Leaching of solutes by the action of acidic rain: a comparison of efflux from twigs and single needles of Picea abies (L. Karst.)

Abstract

Abstract. Leaching of inorganic cations (K+, Mg2+) and in some cases of inorganic anions and sugars from detached twigs and single needles of spruce Picea abies L. Karst.) in the presence of acid rain (H2SO4, 1 mol m−3) or salt solutions (Na2 SO4, 1 mol m−3) was examined under laboratory conditions. Cation leaching (as percentage of the total water soluble ion content of the tissue per hour) was: K+: 0.01‐0.02%; Mg2+: 0.005‐0.01%; Ca2+: 0.1‐0.2%. Leaching rates of anions were even lower than that and concentrations in the leachate were often below the detection limit of anion chromatography. Spraying with H2SO4 (pH 2.95, 1 mol m−3) increased leaching only transiently. Similar effects were found when Na2SO4 was used instead of H2SO4. The transiently enhanced leaching was apparently due to H+/cation or cation/cation exchange at the twig or leaf surfaces. Feeding of K+ or Al3+ through the stems increased leaching of all cations within a few hours, again demonstrating rapid ion exchange in the apoplast. Leaching of potassium and magnesium from single needles occurred at similar relative rates as from twigs. Loss of Ca2+ ions, however, was even smaller from needles than from twigs. Apparently, a large part of the Ca2+ lost from twigs originated from the bark and not from the needles. Efflux of ions from longitudinal needle sections was about 1000 times taster than the rates obtained with intact needles, indicating that the cuticle was the main barrier Preventing solute loss. In relation to the total amount of mineral nutrients in trees, leaching is considered to be too small to be the primary cause of damage to trees stressed by acid rain, as has been suggested in the literature.

Canopy throughfall of Picea abies (L.) Karst. as depending on trace gas concentrations

“…This rate seems to be small in the field since the trace gas composition of SO2 polluted air moving from the front side of spruce or pine canopies to the other side essentially remained unchanged at dry days (Lampadius 1968). The deposition of acid mist, dissolution of SO2 on wet canopy surfaces etc., is assumed to enhance cation throughfall from tree canopies (Adams and Hutchinson, 1987;Bal~izs, 1991;Evans and Curry, 1979;Fairfax and Lepp, 1975;Kreutzer and Bittersohl, 1986;Leonardi and Fliickiger, 1989;Lutz, 1987;Mengel et al, 1987;Mitterhuber et al, 1989). After formation of HNO3 similar consequences are expected also for nitrogen oxides (NOx).…”

Influence of pH and plant nutrient status on ion fluxes between tomato plants and simulated acid mists

“…The temporal behaviour of ion fluxes during wetting events may also indicate whether significant element depletion is occurring, as revealed by the experiments of Mitterhuber et al (1989). Under conditions where ions were not accumulating in surface moisture and soluble spruce foliar ion pools were large compared to fluxes, effluxes of K+, Ca^"^, and Mg^"^ were constant during 80 h of exposure to mists at pH 2-95 or 5-8.…”

Pine needle growth and fine structure after prolonged acid rain treatment in the subarctic

“…This effect on both shoot and needle growth first became evident after 6 years of treatment, and persisted over the 2 subsequent years independently of effective temperature sums or precipitation during the growing season. The effect was only significant when compared with the DC trees, however, possibly as a result of irrigation-induced leaching of nutrients from foliage (Mitterhuber et aL 1989). The literature on conifer seedling growth responses to acid rain shows that the initial stimulation of height growth is often followed by a reduction in growth after prolonged treatment, when the deposition is allowed to reach the soil (e.g.…”