CL1.2.2

Tree rings provide an invaluable long-term record for understanding how climate and other drivers shape tree growth and forest productivity. However, conventional tree-ring analysis methods were not designed to simultaneously test effects of climate, tree size, and other drivers on individual growth. This has limited the potential to test ecologically relevant hypotheses on tree growth sensitivity to environmental drivers and their interactions with tree size. Here, we develop and apply a new method to simultaneously model nonlinear effects of primary climate drivers, reconstructed tree diameter at breast height (DBH), and calendar year in generalized least squares models that account for the temporal autocorrelation inherent to each individual tree's growth. We analyze data from 3811 trees representing 40 species at 10 globally distributed sites, showing that precipitation, temperature, DBH, and calendar year have additively, and often interactively, influenced annual growth over the past 120 years. Growth responses were predominantly positive to precipitation (usually over ≥3-month seasonal windows) and negative to temperature (usually maximum temperature, over ≤3-month seasonal windows), with concave-down responses in 63% of relationships. Climate sensitivity commonly varied with DBH (45% of cases tested), with larger trees usually more sensitive. Trends in ring width at small DBH were linked to the light environment under which trees established, but basal area or biomass increments consistently reached maxima at intermediate DBH. Accounting for climate and DBH, growth rate declined over time for 92% of species in secondary or disturbed stands, whereas growth trends were mixed in older forests. These trends were largely attributable to stand dynamics as cohorts and stands age, which remain challenging to disentangle from global change drivers. By providing a parsimonious approach for characterizing multiple interacting drivers of tree growth, our method reveals a more complete picture of the factors influencing growth than has previously been possible.

How to cite: Anderson-Teixeira, K. and the ForestGEO dendrochronology team: Joint effects of climate, tree size, and year on annual tree growth derived from tree-ring records of ten globally distributed forests, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3077, https://doi.org/10.5194/egusphere-egu22-3077, 2022.

Drought legacy effects in radial tree growth have been extensively studied over the last decade and are found to critically influence carbon sequestration in woody biomass. Typically quantified as a deviation from “normal” growth, drought legacy magnitude and statistical significance depend on the definition of expected vs. unexpected growth variability under average conditions – a definition that has received insufficient theoretical validation.

Here, we revisit popular legacy effect analyses using the International Tree-Ring Data Bank (ITRDB) and employ a synthetic data simulation to disentangle four key variables influencing the magnitude of legacy effects. We show that legacy effects i) are mainly influenced by the overall auto-correlation of radial growth time series, ii) depend on climate-growth cross-correlation, iii) are directly proportional to the year-to-year variability of the growth time series, and iv) scale with the chosen extreme event threshold. Our analysis revealed that legacy effects are a direct outcome of the omnipresent biological memory.

We further found that the interpretation of legacy effects following individual drought events at specific sites is challenged by high stochasticity, and show that the commonly perceived stronger legacy effects for conifers are the result of higher auto-correlation compared to deciduous broadleaves. Given that the existing literature has not sufficiently addressed biological memory, we present two pathways to improve future assessment and interpretation of legacy effects. First, we provide a simulation algorithm to a posteriori account for auto-correlated residuals of the initial regression model between growth and climate, i.e. a corrected Null model to determine statistical significance, thereby retrospectively adjusting expectations for “normal” growth variability. The second pathway is to a priori include lagged climate parameters in the regression model. This substantially reduces the magnitude of observed legacy effects and thus challenges us to revisit estimates of drought-induced growth deviations by considering the full spectrum of expected growth behavior. 

How to cite: Klesse, S., Babst, F., Evans, M. E. K., Hurley, A., Pappas, C., and Peters, R. L.: Drought legacy effects in radial tree growth are rarely significant under heightened statistical scrutiny, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3881, https://doi.org/10.5194/egusphere-egu22-3881, 2022.

