Submission Type
Oral Presentation
Abstract
Frequent droughts are predicted to impact grasslands but intraspecific variation in response to drought is not well-known. Big bluestem (Andropogon gerardii) is a grass distributed across the Midwest rainfall gradient (MAP500-1200mm/yr) giving rise to climate-adapted ecotypes. This dominant grass is important for cattle forage and conservation. Reciprocal gardens were established in 2009 in ecological communities (driest to wettest: Colby, Hays, Manhattan, KS to Carbondale IL) and measured for over a decade. Rainfall was reduced using rainout shelters in three sites. Cover and biomass were monitored in plots over time, and height, width, photosynthetic rate, SPAD, and reproductive phenology were measured on single plants. Objectives were to 1) characterize functional traits across the natural gradient, 2) measure trait response to drought and 3) determine the impact of ecotypes on the community. We hypothesized drought tolerant traits would be more prevalent in the dry ecotype, drought would delay reproduction, and that the local ecotype would be competitively dominant over the surrounding community. The dry ecotype showed higher photosynthetic rates and SPAD, narrower blade width, and reduced height than the wet ecotype. Drought delayed reproduction and decreased biomass and cover. Wet and dry ecotypes had highest performance in their home site, demonstrating local adaptation. The dry ecotype in the wet site had higher performance under the rainouts, demonstrating adaption to reduced rainfall. The locally adapted ecotype became competitive dominance over the surrounding plant community. These results indicate the prominent role of ecotypes and that restoration should use climate-adapted ecotypes in anticipation of droughts.
Decadal Patterns of Adaptation and Trait Variation of the Dominant Prairie Grass Across the Midwest Rainfall Gradient and Response to Drought
Frequent droughts are predicted to impact grasslands but intraspecific variation in response to drought is not well-known. Big bluestem (Andropogon gerardii) is a grass distributed across the Midwest rainfall gradient (MAP500-1200mm/yr) giving rise to climate-adapted ecotypes. This dominant grass is important for cattle forage and conservation. Reciprocal gardens were established in 2009 in ecological communities (driest to wettest: Colby, Hays, Manhattan, KS to Carbondale IL) and measured for over a decade. Rainfall was reduced using rainout shelters in three sites. Cover and biomass were monitored in plots over time, and height, width, photosynthetic rate, SPAD, and reproductive phenology were measured on single plants. Objectives were to 1) characterize functional traits across the natural gradient, 2) measure trait response to drought and 3) determine the impact of ecotypes on the community. We hypothesized drought tolerant traits would be more prevalent in the dry ecotype, drought would delay reproduction, and that the local ecotype would be competitively dominant over the surrounding community. The dry ecotype showed higher photosynthetic rates and SPAD, narrower blade width, and reduced height than the wet ecotype. Drought delayed reproduction and decreased biomass and cover. Wet and dry ecotypes had highest performance in their home site, demonstrating local adaptation. The dry ecotype in the wet site had higher performance under the rainouts, demonstrating adaption to reduced rainfall. The locally adapted ecotype became competitive dominance over the surrounding plant community. These results indicate the prominent role of ecotypes and that restoration should use climate-adapted ecotypes in anticipation of droughts.
Comments
Jack Sytsma,1 Matthew Galliart,2 Trevor Heffley5, Sara G. Baer,3 Nora Bishop1, Helen Winters1, Eli Hartung,1 David Gibson,4 Loretta Johnson1
1Department of Biology, Kansas State University; 2Department of Biological Sciences, Fort Hays State University; 3Ecology and Evolutionary Biology, University of Kansas; 4School of Biological Sciences, Southern Illinois University Carbondale, 5Statistics, Kansas State University