Ecosystem based indicators in retrogressive successions of an agricultural landscape

This paper aims at two main objectives: first, an ecosystem-oriented indicator set is presented and applied at the landscape scale. Then, the utility of this indicator set is assessed with reference to retrogressional successions in typical wetland ecosystems of Northern Germany. The results are based on measurements and GIS linked model applications in the Bornhِved Lakes District. The outputs of 30 years runs of the model system WASMOD/STOMOD have been assigned to theoretically derived indicators. As an exemplary result, relative watershed balances are presented, concerning carbon and nitrogen compounds. These budgets identify some current land use practices as causes of a shift of the whole landscape from a sink to a source function, provoking disturbance in aquatic systems by eutrophication and contributing to the greenhouse effect processes. A more detailed analysis of the wetland systems of the investigated watershed illuminates the process sequences of retrogressive successions. These case studies are used to analyse the indicator set critically, to discuss the single indicators and to propose respective management measures. In this context, it turns out that the behaviour of the indicators is generally in accordance with the fundamental principles of ecosystem theory except for the indication of entropy production that does not show the expected dynamics due to high respiration rates in intensively used ecosystems.