PhD students

Malin Broberg, PhD student



I study the impacts of elevated ozone and carbon dioxide on wheat crops, using meta-analysis and dose-response relationships together with experimental studies. My main interest are effects related to crop yield and grain quality, such as protein and mineral content, but also to understand the underlying mechanisms by evaluating impacts on photosynthesis, gas-exchange and fertilizer-efficiency.

Supervisors: Håkan Pleijel, Johan Uddling


Maria Wittemann, PhD student



My PhD studies focus on tropical tree species in a changing climate. Tropical regions have been experiencing a relatively stable climate both historically (as opposed to changes in temperate zones during the ice ages) and short-term (lacking seasonality). With climate change putting an end to this, there has been growing concern about the ability of tropical trees to acclimate to rising temperatures and more extreme periods of drought and high precipitation. Yet there is discord as to the relative importance of changes in different processes causing temperature and drought sensitivity. These include the biochemistry of photosynthesis (higher temperatures shorten reaction times, but also destabilize proteins and membranes), respiration (which is restricting net photosynthesis) and water balance. The latter is naturally influenced by drought, but also by temperature, since higher temperatures cause rising transpiration. This can result in cavitation and weaken the trees substantially. In my project I attempt to  resolve these relative importance and thereby offer new insight for tropical tree conservation.

Supervisors: Johan Uddling, Göran Wallin, Håkan Pleijel


Aloysie Manishimwe, PhD student

Employed at the University of Rwanda and affiliated to the University of Gothenburg through supervisors Wallin and Uddling



Project: Biomass allocation in tropical montane tree species in response to elevated temperature.

It is predicted that the ongoing climate change will continue for the next 50 to 100 years which is directly linked to anthropogenic emissions of green-house gases (IPCC 2014). Although, little is known on how tropical trees will acclimate and adapt to these changes (Malhi et al. 2010; Malhi et al. 2013), there is growing evidence that tropical ecosystems are highly sensitive to climate change and variability,especially elevated temperature (Alo & Wang 2008). To explore how these important ecosystems may react on climate change, this study will investigate how pioneer and climax tree species from low and mid elevation tropical montane forests, will react to elevated temperatures. Specifically we will investigate the effects of temperature on biomass allocation in tropical trees’ foliage, stems and roots by using a unique altitudinal gradient experimental design representing future warming scenarios (Malhi et al. 2010). Confounding of variation in water and nutrient availability will be minimized through water and fertilizer treatments.

Supervisors: Göran Wallin, Johan Uddling

Myriam Mujawamariya, PhD student

Employed at the University of Rwanda and affiliated to the University of Gothenburg through supervisors Uddling and Wallin



Physiological responses of tropical rainforest tree species in a warming world

My PhD project aims at improving the limited understanding of the climate change sensitivity of a broad range of tropical tree species in Rwanda. The project will investigate physiological responses and underlying biochemical mechanisms of tropical tree species to global warming by determining whether photosynthesis and dark respiration can acclimate to elevated temperature. Taking advantage of an elevational gradient in Rwanda, pioneer and climax species have been taken from Afromontane as well as transitional vegetation zones of Rwanda and then planted at three sites along elevation gradients in Rwanda. A step down the elevation gradient represents a possible future warming scenario. My findings will provide useful information to climate modelers as well as informing the scientific community regarding the climate sensitivity of these important ecosystems and their feedback on the global carbon cycle and ongoing climate change.

Supervisors: Johan Uddling, Göran Wallin


Bonaventure Ntirugulirw, PhD student

Employed at the University of Rwanda and affiliated to the University of Gothenburg through supervisors Wallin and Uddling



Project: Study on the suitability of different indigenous tree species in different regions of Rwanda with respect to their climate and climate change sensitivity.

Nowadays, there is an increasing evidence that tropical ecosystems are extremely sensitive to climate change, including both biomass production and tree mortality. However, more research is required to reduce current doubts about the climate-change impacts on forests and people and improve knowledge regarding management and policy measures for adaptation. In this study we will establish trial of pioneers and climax tree species at three different sites along an elevation gradient in Rwanda. The purpose of this study is to ascertain the sensitivity of growth and competitiveness of Rwandan native tree species in conditions of increased temperature. This knowledge is critical for attempts to understand and consistently predict the potential effects of climate change on tropical forests especially the major native tree species growing in Rwandan forests.

Supervisors: Göran Wallin, Johan Uddling