Gorchov, David L. , Whigham, Dennis , ONeill, Jay .
The role of disturbance in plant invasion: an experimental test of whether Rubus phoenicolasius will survive canopy closure.
INVASIBILITY of many plant communities is associated with disturbance. For localized disturbances, it is rarely known whether 1) invasion is limited to new disturbances or 2) disturbance opens the entire community to invasion. We tested these hypotheses using wineberry, Rubus phoenicolasius, an Asian species that is invasive in deciduous forest in eastern USA. In mature forest at our Maryland study site, this species is currently found at edges and in large tree-fall gaps; vegetative reproduction, fruit production, and seedling establishment are all associated with higher light environments. We tested whether 1- and 2-year-old genets survive the low light levels expected with canopy closure. Potted individuals were overwintered, then grown April – Oct. 2005 under 5%, 12%, and 20% full sun, in an outdoor garden. These treatments (“low”, “medium,” and “high light”) approximated closed canopy, small gaps, and large gaps, respectively. For all treatments, survival of 1-year-old individuals was high, and relative growth rate (RGR) based on leaf number, was positive. RGR differed among treatments (F=9.36, df=2 for all ANOVAs) and was correlated with light. Similarly, all 2-year-old individuals survived, and RGR (based on cane length) was positive in all treatments. RGR (F=5.52) and primocane leaf area (F=7.10) differed among treatments, with medium light plants having the highest values and low light plants the lowest. Root biomass (F=5.69) and primocane shoot biomass (F=7.18) differed among treatments, and were greatest in high light and lowest in low light. High light plants had lower specific leaf area than the two other treatments (F=4.99). These findings indicate that R. phoenicolasius individuals recruited in gaps will survive canopy closure, thus disturbance opens the entire stand to invasion. However, mature stands can be protected from invasion if new disturbances are patrolled, and new R. phoenicolasius removed, every 3-4 years.
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1 - Miami University, Department of Botany, Oxford, Ohio, 45056, USA
2 - Smithsonian Enviromental Resource Center, Po Box 28, 647 Contees Wharf Rd, Edgewater, Maryland, 21037, USA
relative growth rate
Presentation Type: Oral Paper:Papers for Sections
Date: Monday, July 31st, 2006
Time: 3:30 PM