PARENT SESSION
Oral Session #69: Elevated CO2 and Global Change. Presiding: L. Gough.
Thursday, August 9, 2001. 1:00 PM to 4:45 PM. Hall of Ideas H.
Grassland community response to warming and clipping.
Wallace, Linda1, Luo, Yiqi1, Wan, Shiqian1, Bowdish, Sarah1, 1
ABSTRACT- Mixed grass prairie plots were warmed with quartz heaters to 1.5 C over ambient air temperatures for one year. The 2 x 2 m plots were arranged in a split plot design with control plots under a dummy lamp and all plots either clipped biannually or left unclipped. Clipping was at 10 cm to mimic mowing for hay, an important land use in the Central Great Plains. Plant community structure of each 1 x 1 m subplot was determined by visually estimating basal cover of all species. Community data were entered into CANOCO and PCA was run on species data alone. Canonical correspondence analysis was run on species and environmental data. Prior to the onset of treatments in November, 1999, no differences in community structure were found. By the following spring, significant differences were found between clipped and unclipped plots. During the summer, plot differences were minimized. However, by the fall, significant effects of warming and clipping were found with a significant interaction between the two treatments. C3 species cover increased in warmed plots in the fall. Bare ground increased in clipped plots with a slight increase in C4 cover in the summer. Environmental factors most closely correlated with community structure changes will be discussed.
KEY WORDS: Grasslands, Global change, Mowing, Community structure