Short Term Effects of Ozone on the Plant-Rhizosphere-Bulk Soil System of Young Beech Trees

Abstract

Plant growth largely depends on microbial community structure and function in the rhizosphere. In turn, microbial communities in the rhizosphere rely on carbohydrates provided by the host plant. This paper presents the first study on ozone effects in the plant-rhizosphere-bulk soil system of 4-year-old beech trees using outdoor lysimeters as a research platform. The lysimeters were filled with homogenized soil from the corresponding horizons of a forest site, thus minimizing field heterogeneity. Four lysimeters were treated with ambient ozone (1 x O3) and four with double ambient ozone concentrations (2 x O3; restricted to 150 ppb). In contrast to senescence, which was almost unaffected by ozone treatment, both the photochemical quantum yield of photosystem II (PSII) and leaf gas exchange were reduced (11 - 45 %) under the elevated O3 regime. However, due to large variation between the plants, no statistically significant O3 effect was found. Even though the amount of primary metabolites, such as sugar and starch, was not influenced by elevated O3 concentrations, the reduced photosynthetic performance was reflected in leaf biochemistry in the form of a reduction in soluble phenolic metabolites. The rhizosphere microbial community also responded to the O3 treatment. Both community structure and function were affected, with a tendency towards a lower diversity and a significant reduction in the potential nutrient turnover. In contrast, litter degradation was unaffected by the fumigation, indicating that in situ microbial functionality of the bulk soil did not change.

Effects of ozone and Phytophthora citricola on non-structural carbohydrates of European beech (Fagus sylvatica) saplings

“…At the Helmholtz Zentrum München a lysimeter experiment was conducted since 2003 to study the impact of chronic ozone exposure on European beech saplings (Pritsch et al 2008;Schloter et al 2005). In addition, inoculation with the root pathogen P. citricola was performed in 2006 to investigate possible interactions between ozone and the plant disease.…”

Ectomycorrhizal Communities on the Roots of Two Beech (Fagus sylvatica) Populations from Contrasting Climates Differ in Nitrogen Acquisition in a Common Environment

“…The same holds true for the mycorrhizal mantle (13,14). Besides other functions, these prokaryotes are able to catalyze the mineralization of organic matter.…”

Plant-Mediated Ecosystem Effects of Tropospheric Ozone

“…For example in an OTC study with birch (Betula pendula) clones O 3 slightly increased the content of leaf low molecular weight phenolic compounds, an effect which did not persist over the 3-year study. On the other hand, litter chemistry was not affected by short-term O 3 exposure in a study with beech Fagus sylvatica (Schloter et al 2005). In free air type O 3 exposure experiments, it has been demonstrated that O 3 -induced changes in litter quality of Populus tremuloides and Betula papyrifera communities led to reduced inputs of hemicellulose and lignin (Liu et al 2005;Meehan et al 2010) and thus caused a decrease in nutrient flux into soil (Liu et al 2007).…”

“…In a multi-year mesocosm study with Pinus ponderosa, elevated O 3 tended to increase the ratio of fungal to bacterial biomass (Olszyk et al 2001) and such an effect was also observed under similar O 3 exposure conditions for blue wildrye (Elymus glaucus, Yoshida et al 2001). For the tree species Fagus sylvatica, a shift in the overall community structure of soil microorganisms based on phospholipid fatty acids (PLFA) analysis as a biomarker in response to O 3 ) has been found to be associated with a reduction in the potential nutrient turnover (Schloter et al 2005) and a higher abundance of plant-carbon utilising microbes (Esperschutz et al 2009). Aneja et al (2007) characterised the diversity of microbial communities colonising control and O 3 -exposed litter from Fagus sylvatica/Picea abies and provided evidence that changed litter quality due to elevated O 3 influenced the structure of litter-colonising microbial communities.…”