Fisher, James P , Smith, Stuart W , Phoenix, Gareth K , Press, Malcolm C. , Cameron, Duncan D .
Redistributing the wealth or short-circuiting the system? The impact of a parasitic plant on soil nutrient cycling and community structure.
Rhinanthus minor is a root-hemiparasite that induces dramatic shifts in host community structure, significantly altering competitive balances between co-occurring species through the suppression of dominant grasses which frees forbs (non-leguminous dicots) from competitive exclusion/suppression. These shifts are underpinned by successful resistance mechanisms expressed by the forbs but lacked by grasses. Parasitic plants can also have facilitative effects on co-occurring species through soil nutrient flushes underpinned by their nutrient-rich leaf litter. Whether these opposing impacts act to ameliorate the suppression of host growth or further benefit the resistant species is not known: Does Rhinanthus redistribute mineral-nutrients or simply short-circuit the nutrient cycle, returning stolen resources to infected hosts through litter?
In 2005 grassland mesocosms were established to begin probing these questions. Four treatments; (i)infection by Rhinanthus, (ii)treatment with Rhinanthus litter, (iii)infection by Rhinanthus plus litter treatment and (iv)control, were repeated at two levels of fertility and applied to 64 mesocosms. In October 2008 an above-ground harvest was undertaken and the biomass, tissue N and tissue P concentration was determined for each functional group in each mesocosm.
Rhinanthus litter benefits grass and legume productivity and also partially ameliorates the negative effect of parasite infection on host growth. Forb productivity is suppressed by parasite litter when Rhinanthus is absent from the community however, this effect is negated in the presence of the parasite. The community level effects of Rhinanthus are thus a function of both the direct impact of parasitism on susceptible hosts and the indirect effects of the parasite on soil nutrient cycling. The indirect effects of the parasite in terms of nutrient uptake by different host functional groups and the pathways through which these re-mobilised nutrients are cycled will be discussed.
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1 - University of Sheffield, Department of Animal & Plant Sciences, Western Bank, Sheffield, South Yorkshire, S10 2TN, UK
2 - University of Birmingham, College of Life and Environmental Sciences, Birmingham, B15 2TT, UK
3 - University of Sheffield, Department of Animal and Plant Sciences, Alfred Denny Building, Western Bank, Sheffield, South Yorkshire, S10 2TN, UK
Presentation Type: Poster:Posters for BSA Sections
Location: Event Tent/Cliff Lodge
Date: Monday, July 27th, 2009
Time: 5:30 PM