The objective is to investigate the effects of acid deposition on soils and ecosystems by means of experimental manipulations.
Experimental manipulations of the biogeochemical cycles and water balance in forest ecosystems are conducted at 5 sites in Europe. Although the manipulation experiments have started in different years and on different backgrounds, the joint project has developed a high degree of intercomparability. The basic idea and project design is to perform the same or comparable manipulations of the forest ecosystem under different soil conditions, atmospheric loads and climate. The sites are: Klosterhede (Denmark) and Hoeglwald (Germany), both with medium atmospheric input of sulphur and nitrogen; and Solling (Germany), Harderwijk and Kootwijk (The Netherlands), all 3 with high atmospheric input of sulphur and nitrogen. As a reference station, without experimental manipulations, Ballyhooly (Ireland) with low atmospheric input of sulphur and nitrogen.
The manipulations comprise fertigation to arrive at optimal soil chemical conditions (both macro and micro nutrients) and water supply for tree growth. Those manipulations are different from general fertilizer trials, since application is performed in small doses by a sprinkler system according to the demands of the trees. A similar sprinkler system is used for irrigation and experimental acidification with strong acids. Liming and traditional fertilization experiments are run in parallel at some of the sites. A major part of the manipulations are devoted to the removal of atmospheric inputs of elements, strong acids and water by the construction of roofs beneath the canopy. These roof experiments are designed to measure the response, at the ecosystem level and under controlled conditions, of a possible reduction of atmospheric inputs of air pollutants (reversibility of acidification) and water (drought). Apart from the control plot(s), at least 2 types of manipulation are performed at each site. To reduce verlap no attempt has been made to include all types of manipulation on each site.
At each location, the same parameters are measured, and full data exchange exists among the partners. That means that every group can apply its particular models to the data from all sites or, vice versa, that models developed by different partners can be applied to the same data set. As far as possible the same methodology and analytical techniques are used. However, since some methods have to be retrospecitvely referable to other studies on a given site, they have occasionally been retained. In a few instances this has lead to double instrumentation to obtain comparable data.
Funding SchemeCSC - Cost-sharing contracts
6701 AR Wageningen