and closure of forest gaps through participatory management of degraded forests can prevent plant invasions and suppress the growth of previously established IAPS in Shorea robusta forests of Nepal. This is the unacknowledged benefit of participatory forest management in Nepal.

Are Mediterranean forest ecosystems under the threat of invasive species Solanum elaeagnifolium?

“…to the onset of growth. Khaniya & Shrestha (2020), studying 14 invasive tropical plants reported similar results, finding that the increased canopy cover and the closure of forest gaps can prevent plant invasions and suppress the growth of established invasive plants in Shorea robusta forests of Nepal.…”

Distribution and impact of invasive alien plant species in Bardia National Park, western Nepal

“…Natural ecosystems such as grasslands without trees often accumulate greater numbers of IAPS than the surrounding forested areas (Siwakoti et al 2016). Within forest ecosystems, microhabitats with low tree canopy cover such as forest edges and canopy gaps provide environments that are more conducive to the establishment of IAPS than sites with high tree canopy cover (Arellano-Cataldo & Smith-Ramírez 2016, Khaniya & Shrestha 2020). Similarly, rivers act as corridors for the dispersal of IAPS; they provide suitable habitat and contain a reservoir of propagules for further invasions (Parendes & Jones 2000, Levine 2001.…”

Assessment of invasion of Ageratina adenophora in the plantation forest of Nepal

“…Opening of forest (canopy gap) makes the environment favorable for IAPS to dominate other vegetation (Vargas et al, 2013). On the contrary, increasing tree canopy closure in the forest suppress growth of IAPS (Khaniya & Shrestha, 2020). The best option to control the population of A. adenophora in pine plantation forest could be a periodic removal of this invasive species from the forest ground with least disturbance to canopy cover of the forest.…”