20 Jahre ökologische Aufwertung von Waldrändern im Kanton Aargau: erste Erfolgskontrolle

Abstract

20 years of ecological forest edge enhancement in the Canton of Aargau: a first evaluation On the Swiss Plateau, 25 000 km of forest edges serve as transition zones between open grasslands and closed forests. They fulfil important functions with regard to ecological connectivity and constitute a habitat for numerous plant and animal species. Since only a fraction of these forest edges are in good ecological condition, most cantons implement programs to enhance their quality. With almost 200 km of upgraded forest edges, the Canton of Aargau takes on a pioneering role throughout Switzerland. To date, however, it was unknown what ecological value the upgraded forest edges have and which factors significantly contribute to the success of the implemented measures. We used a standardised evaluation key and interviews with the responsible forest services to assess the ecological quality of 20 selected forest edges in six forest districts in the Canton of Aargau as well as potential success factors. Our investigations show that enhanced forest edges in the Canton of Aargau are in a very good condition. The two most important structural elements of a forest edge in terms of biodiversity are two to eight times more marked than on average on a national scale, and they nearly conform to the objectives as defined by nature conservancy. With a registered total of 31 domestic deciduous tree species and 58 domestic lignified plant species, floristic diversity is remarkably high. Contrary to the estimation of the responsible forest services, neither the vigour of a location nor its aspect proved to be decisive factors of success. Rather, the frequency of intervention seems to be critical. Maintenance measures should be implemented at least every seven years. More comprehensive analyses are necessary to corroborate the present findings for other regions in Switzerland. Precondition for such analyses are systematic performance reviews that include an examination of the baseline conditions.