Root parameters of forest trees as sensitive indicators of acidifying pollutants: a review of research of Japanese forest trees

Abstract

The root parameters of forest trees can be indicators of a changing environment. We summarize the results of root studies with regard to the effects of acidifying pollutants, especially soil acidifi cation and aluminum toxicity, on various root parameters of Japanese forest trees under experimentally controlled conditions. All root parameters such as biomass, morphology, nutritional status, and physiology can be regarded as indicators, because, under laboratory conditions, root responses occur prior to the responses in the aboveground parts. However, considering the conditions of forest sites, the nutritional status and physiological changes are better indicators of soil acidifi cation and Al stress than the biomass and morphological response. The currently available data suggest that the most important indicator is the Ca/Al molar ratio in roots of Japanese tree species. In order to predict and detect the initial effects of soil acidifi cation, we postulate that the specifi c root response to the Ca/Al molar ratio of tree roots should be considered as a parameter for use in long-term forest monitoring sites.

Limiting factors in the detection of tree roots using ground-penetrating radar

“…Using a combination of GPR with frequencies ranging from 400 MHz to 1.5 GHz may more accurately detect tree roots greater than 5 mm. However, fine roots less than 2 mm, which are good indicators of environmental stress (Hirano et al 2007), cannot be detected using GPR (Stover et al 2007).…”

Special feature: development and function of roots of forest trees in Japan

“…Two additional articles describe the sensitivity of fi ne-root tips to soil acidifi cation (Hirano et al 2007) and to simulated drought . Hirano et al (2007) review laboratory experiments demonstrating responses of roots of both coniferous and broad-leaved species to acidifying pollutants. In general, the responses, such as changes in root biomass, morphology, and nutrient contents, occurred prior to those of aboveground parts.…”

“…In particular, white roots or the number of white-root tips can be useful as an indicator. Because these parameters have rarely been reported in fi eld conditions in Japan (Hirano et al 2007), it would be fruitful for future studies to accumulate data on the response of fi ne-root tips to environmental stresses in fi eld conditions such as the study on drought stress by Konôpka et al (2007).…”

Fine root traits in Chamaecyparis obtusa forest soils with different acid buffering capacities

“…Several experimental studies have revealed how the biomass and morphology of tree fine roots change in soils of varying acidity, low pH, low concentrations of BC, and high concentrations of Al (see review papers, Andersson 1988;Cronan and Grigal 1995;Hirano et al 2007; Vanguelova et al 2007;Brunner and Sperisen 2013). Field investigations on these topics conducted in mature forests in Europe and North America have found that acidified soils led to the destabilization of root systems, a decrease in living fine roots, and an increase in dead/live fine roots (Schulze 1989;Joslin and Wolfe 1992;Persson 1992;Persson 1993, 1995;Matzner and Murach 1995;Persson et al 1995).…”