Tree-ring chronology derived from ring widths of the alpine dwarf shrub Empetrum hermaphroditum in the Norwegian mountains

Annette Bär

Department of Geography, University of Bonn, Germany, Department of Biology and Environmental Sciences, University of Oldenburg, Germany

Attempts to derive growth ring chronologies from dwarf shrubs have reveived increasing attention during the last years. Earlier dendroecological analyses of dwarf shrubs were mainly restricted to age determination and descriptions of wood anatomical features. However, efforts to crossdate ring width-patterns failed so far. Thus, successful dwarf shrub growth-environment correlations nowadays avails other parameters than ring width such as annual shoot elongations, flower buds and leaf production.
The crucial point for retrospective growth studies with dwarf shrubs is the correct dating of growth increments to calendar years. Cross-dating has not been successful due to difficulties with (a) the visibility and measurability of annual rings due to their size and distinctiveness, (b) the occurrence of many discontinuous rings due to the asymmetric geometry of dwarf shrub stems, (c) high internal variability within individuals and (d) little knowledge about plant physiology related to annual growth increments in comparison to trees. We overcame these difficulties and succeeded in building an 80 years long chronology of Empetrum hermaphroditum from individuals growing in the middle alpine belt in the continental part of the Norwegian Scandes.
The determination of annual increment areas of each growth ring showed that the asymmetric geometry and occurrence of discontinuous rings within one cross section hardly influenced ring width curve synchronicity. However, synchronization solely based on one single stem section per plant failed due to high internal variability of growth rings within one individual and due to the occurrence of partly missing rings. Thus, three representative plants of each site were analyzed by serial sectioning to derive estimations of internal variability of growth ring formation and to detect partly missing rings. By visual comparison of different stem sections, missing rings could be located exactly in the highly replicated ring width curves. Mean curves of every individual analyzed by serial sectioning served as a reference for other individuals from the same habitat. Nevertheless, some uncertainties about the amount of missing rings in some dwarf shrub individuals remained. These completely missing rings in the Empetrum hermaphroditum samples could be located by the help of a chronology from Betula pubescens growing at the local tree line. Furthermore, first estimations of climate-growth relationships for Empetrum hermaphroditum in the middle alpine belt are presented.

Finding best regression approach for description of climate-growth relation­ships by floating time spans of varying width

Wolfgang Beck

Federal Research Centre for Forestry and Forest Poducts; Institute for Forest Ecology and Forest Inventory, Eberswalde

 Mathematical description of the climate-growth-system (FRITTS, 1976) is a central topic of tree ring research. Especially against the background of changing climate the quantified knowledge about the effects of climatic elements on tree growth is of outstanding importance.
Up to now all approaches use monthly values of climatic variables (temperature, precipitation, combinations of both) or aggregations of these variables within a time span which is thought to be important according to the experience of the author. Any method of data pooling seems to be reasonable at first because climatic data exist at least in daily resolution. Otherwise the flood of data would be unmanageable.
The approach chosen here does not set monthly limits. The only distinction drawn here is between vegetation period (April till October) and dormant period (December till March). Inside these time spans (vegetation period and dormant period) floating time-windows of different width (21 days till 183 days during summer; 21 days till 84 days during winter) are used to aggregate balances of temperature and of precipitation in relation to the averaged values of the period from 1951 to 2003.
All possible variants (about 20 thousands per chronology) according to position and width of the floating time span are tested within multiple regressions by a special computer program. The optimal time span is found if both coefficient of determination and coefficient of “Gleichläufigkeit” between time series of tree ring index and time series of modelled values of tree ring index arrived maximum. Simultaneously the size of sensitivity of the original time series should nearly be arrived by the modelled time series.
In this way the most important time spans related to tree growth inside of the year are found and summarized to a full regression model. After this, model-reduction is carried out by backward selection strategy (t-test).
The result of the whole procedure consist of reliable mathematical descriptions of how climate acts on tree growth. The regression models express the majority of variance (66% to 90%) and reflect the properties of original index series by high degrees of “Gleichläufigkeit” and sensitivity of the modelled series.
By using this method it seems to be feasible to acquire the knowledge base which is necessary as decision support for future forest tree species choice by silviculture.

Answer to the climatic signal in the dependence on site type in spruce stands of Borecka Primeval Forests

Szymon Bijak

Department of Dendrometry and Forest Productivity, Faculty of Forestry, Warsaw University of Agriculture

The aim of the study was to determine the reaction of spruce trees for climate conditions depending on the different habitat type.
Increment cores were taken from three, spruce-dominated stands located in Borecka Primeval Forests, which is considered as one of the least polluted areas in Poland. The stands represent a mixed-deciduous forest habitat type and differ with moisture level.
Tree-ring chronologies ranging from 1846 to 2005 were built for each moisture class and for the whole area separately using available computer programs (ARSTAN, ZGODA, DENDRO). Relationships between meteorological conditions and width of the annual increment ring were examined for temperature, precipitation and synthetic indices describing thermal and pluvial conditions. Analysis was based on the ‘response function’ procedure (program RESPO) and on pointer years which were determined with ‘normalisation in a moving window’ method.

Niels Bleicher

Römisch-Germanisches Zentralmuseum Mainz, Ernst-Ludwig-Platz 2, D–55116 Mainz, Germany

In the Federsee-basin near Ulm in southern Germany several settlements from the late neolithic (ca. 3300 – 2900 BC) have been found in a peat-bog. Due to the lack of oxygen in the peat organic matter and especially wood has been preserved. The wooden remains of the architecture have been investigated dendrochronologically. In this presentation some aspects and examples of the current analyses will be given as well as their implications for archaeological studies.
Archaeological wood does not only provide us with an absolute timescale but has the potential to give information on settlement-dynamics, stone-age economy and ecology. The analysis of the settlement-dynamics can give better estimates of settlement-density, because it is often impossible to tell by archaeological means alone whether two settlements are synchronous, but there are also further indications on social organisation that can be inferred from tree-ring data. The underlying question in terms of economy and ecology is how the use of wood was organized: which aspects of the economical activities made use of wood, how were they organized and how did this influence the local ecology? Did shortages in wood-supply already exist in the stone-age?
The material to answer these questions consisted nearly completely of stems with a diameter between 5 and 15 cm. Few material was larger due to human activities and selection for technical purposes. The species that were used for the houses and trackways were mainly Ash (Fraxinus exc.), Beech (Fagus sylvatica), Alder (Alnus spec.), and several other less important deciduous species. Thus the measurements were extremely difficult due to missing rings, short sequences and very heterogeneous curves because of the distorting effects applying to understory-growth. Furthermore the preservation was sometimes a problem. Great care had to be taken in the building of the chronologies. Since the reference-chronologies consisted of oak and material that has been collected about 100km further to the south some of the dating had to be accomplished by wiggle-matching.
To overcome all these difficulties a thorough dendrotypological analysis was applied and using archaeological data as indicators for relative dating it was even possible to achieve the heteroconnection, which means to cross-date mean-curves of different species.
It can be shown that there existed different concepts of the use of forests. These differences comprise the used species, their age and shape at the time of felling and the rhythms of felling-activity. Corresponding to this there also existed different settlement-types and planning-depths. Within a small regional frame the archaeodendrological analysis revealed different economical strategies. It was also possible to investigate a complex stratigraphy at Alleshausen-Grundwiesen. The rhythms and organisation of forest-use were not only locally but also regionally different. This leads to the question how the local ecology and climate influenced cultural behaviour.

Dendro-ecological reconstruction of a Late-Glacial pine forest in Reichwalde, E-Germany.

Ilse Boeren, Hans-Peter Stika, Maria Knipping, Michael Friedrich, Manfred Küppers

Inst. für Botanik (210), Universität Hohenheim, 70593 Stuttgart.

