Research focus: Ecophysiology of plant interactions

The main research focus of our department is the causal analysis of plant interactions and vegetation pattern formation.

During the last decades "plant physiological ecology" or "ecophysiology" has become an important component of botanical research because it closes the gap between plant physiology/plant molecular biology on the one side and vegetation analysis, plant population ecology and analysis of ecosystem level processes on the other. Quantitative analysis of physiological key parameters and processes of plants in situ i.e. under natural field conditions and the comparison of this with the behavior under controlled conditions in the laboratory reveals important information about the causal background of plant (co)existence and niche occupation at particular sites.

Background: Advancement of ecophysiological research

In the past, ecophysiological research on plants mainly focused on the reactions of single plant individuals or even selected plant organs (e.g. leaves, stems etc.).

A methodological breakthrough in this connection was the development gas exchange measuring systems, which allowed the researcher to assess photosynthesis and transpiration rates continuously and with laboratory precision at the field site. In Germany, this development is closely connected with the name of Prof. Dr. O. L. Lange (University of Würzburg) and the manufacturer Heinz Walz (Heinz Walz GmbH, Effeltrich). By combining diurnal course measurements with the measurement of single factor dependency curves under controlled conditions, it became possible to quantitatively assess the dependence of plant primary production and water relations from the abiotic site conditions and stress factors in a large variety of ecosystems all around the world.

Recently, this research received new impulses by the development of field suitable chlorophyll fluorescence measurement systems, mainly inspired by Dr. Ulrich Schreiber (University of Würzburg) and again manufactured by the Heinz Walz Company. In parallel, mathematical models were developed which allowed to scale up from the behavior of single plant organs (typically gas exchange and chlorophyll fluorescence measurements on single leaves or small twigs) to the whole plant.

Objectiv: Contributions to ecosystem research

However, the natural behavior of plants in the field is not only the result of the abiotic site conditions but is also dependent on the biotic environment. Numerous interactions (plant/plant, plant/animal, plant/fungus, plant/microbe) include the whole spectrum of mutualistic and antagonistic effects reaching from competition and parasitism all the way to facilitation and symbiosis. Carbon uptake and transpiration rates are only one (but nevertheless important) aspect in this scenario while growth and allocation patterns of all kind seem to play the key role. Comparing the behavior of plants growing isolated vs. plants growing together with other plants, it has frequently been observed that the mere presence of an intra- or interspecific competitor can lead to significant differences in allocation and growth patterns and, therefore, in competitive behavior.

For the causal understanding of ecosystem scale processes like vegetation dynamics or fluxes of matter it is, therefore, essential to assess the ecophysiology of plant interactions. During recent years quite a few groups all over the world (including us) started to focus on this new type of plant physiological ecology which has close links to population, community and systems ecology.