Intensifying climate change is successively increasing the frequency and intensity of extreme climate events such as droughts. In 2018–2019, Central European forests were hit by two consecutive hotter drought years that were unprecedented in their severity at least in the last 250 years. Such hotter droughts, where drought coincides with a heat wave, may have severe detrimental impacts on forest ecosystems as highlighted by reports of widespread tree defoliation and mortality across Central Europe in 2018–2019. Here, we examine the effect of this unprecedented event on tree growth and physiological stress responses (measured as increase in wood carbon isotope composition, Δδ¹³C) in a Central European floodplain forest ecosystem. We used tree rings of the dominant tree species Quercus robur, Acer pseudoplatanus and Fraxinus excelsior to compare growth responses, Δδ¹³C and drought legacy effects during the consecutive drought years 2018–2019 with effects observed in former single drought years (2003, 2006, 2015). We found that tree growth was, except for F. excelsior, not reduced in 2018 and that drought responses in 2018 were comparable to responses in former single drought years. This indicates that water availability in floodplain forests can partly buffer drought effects and meteorological water deficits. Nonetheless, the 2018 drought – which was the hottest and driest year since the start of records – induced drought legacies in tree growth while former drought years did not. Consistent with this observation, all tree species showed strong decreases in growth and increases in Δδ¹³C in the second hotter drought year 2019. The observed stress responses in 2019 were stronger than in any other examined drought year. We posit that the cumulative effect of two consecutive hotter drought years likely caused this unprecedented stress response across all species. Drought responses were consistent for both drought-stress indicators (growth response and Δδ13C), but the timing and magnitude of responses were species-specific: Q. robur exhibited the overall smallest response, followed by A. pseudoplatanus with the strongest response in F. excelsior. We discuss these species-specific differences in light of the species’ stomatal control (inferred from high-resolution sap flow measurements during drought at our site) and species’ resistance to xylem cavitation. Overall, our findings highlight that consecutive hotter droughts constitute a novel threat to forests, even in floodplain forests with comparably high levels of water supply. These results and similar research may contribute towards understanding and forecasting tree species responses to more frequent hotter droughts under intensifying climate change.

How to cite: Schnabel, F., Purrucker, S., Schmitt, L., Engelmann, R. A., Kahl, A., Richter, R., Seele-Dilbat, C., Skiadaresis, G., and Wirth, C.: Impacts of the 2018-2019 drought: cumulative growth and stress responses in a floodplain forest ecosystem, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6271, https://doi.org/10.5194/egusphere-egu22-6271, 2022.

High-resolution palaeoclimate proxies are fundamental to our understanding of the diverse climatic history of the Australian mainland, particularly given the deficiency in instrumental datasets spanning greater than a century. Annually resolved, tree-ring based proxies play a unique role in addressing limitations in our knowledge of interannual to multi-decadal temperature and hydroclimatic variability prior to the instrumental period. Here we present cross-dated ring-width (RW) and minimum blue-intensity (BI) chronologies spanning 70 years (1929 – 1998) for Podocarpus lawrencei Hook.f., the Australian mainland's only alpine conifer, based on nine full-disk cross-sections from Mount Loch in the Victorian Alps. Correlations with climate variables from observation stations and gridded data reveal a significant positive relationship between RW and mean monthly maximum temperatures in winter throughout central Victoria (r = 0.62, p < 0.001), and a significant negative correlation to winter precipitation (r = -0.51, p < 0.001). We also found significant negative correlations between RW and monthly snow depth data from Spencer Creek in New South Wales (r = -0.60, p < 0.001). Of the assessed BI parameters, delta blue-intensity (ΔBI; the difference between early- and late-wood BI) displayed the greatest sensitivity to climate, with robust spatial correlations with mean October to December maximum and minimum monthly temperatures (r = -0.43, p < 0.001; r = -0.51, p < 0.001) and July precipitation (r = 0.44, p < 0.001), across large areas of northern Victoria. These promising findings highlight the utility of this species for future work. With the very limited availability of suitable long-lived and cross-datable species on the Australian mainland, these results have implications for the significant advancement of palaeoclimate records in southeastern Australia and the potential for improvement in our understanding of past climate in the region.

