Assessment of population ecology and potential habitat modelling of Schleichera oleosa in Uttarakhand Himalaya of India: implications for management and conservation

Abstract

Schleichera oleosa (Lour.) Oken is an important tree species and holds great ecological and economical importance in the lower Western Himalaya of India. Unfortunately, its populations in the region are facing decline due to range of natural (extreme weather/edaphic conditions and invasion of invasive alien species) and human-induced disturbances (grazing, lopping for fodder and fuel wood consumption). To address this issue, a study was conducted in the Doon Valley of the lower Western Himalaya to evaluate the population status and regeneration pattern of this species. Additionally, the study aimed to identify and map the potential habitat of the Indian lac tree in this region. Therefore, a detailed vegetation study was conducted using the stratified random sampling procedure at elevations between 250 and 1000 m. The relative values of frequency, density, and abundance were used to determine the importance value index (IVI) for tree species. These IVI data was further used to re-congregate the quadrates to know the forest association; following this the multivariate analysis was conducted using PAST 4.0 software to group vegetation into different catagories. In the present study, we categorized the tree species into 8 distinct plant associations as Anogeissus − Lannea − Adina, Lannea − Mallotous − Schleichera, Schleichera − Lannea − Syzygium, Schleichera − Anogeissus − Adina, Holoptelea − Lagerstroemia − Schleichera, Schleichera − Cordia − Albizia, Shorea − Mallotous − Cassia, and Azadirachta − Senegalia − Tectona association on the basis of species dominance. The study observed a total of 177 species in S. oleosa forests, including both native and exotic species. Among these, 89 species (50.28%) were classified as trees, 31 species (17.51%) as shrubs, 37 species (20.90%) as herbs, and 20 species (11.30%) as climbers. In various associations, the overall density of S. oleosa trees ranged from 16 to 86 individuals per hectare, while the total tree density ranged from 213 to 540 individuals per hectare. The maximum density of saplings for S. oleosa was recorded as 253 individuals per hectare, while for seedlings, it was 2750 individuals per hectare. Of the eight association types that have existed in the area, the Azadirachta − Senegalia − Tectona association showed a complete failure of regeneration (absence of seedlings or saplings), while the Holoptelea − Lagerstroemia − Schleichera, Schleichera − Cordia − Albizia and Shorea − Mallotous − Cassia association showed absence of saplings. In order to create a species conservation and management plan, we utilized the MaxEnt model to develop a potential distribution map for the species. The results obtained from this model were quite satisfactory, with an AUC mean of 0.929. The model determined that an area of 152.85 km² is highly suitable for the species and could potentially be utilized for species reintroduction. Moreover, the present study emphasizes the importance of regularly monitoring species populations to effectively plan the conservation and restoration efforts. It also highlights the need to develop standardized propagation techniques for mass multiplication, conserve species both in their natural habitats and in controlled environments, and raise awareness about these species among the local community.