Forschungs- & Entwicklungsinformationsdienst der Gemeinschaft - CORDIS

Building GIS model

The objective of this task was to provide a basis for analyses of different aspects of landscape configuration on species distribution and diversity. A GIS model is constructed as different layers of information each bearing a specific content, where the information is spatially explicit. The information layers were species distributions, vegetation, geomorphology and land use. Species distributions were based on field surveys where each of the four target species, Succisa pratensis, Tragopogon pratense, Ranunculus bulbosus and Carlina vulgaris were mapped in the study area, Nynäs nature reserve, southern Sweden. The maps of the target species where imported to a GIS-framework using the software Arcview.

Present day vegetation was inferred from aerial photographs, and the classification was verified in the field. Geomorphology consisted of topography, soil and bedrock, and was imported from existing geomorphological maps. Land use history was extracted from cadastral maps dating back to the 17th century and from aerial photos from the 1940s and onwards. The history of the landscape includes a general decline in traditionally managed grasslands, which has either developed into forest or been used for agricultural fields. During the last decades many fields have again been transformed to pastures, which implies that there are different categories of grasslands, traditionally managed (un-fertilized and not ploughed) and recent grasslands, i.e. former fields.

This land use change has severe effects on the distribution and dynamics of species, and these effects have been subject to both descriptive and analytical studies; the latter using population models. Species response to land use change is basically a result of changing amount of suitable habitats in the landscape, and the actual configuration of habitats in the landscape. Species may however, due to time lags in either colonization or extinction processes, have a distribution that deviates from what would be expected from the landscape structure. Colonization time lags are due to dispersal limitation, i.e. species are not able to colonize all available suitable sites. Extinction time lags are due to persistent life-cycle stages, for example dormant seeds, clonal propagules or long-lived vegetative plants.

Descriptive analyses of species distributions in relation to habitat characteristics suggest that the target species mainly occur in traditionally managed sites or in sites that have been managed, mainly by grazing, over the last 50 years. For one species, Succisa pratensis, the distribution pattern today reflects the distribution of semi-natural grasslands in the 1940s, whereas the occurrences of the species in relation to present vegetation is approximately equally distributed among grasslands and forest. This implies that there is likely a time lag in the response of this grassland species to ongoing land use change. Such a time lag has also been supported by simulation models performed in collaboration with work package 4 (Tomás Herben, University of Prague), which are further described in the summary of the task "Analysis of landscape configuration".

There are several implications of these results. For assessment and monitoring of plant biodiversity in the landscape, it is essential that the non-equilibrium state of species occurrence be acknowledged, otherwise surveys may be misleading, and conservation programmes may fail to reach their goals. Moreover, the results suggest that conservation of biodiversity must account for landscape level processes and not only focus on target sites, "biodiversity hotspots". The results suggest that land use history must be much more in focus of spatial analyses of plant biodiversity, and that explicit knowledge of historical change provide an indirect assessment of the time-scale of the response of plant species to land use change. For agriculture the results imply that it would be favourable to preserve traditional management, e.g. grazing on all still existing semi-natural grasslands, but also that the surrounding landscape should be used for extensive grazing, to promote dispersal of species and development of new populations. Conservation programmes should increase focus on whole landscapes. Economically sustainable systems for maintaining grazing, and for cooperation among farmers in order to increase the extent of grazed areas, should be developed. Such landscapes will also promote recreational values of landscapes.

The results will also be valuable for research on regional plant population dynamics, as there are still relatively few analyses combining demography, regional dynamics and land use history. We foresee that there is also a value for education, both for schools and for higher education at universities. The interface between ecology, history and cultural geography is also enhanced by the results of these studies.

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