A vast and well preserved Late-Glacial pine-birch forest has been excavated in a lignite mine in Reichwalde. The advantageous circumstances for the preservation of organic material (inundation and peat-formation) provided more than 1500 subfossil trees “in situ”. They cover a period of about 800 years in the Bølling-Allerød Interstadial (14100–13300 yrs BP). Additionally, information about Late-Glacial vegetation development is given by peat sediments, prior and subsequent to the preserved forest. The dendrochronological dating of stratified pines makes it possible to precisely date the sediment, to directly connect the trees with the bog stratigraphy and thus to compare the results of the dendro-ecological investigations to the pollen and botanical macro-remains analysis. In this way, bio- and chronostratigraphy can be connected.
The fact that most of the trees were found “in situ”, allowed us to reconstruct the stand structure of great parts of the forest, over the different generation phases. This revealed that most stands have had a rather open structure and that the populations existed out of trees of different age.
There is a great difference between the tree-ring parameters in the older part (first 350 yrs) and those in the younger part (last 450 yrs) of the chronology. In the first part the rings are wider and the trees died younger than in the second part. The tree-ring series are more sensitive, but there are less pointer years in the chronology. The Mean Fire Return Interval is about ten times shorter and much more charred botanical material is found in sediments from this time. All these features indicate that in the earlier Allerød, the trees were more influenced by environmental factors than by climate and that in the later Allerød, the climate must have become more interfering with tree growth. This can also be confirmed by the better correlation of the Reichwalde chronology with the northern and southern Germany chronologies in the younger 400 years. This switch in character of the series coincides with a presumptive large-scale water-level increase, which made it impossible for trees to grow on the greater part of the bog. The only trees which are younger than that event have been standing on a small higher-scale part in the north. Pollen and macro-remains confirm a change in hydrology at that time.
Using precisely dated fire scars on the trees, we composed an 800 year fire chronology. This chronology, as well as the age structure of the forest, suggest that fires were a dominant ecological factor in the forest. The severity of the fires has probably not been strong, since most of the trees have survived many fires; the frequency, on the contrary, was very high. This could be confirmed by the results of the palaeobotanic investigations: bushes were rarely found, the undergrowth was dominated by sedges, grasses and other grass-like vegetation.

Calibration of Radiocarbon dates

Mathieu Boudin, Mark Van Strydonck

Royal Institute for Cultural Heritage, Brussels, Belgium.

Calibration of a radiocarbon date is necessary to link the radiocarbon time scale to the calendar time scale. Calibration curves are available in the time range 0 - 26,000 BP. The younger part of this curve (0-12.4 cal ka BP) is established by radiocarbon dating of dendrochronologically established master curves. Tests have shown that there is a small offset between the Northern and Southern hemisphere. Changes in the production rate of atmospheric 14C results in periods of higher and lower precision (wiggles).
Radiocarbon can be a tool in dendrochronological studies: (1)An absolute age can be given to a floating tree ring curve, (2)Wiggle matching can give much more precise dates, (3) Calibration of post-bomb 14C samples can provide calendar dates of post 1950 trees dated by radiocarbon.
The most common tools available to the user are the OXCAL program and the CALIBOMB program available on the internet. Also other programs are available (CALIB, BCAL, CALPAL, WINCAL) on the internet. However, one has to be very alert in using the CALIBOMB program because of an error in the program.

Tree growth and climate in the Tatra Mountains

Ulf Büntgen (1), David Frank (1), Ryszrad J. Kaczka (2), Anne Verstege (1), Tomasz Zwijacz-Kozica (3) and Jan Esper (1)

(1) Swiss Federal Research Institute WSL, Zürcherstrasse 111, 8903 Birmensdorf, Switzerland
(2) Faculty of Earth Science, University of Silesia, 60 Bedzinska 50, 41-200 Sosnowiec, Poland
(3) Tatra National Park, Chalubinskiego42a, 34-500 Zakopane, Poland

We aggregate 24 tree-ring width and 4 maximum latewood density chronologies from the greater Tatra region (Poland/Slovakia). The network comprises 1,183 tree-ring width and 153 density measurement series, and considers four conifer species (Picea Abies, Larix decidua, Abies alba, and Pinus mugo) from elevations between 800-1,550 m asl. Individual spline detrending is used to retain annual to multi-decadal scale information from the data. 20th century temperature and precipitation data from 16 grid-boxes covering the 48-50°N and 18-19°E region are utilized for comparison. The network is analyzed to assess growth/climate response as a function of species, elevation, parameter, frequency, and site-ecology. Twenty ring width chronologies correlate significantly with June-July temperatures, while the density chronologies reveal strongest response to the wider April-September season. Increasing precipitation response with decreasing elevation is observed. Climatic effects of the previous year are generally insignificant, while site elevation and frequency are evident. Correlations between summer temperatures and the annual growth rates of Larix decidua are lower than for Picea abies, although cyclic defoliation patterns of larch budmoth outbreaks are not distinguished. Principal component analysis elucidates five dominant eigenvectors from the network. The first principle component contains highest loadings from 12 Picea abies ring width chronologies and explains 42% of the network’s variance. The mean of these chronologies correlates at 0.62 (p<0.001) with June-July temperatures, while the mean of the three density chronologies that load most strongly on the second principle component, correlates at 0.69 with April-September temperatures (1901-2002). These mean chronologies allow for the robust estimation of June-July (1661-2004) and April-September (1709-2004) temperatures, respectively. Regional- to continental-scale network analyses from the Alps and Central Europe support the dominant role of homogeneous warm season temperatures on high-elevation tree-growth. Our findings are valid for any revised climatic reconstruction, and long-term estimation of forest net primary productivity in the greater Tatra region.

Threshold of land-use abandonment controls the rate of tree regeneration and forest dynamics in a Mediterranean mountain ( Provence, France)

Sandrine Chauchard (1,2), Christopher Carcaillet (1), Frédéric Guibal (2)

(1) Centre de Bio-Archéologie et d’Ecologie (UMR 5059 CNRS), Institut de Botanique, 163 rue Broussonet, 34090 Montpellier, FRANCE
(2) Institut Méditerranéen d’Ecologie et de Paléoécologie (UMR 6116 CNRS), Bâtiment Villemin, Domaine du Petit Arbois, Avenue Philibert, BP 80, 13545 Aix en Provence, FRANCE

Mediterranean ecosystems are impacted for millenniums by human practices such as permanent agricultural and pastoral activities. Since the end of the 19 th century, the traditional land-use abandonment has lead to shrubland and forest expansion, especially in mountain areas. Here, we analyze a mountain forest dynamics by dendrochronology. The approach includes analysis of land-use from archival documents crossed with tree-ring analysis to investigate the origin, establishment and development of forest following the chronology of land-use abandonment. Forest structure and dynamics are investigated with respect to the local agricultural history and former land-uses. Tree colonization started in the 1890s with Scots pine (Pinus sylvestris) regenerating quickly after abandonment. The net rate of recruitment increased during the 1930s when pasture by sheep kept dropping. Beech (Fagus sylvatica) and fir (Abies alba) have been regenerating in the understorey of pines since the 1960s. Regeneration appears controlled by a threshold of grazing pressure. However the timing of forest colonization differs according to the former type of land-use: colonization began in pastures then in ploughed areas. In a Mediterranean mountain ecosystem, agricultural history and the rhythm of land-use abandonment are a significant driving force explaining forest dynamics. Knowledge of the agricultural history and former land-use is critical to understand and predict forest dynamics in the Mediterranean mountain.

