Spatio-temporal Analysis of Vegetation Dynamics of Selected Successional Stages of Dry Acidic Grasslands: Experimental Studies and Model Simulations

Dissertation, August 2009

Marcel Austenfeld

“A generic modeling environment for the analysis and simulation of spatio-temporal phenomena in ecosystems was developed. This framework was built upon a Rich Client Platform (RCP) which uses new concepts of extensibility and software architecture for sustainable development and provides a solid basis for an Integrated Development Environment (IDE) for ecological models. The integration of various statistical tools, imaging routines and several specialized drawing panels makes this environment particularly suitable for the analysis of the above mentioned spatio-temporal ecological processes.

“Because of their comparatively low complexity, dry acidic grassland ecosystems have been repeatedly used for studying vegetation pattern formation and the underlying biotic interactions. In order to obtain an integrative view of the existing knowledge as well as to provide a possibility for further integrative analysis with the help of model simulations, the above described platform was used to develop an individual based Model structure for the investigation of long term effects of environmental changes on the stability of early successional stages of such dry acidic grasslands which are typically dominated by the two pioneer species Corynephorus canescens and Polytrichum piliferum. The model was validated with experimental data and the spatio-temporal patterns created by the model were in good accordance with the measured natural patterns.

“The model was then used to analyze the effect of changes in temperature, nutrient supply and disturbance rate on the long term behavior of this ecosystem. The results showed an overall high stability of this system under different temperature and nutrient scenarios as long as an intermediate disturbance frequency is assured.

“Finally, an experimental study on the effect of herbivory and competition on the Corynephorus canescens was conducted. In a controlled field experiment, the effects of the removal of various amounts of aboveground biomass on the above and belowground biomass allocation during the following regeneration phase was analyzed in the presence or absence of an intraspecific and interspecific competitor (Hieracium pilosella). The results show a rather high ability of C. canescens to compensate low to medium amounts of foliage loss (reflecting the typical natural herbivory induced by grasshoppers and rabbits) without significant changes in its competitive ability. Belowground, no biomass effects of foliage removal and/or competition could be detected. Because of these negligible effects, herbivory was not implemented in the above described model.”

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