Die Bilder grossflächig brauner Laubbäume in weiten Teilen der Schweiz sowie Zentraleuropas im Fr... more Die Bilder grossflächig brauner Laubbäume in weiten Teilen der Schweiz sowie Zentraleuropas im Frühsommer 2018 sind uns noch sehr präsent. Diese um rund drei Monate verfrühte Herbstverfärbung der Wälder war das Resultat der extre-men Hitze und langanhaltenden Dürre. Auch wenn das Ausmass und die Sichtbar-keit der Schäden in Wald und Landwirtschaft 2018 ausserordentlich waren, so stel-len wir eine Häufung von solchen extremen Hitze-und Trockenjahren (2003, 2011 und 2015) fest. Laut dem neuesten Klimabericht für die Schweiz muss davon aus-gegangen werden, dass Hitze-und Dürreperioden in Zukunft noch häufiger auf-treten dürften. Was heisst dies nun für unsere Wälder? Wie viel Trockenheit kön-nen sie ertragen? Wir diskutieren diese Fragen anhand von Daten aus verschiede-nen Monitoringansätzen und zeigen auf, dass die verschiedenen Waldökosysteme sehr unterschiedlich reagieren und die zukünftige Dynamik unserer Wälder von der Kombination und dem zeitlichen Auftreten von Trockenheit und anderen Wetterextremen abhängen wird.
The efficiency of water use and transport are among the main factors affecting competitiveness, g... more The efficiency of water use and transport are among the main factors affecting competitiveness, growth, and distribution of trees under warming climate. The phenotypical and genetic plasticity of tree populations is considered as an indicator of their adaptive capacity under changing environment. Climatic changes are expected to affect growth of Scots pine (Pinus sylvestris L.), and selection of reproductive material among the populations suitable for future climates has been advised for sustaining productivity of stands. In this regard, provenance trials can serve as source of comprehensive information about growth plasticity and climate-growth interactions of diverse populations. Quantitative wood anatomy can provide detailed information about xylo-genesis and factors affecting it, which are crucial for long-term predictions. Wood anatomy of two top-(Gustrow and Rytel), two low-performing (Eibenstock and Dippoldiswalde), and one local (Kalsnava) provenances of Scots pine from the eastern Baltic region growing in three provenance trials in Latvia was studied using mixed models, accounting for the experimental design, as well as using the time-series approach. Provenance had a significant effect on the studied wood anatomical proxies, indicating genetic adaptation of xylogenesis. The top-performing provenances, which originated from warmer and drier conditions, had tracheids with larger lumens and thinner walls, thus indicating adaptation to water deficit. The top-performing Rytel provenance showed the highest phenotypical plasticity of lumen cross-section area and cell wall thickness of stemwood tracheids. The studied low-performing provenances, which originated from the Orr Mountains, had tracheids with thicker wall and smaller lumens, likely to ensure mechanical durability. The local provenance showed intermediate values of the studied wood anatomical proxies. The effect of provenance on wood anatomical proxies showed some variations among the trials, which differed by continentality, likely due to ecological transfer distance. The studied anatomical proxies were affected by weather conditions prior and during formation of a tree ring, yet these relationships differed by trial and provenance. In general, wood anatomy of earlywood was affected by temperature in the dormant period and beginning of summer, as well as precipitation in the end of the previous vegetation period. Proxies of latewood showed correlation with temperature (negative) and precipitation (po-sitive) in summer, suggesting response to the availability of water. Considering the observed relationships, the top-performing provenances, particularly Rytel, have a high potential to sustain productivity of stands within the region in the future.
Plants essentially contribute to the strength of soil and, in particular, steep slopes susceptibl... more Plants essentially contribute to the strength of soil and, in particular, steep slopes susceptible to erosion and shallow landslides. The corresponding functions of vegetation significantly control processes above and below ground such as interception , evapo-transpiration, soil aggregation and root reinforcement. Either way, they are all correlated with plant growth. Consequently, in order to unfold their soil stabilising potential, the plants must grow and sustainably survive. However, what sounds so obvious is anything but given under the often hostile conditions dominating on bare and steep slopes. This is exactly the point where mycorrhizal fungi come into play, known to improve the plants' ability to overcome periods governed by strongly (growth) limiting factors. Within this scope, numerous investigations have been conducted in order to understand and quantify mycorrhizal effects on different plant and soil functions related to eco-engineering and, particularly, to soil and slope stability. Results on plant growth and survival as well as on soil aggregation and slope stabilisation are presented and discussed from a mycorrhizal perspective.
The annual growth and wood characteristics of tree species at southern Mediterranean countries, a... more The annual growth and wood characteristics of tree species at southern Mediterranean countries, and its relationship with climate variables are recently two important topics for the researchers in this region. Although Moringa peregrina (Forssk.) Fiori is a key species in Africa due to its medicinal and economic values (e.g. as fuel, food and water purifier), little is known about its annual growth or its response to climate variables. In this study, we analyze its dendrochronological potential, macroscopic and microscopic wood structure, and correlation with climate. Wood discs were collected from two desert sites in Egypt: Saint Catherine (SC) and Hurghada (HG). Wood discs and micro-slides were prepared, and the distinctness and pattern of rings, vessels, and ray structure were examined microscopically. The ring boundaries of M. peregrina were distinct and marked by thick-walled and flattened fibers. For the HG site, the resulting ring-width chronology spans 16 years, from 2001 to 2016. A significant positive relationship was found between tree growth at HG and precipitation prior to the vegetation period (January-March). April temperature of the year prior to growth had a significant positive relationship with M. peregrina growth. In contrast, April and May-August temperatures of the current growing season had a significant negative relationship with tree growth. We could not develop a chronology for M. peregrina at SC site due to the presence of growth anomalies in the collected wood discs from the site. Consequently, we did not get a clear picture on the climate-annual growth relationship for M. peregrina trees at this site. At SC, M. peregrina trees respond to stressful environmental conditions by adjusting their anatomical structure to produce a high number of small vessels. Moreover, there was spatial variability in the architecture of ray parenchyma that reflected the degree of stress in both sites. The results of this study improve our understanding of the growth-climate relationship in subtropical trees and the potential role of ray parenchyma in stressed environments.
