PARENT SESSION
Oral Session # 93: Vegetation Change and Response.
Presiding: B Parry Hecht
Friday, August 8. 8:30 AM to 12:00 PM, SITCC Meeting Room 105.
Phenological response of tallgrass prairie to experimental warming and clipping.
Wallace, Linda*,1, Sherry, Rebecca1, Luo, Yiqi1, Zehrbach, Nancy1, Wan, Shiqiang2, 1 University of Oklahoma, Norman, OK2 Oak Ridge National Laboratory, Oak Ridge, TN
ABSTRACT- We have warmed 6 plots of tallgrass prairie 2o C above ambient since 1999 in a fully crossed design with both annual clipping (hay mowing mimic) and warming. Although we have not yet seen substantial community structure changes, the phenology of plant species has been altered, particularly in the fall. This site has heavy clay soils and a depauperate winter annual flora. Hence, few early spring differences in phenology have been noted between warmed and unwarmed plots, despite soil temperatures above 10o C occurring from 6 to 22 days earlier in the warmed plots. Perhaps the species present in these plots are more sensitive to daylength than soil temperature. However, in the fall we have found that green tissues are present for longer periods on Schizachyrium scoparium and Sorghastrum nutans, both C4 species. Ambrosia psilostachyia , a C3 forb, also maintains green tissues and flowering structures longer in the warmed plots for time periods up to 14 days. Soil temperatures above 10o C have been maintained in the warmed plots from 1 to 11 days longer than in the unheated plots. In a site with a more diverse winter annual flora, we would expect larger phenological differences to occur in the early spring, as well. We have not yet seen phenological changes that would suggest uncoupling of plant/pollinator systems.
Key words: Oklahoma, global warming, tallgrass prairie, phenology