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Pretzsch, Hans The information potential of crown allometry for tree and stand dynamics Keynote
Hans Pretzsch1
(1) Technical University of Munich

Presently tree crown shape and forest stand structure are accessible by Lidar technology as easily and precisely as never before. For this study we used Lidar data but mainly classical crown measurements, as they are available since the 1950ies and show the information content of time series of crown data. Such longer times series are not yet at disposal from Lidar, but they will be available in future. This presentation deals with the relevance of crown information for analyzing, regulating, and predicting tree and stand development. First, empty space in forest stands is considered as a resource, and it is shown how crown size and shape determines the canopy space filling. In mixed stands complementary crown shapes determine the canopy and stand packing density, stand productivity, and overyielding compared with mono-specific stands. We stress how a consideration of the species-specific crown characteristics and the packing density can improve the assessment and silvicultural stand density regulation.

Second, we demonstrate that the crown size provides valuable information about the growth, growth efficiency, and growth trend of trees. The growth efficiency of crown shows an ontogenetic drift with progressing size development. The fact that small crowns can be more efficient than tall crowns explains the stand growth response to different thinning and transition methods and is relevant for silvicultural decision making.

Third, the relevance of the crown shape for wood quality will be stressed. Crown characteristics can be used for estimating the E-Modul and stiffness of round wood and wood products. We compare crown allometry and wood quality of European beech in mixed and mono-specific stands.

Those examples raise the potential of crown data and suggest a successful integration and consideration of crown characteristics in experimental plot surveys, forest inventories, tree and stand models and in silvicultural prescriptions. Beyond its significance for production functions, crown allometry determines many other ecosystem functions and services such as structural and compositional diversity and habitat structure, the amenity and recreation functions as well as many protection functions (e.g., flooding, erosion, noise).