Tropical Forest Restoration in the Eastern Himalaya: Evaluating Early Survival and Growth of Native Tree Species

Abstract

Asian tropical forests have among the highest rates of forest loss in the world. Ecological restoration is a vital step for biodiversity maintenance and climate change mitigation. For restoration practice, evaluation of species performance at early stages is crucial to avoid failure of the efforts and for screening species suitable to a region. Though the long-term performance of restoration plantings has been well-documented, few studies have evaluated the performance during the establishment of the planted saplings, especially in South and Southeast Asia. Restoration efforts in Northeast India, a region experiencing high forest loss, is limited by the lack of species-specific data on survival and growth. We compared inter-specific variation in seasonal survival and growth rates (diameter and height) for multiple native rainforest species from this region. We planted 3022 saplings of 50 species at a degraded open forest site. After 18 months, sapling survival varied between 9.1–94.3% for 32 species, and only six species showed “excellent” survival after 18 months. Eight out of 17 species that were tested for seasonal variation in survival showed significant differences in survival between seasons. While the diameter growth rate varied for species between seasons, the height growth rate was different between both species and season, but the interaction term between species and season was not significant. Certain animal-dispersed, medium to large-seeded primary forest species performed well and are vital for future restoration efforts in this region.