Population structure, age and growth rates of conifer species and their relation to environmental variables at Malam Jabba,Swat District, Pakistan

摘要

This study focuses on age,growth rate and diameter distribution of pine forests in the Malam Jabba area,Swat District,Pakistan.Wood core samples were taken from twenty stands.Picea smithiana was the oldest at 234 years with a 112-cm diameter.Abies pindrow was 125 years with an 80-cm diameter while the oldest Pinus wallichiana was 122 years with 75-cm diameter.The fastest overall growth rate of 1.5±0.1 year/cm was for P.wallichiana on a west-facing aspect,while the slowest 5.8±2.6 year/cm growth was P.smithiana on an eastfacing exposure.P.wallichiana and A.pindrow exhibited marked differences in growth rates over a 5-year period.The highest growth was by P.wallichiana from 1966 to 2006.A.pindrow showed less growth over the same years,such pattern simultaneously reverse from 1911 to 1965.The relationship between diameter and age,diameter and growth rate and age and growth rate were correlated.P.wallichiana and A.pindrow ages were correlated with diameter and growth rates.P.smithiana age was positive correlated with diameter.Generally,topographic and edaphic factors did not show significant correlations with growth rates,although some appreciable correlations were recorded.The growth of P.wallichiana was correlated with elevation while A.pindrow was correlated with maximum water retaining capacity.Diameter and age produced uneven size classes and many size gaps,which could be the result of anthropogenic disturbances.