Scientific background

Mining landscapes are rare examples of terrestrial "white spots" on maps worldwide. However, they are only one example of regions affected by severe disturbances. Unlike this cartographic "terra incognita" the GRS Microcluster supposes that disturbed landscapes can be characterized by specific "signatures". Signatures of disturbed landscapes according to the definition of this project become evident as detectable spatio-temporal patterns. They are the result of matter transformation and translocation processes across different scales.

The central scientific research questions of this collaborative research project are:

• Which specific spatio-temporal patterns can be identified as signatures of disturbed landscapes compared to undisturbed landscapes and how can they be explained?
• Are disturbed landscapes sources of matter fluxes into adjacent undisturbed landscapes and what are the effects of such transports?

For answering these questions the microcluster will use the mining landscpes of Lower Lusatia as case study.

Objectives

Overall objective of the current and of upcoming projects is to enhance the understanding of disturbed landscapes in general. It is intended, therefore, to transfer results from mining landscapes later to other types of disturbed landscapes. In future, results of this ongoing collaborative research project and of potential subsequent projects will be of interest as basis for optimizing methods for integrating disturbed landscapes into their undisturbed surroundings.

SP 2: Transformation of organic matter

Institutions within ZfNL: BTU, Department of Freshwater Conservation, Chair of Soil protection and Recultivation

Project leadership within ZfNL:apl. Prof. Dr. Michael Mutz, apl. Prof. Dr. Wolfgang Schaaf

Project realisation:José Schreckinger, M.Sc. (PhD student) , Tatiana Kholiavko, M.Sc. (PhD student)

• Recent organic matter is often missing in post-mining landscapes, but has important key functions in ecosystems.
• It is assumed that spatio-temporal water availability of disturbed landscapes results in a specific transformation and mineralization of organic matter in soils and streams.
• Litter decay experiments as well as respiration and CO₂ emission measurements are planned along moisture and vegetation gradients including ephemeral streams.

 The transformation of recent organic matter is a key function in aquatic and terrestrial ecosystems. In initial states after drastic disturbances by massive substrate relocation like surface mining, this process is of special relevance for the development of ecological functions in soils and sediments. It is assumed that these systems with disturbed or missing ecological memory and specific environmental conditions (e.g. a specific spatio-temporal availability of water) are characterized by partly decoupled sub-processes in the transformation and mineralization of organic matter in soils and streams. This results in detectable signatures like a specific dependence of soil respiration and litter decay on water availability and, related to that, specific process dynamics. Decay experiments with different litter as well as respiration and CO₂ emission measurements are planned along spatio-temporal gradients in water availability of different disturbed transitions zones from streams to terrestrial areas. These field measurements are supplemented by process studies in micro- and mesocosms under controlled conditions.

SP 3: Signatures of severely disturbed landscapes – case study mining lakes

Institutions within ZfNL: BTU, Department of Freshwater Conservation, Department of Ecology

Project leadership within ZfNL:Prof. Dr. Brigitte Nixdorf, Prof. Dr. Klaus Birkhofer

Project realisation:Lanya Feng, M.Sc. (PhD student), Jörn Jander MSc.

The “signature” of mining lakes is characterized by specific water qualities compared to adjacent landscapes which were not affected by mining activities. Acidic mining lakes are very young ecological systems with specific types of primary succession due to the acidification. This is particularly true with regard to limited nutrient and food resources, limited structural diversity and the complexity of food webs. A particular characteristic is the dominance of mixotrophic species: the bacterial production exceeds the primary production and seems to be decoupled. Autumnella lusatica is a potentially mixotrophic green alga dominant during autumn in acidic mining lakes in Lusatia. We hypothesize that a) mixotrophic metabolism favors the success of A. lusatica, b) high intensity of internal recycling of organic matter by pelagic bacteria supports the availability of inorganic phosphorus and carbon for this species and c) seasonal development of A. lusatica starts from cells overwintering in the bottom zone of lakes under low light but higher nutrient conditions. Besides, of field measurements in Lake Halbendorfer See (Lusatia in Saxony) we analyze data of further acidic lakes from 2010 to 2018. Field samples are incubated in the lab under in situ conditions to estimate primary and bacterial production Natural hard water Lake Scharmützelsee is a reference site for undisturbed systems.

Such ecologically relevant state transitions characterize matter fluxes from aquatic systems into food webs of the surrounding terrestrial habitats. The local conditions in lakes thereby likely affect carbon transfer into terrestrial food webs. A gradient of lakes with different abiotic conditions will therefore be studied for its impact on local arthropod food webs. In a second, strictly terrestrial design, natural fires constitute another major disturbance that decouples consumers and resources in local food webs. The trajectory of recovery to pre-fire conditions in disturbed landscapes is a major component of the ecosystems resilience, which is addressed in a second subsystem focusing on terrestrial food webs. The interactions between organisms at a) the interface between disturbed and rather undisturbed post-mining lakes and adjacent terrestrial habitats and b) the impact of wildfires in disturbed landscapes will be investigated by means of community analyses and studies of naturally occurring carbon isotopes. These results will provide novel insights into effects of man-made and natural disturbances on food-webs and local communities in disturbed landscapes of Lower Lusatia.