Sustainable forest management is based on data on forest resources and their growth. In recent decades changes in the environment and their effects on forest productivity and forest health are discussed and emphasized the current importance of growth studies.

Recent investigations on growth trends of European forests indicate positive as well as negative changes in forest productivity (Spiecker et al., 1996; see figure 1). Standing volume per ha and average age of stands have increased considerably in recent decades (Kuusela, 1994, Spiecker et al., 1996). Extensive long-term forest growth data have been accumulated on a regional level. The main objective of the project is to coordinate a joint research effort to investigate the growth of one of the most common and economically most important tree species in Europe on an international level. The four regions included in the project represent different climatic conditions and varying levels of atmospheric deposition.

Recent findings on the regional basis clearly show that climatic variation is the major driving force behind growth variation and variation in tree mortality. By comparing growth reactions in different regions and stands under different silvicultural treatments with climatic variation, a more general knowledge about the effects of climatic variation on growth is expected.

Quantitative analysis of past impacts of environmental changes on the growth of Norway spruce (Picea abies (L.) Karst.) will help to understand the observed growth dynamics more clearly and will help to define minimum levels of climate change that will affect forests in the different regions. The findings would be of immediate relevance for forest management planning on the European level, since site-related economical and ecological yield and risk assessment would become more reliable. Information gathered in this project may be used to reduce risks by choosing adequate management strategies.

New data and prognosis techniques are needed for management purposes on a sustained yield basis under changing environmental conditions. Since there is a general tendency to increase average stand volume and average age of trees in Europe it is of great interest to know the effects of density and age on growth, sensitivity of growth, and mortality in a changing environment and under varying loads of pollution. Recommendations for reduction of risks by silvicultural measures and cutting strategies will be among the results of the proposed project.

Figure 1: Growth Trends in European Forests, Studies From 12 Countries. Spiecker et al.1996.
 
 

References:

Kuusela, K. 1994. Forest resources in Europe. Cambridge University Press: Cambridge. 168 p.
Spiecker, H.; Mielikäinen, K.; Köhl, M. and Skovsgard J.P. (eds.) 1996. Growth Trends in European Forests, Studies From 12 Countries. Berlin: Springer-Verlag. 372 p.
 

The general objective of the project is to coordinate a joint research effort to investigate and interpret the growth and growth changes of one of the most common and economically most important tree species in Europe on an international level. The main research objectives are to investigate growth and growth changes under different climatic and atmospheric deposition conditions in Northern and Central Europe with special regard to different silvicultural treatments by:

determining past variations and changes in growth rate of Norway spruce,

identifying and quantifying environmental factors which control growth variation,

investigating effects of increased average age and density of stands on tree growth, tree sensitivity and tree mortality in respect to climatic changes,

developing scenarios of future growth under changing climatic conditions.

wide range of climatic conditions

wide range of nitrogen and sulphur deposition

availability of long-term data sets.

Figure 2: Research areas with geographical and N- and S-deposition gradients.

The site-related analysis of past changes in growth rates of Norway spruce gives a retrospective view of periodic growth variations and long-term growth trends. Changes in growth will be compared with fluctuations in environmental factors such as climatic conditions and atmospheric deposition and with past land use in order to identify and quantify the driving forces behind growth variations. Therefore growth-climate response patterns will be studied based on interannual as well as intraannual growth variations.

Results of the quantitative analysis of past impacts of environmental changes on growth of Norway spruce under different enironmental conditions will help to understand the observed growth dynamics more clearly and are of immediate relevance for silvicultural and forest management planning. Economical and ecological yield and risk assessment, as well as site-related assessment of climate change impact on Norway spruce forest ecosystems will be more reliable.

Scenarios of future growth trends will be based on these results. Therefore possible future environmental changes will be used as input data in the simulations. Knowledge about site-related growth trends of Norway spruce is necessary for sustainable forest management and timber supply for forest industries throughout Europe.

To accomplish the main objectives mentioned above, the following detailed objectives must be fullfilled:

• Determination of standard criteria for tree, stand and growth data suitable for growth analysis within the project.

• Determination of standard criteria for environmental background data suitable for analysis of environment-growth interrelations within the project.

• Determination of standardized statistical methods for growth analysis.

• Compilation of a consolidated data base on tree, stand, growth and environmental background data according to the standardized criteria developed under a)-c).

• Quantitative statistical analysis of past variations in growth and changes in growth rates of Norway spruce on different sites and stands of different ages and under different silvicultural treatments in Central and Northern Europe.

• Quantitative statistical analysis and modelling of growth-climate relationships of Norway spruce under different climatic and atmospheric deposition conditions and different silvicultural treatments in Central and Northern Europe.

- the local to regional scale,

- the transregional or continental scale.

On the regional scale, elevational line transects and transects covering different aspects will be carried out. Effects of age and silvicultural treatment on growth-climate relationships will be examined. In comparing the response patterns between the four research areas it will be examined if the findings on the regional scale can be scaled up to the transregional scale. It will be tested if there is an equivalence of growth-climate response patterns along elevational and latitudinal gradients as well as gradients in deposition loadings. In addition to the different spatial scales, growth-climate relationships will be investigated on different temporal scales. In order to study the process of tree-ring development and the underlying environmental mechanisms which control this development, analysis of intraannual and interannual growth variation will be included in the project.

• Scenario modelling of future growth of Norway spruce under changing environmental and stand conditions.

• Evaluation of the research implications for European forest and timber policies.

• Development of recommendations for management strategies for to mitigate effects of environmental changes on stability of Norway spruce forest ecosystems.