Soil base saturation affects root growth of European beech seedlings^§

Abstract

To assess the potential effects of Al toxicity on the roots of young European beech (Fagus sylvatica L.), seeds were sown in soil monoliths taken from the Ah and B horizons of forest soils with very low base saturation (BS) and placed in the greenhouse. The Ah horizons offered a larger supply of exchangeable cation nutrients than the B horizons. After 8 weeks of growth under optimal moisture conditions, the seedlings were further grown for 14 d under drought conditions. Root‐growth dynamics were observed in rhizoboxes containing soils from the Ah and B horizons. The concentrations of Al3+, base cations, and nitrate in the soil solution and element concentrations in the root tissue were compared with above‐ and belowground growth parameters and root physiological parameters. There was no strong evidence that seedling roots suffered from high soil‐solution Al3+ concentrations. Within the tested range of BS (1.2%–6.5%) our results indicated that root physiological parameters such as O2 consumption decreased and callose concentration increased in soils with a BS < 3%. In contrast to the B horizons, seedlings in the Ah horizons had higher relative shoot‐growth rates, specific root lengths, and lengths and branching increments, but a lower root‐to‐shoot ratio and root‐branching frequency. In conclusion, these differences in growth patterns were most likely due to differences in nutrient availability and to the drought application and not attributable to differences in Al3+ concentrations in the soil solution.

A starting guide to root ecology: strengthening ecological concepts and standardising root classification, sampling, processing and trait measurements

“…To measure the root elements, the dissolved samples are determined using inductively coupled plasma–optical emission spectrometry (ICP–OES). This technique has multielement and high‐throughput options (Al, B, Ba, Ca, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, P, Pb, S, Zn are in a good range; Cd, Co, Mo are usually below the detection limits) (A. K. Richter et al ., 2011 ). As the measurement of P requires ample amount of dried root material, this may not be realistically measured on separate root orders.…”

Aluminum exclusion and aluminum tolerance in woody plants

“…Al concentrations in the fine roots of common temperate and boreal woody species usually exceed the limit for being hyperaccumulators (>1 mg g - 1 ). For example fine roots of Abies alba , Castanea sativa , Fagus sylvatica , Picea abies , Pinus cembra , and Pinus montana all have values of 1–10 mg g - 1 DW (Zysset et al, 1996; Brunner et al, 2002; Genenger et al, 2003; Hirano et al, 2006; Richter et al, 2011; see also Table 3 ). All these woody species are ectomycorrhizal, suggesting that ectomycorrhizal structures, such as fungal mantle and Hartig net, further contribute to the accumulation of Al in roots by immobilizing Al in the cell wall of the fungal hyphae (Brunner and Frey, 2000; Heim et al, 2003) or in the fungal vacuoles (Martin et al, 1994).…”

Drought and aluminium as stress factors in Norway spruce (Picea abies) seedlings

“…In comparison with the control, higher Al contents in soil did not influence the Al accumulation in needles significantly, probably because Al is predominantly accumulated in roots, while its effect on shoots is only secondary (Chaffai, Marzouk 2009). Richter et al (2011) observed that the differences in the physiological status of beech roots were connected rather with nutrient availability and drought application than with differences in Al 3+ concentrations in the soil solution.…”

“…The presence of Al leads to decreasing concentrations of K, Ca and Mg and a decrease of the base cations to Al molar ratio in the soil solution (De Witt et al 2010). The Ca:Al ratio in roots and soils has been used as a useful indicator of the health status in plants and a diagnostic tool for the prediction of potential stress in forest ecosystems (Konôpka, Lukáč 2010;Richter et al 2011).…”