Terrestrial environments are highly complex and dynamic. It consists of various types
of soils which are constantly exposed to fluctuating conditions affecting their physical
and biological properties. Moreover, soils are delivering several ecosystem services
with high relevance for the human well-being such as water purification, nutrient cycling,
or biodegradation. For many of those ecosystem services, microorganisms are the
main drivers. In consequence, it is important to understand the functional response of
microbial ecosystems to disturbances. Thus, identifying key factors for the functional
stability of microbial ecosystems in terrestrial environments is of high interest.
A powerful tool for analysing dynamics and underlying mechanisms of ecosystems
are computational simulation models. Within this doctoral thesis, a spatiotemporally
explicit bacterial simulation model was developed for assessing dynamics of biodegradation
as a typical microbial ecosystem function under the influence of disturbances.
Disturbances were introduced as lethal events for the bacteria within a certain, randomly
picked disturbance area. The disturbance characteristics vary in the spatial configuration
and frequency of the disturbance events. Functional stability was analysed
in terms of the ability to recover the function after a single disturbance event, i.e. functional
resilience, and the ability to maintain the function during recurrent disturbance
events, i.e. functional resistance. Key factors for functional stability were assessed by
systematically varying properties and processes of the microbial ecosystem and characteristics
of the disturbance regime.
Simulation results show a high influence of the disturbance characteristics, especially
its spatial distribution pattern, on the stability of biodegradation. Functional resistance
and resilience increase with fragmentation of the spatial pattern of the disturbances.
The frequency of recurrent disturbance events proved also essential for the functional
resistance: if the disturbances occur too often, the emergence of a functional collapse
may not be preventable. However, if the fragmentation of the applied disturbance patterns
increases, the function is also maintained under more frequent disturbances without
a functional collapse. Ecological processes such as bacterial dispersal and growth
are shown to enhance the biodegradation performance, but only under specific disturbance
regimes, again depending on frequency and fragmentation of the disturbances.
Dispersal networks are shown to increase the functional stability in many scenarios
and, thus, may serve as a buffer mechanism against disturbances.
Therefore, strategies facilitating these ecological processes, for instance stimulating
fungi that act as dispersal networks for bacteria, or modulating the physical soil structure
to alter the spatial configuration of disturbances are proposed to increase the
functional stability of microbial ecosystems.

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Serie / Reihe: PhD Dissertation

Personen: König, Sara

Schlagwörter: Ökosysteme Mikroorganismen Modelle Bioabfall Biodynamik

Interessenkreis: Umwelt