Recent studies projecting future climate change impacts on forests mainly consider either the effects of climate change on productivity or on disturbances. However, productivity and disturbances are ...intrinsically linked because 1) disturbances directly affect forest productivity (e.g. via a reduction in leaf area, growing stock or resource-use efficiency), and 2) disturbance susceptibility is often coupled to a certain development phase of the forest with productivity determining the time a forest is in this specific phase of susceptibility. The objective of this paper is to provide an overview of forest productivity changes in different forest regions in Europe under climate change, and partition these changes into effects induced by climate change alone and by climate change and disturbances. We present projections of climate change impacts on forest productivity from state-of-the-art forest models that dynamically simulate forest productivity and the effects of the main European disturbance agents (fire, storm, insects), driven by the same climate scenario in seven forest case studies along a large climatic gradient throughout Europe. Our study shows that, in most cases, including disturbances in the simulations exaggerate ongoing productivity declines or cancel out productivity gains in response to climate change. In fewer cases, disturbances also increase productivity or buffer climate-change induced productivity losses, e.g. because low severity fires can alleviate resource competition and increase fertilization. Even though our results cannot simply be extrapolated to other types of forests and disturbances, we argue that it is necessary to interpret climate change-induced productivity and disturbance changes jointly to capture the full range of climate change impacts on forests and to plan adaptation measures.
Background： We compare the climate sensitivity of European beech （Fagus sylvatica L.） in two forest nature reserves in northeastern Germany. The one reserve, Schlossberg, is characterized by shallow ...chalk soils, whereas in the other reserve, EIdena, soils are deeper and more developed. Little is known about the drought sensitivity of beech on shallow chalk soils. Methods： We collected increment cores at both research sites and established climate-growth relationships. Inter- tree variability was assessed by employing linear mixed-effect models. Results： We expected to find distinctively higher drought sensitivity at Schlossberg due to limited water availability, but find only marginal differences in growth responses. At both sites, drought is the major climatic factor driving tree growth. Adaptations in tree architecture and an underestimation of the water holding capacity of shallow chalk soils are discussed as possible reasons for not finding more distinct climate responses. In analyzing climate-growth relationships, we specifically focused on growth responses of individual trees but observed only low inter-tree variability at both sites. Evident is a shift in climate response patterns from the first to the second half of the twentieth century with previous-year drought conditions becoming more important than current-year drought. This shift is discussed in relation to a warming trend over that same period, as well as possible trends in masting behavior of beech. Conclusion： The investigated beech trees on the shallow chalk soil are only slightly more drought sensitive than beech trees on the reference site with deeper and more developed soils.
The onset of the growing season in temperate forests is relevant for forest ecology and biogeochemistry and is known to occur earlier with climate change. Variation in tree phenology among individual ...trees of the same stand and species, however, is not well understood. Yet, natural selection acts on this inter-individual variation, which consequently affects the adaptive potential to ongoing environmental changes. Budburst dates of 146 mature individuals of
, the dominant natural forest tree of central Europe, were recorded over 12 years in one forest stand of 1 ha in the Müritz National Park, Germany. The tree-specific location, topographical differences, as well as social status, were measured to explain the inter-individual variation in budburst. Furthermore, inter-individual differences in bud dormancy were quantified. Additional phenology and weather data across Germany from 405 sites over a 25-year period was used to put the insights from the single stand into perspective. Consistent phenological ranking over the years with respect to early and late flushing trees was observed within the single forest stand, with 23 trees consistently flushing 3-6 days earlier and 22 trees consistently flushing 3-10 days later than the median. Trees flushing consistently early varied most in their spring budburst dates and were less dormant than late-flushing trees already in mid-winter. The higher variation in earlier flushing trees was best explained by a slower warming rate during their budburst period in the observed stand as well as across Germany. Likewise, years with a lower warming rate during the budburst period were more variable in budburst dates. The rate of warming during spring time is crucial to accurately project future within-species variation and the resulting adaptive potential in spring phenology of dominant forest tree species.
Climate change is affecting forest ecosystems globally, in particular through warming as well as increases in the frequency and intensity of extreme events. Norway spruce (Picea abies (L.) Karst.) is ...one of the most important coniferous tree species in Europe. In recent extremely dry years in Central Europe, spruce suffered and large dieback has been observed. In parts of Eastern Europe, however, no large-scale decline in spruce has been reported so far, though anticipated changes in climate pose the question how the future of these forests may look like.
To assess the current state of spruce forests in Eastern Europe, we established a tree-ring network consisting of 157 Norway spruce chronologies (from >3000 trees) of different ages distributed along elevational transects in the Eastern Carpathians, Romania. We evaluated early warning signals of climate change-induced stress, i.e. (1) growth decline, (2) increased sensitivity of tree growth (assessed over the statistics first-order autocorrelation and standard deviation), and (3) increased growth synchrony.
A pronounced growth decline was observed over the last two decades, which was strongest in younger stands and at lower elevations. However, growth sensitivity and synchrony did not show consistent patterns, suggesting that forest decline may not be immediately imminent. Overall, our findings highlight an increased vulnerability of spruce in the Eastern Carpathians. With ongoing climate change, spruce dieback may be expected in this part of Europe as well.
