Indian Journal of Science and Technology Vol.2 No. 7 (July 2009) ISSN: 0974- 6846 Research article “Himalayan flora” Sharma et al. Indian Society for Education and Environment (iSee) http://www.indjst.org Indian J.Sci.Technol. 39 0 5 10 15 20 25 30 Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec Month Temperature (°C) 0 100 200 300 400 500 600 Rainfall (mm) Temperature (°C) Max. Temperature (°C) Min. Rainfall (mm) Fig. 1. Climatic data for Mandal-Chopta forest (Source: Forest Dept. of Uttarakhand) Vegetation structure, composition and diversity in relation to the soil characteristics of temperate mixed broad-leaved forest along an altitudinal gradient in Garhwal Himalaya C.M. Sharma*, S.K. Ghildiyal, Sumeet Gairola and Sarvesh Suyal Department of Botany, HNB Garhwal University, Post Box-51, Srinagar Garhwal-246 174, Uttarakhand, India sharmacmin@gmail.com*, skghildiyal@gmail.com, sumeetgairola@gmail.com, sarveshsuyal@gmail.com Abstract: The focus of the study is to characterize the structure, composition and diversity of Banj Oak (Quercus leucotrichophora) forests at different altitudes and slopes in Mandal-Chopta area of Garhwal Himalaya. Competing co-dominant tree layers comprised of Persea duthiei and D. himalense at the higher altitude (2100m a.s.l.) and steeper slope (45°); D. himalense and Betula alnoides at the middle altitude (1700m a.s.l.) and moderate slope (38°); and Lyonia ovalifolia and Myrica esculenta at lower altitude (1550m a.s.l.) and gentles slope (30°) were observed in these forests. Community diversity was highest (3.140) at the higher altitude (site-1) whereas the concentration of dominance followed the opposite trend of the diversity. Physico-chemical properties of soils have revealed that availability of higher average total nitrogen and moisture contents might have given birth to higher total basal cover values at middle altitude. The tree density was positively correlated with the tree diversity and tree richness (P< 0.001). The vegetational parameters A/F ratio, Shanon-wiener index, Species richness, Margalef index and soil parameters especially pH and available phosphate (kg/ha) were significant (P<0.05%) among the forest sites. Keywords: Banj Oak community, Himalaya, species evenness, vegetation analysis. Introduction The Himalayan moist temperate forests are characterized by extensive oak and coniferous forests extending from 1500 to 3000m asl. In the Western and Central Himalayas, the three main Oaks provide a simple and convenient basis for subdivision into three altitudinal zones each i.e., Quercus semecarpifolia Sm. (Fagaceae) Kharsu oak in the upper altitudinal zone (2500m), Q. floribunda Lindl. ex Royle. (Fagaceae) Moru oak in the middle zone (2250m) and Q. leucotirchophora A. Camus. (Fagaceae) Banj oak in the lower altitudinal zone (2000m). These oak forests are usually composed of mainly single species depending on the altitude. Puri (1960) and Champion and Seth (1968) considered that these forests represent climatic climax of one or the other species. Banj oak (Q. leucotroichophora) forests (Forest Sub- Type 12/C1a as per Champion & Seth, 1968) are evergreen high forests of trees of large girth but medium height, rarely over 25m and usually with large branching crowns festooned with mosses, ferns, aroids and other epiphytes. In damp ravines and other favourable sites, there may be an appreciable mixture of deciduous trees contributing to the main canopy. The banj oak forests are exposed to damage or destruction through human agencies, being at a favourable altitude for settlement and cultivation. The species is coppiced regularly near habitations for getting young shoots for quality fodder, which gives a decidedly different appearance from the original undisturbed form. Lopping is extremely prevalent and combined with fuel and a charcoal demand has led to the disappearance of the forests over large areas (Sharma & Gairola, 2007). These forests are not themselves inflammable, but in many localities suffer a good deal from fires spreading up from the pine zone below. A plant community is the collection of plant species growing together in a particular location that show a definite association with each other (Muller-Dombois & Ellengberg, 1974). The most common method of defining this diversity at the ecosystem level is the species. Species diversity is considered as a spatial form of textural diversity and treated both in structure and dynamics of the plant community (Maarel, 1988). However, the concept of diversity is generally concerned with the representation of variability involved in the natural communities. The comparative analysis of species abundance distributions based on species abundance models with associated diversity indices can provide valuable information on the diversity of a community (Magurran, 1988). Another important biodiversity indicator is the relative (proportional) abundance or degree of dominance of individuals among different species. This is usually referred to as evenness or equitability and measures the extent to which species are equally represented in a community. There exists a strong correlation between structural diversity and species diversity (Sahu et al., 2008). An increase in spatial- structural heterogeneity and habitat complexity is