Competition alters plant species response to nickel and zinc

Phytoextraction can be a cost-efficient method for the remediation of contaminated soils. Using species mixtures instead of monocultures might improve this procedure. In a species mixture, an effect of heavy metals on the species' performance can be modified by the presence of a co-occuring species. We hypothesised that (a) a co-occuring species can change the effect of heavy metals on a target species, and (b) heavy metal application may modifiy the competitive behaviour between the plants. We investigated these mechanisms in a greenhouse experiment using three species to serve as a model system (Carex flava, Centaurea angustifolia and Salix caprea). The species were established in pots of monocultures and mixtures, which were exposed to increasing concentrations of Ni and Zn, ranging from 0 to 2,500mg/kg. Increased heavy metal application reduced the species' relative growth rate (RGR); the RGR reduction being generally correlated with Ni and Zn concentrations in plant tissue. S. caprea was an exception in that it showed considerable Zn uptake but only moderate growth reduction. In two out of six cases, competitors significantly modified the influence of heavy metals on a target species. The interaction can be explained by an increased uptake of Zn by one species (in this case S. caprea) that reduced the negative heavy metal effect on a target species (C. flava). In two further cases, increasing heavy metal application also altered competitive effects between the species. The mechanisms demonstrated in this experiment could be of relevance for the phytoextraction of heavy metals. The total uptake of metals might be maximised in specific mixtures, making phytoextraction more efficien

Plant species from mesotrophic wetlands cause relatively high methane emissions from peat soil

Plants can influence methane emissions from wetland ecosystems by altering its production, consumption and transport in the soil. The aim of this study was to investigate how eight vascular plant species from mesotrophic to eutrophic wetlands vary in their influence on CH4 emissions from peat cores, under low and high N supply. Additionally, we measured the production of low-molecular-weight organic acids (LOA) by the same species (also at low and high N supply), because LOA form a substrate for methanogenesis. There were considerable differences among species in their effects upon rates of CH4 emission. Six of the species (Eriophorum latifolium Hoppe, Potentilla palustris (L.) Scop., Anthoxanthum odoratum (L.) s. str., Carex rostrata Stokes, Carex elata All., Carex acutiformis Ehrh.) increased CH4 emissions up to five times compared to control peat cores without plants, whereas two species (Phalaris arundinacea L., Phragmites australis (Cav.) Trin. ex Steud.) had no effect. There was a weak negative correlation between plant biomass and CH4 emission. N addition had no significant general effect upon CH4 emission. LOA production varied considerably among species, and tended to be highest for species from mesotrophic habitats. LOA production was stimulated by N addition. We conclude that some species from mesotrophic wetlands tend to cause higher CH4 emissions than species from eutrophic wetlands. This pattern, which contradicts what is often mentioned in literature, may be explained by the higher LOA production rates of species adapted to less productive habitat

Plant species from mesotrophic wetlands cause relatively high methane emissions from peat soil

ISSN:0032-079XISSN:1573-503

Towards a trait-based ecology of wetland vegetation

1. Functional traits mechanistically capture plant responses to environmental gradients as well asplant effects on ecosystem functioning. Yet most trait-based theory stems from terrestrial systemsand extension to other habitats can provide new insights.2. Wetlands differ from terrestrial systems in conditions (e.g. soil water saturation, anoxia, pHextremes), plant adaptations (e.g. aerenchyma, clonality, ubiquity of bryophytes) and important pro-cesses (e.g. denitrificati on, peat accumulation, methane emission). Wetland plant adaptations andtrait (co-)variation can be situated along major plant trait trade-off axes (e.g. the resource economicsspectrum), but soil saturation represents a complex stress gradient beyond a simple extension ofcommonly studied water availability gradi ents.3. Traits that affect ecosystem functioning overlap with patterns in terrestrial systems . But wetland-specific traits that mediate plant effects on soil redox conditions, microbial communities and onwater flow, as well as trait spectra of mosses, vary among wetland types.4. Synthesis. With increasing availability of quantitative plant traits a trait-based ecology of wetlandsis emerging, with the potential to advance process-based understanding and prediction. We providean inte ractive cause-and-effect framework that may guide research efforts to disentangle the multipleinteracti ng processes involved in scaling from environmental conditions to ecosystem functioni ngvia plant communities.</p