PS 93-217
Using stable isotopes to quantify seed dispersal along habitat corridors

Friday, August 9, 2013
Exhibit Hall B, Minneapolis Convention Center
John D. Herrmann, Department of Landscape Ecology, University of Kiel, East Lansing, Germany
Lars A. Brudvig, Plant Biology, Michigan State University, East Lansing, MI
Tomás A. Carlo, Biology, The Pennsylvania State University, University Park, PA
Ellen I. Damschen, Zoology, University of Wisconsin-Madison, Madison, WI
Caitlin Forster, University of Washington
Nick M. Haddad, Department of Biology, North Carolina State University, Raleigh, NC
Douglas J. Levey, Population and Community Ecology Cluster, National Science Foundation, Washington, DC
John L. Orrock, Zoology, University of Wisconsin - Madison, Madison, WI
Joshua J. Tewksbury, Colorado Global Hub, Future Earth, Boulder, CO

Negative effects of habitat fragmentation have led to widespread use of habitat corridors in conservation. Yet not all species respond to corridors in the same way.  Predicting these differences is difficult due to lack of a robust, empirically validated framework that applies to the diverse taxa that characterize ecological communities.  In plants, dispersal ability is largely determined by morphology (e.g., pappus) and the mode of dispersal (e.g., animal-mediated or wind). Due to their small size and the rarity of long-distance dispersal, however, it is difficult to trace seeds from a given point across a landscape. In 12 experimental landscapes designed to test corridor effects on dispersal, we used a stable 15N -isotope to label six wind- and two bird-dispersed plant species. Four thousand seed traps were deployed in these landscapes to trace labeled, long-distance dispersing seeds. Here, we evaluate the efficacy of our spraying technique for labeling seeds. Seeds collected from sprayed plants were analyzed for 15N-enrichment and compared to 15N-levels of unsprayed plants. Application frequency and 15N-concentrations were varied for selected species to retrieve the most efficient enrichment scheme.


Our results showed that the application of 15N-labeld urea is sufficient to achieve significant enrichment of 15N in seeds of all sprayed plant species, compared to seeds of unsprayed plants. Further, we could not find a significant difference in 15N-enrichment between plants sprayed three times with a 0.5g/l 15N-concentration and plants sprayed six times with a 0.25g/l 15N-concentration. Our study provides evidence that 15N-labeling can be used to study patterns and processes of seed dispersal by marking entire plant communities in relatively small areas. To decrease work effort, a lower spray frequency with higher concentrations is preferred to a higher spray frequency with lower concentrations.