First insights into the conservation significance and sustainable nature tourism potential of the Diyagama remnant forest, Homagama, Western province, Sri Lanka

Abstract

Forest remnants play a critical role as refugia in conserving biodiversity and sustaining ecosystem services within rapidly urbanizing landscapes. To highlight the conservation significance of Diyagama remnant forest we reported the biological diversity, floristics, forest services, and quantified plant functional traits related to its regeneration and aesthete. Flora, fauna, and macro-fungi were identified through standard techniques. Vegetation structure was enumerated using ten 10 × 10 m plots and the microclimate was recorded. Species dominance and diversity were evaluated using the Importance Value Index, Shannon-Wiener and Simpson’s indices respectively, and the spatial heterogeneity was depicted using Bray-Curtis similarity index based hierarchical cluster analysis. Forty-seven forest services were assessed using semi qualitative three tier rating scheme while carbon sequestration was quantified using available equations. Community Weighted Mean and Functional Service Value of reproductive traits of native shrubs and tree species were evaluated and the contribution of species in forest regeneration and enhancement of aesthete were quantified. A total of 106 plant species, 224 faunal species were recorded, alongside 69 macrofungal taxa including the flagship species Loris tardigradus, Prionailutus rubiginosus and Semecarpus nigroviridis. The predominance of middle-aged trees and scarcity of young and old individuals reflected potential improvements to the forest structure. Ecological dominance was limited to a few species, including the exotic invader Alstonia macrophylla. Diversity indices reflected the fine scale variations within the forest despite its broad similarity of the microclimate and floristics. Among 47 ecosystem services, 68% were functioning at satisfactory levels. Above ground carbon stock of 459.88 tC ha⁻¹ highlighted the importance of forest as an urban carbon sink. Plant trait-based analysis reflected the heavy reliance of fleshy fruits in forest regeneration and the species contribution varied in this regard. The role of Diyagama forest remnant as a refugium is verified. We highlight its sustainable nature tourism potential while conserving its biological assets.