Forest acid deposition impact

The impact of acid deposition on forests depends on the quantity of acidic components received by the forest system, the species present, and the soil composition. Numerous studies have shown that widespread areas in the eastern portion of North America and parts of Europe are being... 

When a forest system is subjected to acid deposition, the foliar canopy can initially provide some neutralizing capacity. If the quantity of acid components is too high, this limited neutralizing capacity is overcome. As the acid components reach the forest floor, the soil composition determines their impact. The soil composition may have sufficient buffering capacity to neutralize the acid components. However, alteration of soil pH can result in mobilization or leaching of important minerals in the soil. In some instances, trace metals such as Ca or Mg may be removed from the soil, altering the A1 tolerance for trees. 

The extent and severity of the damage attributable to acid depositions are difficult to estimate, since impacts vary according to soil type, plant species, atmospheric conditions, insect populations, and other factors that are not well understood. Nitrates in precipitation may actually increase forest growth in areas with nitrogen-deficient soils. 

The documentation of regional level terrestrial consequences of acid deposition is complicated. For example, forested ecosystems m eastern North America can he influenced by other factors such as high atmospheric ozone concentrations, drought, insect outbreaks and disease, sometimes from non-native sources. However there is a general consensus on some impacts of acidic depositon on both soils and forests m sensitive regions. 

The present decay of many German and other European forests as a result of the impact of air pollution, especially photochemical pollutants and acidic deposition. 

Atmospheric deposition has been repeatedly shown to be the major source of sulfur deposition in many forest ecosystems, especially in regions significantly impacted by acid deposition (Mitchell et al., 1992b). Sulfur inputs to forests derived from mineral weathering generally play a minor role however, this is dependent upon the local geology. Regions underlain by sulfide-rich... 

While the impacts of acidification on fish are the main concern in Scandinavia and North America, damage to planted coniferous forests at high elevation sites in central Europe is critical. For example, in the Czech Republic —10 ha of Picea abies have died, and more than 50% of the forest has suffered irreversible damage (Moldan and Schnoor, 1992). Acid deposition and elevated ozone levels are predisposing factors for damage to tree crowns. 

Taiwan Forest ecosystems. A RAINS-ASIA impact module is used to assess ecosystem sensitivity to acid deposition and to calculate critical load of sulfur to six forest ecosystems in Taiwan (Lin, 1998). Results indicate that forest ecosystems in Taiwan are very sensitive to acid deposition due to their low soil pH (< 5.5). Lowland subtropical forest ecosystems in Taiwan have low or moderate low critical loads for S suggesting that they are vulnerable to acid deposition (Table 5). 

Some years ago the first reports appeared on forest die-back in heavily polluted areas. The impact of this information drew the attention on the situation of local forests, which encouraged research on acid deposition in many countries. The quantitative evaluation of damage and the monitoring of forest quality are difficult. Most theories have been based on visual inspections however, trends, actual damage and local effects can only be estimated on the basis of scientific measurements, enabling to make correlations between damage and measured pollutant concentrations. A prerequisite for this evaluation is the availability of representative CRMs. The BCR has hence developed for this purpose two reference materials, namely beech leaves and spruce needles, which have been certified for nutrients (e.g. Ca, Mg, K, P and N) and indicator elements (e.g. S, Cl, A1 and Mn) [17-19],... 

Rehfuess, K.E. (1989). Acidic deposition - extent and impact on forest soils, nutrition, growth and disease phenomena in central Europe a review, fater. Air, and Soil Pollution 48, 1-20. 1987 5... 

After about three decades of extensive research on acid deposition some of the effects of acidity in regions devoid of any buffering capacity are well known. Leaching of calcium and mobilization of toxic aluminum from soils and often profound changes of plant and heterotrophic species composition in lakes, including the demise of the most sensitive fishes, amphibians and insects, are the most deleterious and indisputably established impacts. In contrast, the exact role of acid deposition in the reduced productivity and dieback of some forests remains uncertain. ... 

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