Assoc. professor
I am interested in variation of plant chemical quality and in the consequences of this variation to the survival and tolerance of plants. I focus on phenolic metabolites that may protect plants against natural enemies (herbivores and pathogens) and against abiotic stress factors. A better understanding the genetic and environmental regulation
of these chemicals in plants may be helpful in designing breeding programmes for more resistant or tolerant plants, and in finding sustainable management practices in forestry and agriculture. I work with different plant species ranging from forest trees to barley and use mainly LC in routine chemical analyses.

Current research interests:
Resistance of elms to Dutch Elm Disease – role of chemical defenses and endophytic fungi (collaboration with Dr. Juan A. Martín, Polytechnic University of Madrid, Spain;
Docent Marjo Helander, Univ. of Turku, Finland, Prof. Olle Anderbrant, Lund University) and Prof. Thomas Sieber (ETH Zurich).
 
Using mainly a Spanish collection of elm (U. minor) clones with known resistance characters, we work to elucidate the possible effect of fungal endophytes on resistance of elms to DED fungi or bark beetles, and to characterize the defence mechanisms in elms. Dr. Elzbieta Rozpedowska and research student Kathrin Blumenstein are working in this project.

Teaching
I have given lectures in subjects "plant resistance and defense against natural enemies", "plant anatomy and biotic damages", "chemistry of natural products" and "HPLC technique" at SLU (Umeå and Alnarp), Umeå University and Lund University (2000 – 2010). In 2007 and 2010, I was responsible for a PhD course "Chemical Defenses in Forest Trees". I am currently main supervisor of PhD student Kathrin Blumenstein and assisting supervisor of PhD students Anna Monrad Jensen and Anna Gunulf (Southern Swedish Forest Research Centre, SLU Alnarp); Christian Schiebe and Zakir Ali (LTJ Faculty/Chemical Ecology, SLU Alnarp).

Selected Scientific Publications- Recent publications:
Witzell J, Berglund M & Rönnberg J. 2010. Does temperature regime govern the establishment of Heterobasidion annosum in Scandinavia? International Journal of Biometeorology (in press, DOI 10.1007/s00484-010-0333-1).
 
Martín J.A., Fuentes-Utrilla P., Gil L., Witzell J. 2010. Ecological factors in Dutch elm disease complex in Europe – a review Ecological Bulletins 53:209-224.

Övergaard R, Gemmel P, Welander T & Witzell J 2010. Effects of liming on site properties and natural regeneration of European beech Fagus sylvatica L in Southern Sweden. Ecological Bulletins 53:175-183.

Albrectsen BR, Witzell J, Robinson KM, Wulff S, Luquez VMC, Ågren R & Jansson S. 2010. Large scale geographic clines of parasite damage to Populus tremula L. Ecography 33:483-493.
 
Torp M, Witzell J, Baxter R & Olofsson J. 2010. The effect of snow on plant chemistry
and invertebrate herbivory: experimental manipulations along a natural snow gradient Ecosystems 13:741-751.

Martín JA, Solla A, Witzell J, Gil L, García-Vallejo MC. 2010. Antifungal effect and reduction of Ulmus minor symptoms to Ophiostoma novo-ulmi by carvacrol and salicylic acid. European Journal of Plant Pathology 127:21-32.

Torp M, Olofsson J, Witzell J & Baxter R. 2010. Snow-induced changes in dwarf birch chemistry increase moth larval growth rate and level of herbivory. Polar Biology 33: 693-702.

Witzell, J. &  Martín, J.A. 2008. Phenolic metabolites in pathogen resistance of northern forest trees – past experiences and future prospects. Canadian Journal of Forest Research 38:2711-2727.

Hjältén, J., Lindau, A., Wennström, A., Blomberg, P., Witzell, J. & Hurry, W., Ericson, L.,
Moritz, T. & Karlsson, J. 2008. Vole response to unintentional changes in the chemistry of GM poplars. Chemoecology 18:227-231.

Hjältén, J., Lindau, A., Wennström, A., Blomberg, P., Witzell, J. & Hurry, W. 2007 Unintentional changes of defense traits in GM trees can affect plant-herbivore interactions. Basic and Applied Ecology 8:434- 443.

Shrivastava, V., Schinkel, H., Witzell, J., Hertzberg, M., Torp, M., Shrivastava, M.K., Karpinska B, Melzer M,  &  Wingsle G. 2007 Downregulation of high-isoelectric-point extracellular superoxide dismutase mediates alterations in the metabolism of reactive oxygen species and developmental distrurbances in hybrid aspen. Plant Journal 49:135-148.

Selected earlier publications:
Stenberg, J,, Witzell, J,,  &  Ericson, L .2006: Tall herb herbivory resistance reflects
historic exposure to leaf beetles in a boreal archipelago age-gradient. Oecologia 148:414-425.

Witzell, J., Shevtsova, A. 2004: Nitrogen-induced changes in phenolics of Vaccinium myrtillus - implications for interaction with a parasitic fungus. Journal of Chemical Ecology 10:1919-1938.

Strengbom, J., Olofsson, J., Witzell, J.,  &  Dahlgren, J. 2003: Effect of repeated damage and fertilization on plant palatability to grey sided voles, Clethrionomys rufocanus. Oikos 103:133-141.

Hakulinen, J. 1998: Nitrogen-induced reduction in leaf phenolic level is not accompanied by increased rust frequency in a compatible willow (Salix myrsinifolia)-Melampsora rust interaction. Physiologia Plantarum 102:101-110.

Hoffland, E., Hakulinen, J.  &  Van Pelt, J.A. 1996: Comparison of systemic resistance induced by avirulent and non-pathogenic Pseudomonas species. Phytopathology 86:757-762.

Hakulinen, J., Julkunen-Tiitto, R.  &  Tahvanainen, J. 1995: Does nitrogen fertilization have an impact on the trade-off between willow growth and defensive secondary metabolism? Trees 9:235-240.

Selected Popular Science Publications
Schlyter F & Witzell J. 2009. Forests -carbon sources in peril. Public Service Review: Science and Tecnology 3: 136-137.

Lundström, M., Forsum, Å., & Witzell, J. 2007. Hotar kvävetillförsel kvaliteten hos svenska blåbär? Svensk Botanisk Tidskrift 101(6):347-350.

Witzell, J. 2008. Balanserad näringstillförsel i ungskogar – ekologiska interaktioner i ett landskapsperspektiv. Sveriges lantbruksuniversitet, institutionen för sydsvensk skogsvetenskap, Arbetsrapport nr. 38. 33 s. ISBN: 978-91-85911-45-5.

Witzell, J. m.fl. (2009). Skador på skog. Skogsskötselserien. Skogsstyrelsen. 192 s.
http://www.svo.se/episerver4/templates/SNormalPage.aspx?id=36690 

Links
Research School Sustainable Management and Utilization of Forests