How to cite: O'Connor, J., Henley, B., Brookhouse, M., and Allen, K.: Piloting novel multi-centennial palaeoclimate records from mainland southeast Australia., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6899, https://doi.org/10.5194/egusphere-egu22-6899, 2022.

Trees are one of the best sources of high-resolution proxy data to understand the past climate. By analyzing Tree Ring Width (TRW) data with climate variables and indicators, we can find main clues, which can help us to encode paleoclimate signals. Nowadays, scientists try to model TRW data with various climate data versus reconstructing the mentioned data for an extended period through different statistical methods. One of the newest methods is AI (Artificial Intelligence). This study aimed to model TRW data with the most effective climate variables by comparing the statistical methods vs. the AI method. First, seven climate variables were gathered from the nearest synoptic station (Sokcho) to the TRW site (Whachae Peak-Sorak), in northeast South Korea, during 1901–1998. The climate variables include maximum temperature (Tmax), minimum temperature (Tmin), mean temperature (Tm), diurnal temperature range (DTR = Tmax – Tmin) (°C), precipitation (Pr) (mm), and vapor pressure (VP) (hPa). The in-situ data were applied to correct the Climate Reach Unit (CRU, Version 4.03). Moreover, we have checked two meteorological drought indices, namely the Palmer drought index (PDSI) and standardized precipitation index (SPI). We applied two regression methods (namely multiple linear regression (MLR) and stepwise regression (SR)) and one AI (Nonlinear autoregressive with exogenous input (NARX)) method. In the first step of analyzing data, we did not see any specific significant results for the relationship between drought effects and TRW data in the case study. Then in the second step, modeling continued with the climate variables. Finally, the results demonstrated that among the three used methods, the NARX method achieved the best outcomes, as MLR with r = 0.44 (p < 0.003); SR with r = 0.27 in p < 0.001; and the NARX model was the best outcomes with r = 0.78. This study revealed that regression methods were not strong enough to reconstruct TRW data. Whereas, by noticeable results, the AI method has obtained the best performance.    

How to cite: Salehnia, N. and Ahn, J.: Applying artificial intelligence in modeling the relationship of tree ring growth index with different climate variables, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2212, https://doi.org/10.5194/egusphere-egu22-2212, 2022.

Rapid temperature and vapor pressure deficit (VPD) increase along with precipitation decrease over the past decades lead to massive wildfires and permafrost degradation in boreal forests. Conifer trees growing in subarctic regions are highly sensitive to these climatic changes due to their location at the high latitudes, where air temperature is the limiting factor, but also water relations have a strong impact on tree growth.

In this study, we aimed (i) to assess the usability of local vs. gridded climate data; (ii) to reveal how conifer trees capture temperature and moisture signals based on the local weather station data vs. gridded data from the two Siberian sites in northeastern Yakutia and eastern Taimyr, and one site from northwestern Canada in Mackenzie Delta; (iii) to perform trend analysis of climatic data and δ¹⁸O in tree-ring cellulose; and (iv) to carry out spatial correlation analysis of oxygen isotope patterns and determine the distribution of climatic signal over broad geographical scales in the Siberian and Canadian subarctic.

Comparative analysis of the local and gridded climatic data (air temperature, precipitation and VPD) for the three study sites showed that mainly temperatures are highly correlated between each other. Subarctic trees grow in a temperature-limited environment; therefore, the large spatial coherence of temperature signals is not surprising. Conversely, insignificant correlations between local and gridded for precipitation and rather low correlations for VPD is attributed to the more heterogeneous nature of moisture variables at larger spatial scales. Therefore, analyzing moisture changes in the subarctic using local weather station data is advantageous compared to gridded data.

