>>Department of Ecological Modelling >> Personal homepage Thorsten Wiegand >>  Research

Main research projects:

Landscape and Population Ecology  

Integrating approaches of landscape ecology and population modeling for assessing the impact of landscape structure on population dynamics  

• Finding the missing link between landscape structure and population dynamics (with Kirk A. Moloney)


We developed a spatially explicit modeling framework for integrating the approaches of landscape ecology and population modeling (Wiegand et al. 1999). Our framework facilitates a systematic investigation into the impact of landscape structure on spatially explicit ecological processes and population dynamic and consists of three essential ingredients: first, a modeling approach that is spatially explicit; second, a landscape generator that creates non-random, “realistic” landscape maps where the relative amounts of different habitat types (landscape composition) and the spatial arrangement of habitat types (landscape arrangement) can be varied independently; and third, appropriate landscape measures that establish a quantitative relationship between landscape structure and population dynamics. 
 

• Relative effects of habitat loss and fragmentation on population dynamics (with Eloy Revilla and Kirk A. Moloney)


Although conservation ecologists have studied the effects of habitat loss and fragmentation extensively, the relative importance of both processes in determining the fate of a population is still unclear and the important question arises as to what extent the alteration of landscape pattern can compensate for or worsen the effects of habitat loss. Additionally, it is not clear how to measure fragmentation in an appropriate way. To examine the relative impact of habitat loss and fragmentation on population dynamics, we employ a previously developed framework (Wiegand et al. 1999) for studying the impact of changing the structure of realistic, artificial landscapes containing three types of habitat (good quality, poor quality, and matrix) on population dynamics. We use an individual-based, spatially-explicit model, developed for species with a stable home range and natal dispersal, to simulate population dynamics within 80 landscape maps with different physiognomy and composition. We relate population size to linear combinations of scale-dependent landscape measures, the proportion of good-quality habitat in the landscape, and the interaction between these two factors (Wiegand et al. 2005).
 

• Analyzing dispersal of large carnivores (Eloy Revilla)


A dispersal track is the synergic outcome of the interplay between the behavioral dispersal characteristics of the species, the structure of the underlying landscape, and the demographic frame where it occurs. Therefore, telemetric data contain a great deal of (encoded) information on dispersal characteristics and on the effect of landscape structure and demography.  15 year telemetric data on 30 dispersing Iberian lynx (Lynx pardinus) from the Doñana metapopulation in southern Spain enable us to extract hypothesis on behavioral movement rules of individual lynx in response to landscape structure on a intraday timesale, and to calculate metapopulation scale patterns, i.e., connectivity values between subpopulations, and maximum distances dispersed. We develop a series of nested dispersal models that start with the simplest possible representation of dispersal, a random walk, and progressively include more structural realism to answer the following questions: (1) Can we use mechanistic dispersal rules on a intraday timesale and on the individual level to approximate high level metapopulation-scale patterns, (2) which detail and/or structural realism do we need for this, and (3) can we parameterize simple dispersal models from field data? (Revilla et al, 2004, Kramer-Schadt et al. 2004, 2007).