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ARS Home » Plains Area » Temple, Texas » Grassland Soil and Water Research Laboratory » Research » Publications at this Location » Publication #184848

Title: ECOLOGICAL RESPONSES TO PRECIPITATION QUANTITY AND FREQUENCY IN GRASSLANDS: PATTERN AND PROCESS FROM THE GENE TO THE ECOSYSTEM

Author
item Fay, Philip
item SMITH, M
item TRAVERS, S
item NIPPERT, J
item BLAIR, J
item GARRETT, K

Submitted to: Ecological Society of America Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 4/23/2005
Publication Date: 6/20/2005
Citation: Fay, P.A., Smith, M.D., Travers, S.E., Nippert, J.B., Blair, J.M., Garrett, K.A. 2005. Ecological responses to precipitation quantity and frequency in grasslands: pattern and process from the gene to the ecosystem. In: Ecological Society of America Proceedings, August 7-12, 2005, Montreal, Canada. 2005 CDROM.

Interpretive Summary:

Technical Abstract: Grasslands account for 40% of the U.S. land mass and are highly responsive to temperature and precipitation variability. Climate models and observations indicate warming and increased temporal variability in continental rainfall patterns resulting from increasing greenhouse gas concentrations. Growing season rainfall patterns have been manipulated in an eastern Kansas tallgrass prairie since 1998. A more variable rainfall pattern (extended dry intervals, fewer but larger rain events, no change in total rainfall quantity) lowered the mean and increased the variation in 0-30 cm soil water content. Total aboveground net primary productivity (ANPP) was reduced by 10% vs. the ambient rainfall pattern, due to decreased growth of subdominant warm season grasses, and no significant responses in other functional groups. Leaf-level photosynthetic carbon gain in two C4 grasses that account for > 60% of total biomass (Andropogon gerardii, Sorghastrum nutans) was strongly correlated with temporal variation in soil water content (R2 = 0.80), suggesting that these grasses contribute strongly to variation in ecosystem carbon and water fluxes. However Sorghastrum’s water use efficiency and photosynthetic nitrogen use efficiency decreased more strongly with decreasing soil water content than did Andropogon’s, suggesting that Sorghastrum should experience reduced success under a more variable soil moisture regime than Andropogon, a difference which was borne out in flowering stem density and cover. Preliminary analysis of Andropogon cDNA hybridized to maize microarrays suggested that thirteen genes involved in the regulation of photosystem I or II activity in Andropogon were differentially up regulated in the more variable rainfall treatment vs. the ambient rainfall treatment, suggesting that compensatory increases in photosynthetic function could in part explain Andropogon’s tolerance of increased rainfall variability. A comparative analysis of Andropogon and Sorghastrum gene activity is in progress. These results suggest that ecosystem responses to rainfall variability are based on a combination of physiological, life history, and genetic responses in these dominant grasses.