Variations in Tension Wood of Two Broad‐Leaved Tree Species in Response to Different Mechanical Treatments: Implications for Dendrochronology and Mass Movement Studies

Reaction wood formation, in particular compression wood in conifers, has often been used to date geomorphic events such as debris flows or snow avalanches. However, very little is known yet about the variations of tension wood formation and particularly cross‐sectional vessel characteristics in response to different mechanical impacts. To test whether different intensities and characteristic forms of tension wood formation induce the formation of vessels with changing sizes, growth experiments with different treatments were conducted with alder and beech followed by wood anatomical analysis of the vessels. The experiments comprised bending treatments of varying severities in combination with cambium wounding and other alterations. The treatments were successful in inducing different intensities in tension wood expressed by variations of vessel lumen area (VLA). An increasing bending stress resulted in the formation of lower VLA values. When the apex or the root system was damaged or the apex remained vertical, VLA values decreased less and the tension wood formation was regarded as less intense. Our research shows that VLA is affected by mechanical impacts and that the application of wood anatomical techniques can potentially provide supplementary information about type and intensities of past mechanical impacts in angiosperm tree growth.