The origin of large oak clusters in the Netherlands

Paul Copini, Ute Sass-Klaassen & Jan den Ouden

University of Wageningen, Forest Ecology and Forest Management, PO Box 47, 6700 AA, Wageningen, The Netherlands

In the Netherlands large oak clusters (Quercus robur L. & Q. petraea (matt.)Liebl.) with sizes up to 33 meters in circumference were discovered in 2001. Genetic research of oak clusters in a drift sand area as well as in an area with preglacial material showed that these large clusters can be genetically identical, but can also contain a mixture of genotypes. Still there is the question how these oak clusters originated?
We used amongst others a dendrochronological approach to study growth pattern and age of stems belonging to oak clusters with a known history (e.g. coppice stools, grazed oaks shrubs) in order to find characteristics, which could be used to test hypothesis about the origin of these large oak clusters with unknown history.

Influence of climatic factors on the radial growth of Pinus sylvestris in different regions and habitat types in Latvia

Didzis Elferts

University of Latvia , Faculty of Biology, Kronvalda bulv. 4, Riga, Latvia, LV-1586

Scots pines (Pinus sylvestris) in Latvia grow in different habitat types, for example, on dunes, in bogs, on sandy soils. The climatic conditions across Latvia also differ, and there are some regional changes that could have an effect on the growth of pines. The aim of this study is to determine the main climatic conditions affecting the growth of Scots pine (Pinus sylvestris) in Latvia and if there are differences across regions and habitat types.
Samples of tree-rings from pines were taken in different regions (sites) of Latvia using coring (one sample per tree) or taking stem disks (measured at three diameters). The habitat types were bogs, bog islands, dunes, forests on sandy soils. Tree-ring series were dated, then residual chronologies were built for every site, and also one common chronology including trees from all sampling-sites. Correlation and multiple regression analyses were used to determine the relationships between climatic factors (temperature and precipitation) and tree growth. Information on temperatures and precipitation were available starting from 1850 for the Riga region and from 1924 for other regions.
The response to climatic conditions differed among habitat types and regions in Latvia but there were cases when trees across Latvia responded similar to some climatic factors, especially in years with extreme climatic changes, for example, years with lower temperature compared to average temperature.
This study was financially supported by European Social Fund.

On chronology development and changes in sample replication.

David Frank, Jan Esper

Swiss Federal Research Institute WSL, Zuercherstrasse 111, 8903 Birmensdorf, Switzerland

 It is a common property of environmental time-series data that the number of observations does not remain constant over time. This consideration is inherent to dendrochronology whereby a chronology composed of living trees typically contains the greatest numbers of samples in recent years, with replication declining in earlier decades and centuries. Similar considerations apply to chronologies that combine relict/historical/sub-fossil material, networks of chronologies, and instrumental data. Varying sample replication results in quality changes in the mean-value estimate as well as changes in its local variance. In the case of the variance, if left uncorrected, the mean value function and any subsequent analyses will be systematically biased solely due to sample replication changes. In this talk, dendroclimatic results ranging from single site chronologies to a Hemispheric-scale temperature reconstruction will be presented that show how replication changes may manifest themselves in the mean time-series and also be considered/corrected.

Dendroclimatology in the Low Mountain Ranges, Germany

 Dagmar Friedrichs, B. Neuwirth & J. Löffler

Department of Geography, University of Bonn, Meckenheimer Allee 166, 53115 Bonn, Germany

The world-wide precipitation amount increased at about 2% within the 20 th century due to a changing atmospheric circulation. The spatial and temporal variability of this increase is not completely understood. Hence, for a profound assessment of the impact of global change on the regional scale further spatial high resolved analyses are indispensable. These analyses can only benchmark the current precipitation patterns by using long-term reconstructions. These reconstructions should place recent changes in context of the previous environmental situation. Although earlier studies indicate that precipitation is a dominant growth-limiting factor at specific sites, only few attempts have been made in Central Europe to reconstruct precipitation from tree rings. Initial dendroecological investigations in the Rheinische Schiefer­­­­­gebirge confirm the strong influence of precipitation on growing-patterns of oaks and demonstrate that tree-ring/climate-relationships are not constant over time. In this study long and annually resolved tree-ring records will be used to estimate changes in precipitation variability over, at least, the last three centuries for the northern low mountain ranges in Germany and parts of some neighbouring countries. By combining recent and historical ring-width series, we intend to analyse the signals of both, temperature and precipitation on tree-ring growth in order to reconstruct precipitation patterns. A new methodological approach will be established, whereby we will consider the spatial and temporal variability of relationships between tree rings and climate. This approach combines dendroecological methods and multivariate statistics such as cluster analysis and GIS techniques. To include the spatial variability of precipitation patterns in the dataset a spatially high-resolved network of sites will be arranged for the entire study area. The reconstructions will present precipitation variability on different temporal scales, from interannual to multi-decadal.

Combining different tree-ring parameters for a multi-proxy approach: an example from the Tibetan plateau

Jussi Grießinger (1,2), Achim Bräuning (2) & Gerhard H. Schleser (1)

(1) Forschungszentrum Jülich, Institute für Chemie und Dynamik der Geosphäre ICG-V, Abt. Isotopengeochemie und Paläoklima, D-52425 Jülich
(2) Universität Stuttgart, Institut für Geographie, Azenbergstr. 12, D-70174 Stuttgart.

Analysing climate and environmental information from tree ring data is a common tool for reconstructing past environments. Most of these reconstructions are mainly based upon one single parameter like ring width or maximum latewood density. In recent publications, McCarrol et al (2003) and Gagen et al (2004) demonstrated the high potential of combining different tree-ring proxies for dendroclimatological investigations.
The location of our sampling site is close to the upper treeline near the city of Qamdo in south-eastern Tibet. The location is representative for the regional climate of the eastern part of the Tibetan plateau. The trees at the study site are very sensitive to climate variations and therefore very suitable for a detailed proxy-climate investigation. The region is characterized by a seasonal change of two major atmospheric circulation systems. During summer, humid air masses of the Indian summer monsoon and the East Asian monsoon are the prevailing factors of regional climate. In winter, cold westerly winds with small amounts of precipitation are dominating.
The aim of our study is to analyse the potential of combining different tree-ring parameters like ring width, maximum latewood density data and stable carbon and oxygen isotope series for a comprehensive climate reconstruction. To study tree-species specific reactions to climate forcing we use two different tree species. We selected junipers (Juniperus tibetica) from a southern slope and spruce (Picea balfouriana) from a northern slope. Both species provide continuous, annually resolved records covering a period of approximately the last 400 years for all investigated proxies.

McCarroll, D., R. Jalkanen, S. Hicks, M. Tuovinen, M. Gagen, F. Pawellek, D. Eckstein, U. Schmitt, J. Autio & O. Heikkinen (2003): Multiproxy dendroclimatology: A pilot study in northern Finland. In: The Holocene 13(6):831-841.
Gagen, M., D. McCarroll & J.-L. Edouard (2004): Latewood width, maximum density and stable carbon isotope ratios of pine as indicators in a dry, subalpine environment. In: Arctic, Antarctic and Alpine Research 36(2):166-171

Wood anatomy and Dendrogeomorphology - Reaction wood varieties caused by different experimental treatments

 Ingo Heinrich (1), H. Gärtner(2) & M. Monbaron(1)

(1)Department of Geosciences, Geography, University of Fribourg, 1700 Fribourg, Switzerland
(2)Swiss Federal Research Institute WSL, Zürcherstrasse 111, 8903 Birmensdorf, Switzerland