Trend analysis of the climate data showed that drastic changes in climate variability occurred from the 1980s in the investigated subarctic regions and were even more pronounced from 2000 to 2021. Recent warming and development of drought conditions were stronger in the Canadian subarctic than the Siberian subarctic sites. Drastic precipitation changes, temperature and VPD increase mainly occurred during winter, spring and autumn in the studied subarctic regions. New updated stable isotope chronologies from remote subarctic regions allowed us to accurately reconstruct moisture changes using precipitation and VPD data from the local weather stations while reconstructing air temperature using gridded data.

This research was funded by the Russian Science Foundation (RSF) grant number 21-17-00006.

How to cite: Churakova (Sidorova), O. V., Zharkov, M. S., Fonti, M. V., Trushkina, T. V., Barinov, V. V., Taynik, A. V., Porter, T. J., Kirdyanov, A. V., Arzac, A., and Saurer, M.: Tree-ring oxygen isotope patterns from Siberian and Canadian subarctic to test usability of local versus gridded climate data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8756, https://doi.org/10.5194/egusphere-egu22-8756, 2022.

Stable isotope analyses (δ¹⁸O, δ²H) combined with the tree-ring dating have enormous potential for tracing freshwater resource availability under changing climate and in the context of the impacts of other human activities. This study focusses on the isotopic composition of tree-rings in combination with an anatomical analysis of the European Larch (Larix Decidua) species from different upstream and downstream sites along the Turtmänna river in south-western Switzerland. The results show distinctive patterns of year-to-year tree-ring growth from their constructed chronology dated back to 1851 (i.e. a 170-year record). A trend of a decreasing growth was noted over the last two decades. Decreasing growth was correlated (r = 0.50) with a decrease in precipitation and an increase in temperature (r = 0.30) during the growing season (between June and October) of previous and current years. The isotopic analysis shows a depletion in ¹⁸O in the trees fed by glacial meltwater close to the river as compared to the trees fed by precipitation distal to the river. Given the changes in climate, trees closer to the river are becoming more dependent on river-derived water, which in turn is sourced from melting glaciers. This hence has important consequences for the hydropower generation and water availability.

How to cite: Islam, N., Vennemann, T., and Lane, S. N.: Use of stable isotope signals from tree rings as proxy for tracing the combined effects of climate change and hydropower on glacier-derived water resources in the Turtmänna river catchment, Switzerland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5873, https://doi.org/10.5194/egusphere-egu22-5873, 2022.

While carbon (δ¹³C) and oxygen (δ¹⁸O) isotopes in tree-ring cellulose are widely used as climatic and physiological proxy in dendro sciences, the processes that are affecting the fractionation of non-exchangeable hydrogen (δ²H) isotopes and shaping the tree-ring δ²H profile are barely understood and thus not widely applied yet.

To establish a first comprehensive comparison of the photosynthetic and post-photosynthetic ²H-fractionation of northern-hemisphere trees, we sampled leaves and twigs of 152 trees representing 73 species, 48 genus, 19 families and 12 orders containing both evergreen and deciduous angio- and gymnosperms in a common garden, as well as diurnal cycles (6 species from 6 families) of leaf sugar. We extracted leaf water and sugar, as well as twig water and the current year twig xylem cellulose for δ²H analysis. Leaf sugar and twig cellulose were measured with a newly established hot water vapour equilibration method.

Our findings show a wide variation in ²H-fractionation between species growing at a common site. The measured δ²H values ranged from -63.5 to –33.4‰ for xylem water, between -22.3 and +28.5‰ for leaf water, between -160.9 and +12.6‰ for leaf sugar and between -79.1 and +6.9‰ for twig cellulose. The biological fractionation between leaf water and leaf sugar ranged between -169.6 and +24.2‰ and between leaf sugar and current year twig cellulose from -34.6 to +116.8‰. In general, sugar and cellulose of gymnosperms were significantly more ²H depleted than those of angiosperm species, with no impact of the leaf shedding behaviour to the measured δ²H values. We observed significant differences in the δ²H values between different orders and families, but not between genus and species within a family or genus, respectively. This pattern indicates that the photosynthetic and post-photosynthetic ²H-fractionation are based on conservative metabolic reactions with a generally low mutation rate.

