Rainer Krug

Areas of interest and expertise

I am interested in theoretical ecology, particularly ecological modelling and its integration and interaction with field experiments and data. My main interest lies in the field of processes and pattern description and analysis — which processes cause pattern and how pattern influence the processes. These pattern and processes can range from population to ecosystem levels.

Essential is for me the close integration of theoretical models and field work and field data. Models can help to plan experiments, determine sample sizes needed, simplifying experiments. Field experiments can enhance and simplify models and validate results obtained in ecosystem models. These simplified but valid models can be used to address conservation related questions.

More specifically, I am interested in the functioning of ecosystems and the dynamics of populations and communities — which processes and disturbances are essential in maintaining the dynamics? How do they react to changes in e.g. the frequency or intensity of these processes? Which processes and disturbances are essential in maintaining certain pattern in the system? Which role does dispersal play in the maintenance of these systems?

To answer these questions, it is important to combine field work with ecological simulation models of different complexity in all stages of the project — from the planning of the experiments to the analysis of the field data and the identification of important parameter and processes.

My PhD focused on the role of seed dispersal in restoration and biological invasion, the effects of alien vegetation on the establishment of indigenous species and the effects of biocontrol agents on the spread of invasive species. This involved developing rule-based simulation models reflecting the seed dispersal and plant distributions observed in the field, and making predictions of the spread of species under different scenarios. The model was written in Delphi.

A recent research focus was on population dynamics and reconstructing the age structure of populations of Aloe pillansii, spatial dynamics of alien invasive plants and the interaction with different management strategies, including biocontrol. My latest projects (spatial and temporal dynamics) combine the field of ecological modelling with spatial statistics, as the development of simulation models as well as the comparison of different spatial pattern is essential to them.

To link management into the models developed to be able to provide applicable feedback to managers, is an important aspect for me, as well as the close co-operation with managers during all phases of the project. This approach, coupled with a close co-operation with field biologists, makes it possible, that the results of the projects are not only scientifically interesting, but also have an impact on the management practises.

In the field of statistics, I am interested in resampling methods and I employed a bootstrapping approach in the analysis of seed dispersal data. Data arising from the simulations are all analysed in the statistical package R, using a range of different functions and modules. I have written numerous scripts in R to aid with data analysis and presentation. I also wrote a package for R implementing the Earth Movers Distance based on an implementation in C++ by Haibin Ling and Kazunori Okada.

All my simulation models and analysis use only Open Source software. This includes Linux as the operating system of choice, R for analysis and writing my simulations, GRASS and QGIS as GIS programs, which I also use in my simulations (GRASS). This approach of only using Open Source software, provides the flexibility to develop the simulation models and analysis protocols, distribute them freely and to enable others (scientists as well as implementing agencies like nature conservation agencies) to use the code without limitations and without having to purchase specific software.

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Research Projects and Experience

My postdoctoral fellowship at the C·I·B is currently focusing on the the spatial and temporal dynamics of selected biocontrol agents and their hosts. The invasive species being investigated are Hakea sericea, Acacia cyclops and Acacia mearnsii and their respective biocontrol agents. The study will address questions concerning the dynamics resulting from a single biocontrol agents based on the dispersal ability of the agent, the dynamics resulting from the introduction of multiple bicontrol agents. In addition, the project will evaluate different release scenarios for the agent, with the aim to identify rules which help to increase the efficiency of biocontrol (re-)releases.

In addition, I am wrapping up a project which addressed the question of which areas should be selected for alien management. Due to budget limitations, it is in most cases not possible to clear aliens in a management area. Therefore a prioritisation has to be conducted, identifying the areas to be cleared. This project addressed the following questions: which factors are involved in the spatial prioritisation conducted by the managers? Can this prioritisation be translated into a GIS framework? Is the prioritisation strategy used, in comparison to other hypothetical and possible strategies, the most effective for different areas and budget scenarios? This project included aspects ranging from using an Analytical Hierarchical Process to capture and quantify the subjective decision making process of prioritising, translating this into a spatial simulation model, developing a spatial–temporal simulation model which included fire, alien plant management, different dispersal vectors (wind, water, birds) and to use high performance computing infrastructure (cluster) to run the simulations and to develop a package for R to compare the different resulting prioritisation maps spatially.

The project generated considerable interest from CapeNature and Working for Water. These implementing agencies intend to adopt results arising from the study and consider adjusting their alien clearing strategies accordingly.

I’m also involved in two projects addressing the spread of invasive species under different climate change scenarios. This involved developing the spread models (one population based, the second probabilistic) which include climatic suitability maps to project the observed distribution under different climate change scenarios to identify risk areas and to assess the invasive potential of these species.

A third project I am working on at the moment, in collaboration with Brian van Wilgen (CSIR), concerns the viability of pine plantations under different (and changing) fire regimes.

My postdoctoral fellowship at UCT focused on two aspects, namely analysing the population dynamics of Aloe pillansii, a tree aloe, with focus on the recruitment events and their reconstruction (together with Prof. Timm Hoffman (University of Cape Town, PCU)), and secondly, in co-operation with Prof. Dave Richardson (C·I·B, Stellenbosch University), modelling the spread of alien species in the Western Cape with the aim of optimising the alien management strategies.

Research for my PhD focused on modelling the role of seed dispersal in restoration and biological invasion, and investigating factors influencing the spread of a species. I have developed rule-based simulation models based on data collected in the field and experts estimates to predict the rate of spread of a species depending on dispersal ability, competition experienced in establishment, and the effects of biocontrol agents.

For my MSc project in Conservation Biology I investigated the genetic heterogeneity of three populations of African Buffalo using microsatellites and gained knowledge on population genetic techniques and analysis methods.

As part of the MSc course in conservation biology, I conducted two smaller research projects. The first was a GIS based conservation planning exercise in which species presence — absence data was used to identify areas most relevant for conservation. The second was an analysis of the financial value of the Good Hope Environmental Education Centre. It included, among others, questionnaires to tourists and schools concerning their willingness of paying to visit the centre.

In my research for my Diplom (MSc) in Germany, I was working on a simulation model focus sing on the effect of habitat use on the mean survival time of populations. This research was conducted in co-operation with a biologist who was involved in the planning of the project and in the formulation of the questions. Building a simulation model of the population investigated provided important insights in the importance of different habitat types for the survival and conservation of the species.

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Conference oral presentations

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Conference poster presentations

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Guest lectures

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