A R T I C L E I N F O Keywords: Ailanthus altissima (tree of heaven) Tree-ring Climate growth rel... more A R T I C L E I N F O Keywords: Ailanthus altissima (tree of heaven) Tree-ring Climate growth relationship Vessel lumen area Wood anatomy Invasive tree A B S T R A C T Knowledge on the ecology of tree species in both their native and introduced range can increase the understanding of their successful establishment and spread outside the native range. Here, we analysed radial growth patterns of Ailanthus altissima (Mill.) Swingle in two sites in its native range in eastern China and in two sites in the introduced range in southern Switzerland, where it started to disperse into forests in the 1950s. Growth rates were similar despite lower amounts of growing season precipitation in China. Furthermore, we found negative correlations between annual radial growth and average temperatures in the growing season at the warmest of the four sites, which suggest that radial growth of A. altissima starts to be limited by average growing season temperatures above 21 °C. Regarding wood anatomy, we did not find clear correlations between vessel lumen area and monthly temperature or precipitation at the time of tissue formation in spring. Overall, our results demonstrate that A. altissima has the potential to grow in drier conditions than currently found in Switzerland, which is in line with previous studies.
A spatiotemporal reconstruction of slope movements on the edge of Lake Lucerne near the municipal... more A spatiotemporal reconstruction of slope movements on the edge of Lake Lucerne near the municipality of Horw, canton of Lucerne, is presented. The reconstruction was realized by analyzing growth reactions of beech (Fagus sylvatica L.) and fir (Abies alba Mill.) trees growing on this slope. Before dendrochronological sampling, a detailed geomorphological mapping of the landslide was conducted with the aim to determine the spatial extent of the sliding area. For tree-ring analyses, 124 increment cores from 62 trees were analyzed following standard techniques of dendrogeomorphology. In addition, long micro-sections were prepared from the entire cores to extend the common eccentricity analyses by microscopic determination of the onset of reaction wood in fir and beech. Results clearly show that the area is moving at least since 1948. A significant concentration of events was observed between the years 1990 and 2000 as well as after 2006. The definition of a threshold to define events using an eccentricity index alone is problematic and needs to be adapted to specific site conditions. For this reason, we recommend always combining the application of an eccentricity index with a detailed visual (anatomical) inspection to check for the occurrence of reaction wood.
Wood anatomical features may be visible on the microscopic as well as on the macroscopic scale. W... more Wood anatomical features may be visible on the microscopic as well as on the macroscopic scale. While the former can often be quantified by detailed wood anatomical analyses, the latter are often treated as qualitative features or as binary variables (present/absent). Macroscopic tree-ring features can be quantified in terms of frequency, intensity, or classified according to their position within a tree ring, like intra-annual density variations (IADFs) in conifers or frost rings in earlywood or latewood. Although some of these tree-ring features, like e.g. missing rings or IADFs are often seen as anomalies, hampering dendrochronologists to perform proper crossdating of tree-ring series, many of these properties are formed under extreme environmental stress or heavy impact, and could mark these extreme events by the manifestation in the wood anatomical structures throughout the lifespan of trees. The described tree-ring features form discrete time-series of extreme events. For example, flood rings may be marked by lunar-shaped earlywood vessels or enlarged latewood vessels in ring-porous oaks. White earlywood rings and light rings indicate reduced cell wall thickness and lignification occurring in very cold years. Frost rings result from cambial cell death during abrupt cooling events in the growing season. Missing rings and IADFs are mainly caused by drought events. Characteristic variations in earlywood vessel size, shape, or number in ring-porous oak species are markers for flood events, defoliation, heat stress, or drought. Traumatic resin ducts may be triggered by a range of biotic or environmental stressors, including wounding, fires or mechanical factors. Reaction wood is indicative of mechanical stress, often related to geomorphic events. In many cases anatomical responses are unspecific and may be caused by different stressors or extreme events. Additionally, the sensitivity of trees to form such features may vary between species, or between life stages within one species. We critically evaluate the indicative value of different wood anatomical tree-ring features for environmental reconstructions.
The type of samples most commonly used in dendro sciences are increment cores of conifers. These ... more The type of samples most commonly used in dendro sciences are increment cores of conifers. These cores allow for an easy determination and measurement of ring-width variations over long time periods. For wood anatomical analyses, the cores have to be split into pieces to enable the preparation of high quality micro sections for detailed measurements of cell properties. A major drawback of this procedure is the fact that it is labor intensive and time consuming. We present a new technique enabling the preparation of micro sections of entire increment cores up to a length of 40 cm. For that purpose we combined standard wood-anatomical techniques with the application of Mowiol glue and common Tesa tape. We tested the introduced method on increment cores of Larix decidua Mill. sampled years ago for ring-width analyses to reanalyze them on a microscopic level. The ability to cut these long sections will tremendously reduce the time needed to prepare micro sections. This is of special interest for wood anatomical image analyses of cores used before to create long ring-width chronologies for any kind of environmental reconstructions.
