Johanna Witzell

Johanna Witzell


Associate professor, Editor-in-Chief Scandinavian Journal of Forest Research


My teaching covers forest pathology, tree resistance and defense against natural enemies, and chemical ecology. I am currently course responsible for MSc thesis course, and teach a 1-week module "Scientific reading and writing" in distance education. In 2021, I will be course leader for a 7.5 HEC course in Forest Health. During my affiliation with UEF in Finland (2014-2016), I was course leader for MSc level courses 3513143 "Microbes in trees and wood" (5 ECTS), 3513142 "Basics of wood materials science" (1 ECTS), 3513138 "Thesis Seminar II in Wood Materials Science" (1 ECTS), 3513139 "Master’s Thesis in Wood Materials Science" (30 ECTS). I have organized several PhD courses in my role as a research school coordinator (2008-2013). 


My research interests include forest diseases, tree resistance and stress responses (with special interest in phenolic defensive compounds), functional traits of fungal endophytes of trees, Dutch elm disease and invasive Phytophthora-species. I am interested in the interface between biology and forest management, e.g., how fertilization influences tree quality, how thinning influences fungal biodiversity, or how the fungal communities can influence tree resistance or regeneration success.

Research in my group is financed by EU MSCA IF grant to post doc researcher Dr. Carmen Romeralo, and MSCA ITN grant to a PhD student (project "PROTECTA", coordinated by Prof. Laura Grenville-Briggs Didymus), by SNS, Swedish Research Council Formas and Carl Tryggers foundation. I collaborate with Dr. Michelle Cleary (SLU; Phytophthora-damages of broadleaved trees), Assoc. Prof. Benedicte Albrectsen (Umeå University, Umeå Plant Science Center; endophytes and tree chemical defenses), Assoc. Prof. Juan A. Martín (UPM, Madrid, Spain; Dutch elm disease, tree endophytes). 



Tree and forest diseases interest forest owners, forestry professionals and common public, and an important part of my work is to inform about diseases to different target groups in society. In our Forest Pathology Lab in Alnarp, we frequently conduct disease diagnoses to forest managers and private forets owners. 


Chemical quality of woody plants, based on phenolic metabolites, has been the subject of most my studies since I finished my PhD in Professor Riitta Julkunen-Tiitto’s (UEF, Finland) research group in Finland (1998). My PhD thesis focused on studying the effect of nitrogen fertilization on the growth and phenolic metabolites in dark-leaved willow (Salix myrsinifolia Salisb.). 

I came to SLU in 1999, to work as a post-doctoral fellow in Professor Torgny Näsholm’s group (SLU, Umeå Plant Science Center). In that position, I continued to explore the effects of nitrogen amendments on plant defensive chemistry, but this time the study system was bilberry (Vaccinium myrtillus L.), a keystone species of boreal forests. Between 2002 and 2006, I continued this research an assistant professor, financed by the Swedish Research Council Formas.

In 2006, I moved to Southern Swedish Forest Research Center, where I started to work with Dutch elm disease (collaboration with Prof. Juan A. Martín, UMP Madrid), focusing on the role of endophytic communities in this disease complex. Since 2010, I have also been working with Phytophthora-diseases of broadleaved trees, lately in close collaboration with Dr. Michelle Clearly. This work includes close contacts with forest owners and common public. 

During 2014-2016, I was holding a chair of Professor in Wood Materials Science at my Alma mater, the University of Eastern Finland (80% of full time). My main task in this position was to lead the international MSc program in Wood Materials Science. Since June 2016, I am back at SLU where I continue research on forest tree health.


Currently I am main supervisor for PhD student Noelia López-García (start 2019). I was main supervisor for Marta Agostinelli, who defended her thesis on fungal assemblages in forest trees in December 2018, and for Dr. Kathrin Blumenstein (currently post doc in Georg August University in Göttingen) who defended her thesis on elm endophytes in December 2015. I am also co-supervisor for four PhD students, and have been a co-supervisor for six completed PhD students in 2005-2020. I have also supervised several BSc and MSc thesis projects.