Influence of altitude and slope-aspect on diversity, regeneration and structure of some moist temperate forests of Garhwal Himalaya

Abstract

The climate and altitude play an important role in composition and distribution of Himalayan vegetation. Hence this study was aimed to understand the influence of altitude and slope aspect on diversity, regeneration, and structure of some temperate forests of Garhwal Himalaya. The maximum mean tree density (627 ± 27.04 trees ha−1) was recorded on southwest facing aspect for Rhododendron arboreum-Quercus semecarpifolia association whereas, minimum (555 ± 43.11 trees ha−1) on northwest aspect for Quercus semecarpifolia-Abies spectabilis association. However, highest mean total basal cover value (99.84 ± 10.9 m2 ha−1) was found on northwest aspect and lowest (79.15 ± 12.9 m2 ha−1) on southeast facing aspect for Q. semecarpifolia-A. spectabilis association. The greater mean Shannon Index values (i.e., trees, 1.40 ± 0.05; shrubs, 1.67 ± 0.05 and herbs, 2.48 ± 0.05) were recorded for R. arboreum-Q. semecarpifolia (CTI), Q. semecarpifolia-A. pindrow (CTII) and Q. semecarpifolia-A. spectabilis (CTIII), respectively, whereas, lower value (trees, 0.59 ± 0.17) for Q. semecarpifolia-A. spectabilis (CTIV), shrubs (1.44 ± 0.16) and herbs (2.0 ± 0.12) for R. arboreum-Q. semecarpifolia association. The tree species like Quercus semecarpifolia, Rhododendron arboreum, Abies spectabilis were found widely distributed in the study area. The regeneration study revealed that southwest facing aspect community vegetation experienced additional threat of extinction by representing 26.67% species as not regenerating. Overall a reverse ‘J’ shaped structure was obtained for all studied communities representing higher densities on lower dbh classes while, The Q. semecarpifolia-A. spectabilis (CTIII) exhibited maximum total basal cover value on higher dbh classes (i.e., 50–70 cm). Henceforth, it could be concluded that the forest community growing between 2800–3400 m asl was comparatively mature and old growth, and could be recommended for conservation purposes.