Geomorphic events such as debris flows usually have a significant impact on tree growth resulting in conspicuous changes of ring-widths and wood densities. To date, several dendroecological techniques have been developed for the successful determination of frequencies of these events. However, it has only rarely been accomplished to retrieve more information from the reaction wood, e.g., type and intensity of the geomorphic event. Additional qualitative information retrieved from the reaction wood of trees hold the potential to not just date but reconstruct important characteristics of natural hazard events. The ability to date mass movement events intra-seasonally and also to retrieve more qualitative details would be particularly helpful in study regions without detailed knowledge of the predominant geomorphic process. Long-term reconstructions of geomorphic events would also benefit because it is likely that the tree-ring signals for different mass movements such as debris flows and avalanches can not be separated when occurring at the same site and consequently are all mixed into one reconstruction not distinguishing between the different processes. Consequently, comprehensive wood anatomical analyses of reaction wood induced artificially as part of a growth experiment have the potential to obtain more complete information on the potentially different tree reactions to these dissimilar events. To refine the methods already used in dendrogeomorpology long-term growth experiments imitating typical impacts of different geomorphic events were set up. During the experiments the wood anatomical reactions of four common European tree species (Picea abies, Larix decidua, Fagus sylvatica and Alnus glutinosa) were monitored over a period of 18 months. The results demonstrate that the tree species show distinct variations in their reactions due to the various experimental treatments differing in intensity and intra-seasonal timing. This new interdisciplinary approach has advanced commonly used techniques in dendrogeomorphology which will help to extract more detailed qualitative and quantitative information stored in trees and to improve the knowledge of natural hazard processes in future applications.

Intra-seasonal oxygen stable isotope signals in the arboreal system – A case study with Pinus strobus and Fagus sylvatica

Gerd Helle (1), T.J. Drees (2), P. Strauch (2) & G.H. Schleser (1)

(1) Forschungszentrum Jülich GmbH, Institut für Chemie und Dynamik der Geosphäre, ICG-V: Sedimentäre Systeme, 52425 Jülich, Deutschland
(2) Westfälische Wilhelms-Universität, Institut für Ökologie der Pflanzen, Hindenburgplatz 55, 48143 Münster, Deutschland

Dendrochronology has in the past provided most valuable information (wood anatomy, ring density, ring width, and wood isotopes) on environmental change at annual/seasonal resolution. However, tree rings do not directly record changes in their vicinity. Therefore, it is very difficult to deduce quantitative information on annual or seasonal scale, because the applied (statistical) methods, based on our current understanding of tree-ring formation are rather limited. A better understanding of the processes governing tree-ring response to environmental forcing is needed for understanding the causes and limits on past and future tree growth. In this respect, high resolution intra-annual isotope studies of the arboreal system can help to elucidate the seasonal signal transfer in trees and their response to environmental changes.
It has to be considered, that intra-seasonal changes of ambient environmental conditions are recorded within a tree-ring by the specific way continuous accumulation of wood cells develops during the growing season. Furthermore, climatic factors govern isotopic effects, mainly at the site of photosynthesis, i.e. leaf level, and subsequent fractionations re­lated to plant physiological processes alter further the isotope signals stored in the tree-rings.
The poster will focus on results from the ongoing ecophysiological process studies on isotope signal transfer in trees from a forest lysimeter facility in St. Arnold in NW-Germany. Up to now over 40 years of tree-growth measurements, meteorological variables and local water cycling data are at hand. Results on intra-seasonal oxygen stable isotope variations in relation to carbon isotope and wood density analyses on Pinus strobus and Fagus sylvatica trees will be presented.

Interactions between archaeology, trees and climate in northern England.

Jacqui Huntley

English Heritage and Department of Archaeology, Durham University.

Sea defense management at Staithes in North Yorkshire, UK uncovered timbers and associated roundwood considered to be man-made. Archaeological investigation was undertaken. The large timbers were radiocarbon dated to the Bronze Age, ca 3300 years ago and their ring sequences produced a good internal cross-match. These, however, could not be matched to any master chronology, despite knowing their radiocarbon age. This paper produces some research undertaken to investigate this, looking at the two species of British oak, Quercus robur and Q. petraea and their responses to warmth and moisture. Preliminary results suggest that there are significant differences in these responses meaning that any technique to characterise archaeological wood towards one or other of these two species could be crucial.

The dendrochronological records of debris flow activity in SE Quebec

Ryszard J. Kaczka, Hubert Morin

Laboratoire d'Écologie Végétale, Université du Québec à Chicoutimi, Quebec, Canada

The debris flow, rapid mass movement of water-saturated sediments, is one of the main processes modeling the high mountainous slopes. However this phenomenon can occur on each steep hill covered by unconsolidated sediments. The postglacial relief of the south-east Quebec, rich of steep-slope fjord type valleys, is conducive to study the debris flows activity in non-mountainous environment. The area of investigation covered by boreal forest consists of coniferous species as balsam fir ( Abies balsamea ), white spruce ( Picea glauca ) black spruce ( Picea mariana ). The aim of the study was to assess the spatial and temporal dynamics of that particular kind of mass movement. The stages of debris flows activity and the post-event evolution of the debris flow were reconstructed. The scars, inter-trunk wood anomalies (reaction wood, resin ducts) and tree ring patterns (growth reduction) were use as sources of information about the debris flows activity. They record both the date and intensity of the mass movement with annual precision. The existence of the model of inter-annual ring development of balsam fir in boreal forest, gives the opportunity of even more accurate dating. The study of the phase of development of exposed part of the ring reflects the period of the growing season when injures of trees and damages of the cambium occurred. The research was conducted in three valleys in north of the Saguenay River . Twelve cases of two types of debris flows were studied. The geomorphologic characteristic of slopes and the debris flows were established by field examination and analysis of the maps and satellite images. The disc samples (approximately 20 per site) were taken from the trees growing on the edge and fan of debris flows. The comparison of existing records of daily precipitation and obtained dates of debris flows events shows that even daily rainfall, which reached 40 mm could trigger the failure. The last and also very intense period of debris flows activity occurred in 1996, and was related to extremely high precipitation (almost 100mm on July 19 th and 50mm on September 14 th). All 12 examinated debris flows were active in 1996 and for some of them evidences of previous movement were not found. Erosion of all uncovered parts of the debris flows (levee, lob and fan) has remained the main post-event morphological process after 10 years of the events. Most of the dated events occurred in the second part of the 20 th century. The dynamic of boreal balsam fir forest is the main limiting factor of the dating of older events (the average age of sampled tees did not reach 100 years).

Response kinetics of tree radial growth to environmental perturbations - A challenge to the equilibrium hypothesis

Hans-Peter Kahle

Institute for Forest Growth, University Freiburg, Germany,

Tree radial growth varies on different time scales. In chronology building the concept of standardization builds on the hypothesis of equilibrium growth. Elasticity is an important component of equilibrium conditions. Systems that maintain their properties despite disturbance and that return rapidly to their original state exhibit more stable properties. However, depending on the nature, magnitude, and duration of the perturbation and on the nature of the system itself it may never recover to its original state but will be converted to a new state. Hence, the stability of an ecological system to environmental perturbations can be assessed by means of its elasticity.
This research into the growth response kinetics of Norway spruce (Picea abies L. Karst.), silver fir (Abies alba Mill.) and common beech (Fagus sylvatica L.) trees is based on observational growth data from southern Germany. Long-term tree-ring time series from selected sites were retrospectively analyzed using superposed epoch analysis. Response surfaces were parameterized to model growth elasticity.
The rate of radial growth elasticity depends on the magnitude of the initial growth deflection, it differs between tree species and depends on tree age as well as on the site conditions. Furthermore it is shown, that radial growth elasticity is not constant over time.

Dendroglaciological reconstruction of late-Holocene glacier activity in the southern Boundary Range, British Columbia Coast Mountains, Canada .

