WSL Tree-Ring Laboratory

 

The Swiss Federal Institute for Forest, Snow and Landscape Research, better known as WSL (which stands for Wald, Schnee, und Landschaft meaning Forest, Snow, and Landscape) houses the largest dendrochronology laboratory in Europe.

WSL is a large research consortium that has offices in Birmensdorf, Davos, Lausanne, Bellinzona, and Sion with Birmensdorf being the largest center. They divide themselves into 10 different research units (Forest Resources and Management, Forest Dynamics, Forest Soils and Biogeochemistry, Landscape Dynamics, Mountain Hydrology and Mass Movements, Community Ecology, Snow Avalanches and Prevention, Snow and Permafrost, Biodiversity and Conservation Biology, and Economics and Social Sciences). While dendrochronology could almost come under any of these headings, it is housed in the Landscape Dynamics research unit where there are five subgroups (Dendroclimatology, Dendroecology, Dynamic Macroecology, Landscape Ecology, and Remote Sensing). Dendrochronology is housed in the first two subgroups which are led by Dr. David Frank and Dr. Ulf Büntgen, respectively. In these two groups there are 44 individuals including 11 with doctorate degrees.

Dendroclimatology

Dr. David Frank - teamleader

Dr. Kerstin Treydte - scientific staff member

Daniel Nievergelt - technical staff member

Anne Verstege
1 visiting scientist

4 PhD students

1 master student

1 temporary employee

2 trainees

Dendroecology

PD Dr. Ulf Büntgen - teamleader

Prof. Dr. Fritz Schweingruber - visiting scientist

Dr. Paolo Cherubini - senior scientist

Dr. Patrick Fonti - scientific staff member

Dr. Holger Gärtner - scientific staff member

Dr. Bettina Wagner - scientific staff member

Dr. Georg von Arx - scientific staff member

Dr. Bako Harisoa Ravaomanalina - visiting scientist

Dr. Juan Diego Galván Candela - Postdoc

Loïc Schneider
5 visiting scientists

5 PhD students

6 master students

3 trainees

1 temporary employee

1 civil service employee

1 guest

From front left Dejan Stojanović, David Frank, Fritz Schweingruber, Ulf Büntgen, Dario Martin-Benito, myself, and Paolo Cherubini. We were also later joined by Patrick Fonti and Volodymyr Trotsiuk. I would like to thank Dejan Stojanović for sharing this photograph. I downloaded about 1300 pictures to my Asus Tablet and the next morning, it would not turn on. The company cleared the hard drive while replacing the motherboard so these are the only photos I have from my visit. This has left me with no original photos of the WSL Laboratory and its lead scientists besides what is included in this blog.

One of the very nice things about WSL is the proximity of so many forest, soil, and landscape researchers. If one has questions about soil mycology as it relates to tree growth and insect outbreaks (as I do), there would be colleagues to talk to just down the hall. They also have a nice library of forestry literature and are connected to a library consortium from which any requested items will be delivered within 24 hours from across Switzerland. This seems like a very intensive and productive space to conduct research.

My visit was far too short, but I had a chance to talk with most of the lead scientists although Dr. Kerstin Treydte was away in Australia on sabbatical (see Treydte et al. 2006). I had the chance to see Dr. Schweingruber's office and lab where he has developed so many books that introduce the field of dendrochronology (Schweingruber 1988, 1996) of wood anatomy from woody stems (from shrubs to trees) around the world (e.g. Schweingruber 1990). It was great to talk to him after the many years since I saw him last. I had the chance to see his original densitometry sections and plots in the WSL archives that where the basis for much of the work in his papers (Schweingruber et al. 1979, Schweingruber et al. 1988). I also got to see the wood archives of his samples from the northern Eurasian transects (Schweingruber and Briffa 1996).

I had a good conversation with Dr. Ulf Büntgen and got to hear about his work with annual banding on ibex horns (Büntgen et al. 2014), truffle mushrooms (Büntgen et al. 2011), and hear some about his work with long-term climate reconstructions in Europe that also consider human susceptibility to these climate changes (Büntgen et al. 2005, Büntgen et al. 2006, Büntgen et al. 2011).

