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Title: Interactive effects of elevated CO2, warming, and moisture on timings and rates of plant development in a mixed-grass prairie ecosystem: Enhancing the GPFarm model

Author
item Reyes-Fox, Melissa
item TRLICA, JOSEPH - COLORADO STATE UNIVERSITY
item ANDALES, ALLAN - COLORADO STATE UNIVERSITY
item McMaster, Gregory
item Morgan, Jack
item KNAPP, ALAN - COLORADO STATE UNIVERSITY

Submitted to: Ecological Society of America Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 3/2/2008
Publication Date: 8/7/2008
Citation: Reyes Fox, M.A., Trlica, J.M., Andales, A.A., Mcmaster, G.S., Morgan, J.A., Knapp, A.K. 2008. Interactive effects of elevated CO2, warming, and moisture on timings and rates of plant development in a mixed-grass prairie ecosystem: Enhancing the GPFarm model. In: Ecological Society of America annual meeting, August 2008, Milwaukee, WI. CDROM.

Interpretive Summary:

Technical Abstract: Global change will undoubtably affect the mechanisms that govern natural processes. This study investigates the effects of CO2 enrichment, warming and water additions on phenological growth stages of dominant prairie species in the west-central Great Plains. Observational data was collected on a weekly basis from mid-March through November to determine differences in the onset of certan developmental phases for Bouteloua gracilis (Bogr), Pascopyrum smithii (Pasm) and Stipa comata (Stco). Four key growth stages were identified: beginning of spring growth (BSG), start of anthesis (AS), seed maturation (SM), and end of season growth (ESG). We observed significant overall treatment effects for Bogr at AS (p=0.017) as well as for Stco at ESG (p=0.021). To determine the effects CO2 enrichment, warming and irrigation had on plant phenology, we ran a pairwise comparisons test to isolate treatment effects. We found a significant CO2 effect (p=0.047) for Stco at ESG, suggesting water savings resulting from reduced stomatal conductance permitted Stco to persist later into the growing season. Additionally, a heating effect was evident for both Bogr (p=0.032) and Stco (p=0.042) at AS, where AS was initiated earlier in the growing season. Lastly, a signficant irrigation effect was detected for Bogr at AS where those individuals treated wtih a shallow, more frequent irrigation regime set seed earlier in the season than those exposed to less frequent, deep irrigation treatments (p=0.028). These results indicate that seed production is largely mediated by warmer temperatures and water additions. It is likely that changes in temperature and CO2 concentrations will influence influence soil moisture and seedling recruitment, which may alter the structure of plant communities. Intraspecific seed production also varied according to interactive treatment effects where plants occuring in non-irrigated plots flowered less frequently than those that were exposed to either a deep or shallow irrigation regime. Shifts in species abundance may adversely affect organisms that depend on certain species for forage. An additional component of this research is to predict plant development as a function of CO2, temperature, and soil moisture. After the model is parameterized, new long-term simulations will evaluate the possible changes in plant development under different climate change scenarios. Data collected will enhance the GPFARM-Range model (Ascough et al. 2002), a decision support tool developed by the USDA-ARS to assist ranchers with managing site-specific areas to optimize production and economic benefits while minimizing environmental impacts.