The effects of fructification on the diameter growth of forest trees subject to drought stress.
Final Report Abstract
In this project, various aspects of the fructification of forest trees and their interactions with weather and tree growth were investigated. Common tree species in Central Europe exhibit pronounced masting behavior, where the quantity of cones and fruits varies significantly from year to year, yet with a high level of regional synchronicy within a single year. Using an extensive dataset of individual tree data from southern Germany, we examined how factors such as tree age, social status, and crown condition influence fructification at the individual tree level. The results indicate that dominant trees tend to have the highest probability of strong fructification among most species. This probability increased with tree age and then declines again as a certain age is reached. For some species, the likelihood of strong fructification decreased with increasing crown transparency, while for others, low crown transparency was associated with the highest likelihood of (strong) fructification. Next, we explored how the interplay of masting and drought affects stem diameter growth. Species-specific response patterns were identified, showing that, in particular, beech and spruce exhibited a reduction in stem diameter growth associated with fructification, especially in dry years. In contrast, oak showed an increased stem diameter growth during a mast year compared to a non-mast year, indicating different strategies for carbon allocation. Additionally, the effect of masting on stem diameter growth varied along the stem axis, especially in the crown area where carbon is both assimilated and, particularly in mast years, in strong demand. We also investigated whether masting impacts the wood anatomy of beech. It was found that the proportion of vessels in the tree ring and vessel density are strongly correlated with tree ring width, but these relationships showed little difference between mast and non-mast years. Other characteristics, such as the lumen areas of earlywood and latewood vessels, were influenced by weather but also displayed minimal variation between mast and non-mast years. Overall, the findings of this project enhance our understanding of the factors influencing fructification at the individual tree level, as well as the effects of fructification on tree growth. This knowledge is essential not only for better comprehension of various growth processes and their interactions but also for improving predictions of forest development and decisions concerning management.