Dr. David Frank was kind enough to host me at his house for a few days during my visit. Dr. Frank was a group leader at the Tasmanian fieldweek where I first got to know him better after meeting him at Ameridendro, WorldDendro, and other conferences. His work in long-term climate reconstruction and ensemble reconstruction has been interesting to follow (Frank and Esper 2005a, Frank and Esper 2005b, Frank et al. 2007a, Frank et al. 2007b, Frank et al. 2010). I really enjoyed his presentation at WorldDendro 2014 on the multiple causes for what has been called the Divergence Issue. I also enjoyed talking to him about a paper that just came out that he co-authored that examines the effect of sampling design on research results in dendrochronology (Nehrbass‐Ahles et al. 2014).

 

It was great to see Dr. Holger Gärtner's microtomes (image is of the full core microtome - photo credit to Holger Gärtner and the WSL http://www.wsl.ch/info/mitarbeitende/gaertner/Microtomes_EN) in action where they were invented (Gärtner and Nievergelt 2010). I would highly recommend the wood anatomy workshop that he teaches with Dr. Fritz Schweingruber and would also recommend purchasing his microtomes. I really like Dr. Gärtner's work with wood anatomy of root to stem transitions (Gärtner et al. 2001, Gärtner 2007). Loïc Schneider has worked with Holger to contribute to the literature using new techniques to prepare micro sections (Schneider and Gärtner 2013).

 

I had met Dr. Georg von Arx at the University of Arizona Laboratory of Tree-Ring Research during my sabbatical visit there in 2008 and heard about the program ROXAS (Photo credit - Patrick Fonti; http://www.wsl.ch/dienstleistungen/produkte/software/roxas/index_EN) that he is developing to measure cell size in angiosperms (von Arx and Dietz 2005). It was great to hear how that work has progressed and now also includes analysis of conifer wood (von Arx and Carrer 2014), and to get an individual tutorial on the program. I am starting to feel that I need to start more work in wood anatomy.

It was good to see Dr. Paolo Cherubini again after much time together at international conferences. He has done interesting and ground-breaking work on fungal effect on tree-growth (Cherubini et al. 2002), exploring tree species with growth rings in the Mediterranean (Cherubini et al. 2003), investigating sampling bias in tree-ring results which is a more popular topic today (Cherubini et al. 1998), some early work in spatiotemporal dynamics from tree-rings (Cherubini et al. 1996), and more recently adding to the discussion about dating the Santorini volcanic eruption (Cherubini et al. 2013, Cherubini et al. 2014). He was very helpful in providing supporting letters for my sabbatical application and partly hosting my stay while at WSL.

Dr. Bako Harisoa Ravaomanalina is a visiting scientist from Madagascar who is working on a book with Dr. Schweingruber showing the wood anatomy of the variety of ebony species. Ebony (Diospyros spp.) is a set of species that is endangered and protected in Madagascar and restricted in global trade. Dr. Harisoa Ravaomanalina works for the Madagascar customs office and uses wood anatomy to identify the wood that is being traded across international borders which is a very interesting use of the science that we do.

 

Dr. Patrick Fonti and Dani Nievergelt took me to the Lötschental Valley in the Alps south of Bern (about a 3 hour car ride each way) for a day trip to open up their long-term phenology monitoring stations at lower elevation. This is an amazing place that is the largest valley in the Alps north of the Rhone River. It was cut off from most of the rest of the world because of the difficult passes to get into the valley until the Lötschbergbahn railway tunnels where completed in 1913. This is still a very remote place with its own customs and culture.

Patrick and Dani are working on a datalogger that is recording sap flow and point dendrometer data at a site in the Lötschental. You can see the orange caution fence wrapped around a tree in the background. Underneath the silver protection are the sap flow monitors that measure temperature difference between two electronic probes that are inserted into the xylem. These stations are powered by local solar panels and all of this gear had to be packed in to the site when they were first established. Every spring they need to be checked out and reactivated and someone visits the sites every week to take phonological short cores from the stem to examine cell development. This data goes back at least seven years so far. This and similar data is helping us understand the development of tree rings and their response to climate (Fonti and García‐González 2004, Fonti et al. 2007, Fonti and García‐González 2008, Fonti et al. 2009, Fonti et al. 2010).

