Bioscience Horizons Advance Access originally published online on April 24, 2008
Bioscience Horizons 2008 1(2):128-135; doi:10.1093/biohorizons/hzn017
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Species richness and aggregation effects on the productivity of ruderal plant communities under drought perturbation
School of Agriculture, Policy and Development, University of Reading, Earley Gate, Reading, PO Box 237, RG6 6AR, UK
* Corresponding author. Oxford University Centre for the Environment, South Parks Road, Oxford, OX1 3PG, UK. Tel: 01865 283933 Email: nodoka.nakamura{at}ouce.ox.ac.uk
Supervisor: Dr Andrew Wilby, School of Agriculture, Policy and Development, University of Reading, Reading, UK. Present address: Department of Biological Sciences, Lancaster University, Lancaster, UK.
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Abstract |
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The effect of species richness and spatial aggregation on the stability of community productivity in response to drought perturbation was investigated with experimental plant communities. Communities comprising all single- and three-species combinations of the ruderal species, Capsella bursa-pastoris, Tripleurospermum inodorum, Poa annua, and Stellaria media, were established in glasshouse. Habitat patchiness was manipulated by applying different seed-sowing patterns, either aggregated or random. After the establishment of communities, 8 days of drought treatment was imposed. Followed by a week of recovery with a regular watering regime, aboveground biomass was harvested. Community biomass was not affected by species richness or by aggregation, but was affected by perturbation. When multi-species community productivity was compared with monocultures in relative terms, species mixtures performed better in drought-induced conditions. This suggests that the positive effect of species richness may be enhanced under the perturbed condition. Sampling effects were evident under perturbation favouring the least productive species, P. annua and drought-tolerant S. media. All species except C. bursa-pastoris showed reduced productivity in species mixtures, but this may be mitigated under perturbed environments by species complementarity. Lack of clear responses to aggregation may suggest that the revealed diversity effect is not related to spatial structure. While competition predominates in communities in the resource-rich environment, drought perturbation enhance overall community productivity via a shift in relative significance of species interactions from competition to sampling and complementarity effects.
Key words: biodiversity effects, ecosystem stability, drought perturbation, relative yield total
Submitted on 3 October 2007; accepted on 21 December 2007