Dating of snow avalanches by means of wound‐induced vessel anomalies in sub‐arctic Betula pubescens

Abstract

Dendrogeomorphic research has long relied on scarred trees to reconstruct the frequency of mass‐movement processes. Injuries have mostly been dated macroscopically by counting the tree rings formed after wounding. Tree‐ring anatomical anomalies induced by cambial injury, in contrast, have only recently been recognized as proxy records of past events. We investigated 12 sub‐arctic downy birch (Betula pubescens Ehrh.) trees scarred by snow avalanches in Norway and Iceland. Earlywood vessel lumina were measured for each tree in the xylem tissue bordering the scars. Seven successive rings were examined, namely two control rings laid down prior to wounding and five rings in the wound xylem. We provide evidence that snow‐avalanche‐induced wounding resulted in atypically narrow earlywood vessels over at least two years. Our data demonstrate that wound‐associated vessel anomalies represent tangible markers of mass‐movement processes, and as such make a viable tool for reconstructing past events. Similar dendrogeomorphic studies based on tree‐ring anatomy can be readily conducted with other mass‐movement processes, as well as with other broad‐leaved tree species. Ultimately, this new approach will foster increment coring over more invasive sampling techniques.

Disentangling the effects of disturbance, climate and tree age on xylem hydraulic conductivity of Betula pendula

“…Quantification of a model's sensitivity to disturbance predictors might be also influenced by the number of available tree rings formed after the treatment, as experimental design should include not only the period immediately following the disturbance, but also several years afterwards to allow sufficient time for both adjustment and recovery. In our study, responses to most of the treatments (tilting, scarring, root exposure) are considered immediate (Hitz et al, 2008;Heinrich and Gärtner, 2008;Arbellay et al, 2013;Groover, 2016), and the graphical representation in Fig. 2 shows that our results are in agreement with this.…”

“…2 shows that our results are in agreement with this. Previous studies have found varying recovery speeds of wood anatomical parameters after strong mechanical events causing cambial damage (flood, rockfall, avalanche), ranging from 1 to 5 years (Arbellay et al, 2012b(Arbellay et al, , 2013Tumajer et al, 2015). Based on this, our experimental design included three analysed post-treatment years.…”

Dendroecological Dating of Geomorphic Disturbance in Trees

“…George et al 2002;Ballesteros et al 2010b;Arbellay et al 2010a,b;Wertz et al 2013). Other processes, such as snow avalanches, were not studied frequently in the past (Arbellay et al 2013). Tree microscopic response to wounding was primarily studied between rings formed in the year of disturbance and subsequent years as well as in uninjured control rings (Figure 2A).…”

Visual dating of rockfall scars in Larix decidua trees

“…To protect itself against fungi and bacteria infestation, an injured tree will start to compartmentalize the affected wood (Shigo, 1986), form boundary zones within the bark (Biggs, 1985), and initiate the formation of anatomical changes within the xylem such as reduced tracheid or vessel lumina (Stoffel and Hitz, 2008;Arbellay et al, 2010Arbellay et al, , 2012Arbellay et al, , 2013 or the production of callus tissue (Neely, 1979(Neely, , 1988Delvaux et al, 2010)-a thin layer of undifferentiated cells as a response to injury that may help reestablish the vascular cambium after scarring (Smith and Sutherland, 2001). In the case of deep wounds, which are a common feature in trees injured by highenergy, geomorphic impacts (e.g., Dorren and Berger, 2006;Schneuwly-Bollschweiler and Schneuwly, 2012), trees will typically start to form callus as an extension of the undisturbed vascular cambium along the wound edges.…”