SIDDIQUI ET AL (2013), FUUAST J. BIOL., 3(2): 141-155 PRESENT STATUS AND SIZE CLASS STRUCTURE OF SOME CONIFER DOMINATING FORESTS FROM MOIST TEMPERATE AREA OF WESTERN HIMALAYAN AND HINDUKUSH REGION OF PAKISTAN MUHAMMAD FAHEEM SIDDIQUI 1 , MOINUDDIN AHMED 2 , SYED SHAHID SHAUKAT 2 IMRAN AHMED KHAN 3 , ATTA MUHAMMAD SARANGZAI 4 AND NASRULLAH KHAN 5 1 Department of Botany, University of Karachi, Pakistan 2 Laboratory of Dendrochronology and Plant Ecology, Department of Botany, Federal Urdu University of Arts, Science and Technology, Gulshan-e-Iqbal, Karachi 3 Department of Geography, University of Karachi, Pakistan 4 Department of Botany, University of Baluchistan, Quetta-Pakistan 5 Department of Botany and Biotechnology, University of Malakand, Dir Lower * Corresponding author e-mail: mfsiddiqui2011@yahoo.com Abstract Size class structure of conifer dominating forests of moist temperate areas is presented in this paper. On different environmental gradients (elevation, slope and aspect) sampling were carried out at 41 stands by point centered quarter method. In moist temperate areas, conifers are dominant as compare to angiospermic trees. Five conifers and seven angiospermic trees were recorded during the study. Among conifers Pinus wallichiana occupied highest frequency found in 35 stands while Abies pindrow occurred in 27 stands with high importance value and density. Cedrus deodara is well tolerant in different climatic conditions, recorded from 22 sampling sites. Taxus fuana and Picea smithiana attained low frequency and density, recorded from 6 and 5 stands respectively. Angiospermic species associated with conifers attained very low density. Quercus incana, Quercus ilex, Pyrus pashia, Albizia chinensis, Juglans regia, Populus pamirica and Populus alba occurred in few sampled forests. Most of the forests showed uneven size class structure but some forests showed inverse J shaped size class distribution which showed ideal regeneration potential. Most of the forests were under threat due to high degree of anthropogenic disturbance i.e. illegal cutting and over grazing. Introduction In the studies on population dynamics of tree species the density size class structure is often examined. Density size class structure has been particularly widely applied in forest ecology and phytosociology (Curtis and McIntosh, 1951). According to Kelly and Larson (1997) the principal problem encountered when studying the population dynamics of a forest community is the enormous length of time required to follow individuals from germination to death. Instead, present day stem densities structure is used to infer past fluctuations in population size and to make predictions of future trends. The life history pattern of an individual tree, or the structure of the population, can be conceived as comprising a series of stages (e.g. seedling, saplings, poles, mature trees etc.). Saxena and Singh (1984) suggested that population structure of a species in a forest can convey its regeneration behavior. Population structure, characterized by the presence of a sufficient population of seedlings, saplings and young trees, indicate a successful regeneration of forest species. Harper and White (1974), and Harper (1977) suggested that size may be a better predictor of reproductive output than age and that balanced or stable size distributions in higher plants may be analogous to balance or stable age distributions in higher plants. Natural disturbance plays a critical role in mediating old-growth forest dynamics and disturbance vary in type, scale, and effect on stand structure (Pickett and White, 1985, Pickett et al., 1989). The theory of community and ecosystem dynamics has benefited greatly from understanding of the role of disturbance and in particular, the concept of gap or patch dynamics. Localized disturbance occurs occasionally at different points in a landscape, resulting in patches that are in different stages of response to disturbance (Pickett and White 1985). Within any forest landscape, the relative proportion of the various stages of stand structural and / or stand successional development depends to a large extent on the periodicity, magnitude and spatial and temporal stochasticity of any particular disturbance event. Forests dominated by relatively major disturbances are often viewed as a mosaic of relatively discrete seral or development patches of varying size structure. Non- equilibrium patch dynamics have become the dominant ecological paradigm by which to understand the relationship between forest and stand-level structure and disturbance (Pickett and White 1985; Wu and Loucks 1995). Spatial distribution of disturbance is determined by factors that influence the size and location of disturbance events. If trees at the gap margin are more likely to die than random canopy trees for instance, canopy gaps would expand (Worrall et al., 2005).