Sarah Laxton (1), S. Jackson (2) and D.J. Smith (2)

(1) Department of Geology, University of Cincinnati, Cincinnati, Ohio 45221-0013, U.S.A.
(2) University of Victoria Tree-Ring Laboratory, Department of Geography, University of Victoria, Victoria, British Columbia V8W 3P5, Canada.

Accelerated glacial recession and downwasting in Pacific North America is exposing land surfaces and features buried by glacial advances that, in many locations, predate the recent Little Ice Age. Dendrochronologic analyses of increment core samples from living trees (Abies lasiocarpa,Tsuga mertensiana) and samples of subfossil wood collected in the Todd Icefield area, Boundary Ranges, British Columbia Coast Mountains, provide the basis for a dendroglaciological reconstruction of late-Holocene glacier activity. Radiocarbon analyses and tree-ring crossdating resulted in the identification of several phases of late-Holocene glacier activity including the: Sage Advance (BC 420-200); the Bridge Advance (AD 405-640); and, four intervals of Little Ice Age glacier fluctuation (AD 1200-1390; 1250-1420; 1400-1630; 1640-1950). Our findings confirm the timing of late-Holocene glacier activity emerging from other regions in the British Columbia Coast Mountains. In addition, they provide the basis for developing an annually resolved tree-ring and glacial advance chronology that potentially spans the last three millennia.

Long-term trends in growth of Siberian spruce and Scots pine in Komi Republic, Russia

Eugene Lopatin (1,2), Taneli Kolström (2), Heinrich Spiecker (3), Hans-Peter Kahle(3)

(1) Institute of Biology, Komi Science Centre, Ural Branch, Russian Academy of Sciences, Syktyvkar, Russia
(2) University of Joensuu, Mekrijärvi Research Station, Joensuu, Finland,
(3) Albert-Ludwigs-University Freiburg, Institute for Forest Growth , Freiburg, Germany

To adopt forest management practices to changing environment, it is important to understand the response of unmanaged natural forests to changing climate. Komi Republic is the region of Northwestern Russia where large areas of natural boreal forest still exist. Analysis of climate data for the last century showed that significant long-term trends in climate can be identified in this region. During the last 20 years air temperature increased at most of the meteorological stations compared to the preceding 40 years period and precipitation began to increase too. Length of thermal growing season substantially extended in the region.
In order to retrospectively analyze tree growth along a latitudinal transect across the region stem discs or increment cores from sample trees were collected in six stands in four forest zones of Komi Republic: south taiga sub zone of boreal forests, middle taiga sub zone of boreal forests, northern taiga sub zone of boreal forests, and forest-tundra transition zone. Mature dominant trees without visible signs of damage were randomly selected as sample trees (n=92 trees of Siberian spruce and n=90 trees of Scotch pine).
Significant long-term trends of increasing site productivity were detected. Increase in mean apical growth of Siberian spruce in the forest-tundra transition zone for the last 50 years was 29.8% compared to the long-term mean level of growth of the previous 50 years. The respective figures for the other zones are: northern taiga zone 25.0%; middle taiga zone 19.1%, and southern taiga zone 0.4%. Increase in apical growth of Scotch pine in the northern taiga zone was 6.8%; in middle taiga zone 37.9%; in southern taiga zone 88.3%.

Dendrochronological records of erosion and accumulation in mid-mountain stream ( Jeseniki Mountains – Czech Republic)

Ireneusz Malik, Piotr Owczarek

University of Silesia, Faculty of Earth Sciences, Bedzinska 60, 41-200 Sosnowiec, Poland

Date of exposure of spruce roots as result of bank erosion and tree rings reduction as result of mechanical stress was investigated on the Cerny Potok in the north-eastern Czech Republic. Following the exposure of roots, wood cells in the tree rings divide into early wood and late wood. Root cells within the tree rings also become smaller and more numerous. These processes permit the erosion episodes in which roots were exposed to be dated. Material is transported downstream and wounding spruces growing in the bottom of the valley as result of this process tree rings reduction occur. Forty root samples and thirty five cores from trees were taken from seven sampling sites. The results of root exposure dating and trees wounding were compared to historical data on hydrological flooding. Using the root exposure tree ring reduction dating method, several erosion episodes were recorded in the last 100 years.
The greatest bank erosion was recorded in July 1997 during an extraordinary flood, but several another erosion and accumulation episodes were recorded. A lot of signals were recorded in 1953, 1968, 1983 and 1986. Signals recorded by exposed roots analyse very often are not synchronic with signals recorded by tree rings reduction. Material is delivered into the river channel not only as results of bank erosion. Numerous debris flow events in the upper part of the studied valley supply material to the riverbed.

Dendrogeomorphological analysis of alpine trees and shrubs growing on active and inactive rockglaciers  

Isabelle Roer (1,2), Holger Gärtner (1) & Ingo Heinrich (3)

(1) Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Zürcherstrasse 111, 8903 Birmensdorf, Switzerland
(2) Department of Geography, University of Bonn, Meckenheimer Allee 166, 53115 Bonn, Germany
(3) Department of Geosciences, Geography, University of Fribourg, Pérolles, 1700 Fribourg, Switzerland

The occurrence of permafrost and related landforms (rockglaciers) is a widespread phenomenon in many high mountain geosystems. Diverse methods like geomorphic mapping, geodetic survey as well as photogrammetric analyses were applied for the determination of permafrost distribution and rockglacier kinematics in order to understand the geosystems’ sensitivity to climatic changes. In this study we present the first-time application of dendrogeomorphological methods in this context.
To determine the impact of permanently frozen ground and the influence of ground movements (by permafrost creep) on plants, wood-samples were taken from active and inactive rockglaciers in the Turtmann Valley, southern Swiss Alps. Due to their typical position above timberline, the occurrence of trees is limited. Therefore, the investigation was restricted to single trees (Pinus cembra) and several shrubs (mainly Salix helvetica). The plants sampled cover a period of 30 to 40 years. Working with dwarf shrubs, the extraction of cores is in most cases not possible. Thus, the whole plant was cropped and samples were taken from roots and stems. Besides the analysis of ring-width variations, the analysis focused on the anatomical structure of the rings and the distribution of vessels in stems and roots.
The findings indicate a probable influence of the ground movement on the plants. The reaction wood in a Pinus cembra stem at the rockglacier front clearly suggests an increase in horizontal velocity in the beginning of the 1990s which is supported by velocities quantified by photogrammetrical analyses. Regarding the Salix helvetica shrubs, no obvious differences in ring width variations between the unstressed and stressed samples from the inactive and active rockglaciers, respectively, were found. However, a comparison of vessels within individual rings of the stressed and unstressed samples revealed general differences in size. Especially the vessels in roots taken from the inactive rockglacier tend to be larger than those from the stressed site.

Twentieth century as the wettest period in Northern Pakistan over the past millennium

Kerstin Treydte (1), Gerhard Schleser (2), Gerhard Helle (2), David Frank (1), Matthias Winiger, Gerald Haug, Jan Esper (1)

(1) Swiss Federal Research Institute WSL, 8903 Birmensdorf, Switzerland
(2) Forschungszentrum Jülich, Institute für Chemie und Dynamik der Geosphäre ICG-V, Abt. Isotopengeochemie und Paläoklima, D-52425 Jülich.

There is evidence that 20th-century warming could lead to increases in the moisture holding capacity of the atmosphere altering the hydrological cycle and the characteristics of precipitation. Despite the existing co-variability of both climate variables, attention in long-term climate reconstruction has recently concentrated on temperature changes. We present the first annually resolved oxygen isotope record from tree-rings, providing a millennial-scale reconstruction of precipitation variability in the high mountains of northern Pakistan. Low-frequency variations reveal dry conditions at the beginning of the past millennium, and through the 18th and early 19th centuries, with precipitation increasing during the late 19th and the 20th century to yield the wettest conditions of the last 1000 years. Comparison with long-term precipitation reconstructions from synoptically different regions like Europe or Western USA indicates a large-scale intensification of the hydrological cycle coincident with the onset of industrialisation and global warming. Its unprecedented amplitude argues for a human role.

