Forests respond differently to changes in climate depending on individual site characteristics and tree status. Site conditions may buffer or boost impacts of heat, drought, and storm events. ...Considering contemporary changes in climate (Christensen et al. 2007), warming may increase forest productivity in those parts of Europe where growth resources like soil water are not limiting (Nabuurs et al. 2002). However, under conditions of limited resource supply and changed disturbance regime, we may expect a reduction of forest productivity and vitality (Lindner et al. 2010). Major climatic impacts on forests include both singular extreme events (changing climate variability) that are difficult to predict in time and location, as well as less obvious gradual changes (changing mean values) (Bolte et al. 2010; Reyer et al. 2013).This study presents an analysis of the diverse aspects of climate change impacts on forests in Europe based on the expert views of local observers. Local expert knowledge provides additional (often overlooked) information on climate change impacts and fills knowledge gaps for less-described European regions. Furthermore, we used expert knowledge to highlight a set of priorities for pro- and reactive forest management, taking into account differences and similarities among regions. Finally, we wanted to define “hot spots” of climate change impacts, i.e., regions, or selected tree species/stands in these regions, which are highly vulnerable and considerably exposed to negative impacts of climate change.
Rising temperature and altered precipitation regimes will lead to severe droughts and concomitant extreme events in the future. Forest ecosystems have shown to be especially prone to climate change. ...In assessing climate change impacts, many studies focus on high altitude or ecological edge populations where a climate signal is supposedly most pronounced. While these studies represent only a fraction of the forest ecosystems throughout Europe, findings on climate sensitivity of lowland core populations remain comparatively underrepresented.
By using tree-ring widths of a large region-wide network of European beech and Scots pine populations along a precipitation gradient in northeastern Germany, we identify main climatic drivers and spatio-temporal patterns in climate sensitivity. Further, we analyze the resistance of tree growth towards drought. Detailed data on soil characteristics was used to interpret climate-growth relationships.
Beech was found to be most sensitive to summer drought during early summer at dry sites, whereas pine displayed highest sensitivity for winter temperature at wet sites. The resistance to extreme drought was lower for beech. By splitting the observation period (1964–2017) into an early and late period, we found non-stationary climate-growth relationships for both study species with beech showing an increase in drought sensitivity and pine in winter temperature sensitivity.
Overall, beech populations seem to be especially endangered by prospective climate changes, whereas climate-growth relationships of pine seem more ambiguous with a possible trade-off between enhanced photosynthetic activity caused by early photosynthesis in late winter and reduced activity due to summer drought.
Masting is a well-known phenomenon in forest science in which trees recurrently produce exceptional high seed amounts throughout their lifespan. Occurring simultaneously across wide regions, masting ...may impact carbon sequestration and carbon cycling of forest ecosystems. To identify masting-induced changes in tree canopies, remote sensing methods may offer a suitable tool, though so far only few studies have used RS methods to investigate the relationship between masting and tree-ring width (TRW). Therefore, we employed a regional network of 19 European beech sites along a precipitation gradient in north-eastern Germany, providing time series of TRW (1961–2017) and categorical masting data (1992–2020). Combined with leaf area index (LAI) from the medium-resolution satellite sensors SPOT-VGT/PROBA-V and MODIS, we assessed the relationship between all three parameters by correlation analysis. Furthermore, we identified common climatic drivers and spatial masting patterns along gradients of water availability. We found negative relationships for both TRW and LAI with masting and a positive correlation for TRW with LAI for SPOT-VGT/PROBA-V data. Contrary, MODIS LAI provided no significant relationships. Water availability did not impact masting occurrence or intensity. The climate correlations showed that masting and TRW are commonly driven by summer climate in June and July, while we found no correlations between climate and LAI. We conclude that medium-resolved SPOT-VGT/PROBA-V LAI is suitable to observe masting but not to estimate TRW. Nonetheless, the results should be thoroughly interpreted in the context of uncertainties of RS measurements and complex interactions of different environmental drivers.
•Day-to-day stem radius variations (SRV) of beech were analyzed at a NE and SW slope.•Responses of SRV to forest meteorological variables were mostly linear.•Beech trees at NE and SW did not differ ...in their response to weather conditions.•Forest meteorological factors were found to have opposing effects at lagged days.
