Species diversity of woody vegetation along altitudinal gradient of the Western Himalayas

Abstract

The phytosociological attributes of woody species were investigated along an altitudinal gradient in Kedarnath Wildlife Sanctuary. Detailed sampling was carried out in five altitudinal zones (from 1550 to 3550 m asl). A total of 81 woody species, including 33 trees (28 genera and 22 families) and 48 shrub species (39 genera and 24 families) were reported. Density ranged from 150 ± 19 trees/ha (Zone V, 3350–3550 m asl) to 530 ± 36 trees ha−1 (Zone I, 1550–1750 m asl) and 3.83 ± 0.31 shrubs 25 m-2 (Zone-I 1550–1750 m) to 12.3 ± 0.45 shrubs 25 m-2 (Zone-III 2900–3100 m). Total Basal Cover (TBC) fluctuated between 2.91 ± 0.74 m2 ha−1 (Zone-V) to 37.96 ± 2.95 m2 ha−1 (Zone-I). The diversity index (H̅) of trees varied from 2.097 (Zone-V) to 3.373 (Zone-I) and of shrubs ranged from 2.624 (Zone-V) to 4.209 (Zone-I). The correlation (Carl Pearson) test indicated that species richness, Shannon-Wiener diversity index, β-diversity, and TBC declined sharply with increase in altitude. The average maturity index for trees varied from 16.36 to 33.57 and 11.59 to 32.67 for shrubs. The diversity of woody plants declined as altitude increased, indicating that environmental filtering acts as a key factor in shaping the woody vegetation at high altitudes. In lower altitudinal zones, most of the species exhibited a lognormal curve while species of higher altitudes followed geometric curves. The present study could prove beneficial for the foresters, policy-makers to understand the altitudinal behavior of species diversity and its degeneration patterns so that strategic conservation plan could be implemented in the coming future. Thus, the study is expected to provide information to understand the current status, ecology as well as conservational efforts required for this protected area.