Implications of irregular shelterwood system on regeneration and species diversity of Sal (Shorea robusta Gaertn. f.) forest in Nepal

Niraj Pokhrel; Sachin Timilsina; Nripesh Awasthi; Anita Adhikari; Bikash Adhikari; Santosh Ayer; Kishor Prasad Bhatta

doi:10.1016/j.heliyon.2023.e23156

Implications of irregular shelterwood system on regeneration and species diversity of Sal (Shorea robusta Gaertn. f.) forest in Nepal

Heliyon. 2023 Dec 2;10(1):e23156. doi: 10.1016/j.heliyon.2023.e23156. eCollection 2024 Jan 15.

Authors

Niraj Pokhrel¹, Sachin Timilsina¹, Nripesh Awasthi², Anita Adhikari³, Bikash Adhikari¹, Santosh Ayer⁴, Kishor Prasad Bhatta⁵

Affiliations

¹ Tribhuvan University, Institute of Forestry, Pokhara Campus, Pokhara, 33700, Nepal.
² Ministry of Industry, Tourism, Forest and Environment, Kailali, Sudurpaschim, Nepal.
³ Tribhuvan University, Institute of Forestry, Hetauda Campus, Makwanpur, 44107, Nepal.
⁴ Agriculture and Forestry University, College of Natural Resource Management (CNRM), Katari, 56310, Nepal.
⁵ Research and Development Centre, Kathmandu, 44600, Nepal.

Abstract

Silvicultural systems are essential for effective forest management and utilize the resources by conserving biodiversity, health, and valuable services forests offer to society. However, Nepal faces a significant knowledge gap due to the limited data on the effect of silvicultural systems and forest management practices on tree diversity and regeneration. Therefore, this study was conducted to assess the effects of canopy opening on natural regeneration and species diversity of Sal (Shorea robusta Gaertn. f.) forest in comparison to managed and control blocks in the southern plains of Nepal under irregular shelterwood systems. The vegetation sampling was carried out by the quadrat method (plot of 10 m* 10 m) for studying 48 plots in both managed and control forest areas. The Shannon-Wiener Index and the Simpson Index were used to measure species diversity, whereas Margalef's index was used to measure species richness. Dominant tree species in both managed and control forest areas were identified through the Important Value Index (IVI). The seedling and sapling density of Sal was found to be significantly higher (p < 0.05) in managed blocks. Seedlings of Sal from the seed origin were notably more abundant in the managed block (p < 0.01), whereas those from coppice origin exhibited higher numbers in the control block (p < 0.01). Sal was found to be dominant species in both managed block (IVI = 199.94) and control (IVI = 108.34). The species diversity and richness were significantly declining in the managed forest (p < 0.01) with higher species dominance in comparison to the control blocks. Our study found a positive correlation of canopy cover with species diversity (r = 0.69, p < 0.01) and richness (r = 0.59, p < 0.01) whereas a negative correlation with seedling (r = -0.43, p < 0.01) and sapling density (r = -0.16, p < 0.01). The application of the irregular shelterwood system in study area has effectively promoted natural Sal regeneration while concurrently reducing species diversity. To strike a balance between timber production and biodiversity conservation in these forests, further research focusing on moderating felling intensity within the irregular shelterwood system is strongly recommended.

Keywords: Irregular shelterwood system; Seed origin; Species dominance; Timber production.