Finding the missing link between landscape structure and population dynamics: A spatially explicit perspective

We construct and explore a general modeling framework that allows for a sys tematic investigation of the impact of changes in landscape structure on po pulation dynamics. The essential parts of the framework are a landscape gen erator with independent control over landscape composition and physiognomy, an individual-based spatially explicit population model that simulates pop ulation dynamics within heterogeneous landscapes, and scale-dependent lands cape indices that depict the essential aspects of landscape that interact w ith dispersal and demographic processes. Landscape maps are represented by a grid of 50 x 50 cells and consist of good-quality, poor-quality. or uninh abitable matrix habitat cells. The population model was shaped in accordanc e to the biology of European brown bears (Ursus arctos), and demographic pa rameters were adjusted to yield a source-sink configuration. Results obtain ed with the spatially explicit model do not confirm results of earlier nons patial source-sink models where addition of sink habitat resulted in a decr ease of total population size because of dilution of high-quality habitat. Our landscape indices, which describe scale-dependent correlation between a nd within habitat types, were able to explain variations in variables of po pulation dynamics (mean number of females with sink home ranges, mean numbe r of females with source home ranges, and mean dispersal distance) caused b y different landscape structure. When landscape structure changed, changes in these variables generally followed the corresponding change of an approp riate landscape index in a linear way. Our general approach incorporates so urce-sink dynamics as well as metapopulation dynamics, and the population m odel can easily be modified for other species groups.