ESTIMATING SAPLING VITALITY FOR SCOTS PINE (PINUS-SYLVESTRIS L.) IN RUSSIAN KARELIA

A new method is proposed for estimating vitality or growth potential f or saplings of Scots pine (Pinus sylvestris L.), based on height, diam eter and height increment. A two-stage process was used to establish t he vitality index. The logarithms of height, diameter and height incre ment were regressed against age, to adjust for the wide range of ages present in our data (c. 10,000 saplings with ages spanning 4-50 years) . Then principal component analysis was used to obtain coefficients, w hich were, in turn, standardized on each axis to provide a vitality in dex scaled in standard deviations, This standardized scale allows the rank of an individual in the population to be assessed, and draws atte ntion to possible outliers. The use of age-adjusted residuals ensured that the estimator was independent of age, and stable over a wide age range. The first principal component indicates if a sapling is relativ ely tall (weight = 0.5), thick (w = 0.5) or fast-growing (w = 0.7) for its age. Most of the information is contained in the first principal component, but the second component, which explains about 10% of the v ariance, appears to offer some utility as an indicator of 'acceleratio n' due to changing conditions. The resulting measures of vitality have been useful for research and management in the dry lichen-moss pine f orest in Russian Karelia, but are specific to this species, locality a nd ecotype. Further research and site-specific data are necessary to a dapt the system to other situations. (C) 1997 Elsevier Science B.V.