Abstract
Observed recent and expected future increases in frequency and intensity of climatic extremes in central Europe may pose critical challenges for domestic tree species. Continuous dendrometer recordings provide a valuable source of information on tree stem radius variations, offering the possibility to study a tree's response to environmental influences at a high temporal resolution. In this study, we analyze stem radius variations (SRV) of three domestic tree species (beech, oak, and pine) from 2012 to 2014. We use the novel statistical approach of event coincidence analysis (ECA) to investigate the simultaneous occurrence of extreme daily weather conditions and extreme SRVs, where extremes are defined with respect to the common values at a given phase of the annual growth period. Besides defining extreme events based on individual meteorological variables, we additionally introduce conditional and joint ECA as new multivariate extensions of the original methodology and apply them for testing 105 different combinations of variables regarding their impact on SRV extremes. Our results reveal a strong susceptibility of all three species to the extremes of several meteorological variables. Yet, the inter-species differences regarding their response to the meteorological extremes are comparatively low. The obtained results provide a thorough extension of previous correlation-based studies by emphasizing on the timings of climatic extremes only. We suggest that the employed methodological approach should be further promoted in forest research regarding the investigation of tree responses to changing environmental conditions.
Highlights
During the past 15 years the systematic installation and operation of dendrometers and analysis of the obtained data has received increasing interest in forestry sciences
Analysis As a thorough extension of the basic ECA method for two event sequences, in this work, we introduce new multivariate generalizations of ECA termed conditional event coincidence analysis (CECA) and joint event coincidence analysis (JECA)
For positive stem radius variations (SRV) events (Figure 2, left panel), five main observations are made: (i) Tmin and Tmax events have an opposite effect in almost all years and for all tree species
Summary
During the past 15 years the systematic installation and operation of dendrometers and analysis of the obtained data has received increasing interest in forestry sciences. Where additional environmental information is available, dendrometer data can provide information on the tree stems response to external factors, especially meteorological conditions (McLaughlin et al, 2003; Denneler et al, 2010; Miralles-Crespo et al, 2010; Oberhuber and Gruber, 2010; Jezik et al, 2011; Butt et al, 2014) Investigations such as these are important in order to better understand the diurnal cycle of sap flow and leaf water potential (Drew and Downes, 2009). Even though stem radius does not allow estimates of total cell numbers, it is an important proxy for a forest’s above ground biomass (Schulte-Bisping et al, 2012), because it can help to determine the wood volume available for the fixation of carbon (Cuny et al, 2015)
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