Treydte, K., Schleser, G.H., Helle, G., Frank, D.C., Winiger, M., Haug, G., Esper, J. 2006: Twentieth century as the wettest period in Northern Pakistan over the past millennium. Nature, in press.

Fire-climate interactions in the Mediterranean climate areas of California, Southern Oregon, and Western Nevada

Valerie Trouet, Alan Taylor

The Pennsylvania State University, Department of Geography, 302 Walker Building, 16802-5011, University Park, PA, USA

Wildland forest fires are, and have been, an important process shaping forest ecosystem structure and function in the fire-prone Mediterranean Climate Area (MCA) forests of the North American Pacific Coast. The long-term and large-scale suppression of fire activity in many forests in the Western U.S. has led to an increased risk of devastating fires because fuels are allowed to build up to unnaturally high levels. The development of prefire management plans, with a primary goal of reducing the build-up of fuels, is critical to alleviate loss of life and property associated with wildfires and to facilitate long-term sustainability of forest ecosystems in the region. Understanding the role of wildfire in forest ecosystems and the factors influencing wildfire behavior is essential for the development of these management plans.
The goal of this study is to identify the relationships of inter-annual and intra-decadal climate variation and multi-decadal and multi-century climate change on sub-regional variation in fire regimes in the MCA of the Pacific Coast. The fire occurrence variation on a sub-regional to regional scale over periods of decades to centuries is determined using fire scar chronologies as a proxy of fire activity. Long-term fire-scar records were collected at more than 50 sites, extending from northern Baja California to Southern Oregon. The variation in fire occurrence is related to multi-century tree-ring reconstructions of climate (temperature, precipitation, PDSI) and dominant modes of circulation (PDO, ENSO, PNA).

Analysis of rootwood of Scots pine

Hanuš Vavrčík, Vladimír Gryc, Michal Rybníček

Mendel University of Agriculture and Forestry Brno, Faculty of Forestry and Wood Technology, Department of Wood Science, Zemědělská 3, 613 00 Brno, Czech Republic

Dendrochronological and anatomical analysis of rootwood of Scots pine (Pinus sylvestris L.) tree was carried out. The relation (synchronization) between widths of rings in the root and widths of rings in the stem was studied. We supposed that widths of rings in root may be the valuable source of ecological signal the same as widths of rings in stem. Ring analysis of stem was carried out for comparison. The curves of ring widths of horizontal roots were synchronized together with high values of the corelate coeficient and paralellism coeficient. The curves of ring widths of roots were synchronized with ring widths of tree stem.
Radial diameters and thickness of cell walls of tracheids were measured in one horizontal root (8 m in length total). Rings of root from part close to the stem base shown the similar structure (earlywood and latewood portion) as stemwood rings. Rings visibility and portion of latewood decreased along the root length (from the stem base to the root tip). Latewood of each ring in rootwood was formed only by one or two tracheids in each radial row. False rings occurred frequently in rootwood.
The number of tracheids per ring decreased along the root length. The radial dimension of tracheids increased along the root length.
There were different trends of the dependency of the radial dimension of tracheids on the relative position of tracheid within ring (root section 0.2m from the stem base).
The radial dimensions of tracheids decreased from earlywood to latewood within rings close to cambial zone. On the other hand the dimensions increased within almost whole ring in rings that were close to the central part of the root. Remarkable decrease of the radial dimensions of tracheids was observed in last tracheids of each ring. Variability of cell wall thickness of tracheids from central part of root was lower than variability of tracheids from rings close to cambial zone (valid for section taken from 0.2m from the stem base).
The project was financially supported by the research plan of LDF MZLU in Brno, MSM 6215648902.

Radial growth as influenced by light and nutrient availability

Pascale Weber, R.D. Bardgett

Department of Biological Sciences, Lancaster University, Lancaster, LA1 4YQ, United Kingdom

Tree growth is, besides endogenous factors, influenced by various exogenous factors such as light and nutrient availability. However, the relative importance of belowground properties related to nutrient availability for tree growth and regeneration has not yet been studied. In this study, we combined dendroecological with soil ecological methods to investigate how single freestanding trees influence soil properties and thereby the growth of regenerating trees in their neighbourhood zone. We tested the hypothesis that soil properties affect the radial growth of the regeneration besides light availability and browsing pressure.
In a remnant of the old Caledonian forests in Scotland, 16 old and dominant Scots pine (Pinus sylvestris L.) trees were chosen. These trees can be described as making up a patch on their own and probably causing a gradient in light and nutrient conditions from their stems to their outer crowns. Around each tree, soil samples were taken and the vegetation was recorded in three zones, defined as inner, middle and outer zone of influence. Increment cores of both the dominant and adjacent regenerating trees were extracted to measure the age and the radial growth of each tree.
Soil properties, such as moisture content and availability of different nutrient forms, were found to differ among the three zones. These differences might be explained by several processes, such as the tree’s water uptake and transpiration, the needle litter input to the soil, which alters the decomposer community and nutrient cycling, and root actions.
The results of the soil ecological analyses together with forthcoming light measurements at each tree are aimed at revealing the relative importance of below- (nutrients) versus above- (light) ground factors for the abundance and growth of Scots pine regeneration in the forest remnants. Currently, regenerating these forests is mainly based on reducing browsing intensity by fencing and by downsizing dear populations through culling. With this study, we hope to provide new insights in the regeneration ecology of Scots pine with respect to light and nutrient requirements to further enhance conservation and management strategies.

Reconstructing the flow of the river Nile from carbon isotopes and other proxies in Juniperus procera tree rings

Tommy H.G. Wils (1), I. Robertson (1), Z. Eshetu (2) & M. Gagen (1)

(1) Department of Geography, University of Wales Swansea, Singleton Park, SWANSEA SA2 8PP, United Kingdom
(2) Ethiopian Agricultural Research Organization (EARO), PO Box 2003, ADDIS ABEBA, Ethiopia

The aim of this project is to extend the limited discharge records of the river Nile by several centuries using carbon isotope ratios and other proxies from tree rings in 400-year-old Juniperus procera trees growing at a number of sites in Northwest Ethiopia.
The resulting hydrological and climatic records will highlight the influence of climate change on Nile discharge and improve water resources management in the basin, which is of great importance due to the increasing population depending on the Nile waters for agriculture and electric power.
Rainfall in the Ethiopian Highlands accounts for most of the Nile waters in Egypt through the Blue Nile, Atbara and Sobat rivers. Carbon isotope ratios in trees are strongly related to precipitation through its influence on stomatal conductance. However, this proxy is also influenced by varying rates of photosynthesis. This project will assess the impact of these competing influences by determining carbon isotope ratios, tree-ring widths, tree-ring density and earlywood-latewood ratios. All proxies will be measured at annual resolution and from at least five trees to ensure an adequate degree of replication. The reconstructed flow of the river Nile will be validated against historical measurements from the Rauda Nilometer in Cairo, Egypt.