I also got to see the Trephor micro core plug extractor in action that is hammered into the tree, cutting a 2mm micro core that is just a 15-25mm long (you can buy different length core bits depending upon the depth needed). This tool was invented in Italy by Rossi et al. in 2004 (see the entry on the University of Padua for a more extensive description).

The town of Kippel in the Lötschental Valley has also been the location where Dr. Kerstin Treydte and Dr. David Frank have organized the European Dendroecological Fieldweek for a couple of years (total of 25 annual fieldweeks to date). The community house (pictured here with Patrick and Dani walking in front of it) was the location of the labs and sleeping quarters. This European fieldweek was the first of its kinds that Paul Krusic emulated with his North American Dendroecological Fieldweek (23 annual fieldweeks completed). Now we have a South American fieldweek, Asian fieldweek, Middle East fieldweek, and international fieldweeks associated with the WorldDendro conferences.

 

The old houses in the village and the surrounding area are where the samples came from for the Esper et al. (2007) 1,200-year long Larch budmoth reconstruction. It was great to see where these samples came from considering I had just reread this paper two weeks prior to my visit (very good paper). 

 

The local villages in the valley have a tradition called Tschäggättä where some of the inhabitants don animal skins and hand carved masks and portray the evil spirits of winter, throwing soot, kicking snow at visitors, and throwing ones hat on the ground. David Frank had attended this festival last year and showed me some great pictures of the different characters of the village.

Dani Nievergelt along with Dr. David Frank found buried wood in the middle of Zurich in the area of Binz that dates to 12,000-15,000 years before present (based on preliminary radiocarbon dating). WSL has the start of a continuous 15,000 year-long chronology from the work of Klaus Felix Kaiser which Dani has been continuing (Kaiser 1993). Now with the addition of about 200 stems from Binz, they are likely to fill in these gaps and extend this chronology with good sample depth prior to the Holocene to join other long-chronology work by Dr. Richard Guyette and Dr. Michael Stambough in Missouri (Stambough and Guyette 2009), Mauri Timonen and others in Finland (Timonen et al. 2013), and Rob Wilson and others working on the Scottish long chronology (Wilson et al. 2012).

It was nice to also visit with Dr. Dario Martin-Benito (Martín-Benito et al. 2008, Martin-Benito 2010) who recently took a postdoc position at the University of Zurich and was a group leader in dendroecology at our North American Dendroecological Fieldweek at Black Rock Forest, NY in 2013. I also had very good conversations with Dejan Stojanović (Stojanović et al. 2013) from Serbia and Volodymyr Trotsiuk (Trotsiuk et al. 2012) who is from the Ukraine but currently studying in the Czech Republic (see more about that lab in a later post).

Büntgen, U., Esper, J., Frank, D. C., Nicolussi, K., & Schmidhalter, M. (2005). A 1052-year tree-ring proxy for Alpine summer temperatures. Climate Dynamics, 25(2-3), 141-153.

Büntgen, U., Frank, D. C., Nievergelt, D., & Esper, J. (2006). Summer temperature variations in the European Alps, AD 755–2004. Journal of Climate, 19(21).

Büntgen, U., Kauserud, H., & Egli, S. (2011). Linking climate variability to mushroom productivity and phenology. Frontiers in Ecology and the Environment, 10(1), 14-19.

Büntgen, U., Liebhold, A., Jenny, H., Mysterud, A., Egli, S., Nievergelt, D., ... & Bollmann, K. (2014). European springtime temperature synchronises ibex horn growth across the eastern Swiss Alps. Ecology letters, 17(3), 303-313.

Büntgen, U., Tegel, W., Nicolussi, K., McCormick, M., Frank, D., Trouet, V., ... & Esper, J. (2011). 2500 years of European climate variability and human susceptibility. Science, 331(6017), 578-582.

Cherubini, P., Dobbertin, M., & Innes, J. L. (1998). Potential sampling bias in long-term forest growth trends reconstructed from tree rings: a case study from the Italian Alps. Forest Ecology and Management, 109(1), 103-118.