Dendroecological research uses information stored in tree rings to understand how single trees an... more Dendroecological research uses information stored in tree rings to understand how single trees and even entire forest ecosystems responded to environmental changes and to finally reconstruct such changes. This is done by analyzing growth variations back in time and correlating various plant-specific parameters to (for example) temperature records. Integrating wood anatomical parameters in these analyses would strengthen reconstructions, even down to intra-annual resolution. We therefore present a protocol on how to sample, prepare, and analyze wooden specimen for common macroscopic analyses, but also for subsequent microscopic analyses. Furthermore we introduce a potential solution for analyzing digital images generated from common small and large specimens to support time-series analyses. The protocol presents the basic steps as they currently can be used. Beyond this, there is an ongoing need for the improvement of existing techniques, and development of new techniques, to record and quantify past and ongoing environmental processes. Traditional wood anatomical research needs to be expanded to include ecological information to this field of research. This would support dendro-scientists who intend to analyze new parameters and develop new methodologies to understand the short and long term effects of specific environmental factors on the anatomy of woody plants.
Based on the Reichert Om E microtome a more sophisticated, nevertheless solely
mechanically opera... more Based on the Reichert Om E microtome a more sophisticated, nevertheless solely mechanically operated microtome was developed enabling to section specimens of various forms and sizes. The materials used and the special construction of the microtome resulted in a higher stability of the moving parts whilst simultaneously reducing weight. As a result of the high stability of the sledge guidance, bigger sections can be cut enabling more detailed analyses of anatomical structures within plant stems, roots or branches as well as their variation back in time. Consequently, wood anatomical parameters can be integrated more easily in time-series analyses supporting the aims of a quantitative wood ecology.
Exposed roots have been used in Dendrogeomorphology since the 1960s to determine erosion rates. T... more Exposed roots have been used in Dendrogeomorphology since the 1960s to determine erosion rates. This was done by using the root axis as the relative position of the former soil layer and then relating this measure to the age of the root in order to quantify the amount of soil erosion over time. Recently, wood anatomical research revealed the possibility of determining the first year of exposure of roots due to specific anatomical changes within the respective annual ring. As a consequence, using exposed roots that are still in contact to the soil surface, it is possible to reconstruct the size and position of the root at the time of exposure. Consequently, a new equation is presented to calculate the thickness of the eroded soil layer allowing a detailed reconstruction of erosion rates. The technique also helps to determine if the root was exposed by erosional processes or just by its ongoing secondary growth without any erosion involved.
Die Bilder grossflächig brauner Laubbäume in weiten Teilen der Schweiz sowie Zentraleuropas im Fr... more Die Bilder grossflächig brauner Laubbäume in weiten Teilen der Schweiz sowie Zentraleuropas im Frühsommer 2018 sind uns noch sehr präsent. Diese um rund drei Monate verfrühte Herbstverfärbung der Wälder war das Resultat der extre-men Hitze und langanhaltenden Dürre. Auch wenn das Ausmass und die Sichtbar-keit der Schäden in Wald und Landwirtschaft 2018 ausserordentlich waren, so stel-len wir eine Häufung von solchen extremen Hitze-und Trockenjahren (2003, 2011 und 2015) fest. Laut dem neuesten Klimabericht für die Schweiz muss davon aus-gegangen werden, dass Hitze-und Dürreperioden in Zukunft noch häufiger auf-treten dürften. Was heisst dies nun für unsere Wälder? Wie viel Trockenheit kön-nen sie ertragen? Wir diskutieren diese Fragen anhand von Daten aus verschiede-nen Monitoringansätzen und zeigen auf, dass die verschiedenen Waldökosysteme sehr unterschiedlich reagieren und die zukünftige Dynamik unserer Wälder von der Kombination und dem zeitlichen Auftreten von Trockenheit und anderen Wetterextremen abhängen wird.
The efficiency of water use and transport are among the main factors affecting competitiveness, g... more The efficiency of water use and transport are among the main factors affecting competitiveness, growth, and distribution of trees under warming climate. The phenotypical and genetic plasticity of tree populations is considered as an indicator of their adaptive capacity under changing environment. Climatic changes are expected to affect growth of Scots pine (Pinus sylvestris L.), and selection of reproductive material among the populations suitable for future climates has been advised for sustaining productivity of stands. In this regard, provenance trials can serve as source of comprehensive information about growth plasticity and climate-growth interactions of diverse populations. Quantitative wood anatomy can provide detailed information about xylo-genesis and factors affecting it, which are crucial for long-term predictions. Wood anatomy of two top-(Gustrow and Rytel), two low-performing (Eibenstock and Dippoldiswalde), and one local (Kalsnava) provenances of Scots pine from the eastern Baltic region growing in three provenance trials in Latvia was studied using mixed models, accounting for the experimental design, as well as using the time-series approach. Provenance had a significant effect on the studied wood anatomical proxies, indicating genetic adaptation of xylogenesis. The top-performing provenances, which originated from warmer and drier conditions, had tracheids with larger lumens and thinner walls, thus indicating adaptation to water deficit. The top-performing Rytel provenance showed the highest phenotypical plasticity of lumen cross-section area and cell wall thickness of stemwood tracheids. The studied low-performing provenances, which originated from the Orr Mountains, had tracheids with thicker wall and smaller lumens, likely to ensure mechanical durability. The local provenance showed intermediate values of the studied wood anatomical proxies. The effect of provenance on wood anatomical proxies showed some variations among the trials, which differed by continentality, likely due to ecological transfer distance. The studied anatomical proxies were affected by weather conditions prior and during formation of a tree ring, yet these relationships differed by trial and provenance. In general, wood anatomy of earlywood was affected by temperature in the dormant period and beginning of summer, as well as precipitation in the end of the previous vegetation period. Proxies of latewood showed correlation with temperature (negative) and precipitation (po-sitive) in summer, suggesting response to the availability of water. Considering the observed relationships, the top-performing provenances, particularly Rytel, have a high potential to sustain productivity of stands within the region in the future.
