Edward I. Sucoff

Aluminum toxicity in forests exposed to acidic deposition: The ALBIOS results

The ALBIOS project was conducted to examine the influence of acidic deposition on aluminum transport and toxicity in forested ecosystems of eastern North America and northern Europe. Patterns of aluminum chemistry were evaluated in 14 representative watersheds exposed to different levels of sulfur deposition. Controlled studies with solution and soil culture methods were used to test interspecific differences in aluminum sensitivity for one indicator species (honeylocust - Gleditsia triacanthos L. ) and six commercial tree species (red spruce - Picea rubens Sarg., red oak - Quercus rubra L., sugar maple - Acer saccharum Marsh., American beech - Fagus grandifolia Ehrh., European beech - Fagus sylvatica, and loblolly pine - Pinus Taeda L. ). Overall, red spruce was the tree species whose growth was most sensitive to soluble aluminum, with significant biomass reductions occurring at Al concentrations of approximately 200–250 umol/L. Analyses of soil solutions from the field sites indicated that the conditions for aluminum toxicity for some species exist at some of the study areas. At these watersheds, aluminum toxicity could act as a contributing stress factor affecting forest growth.

Response of honelocust (Gleditsia triacanthos L.) to soil solution aluminium

Honeylocust (Gleditsia triacanthos L.) seedlings were grown for 72 days in soil from a BC horizon of a Spodosol altered by adding four levels of AlCl3. Saturated paste extracts from controls to the highest AlCl3 treatment contained, respectively, 85 to 831 μM Al, 834 to 163 μM Ca and 316 to 35 μM Mg and had a pH of 4.4 to 4.0 Leaf, stem, and root concentrations of Al and P increased while those of Mg, Ca, and Zn decreased with increasing levels of Al. Growth decreased as Al, Al/Ca, and Al/Mg ratios in the extract increased. Growth was negatively related to tissue concentrations of Al, P, and Zn and positively related to tissue Mg and Ca. Growth was more closely correlated to elemental concentrations in the saturated paste extracts than in the SrCl2 extracts (1 part 0.01M SrCl2: 1 part moist soil).

Responses of quaking aspen seedlings to solution calcium and aluminum

Abstract Quaking aspen (Populus tremuloides Michx.) seedlings were grown in nutrient solutions to study their responses to various levels of calcium (Ca) and aluminum (Al) in four experiments. In solutions with 100 to 2500 µM Al, seedlings had visible symptoms of Al toxicity and/or Al‐induced deficiencies of Ca or phosphorus (P). The symptoms became more prominent with increasing solution Al, and less prominent with increasing solution Ca. Elongation of shoots and roots declined significantly with increasing solution Al, and usually increased with increasing solution Ca. Therefore, elongation of shoots and roots was closely related to ratio of solution Ca/Al. The molar ratio of solution Ca/Al associated with 90% of maximum elongation was 0.23 for shoots and 1.86 for roots. The levels of solution magnesium (Mg) and NH4 did not significantly affect the response of aspen to solution Ca/Al ratio. Concentrations of leaf Ca, nitrogen (N), and Mg as well as root Ca, potassium (K) and Mg decreased as solution Al increased, whereas leaf Ca, N, and P and root Ca and K usually increased with increasing solution Ca. Adding Al into solutions increased leaf and root Al. Shoot elongation was positively and closely related to the root Ca/Al ratio, while root elongation was positively and closely related to root Ca. In addition, aspen growth was significantly related to tissue N and K. These relationships indicate that Ca deficiency was a primary, but probably not the sole cause of growth reduction in solutions with high Al.

RESPONSES OF POPULUS TREMULOIDES SEEDLINGS TO SOLUTION pH AND CALCIUM

Quaking aspen (Populus tremuloides Michx.) seedlings were grown in solution culture to investigate their response to a range of solution pH (3.3, 3.5, 3.7, 3.9, and 5.0) at two levels of solution Ca (25 and 250 μM). Both shoots and roots showed visible abnormalities at lower levels of solution pH and Ca. Growth increased significantly with increasing solution pH at both levels of solution Ca. Regardless of solution pH, seedlings were larger at 250 μM Ca than at 25 μM Ca. The results suggest that high solution Ca ameliorated the adverse effects of low pH on growth. Concentrations of leaf P, K, Ca, and Mg and root K, Ca, and Mg usually increased with increasing solution pH. At pH 3.9 and 5.0, concentrations of leaf P and Ca and root Ca were higher at 250 μM Ca than at 25 μM Ca. Shoot elongation was positively related to concentration of leaf P, and root elongation was positively related to concentrations of leaf P and Ca and root Ca. These results suggest that high solution Ca ameliorated the adverse effects of low pH on growth possibly by alleviating P and Ca deficiencies.