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Long-Term Changes in Flora and Vegetation in Deciduous Forests of Southern Sweden
No. 44, Effects of Acid Deposition and Tropospheric Ozone on Forest Ecosystems in Sweden (1995), pp. 215-226
Published by: Oikos Editorial Office
Stable URL: http://www.jstor.org/stable/20113164
Page Count: 12
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This article focuses on south Swedish research on soil acidification and its impact on field-layer vegetation in beech Fagus sylvatica, oak Quercus robur and hornbeam Carpinus betulus forests. Soil acidification has occurred since at least the 1950's and is of such magnitude that it has been detected over a period of only 10 yr. Acidification can be quantified as a lowering of soil pH, most pronounced in soils with originally high pH. The cations are leached out of the soil and the pools available to plants decrease gradually. The average annual decrease in recent decades has been 1%. Changes in the occurrence of vascular plants have been investigated mainly by repeating earlier vegetation analyses after 10, 30, 40 and 60 yr. Many typical field-layer species of deciduous forests have been negatively affected, both quantitatively and qualitatively, during recent decades, especially in soils which have become too acid for them. The more intense management of beech forests today has, among other things, allowed certain weed species to establish themselves. If management trends continue in this direction, these species may become part of the "natural" species composition of these forests. The doubled N-deposition since the 1950's is another factor that, until now, seems to have led to a higher diversity and abundance of several species in deciduous forests. Nowadays N is available in excess in many south Swedish forest soils and NO₃ may leach out of the soil, leading to further acidification and accelerated leaching of other nutrients. The form of inorganic N available to plants may limit growth. Acid soils have a lower nitrification potential and NH₄ as the sole N-form may be inadequate for plants usually growing in less acid soils. For some species the hydrogen ion concentration per se seems to be crucial, but decreased growth and survival may also result from a high Al concentration or Al/Ca ratio.
Ecological Bulletins © 1995 Oikos Editorial Office