Some recent analyses concerning changes in growth for the last three decades at least are presented. Different data and methods were used in order to detect growth trends. Growth influencing parameters, which are not related to growth trends have been largely excluded.
The first part of the paper deals with results of the Austrian Forest Inventory. Some major findings of four inventory periods beginning in 1961 show a steady increase of increment in basal area, in top height as well as in volume. Changed methods for the determination of increment in the different inventory periods has been analysed and apparently has no great influence on the comparability of the results since 1961.
Two approaches towards growth trends using stem analyses data are given. The first concludes, that the current annual volume increment of at least 100 years old spruce (Picea abies) stands has not decreased in the last three decades. These findings from two different locations (each with three elevations) in the Austrian Alps are derived from 200 analysed stems. The second investigation using stem analyses was carried out on sites of the Bohemian Massif, as an example for outer alpine regions of Austria. On four locations height growth of trees with different age-classes (60, 80, 100) was compared. At all locations the slope of the height curve of the young trees was steeper than the slope of the elder trees.
Growth trends based on radial-increment analyses were investigated using long increment cores from Norway spruce (Picea abies), which had been taken from the National Inventory in 1977 and in the period 1986/90. Both series showed continuously increasing mean radial increments of the first twenty years of trees with different germination over time.
The different increment data of the National Inventory were analysed more detailed in order to find some structure in the increase of increment to get hints for possible cause relationships. Stand characteristics like tree composition, density or age show higher correlations with increase of increment than site characteristics do.
Key words: forest inventory, stem analyses, increment cores, top height growth.
Correspondence: Klemens Schadauer, Forest Research Station, Seckendorff-Gudentweg 8, A-1131 Wien, Austria