03518nas a2200193 4500008004100000245010400041210006900145260004300214490002100257520286800278653001503146653001303161653002103174653001303195653001803208100002203226700002303248856005303271 2016 eng d00aPatterns and ecological consequences of water uptake, redistribution, and loss in tallgrass prairie0 aPatterns and ecological consequences of water uptake redistribut aManhattan, KSbKansas State University0 vPhD Dissertation3 a

Water availability is a key driver of many plant and ecosystem processes in tallgrass prairies, yet we have a limited understanding of how grassland plants utilize water through space and time. Considering that tallgrass prairies experience tremendous heterogeneity in soil resources, identifying spatiotemporal variation in plant ecohydrology is critical for understanding current drivers of plant responses to water and for predicting ecosystem responses to future changes in climate. Here, I investigated the patterns, drivers, and ecological consequences of plant water use (e.g., water uptake, water redistribution, and water loss) in a native tallgrass prairie located in northeastern Kansas, USA. Using a combination of leaf gas exchange, sap flow, and isotopic techniques, I addressed four main questions: 1) How does fire and grazing by bison impact use of water from different sources and niche overlap for common grasses, forbs, and shrubs? 2) Does hydraulic lift occur in grazed and ungrazed tallgrass prairie, and does this impact facilitation for water within grassland communities? 3) What are the patterns and drivers of nocturnal transpiration in common grassland species? 4) How does diel stem sap flow and canopy transpiration vary among common grassland species?

I found that bison grazing increased the depth of water uptake by Andropogon gerardii and Rhus glabra, reducing niche overlap with co-occurring species. Conversely, grazing did not affect hydraulic lift, which was generally uncommon and likely limited by nocturnal transpiration. Further, leaf gas exchange measurements indicated that nocturnal transpiration occurred commonly in tallgrass prairie plants and was greatest among grasses and early in the growing season. Nocturnal transpiration was not driven by vapor pressure deficit or soil moisture, as commonly observed in other systems, but was regulated by nocturnal stomatal conductance in most species. Finally, I found that daytime sap flow rates were variable among species and functional types, with larger flux rates among woody species. Nocturnal sap flow rates were more consistent across species, which caused nighttime sap flow and transpiration to account for a larger proportion of daily flux rates in grasses than in forbs or shrubs. These results show that water uptake, water redistribution, and water loss are all influenced by different biotic and abiotic drivers and have varying ecological impacts across a heterogeneous landscape. Additionally, extensive differences in water flux exist among co-occurring species and plant functional groups, which likely reflect varying strategies to tolerate water limitation. These results suggest that shifts in the abundance of these species with future climate changes, or with ecosystem state changes, will likely impact ecosystem-level water balance.

10aGrasslands10aIsotopes10aPlant physiology10aSap flow10aTranspiration1 aO'Keefe, Kimberly1 aNippert, Jesse, B. uhttp://krex.k-state.edu/dspace/handle/2097/3451402086nas a2200229 4500008004100000245010700041210006900148300001300217490000800230520136700238653002301605653001601628653001501644653001301659653001801672653002401690100001701714700001601731700002001747700002301767856006601790 2012 eng d00aCommunity traitscape of foliar nitrogen isotopes reveals N availabiity patterns in a tallgrass prairie0 aCommunity traitscape of foliar nitrogen isotopes reveals N avail a395 -4030 v3563 a

Background and aims Nutrients are important determinants of community assembly, yet the roles they play in structuring plant communities are still poorly understood. One inferential approach to understanding how environmental factors structure plant communities is examining the distribution of key functional traits among species of a community—a community traitscape. Methods To better understand how nitrogen (N) and water availability structure grasslands, we measured N concentrations and isotope ratios for 366 herbaceous species in a mesic N-limited temperate grassland, Konza Prairie. We also compared foliar N concentrations and N isotopes between Konza species and a global dataset. Results Species that had either high foliar N concentrations or high δ15NL were not necessarily more or less abundant on the landscape nor more or less likely to be found in uplands, grazed areas, or burned areas. Apparently there are unique hot spots of high N availability at Konza and the typical non-Fabaceae Konza species occupies sites with greater N availability than found globally. Conclusions Although nascent, the Konza traitscapes suggest that plant diversity in nutrient-limited communities might be strongly dependent on high-nutrient availability sites that enable high-fertility species to persist in a matrix of low nutrient availability.

10aCommunity assembly10adisturbance10aGrasslands10aIsotopes10aKonza Prairie10aResource limitation1 aCraine, J.M.1 aTowne, E.G.1 aOcheltree, T.W.1 aNippert, Jesse, B. uhttps://link.springer.com/article/10.1007%2Fs11104-012-1141-7