A field based study was carried out, investigating the effects of increased acid deposition on soil, soil solution chemistry and the fine roots of Pinus sylvestris growing on a podzol. An addition of sulphur at a rate of 15 Kg/ha/yr above ambient deposition was observed to:
The cause of the reduction in fine root growth was more likely to be cation depletion and high proton and ammonium concentrations due to the acidification treatment, rather than increased aluminium availability in isolation.
The critical threshold of aluminium in solution for fine root functioning was identified between 2.5 and 5 mg/l. The aluminium threshold, was based on the inhibition effect of aluminium on fine root growth, nutrient status and seedling phosphorus uptake in controlled environment studies.
The fine root response to the main soil-mediated factors (soil moisture, temperature and soil solution chemistry) and their fluctuation was also evaluated under natural environmental conditions. This study showed that:
Acid deposition is one of the major anthropogenic factors affecting the stability of forest ecosystems. The increase in acid deposition has been associated with an increase in soil acidification and Al mobilisation in forest soils, which is believed to be a threat to forest vitality through its effects on fine roots. A direct effect of aluminium toxicity on fine roots was identified in a number of controlled environment experiments, but was not verified under field conditions. Aluminium toxicity is ameliorated by calcium, and the soil solution calcium to aluminium (Ca:Al) ratio was proposed as a better indicator for evaluating aluminium toxicity. Tissue Ca/Al molar ratio was also postulated as a better indicator than aluminium alone.
The results will show if fine root data can complement soil and foliage indicators in evaluating site conditions and environmental change.
There is now a European Concerted Research Action designated as COST E38 on “Woody root processes under changing environment” with three working groups discussing:
Soil acidification and fine root response of Scots pine
Vanguelova, E.I. (2002).
Unpublished PhD thesis, The University of Reading, UK.