Frequency and Extent of Water Limitation to Primary Production in a Mesic Temperate Grassland |
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Authors: | A K Knapp J M Briggs J K Koelliker |
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Institution: | (1) Division of Biology, Kansas State University, Manhattan, Kansas 66506, USA; and, US;(2) Department of Biological and Agricultural Engineering, Kansas State University, Manhattan, Kansas 66506, USA, US |
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Abstract: | The frequency and extent of water limitation to aboveground net primary production (ANPP) in a mesic grassland in NE Kansas
(Konza Prairie, USA) was assessed with an 8-year irrigation experiment. Since 1991, transects spanning upland and lowland
sites in annually burned, ungrazed tallgrass prairie were provided with supplemental water to satisfy evapotranspirational
demands. This protocol minimized water limitations during the growing season, as well as interannual variability in water
stress. Irrigation of this mesic grassland increased ANPP in 6 of 8 years by an average of 26% when compared to control transects.
Although interannual variation in ANPP was greater in uplands than lowlands at nominal levels of precipitation, reducing interannual
variability in water availability via irrigation eliminated topographic differences; the irrigation protocol also reduced
interannual variability in ANPP by as much as 40%. The addition of supplemental water enabled us to extend the relationship
between annual precipitation and ANPP in grasslands to precipitation levels (average, 1153 mm; maximum, 1346 mm) similar to
those experienced by more mesic grasslands that today exist only as remnants several hundred kilometers east of Kansas. This
relationship was linear (r
2= 0.81), with maximum ANPP (738 g/m2) similar to values reported for sites in Illinois and Wisconsin. After 8 years of irrigation, production of the C3 forb component was twice that in control sites. These results indicate that water limitations in grasslands at the western
edge of the presettlement extent of tallgrass prairie affect ANPP in most years and that this high frequency of water limitation
may lead to greater dominance of the C4 grasses than is seen in more eastern grassland sites.
Received 18 January 2000; accepted 19 July 2000. |
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Keywords: | :Andropogon gerardii C 4 grasses forbs grassland irrigation leaf water potential primary production tallgrass prairie water limitation |
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