Physiological reactions of chestnut tree roots to acidic soils

Young chestnuts in Ticino. Foto: Yasuhiro Hirano (WSL).

Objectives

Large parts of European forests grow on acidic soils. In the last decades, however, inputs of acidifying substances to forest ecosystems have increased and have led to an acceleration of the acidification processes on sensitive sites. In particular, such sites are located in the southern part of Switzerland (Rihm 1994). On the basis of the concept of critical loads of acidity, the molar ratio of base nutrient cations to aluminium in the soil solution has been used as the parameter to assess acidification (Sverdrup and Warvfinge 1993, Cronan and Grigal 1995). During an observation period of over 10 years, a constant decrease was measured in a soil at Copera TI with values significantly below calculated critical loads (Blaser et al. 1999).

Aim

The aim of this project is to investigate whether roots of European chestnut (Castanea sativa) show physiological reactions to soil acidification processes. The following research questions should be answered:

• Which horizons within the soil profiles impede root growth?
• Which are the critical threshold values in the soils for the hindrance of root growth?
• Which physiological root parameters are suitable to detect effects of soil acidification to roots?

Methods

Field investigations: In field investigations at forest sites in the Ticino, chestnut fine roots originating from various soil horizons will be examined in order to measure the effects of soil acidification on the condition of the roots. Root parameters which will be investigated include molar Ca/Al ratio, activity of the respiration chain (TTC test), O₂-consumption, and starch content. In addition, a test to estimate the content of callose will be adapted from the literature and applied. Laboratory experiments: In pot systems using sand the reactions of the chestnut roots to toxic Al at various molar BC/Al ratios will be examined. The ratios will be 1, 0.3, 0.1, and a control. The nutrient solutions will be comparable to a soil solution, as well as the concentrations of free Al³⁺ ions measured with FIA or calculated with the model of Prof. E. Tipping, Centre for Ecology and Hydrology, Cumbria, UK.

Relevance for extension

The assessment of soil acidification in southern Switzerland is one of the key issues of the LWF programme. The physiological consequences of soil acidification processes on tree roots in the fields, however, are widely unknown. It is the aim of this project to develop physiological root indicators for the assessment of the effects of soil acidication processes. Chestnut trees in the Ticino area are becoming more and more respected, and efforts are undertaken to improve their cultivation and production. In Japan, the acorns of chestnuts are economically highly important. In addition, the chestnut trees are, as part of the Japanese culture, highly respected since several hundred years.

Finances

This project is financially supportet by FFPRI and the Japanese National Science Foundation

Publications

Hirano, Y., Mizoguchi, T., Brunner, I. 2007. Root parameters of forest trees as sensitive indicators of acidifying pollutants: a review of Japanese research. Journal of Forest Research 12, 134-142.
Hirano, Y., Brunner, I. 2006. Quantitative determination of callose in tree roots. Journal of Plant Physiology 163, 1333-1336.
Hirano, Y., Walthert, L., Brunner, I. 2006. Callose in root apices of European chestnut seedlings; a physiological indicator of aluminium stress. Tree Physiology 26, 431-440.
Hirano, Y., Graf Pannatier, E., Zimmermann, S., Brunner, I. 2004. Induction of callose in roots of Norway spruce seedlings after short-term exposure to Al. Tree Physiology 24, 1270-1283.