R. Mayer

Chemical changes due to acid precipitation in a loess-derived soil in central Europe.

In a stand of Fagus silvatica in the Solling highlands, Federal Republic of Germany, we followed the effect of acid precipitation on chemical soil state and the ion fluxes in the ecosystem between 1966 and 1979. As indicated by increasing aluminum concentration in the soil solution and an increase in organic matter storage in the forest floor, for example, the soil shifted during the measuring period from one state toward another one. During this transition, the acid precipitation has induced soil internal H+ ion production, partly by accumulation of organic matter poor in nitrogen, and partly by a probable change in the type of nitrogen nutrition. Two-thirds of the H+ ion buffering is due to the dissolution of polymeric hydroxoaluminum, resulting in the formation of solid AlOHSO4 and the leaching of Al ions. There are indications that the Al concentration in soil solution reaches toxic levels for the stand. The findings may have serious consequences for forestry in central Europe.

Acidity of precipitation as influenced by the filtering of atmospheric sulphur and nitrogen compounds — its role in the element balance and effect on soil

Acidity of throughfall precipitation is increased by the filtering of S and N from the atmosphere by trees. An element balance for a beech forest is given. As a consequence of acidification the soil chemical conditions are changed in a way that plants rooting close to the soil surface are affected. Losses of nutrients may pose a problem in forest plant nutrition in the near future in Central European forests on light or medium textured acid soils.

Input, Output und Interner Umsatz von Chemischen Elementen bei einem Buchen- und einem Fichtenbestand

The element flux balance measured over a period of 4 years in a beech and a spruce stand is given. By the use of measured data two element fluxes are calculated: the leaching of salts and metabolic substances from the canopy by precipitation (part of the internal turnover), and filtering of atmospheric substances by impaction with the forest canopy (atmospheric input). With these data the flux balance for the forest ecosystem is complete, element uptake by roots included.

Atmospheric pollution in a tropical rain forest: effects of deposition upon biosphere and hydrosphere II. Fluxes of chemicals and element budgets.

Three rain forest ecosystems in the Serra do Mar, theatlantic coastal mountain range of Brazil, have beeninvestigated in the frame of an interdisciplinaryGerman-Brazilian research project on dispersion,transformation and deposition of air pollutants in andaround the industrial area of Cubatão. Part I ofthis paper gives a description of the overall goals ofthe project, the area of investigation, and thematerials and methods used. It reports on the resultsof the field measurements conducted from 1991 to 1995,covering concentrations of chemicals in precipitation,soil water, surface water and litter fluxes. In thepresent paper, part II, the element fluxes arepresented with calculated concentrations in thetransport media (precipitation, seepage water,litterfall) and their respective flow rates. Elementbudgets for the ecosystem and for the soil compartmentare interpreted with respect to turnover of chemicals,including nutrients, in forest vegetation, and toprocesses of soil acidification.The forests under investigation are characterized bya very high input from the atmosphere. Between 100 and200 kg S ha-1 are annually carried into soil byprecipitation in the form of sulfate, 20 to 70 kg ofnitrogen mainly in the form of ammonium, 3 to 24 kg offluoride. Input of ammonium and organic bound nitrogenis followed by nitrification in the top soil. At themost polluted site, nitrate output with seepageamounts to 300 kg N ha-1 yr-1, sulfate output tomore than 400 kg S. Soil acidification associated withturnover of sulfur and nitrogen is followed by therelease of aluminum from soil minerals, and leachingof ionic forms of Al (up to 280 kg Al ha-1annually). Transfer of aluminum ions to groundwaterand surface water can have serious ecologicaleffects. Alkalinity is consumed, and the water issubject to acidification.

Calculation of Deposition Rates from the Flux Balance and Ecological Effects of Atmoshperic Deposition upon Forest Ecosystems

Total wet and dry deposition of main and trace elements is calculated from the flux balance for precipitation fluxes of forest canopies for which precipitation fluxes above and below canopy as well as the flux coupled with litterfall has been measured. Retention and leaching of substances are estimated for groups of elements individually showing similar chemical and physiological behavior. It is shown that dry deposition may be very important and may even exceed wet deposition to forests in rural areas. Dry deposition rate in the same area depends clearly upon forest type, i. e. upon the surface quality. Ecological consequences of atmospheric deposition to forests are discussed.