Projected changes in climate highlight the need for a better understanding of the effects of forest meteorological factors on the growth of Central European forests. In this study, we used automatic point dendrometers to investigate day-to-day stem radius variations of 24 European beech trees (Fagus sylvatica L.) in relation to daily forest meteorological conditions. Study trees were located at opposing north-east (NE) and south-west (SW) exposed slopes of a valley in southwestern Germany, and monitored over a six-year period (2001–2006). Seasonal courses of day-to-day stem radius variation (SRV) were analyzed in hierarchical mixed models based on first-order derivatives of cumulative Weibull functions. Responses of SRV to weather conditions were found to be remarkably synchronic within and between the NE and SW aspect. This latter finding suggests that trees at both slopes may have adapted to prevailing environmental conditions. Further, responses were found to be mostly linear within the range of forest meteorological conditions encountered in this study. Highly distinct effects of forest meteorological fluctuations were observed when daily lags were considered. The daily parameters mean air temperature at lag1 (=one day lag), maximum air temperature and soil water content at lag1 were found to explain 59% of the variance in day-to-day stem radius variations. We discuss the complex responses of SRV to lagged and current-day weather variables in relation to stem hydraulics and growth, varying time scales of tree physiological processes, and pre-conditioning of tree water status.
Deciphering the drivers of tree growth is a central aim of dendroecology. In this context, soil conditions may play a crucial role, since they determine the availability of water and nutrients for ...trees. Yet, effects of systematically differing soil conditions on tree growth render a marginally studied topic. In this context, relict charcoal hearths (RCH) – a widespread legacy of anthropogenic charcoal production – render a valuable ‘natural’ experiment to study possible effects of artificially altered soil conditions on tree growth. We hypothesize, that the differing physico-chemical properties of RCH result in differing wood properties if compared to trees growing on unmodified soils. To test this hypothesis, we analyzed tree-growth, wood density, and wood elemental concentrations of Scots pine as well as physico-chemical soil properties. We applied a classic control-treatment design to compare RCH with unmodified soils. Our analyses identified significantly lower above-ground wood production but systematically higher wood elemental concentrations in RCH-trees compared to control trees. Since we could not identify treatment-specific growth patterns, we hypothesize the observed lower above-ground productivity of Scots pine to indicate an increased root-shoot ratio to compensate for a potentially lower plant water availability on RCH-sites. The observed higher wood elemental concentrations likely reflect higher soil elemental concentrations of Fe, Ca, K, and Mn in RCH soils. In conclusion, our study highlights diverse effects of RCH on tree growth and wood properties and strengthens the value of dendro-chemistry to use the tree-ring archive as proxy for soil conditions within a dendro-ecological context.
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•We study the influence of relict charcoal hearths on tree growth and wood properties.•Trees on relict charcoal hearths featured less above ground productivity.•Trees on relict charcoal hearths featured higher wood chemical concentrations.•C-horizons of relict charcoal hearth soils featured higher chemical concentrations.•We discuss how soil properties may affect tree productivity and chemistry.
We analyzed inter-annual variations in ring width and maximumwood density of Norway spruce (Picea abies (L.) Karst.) at different altitudes in Baden-Württemberg, southwestern Germany, to determine ...the climate response of these parameters under contrasting climate conditions. In addition, we compared maximum, average and minimum wood density between sites. Bootstrapped correlation coefficients of ring width and maximum wood density with monthly temperature and precipitation, revealed a different climate sensitivity of both parameters. Ring width showed strong correlations with climate variables in the previous year and in the first half of the growingseason. Further, a negative relationship with summer temperature was observed at the low-altitude sites. Maximum wood density correlated best with temperature during the growing season, whereby strongest correlations were found between September temperature and maximum wood density at the high-altitude sites. Observed differences in maximum, average and minimum wood density are suggested to relate to the local climate; with lower temperature and higher water availability having a negative effect on wood density.
Induced by climate change associated disturbances and further promoted by changes in forest management, the proportion of European beech, a highly competitive climax species, is increasing in Central ...Europe. However, its climatic stability is questioned by the recent loss of vitality. In this regard, the evaluation of seed sources used for reforestation receives great attention. Here, we present a multi-trait evaluation of height, basal area and stem quality assessed over 25 years for 85 provenances grown at three sites in northern, western and eastern Germany. Considerable provenance differentiation exists, explaining 21% (proportion of trees with acceptable stem form) to 45% (basal area) of the variance on single sites and 20 to 39% across sites, while provenance by environment interactions are absent. On the landscape level, this results in distinct patterns with spatially adjacent provenances showing a similar trait expression. These patterns are highly similar for height and basal area but divergent for stem form. They could be directly linked to geographic variables with multivariate regression tree analysis that captured 58% of the phenotypic variation, delineating eleven ‘ecotypes’ shaped by local adaptation. A selection based on two multi-trait indices gives highly concordant results. Particularly, the intermediate elevations of the central highlands in Western Germany host highly suitable provenances. Lower elevation provenances from continental climates in the south-east profit from the transfer to favorable growing conditions. Since the majority of provenances was already exposed to elevated temperatures compared to their origin during the observation period, this study gives a first indication for the potential benefits of assisted migration facing climate change.
dendrometeR: Analyzing the pulse of trees in R van der Maaten, Ernst; van der Maaten-Theunissen, Marieke; Smiljanić, Marko ...
