Fruit tree ecosystem service provision and enhancement.

The paper deals with the qualitative valuation of services provided by fruit tree ecosystems in an ecological engineering context. Thereby, the state and spatial occurrence of various fruit tree species and varieties are assessed, the services that they confer to people are evaluated, and recommendations are made on strategies aiming at enhancing their services. In the community of Vaduz, principality of Liechtenstein, the position of 1445 fruit trees including 77 small apple plantations with modern varieties has been recorded. Experts identified 200 apple and 59 pear varieties, and assigned the fruits to one of three quality and rareness categories. The diversity of apple is higher than the diversity of pears, and there are indications for a high diversity of the Prunus spp. The current 720 patches on agricultural land are composed of 361 trees, some small apple plantations, and 359 hedgerow point measurements; display 258 840 connections and yield connectivity indices for dispersal coefficients of little mobile birds and butterflies, respectively. Four strategies to place 75 additional trees for connectivity enhancement have been evaluated. They all lead to higher overall connectivity relative to the current connectivity, but the establishment of an orchard provides the highest gain in relative connectivity. The second best result is obtained by randomly placing the trees into open agricultural land. The strategy of planting the trees for shade provision along roads and paths yields a result similar to a strategy with placement of trees on transects through open agricultural land. The strategy of planting trees along paths and roads is preferred since interference with agricultural activities is smallest. In a metapopulation context, the connectivity for representative taxa should be seen as a necessary but insufficient parameter for species conservation purposes in particular and biodiversity augmentation in general.