ECOSYSTEM ECOLOGY - ORIGINAL PAPER Linking plant growth responses across topographic gradients in tallgrass prairie Jesse B. Nippert • Troy W. Ocheltree • Adam M. Skibbe • Laura C. Kangas • Jay M. Ham • Kira B. Shonkwiler Arnold • Nathaniel A. Brunsell Received: 14 April 2010 / Accepted: 17 February 2011 Ó Springer-Verlag 2011 Abstract Aboveground biomass in grasslands varies according to landscape gradients in resource availability and seasonal patterns of growth. Using a transect spanning a topographic gradient in annually burned ungrazed tall- grass prairie, we measured changes in the height of four abundant C 4 grass species, LAI, biomass, and cumulative carbon flux using two closely located eddy flux towers. We hypothesized that seasonal patterns of plant growth would be similar across the gradient, but the magnitude of growth and biomass accumulation would vary by topographic position, reflecting spatial differences in microclimate, slope, elevation, and soil depth. Thus, identifying and measuring local growth responses according to topographic variability should significantly improve landscape predic- tions of aboveground biomass. For most of the growth variables measured, classifying topography into four posi- tions best captured the inherent spatial variability. Biomass produced, seasonal LAI and species height increased from the upland and break positions to the slope and lowland. Similarly, cumulative carbon flux in 2008 was greater in lowland versus upland tower locations (difference of 64 g m -2 by DOY 272). Differences in growth by topographic position reflected increased pro- duction of flowering culms by Andropogon gerardii and Sorghastrum nutans in lowland. Varying growth responses by these species may be a significant driver of biomass and carbon flux differences by topographic position, at least for wet years. Using a digital elevation model to classify the watershed into topographic posi- tions, we performed a geographically weighted regression to predict landscape biomass. The minimum and maxi- mum predictions of aboveground biomass for this watershed had a large range (86–393 t per 40.4 ha), illustrating the drastic spatial variability in growth within this annually-burned grassland. Keywords ANPP Á Flux footprint Á Eddy covariance Á LAI Á Mesic grassland Á Topography Introduction During the mid-nineteenth century, the grassland region of central North America was termed ‘‘the Great Plains’’ to reflect the expansive skylines and flat valley bottoms common across the landscape (Lewis 1966). This Communicated by Tim Seastedt. Electronic supplementary material The online version of this article (doi:10.1007/s00442-011-1948-6) contains supplementary material, which is available to authorized users. J. B. Nippert (&) Á T. W. Ocheltree Á A. M. Skibbe Á L. C. Kangas Division of Biology, Kansas State University, Manhattan, KS, USA e-mail: nippert@ksu.edu J. M. Ham Department of Soils and Crop Sciences, Colorado State University, Fort Collins, CO, USA K. B. Shonkwiler Arnold Department of Horticulture, Forestry and Recreation Resources, Kansas State University, Manhattan, KS, USA N. A. Brunsell Department of Geography, University of Kansas, Lawrence, KS, USA Present Address: L. C. Kangas School of Forest Resources and Environmental Science, Michigan Technological University, Houghton, MI, USA 123 Oecologia DOI 10.1007/s00442-011-1948-6