COGCI

Ecosystem Processes
Responsible: Søren Christensen.

Aim: The course aims at giving a general overview of ecosystems of the world and will focus on sensitive processes of interest in a Global change context. The course will also give an introduction for non-specialists to investigation of key-processes and tools to analyse biodiversity with emphasis on soil organisms.

Teachers: Søren Christensen, Sven Jonasson, Anders Michelsen, Annelise Kjøller, Sten Struwe and invited specialists

Form and duration of course: residential, one week, August 2001

Location: Brorfelde

Evaluation: Group report

Points: 2-4

The course describes major terrestrial biomes of the world, the climatic background for their existence and variability due to soil structure and composition, and vegetation. Focus will be on an axis covering the arctic, boreal tundra and forest, temperate forest and agriculture, and tropical forest, savannah, and agriculture. With a contrasting approach the life of soil microbes and their grazers, detritivores and carnivores is dealt with from an ecophysiological point of view. Interaction within and among these groups of organisms is discussed based on ecosystem functions considered important such as primary production, decomposition, and trace gas exchange soil-atmosphere. Decomposition involves a vast number of soil organisms organised in trophic and information networks of varying interaction strength. In contrast, primary production is mainly governed by a single organism (the plant) in close interaction with specific beneficial and harmful micro-organisms and invertebrates, and more casual interaction with selected decomposer organisms. Main trace gases of the atmosphere (CH4 and N2O) are produced and consumed by soil organisms, which are also members of the decomposer system. Under this heading tools to trace specific organisms and processes of importance are described. Broad scale approaches are presented that describe the structure and function of the soil decomposer community and possibly the associations involved in primary production. By focussing such descriptions on measurable community functions like decomposition and on the resistance and resilience of decomposition to well defined disturbances one of the aims is to discuss the importance of single species for ecosystem function in a way that may be experimentally verified. Ultimately this community approach will help bridging the gap between the above-mentioned biome approach and ecophysiological approach that is based upon research disciplines within different branches of natural science. The interactions of human activities with ecosystem processes are discussed in a land-use framework whereby manageable aspects will be in focus. Change from forest to agriculture in the temperate or tropic zone, and drainage of humid soils in the boreal zone are land use changes that affect biotic processes within the system. These changes will eventually results in altered outputs of CO2 and trace gases to the atmosphere and of inorganic ions such as NO3- to subsurface aquifers. Topics: Soil description, pedology, structure and composition. Water, movement and availability. Primary production in different biomes, energy, water, nutrients, experimental techniques. Decomposition, microorganisms (bacteria and fungi) diversity and activity, microfauna interaction Trace gases, microbial production and consumption, experimental approaches, upscaling of results from plot to landscape to region Intervention strategies, managed ecosystems, dealing with pollutants as stress factors
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