The rhizosphere effect in trees of the Indian Central Himalaya with special reference to altitude

Abstract

The present paper deals with the rhizosphere effect exerted on the microbial communities by ten representative and important tree species of the Indian Himalayan region. The study covered a wide altitudinal range (1200 to 3610 m above mean sea level) representing subtropical to subalpine climatic conditions. The rhizosphere to soil (R:S) ratio was found to range from 0.2 to 3.5, 0.3 to 2.9, and 0.3 to 3.4, for bacteria, actinomycetes and fungi, respectively. Barring a few exceptions, generally the tree species of subtropical and temperate regions exerted a slight stimulatory effect on the rhizosphere microorganisms. Coniferous species of the subtropical and temperate locations viz., Cedrus, Pinus and Taxus supported relatively higher microbial population in the rhizosphere in comparison to other species. Abies pindrow (a conifer), Betula utilis, and Rhododendron campanulatum, species of the subalpine region were found to exert a distinct negative rhizosphere effect. The negative rhizosphere effect coincided with lowering of the soil pH in the rhizosphere region. © 2007, Penkala Bt.