Additionally, the results from our diurnal sampling of leaf sugar are showing first evidence for a dynamic and species-specific nature of the photosynthetic ²H-fractionation, which is in contrast to current models, which are assuming the same constant ²H-fractionation processes for all plant species.

We conclude that the here presented results will help to improve our understanding of the mechanisms influencing the δ²H values of leaf sugar and tree-ring cellulose and thus enabling the scientific community to use δ²H in tree-ring cellulose as the third isotope-proxy for dendrochronological studies.

How to cite: Schuler, P., Vitali, V., Saurer, M., Gessler, A., Buchmann, N., and Lehmann, M.: The phylogenetic impact on photosynthetic and post-photosynthetic hydrogen isotope fractionation in 73 tree species, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5772, https://doi.org/10.5194/egusphere-egu22-5772, 2022.

Stable hydrogen and carbon isotope ratios of wood lignin methoxy groups (δ¹³C_LM and δ²H_LM values) have been shown to be reliable proxies of past temperature variability. Recent studies revealed δ²H_LM values even work in temperate environments where classical tree-ring width and maximum latewood density data are less skilful. In this presentation, we report 100 years of annually resolved δ¹³C_LM values of four beech trees (Fagus sylvatica) from a temperate site near Hohenpeißenberg in southern Germany. The series are compared with regional to continental scale climate observations to assess their potential for paleoclimate reconstruction. The δ¹³C_LM values were corrected for both the Suess effect to mitigate the effect of decreasing δ¹³C in atmospheric CO₂ and the physiological tree response to increasing atmospheric CO₂ concentrations using different factors for possible changes in discrimination. The calibration of δ¹³C_LM chronologies against regional instrumental data reveals highest temperature sensitivity with mean summer, annual, and previous-year September to current-year August temperatures.

We additionally compared the new δ¹³C_LM chronology with the previously produced δ²H_LM series of the same trees to evaluate the additional gain of assessing past climate variability using a dual-isotope approach. The δ²H_LM values predominantly reflect large-scale temperatures since highest correlations were found with western European temperatures. Weak and mainly non-significant correlations were found between precipitation and both isotopic chronologies (δ¹³C_LM and δ²H_LM values). Our findings described for the first time the great potential of using δ¹³C_LM values from temperate, low elevation environments as a proxy for local temperatures, whereas the combination of both proxies supports the reconstruction of temperature variations at different spatial and temporal scales.

How to cite: Wieland, A., Greule, M., Roemer, P., Esper, J., and Keppler, F.: Climate signals in stable carbon and hydrogen isotopes of lignin methoxy groups: assessing the potential for temperature reconstructions at different spatial and temporal scales, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3369, https://doi.org/10.5194/egusphere-egu22-3369, 2022.

Stable carbon (δ¹³C_c) and oxygen (δ¹⁸O_c)isotopes measured in tree-ring cellulose, together with tree-ring width (TRW), have been used extensively to investigate the effects of past climatic conditions on tree growth. By contrast, the information recorded by the third major chemical component of tree-ring cellulose, the non-exchangeable carbon-bound hydrogen, has been explored far less due to methodological drawbacks and lack of understanding of ²H-specific fractionations. In this first Europe-wide assessment we investigate the signals stored in the hydrogen isotope ratios in tree-ring cellulose (δ²H_c), from a unique collection of 100-years records, from two major genera (Pinus and Quercus) across 17 sites (36°N to 68°N).