Plants essentially contribute to the strength of soil and, in particular, steep slopes susceptibl... more Plants essentially contribute to the strength of soil and, in particular, steep slopes susceptible to erosion and shallow landslides. The corresponding functions of vegetation significantly control processes above and below ground such as interception , evapo-transpiration, soil aggregation and root reinforcement. Either way, they are all correlated with plant growth. Consequently, in order to unfold their soil stabilising potential, the plants must grow and sustainably survive. However, what sounds so obvious is anything but given under the often hostile conditions dominating on bare and steep slopes. This is exactly the point where mycorrhizal fungi come into play, known to improve the plants' ability to overcome periods governed by strongly (growth) limiting factors. Within this scope, numerous investigations have been conducted in order to understand and quantify mycorrhizal effects on different plant and soil functions related to eco-engineering and, particularly, to soil and slope stability. Results on plant growth and survival as well as on soil aggregation and slope stabilisation are presented and discussed from a mycorrhizal perspective.
The annual growth and wood characteristics of tree species at southern Mediterranean countries, a... more The annual growth and wood characteristics of tree species at southern Mediterranean countries, and its relationship with climate variables are recently two important topics for the researchers in this region. Although Moringa peregrina (Forssk.) Fiori is a key species in Africa due to its medicinal and economic values (e.g. as fuel, food and water purifier), little is known about its annual growth or its response to climate variables. In this study, we analyze its dendrochronological potential, macroscopic and microscopic wood structure, and correlation with climate. Wood discs were collected from two desert sites in Egypt: Saint Catherine (SC) and Hurghada (HG). Wood discs and micro-slides were prepared, and the distinctness and pattern of rings, vessels, and ray structure were examined microscopically. The ring boundaries of M. peregrina were distinct and marked by thick-walled and flattened fibers. For the HG site, the resulting ring-width chronology spans 16 years, from 2001 to 2016. A significant positive relationship was found between tree growth at HG and precipitation prior to the vegetation period (January-March). April temperature of the year prior to growth had a significant positive relationship with M. peregrina growth. In contrast, April and May-August temperatures of the current growing season had a significant negative relationship with tree growth. We could not develop a chronology for M. peregrina at SC site due to the presence of growth anomalies in the collected wood discs from the site. Consequently, we did not get a clear picture on the climate-annual growth relationship for M. peregrina trees at this site. At SC, M. peregrina trees respond to stressful environmental conditions by adjusting their anatomical structure to produce a high number of small vessels. Moreover, there was spatial variability in the architecture of ray parenchyma that reflected the degree of stress in both sites. The results of this study improve our understanding of the growth-climate relationship in subtropical trees and the potential role of ray parenchyma in stressed environments.
A R T I C L E I N F O Keywords: Ailanthus altissima (tree of heaven) Tree-ring Climate growth rel... more A R T I C L E I N F O Keywords: Ailanthus altissima (tree of heaven) Tree-ring Climate growth relationship Vessel lumen area Wood anatomy Invasive tree A B S T R A C T Knowledge on the ecology of tree species in both their native and introduced range can increase the understanding of their successful establishment and spread outside the native range. Here, we analysed radial growth patterns of Ailanthus altissima (Mill.) Swingle in two sites in its native range in eastern China and in two sites in the introduced range in southern Switzerland, where it started to disperse into forests in the 1950s. Growth rates were similar despite lower amounts of growing season precipitation in China. Furthermore, we found negative correlations between annual radial growth and average temperatures in the growing season at the warmest of the four sites, which suggest that radial growth of A. altissima starts to be limited by average growing season temperatures above 21 °C. Regarding wood anatomy, we did not find clear correlations between vessel lumen area and monthly temperature or precipitation at the time of tissue formation in spring. Overall, our results demonstrate that A. altissima has the potential to grow in drier conditions than currently found in Switzerland, which is in line with previous studies.
A spatiotemporal reconstruction of slope movements on the edge of Lake Lucerne near the municipal... more A spatiotemporal reconstruction of slope movements on the edge of Lake Lucerne near the municipality of Horw, canton of Lucerne, is presented. The reconstruction was realized by analyzing growth reactions of beech (Fagus sylvatica L.) and fir (Abies alba Mill.) trees growing on this slope. Before dendrochronological sampling, a detailed geomorphological mapping of the landslide was conducted with the aim to determine the spatial extent of the sliding area. For tree-ring analyses, 124 increment cores from 62 trees were analyzed following standard techniques of dendrogeomorphology. In addition, long micro-sections were prepared from the entire cores to extend the common eccentricity analyses by microscopic determination of the onset of reaction wood in fir and beech. Results clearly show that the area is moving at least since 1948. A significant concentration of events was observed between the years 1990 and 2000 as well as after 2006. The definition of a threshold to define events using an eccentricity index alone is problematic and needs to be adapted to specific site conditions. For this reason, we recommend always combining the application of an eccentricity index with a detailed visual (anatomical) inspection to check for the occurrence of reaction wood.
