Aggregated seed arrival alters plant diversity in grassland communities

dc.contributor.authorHouseman, Gregory R.
dc.descriptionClick on the DOI link to access the article (may not be free).en_US
dc.description.abstractAims Species aggregation is commonly seen in plant communities and may increase diversity by causing intraspecific competition to exceed interspecific competition. One potential source of this spatial aggregation is seed dispersal but it is unclear to what extent aggregated seed distributions affect plant diversity in real communities. Using a field experiment, I tested whether uniform or aggregated seed arrival alters community structure and whether these effects vary with sowing density. Methods The experiment consisted of two spatial seeding treatments (uniform and aggregated) that were fully crossed with three seed density treatments. Sixty, 3 × 4-m plots were arrayed in a low-diversity grassland located in Kansas, USA. Each plot was divided into forty-eight, 0.5 × 0.5-m patches. For aggregated seeding treatments, each of the 15 species was sown into three randomly selected patches within the plot (3×15 = 45). To create a uniform species arrival but control for the seed addition method, all 15 species were sown into 45 individual patches (with three patches remaining unsown) within each plot. Seed mass for each species was held constant at the plot scale between uniform or aggregated treatments within a given level of the sowing density treatment. After two growing seasons, plant density was quantified for all sown species in 15 randomly selected patches from each plot. Important Findings I found evidence for shifts in community structure in response to the different spatial seeding patterns. The evenness of added species was higher under aggregated than uniform sowing patterns. There was no detectable effect of aggregated seed sowing on species richness at 3.75 m2 scale. However, when species richness was extrapolated to larger scales (11.25 m2), aggregated sowing was predicted to have greater richness than uniform sowing. Effects of seed aggregation on community structure were apparent only at moderate to high sowing rates, yet the latter are within the range of measured seed dispersal in similar grasslands. Additionally, as sowing density increased, seed mass became an increasingly effective predictor of relative abundances for added species, but only under uniform sowing patterns supporting the idea that aggregated dispersal may buffer weaker (smaller seeded) species from competition during colonization. This is the first experiment to show that aggregated seed dispersal patterns can increase at least some components of plant diversity in undisturbed grasslands and suggests that previous seed dispersal experiments, which utilize uniform seed sowing, may underestimate the potential effect of dispersal on plant community structure.en_US
dc.description.sponsorshipWichita State University; National Science Foundation (EPS 0903806).en_US
dc.identifier.citationHouseman, Gregory R. 2014. Aggregated seed arrival alters plant diversity in grassland communities. Journal of Plant Ecology, vol. 7:no. 1:ppg. 51-58en_US
dc.publisherOxford University Pressen_US
dc.relation.ispartofseriesJournal of Plant Ecology;v.7:no.1
dc.rights.holder© The Author 2013. Published by Oxford University Press on behalf of the Institute of Botany, Chinese Academy of Sciences and the Botanical Society of China. All rights reserved. For permissions, please email:
dc.subjectRank-abundance distributionsen_US
dc.subjectSeed dispersalen_US
dc.subjectSeed sowingen_US
dc.titleAggregated seed arrival alters plant diversity in grassland communitiesen_US
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