Dendrochronological techniques applied on standing structures: a pilot study on the Czar Peter House in Zaandam, The Netherlands

Marta Domínguez Delmás (1), Tamara Vernimmen (1) & Gerard Horneman (2)

(1) Hollandia Archeologie / DendroLab NL, Tuinstraat 27ª, 1544 RS Zaandijk, The Netherlands, www.dendrolab.nl
(2) Zaans Museum / Czaar Peterhuisje, Krimp 23, 1506 AA Zaandam, The Netherlands,

August 1697. Czar Peter the Great arrives in Zaandam, the Netherlands, determined to become personally acquainted with the arts of shipbuilding, which Dutchmen are famous for. Zaandam was at that time the most important centre of such craftsmanship and the Czar had planned to stay the whole winter. The massive attention he received from the local population, however, forced him to leave after only 8 days.
During his short stay, Peter the Great was lodged at a small and humble wooden house, which was built, like many of the houses in the Zaandam area, with planks from boats taken apart at the local wharfs. The impact of his visit was so strong that the little dwelling was later turned into a museum and has become a place of pilgrimage for Russians and historians all over the world.
Still, certain parts of the Czar Peter House have been altered over the last centuries to safeguard the integrity of its structure. However, traces of further alterations have been found which do not appear to be documented.
In order to identify and date the modifications the house was subjected to, a dendrochronological pilot study has been undertaken in collaboration with the Zaans Museum/Czaar Peterhuisje. Due to the fact that the house is a protected historical monument none of the usual techniques apply. Therefore the tree-ring pattern of the planks had to be measured in situ using a relative or non-fixed scale, in the radial to tangential section. No preparation of the surface was allowed. Micro-samples were taken for wood identification in non-visible parts of the planks.
Preliminary results show three different wood species present in the house: Abies alba Mill., Picea abies L. (Karst.) and Pinus sp. Synchronisation between planks proved possible in some cases. The dating of the index series is still pending as the research is ongoing. Provenance of the samples will also be investigated. Recording and dating the tree ring patterns of conifers in the radial/tangential section with a relative scale has proved to be a challenge, yet not impossible.

3D-modelling of roots - New application for analysing root system development

Holger Gärtner

Swiss Federal Research Institute WSL, Zürcherstrasse 111, 8903 Birmensdorf, Switzerland

Several attempts have been made in recent years to collect data on the morphology of root systems to represent their spread and size in three-dimensional space.
A practical tool to acquire data on the architecture of exposed root systems is the exertion of a magnetic field enclosing the root. A point-by-point exploration by means of a 3D-digitizer enables to measure and represent root lengths and bifurcations in three-dimensional space. The advantage of this method is the possibility to include branching order and branching pattern in the dataset. Regarding a more detailed analysis of total root structure, growth development as well as total and partial biomass measurements, the digitizing complexity would be too high. Further, no effort has been attempted so far to blend in tree-ring values into the digitized data. To realize this, a high resolution model of the root needs to be generated, which would necessitate an extensive digitizing work.
The application of a 3-D laser scanner to the admission of the structure of whole root systems, presented here, is a step towards the solution of this problem. Within Geosciences, laser systems are mostly used to generate digital terrain models. The possibility of receiving high resolution data (~1 mm) in short time combined with a fast and cost-effective post-processing of the data makes the data gathering and representation of highly complex structures a feasible task. At the Swiss Federal Research Institute WSL a ground based 3D- laser scanner was used in a feasibility study for the first time as a base to generate a three dimensional model of an exposed root system of a mature spruce tree. The study was accomplished to investigate the prospects and limitations of this technology.

True and false rings in Toona ciliata

 Ingo Heinrich

Department of Geosciences, Geography, University of Fribourg, 1700 Fribourg, Switzerland

Tree-ring proxy data from subtropical to tropical Australasia are valuable though rare sources for climate reconstructions. Toona ciliata M. Roem. occurring naturally in this region is among the most promising tree species for future tropical tree-ring research. New increment core samples of T. ciliata collected in the Australian tropics and subtropics exhibited difficult tree-ring structures. During tree-ring analysis two growth anomalies (extensive zones of narrow and indistinct rings) and three types of false rings were discovered which complicated crossdating. Furthermore, little is known about the species’ phenological behaviour and the influence of environmental conditions on intra-seasonal growth and wood anatomical properties. This necessitated a closer examination of the wood anatomy, possible false rings and the species’ crossdating capacity. Hence, growth experiments were conducted on young trees to investigate their responses to different treatments and whether false rings could be induced artificially. The results show that phenology and growth were adjusted according to the severity of the treatments. Restricted growth conditions often caused longer leafless periods, shorter flushes of leaves, decreased height and diameter growth increments and partly resulted in more but smaller vessels. Under optimum conditions T. ciliata did not become leafless, had multiple leaf flushes, sustained growth throughout the experiment and did not form a tree-ring boundary. All specimens entering leafless or at least semi-leafless periods formed one tree-ring boundary during the experiment. The growth reaction was more distinct in the latewood than in the earlywood, in extreme cases suppressing the latewood totally. Only one type of false ring could be induced artificially by totally defoliating young trees. It was possible to alter their phenological performance by artificially changing the environmental conditions. Visual crossdating of samples originating from northeast Australia was feasible within and between trees. For selected years a positive relationship between ring width and precipitation data was found. Although the experiment was conducted on young trees and hence might not be simply generalised and applied to adult specimens the results suggest that the species is well suited for reliable dendroclimatological investigations.

Virtual microscopy applied to wood anatomy

Benoit Jourez (1), Michel Herin (2), Jacques Hebert (3),

(1) Direction de Technologie du Bois, Centre de Recherches de la Nature, des Forêts et du Bois, Ministère de la Région wallonne, Avenue Maréchal Juin 23, 5030 Gembloux
(2) Laboratoire cellules et tissus, Département d'Histologie-Embryologie, Faculté de Médecine, Facultés Universitaires Notre-Dame de la Paix, Rue de Bruxelles 61, 5000 Namur
(3) Unité de Gestion des Ressources forestières et des Milieux naturels, Faculté universitaire des Sciences agronomiques, Passage des Déportés 2, 5030 Gembloux

Objective of virtual microscopy
A preparation is first digitised with a special tool that combines a microscope and a digital camera. The image of the digitised preparation can be instantaneously displayed on a screen with a chosen magnification. Actually, the digitisation concerns several levels of magnification and produces a multitude of tiles that a viewer software collects and displays according to the zone selected by the user.

Opportunities
Located on a server, these images can be shared by several users simultaneously (students during practical work or scientists working in distinct laboratories) located in the same site or in different sites and using, in this case, an Internet access. The classical tools for image analysis provide additional advantages compared to conventional microscopy.

Principles applied to wood anatomy
The project in progress deals with main temperate species in our region. About thirty species were selected. The Research Centre for Nature, Forests and Wood (Gembloux) carried out cuts of 12 m thickness according to 3 ligneous plans. The Laboratory of Cells and Tissue of the Faculty of Medicine of Namur University takes care of the digitisation of the cuts.

Illustration
The attached print screen shows a transverse section in a sample of oak. The software offers various tools: zoom, window of navigation, magnifying glass, measurement...

Additional information
Virtual microscopy applied to wood anatomy will be revealed to the general public on the occasion of the exposition "Knock on Wood" organised by the museum of Central Africa in May 2007. The visitors will be able to handle the images at their disposal.

13CO2 pulse-labeling of photoassimilates reveals carbon allocation within and between tree rings.

Akira Kagawa (1), Atsuko Sugimoto (2), Trofim C. Maximov (3)

(1) Wood Anatomy and Quality Laboratory, Forestry and Forest Products Research Institute, Tsukuba Norin P.O.Box 16, Ibaraki 305-8687, Japan
(2) Division of Geoscience, Graduate School of Environmental Earth Science, Hokkaido University, Sapporo 060-0810, Japan
(3) Institute for Biological Problems of Cryolithozone, Yakutsk, Russia.