Wood anatomical features may be visible on the microscopic as well as on the macroscopic scale. W... more Wood anatomical features may be visible on the microscopic as well as on the macroscopic scale. While the former can often be quantified by detailed wood anatomical analyses, the latter are often treated as qualitative features or as binary variables (present/absent). Macroscopic tree-ring features can be quantified in terms of frequency, intensity, or classified according to their position within a tree ring, like intra-annual density variations (IADFs) in conifers or frost rings in earlywood or latewood. Although some of these tree-ring features, like e.g. missing rings or IADFs are often seen as anomalies, hampering dendrochronologists to perform proper crossdating of tree-ring series, many of these properties are formed under extreme environmental stress or heavy impact, and could mark these extreme events by the manifestation in the wood anatomical structures throughout the lifespan of trees. The described tree-ring features form discrete time-series of extreme events. For example, flood rings may be marked by lunar-shaped earlywood vessels or enlarged latewood vessels in ring-porous oaks. White earlywood rings and light rings indicate reduced cell wall thickness and lignification occurring in very cold years. Frost rings result from cambial cell death during abrupt cooling events in the growing season. Missing rings and IADFs are mainly caused by drought events. Characteristic variations in earlywood vessel size, shape, or number in ring-porous oak species are markers for flood events, defoliation, heat stress, or drought. Traumatic resin ducts may be triggered by a range of biotic or environmental stressors, including wounding, fires or mechanical factors. Reaction wood is indicative of mechanical stress, often related to geomorphic events. In many cases anatomical responses are unspecific and may be caused by different stressors or extreme events. Additionally, the sensitivity of trees to form such features may vary between species, or between life stages within one species. We critically evaluate the indicative value of different wood anatomical tree-ring features for environmental reconstructions.
The type of samples most commonly used in dendro sciences are increment cores of conifers. These ... more The type of samples most commonly used in dendro sciences are increment cores of conifers. These cores allow for an easy determination and measurement of ring-width variations over long time periods. For wood anatomical analyses, the cores have to be split into pieces to enable the preparation of high quality micro sections for detailed measurements of cell properties. A major drawback of this procedure is the fact that it is labor intensive and time consuming. We present a new technique enabling the preparation of micro sections of entire increment cores up to a length of 40 cm. For that purpose we combined standard wood-anatomical techniques with the application of Mowiol glue and common Tesa tape. We tested the introduced method on increment cores of Larix decidua Mill. sampled years ago for ring-width analyses to reanalyze them on a microscopic level. The ability to cut these long sections will tremendously reduce the time needed to prepare micro sections. This is of special interest for wood anatomical image analyses of cores used before to create long ring-width chronologies for any kind of environmental reconstructions.
Dendroecological research uses information stored in tree rings to understand how single trees an... more Dendroecological research uses information stored in tree rings to understand how single trees and even entire forest ecosystems responded to environmental changes and to finally reconstruct such changes. This is done by analyzing growth variations back in time and correlating various plant-specific parameters to (for example) temperature records. Integrating wood anatomical parameters in these analyses would strengthen reconstructions, even down to intra-annual resolution. We therefore present a protocol on how to sample, prepare, and analyze wooden specimen for common macroscopic analyses, but also for subsequent microscopic analyses. Furthermore we introduce a potential solution for analyzing digital images generated from common small and large specimens to support time-series analyses. The protocol presents the basic steps as they currently can be used. Beyond this, there is an ongoing need for the improvement of existing techniques, and development of new techniques, to record and quantify past and ongoing environmental processes. Traditional wood anatomical research needs to be expanded to include ecological information to this field of research. This would support dendro-scientists who intend to analyze new parameters and develop new methodologies to understand the short and long term effects of specific environmental factors on the anatomy of woody plants.
Based on the Reichert Om E microtome a more sophisticated, nevertheless solely
mechanically opera... more Based on the Reichert Om E microtome a more sophisticated, nevertheless solely mechanically operated microtome was developed enabling to section specimens of various forms and sizes. The materials used and the special construction of the microtome resulted in a higher stability of the moving parts whilst simultaneously reducing weight. As a result of the high stability of the sledge guidance, bigger sections can be cut enabling more detailed analyses of anatomical structures within plant stems, roots or branches as well as their variation back in time. Consequently, wood anatomical parameters can be integrated more easily in time-series analyses supporting the aims of a quantitative wood ecology.
Exposed roots have been used in Dendrogeomorphology since the 1960s to determine erosion rates. T... more Exposed roots have been used in Dendrogeomorphology since the 1960s to determine erosion rates. This was done by using the root axis as the relative position of the former soil layer and then relating this measure to the age of the root in order to quantify the amount of soil erosion over time. Recently, wood anatomical research revealed the possibility of determining the first year of exposure of roots due to specific anatomical changes within the respective annual ring. As a consequence, using exposed roots that are still in contact to the soil surface, it is possible to reconstruct the size and position of the root at the time of exposure. Consequently, a new equation is presented to calculate the thickness of the eroded soil layer allowing a detailed reconstruction of erosion rates. The technique also helps to determine if the root was exposed by erosional processes or just by its ongoing secondary growth without any erosion involved.
