Come and visit us if you are a Helsinki University student interested in doing your Master’s or PhD research, or final undergraduate project and training, with us:
Choose from the example Masters or PhD projects or come up with one of your own….
Modelling environmental controls on phenology of Fraxinus excelsior
Seasonal controls on the development and annual cycle of plant growth have for a long time proved an intriguing question for scientists and the public alike. When unusual weather accelerates or delays flushing in the spring, mismatches across components of communities can lead to a catastrophic loss of ecosystem function. Concerns about climate change make research into the understanding of environment controls acting on phenology particularly timingly. In case of ash (Fraxinus excelsior) the need to understand these controls is further heighten by the spread of a fungal pathogen causing ash die-back disease across Europe, whose infection success appears linked to host tree phenology.
Using an extensive database of observation of tree phenology, weather, and location, you will create optimal mathematical models on the environmental controls that determine the timing of development of tree populations based on location of growth and origin affected by day length, light quality, winter and spring temperature, and fertility. These models can be applied to better understand the potential for species range shift and disease resistance under climate change scenarios.
Do growth and fitness correlate with photosynthesis and phenology to explain within tree species differences derived from their distance from ecological niche.
A field trial of Fagus sylvatica growing in Viikki fields contains populations from Spain, Sweden and low and high elevation provenances from Germany. These populations differentially process environment cues to control their development. This means that they each flush and senescence at different times. Differences between Helsinki and each populations’ home habitat also mean that they photosynthesize and grow at different efficiencies.
Despite the sophistication of modern plant ecology is remains difficult to scale-up differences in plant physiology and development to differences in growth rate. In this project you will utilise ecophysiological techniques to characterise the growth and photosynthesis of saplings in the field trial, and to obtain the input date to model carbon capture and utilisation by these saplings over a year and to test the relationship between this and the growth of saplings from each population with a view to understanding the causal relationship between the distance from ecological niche and reduced fitness of populations.
Achieving a better understanding of this relationship is crucial for our understanding of how climate change might affect future species distributions. Since currently our knowledge of how the combination of different environmental cues changes plant fitness remains very basic.
Autumn phenology of tree species and concomitant changes in understorey plants
Light capture during early spring is important to understorey plants coordinating with the canopy, but there is also an opportunity for understorey plant to exploit favourable conditions on the forest floor in the autumn to gain carbon later into the year than canopy trees. However these processes are relatively unstudied.
In the autumn the soil is warm from the summer growing season so metabolic activity of plants can be high, and protection from loss of infra-red radiation (IR) is afforded by canopy trees even once they begin to lose their leaves. As leaves change colour the quality of radiation available for forest understorey plants improves, and the light signals that they receive change. But how do they use this information?
By understanding these sort of seasonal patterns in light capture and signalling, we can model annual photosynthetic carbon assimilation by different plant species, and we can understand better the community-level changes that occur in understorey plant species.
Since we know that the spectral composition of solar radiation changes with latitude, time of year, and canopy species composition and age, we must control for these factors when we compare different forest understories.
Decision making based on spectral signals
Plant have photoreceptors that perceive changes in the light environment in their surroundings and processes these signals. But how is this information utilised in the type of patch environment that plants encounter in nature.
When plants’ stems and leaves encounter two environments of different light quality how to they proceed to grow? As modular organisms, how is the information that plants receive integrated to make a decision on the outcome.
For instance, plants with long exploratory stems like ivies, honeysuckles and passion flowers can ‘move’ around exploring their surroundings, but does this exploration involve a trade off in growth and allocation of resources?
Such questions can be tested with simple controlled experiments using colour lights to find out how subtly plants react to changes in their surroundings.