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Keywords: Natural Sciences
Plants (Botany)
Issue Date: 2011
Abstract: In this study various pine forests from district Dir were investigated. Their quantitative survey, multivariate analyses, population structure and dendrochronological studies were presented. Thirty mature and least disturbed forests were sampled by pointer centered quarter method throughout the study area. On the basis of analysis, twelve communities of six conifer species and two broad leaved tree species were recognized using their importance values. Cedrus deodara and Pinus wallichiana were the dominant species found in seventeen and ten sampled forests respectively. Taxus wallichaina and Abies pindrow were found infrequently represented in one and three stands respectively. Quercus baloot and Populus nigra were associated as co-dominance species. Pinus roxburghii forests were growing on lower elevations while Picea smithiana were found comparatively on high elevations. A total of eighty two species were found in the understorey of which seventy two were common while eleven species occurred rarely. The group structure inherent in the vegetation and underlying trends in the vegetation were examined. The relationship between vegetation and environmental factors were explored. Five major groups were recognized in tree species data while eleven groups were found in the understory vegetation using TWINSPAN, a divisive clustering technique. The major trends were unraveled by DCA ordination. The groups of trees and understorey vegetation were superimposed on DCA ordination that showed continuity in vegetation. Correlation of environmental factors with the axes of ordination disclosed the relationship with altitude as well as slope. However, edaphic variables including soil nutrients also revealed substantial relationships with the vegetation groups as well as the compositional gradients. Population structures of individual forest were also investigated concentrating on trees dbh size class distribution, density, basal area, age and growth rates that reflect the structural variability and future trends of these valuable forests. This study disclosed that these forests have a multimodal structure that is principally due to anthropogenic activities which is an overriding factor of these unbalanced forests. However, on the other hand, some of the deodar (C. deodara) forests showed considerably stable structures i.e. J-shaped distribution. The age and growth rate of each conifer species were also calculated that offer additional information about forest regeneration potential and provide a baseline for silviculturists and foresters. The present results also confirmed that Pinus roxburghii is the fastest growing species (among those studied) followed by Pinus wallichiana while Picea smithiana was of the slowest growing species. Among the trees, Cedrus deodara was the oldest tree species with the recorded age up to 500 years. Pinus roxburghii reached only up to hundred years of age. Wood samples of twenty four sites were cross matched by using the composite skeleton plot. Among the different sites and species three sites of deodar and two sites of Picea smithiana were cross dated successfully while the remaining sites and species were excluded from further analysis due to complacent ring-width sequences and short interval period. The standardized versions of five site chronologies of two species were produced. A maximum dated chronology of deodar extends back to 1353-2007 A.D was obtained for 655 years. However, common pattern of pointer years were distinguished among all tree ring series of different sites and species. Climate and Rings-width relationship were evaluated by running various types of response function analysis in order to explore various approaches between their interactions systematically. Three versions of chronologies were correlated with local and grided climate data (temperature and precipitation) and as a result standard version of chronology and local climate were found more suitable for analysis due to the high percentage of explained variances. According to these analyses, precipitation in previous October seems to support growth but high temperature does not. Similarly, high temperature in current May is negatively correlated while precipitation in the same month supports growth. Among season, high temperature in spring is deleterious for tree growth while, adequate precipitation promotes forest growth. The overall, studies indicate that climate-growth responses were consistently seen to prevail both between sites and of the same species and between sites composed of different species. Multiple linear regressions were used to calculate past climatic history. Applying this model of transfer function coefficients, the relative effect of annual rings (predictor variable) upon the recorded climate data (predictand variable) was estimated. Temperature and precipitation were reconstructed and extended back to last three hundred years from reliable tree ring sequences. Similarly, spring temperature and precipitation were also reconstructed. Various sets of drier and wetter years were described in the rescaled past climatic data from tree ring series. It is concluded that Cedrus deodara and Picea smithiana have reliable palaeoclimatic potential and this proxy data could be used for predicting future climatic possible changes. It is also suggested to explore greater number of sites and species for better achievements.
Appears in Collections:PhD Thesis of All Public / Private Sector Universities / DAIs.

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