Fritz H. Schweingruber, pioneer of tree-ring research and wood anatomy, passed away on January 7,... more Fritz H. Schweingruber, pioneer of tree-ring research and wood anatomy, passed away on January 7, 2020, at the age of nearly 84. Fritz was born on February 29, 1936, in Krauchthal (Canton Bern, Switzerland). From 1956 to 1965, he was a primary school teacher and an organist. Although he liked teaching, he discovered his curiosity for botany and archaeology. This was the beginning of what turned out to be an outstanding scientific career. He enrolled at University of Bern and took classes in botany, zoology, geology and preand early history. In 1972, he obtained his doctorate in botany from the University of Basel, where he was appointed professor in 1976. Since 1971, Fritz was based at the Swiss Federal Institute for Forest, Snow and Landscape Research WSL (Birmensdorf, Switzerland), where he established one of Europe’s first tree-ring labs, which developed into one of the largest worldwide. Among the lasting contributions to our field are more than 200 journal articles and 39 books, amongwhich include (1) “Tree Rings: Basics and Applications of Dendrochronology” (Schweingruber 1988) and “Tree Rings and Environment Dendroecology” (Schweingruber 1996), which are classics, (2) the northern hemispheric network of tree-ring density data from 350 sites established with colleagues from UK and Russia, which is an important backbone of the ITRDB, (3) a worldwide unique collection of anatomical microsections of 5000 tree, shrub, herb and graminoid species, (4) the “International Dendroecological Fieldweek” initiated in 1986, which inspired a number of courses worldwide such as the continuing “European Dendroecological Fieldweek”, and (5) the international course on “Wood Anatomy & Tree-Ring Ecology” running since 2001. These and further milestones of Fritz’ extraordinary life are summarized in more detail in other obituaries (Büntgen et al. 2020, Crivellaro and Gärtner 2020, Urbinati et al. 2020). Colleagues and friends at the WSL as well as in the scientific community experienced Fritz as a very curious, dedicated and charismatic person. The following thoughtful recollections from our group, mostly from Fritz’ last years as a retired member of our research group, illustrate this.
The use of automated techniques for image analysis of microscopic wood specimens together with ne... more The use of automated techniques for image analysis of microscopic wood specimens together with new procedures for the preparation of stained xylem tissue support the use of quantitative wood anatomy. These techniques and procedures are especially useful in the studies of retrospective analysis of xylem phenology, reaction(s) of trees to stressful conditions of growth, or reconstruction of long-term growth trends. The unresolved technical problems during the digitalization of cross sections from entire increment cores were stabilization and precise shifting of long microscopic specimens onto the optical microscope stage. For this reason, we have developed a long slide holder for microscope stages in two versions: the basic one allowing stabilization and manual shifting, and the advanced one for stabilization and mechanical shifting. Both versions of the adapter speed up the work with long slides, improving the quality of panoramic images of microscopic specimens.
... A preliminary study Ellen Gers, Nicole Florin, Holger Gartner, Thomas Glade, Richard Dikau an... more ... A preliminary study Ellen Gers, Nicole Florin, Holger Gartner, Thomas Glade, Richard Dikau and Fritz H, Schweingruber with 2 photos, 7 Figures and 2 tables Summary. ... Fantucci, R. (1999): Dcndro geo morphology in landslide analysis. - In: Casale, R. & Margottini, С. ...
During recent decades, stable oxygen isotopes derived from tree-ring cellulose (δ18OTRC) have bee... more During recent decades, stable oxygen isotopes derived from tree-ring cellulose (δ18OTRC) have been frequently utilised as the baseline for palaeoclimatic reconstructions. In this context, numerous studies take advantage of the high sensitivity of trees close to their ecological distribution limit (high elevation or high latitudes). However, this increases the chance that indirect climatic forces such as cold ground induced by permafrost can distort the climate-proxy relationship. In this study, a tree stand of sub-alpine larch trees (Larix decidua Mill.) located in an inner alpine dry valley (Val Bever), Switzerland, was analysed for its δ18OTRC variations during the last 180 years. A total of eight L. decidua trees were analysed on an individual base, half of which are located on verified sporadic permafrost lenses approximately 500 m below the expected lower limit of discontinuous permafrost. The derived isotope time series are strongly dependent on variations in summer temperatur...
... thank the participants of the meeting, who contributed to a lively and enthusiastic exchange ... more ... thank the participants of the meeting, who contributed to a lively and enthusiastic exchange of ideas, and Marjolein Mullen (Utrecht ... wood reveals a systematic recurring carbon isotope pattern SECTION 5 PALAEO-ENVIRONMENTS U. Sass-Klaassen, M. Kooistra, L. Kooistra, E ...
Introduction In the context of changing magnitudes and frequencies of natural hazards such as deb... more Introduction In the context of changing magnitudes and frequencies of natural hazards such as debris flows or snow avalanches caused by the current climate change a detailed understanding of tree reactions on growth stresses induced through different geomorphological forces is desirable. Macroscopic changes in wood formation (growth variations in trees) as reaction to external impacts have often been used for dating catastrophic events. Frequently, conifers have been used in dendrogeomorphology for reconstructions of geomorphic processes while similar studies with broadleaf species are rather rare. However, broadleaf species often occur in mixed forests together with conifer trees and are sometimes the dominant species in lower elevations. Furthermore, broadleaf species possess a more complex wood anatomy and offer structural features for further analysis not found in coniferous wood. Hence, it is essential to also examine the reaction wood of broadleaf species in more detail in order to enable dendrogeomorphological studies in vegetation zones dominated by them. It is suggested here that the additional application of wood anatomical techniques can harvest supplementary information about type, size and intensity of past hazardous impacts on tree growth. Long-term growth experiments imitating typical impacts of different geomorphic events are being conducted and their wood anatomical reactions monitored in order to study the likely varying reactions to a range of mechanical stresses, and first results are presented.