Dendrochronologia,
December 2016, 2016-12-00, Letnik:
40
Journal Article
Recenzirano
Odprti dostop
Dendrometers are measurement devices proven to be useful to analyze tree water relations and growth responses in relation to environmental variability. To analyze dendrometer data, two analytical ...methods prevail: (1) daily approaches that calculate or extract single values per day, and (2) stem-cycle approaches that separate high-resolution dendrometer records into distinct phases of contraction, expansion and stem-radius increment. Especially the stem-cycle approach requires complex algorithms to disentangle cyclic phases. Here, we present an R package, named dendrometeR, that facilitates the analysis of dendrometer data using both analytical methods. By making the package freely available, we make a first step towards comparable and reproducible methods to analyze dendrometer data. The package contains customizable functions to prepare, verify, process and plot dendrometer series, as well as functions that facilitate the analysis of dendrometer data (i.e. daily statistics or extracted phases) in relation to environmental data. The functionality of dendrometeR is illustrated in this note.
To enhance our understanding of forest carbon sequestration, climate change mitigation and drought impact on forest ecosystems, the availability of high-resolution annual forest growth maps based on ...tree-ring width (TRW) would provide a significant advancement to the field. Site-specific characteristics, which can be approximated by high-resolution Earth observation by satellites (EOS), emerge as crucial drivers of forest growth, influencing how climate translates into tree growth. EOS provides information on surface reflectance related to forest characteristics and thus can potentially improve the accuracy of forest growth models based on TRW. Through the modelling of TRW using EOS, climate and topography data, we showed that species-specific models can explain up to 52 % of model variance (Quercus petraea), while combining different species results in relatively poor model performance (R2 = 13 %). The integration of EOS into models based solely on climate and elevation data improved the explained variance by 6 % on average. Leveraging these insights, we successfully generated a map of annual TRW for the year 2021. We employed the area of applicability (AOA) approach to delineate the range in which our models are deemed valid. The calculated AOA for the established forest-type models was 73 % of the study region, indicating robust spatial applicability. Notably, unreliable predictions predominantly occurred in the climate margins of our dataset. In conclusion, our large-scale assessment underscores the efficacy of combining climate, EOS and topographic data to develop robust models for mapping annual TRW. This research not only fills a critical void in the current understanding of forest growth dynamics but also highlights the potential of integrated data sources for comprehensive ecosystem assessments.
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•We combined remote sensing, climate and elevation to model tree-ring width (TRW).•Models' explained variance ranged up to 52 % and was higher for species-specific models.•Including remote sensing data improved the prediction accuracy by 6 % on average.•Satellite-derived vegetation indices yielded strong positive relationships with TRW.•The developed forest-type models were successfully applied to generate a map of TRW.
•The uniformitarian principle is the basis for extrapolating into the past.•The dendro-community uses this principle inconsistently and partially incorrect.•We propose a simple, logical and ...straightforward interpretation.
The uniformitarian principle is one of the most important foundations of all dendro- and paleo-sciences. Without it, no inferences about the past can be made. However, the use of this principle in our community is not consistent and partially incorrect, with the main confusion relating to the understanding of the “uniformitarian principle” as somehow implying a stable relationship between climate and tree growth. To solve this, we look briefly at the history of the term, show how we teach this principle in our textbooks, give some examples of incorrect applications of this principle in the recent literature and close with a simple, logical and straightforward interpretation of this principle to the dendro-community. Applying the principle of aggregate tree growth we show that instable climate-growth relationships and the “no-analogue problem” are not a violation of the uniformitarian principle, but rather reflect our incomplete understanding of tree growth processes. Simply stated: The “uniformitarian principle” is an a priori assumption of spatial and temporal invariance of law’s describing nature’s processes. Applied to the dendro-sciences it means that the principle of aggregate tree growth is valid in time and space.
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