PARENT SESSION
Poster Session #1: Decomposition and Soil Respiration.
Monday, August 5. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC

Altered rainfall patterns affect soil respiration, nitrogen availability, and decomposition in a tallgrass prairie ecosystem.

Harper, Christopher^*,1, Blair, John¹, Fay, Philip¹, Knapp, Alan¹, Carlisle, Jonathan¹, ¹ Kansas State University, Manhattan, KS

ABSTRACT- Large-scale intensification of the global hydrological cycle associated with global warming is predicted to result in changes in rainfall patterns for many regions of the world. For the US Central Plains, precipitation events are expected to become less frequent but more severe (i.e., a shift toward more intense storms). We explored the effects of increased variability of rainfall events on belowground processes in a sub-humid grassland. Using fixed position rainfall exclusion shelters, we manipulated both timing and amounts of growing season rainfall on an annually burned lowland tallgrass prairie (Konza Prairie, Kansas, USA) since 1998. Altered rainfall timing and reduced amounts depressed growing season mean rate of soil respiration by as much as 18%. Altered rainfall patterns also affected soil nitrogen (N) availability as indicated by field incubation of ion-exchange resin bags; plots receiving reduced frequency of rainfall events had increased soil N availability compared to plots receiving natural frequency of rainfall events. Additionally, we found that reductions in rainfall amount reduced rates of grass root decomposition in buried litterbags. We suggest that changes in future rainfall patterns will affect the carbon balance and nutrient status of sub-humid grasslands. Furthermore, interactions associated with altered soil moisture regimes under a changing climate may be important in regulating global warming – soil respiration feedbacks.

KEY WORDS: tallgrass prairie, altered precipitation patterns, soil CO₂ flux, climate change