Vegetation diversity of tembawang in relation to critical land rehabilitation efforts in the Peninsung Catchment, Sepauk Sub-Watershed, West Kalimantan

Degraded land in the Peninsung Catchment is currently a significant concern, necessitating rehabilitation efforts that involve local communities. This study aimed to determine the Important Value Index (IVI) and species diversity within the traditional Dayak agroforestry landscape, known as tembawang and to evaluate the potential of this landscape for rehabilitating the critical land. The research was conducted in Peninsung Catchment (8,111.36 ha), Sepauk Sub-Watershed, Kapuas Watershed, West Kalimantan. A line-nested sampling plot method with 30% sampling intensity was used to collect data on the structure and composition of vegetation, generating the Important Value Index (IVI) to determine species dominance and ecological importance within the vegetation community. PAST software (ver. 4.04) was used to analyse the diversity indices (Shannon and Simpson Index), evenness (E) and hierarchical cluster analysis. The results revealed a highly resilient, multi-layered canopy structure. At the tree stage, the ecosystem maintains a stable structural framework characterised by moderate diversity (H' up to 2.38) and high evenness (E > 0.80), validated by exceptionally robust cluster configurations (CCC = 0.9549). However, the pole stage has a lower diversity (H' < 1.0) as a result of rubber cultivation for economic cultivation. The multilayered vegetation structure of tembawang, consisting of seedlings, saplings, poles and mature trees, indicates strong ecological stability and continuous natural regeneration similar to that of natural forest ecosystems. Therefore, tembawang can be recommended as a locally adaptive agroforestry system that supports soil and water conservation and has potential for critical land rehabilitation in watershed areas.