Silvicultural interventions alter forest characteristics such as stand structure, tree species composition and developmental stage. These forest characteristics in turn influence the quality and quantity of public goods and services a forest provides, such as space for recreation, clean water, and air purification. In this paper, we use a forest growth simulator and a geographical information system (GIS) to assess the effects of three silvicultural strategies on recreational suitability, water purification potential and air purification potential in a peri-urban catchment in Switzerland. For each of the three services, an index was developed to capture the suitability of a stand for providing the service. The growth simulator SILVA 2.2 was used to project forest development over 50 years under the three silvicultural strategies BU 'business as usual' (small patch cuts, Swiss selection system), NI 'no intervention', and MA 'mass production' (clearcuts and plantations of Picea abies). In all three strategies, road maintenance continued. The outputs of SILVA 2.2 were transferred into the GIS. Indices for the three services were calculated and aggregated over the study area.
The development of the indices for all three services mainly reflected the changes in developmental stages and in the spatial patch distribution as a result of silvicultural interventions. No single strategy resulted in maximum values for all three indices. Recreational suitability was highest with the BU strategy and lowest with the MA strategy. The latter was due to the conversion of broad-leaved forests into plantations. Water purification potential was captured as nitrogen (N) storage in tree biomass and N removal by timber harvesting. In these nearly N-saturated forest ecosystems, the water purification potential was generally highest with the BU strategy, and lowest with the NI strategy. The air purification potential was higher with the NI than with the BU strategy. With the MA strategy, it rapidly decreased at the beginning, but increased after 30 years and surpassed the other strategies as soon as most of the plantations had reached the pole stage.
The NI and MA strategies presented are clearly extreme strategies, which could not realistically be applied to the whole catchment as so many different owners are involved. However, the results of our study can be used to show to what extent management activities affect goods and services. We propose using such tools more often in forest planning processes to support the development of land-use visions and policies on a regional scale.