Plant–plant interactions and soil moisture might be important in determining ozone impacts on grasslands

• Published in: The New phytologist 2000-08, Vol.147 (2), p.327-335
• Main Authors: NUSSBAUM, S., BUNGENER, P., GEISSMANN, M., FUHRER, J.
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Applied ecology; binary mixtures; Biological and medical sciences; Biomass; Centaurea jacea; Demecology; Fundamental and applied biological sciences. Psychology; Grassland soils; grassland species; Mixing ratios; Natural grasslands; Non agrochemicals pollutants; open‐top chambers; Ozone; Phytopathology. Animal pests. Plant and forest protection; Plant competition; Plants; Plants and fungi; Pollution effects and side effects of agrochemicals on crop plants and forest trees. Other anthropogenic factors; Pollution effects. Side effects of agrochemicals; replacement series; Research article; Soil water; soil water content; Species; Trifolium pratense; Trisetum flavescens
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1046/j.1469-8137.2000.00697.x

Ozone effects on plant species mixtures could depend on the characteristics of the species involved, their mixing ratio, or on environmental conditions. Predicting long-term effects on the dynamics of plant communities requires an understanding of the interactions involved. The present experiment was designed to determine the effects of ozone on grassland species in relation to mixing ratio and soil water content (irrigation) using binary mixtures. The grass Trisetum flavescens was grown in potted replacement-series mixtures with Centaurea jacea (Experiment A) or Trifolium pratense (Experiment B). The plants were exposed to three concentrations of ozone in open-top chambers in two irrigation treatments. Total above-ground dry weight over three growth periods was measured. The competitive ability of T. flavescens was expressed as the competitive ratio (CRT). In Experiment B, total above-ground dry weight was reduced by elevated ozone and by reduced soil moisture, and significant interactions were found for ozone × irrigation and ozone × ratio. In Experiment A these effects were not significant. Under well watered conditions, CRT tended to be reduced by elevated ozone in Experiment A, but increased significantly in Experiment B, indicating the importance of the competing species in modifying the ozone effect on T. flavescens. In both experiments reduced irrigation decreased the magnitude of ozone effects on biomass production, which could be related to observed reductions in specific leaf conductance. The results suggest that under well watered conditions the effect of elevated ozone on the competitive balance between species depends on the species mixture, but that the mixing ratio is less important.