Impact of root harvest on Decalepis hamiltonii Wight & Arn. population across habitats in Savandurga Reserve Forest, Karnataka, India

Abstract

Decalepis hamiltonii Wight & Arn., is a woody climber, endangered due to the destructive harvest of fragrant roots and substituted for Hemidesmus indicus (L.) R.Br. (Nannari). We assessed the density, size class, distribution across habitat types, disturbance types, and environmental variables that influence the D. hamiltonii population in the Savandurga Reserve Forest (SRF). Method: The entire forest was divided into 1 km² grids, with 10 plots of 5 x 5 m established in each of the 24 grids, totaling 240 plots. Disturbances were categorized as low, medium, and high, while plots were classified into dense, mixed, and rocky outcrop habitats. Results: D. hamiltonii density ranged from 0.1 ± 0.32 to 5.2 ± 2.66 per 25 m² across the grids with an overall mean density of 675 ± 455 stems per ha. The size class distribution showed a typical inverted “J” curve, with fewer saplings (3.01–6.0 cm class), indicating potential future population instability. Stem density was lower in dense vegetation and higher in mixed vegetation and rocky outcrops, with greater densities in areas of higher disturbance. Adult density was mainly influenced by harvesting (78% variation), saplings by NDVI (2.09%) & altitude (18.72%), and seedlings by aspect (4.44%), increasing from the south to the north. Conclusion: Strict monitoring and periodic assessment of the population are essential to protect the seedlings to the sapling stage, regulation of selective harvesting of the adults, and control of the herders feeding the leaves. Encouragement of local and large-scale cultivation to reduce pressure on the wild source and to improve livelihood. Capacity and confidence building of the community with citizen science reporting of destructive harvesting will help the forest department to save the declining population.