Changes in forest growth

The forest growth curves over a long period of rime are suitable indicators for changes in forest eco-systems. Hence, the investigation of growth tren ds is based on the analysis of long-term yield figures on experimental plot s, increment cores and consecutive inventories. Growth changes may be diagn osed from these data, together with yield cable comparisons, constant age m ethod, comparison of generations and the evaluation of consecutive inventor ies. It has been found that increments in forest stands, considered on a su pra-regional scale, are showing a considerable upward trend over the past f ew decades. For the past two decades repeated forest inventories in Bavaria have diagnosed an increase of 10-20 % in standing volume and show that spe cies-specific annual volume increment exceeds yield tables by 12 to 43 %. I n the Northern hemisphere the uncontested rise in temperature and prolongat ion of the vegetation period offer a probable explanation for supra-regiona l increment increase. This increase is overlaid by various factors with loc al and regional impacts such as local site conditions, nutrient inputs and biotic stress factors. This superimposition brings about a great variety of increment reaction patterns and positive as well as negative deviations fr om the expected increment curve for typical age classes. It also provides a n approach towards explaining the paradox that downright hypertrophic growt h, increment decreases and stand dissolutions may occur side by side and at the same time. Forest research and forest management need to react to thes e changes in growth conditions by developing and applying site-dependent gr owth models, for it is through these means char future silvicultural decisi ons may be put on a reliable basis of actual figures.