Tree ring parameters like ring width, wood density and stable isotope ratios have been used for a long time in areas outside the tropics as powerful tools for the retrospective analysis of tree growth and its response to environmental factors.
The existence of annual rings in several species of tropical trees has been known for a long time. However, a lack of climate signal strength and the absence of distinct annual rings in many species has so far prohibited the general use of tree ring parameters as a dendroclimatological tool in the tropics.
- to apply high resolution stable isotope analysis to endorse tree ring boundaries
- to assess the response of tropical trees to climate change from physical and chemical tree ring parameters(retrospective tree physiology)
- to reconstruct climate from tree rings of tropical trees
- Tree-ring width measurements
- Wood cell structure analysis (e.g. with confocal laser microscopy)
- High resolution stable isotope analysisof carbon and oxygen
- Dendroecological monitoring
- Twentieth Century changes of tree ring isotopes in Southeastern Brazilian forests How do climate conditions influence growth and water use efficiency (WUE) and thus enforce tree migration? (DFG)
- Dendroclimatological information from African Baobab (Elsa Neuman Stiftung)
- HIMPAC (DFG)
- Indopal (DFG, abgeschlossen)
Publications and Presentations
Schollän, K., Heinrich, I., Helle, G. (2014): UV-laser-based microscopic dissection of tree rings - a novel sampling tool for δ13C and δ18O studies. - New Phytologist, 201, 3, p. 1045-1055.
van der Sleen, P., Soliz-Gamboa, C. C., Helle, G., Pons, T. L., Anten, N. P. R., Zuidema, P. A. (2014): Understanding causes of tree growth response to gap formation: ∆13C-values in tree rings reveal a predominant effect of light. - Trees - Structure and Function, 28, 2, p. 439-448.
Schollaen, K.; Heinrich, I.; Neuwirth, B.; Krusic, P. J.; D’Arrigo, R. D.; Karyanto, O.; Helle, G. (2013): Multiple tree-ring chronologies (ring width, δ13C and δ18O) reveal dry and rainy season signals of rainfall in Indonesia. Quaternary Science Reviews, 73, 170-181
Slotta, F.; Helle, G.; Heinrich, I.; Heußner, U.; Shemang, E.; Riedel, F.; Tarasov, P. (2013): On the potential of the African baobab, Adansonia digitata, for palaeoclimatic studies. Program and Abstracts of the Dendrosymposium 2013, TRACE 2013 - Tree Rings in Archaeology, Climatology and Ecology (Viterbo, Italy 2013), 98.
Schollaen, K.; Heinrich, I.; Neuwirth, B.; Krusic, P.; D‘Arrigo, R.; Karyanto, O.; Helle, G. (2013): Multiple tree-ring chronologies (ring width, delta13 C and delta18 O) reveal dry and rainy season signals in Indonesia. General Assembly European Geosciences Union (Vienna, Austria 2013).
Brienen, R. J. W.; Helle, G.; Pons, T. L.; Guyot, J.-L.; Gloor, M. (2012): Oxygen isotopes in tree rings are a good proxy for Amazon precipitation and El Niño-Southern Oscillation variability. PNAS, 109, 42, 16957-16962.
Pons, T. L.; Helle, G. (2011): Identification of anatomically non-distinct annual rings in tropical trees using stable isotopes. Trees - Structure and Function, 25, 1, 83-93.
Hennig, K.; Helle, G.; Heinrich, I.; Neuwirth, B.; Karyanto, O.; Winiger, M. (2011): Toward multi-parameter records (ring width, δ13C, δ18O) from tropical tree-rings - A case study on Tectona grandis from Java, Indonesia. Proceedings of the Dendrosymposium, April 22nd – 25th, 2010 in Freiburg, Dendrosymposium (Freiburg 2010), 158-165.
Fichtler, E.; Helle, G.; Worbes, M. (2010): Stable carbon isotope time series from tropical tree rings indicate a precipitation signal. Tree-Ring Research, 66, 1, 35-49.
Helle, G., Treydte, K.S. & Verheyden, A. (2004) Tropical Swietenia macrophylla wood reveals a systematic recurring carbon isotope pattern. TRACE Tree Rings in Archaeology, Climatology and Ecology, Vol. 2, Proceedings of the DENDROSYMPOSIUM 2003, May 1st – 3rd 2003, Utrecht, The Netherlands, ISBN 3-89336-349-1: 107-109