In order to reconstruct past climate or to study tree growth response to expected climate change, tree-ring parameters such as ring width, density or stable isotope ratios have been used by many investigators. However, more knowledge on the physiological background of dendroclimatology is needed for improved quality of climate reconstruction. For example, autocorrelation is often observed in dendroclimatological research and potentially interferes with climate reconstruction. Proposed causes for autocorrelation are stored carbohydrates, climate effects on formation of buds, leaves, roots, and fruits, or hormones. Clarifying how much photosynthate in the previous year(s) is stored and then remobilized for current year’s tree ring formation will improve our interpretation of dendroclimatological data. Such potential problem is also pointed out in isotope dendroclimatological research. Farquhar model explains carbon isotope fractionation relatively successfully at leaf level, but it excludes downstream fractionation processes such as storage and remobilization of sugar and starch. For example, the model can not fully explain intra-annual δ 13C variation of ring-porous oak wood (Helle & Schleser 2004). Photosynthates assimilated close to the end of growing season can be stored and then remobilized for next year’s earlywood formation. For example, high correlation is reported between earlywood δ 13C values and latewood ones of the previous year in ring-porous English oak (Robertson et al. 1997). In order to apply tree physiological knowledge on carbon allocation to better interpret dendrochronological data such as autocorrelation of tree ring parameters, we need to study long-term carbon allocation with longer chase period up to a few years. We applied 13CO2 pulse-labeling method developed for studying the use of photosynthates for wood formation (Kagawa et al. 2005) to deciduous Siberian trees, in order to study seasonal course of translocation, storage and remobilization of photosynthates (Kagawa et al. 2006b) and time lag in its use for tree-ring formation (Kagawa et al. 2006a). We pulse-labeled 12 saplings of Larix gmelinii (Rupr.) Rupr. at the beginning (June), middle (July), and end (Augusut) of the growing season with the 13CO2. We enclosed the whole tree into a pulse-labeling chamber and later sampled the trees with chase periods from 3 days up to 3 years. Carbon allocation of 13C-labeled photosynthates to different body parts: leaves, branches, phloem & xylem of stem and roots were examined. Acid-soluble starch was extracted from each body part to study carbon turnover of storage material. High-resolution δ 13C analysis of the tre e ring formed was conducted by using a rotary microtome at 30 μm resolution. The spring (June) photosynthates were mainly allocated to aboveground part (over 92 %) and were used relatively quickly for earlywood formation. Relatively more summer (July) and autumn (August) photosynthates were allocated to belowground part (32-44% and 12-24%, respectively) and were used for following year’s tree ring formation. About 60% of labeled carbon in stored starch was replaced every year. Compression wood showed higher δ 13C values compared to normal wood, probably because compression wood is a strong sink of carbohydrates.

References
Helle G. & Schleser G.H. (2004) Beyond CO 2-fixation by Rubisco - an interpretation of 13C/ 12C variations in tree rings from novel intra-seasonal studies on broad-leaf trees. Plant, Cell & Environment, 27, 367-380.
Kagawa, A., Sugimoto, A., Yamashita, K., Abe, H. (2005) Temporal photosynthetic carbon isotope signatures revealed in a tree ring through 13CO 2 pulse-labeling. Plant, Cell & Environment. 28, 906-915.
Kagawa, A., Sugimoto, A., Maximov, T.C. (2006a) 13CO 2 pulse-labeling of photoassimilates reveals carbon allocation within and between tree rings. Plant, Cell & Environment (in press).
Kagawa, A., Sugimoto, A., Maximov, T.C. (2006b) Seasonal course of translocation, storage, and remobilization of 13C pulse-labeled photoassimilate in naturally growing Larix gmelinii saplings. New Phytologist (in review).
Robertson I., Switsur V.R., Carter A.H.C., Barker A.C., Waterhouse J.S., Briffa K.R. & Jones P.D. (1997) Signal strength and climate relationships in 13C/ 12C ratios of tree ring cellulose from oak in east England. Journal of Geophysical Research, 102, 19507-19516.

Is wood analysis a useful tool for studying growth respiration in tree stems?

An Saveyn, Kathy Steppe and Raoul Lemeur

Laboratory of Plant Ecology, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, B-9000 Ghent, Belgium

Interest in stem respiration is increasing as many quantitative estimates show that it is a large component of the annual carbon balance of forest ecosystems. Although the biochemical pathways are similar, stem respiration is generally separated into two components: maintenance respiration, which maintains existing living cells, and growth respiration, which provides the energy needed to synthesize new tissues. Growth respiration is supposed to be a function of diameter growth, which is usually measured with band-dendrometers or linear variable displacement transducers. However, several studies showed that peak of CO 2 emission by stems is much later in the growing season than maximum diameter growth. Diameter growth mainly reflects cell expansion. Cell expansion is a physical process requiring little chemical energy. The greatest energy requiring process is the incorporation of carbon skeletons into new cell structures. Unfortunately, this process can not be simply measured with a sensor. Therefore, this abstract aims at opening a new ground for discussion on the possibilities of wood analysis for growth respiration studies.

How do stable isotopes react on Larch Budmoth Outbreaks?

Kathrin Weidner (1,2), G. Helle (2), J. Löffler (1), B. Neuwirth (1), G. H. Schleser (2)

(1) Department of Geography, University of Bonn, Meckenheimer Allee 166, Germany
(2) Research Centre Jülich GmbH, Department of Chemistry and Dynamics of the Geosphere, ICG-V: Sedimentary Systems , Germany

European Larch ( Larix decidua Mill.) from the subalpine forest is commonly used for low-frequency temperature reconstructions (Büntgen et al., 2005). These subalpine forests form the habitat of the larch budmoth (LBM; Zeiraphera diniana Gn). A strongly increase of the population of this insect at intervals of 7-11 years leads to a typical tree-ring pattern, which is characterized by an abrupt growth reduction in the year of the outbreak and a slow increase of ring width in the following years. This typical tree-ring pattern causes problems in high-frequency climate reconstructions. The aim of this study was to investigate to what extent LBM outbreaks modify the signature of the stable carbon and oxygen isotopes of the corresponding tree-rings. The inter-annual and intra-annual carbon and oxygen isotope analyses bear more information on the mechanisms which are responsible for the observed pattern. Cores of two sites on the south-exposed slope at 2000 m and 1700 m a.s.l. in the Lötschental/Switzerland are prepared to investigate the reaction on LBM outbreaks of different intensities.

Tree rings chemical content fluctuations between acid and calcareous soils of Fagus sylvatica L stands measured by microanalysis.

Anny Weitner, J.L. Dupouey, R. Bailly, C. Rose

UMR Forest Ecology and Ecophysiology , Phytoecology team, INRA-NANCY, France

Differences in mineral nutrients content in beech (Fagus sylvatica L.) tree rings in the HNE network (Beech stands of north-eastern France) have been evaluated on two soils types. Six stands are located on acids soils and six others are located on calcareous soils. Three dominant trees have been cored in each stand. The chemical measurements have been made in the earlywood (12 stands, 3 trees by stand, one core per tree and two periods by core corresponding to ten rings in heartwood and ten rings in sapwood). The microanalysis of mineral nutrients concentration in tree rings have been measured with an energy dispersive spectrometer (EDS) coupled with a low vacuum scanning electron microscope.
We found differences between calcareous and acid stands in tree rings element concentration. Calcareous stands have typically high calcium and low manganese concentration in tree rings in comparison to acid stands. These differences are mostly representative of the nutrient richness of the soil and especially saturation rate and soil upper horizon pH. We also undertook to measure element concentration in the bark. It appears that differences in elements concentrations are greater when considering the bark compared to the wood. These results point out the ability of SEM/EDS method to measure differences in two soils type differing in acidity status. We showed that tree nutrient status is reflected in wood and to a better extend when considering the bark only. Bark seems to have a high potential to be used as a tree nutritional status diagnostic.