Distinct growth phenology but similar daily stem dynamics in three co-occurring broadleaved tree species

Abstract

Dendrometers offer a useful tool for long-term, high-resolution monitoring of tree responses to environmental fluctuations and climate change. Here, we analyze a 4-year dendrometer dataset (2014-17) on European beech (Fagus sylvatica L.), common hornbeam (Carpinus betulus L.) and pedunculate oak (Quercus robur L.), co-occuring in a mixed broadleaved forest in northeastern Germany. In our analyses, we focus both on seasonal growth dynamics as well as on the environmental forcing of daily stem-size variations. Over the study period with contrasting weather conditions, we observed species- and year-specific differences in growth phenology (i.e., growth onset, cessation and duration). Oak was characterized by early growth onset and long growth duration in all years as compared with beech and hornbeam. The analysis on the environmental forcing of daily stem dynamics revealed, however, highly similar responses for the studied species, with current-day vapor pressure deficit and sunshine duration negatively, and relative humidity and precipitation positively affecting stem size. When considering lagged effects, environmental conditions often oppositely affected stem-size changes. No consistent seasonality in environmental responses was detected, though specific weather conditions were found to affect temporal patterns in individual years. We suggest that the high similarity in environmental forcing observed between tree species can be explained by daily stem-size changes mainly reflecting tree water status rather than tree growth. Our results stress that correcting dendrometer series for reversible stem hydrological changes is of utmost importance to better quantify tree growth from dendrometers in future.

Seasonal Drought Effects on Intra-Annual Stem Growth of Taiwan Pine along an Elevational Gradient in Subtropical China

“…To assess differences in intra-annual stem growth dynamics between elevations and years, we defined the critical dates of stem growth phenology (i.e., timings of onset, peak and offset) and estimated growth rates and annual increments from individual dendrometer records. While detecting of growth initiation and cessation from dendrometer-based stem radial variations likely to be confounded by hydrological processes in stems, the estimations should be considered as proxies of seasonal stem growth dynamics [16,23,27,29,32]. In subtropics, the high winter air-temperature (above −4 • C) yields little shrinkage of stem radius [21], and soil temperature and moisture are generally optimal for root water uptake during winters (in this study, soil temperature >4 • C and soil water content >0.18 m 3 m −3 across sites), implying the absence of pronounced tree water deficit and spring rehydration in tree stems.…”

“…The parameter estimations were computed with ordinary least squares method (SAS 9.1, SAS Institute, Cary, NC, USA). For each individual tree and year, we defined stem growth onset and offset as the dates when 5% and 95% of the annual increment were reached [16], respectively, and growth duration as the difference between onset and offset. The parameters of Gompertz models can be used to describe growth rates and its inflection points.…”

“…Seasonal stem growth dynamics have been intensively monitored in boreal and temperate forests using dendrometers and quantitative wood anatomy (e.g., micro-coring) [13][14][15][16][17][18]. While wood anatomical methods allow for an accurate description of wood formation at the cellular level through weekly sampling micro-cores, dendrometer-based stem radial variation can provide detail tree physiological reactions at higher temporal resolutions (sub-hourly and daily) without wounding the cambium.…”

Combining Dendrometer Series and Xylogenesis Imagery—DevX, a Simple Visualization Tool to Explore Plant Secondary Growth Phenology

“…The most common approaches to study seasonal tree growth dynamics and wood formation phenology include the monitoring of stem-size variation (dendrometers), repeated wounding of the cambium through the pinning technique (e.g., Gričar et al, 2007) and repeated cambium sampling through microcores (e.g., Mäkinen et al, 2008;Drew and Downes, 2009;Prislan et al, 2013;Balzano et al, 2018). Among these approaches, the use of point-dendrometers has been shown to be an effective technique for recording intra-annual tree growth variability and attempts have been made to link radial variations to meteorological conditions by disentangling hydraulic stemdiameter fluctuations and biomass increments (Deslauriers et al, 2007;van der Maaten et al, 2013van der Maaten et al, , 2018Aldea et al, 2018). Although the use of daily stem variation data seems to be promising for understanding the ecology of radial growth on a fine temporal scale, its use on determining (absolute) wood formation phenology is limited, since changes in stem water content can potentially mask signals from actual cellular production (Cuny et al, 2015;Sass-Klaassen, 2015).…”

“…Its cells can be roughly characterized in early and late phloem, according to the formation time (Gričar andČufar, 2008;Prislan et al, 2019b). These processes are linked to irreversible stem enlargement, however since dendrometer readings also integrate reversible stem hydraulic dynamics, these are known to deliver rough estimates of cambial activity and less reliable critical dates like onset and cessation of growth (de Vries et al, 2003;Deslauriers et al, 2007;Solberg et al, 2009;van der Maaten et al, 2018). Therefore, a calibration and comparison with anatomical sections of tissues including cambium and forming wood of the same tree should be performed to securely separate both processes from each other.…”