Aluminium toxicity and magnesium uptake in spruce forest

In response to the problems in quantifying the effects of aluminium in plant nutrient uptake and growth as mentioned in the previous post, De Wit et al. (2010) specifically measured the effects of dissolved al on mg uptake in Norway spruce forests, in a long term field manipulation experiment from 1996.

Table from De Wit et al. (2010) showing the changes to BS after the addition of dilute aluminum carbonate into soil. 

The sites chosen were homogeneous-sandy soils with low al and n concentrations and Norway spruce stand. Dilute aluminium carbonate was added to 12 adjoining plots during snow and frost free seasons. Frequent measurements of soil at O horizon, pine needles and bark samples, crown density and color were observed and taken for analysis.

BS at O horizons were found to have significantly decreased while exchangeable al increased after 3 years of treatment. Mg in needles were also found to be reduced as compared to the control.

However, De Wit et al. (2010) found no significant impact of al on tree volume, crown, density annual increment and height increment. Plant root growth was not affected as hypothesized by many researchers. Only reduced mg uptake was significant, and this is not due to fluctuations in mg in soils. This mg deficiency has been reported in Lehstenbach, Germany by Alewell et al. (2000) but in nutrient poor soils.

Despite reports of al toxicity, it seems that spruce trees are more tolerant to acid deposition than previously thought. Similar experiments should be carried out in other areas to verify al toxicity levels in plants. However, this is a challenge to tropical areas as the vegetation is much more heterogeneous in a given area. Field experiments will need to be aided with laboratory experiments to test al sensitivity for all types of vegetation in a given area in order better quantify the effects of al in tropical regions.

References:

De Wit, H.A., Eldhuset, T.D. and Mulder, J. (2010) Dissolved Al reduces Mg uptake in Norway spruce forest: Results from long-term field manipulation experiment in Norway. Forest Ecology and Management. Vol. 259, pp. 2072-2082.

Alewell, C., Manderscheid, B., Gerstberger, P., Matzner, E., 2000. Effects of reduced atmospheric deposition on soil solution chemistry and elemental contents of spruce needles in NE-Bavaria, Germany. Journal of Plant Nutrition and Soil Science—Zeitschrift Fur Pflanzenernahrung Und Bodenkunde 163, 509-516.