Cherubini, P., Fontana, G., Rigling, D., Dobbertin, M., Brang, P., & Innes, J. L. (2002). Tree‐life history prior to death: two fungal root pathogens affect tree‐ring growth differently. Journal of ecology, 90(5), 839-850.

Cherubini, P., Gartner, B. L., Tognetti, R., Bräker, O. U., Schoch, W., & Innes, J. L. (2003). Identification, measurement and interpretation of tree rings in woody species from Mediterranean climates. Biological Reviews, 78(1), 119-148.

Cherubini, P., Humbel, T., Beeckman, H., Gärtner, H., Mannes, D., Pearson, C., ... & Lev-Yadun, S. (2013). Olive tree-ring problematic dating: a comparative analysis on Santorini (Greece). PloS one, 8(1), e54730.

Cherubini, P., Humbel, T., Beeckman, H., Gartner, H., Mannes, D., Pearson, C., ... & Lev-Yadun, S. (2014). The olive-branch dating of the Santorini eruption. Antiquity, 88(339), 267-273.

Cherubini, P., Schweingruber, F. H., & Piussi, P. (1996). Spatiotemporal growth dynamics and disturbances in a subalpine spruce forest in the Alps: a dendroecological reconstruction. Canadian Journal of Forest Research, 26(6), 991-1001.

Esper, J., Büntgen, U., Frank, D. C., Nievergelt, D., & Liebhold, A. (2007). 1200 years of regular outbreaks in alpine insects. Proceedings of the Royal Society B: Biological Sciences, 274(1610), 671-679.

Frank, D., Büntgen, U., Böhm, R., Maugeri, M., & Esper, J. (2007a). Warmer early instrumental measurements versus colder reconstructed temperatures: shooting at a moving target. Quaternary Science Reviews, 26(25), 3298-3310.

Frank, D., & Esper, J. (2005a). Characterization and climate response patterns of a high-elevation, multi-species tree-ring network in the European Alps. Dendrochronologia, 22(2), 107-121.

Frank, D., & Esper, J. (2005b). Temperature reconstructions and comparisons with instrumental data from a tree‐ring network for the European Alps. International Journal of Climatology, 25(11), 1437-1454.

Frank, D., Esper, J., & Cook, E. R. (2007b). Adjustment for proxy number and coherence in a large‐scale temperature reconstruction. Geophysical Research Letters, 34(16).

Frank, D. C., Esper, J., Raible, C. C., Büntgen, U., Trouet, V., Stocker, B., & Joos, F. (2010). Ensemble reconstruction constraints on the global carbon cycle sensitivity to climate. Nature, 463(7280), 527-530.

Fonti, P., Eilmann, B., García-González, I., & von Arx, G. (2009). Expeditious building of ring-porous earlywood vessel chronologies without loosing signal information. Trees, 23(3), 665-671.

Fonti, P., & García‐González, I. (2004). Suitability of chestnut earlywood vessel chronologies for ecological studies. New Phytologist, 163(1), 77-86.

Fonti, P., & García‐González, I. (2008). Earlywood vessel size of oak as a potential proxy for spring precipitation in mesic sites. Journal of Biogeography, 35(12), 2249-2257.

Fonti, P., Solomonoff, N., & García‐González, I. (2007). Earlywood vessels of Castanea sativa record temperature before their formation. New Phytologist, 173(3), 562-570.

Fonti, P., von Arx, G., García‐González, I., Eilmann, B., Sass‐Klaassen, U., Gärtner, H., & Eckstein, D. (2010). Studying global change through investigation of the plastic responses of xylem anatomy in tree rings. New Phytologist, 185(1), 42-53.

Gärtner, H. (2007). Tree roots—methodological review and new development in dating and quantifying erosive processes. Geomorphology, 86(3), 243-251.

Gärtner, H., & Nievergelt, D. (2010). The core-microtome: A new tool for surface preparation on cores and time series analysis of varying cell parameters. Dendrochronologia, 28(2), 85-92.

