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Linear and non-linear stem volume models have wide-ranging applications in forest resource management owing to their ability to provide reliable estimates of independent variables. In the present study, we have used, diameter at breast height (DBH) and tree height data of Pinusroxburghii and Cedrusdeodara to model stem volume in Pithoragarh district of Uttarakhand. To model tree volume, different stem volume equations were used to develop the relationship. Parameters of volume equations are estimated by regression analysis and the best fit model equation was selected. Validation of modelled equation are performed by using various statistics;coefûcient of determination (R2), root mean square error (RMSE), mean deviation (MD), and mean absolute deviation (MAD) to determine best model fit. The results of the study shows that the models V=a+bD+cD2 for Pinusroxburghiiand V=a+bD2H for Cedrusdeodara performed best in almost all fit statistics in comparison with other model equations. These models would provide better calculation of volume stock and helps in future management of forest. [ABSTRACT FROM AUTHOR]

The impact of climate change on trees is conspicuous in the form of tree line response at the higher mountain region. Based on tree ring data, we investigated the age stand structure and tree line dynamics of the Himalayan fir (Abies spectabilis) at Tungnath, Uttarakhand, western Himalaya. This species forms the upper ecotone limit at ~3335 m asl in association with Rhododendron campanulatum, the latter extending further and forming the krummholz ecotone limit. The stand structure and age distribution of fir reveals the presence of high girth class trees at lower altitudes with the oldest tree of ~379 years age at ~3000 m asl. A good number of trees older in age than the age of uppermost tree (~109 years) at ~3353 m asl show the recruitment of fir at the ecotone limit by the early 20th century AD with the shift rate of ~13 m per decade. The highest advancement rate of ~39 m per decade is found during 18th Century AD. Over 300 years old ring width chronology of silver fir indicates that the temperature of winter months, especially February, have positive influence on the tree growth. The presence of trees younger than 100 years within the forest stand near ecotone limit indicates subsequent infilling of forest and also explains the growth behavior of fir trees in relation to increasing temperature of winter months during the last century. Evidences of no regeneration above the present fir limit and the presence of few seedlings within the upper ecotone limit could be related to mixed response to climate and other local factors at this site. In spite of rapid warming silver fir tree line in Tungnath area has not shown upslope advance. It seems that the positive effect of warming in tree growth is nullified by water stress resulting from increased evapotranspiration. [ABSTRACT FROM AUTHOR]