Partitioning of soil respiration into autotrophic and heterotrophic components in Hainich national park

[Master thesis only]

Soil respiration is the flux of CO2 in the interface between soil and
atmosphere. This flux is driven by the respiration of two main
components, one being autotrophic organisms (i.e. plant roots) and the
other heterotrophic organisms (mainly microbial decomposers). In
temperate forests, soil respiration typically constitutes about half of
the release of carbon from the land surface to the atmosphere. As such,
it has a strong influence on the total ecosystem C balance at different
time scales. But separating these components is necessary in order to
understand the individual response of plants and decomposers to
environmental changes.

In this context we propose a masters thesis in which the student will
combine field work and data analysis to measure separately the two main
components of soil respiration and separately analyze their response to
soil temperature, soil moisture and other potential drivers. For this,
the student will use a technique by which roots are excluded from an
area of soil by trenching. Collars will subsequently be installed and
soil chambers used to measure the flux of CO2. The thesis will thus
consist of an initial stage of field work preparing the trenched plots,
a further period of intensive field work over a few weeks measuring
fluxes and a final stage of data analysis and writing. The research site
will be the Hainich National Park, an deciduous temperate forest,
special in Germany for its age and structure. The student will thus be
introduced to topic of ecosystem C dynamics with a focus on soils, and
will learn techniques of data analysis and visualization. The results
will help improve our general understanding of the response of old
growth forests to environmental change.