Christoph Dittmar

Growth variations of Common beech (Fagus sylvatica L.) under different climatic and environmental conditions in Europe—a dendroecological study

Abstract With increased growth potential on the one hand, but on the other hand a high percentage of trees exhibiting visible damages and the apparent regional decline in Common beech (Fagus sylvatica L.) stands in Europe, new questions arise about the sensitivity and resistance of this tree species to current environmental changes. In order to obtain more relevant information about this, 36 beech stands under different climatic and environmental conditions throughout Europe were selected and investigated by dendroecological methods. The variation of tree ring widths of Common beech was found to be a very sensitive indicator, reflecting clearly the signals of environmental influences. A high statistical quality of tree ring chronologies demonstrates a high suitability for dendroecological analysis. The investigation of long-term growth variations results in site-dependent and especially elevation-dependent growth trends. Since 1950, at lower altitude sites in Central Europe mainly increased growth trends are obvious. At higher altitude sites, however, almost all sites show a slightly decreased growth potential during the last decades. It seems that at higher altitudes in Central Europe, environmental changes in the recent past with negative effects on cambial activity are the predominant growth influences. This is also reflected in short-term growth disturbances and growth depressions after 1975 in tree ring series of beech trees growing on higher altitude sites. The investigation of climate–growth relations by different dendroecological methods results in distinct altitude-dependent growth-limiting factors. The comparison of chronologies demonstrates a high resistance of beech at sites where water supply is the main growth controlling factor. Strong disturbances and depressions in radial increment, however, were found at higher altitude sites in Central Europe especially at the end of the 1970s. Comparisons with reactions in preceding years demonstrate an increased sensitivity or an affected ‘ecological fitness’. Site factors modify the intensity of damage symptoms, but cannot be regarded as primary causes. Recent environmental changes may be responsible for the reduced ‘ecological fitness’ of Common beech in higher altitude sites. The spatial and temporal distribution of the detected growth disturbances leads to the assumption that increased tropospheric ozone concentrations are involved in the process of a changed sensitivity and resistance.

Impact of late frost events on radial growth of common beech (Fagus sylvatica L.) in Southern Germany

Phenological, temperature, and tree-ring data were used in order to identify and quantify the impact of late frosts on common beech (Fagus sylvatica L.) at different altitudes in Southern Germany during the last century. For this intention, dendroecological investigations were made upon trees at the Meteorological Observatory Hohenpeißenberg as well as from seven stands in the Bavarian Forest and 17 stands at the northern fringe of the Alps. From these locations, a considerable number of severe growth minima in the tree-ring series could be related to late frost in the days of or immediately after leaf unfolding. The frequency of frost-related growth minima increases with altitude. In individual years, radial growth can be reduced by more than 90% (stand mean) in relation to the average growth of the ten previous years. Hence, late frosts are considered as important ecological events that strongly affect beech vitality and competitiveness especially at high altitudes. Evidence of significant impacts on radial growth by late frosts distinct before leaf unfolding or with temperatures above −3°C was not found. Also, increasing frequency and intensity of late frosts during recent decades were not ascertained. Hence, the recently observed decreased vitality of common beech accompanied by growth depressions especially at high altitude sites in Central Europe cannot be explained as a consequence of late frost damage.

Jahrringbreite von Fichte und Buche in Abhängigkeit von Witterung und Höhenlage

ZusammenfassungJahrringbreiten von je 15 Fichten- und Buchenbeständen unterschiedlicher Höhenlagen in Süddeutschland wurden im Hinblick auf den Zusammenhang zwischen Witterung und Radialzuwachs untersucht. Hierfür kamen drei verschiedene, voneinander unabhängige Verfahren zur Beschreibung von Witterungs-Zuwachs-Beziehungen zur Anwendung: ‚response-function‘-Methode, Einzelfaktoren-und Einzeljahr-Analyse. Die Ergebnisse zeigen für die meisten der Standorte einheitliche und eindeutige Beziehungen zwischen Vegetationszeit-Witterung (Mai bis August) und Jahrringbreite. In tieferen Lagen bis etwa 600 m ü.NN erweist sich in erster Linie das Angebot an Wasser als zuwachslimitierender Faktor. Daran schließt sich ab etwa 600 m bis 800 m ü.NN ein Übergangsbereich an, in dem sich im Mittel zwischen Witterungsverlauf und Zuwachs nur schwache und nicht eindeutig gerichtete Beziehungen erkennen lassen. Von Jahr zu Jahr sehr unterschiedliche Witterungseinflüsse oder auch witterungs-unabhängige Parameter steuern in diesen Höhenbereichen das Wachstum. In den Mittelgebirgen und Alpen — oberhalb von etwa 800 m ü.NN — ergaben sich klare Zusammenhänge zwischen Wärme- und Strahlungsangebot und dem Radialzuwachs von Fichte und Buche. In Hinblick auf die Witterungs-Zuwachs-Beziehungen in höheren Lagen stehen diese Ergebnisse teilweise im Widerspruch zu neueren Arbeiten, die auch dort den Produktionsfaktor Wasser in den Vordergrund stellen. Diese gegensätzlichen Befunde sowie viele noch offene Fragen im Blick auf die komplexen Zusammenhänge zwischen Witterung und Zuwachs von Waldbäumen machen weitere Forschungsarbeit notwendig. Dabei sollten, wie in diesem Beitrag angeregt, verschiedene dendroökologische Verfahren zur Prüfung der Ergebnisse berücksichtigt werden.SummaryRelationships between tree-ring and climate of 15 Norway spruce and 15 European beech stands at different altitudes in southern Germany were investigated. Three different and independent techniques were applied to evaluate growth-weather relationships: response function, single-factor and single-year analysis. For most of the stands results show homogeneous and clear relationships between weather course during the vegetation period (May to August) and year ring width. At low altitudes, up about 600 m a.s.l., the supply of water by precipitation is the main growth limitation factor. Between about 600 and 800 m a.s.l. only weak and no clear relationships between weather course and radial growth were found. Weather events changing from year to year or non-climatic parameters are controlling year ring widths at these altitudes. Above 800 m a.s.l., in mountain regions and the Alps, clear correlations between the supply of temperature and radiation and tree-ring growth of spruce and beech were found. Concerning growth-weather relationships of trees at higher altitudes these results contradict some newer investigations which favour the water supply also in this regions as the main production factor. These contradictory findings and many open questions concerning the complex relationships between weather and growth require more research efforts. As presented in this contribution different kinds of dendroecological methods should be applied to evaluate and prove the results.

Radial Growth of Norway Spruce [Picea abies (L.) Karst.] at the Coulissenhieb Site in Relation to Environmental Conditions and Comparison with Sites in the Fichtelgebirge and Erzgebirge

Changing environmental conditions influence the evolution and growth of trees. With the building of annual increment layers, trees document their reaction to long-term as well as short-term changing growth conditions over a long period of time. Hence, for many years, tree-ring analyses have been used to detect growth and vitality variations in forest ecosystems.