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ARS Home » Plains Area » Miles City, Montana » Livestock and Range Research Laboratory » Research » Publications at this Location » Publication #212233
Title: Primary Productivity and Precipitation Use Efficiency in Mixed-Grass Prairie: A Comparison of Northern and Southern U.S. Sites

Author
item Vermeire, Lance
item HEITSCHMIDT, ROD - USDA-ARS, RETIRED
item Rinella, Matthew - Matt

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/26/2009
Publication Date: 5/1/2009
Citation: Vermeire, L.T., Heitschmidt, R.K., Rinella, M.J. 2009. Primary Productivity and Precipitation Use Efficiency in Mixed-Grass Prairie: A Comparison of Northern and Southern U.S. Sites. Rangeland Ecology and Management 62:230-239.

Interpretive Summary: Precipitation is a primary factor controlling rangeland structure and function and as such, precipitation-use efficiency (PUE) is a key determinant of aboveground plant production. We used 76 datasets to contrast production and PUE between northern (southeast Montana) and southern (north Texas) mixed-grass prairies. Effects of varying amounts and temporal distribution of precipitation on PUE were examined at the Montana site, using a rainout shelter and irrigation. Results show that: 1) production was about 25% less in Montana than Texas (188 vs 237 g m**-2); 2) plant functional type (cool-season versus warm-season) composition varied between the two study locations, with cool-season perennial grasses (CSPG) being dominant in Montana (52%) and warm-season perennial grasses being dominant in Texas (47%); 3) production dynamics varied between the two sites with 90% of production completed by 1 July in Montana as compared to 31 August in Texas; 4) average PUE estimates were greater in Montana (0.56 g dry matter m**-2 mm**-1 of precipitation) than Texas (0.40 g m**-2 mm**-1); and 5) PUE estimates varied among plant functional types and locations, with CSPG estimates being greater in Montana than Texas (0.31 vs, 0.11 g m**-2 mm**-1) and WSPG estimates being greater in Texas than Montana (0.19 vs, 0.15 g m**-2 mm**-1). Seasonal droughts and supplemental irrigations at the Montana site altered production, plant functional type biomass composition, and PUE estimates substantially. Results show convincingly that variation in PUE was largely a function of plant functional type composition relative to amount and seasonal distribution of precipitation.

Technical Abstract: Precipitation is a primary determinant of terrestrial ecosystem structure and function and as such, precipitation-use efficiency (PUE) is a key determinant of aboveground net primary production (ANPP). We used 76 datasets to contrast ANPP and PUE estimates between northern (southeast Montana) and southern (north Texas) mixed-grass prairies. Effects of varying amounts and temporal distribution of precipitation on PUE were examined at the Montana site, using a rainout shelter and irrigation. Results show that: 1) ANPP was about 25% less in Montana than Texas (188 vs 237 g m**-2); 2) plant function type (PFT) composition varied between the two study locations, with cool-season perennial grasses (CSPG) being the dominant PFT in Montana (52%) and warm-season perennial grasses (WSPG) being the dominant PFT in Texas (47%); 3) production dynamics varied between the two sites with 90% of ANPP completed by 1 July in Montana as compared to 31 August in Texas; 4) average PUE estimates were greater in Montana (0.56 g dry matter m**-2 mm**-1 of precipitation) than Texas (0.40 g m**-2 mm**-1); and 5) PUE estimates varied among PFT and locations, with CSPG estimates being greater in Montana than Texas (0.31 vs, 0.11 g m**-2 mm**-1) and WSPG estimates being greater in Texas than Montana (0.19 vs, 0.15 g m**-2 mm**-1). Seasonal droughts and supplemental irrigations at the Montana site altered ANPP, PFT biomass composition, and PUE estimates substantially. Results show convincingly that variation in PUE was largely a function of PFT composition relative to amount and seasonal distribution of precipitation.