Symbioses: Plant, Animal, and Microbe Interactions
Fisher, James P , Phoenix, Gareth K , Cameron, Duncan D .
Robbing the rich to feed the rich? The direct and indirect effects of a parasitic plant on nutrient cycling and community structure.
Rhinanthus minor is a root-hemiparasite known to induce dramatic shifts in the composition of grassland communities in which it occurs. By decreasing the proportion of grasses in a community, this parasite allows forb species (non-leguminous dicots) to proliferate under reduced competition. This shift is underpinned by the differential ability of the plant functional groups to resist parasitism; grasses exhibit a weak resistance response while forbs resist parasitism strongly. In addition to their direct effects, parasitic plants can also have indirect effects on their host communities by modifying the flux of nutrients through ecosystems. Specifically, R. minor can extract nutrients from its perennial hosts and return them to the soil via its nutrient rich litter. But do these liberated nutrients act to ameliorate the direct impact of parasitism on susceptible hosts or further benefit the resistant ones? Do all species or functional groups within a grassland community benefit equally from the R. minor induced nutrient flush? In 2005 we established a field experiment in Derbyshire, UK to address these questions. Four treatments; (i) infection by R. minor, (ii) treatment with R. minor litter, (iii) infection by R. minor plus litter treatment and (iv) control, were applied to 40 1.25x1.25m plots. In August 2009 a vegetation survey was undertaken and followed by an above-ground harvest. Biomass, tissue N and tissue P were determined for each functional group (grasses, fobs and legumes) within each plot. The vegetation survey revealed a clear impact of R. minor infection on community composition; with the first evidence that parasitic plant litter can have differential effects on discrete functional groups within natural plant communities in the field. Moreover, in grasses, the positive effects of litter inputs negated the negative effects of parasitims .
Therefore, to understand the role that parasitic plants play in modulating plant community structure we must consider both their direct parasitic effects and their indirect impacts on nutrient cycling.
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1 - University of Sheffield, Department of Animal & Plant Sciences, Western Bank, Sheffield, South Yorkshire, S10 2TN, UK
2 - University of Sheffield, Department of Animal and Plant Sciences, Alfred Denny Building, Western Bank, Sheffield, South Yorkshire, S10 2TN, UK
Presentation Type: Oral Paper:Papers for Topics
Location: 553B/Convention Center
Date: Monday, August 2nd, 2010
Time: 1:30 PM