|Shields Jr, Fletcher|
Submitted to: Acta Oecologica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/5/2005
Publication Date: 10/1/2005
Citation: Li, S., Martin, L.T., Pezeshki, S.R., Shields Jr, F.D. 2005. Responses of black willow (salix nigra) cuttings to herbivory and flooding. Acta Oecologica. 28(2): 173-180.
Interpretive Summary: Stream channel erosion results in degraded water quality, loss of land, and ecological damage. Willow trees, which root from cuttings, are effective and economical plants for re-establishing woody vegetation for stabilization of eroding stream channels. However, survival and success of willow planting projects is often lowered by environmental factors such as flooding, poor soils, and grazing by beaver. This greenhouse experiment investigated the effects of flooding and beaver grazing on the growth of willow cuttings. Beaver grazing was simulated by clipping the tops of well-established cuttings. Clipped cuttings exhibited faster height growth than unclipped cuttings, but they were unable to fully replace the biomass removed by simulated beaver grazing. Evidently willow cuttings can survive at least a single severe grazing event even when subjected to flooding stress. These findings may be used to enhance the efficiency of stream bank and riparian zone restoration projects, since beaver control efforts may be abbreviated.
Technical Abstract: Herbivory and flooding influence plant species composition and diversity in many wetland ecosystems. Black willow (Salix nigra) naturally occurs in floodplains and riparian zones of the southeastern United States. Cuttings from this species are used as a bioengineering tool for streambank stabilization and habitat rehabilitation. The present study was conducted to evaluate the photosynthetic and growth responses of black willow to simulated herbivory and flooding. Potted cuttings were subjected to three levels of single-event herbivory: no herbivory (control), light herbivory, and heavy herbivory; and three levels of flooding conditions: no flooding (control), continuous flooding, and periodic flooding. Results indicated that elevated stomatal conductance contributed to the increased net photosynthesis noted under both levels of herbivory. However, chlorophyll content was not responsible for the observed compensatory photosynthesis. Cuttings subjected to heavy herbivory accumulated the lowest biomass even though they had the highest height growth by the conclusion of the experiment. In addition, a reduction in root/shoot ratio was noted for plants subjected to continuous flooding with no herbivory. However, continuously flooded, lightly clipped plants allocated more resources to roots than shoots. This study provides evidence that black willow can survive a severe herbivory event and flooding at restoration sites where the two factors are likely to be present.