<p>Tree mortality due to climate change and particularly drought is a globally observed iss... more <p>Tree mortality due to climate change and particularly drought is a globally observed issue and has been studied widely. However, the underlying physiological mechanisms are still not fully understood. One approach to assess the drivers of drought-induced mortality is to retrospectively investigate predisposing factors that have led to tree death by utilizing tree rings. Here we combine annual stem growth, and stable carbon and oxygen isotopes (&#120575;<sup>13</sup>C and &#120575;<sup>18</sup>O) in tree rings of recently died and living trees of two species, drought tolerant Pinus sylvestris and drought sensitive Fagus sylvatica, in the Rhone Valley (Valais), the driest part of Switzerland.</p><p>Irrespective of specific drought tolerance, growth patterns of now-dead and living trees were significantly different in both species. Now-dead trees showed higher growth rates than living trees, for at least half of their life span. In the last two decades this pattern was reversed and growth of now-dead trees was at a lower level compared to living trees. In this recent time period, &#120575;<sup>18</sup>O records of now-dead trees of both species showed a distinct decrease, while no systematic difference was found in the tree-ring &#120575;<sup>13</sup>C records of now-dead and living trees. Climate correlation analysis revealed that stem growth of now-dead trees was more sensitive to climate compared to living trees and that the relationship between isotope-derived leaf gas exchange and climate weakened in the late period prior to death.</p><p>Our findings suggest that now-dead trees followed a more conservative water-use strategy in their declining phase. Decreasing &#160;values and weakened relationships to climate indicate a reduction in stomatal conductance, accompanied by reduced photosynthetic activity, since the ratio of photosynthesis to stomatal conductance remained unchanged. Overall, our results suggest a combination of hydraulic failure and carbon starvation as initiators of tree death at our study sites, probably in different stages of tree life. It is obvious that recent climate conditions already strongly affected the trees, such that in a future environment negative effects will most likely increase.</p>
Compression wood (CW) is a common tissue present in the trunk, branches and roots of mechanically... more Compression wood (CW) is a common tissue present in the trunk, branches and roots of mechanically stressed coniferous trees. Its main role is to increase the mechanical strength and regain the vertical orientation of a leaning stem. Compression wood is thought to influence the climate signal in different tree-ring measures. Hence trees containing CW are mostly excluded from tree-ring studies reconstructing past climate variability. There is a large gap of systematic work testing the potential effect of CW on the strength of the climate signal in different tree-ring parameters, especially stable isotope records. Here we test for the first time the effect of CW contained in montane Norway spruce (Picea abies L. Karst) on both δ13C and δ18O tree-ring cellulose records by analyzing compression and opposite wood radii from several disturbed trees together with samples from undisturbed reference trees. We selected four trees tilted by geomorphic processes that were felled by wind and four undisturbed reference trees in the Tatra Mountains, Poland. We qualitatively classified the strength of CW using wood cell anatomical characteristics (tracheid shape, cell wall thickness and presence of intercellular spaces). Then we developed tree-ring width and δ13C and δ18O chronologies from the CW radii, from the opposite radii of the tilted trees and from the reference radii. We tested the effect of CW on tree-ring cellulose δ13C and δ18O variability and on the climate signal strength. We found only minor differences in the means of δ13C and δ18O of compression (δ13C: −22.81‰, δ18O: 28.29‰), opposite (δ13C: −23.02‰; δ18O: 28.05‰) and reference (δ13C: −22.78‰; δ18O: 27.61‰) radii. The statistical relationships between climate variables, δ13C and δ18O, remained consistent among all chronologies. Our findings suggest that moderately tilted trees containing CW can be used to reconstruct past geomorphic activity and for stable isotope-based dendroclimatology.
Die Bilder grossflächig brauner Laubbäume in weiten Teilen der Schweiz sowie Zentraleuropas im Fr... more Die Bilder grossflächig brauner Laubbäume in weiten Teilen der Schweiz sowie Zentraleuropas im Frühsommer 2018 sind uns noch sehr präsent. Diese um rund drei Monate verfrühte Herbstverfärbung der Wälder war das Resultat der extremen Hitze und langanhaltenden Dürre. Auch wenn das Ausmass und die Sichtbarkeit der Schäden in Wald und Landwirtschaft 2018 ausserordentlich waren, so stellen wir eine Häufung von solchen extremen Hitze- und Trockenjahren (2003, 2011 und 2015) fest. Laut dem neuesten Klimabericht für die Schweiz muss davon ausgegangen werden, dass Hitze- und Dürreperioden in Zukunft noch häufiger auftreten dürften. Was heisst dies nun für unsere Wälder? Wie viel Trockenheit können sie ertragen? Wir diskutieren diese Fragen anhand von Daten aus verschiedenen Monitoringansätzen und zeigen auf, dass die verschiedenen Waldökosysteme sehr unterschiedlich reagieren und die zukünftige Dynamik unserer Wälder von der Kombination und dem zeitlichen Auftreten von Trockenheit und andere...
Recently, the Mediterranean region has experienced unprecedented drought. Climate models predict ... more Recently, the Mediterranean region has experienced unprecedented drought. Climate models predict an increase in drought frequency and duration. Therefore, quantifying the response of Mediterranean plants to drought is important. We contrasted wood anatomy and dendroecological features of a Mediterranean shrub, Arbutus unedo, at a xeric and a mesic site on the Italian island of Elba. Radial microsections of Arbutus unedo were stained, described, and crossdated. Annual ring widths of radial microsections were measured and compared with regional temperature and precipitation. False rings are common and distinguishable from true annual ring boundaries only by viewing radial microsections under high magnification. False ring formation was more common at the xeric site and was caused by below average rainfall in late summer (xeric site) and below average rainfall and high temperatures in spring and summer (mesic site). Given the predictions for increased drought, plants currently growing at mesic sites will likely adopt the growth patterns of plants currently growing at xeric sites. Thus, late summer precipitation will limit growth rates for woody plants. Arbutus unedo demonstrated its dendroecological value and future work on climate initiated shifts in Mediterranean vegetation should take advantage of the potential found in annual ring records of shrubs
This volume contains 30 short papers which summarise the main subjects of talks and posters prese... more This volume contains 30 short papers which summarise the main subjects of talks and posters presented at the seventh TRACE (Tree Rings in Archaeology, Climatology and Ecology) conference organized by Ireneusz Malik, Ryszard J. Kaczka and Piotr Owczarek and held in Zakopane, Poland on April 27th - 30th, 2008.
