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 × O3 ) and four with double ambient ozone concentrations (2 × 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.
Key words
Ozone - rhizosphere - plant - soil - microbial community - beech - litter degradation - lysimeter.
References
Apiognomonia errabunda dramatically depends on light exposure and climatic conditions.
Plant Biology.
(2005);
7
659-669
(Populus nigra) and beech (Fagus sylvatica) : a comparison.
Environmental Pollution.
(2000);
109
509-516
2 assimilation, transpiration and root growth of Fagus sylvatica infested with four different Phytophthora species.
Plant Biology.
(2002);
4
144-152
Neue Ergebnisse zum Mechanismus der Silberfärbung. Radola, B. J., ed. Electrophorese Forum' 86. Munich; Technische Universität München (1986): 22-27
2 and O3 concentrations differentially affect selected groups of the fauna in temperate forest soils.
Soil Biology and Biochemistry.
(2004);
36
1521-1524
2 and O3 on a ponderosa pine plant/litter/soil mesocosm.
Environmental Pollution.
(2001);
115
447-462
Phytophthora citricola in a phytotron experiment with spruce/beech mixed cultures.
Plant Biology.
(2005);
7
718-727
Interactions among root-inhabiting fungi and their implications for biological control of root pathogens. Sylvia, D., ed. Advances in Agronomy. New York; Academic Press (2001): 1-33
Hordeum vulgare L.) supplied with nitrogen fertilizer at two rates.
Plant and Soil.
(1993);
157
51-63
schloter@gsf.de
Editor: H. Rennenberg