The climate correlation analyses showed weak climate signals in the δ²H_c high-frequency chronologies, compared to those recorded by δ¹³C_c and δ¹⁸O_c, but similar to the TRW ones. The δ²H_c climate signal strength varied across the continent and was stronger and more consistent for Pinus than for Quercus. The δ²H_c inter-annual variability was strongly site-specific. Focusing on the effect of extreme climatic conditions during years with extremely dry summers, we observed a significant ²H-enrichment in tree-ring cellulose for both genera. Our findings clearly indicate that δ²H_c registers information about hydrology and climate, but it also records non-climatic signals such as physiological mechanisms associated with carbohydrates storage remobilization ²H-specific fractionations and growth.

To disentangle the climatic and non-climatic signals in δ²H_c, we investigated its relationships with δ¹⁸O_c and TRW. We found significant relationships negative between δ²H_c and TRW at 7 sites and positive between δ²H_c and δ¹⁸O_c at 10 sites, while the rest of the sites did not show any significant relationships. The agreement with the TRW chronologies confirms the relationship between growth and δ²H_c, while the divergencefrom δ¹⁸O suggests a loss of the hydrological signal in δ²H_c. These highlights, once again,a stronger physiological component in the δ²H signature independent from climate. Advancements in the understanding of ²H-fractionations and their relationships with climate, physiology, and species-specific traits are therefore needed to improve the mechanistic modeling and interpretation accuracy of δ²H_c in plant physiology and paleoclimatology. Such advancements could lead to new insights into trees’ carbon allocation mechanisms, and responses to abiotic and biotic stressors.

How to cite: Vitali, V., Martínez-Sancho, E., Treydte, K., Andreu-Hayles, L., Dorado-Liñán, I., Gutiérrez, E., Helle, G., Leuenberger, M., Loader, N. J., Rinne-Garmston, T. K., Schleser, G., Allen, S., Waterhouse, J., Saurer, M., and Lehmann, M.: The unknown third - exploring the climatic and non-climatic signals of hydrogen isotopes in tree-ring cellulose across Europe, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-673, https://doi.org/10.5194/egusphere-egu22-673, 2022.

Abstract:

As a widespread species, sessile oak (Quercus petraea) populations occupy a wide range of ecological conditions with different local selection pressures, especially different drought exposure, which would have favoured different locally adapted populations. Water-use efficiency (WUE), which is defined at the tree level as the ratio between the biomass produced and the quantity of water transpired during the same period of time, is an interesting candidate trait for adaptation to drought. Six hundred trees from sixteen different provenances planted in 1993 in a common garden in the North-Eastern of France were harvested during the 2014-2015 winter. Intrinsic WUE (WUE_i), estimated from carbon isotope composition (δ¹³C) measurements of tree-rings, was compared among and within provenances for three contrasted years: (i) 2000, a wet year; (ii) 2003, a severely dry year; (iii) and 2005, a moderately dry year. The main purpose was to assess the drought-adaptive character of WUE_i for sessile oak trees. For this, (i) the adaptive character of WUE_i was evaluated by relating population mean WUE_i to the mean pedoclimatic conditions of their provenance sites. (ii) The phenotypic plasticity of WUE_i to drought was evaluated by comparing  the values observed in 2003 and 2005 to those of  2000 ; this plasticity was also related to the mean pedoclimatic conditions of their provenance sites. (iii) The contribution of WUE_i to tree and population fitness was assessed from the relationship between WUE_i and tree growth. Significant differences in δ¹³C (thus WUE_i) were found among populations. However, no linear relationship was established between mean population δ¹³C and the mean pedoclimatic conditions of the provenance sites. Based on these results observed on juvenile sessile oak trees in the relatively wet conditions of the common garden, no local adaptation in terms of WUEi was detected. An increase in drought intensity resulted in an increase in population WUE_i and all provenances displayed a similar plasticity of WUE_i to drought, suggesting no among population diversity for drought responses. A significant correlation between WUE_i and tree growth was detected only during the wet year, when populations with a higher WUE_i also had a higher growth index. Moreover, a much larger variability in WUE_i was demonstrated within populations (2–4‰) than among-population (0.6‰).

