The effect of forest management and neighborhood diversity on seasonal tree growth responses
Final Report Abstract
The project “The effect of forest management and neighborhood diversity on seasonal tree growth responses” focused on analyzing the growth response of trees as a function of local neighborhood identity. As the choice of tree species and hence the design of tree mixtures is one of the most important forest management decisions the projects addressed one key element of the DFG-exploratories: which impact does land-use has on diversity and ecosystem functions, in our case productivity and stability? In this project high-resolution dendrometer measurements, dendrochronological investigations and wood stable isotope measurements were combined to investigate the impact of neighborhood diversity on longterm growth performance and drought response of European beech in the three Biodiversity-Exploratories set up by the respective DFG-priority programme. It was shown that on different time scales target trees whose competitive neighborhood consisted of co-occurring species exhibited a superior growth performance compared to beeches in pure stands of the same investigation area. This general pattern was also found in exceptional dry years. Although the summer droughts of 1976 and 2003 predominantly caused stronger relative growth declines if target trees were exposed to interspecific competition, with few exceptions they still formed wider annual rings than beeches growing in close-by monocultures. Within the same study region, recovery of standardized beech target tree radial growth was consistently slower in monospecific stands than in the neighborhood of other competitor species. These findings suggest an improved water availability of beech in mixtures which is in line with the results the of stable isotope analysis. Apparently the magnitude of competitive complementarity determines the growth response of target beech trees in mixtures. The results of our project strongly suggest that the sensitivity of European beech to environmental constrains depends on neighborhood identity. Therefore, the systematic formation of mixed stands tends to be an appropriate silvicultural measure to mitigate the effects of global warming and droughts on growth patterns of Fagus sylvatica. As under natural conditions pure beech forests but not mixed stands would dominate throughout Central Europe, our results point towards positive effects of forest management on ecosystem functioning if mixtures are promoted. Further analyses will be carried out to see at which point of time within a year beech benefits most of interspecific neighborhood and whether or not it’s better performance in mixed stands is reflected in selected leaf traits.
Publications
- (2013) Crown modeling by terrestrial laser scanning as an approach to assess the effect of aboveground intra- and interspecific competition on tree growth. Forest Ecology and Management 310: 275-288
Metz J, Seidel D, Schall P, Scheffer D, Schulze E-D, Ammer C
(See online at https://doi.org/10.1016/j.foreco.2013.08.014) - Site‐adapted admixed tree species reduce drought susceptibility of mature European beech. Global Change Biology Vol 22 Issue 2, February 2016, Pages 903-920
Metz J, Annighöfer P, Schall P, Zimmermann J, Kahl T, Schulze, E-D, Ammer C
(See online at https://doi.org/10.1111/gcb.13113)
