ABSTRACT
The landscape of extensively farmed countryside in Poland, as in France, is made up of a mosaic of agricultural plots linked to noncontiguous wooded areas of various sizes and shapes, sometimes connected to one another by hedges or wooded corridors. The ground survey consists in measuring the distance of each change in physiognomy, or even of facies, encountered in crossing a forest islet, from the starting point of a transect. With regard to areal frame sampling, if one wishes to describe the totality of land-cover types, it is necessary to use the technique of nonaligned systematic sampling of the areas under survey in order to make up the sample. The fragmentation of forest cover and its spatial organization have an effect on the plant biodiversity of the forest islets. Forest islets find themselves all the more easily enriched by migrating species since the places from which they come are nearby.
