Ecological Niche Modeling of the Endemic Himalayan Near-Threatened Treeline Conifer Abies spectabilis (D.Don) Mirb. in the Indian Central Himalaya

Abstract

Abies spectabilis (D.Don) Mirb. is an endemic Himalayan near-threatened coniferous species and the predominant treeline-forming species in the Indian Central Himalaya (Uttarakhand). The impact of climate change and anthropogenic activities is perilous to its habitat distribution. Accurate species habitat distribution is a prerequisite for efficient conservation planning. This vital information is still missing in the Indian Himalayan region for A. spectabilis. This study models the habitat suitability of A. spectabilis in Uttarakhand and discusses the management implications. Species occurrence records from primary and secondary sources were used with environment variables for habitat suitability modeling using the MaxEnt approach. Environment variables included bioclimatic (BCVs), topographic, edaphic, and anthropogenic variables. The BCVs from two global bioclimatic databases CHELSA (model 1) and WorldClim (model 2) were used. Models were validated using threshold-independent measures and further used to build habitat suitability maps. Both models performed optimally; however, model 2 had higher average values for the area under the curve (AUC) (0.980), partial AUC (0.977), and the AUC ratio (1.954) indicating higher predictive power. The precipitation of the driest month (BIO14) was the most important predictor variable under both models. The habitat suitability area for model 1 (16,324.57 km2) was five times greater than model 2 (3323.86 km2). Only 826.86 km2 area (model 2) was highly suitable for A. spectabilis. The habitat suitability is concentrated predominantly in a tight group in the northern region of Uttarakhand. Chamoli (8.43%), Rudraprayag (6.20%), and Uttarkashi (0.53%) were the top 3 districts with the highest percentage of high suitability regions under model 2. The results from the habitat suitability distribution of A. spectabilis suggest in situ conservation of present occurrences and monitoring of the regeneration process. Stringent monitoring in the protected areas and the highly suitable habitat regions modeled must be used for assisted regeneration and plantation-based habitat enhancement of this endangered species.