Changes in Soil Solution Chemistry, Seepage Losses, and Input–Output Budgets at Three Beech Forests in Response to Atmospheric Depositions

Abstract

Atmospheric depositions have increased substantially since industrialisation and have affected many forest properties. Forest soils of low buffering to the acid load as those of sandy or silty texture significantly declined in soil pH and some essential nutrients during the last decades (see Chap. 21) causing a controversial discussion about the stability of such forest ecosystems (Ulrich 1981, 1987, 1992, 1994b). Of 1,700 soils studied in the forest soil survey programme of Germany, 60% of all soils have pH(H2O) <4.2 (Wolff and Riek 1997a, b). N deficiency, which has been a common feature of forest stands in the temperate region (Tamm 1991), does not occur any more due to high N deposition rates in Europe (except of north and east Europe). On the contrary, the N supply has increased as indicated by high N contents of the tree foliage and surface organic layer samples (Tietema and Beier 1995; Alewell et al. 2000b; McNulty et al. 1991; Wolff and Riek 1997a). Nitrate losses with seepage water have increased at some locations (Dise and Wright 1995; Bredemeier et al. 1998; Matzner et al. 2004; Borken and Matzner 2004), which led to a discussion about the saturation of forests with nitrogen (e.g. Agren and Bosatta 1988; Tamm 1991; Gundersen et al. 1998; Aber et al. 1998). However, political actions by European countries have led to a noticeable decline in atmospheric depositions of sulphur and nitrogen in the 1980s and 1990s (Ferrier et al. 2001) raising questions about the recovery of forest ecosystems from soil acidification. A general recovery of alkalinity of lakes and streams was observed in all regions of Europe in the 1990s (Stoddard et al. 1999) except at many sites in central Europe where a significant delay in aquatic recovery from acidification (Alewell et al. 2000a) was observed. Recovery of water acidification can take decades, because of the release of previously stored sulphate from soils with a high storage capacity for sulphate continues leading to acidification of aquatic systems (Matzner 2004). Moreover, many of the European forest stands are experiencing changes due to the so-called “climate change” phenomenon. For example, significant changes in the climate at the Solling site with increased air temperature and precipitation have been recorded since the Solling project was established in 1966 (see Chap. 2). All these impacts on forest ecosystems constitute the basis for extensive research for which the most promising tool is the long-term monitoring of element budgets of representative ecosystems. This allows one to follow forest development under changing environmental conditions.