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FP5

TRANSPLANT Résumé de rapport

Project ID: EVK2-CT-1999-00004
Financé au titre de: FP5-EESD
Pays: Sweden

Analysis landscape configuration

Regional distributions of animals and plants in landscapes are the result of local population dynamics within habitat patches and dispersal among patches. The dynamics and extinction risks of local populations are strongly influenced by local habitat conditions. Dispersal resulting in establishment of new populations or augmentation of existing populations critically depends on landscape configuration. Metapopulation theory explains distributions as determined by the balance between extinctions and colonisations, and it has generated an increased interest in large-scale spatial dynamics and landscape processes, such as habitat fragmentation. Hence, assessments of population viability within a larger landscape fragment must consider both these aspects.

To model the importance of landscape configuration for the long-term survival probabilities of four target plant species in an agricultural landscape of 7 square kilometres, we collected information about landscape configuration, in terms of categorization of habitat into suitable or unsuitable and presence or absence of each of the target species. This information formed part of the GIS-model (see "Building GIS mode"). We continued by building more complex models that included also information on habitat quality and the land use history of each habitat patch. Lastly, we incorporated the local population dynamics of plant species assigned a particular type of local demography to a particular habitat quality type by using the demographic data collected (see "Sampling of demographic data").

Together with WP 4 we then constructed a dynamic model that simulated the dynamics of species in the landscape. The model was a realistic, spatially explicit, and dynamic metapopulation model and by using this model we were able to examine how the distribution of target species among patches was affected by local population dynamics, and by short-distance and long-distance dispersal. As a baseline in simulations we used the current land use conditions. We were also able to investigate how land use history influences the current distributions. The effect of landscape development on future distributions and the possibilities of long-term persistence in the landscape were examined through different land-use scenarios.

Simulation results showed that the colonization and extinction dynamics in this agricultural landscape may be slow and the time frame for the population system to attain equilibrium in a constant landscape is very long. Hence, landscape history is important to interpret current distribution patterns. They also suggested that species only very slowly colonizes new habitats that are made available through changes in management. Sensitivity analyses demonstrated that the very small fraction of seeds dispersing over long distances have a large influence on the regional dynamics of species, whereas regular short-distance dispersal has almost no effect. The model also allowed us to assess how demographic processes affect not only local population growth but also regional dynamics.

Our analyses of the importance of the configuration of an agricultural landscape on the survival possibilities of plant species are central to biological monitoring and risk assessment. One insight from the models is that conservation efforts should focus as much on dispersal processes and landscape configuration as on local habitat conditions. The results are also important in the sense that they illustrate that the dynamics of many perennial plant species is slow and that therefore time lags are important. The response of the landscape to changes in land use may therefore be slow and the changes that have already occurred are only partly expressed in the current-day distribution.

These findings have important implications for assessing the effects of different management practices in agriculture, and show that it is not only important what management that is practiced a particular site but that also the landscape configuration of different management types play a role. From a research point of view our results are important because they suggest a way to study metapopulation dynamics also in systems with a very slow turn-over rates, thus being in non-equilibrium. The study system also provides unique opportunities to integrate, cultural geography, landscape history and ecology in education. Lastly, landscapes like our study system have high recreational values. These values are associated both with properties of local areas and properties of the landscape as a whole. To maintain these values we must therefore ensure that both local conditions and landscape configuration are such that the continued survival of key species is guaranteed.

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Reported by

STOCKHOLM UNIVERSITET
Lilla Frescativagen 5
106 91 Stockholm
Sweden
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