Forest Vegetation And Dendrochronology Of Gilgit, Astore And Skardu Districts Of Northern Areas (Gilgit Baltistan), Pakistan

A quantitative forest vegetation study was conducted in 40 stands from Astore, Gilgit and Skardu three districts of Gilgit-Baltistan.The arboreal vegetation was analyzed using point centered quarter method while understory was sampled using circular quadrates.On the basis of phytosociological analysis following 5 communities of mixed tree species and 5 pure stands were recognized on the basis of importance value. 1) Pinus wallichiana-Juniperus community, 2) Pinus wallichiana Betula community, 3) Picea-Juniperus community, 4) Picea-Pinus wallichiana, 5) Pinus wallichiana-Pinus gerardiana community, 1) Picea smithiana pure stands, 2) Pinus wallichiana pure stands, 3) Betula pure stands, 4) Juniperus macropoda pure stand and 5) Abies pindrow pure stand .Eighty three plants species of various herbs, shrubs and seedlings of trees were observed and identified on the forest floor. Among the understory vegetation Thymus serpyllum (2.8-18%), Fragaria nubicola (3.8- 17.5%), Leontopodium leontopodinum (3.7-17.1%), Bergenia stracheyi (1.5-16.1%), Artemisia brevifolia (2.7-15.3%), Bistorta affinis (2.2-15.1%), Tanacetum artemisioides (1.2-15.2%), Thymus linearis (6.2-15.1%), Geranium wallichianum (6-15%), Leontopodium himalayanum (3-14.9%) were abundantly distributed with the range of relative frequency respectively.Dbh size classes of each stand as well as overall size class of four dominant species i.e. Pinus wallichiana, Picea smithiana, Juniperus excelsa and Betula utilis were studied. Size class showed varied distribution patterns in different stands. Most of the deviation from an ideal distribution may be explained in terms of anthropogenic disturbances, i.e. grazing, cutting, sliding, burning and other human induced factors. Therefore, these forests do not appear to be in stable condition. It is concluded that if prompt action is not taken to stop current damaging practices, these valuable forests will vanish in a few decades.Ward’s cluster analysis and Principal Component Analysis (PCA) were applied to investigate the relationships between soil properties and vegetation. Sixteen soil characteristics and Importance value index were taken in case of tree vegetation while in case of understory vegetation frequency of species was used to investigate the distribution pattern of vegetation. Based on Ward’s cluster analysis seven groups were identified from tree vegetation data and six groups were recognized in case of understory flora.These groups clearly showed the distinct species composition and associated environmental (soil) characteristics. Relationship between vegetation and topographic factors was also studied. Ward’s cluster analysis and Detrended correspondence analysis (DCA) were applied to seek the vegetation distribution and composition.The groups of tree and understory vegetation could be readily superimposed on DCA ordination plane.Classification and ordination showed similar distribution pattern of tree species as well as understory vegetation thereby complementing the results of each other.Modern Dendrochronological methods were applied to analyze growth rates and age estimation of Pinus wallichiana A.B.Jackson (blue pine) from the forest of Ganji valley Himalayan range of Pakistan.Twenty eight cores from 14 trees were obtained to determine age and growth rates.Pinus wallichiana showed mean age of 173 years while highest (363years) age was recorded from 70 cm Dbh tree.The mean growth rate observed in this species ranged from 3 to 15 year/cm in case of trees while in case of seedlings showed 0.8 to 2 while correlation between Dbh and age was significant.Correlation between age and growth rate in case of seedling found significant while in case of tree it was not significant. Dbh and age were found significant in both cases.Growth rates in every ten years interval from 1720 to 2010 also estimated. It is concluded that growth rate is gradually not significantly on every 10 year basis, however each period is significantly differs 40 to 50 years. Seedling in the past period also show that the vegetation is deteriorating with the passage of time, therefore a special attention is required to save these forests.These important forests exist under anthropogenic threat and environmental disturbances .Some of them may easily be managed as indicated by the presence of large number of seedling. However stands with paucity of seedlings shall need more serious attention.In addition ring-width chronology of 211 years (AD 1730-2010) was developed.Chronology statistics showed that Pinus wallichiana have the past climate signal.Strong correlation has been observed between tree growth and previous November temperature and July indicating that winter warmth is the main factor responsible for tree growth. Correlation analysis between tree ring chronology and grid data also indicates that summer temperature is useful for tree growth.Greater numbers of samples are needed to provide better results in this regard.