Gärtner, H., Schweingruber, F. H., & Dikau, R. (2001). Determination of erosion rates by analyzing structural changes in the growth pattern of exposed roots. Dendrochronologia, 19(1), 81-91.

Kaiser, K.F. 1993. Growth rings as indicators of glacier advances, surges and floods. Dendrochronologia, 11, 101-122.

Martín-Benito, D., Cherubini, P., del Río, M., & Cañellas, I. (2008). Growth response to climate and drought in Pinus nigra Arn. trees of different crown classes. Trees, 22(3), 363-373.

Martín-Benito, D., Del Río, M., Heinrich, I., Helle, G., & Canellas, I. (2010). Response of climate-growth relationships and water use efficiency to thinning in a Pinus nigra afforestation. Forest Ecology and Management, 259(5), 967-975.

Nehrbass‐Ahles, C., Babst, F., Klesse, S., Nötzli, M., Bouriaud, O., Neukom, R., ... & Frank, D. (2014). The influence of sampling design on tree‐ring based quantification of forest growth. Global change biology.

Schneider, L., & Gärtner, H. (2013). The advantage of using a starch based non-Newtonian fluid to prepare micro sections. Dendrochronologia, 31(3), 175-178.

Schweingruber, F. H. (1988). Tree rings-basics and applications of dendrochronology. D. Reidel Publishing Company.

Schweingruber, F. H. (1990). Anatomy of European woods. Paul Haupt.

Schweingruber, F. H. (1996). Tree rings and environment: dendroecology. Paul Haupt AG Bern.

Schweingruber, F. H., Bartholin, T., Schaur, E., & Briffa, K. R. (1988). Radiodensitometric‐dendroclimatological conifer chronologies from Lapland (Scandinavia) and the Alps (Switzerland). Boreas, 17(4), 559-566.

Schweingruber, F. H., Braker, O. U., & Schar, E. (1979). Dendroclimatic studies on conifers from central Europe and Great Britain. Boreas, 8(4), 427-452.

Schweingruber, F. H., & Briffa, K. R. (1996). Tree-ring density networks for climate reconstruction. In Climatic variations and forcing mechanisms of the last 2000 years (pp. 43-66). Springer Berlin Heidelberg.

Stambaugh, M. C., & Guyette, R. P. (2009). Progress in constructing a long oak chronology from the central United States. Tree-Ring Research, 65(2), 147-156.

Stojanović, D. B., Kržič, A., Matović, B., Orlović, S., Duputie, A., Djurdjević, V., ... & Stojnić, S. (2013). Prediction of the European beech (Fagus sylvatica) xeric limit using a regional climate model: An example from southeast Europe. Agricultural and Forest Meteorology, 176, 94-103.

Timonen, M., Jiang, J., Helama, S., & Mielikäinen, K. (2013). Significant changes of subseries-means in the Finnish tree-ring index of 7638 years, with comparisons to glaciological evidence from Greenland and Alps. Quaternary International.

Treydte, K. S., Schleser, G. H., Helle, G., Frank, D. C., Winiger, M., Haug, G. H., & Esper, J. (2006). The twentieth century was the wettest period in northern Pakistan over the past millennium. Nature, 440(7088), 1179-1182.

Trotsiuk, V., Hobi, M. L., & Commarmot, B. (2012). Age structure and disturbance dynamics of the relic virgin beech forest Uholka (Ukrainian Carpathians). Forest Ecology and Management, 265, 181-190. 

von Arx G and Carrer M (2014) ROXAS - a new tool to build centuries-long tracheid-lumen chronologies in conifers. Dendrochronologia. In press. http://dx.doi.org/10.1016/j.dendro.2013.12.001

von Arx, G., & Dietz, H. (2005). Automated image analysis of annual rings in the roots of perennial forbs. International Journal of Plant Sciences, 166(5), 723-732.

Wilson, R., Loader, N. J., Rydval, M., Patton, H., Frith, A., Mills, C. M., ... & Gunnarson, B. E. (2012). Reconstructing Holocene climate from tree rings: The potential for a long chronology from the Scottish Highlands. The Holocene, 22(1), 3-11.