PhD students

Malin Broberg, PhD student


E-mail
: malin.broberg@bioenv.gu.se

I study the impacts of elevated ozone and carbon dioxide on agricultural crops, using meta-analysis and dose-response relationships together with experimental studies. Elevated levels of tropospheric ozone and carbon dioxide may significantly influence crop yields and its quality, such as protein and mineral nutrient content, but also baking qualities. This project aims to aggregate experimental field data from the 1980’s until present, in order to estimate the overall effects. Dose-response relationships between ozone/carbon dioxide and different crop variables are derived to evaluate the sensitivity to these environmental factors. Crops of main concern are varieties of wheat and rice, with experiments covering growing conditions in Europe, Asia, Australia and North America.

Supervisors: Håkan Pleijel, Johan Uddling


Shubhangi Lamba, PhD student

Shubangi

Tel: 031 786 2928
Fax: +46 31 786 2560
E-mail: shubhangi.lamba@bioenv.gu.se


There is a lot of uncertainty in the response of trees and entire forest ecosystems due to the increasing atmospheric CO2 concentration and climate change. Much of these uncertainties are due to poorly quantified, bidirectional climate-forest feedbacks. Investigating responses of specific forest ecosystem processes such as photosynthesis, respiration and tree-atmosphere exchange of CO2 and H2O in detail is important to estimate forest responses to and feedbacks on climate change. My study deals with the response of boreal Norway spruce forest ecosystem processes such as photosynthesis, respiration and transpiration to increasing CO2  concentration and temperature. Effects of elevated CO2 and temperature on mature boreal spruce trees were studied in field experiments in which fluxes of both CO2 and water flux data are available at shoot as well as whole tree level.  Responses of shoot photosynthesis, respiration, stomatal conductance and phenology are quantified and scaled up to whole tree level by using the MAESTRA model to assess the relative importance of different types of plant acclimation in a changing climate. My research also aims to introduce dynamic tree responses (i.e. tree acclimation) into the dynamic global vegetation model (DGVM) LPJ-GUESS.

Supervisors: Johan Uddling, Göran Wallin


Maria Wittemann, PhD student

MariaWittemann


E-mail
: maria.wittemann@bioenv.gu.se

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 Fredin, Göran Wallin


Myriam Mujawamariya, PhD student

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

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E-mail
: mmujawamariya@gmail.com

Project:
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.


Aloysie Manishimwe, PhD student

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

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E-mail
: aloysie.manishimwe@yahoo.fr

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.


Bonaventure Ntirugulirw, PhD student

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

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E-mail
: ntirugulirwab@yahoo.com

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.


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