Synergizing population structure, habitat preferences, and ecological drivers for conservation of Cedrus deodara

Abstract

Climate change is impacting forest tree species adversely and making the ecological system vulnerable. The Himalayan cedar (Cedrus deodara), a keystone species in Western Himalayan forests, plays an important ecological role but is under increasing threats from natural and anthropogenic pressures. The current study analyses the population structure, spatial distribution, environmental factors, and future conservation strategies for Himalayan cedar populations in the Kashmir Himalayas. Field sampling was carried out between 2023 and 2024 in various districts of the Kashmir Himalayas. The quadrat method was used to record the vegetation data across an elevational gradient ranging from 1300 to 2700 m. GIS and spatial analysis were used to map population distribution while, cluster analysis was performed to identify species associations. Canonical Correspondence Analysis (CCA) was applied to identify the influence of environmental factors while, Non-Metric Multidimensional Scaling (NMDS) and SIMPER analysis were used to investigate inter-association dissimilarity. The populations showed an average stem density of 110.73 trees/ha and low regeneration rates, with just 15 seedlings per ha on average. Stump density (mean: 90.62 stumps/ha) demonstrated human-induced pressures. GIS and spatial analysis revealed that Cedar populations were mostly found at altitudes ranging from 1900 to 2200 m, with a preference for north-facing slopes. Cluster analysis identified four distinct species associations in which each with a different species richness and ecological composition. Association 3 was the most diverse (Shannon index: 3.31 ± 0.05), while Association 4 showed the highest dominance (0.062 ± 0.002). Canonical Correspondence Analysis (CCA) identified altitude and timber extraction as the key drivers of variation, accounting for 16.2% and 15.2% of the distribution variance, respectively. Grazing, erosion, and fire accelerated the degradation of habitat. Cedar density was influenced by various edaphic parameters, with total nitrogen (R2 = 0.11) and soil moisture (R2 = 0.09) demonstrating the strongest association. Soil pH, electrical conductivity, and total phosphorus exhibited minimal or negligible effects. Associations 1 and 2 were associated with increased soil pH and electrical conductivity, but Associations 3 and 4 were influenced more by nutrient-rich and moisture-retentive soils. Non-Metric Multidimensional Scaling (NMDS) and SIMPER analysis identified a 56.99% dissimilarity between associations, mostly driven by species such as Parrotiopsis jacquemontiana and Viburnum grandiflorum. The study reveals that Himalayan cedar populations in the Kashmir Himalayas face low regeneration rates and significant anthropogenic pressure. Their distribution is influenced by various factors, including altitude, timber extraction, soil nitrogen, moisture, grazing, erosion, and fire. These findings highlight the necessity for targeted conservation strategies. Future conservation strategies should encompass controlled grazing, regulated timber extraction, soil conservation measures, anti-logging policies, ecotourism initiatives, and collaboration among local communities and policymakers.