PARENT SESSION
Oral Session #54: Vegetation: Controls on NPP, Global Climate Change. Presiding: W. Oechel.
Wednesday, August 8, 2001. 1:00 PM to 5:00 PM. Hall of Ideas G.
Rainfall manipulations mirror topography effects on productivity and water relations in tallgrass prairie.
Fay, Philip1, Knapp, Alan1, Blair, John 1, Collins, Scott2, Carlisle, Jonathan1, 1 2
ABSTRACT- Climatic variability is a key driver of ecosystem structure and function in tallgrass prairie. Future rainfall patterns are predicted by most global climate models to lead to increasingly variable moisture availability as the climate changes. Rainfall variability has been experimentally increased (by 50%) beginning in 1998 in the Rainfall Manipulation Plot experiment at the Konza Prairie Biological Station in northeastern Kansas tallgrass prairie. After three growing seasons of manipulations in annually burned prairie, alterations in rainfall variability (defined as duration between events) with total inputs held constant led to reductions in aboveground net primary production (ANPP), water use efficiency (WUE), and soil CO2 fluxes compared to rainfall applied in ambient patterns. These responses mirrored long-term (20 yr) changes in productivity and water relations associated with alterations in topographic position and soil depth across the tallgrass prairie landscape. Thus, reductions in ANPP (33%), WUE (35%), and soil CO2 fluxes (8%), and increases in forb abundance (50%) in shallow-soiled uplands versus deep-soiled lowland sites were similar in direction and magnitude to responses to increased rainfall variability. As a result of this functional correspondence, upland sites in this grassland may serve as surrogates for estimating the magnitude of change to be expected in tallgrass prairie structure and function under future rainfall scenarios.
KEY WORDS: grassland, climate change, precipitation, productivity