In mountain environments superficial slope failures on coarse grained, vegetation-free slopes are... more In mountain environments superficial slope failures on coarse grained, vegetation-free slopes are common processes and entail a certain risk for humans and socio-economic structures. Eco-engineering measures can be applied to mitigate slope instabilities. In this regard, limited plant survival and growth can be supported by mycorrhizal inoculation, which was successfully tested in laboratory studies. However, related studies on a field scale are lacking. Furthermore, mycorrhizae are known to enhance soil aggregation, which is linked to soil physics such as shear strength, and hence it is a useful indicator for near-surface soil/slope stability. The overall objective of our contribution was to test whether mycorrhizal inoculation can be used to promote eco-engineering measures in steep alpine environments based on a five-year field experiment. We hypothesized that mycorrhizal inoculation (i) enhances soil aggregation, (ii) stimulate plant survival and fine root development, (iii) eff...
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allow for an easy determination and measurement of ring-width variations over long time periods. For
wood anatomical analyses, the cores have to be split into pieces to enable the preparation of high quality
micro sections for detailed measurements of cell properties. A major drawback of this procedure is the
fact that it is labor intensive and time consuming. We present a new technique enabling the preparation of
micro sections of entire increment cores up to a length of 40 cm. For that purpose we combined standard
wood-anatomical techniques with the application of Mowiol glue and common Tesa tape. We tested the
introduced method on increment cores of Larix decidua Mill. sampled years ago for ring-width analyses to
reanalyze them on a microscopic level. The ability to cut these long sections will tremendously reduce the
time needed to prepare micro sections. This is of special interest for wood anatomical image analyses of
cores used before to create long ring-width chronologies for any kind of environmental reconstructions.
environmental changes and to finally reconstruct such changes. This is done by analyzing growth variations back in time and correlating various
plant-specific parameters to (for example) temperature records. Integrating wood anatomical parameters in these analyses would strengthen
reconstructions, even down to intra-annual resolution. We therefore present a protocol on how to sample, prepare, and analyze wooden
specimen for common macroscopic analyses, but also for subsequent microscopic analyses. Furthermore we introduce a potential solution for
analyzing digital images generated from common small and large specimens to support time-series analyses. The protocol presents the basic
steps as they currently can be used. Beyond this, there is an ongoing need for the improvement of existing techniques, and development of new
techniques, to record and quantify past and ongoing environmental processes. Traditional wood anatomical research needs to be expanded to
include ecological information to this field of research. This would support dendro-scientists who intend to analyze new parameters and develop
new methodologies to understand the short and long term effects of specific environmental factors on the anatomy of woody plants.
mechanically operated microtome was developed enabling to section specimens
of various forms and sizes. The materials used and the special construction of the
microtome resulted in a higher stability of the moving parts whilst simultaneously
reducing weight. As a result of the high stability of the sledge guidance, bigger
sections can be cut enabling more detailed analyses of anatomical structures
within plant stems, roots or branches as well as their variation back in time.
Consequently, wood anatomical parameters can be integrated more easily in
time-series analyses supporting the aims of a quantitative wood ecology.
allow for an easy determination and measurement of ring-width variations over long time periods. For
wood anatomical analyses, the cores have to be split into pieces to enable the preparation of high quality
micro sections for detailed measurements of cell properties. A major drawback of this procedure is the
fact that it is labor intensive and time consuming. We present a new technique enabling the preparation of
micro sections of entire increment cores up to a length of 40 cm. For that purpose we combined standard
wood-anatomical techniques with the application of Mowiol glue and common Tesa tape. We tested the
introduced method on increment cores of Larix decidua Mill. sampled years ago for ring-width analyses to
reanalyze them on a microscopic level. The ability to cut these long sections will tremendously reduce the
time needed to prepare micro sections. This is of special interest for wood anatomical image analyses of
cores used before to create long ring-width chronologies for any kind of environmental reconstructions.
environmental changes and to finally reconstruct such changes. This is done by analyzing growth variations back in time and correlating various
plant-specific parameters to (for example) temperature records. Integrating wood anatomical parameters in these analyses would strengthen
reconstructions, even down to intra-annual resolution. We therefore present a protocol on how to sample, prepare, and analyze wooden
specimen for common macroscopic analyses, but also for subsequent microscopic analyses. Furthermore we introduce a potential solution for
analyzing digital images generated from common small and large specimens to support time-series analyses. The protocol presents the basic
steps as they currently can be used. Beyond this, there is an ongoing need for the improvement of existing techniques, and development of new
techniques, to record and quantify past and ongoing environmental processes. Traditional wood anatomical research needs to be expanded to
include ecological information to this field of research. This would support dendro-scientists who intend to analyze new parameters and develop
new methodologies to understand the short and long term effects of specific environmental factors on the anatomy of woody plants.
mechanically operated microtome was developed enabling to section specimens
of various forms and sizes. The materials used and the special construction of the
microtome resulted in a higher stability of the moving parts whilst simultaneously
reducing weight. As a result of the high stability of the sledge guidance, bigger
sections can be cut enabling more detailed analyses of anatomical structures
within plant stems, roots or branches as well as their variation back in time.
Consequently, wood anatomical parameters can be integrated more easily in
time-series analyses supporting the aims of a quantitative wood ecology.