EXPERIMENTAL-EVIDENCE FOR THE RELATIVE SENSITIVITY OF DECIDUOUS FOREST PLANTS TO HIGH SOIL ACIDITY

Thirteen species of deciduous forest vascular plants were established from seeds: Brachypodium sylvaticum, Carex sylvatica, Circaea lutetian a, Deschampsia flexuosa, Galium odoratum, Lamium galeobdolon, Lathyrus vernus, Luzula pilosa, Milium effusum, Poa nemoralis, Sanicula europa ea, Stellaria holostea and Stellaria nemorum. An acid beech forest soi l was variously treated with carbonates (CaCO3 + MgCO3 or SrCO3) to ob tain a soil solution pH of 3.3-5.2. The experimental results were comp ared with the field distribution of the same species in 230 south Swed ish deciduous forests with regard to soil pH. In general, the species reacted to increasing soil pH in accordance with their field distribut ion. Addition of SrCO3 was almost equally effective as CaCO3 + MgCO3 ( both at pH 4.2 in the soil solution) in promoting establishment and gr owth, whereas most species failed in the untreated soil (pH 3.3). Ther e were no indications that the Ca or Mg concentrations of the soil sol ution were below minimum or even suboptimal for plant growth in the un treated soil. Within the pH range (pH less-than-or-equal-to 3.5-4.3) w hich proved critical to establishment and growth in most of the specie s, the reactive Al3+ concentration of the soil solution did not vary s ignificantly. It is suggested that the high acidity of the rhizosphere solution, possibly aggravated by Al3+, obstructed the uptake or reten tion of mineral nutrients by the roots in the untreated acid beech for est soil.