The relationship between area, and vegetation structure and diversity in montane forest (shola) patches in southern India

Abstract

Background: The montane forests of the higher altitudes of the Western Ghats in southern India, called ‘sholas’, are naturally patchy and closely juxtaposed with grasslands. Palaeoclimatic studies have indicated that the sholas have expanded in warmer climatic regimes and the grasslands during colder climates. Therefore during the present post-glacial climatic regime sholas may be in the expansion phase. Aims: We aimed to test if sholas are in an expansion phase; in particular, if smaller sholas could be at earlier successional stages than larger sholas. Methods: We enumerated all non-climbing plants (≥ 1cm dbh) in 18 shola patches ranging from 0.09ha to 15ha in area. We tested whether species richness, basal area, and proportion of large trees (≥ 30 and ≥ 60cm dbh) increased with shola size, and rare and ‘ecotone’ species decreased with shola size. Results: As predicted, species richness, basal area and the proportion of large trees (≥ 60cm dbh) increased with shola size, whereas the proportion of rare and ‘ecotone’ species decreased with shola size, and species in smaller sholas were a nested subset of those in larger sholas. Conclusions: These results suggest that shola forests are a highly structured plant community, possibly driven by succession.