Key words : Climate change, assisted migration, local adaptation, water-use efficiency, fitness, diversity

How to cite: Rabarijaona, A., Ponton, S., Bert, D., Ducousso, A., Richard, B., Levillain, J., and Brendel, O.: Among-provenance diversity and phenotypic plasticity of water-use efficiency in sessile oak populations growing in a mesic common garden., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7275, https://doi.org/10.5194/egusphere-egu22-7275, 2022.

Large earthquakes can increase the amount of water feeding stream flows, raise groundwater levels, and thus grant plant roots more access to water in water-limited environments. Here, we quantify growth and photosynthetic responses of Pinus radiata plantations to the Maule Mw 8.8 earthquake in geometrically simple headwater catchments of Chile's Coastal Range. To this end, we combine high-resolution wood anatomic (lumen area) and biogeochemical (δ¹³C of wood cellulose) proxies of daily to weekly tree growth sampled from trees on valley bottoms and close to ridge lines. We find that, immediately after the earthquake, at least two out of six tree trees on the valley floor had enlarged lumen area and lowered δ¹³C, while trees along the hillslope ridge had a reverse trend. Our findings favor a control of soil water on this response, largely consistent with models that predict how enhanced postseismic vertical soil permeability causes groundwater levels to rise on valley floors, but fall along the ridges. Statistical analysis with non-parametric boosted regression trees reveals that streamflow discharge gained importance for photosynthetic activity on the ridges, but lost importance on the valley floor after the earthquake. We conclude that earthquakes may stimulate ecohydrological conditions favoring tree growth over days to weeks by triggering stomatal opening. The weak and short-lived signals that we identified, however, imply that such responses are only valid under water-limited, rather than energy-limited tree, growth. Hence, dendrochronological studies targeted at annual resolution may overlook some earthquake effects on tree vitality.

How to cite: Mohr, C., Manga, M., Helle, G., Heinrich, I., Giese, L., and Korup, O.: Trees Talk Tremor—Wood Anatomy and δ13C Content Reveal Contrasting Tree-Growth Responses to Earthquakes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2223, https://doi.org/10.5194/egusphere-egu22-2223, 2022.

Radial growth, wood density and climate-growth relationship of four Douglas fir provenances were analysed separately for the juvenile and the adult phase. Two pairs of provenances were selected from an existing IUFRO provenance trial planted in 1971 based on their diameter at breast height and vitality. Increment cores were extracted from individual trees, on which we measured tree-ring widths (RW), earlywood widths (EWW) and latewood widths (LWW). Wood density was assessed in standing trees using resistance drilling. The climate-growth correlations were calculated between provenance chronologies of RW, EWW, LWW and latewood share, and day-wise aggregated Standardised Precipitation-Evapotranspiration Index (SPEI). We calculated the accumulated drought effects by aggregating climatic water deficits into a log-logistic probability distribution to obtain the SPEI index series of different seasons, starting from three weeks to nine months, including the effect of previous growing season. In all provenances, RW, and consequently EWW and LWW, were wider in juvenile period than in adult period. Share of latewood was in all cases higher in juvenile wood then in mature wood. All four provenances have similar wood density in both analysed growth phases. The general effect of wet conditions in current growing season was positive, indicating that Douglass fir’s radial growth was favoured in moist years, and reduced in dry years. The significant positive effect of SPEI on LW was observed also at the beginning of previous growing season. Our analysis showed that when selecting the most promising provenance for planting, it needs to be considered that growth rate may change from juvenile to adult period. Only by combining climate-growth analysis with measurements of external tree features we can compare and assess the suitability of certain provenances for planting in current and future climate.

How to cite: Krajnc, L., Hafner, P., Jevšenak, J., Gričar, J., and Brus, R.: Tree rings, wood density and climate-growth relationships of four Douglas fir provenances in sub-Mediterranean Slovenia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9627, https://doi.org/10.5194/egusphere-egu22-9627, 2022.