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•In the Carpathians, a network of 157 Norway spruce chronologies was established.•Early-warning signals of climate change-induced stress were studied.•Recent growth decline was observed, which was strongest at low elevations.•Growth sensitivity and synchrony did not show consistent patterns.•Overall, our results show an increased vulnerability of Norway spruce in the region.
More frequent and severe droughts have affected forest ecosystems throughout Europe in recent decades. In Central Europe, large-scale dieback of Norway spruce has, for example, been observed, whereas ...Norway spruce decline was so far less widespread in Eastern Europe. To assess the potential future impacts of drought on Norway spruce in the southeastern part of its natural distribution, studies on drought resilience are urgently needed. Here, we use a tree-ring network consisting of more than 3000 trees from 158 managed Norway spruce stands of different ages distributed along elevational gradients in the Eastern Carpathians to assess growth responses to drought. Specifically, we analyzed differences in resilience components (e.g., resistance, recovery, resilience, recovery period) with elevation and tree age, and used the ‘line of full resilience’ concept to comprehensively assess drought resilience. Our results show that Norway spruce at low elevations (<800 m) is characterized by the lowest resistance to drought, though has a high recovery, while at high elevations (>1400 m), a higher resistance is associated with a low recovery. In general, older trees were found to need more time to recover. Resilience decreases with a higher water deficit, suggesting that Norway spruce is at risk in the Carpathians with ongoing climate change, urging the need for adaptative forest management.
•Spruce resilience was assessed using more than 3000 trees in the Carpathians.•Spruce suffers most from drought at low elevations, though it recovers quickly.•Older trees were found to need more time to recover.•Resilience decreases with a higher water deficit, suggesting that spruce is at risk.
Aim of the study: At current, forest management in the Eastern Mediterranean region is largely based on experience rather than on management plans. To support the development of such plans, this ...study develops and compares site index equations for pure even-aged Pinus brutia stands in Syria using base-age invariant techniques that realistically describe dominant height growth.Materials and methods: Data on top height and stand age were obtained in 2008 and 2016 from 80 permanent plots capturing the whole range of variation in site conditions, stand age and stand density. Both the Algebraic Difference Approach (ADA) and the Generalized Algebraic Difference Approach (GADA) were used to fit eight generalized algebraic difference equations in order to identify the one which describes the data best. For this, 61 permanent plots were used for model calibration and 19 plots for validation.Main results: According to both biological plausibility and model accuracy, the so-called Sloboda equation based on the GADA approach showed the best performance.Research highlights: The study provides a solid classification and comparison of Pinus brutia stands growing in the Eastern Mediterranean region and can thus be used to support sustainable forest management planning.Keywords: site index; Generalized Algebraic Difference Approach (GADA); Sloboda equation.
Background
In the German Democratic Republic (GDR), resin tapping in Scots pine (
Pinus sylvestris
L.) forests was a major economic activity, and resin-tapped stands are frequently found up until ...this day. In this study, we investigate how the mechanical damage caused by resin tapping affects the growth and climate sensitivity of Scots pine using a dendroecological approach.
Methods
Tree-ring samples were collected from resin-tapped and non-tapped trees in two forest areas in northeastern Germany, and tree-growth patterns were analyzed. For elucidating effects of resin tapping on the climate sensitivity of pine growth, climate-growth relationships and pointer years were studied.
Results
We observed that resin tapping positively affects tree growth at breast height, likely as wood formation is concentrated on the living part of the bole (i.e. after tapping there is no growth taking place on the tapping face due to the mechanical damage done to the cambium). We observed no differences in the climate sensitivity of tapped and non-tapped trees, nor in the occurrence of extreme growth responses.
Conclusion
Our results highlight that resin extraction is, apart from inflicting mechanical damage, not altering the sensitivity of Scots pine growth to climatic conditions.
The R package pointRes helps to analyze event years, pointer years and components of resilience for tree-ring datasets (e.g., tree-ring width or basal area increment) by offering highly flexible ...calculating and plotting functions. Event and pointer years can be identified using established methods based on (i) normalization in a moving window, and (ii) relative growth change. Besides, the resilience components resistance, recovery, resilience and relative resilience can be examined. The analysis of pointer years and resilience components provides quantitative information on growth responses of trees to extreme events as well as on their ability to retain growth levels prior to disturbance. In the face of climate change, with a projected increase in intensity and frequency of extreme events, such information is highly important. The main focus of pointRes is on dendroecological applications, but the package may be used to analyze patterns in other ecological time series as well.
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.
To study growth responses of trees to extreme events, analyses of so-called ‘pointer years’ are often performed. Thereby, the term pointer year refers to years in which a majority of trees shows ...extraordinary growth responses, like very narrow (or wide) ring widths. A wide variety of methods has been used to analyze pointer years, hampering comparisons between studies. The latter illustrates that there is a strong need to harmonize pointer year detection methods. This review contributes to that by describing and comparing the main methods (and variants thereof) found in the literature for the last two decades, both in a qualitative and quantitative way. We discuss methodological considerations and provide recommendations how to proceed with pointer year detection in future. Given that the individual methods for pointer year detection were found to highlight different aspects of extraordinary growth, the one method cannot completely substitute the other. Hence, we suggest to use multiple methods in a harmonized way to get the deepest insight into the nature of pointer years.
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