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Direct and indirect impacts of hemiparasitic plants on species richness and community structure in managed grasslands in Flanders

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Abstract
Hemiparasitic plants are considered keystone species in grasslands and both directly and indirectly affect their host plant community. Hemiparasitic infection directly reduces host and total aboveground biomass production. Furthermore, when a host preference exists for dominant graminoids, hemiparasitic infection can alter the competitive balance in favour of forbs. This could in turn increase species richness and accelerate the restoration of species-rich grasslands. On the other hand, as many hemiparasites shed their nutrient-rich litter before hay-making, less nutrients are removed from the field. This could indirectly reduce species richness when higher nutrient availability favours competitive species. We hypothesised that (1) direct, structural effects will dominate in more nutrient-rich grasslands and (2) that indirect, biogeochemical effects will dominate in more nutrient-poor grasslands. Two types of managed wet grasslands with contrasting nutrient status were chosen: (1) mesotrophic Calthion palustris, infected by Rhinanthus angustifolius, and (2) rather oligotrophic, wet Nardo-Galion infected by Pedicularis sylvatica. For the mesotrophic Rhinanthus grasslands, we expect that direct effects on vegetation structure will dominate and that hemiparasitic infection will increase plant species diversity. In contrast, for the more nutrient-poor Pedicularis heath-grasslands, we expect that indirect effects on vegetation structure through changes in nutrient cycling will dominate, and that hemiparasitic infection could decrease plant species diversity. In the next four years, structural (1) and biogeochemical (2a-e) impacts of R. angustifolius and P. sylvatica on grassland communities will be studied. (1) In an experimental study, changes in vegetation structure (biomass, species richness) will be monitored in a randomized block design with four treatments: (i) parasitized control, (ii) weeding of hemiparasite, (iii) sowing of target species, and (iv) weeding + sowing. (2a) In an observational study, differences in leaf litter nutrient concentration, nutrient resorption efficiency/proficiency between hemiparasites and potential hosts are assessed. By means of a litterbag experiment (2b), decomposition rates and changes in N, P and lignin content of leaf litter of hemiparasites and most important potential hosts are determined. (2c) In a 15-N labelling experiment, we will investigate the proportion of organic and inorganic nitrogen, released during hemiparasitic leaf litter mineralization and try to relate the outcome to species diversity (N-niche dimensionality). In the next experiment (2d), the ability of potential hosts to take up N, released from 15-N labelled hemiparasitic litter is studied. (2e) In a last experiment, N transfer from host to hemiparasite will be quantified, using the semi-hydroponics experimental set-up.

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Chicago
Demey, Andreas, Els Ameloot, Pascal Boeckx, Martin Hermy, and Kris Verheyen. 2009. “Direct and Indirect Impacts of Hemiparasitic Plants on Species Richness and Community Structure in Managed Grasslands in Flanders.” In BES Annual Symposium, Abstracts, 30–30. British Ecological Society (BES).
APA
Demey, Andreas, Ameloot, E., Boeckx, P., Hermy, M., & Verheyen, K. (2009). Direct and indirect impacts of hemiparasitic plants on species richness and community structure in managed grasslands in Flanders. BES Annual symposium, Abstracts (pp. 30–30). Presented at the BES Annual symposium 2009 : Facilitation in plant communities, British Ecological Society (BES).
Vancouver
1.
Demey A, Ameloot E, Boeckx P, Hermy M, Verheyen K. Direct and indirect impacts of hemiparasitic plants on species richness and community structure in managed grasslands in Flanders. BES Annual symposium, Abstracts. British Ecological Society (BES); 2009. p. 30–30.
MLA
Demey, Andreas, Els Ameloot, Pascal Boeckx, et al. “Direct and Indirect Impacts of Hemiparasitic Plants on Species Richness and Community Structure in Managed Grasslands in Flanders.” BES Annual Symposium, Abstracts. British Ecological Society (BES), 2009. 30–30. Print.
@inproceedings{851573,
  abstract     = {Hemiparasitic plants are considered keystone species in grasslands and both directly and indirectly affect their host plant community. Hemiparasitic infection directly reduces host and total aboveground biomass production. Furthermore, when a host preference exists for dominant graminoids, hemiparasitic infection can alter the competitive balance in favour of forbs. This could in turn increase species richness and accelerate the restoration of species-rich grasslands. On the other hand, as many hemiparasites shed their nutrient-rich litter before hay-making, less nutrients are removed from the field. This could indirectly reduce species richness when higher nutrient availability favours competitive species. We hypothesised that (1) direct, structural effects will dominate in more nutrient-rich grasslands and (2) that indirect, biogeochemical effects will dominate in more nutrient-poor grasslands.
Two types of managed wet grasslands with contrasting nutrient status were chosen: (1) mesotrophic Calthion palustris, infected by Rhinanthus angustifolius, and (2) rather oligotrophic, wet Nardo-Galion infected by Pedicularis sylvatica. For the mesotrophic Rhinanthus grasslands, we expect that direct effects on vegetation structure will dominate and that hemiparasitic infection will increase plant species diversity. In contrast, for the more nutrient-poor Pedicularis heath-grasslands, we expect that indirect effects on vegetation structure through changes in nutrient cycling will dominate, and that hemiparasitic infection could decrease plant species diversity. 
In the next four years, structural (1) and biogeochemical (2a-e) impacts of R. angustifolius and P. sylvatica on grassland communities will be studied. (1) In an experimental study, changes in vegetation structure (biomass, species richness) will be monitored in a randomized block design with four treatments: (i) parasitized control, (ii) weeding of hemiparasite, (iii) sowing of target species, and (iv) weeding + sowing. (2a) In an observational study, differences in leaf litter nutrient concentration, nutrient resorption efficiency/proficiency between hemiparasites and potential hosts are assessed. By means of a litterbag experiment (2b), decomposition rates and changes in N, P and lignin content of leaf litter of hemiparasites and most important potential hosts are determined. (2c) In a 15-N labelling experiment, we will investigate the proportion of organic and inorganic nitrogen, released during hemiparasitic leaf litter mineralization and try to relate the outcome to species diversity (N-niche dimensionality). In the next experiment (2d), the ability of potential hosts to take up N, released from 15-N labelled hemiparasitic litter is studied. (2e) In a last experiment, N transfer from host to hemiparasite will be quantified, using the semi-hydroponics experimental set-up.},
  author       = {Demey, Andreas and Ameloot, Els and Boeckx, Pascal and Hermy, Martin and Verheyen, Kris},
  booktitle    = {BES Annual symposium, Abstracts},
  language     = {eng},
  location     = {Aberdeen, Scotland, UK},
  pages        = {30--30},
  publisher    = {British Ecological Society (BES)},
  title        = {Direct and indirect impacts of hemiparasitic plants on species richness and community structure in managed grasslands in Flanders},
  year         = {2009},
}