02617nas a2200277   4500008004100000245008000041210006900121300001300190490000700203520177300210653001201983653001701995653002102012653001202033653002202045100001402067700001902081700001702100700001502117700001902132700001602151700002002167700002002187700002402207856010802231       2001                        eng d00aCarbon and water relations of juvenile Quercus species in tallgrass prairie0 aCarbon and water relations of juvenile Quercus species in tallgr  a807 -8160 v123 aIn ecosystems where environments are extreme, such as deserts, adult plant species may facilitate the establishment and growth of seedlings and juveniles. Because high temperatures and evaporative demand characterize tall-grass prairies of the central United States (relative to forests), we predicted that the grassland-forest ecotone, by minimizing temperature extremes and moderating water stress, may function to facilitate the expansion of Quercus species into undisturbed tall-grass prairie. We assessed the carbon and water relations of juvenile Quercus macrocarpa and Q. muhlenbergii, the dominant tree species in gallery forests of northeast Kansas, in ecotone and prairie sites. To evaluate the potentially competitive effects of neighboring herbaceous biomass on these oaks, juveniles (< 0.5 m tall) of both species also were subjected to either: (1) removal of surrounding above-ground herbaceous biomass, or (2) control (prairie community intact) treatments. Herbaceous biomass removal had no significant effect on gas exchange or water relations in these oak species in either the prairie or the ecotone environment. Although the ecotone did alleviate some environmental extremes, photosynthetic rates and stomatal conductance were ca. 20 % higher (p < 0.05) in both oaks in prairie sites vs. the ecotone. Moreover, although leaf temperatures on average were higher in oaks in the prairie, high leaf temperatures in the ecotone had a greater negative effect on photosynthesis. These data suggest that the grassland-forest ecotone did not facilitate the growth of Quercus juveniles expanding into this grassland. Moreover, the carbon and water relations of juvenile oaks in the prairie appeared to be unaffected by the presence of the dominant C4 grasses.10aEcotone10aFacilitation10aforest expansion10aQuercus10atallgrass prairie1 aFay, P.A.1 aCarlisle, J.D.1 aDanner, B.T.1 aLett, M.S.1 aMcCarron, J.K.1 aStewart, C.1 aKnapp, Alan, K.1 aBlair, John, M.1 aCollins, Scott., L.  uhttp://lter.konza.ksu.edu/content/carbon-and-water-relations-juvenile-quercus-species-tallgrass-prairie02351nas a2200181   4500008004100000245018500041210006900226300001300295490000700308520164000315653002001955653001201975653001301987653001202000100001702012700002002029856012002049       2001                        eng d00aGrowth dynamics of gallery forest oak seedlings (Quercus macrocarpa Michx. and Quercus muhlenbergii Engelm.) from gallery forests: implications for forest expansion into grasslands0 aGrowth dynamics of gallery forest oak seedlings Quercus macrocar  a271 -2770 v153 aSeedling growth dynamics of Quercus macrocarpa Michx. and Quercus muhlenbergii Engelm. were compared over a 3-month period under optimal growth conditions. These two species are the dominant trees at the western limit of the eastern deciduous forest, and are typically confined to gallery forests along stream beds in tallgrass prairie. Since tallgrass prairie is characterized by a highly variable climate and is prone to periodic drought, we hypothesized that these oaks would have rapid root growth and produce deep taproots as seedlings, enabling them to avoid drought stress and persist in this region. These traits may also facilitate forest expansion into the more xeric tallgrass prairie if fires are suppressed. Taproots of Q. macrocarpa and Q. muhlenbergii grew to approximately 140 cm and 100 cm in length, respectively, after 104 days. In both species, 65% or more of seedling biomass was allocated below ground, and root/total biomass was significantly greater in Q. muhlenbergii at 0–20 and 21–40 days after germination. The seedling taproot elongation rates reported here are much greater than rates reported in other eastern deciduous forest trees. Long-term precipitation data and soil moisture patterns from tallgrass prairie, when combined with rapid taproot elongation rates, suggest that soil moisture may not limit oak establishment or growth in tallgrass prairie in most years, although water uptake by roots was not measured in this study. Other factors, such as fire, herbivory, and seed predation and dispersal may be equally important in constraining the distribution of these species to gallery forests.10aGallery forests10aQuercus10aSeedling10aTaproot1 aDanner, B.T.1 aKnapp, Alan, K.  uhttp://lter.konza.ksu.edu/content/growth-dynamics-gallery-forest-oak-seedlings-quercus-macrocarpa-michx-and-quercus02129nas a2200193   4500008004100000245010500041210006900146300001300215490000700228520143200235653002601667653002001693653002101713653001901734653001201753100002101765700002001786856012901806       1996                        eng d00aEarly season cuticular conductance and gas exchange in two oaks near the western edge of their range0 aEarly season cuticular conductance and gas exchange in two oaks   a403 -4090 v103 aSeasonal changes in minimum leaf conductance to water vapor (gmin), an estimate of cuticular conductance, and photosynthetic gas exchange in two co-occurring oak species in north-east Kansas (USA) were examined to determine if leaf gas exchange characteristics correlated with differences in tree distribution. Bur oak (Quercus macrocarpa Michx.) is more abundant in mesic gallery forest sites, whereas chinquapin oak (Quercus muehlenbergii Englm.) is more abundant in xeric sites. Early, during leaf expansion, gmin was significantly lower in chinquapin oak than in bur oak, though midday water potentials were similar. After leaves had fully expanded, gmin decreased to seasonal minimum values of 4.57 (±0.274) mmol m-2 s-1 in bur oak, and 2.66 (±0.156) mmol m-2 s-1 in chinquapin oak. Water potentials at these times were significantly higher in chinquapin oak. As leaves were expanding, photosynthesis (Anet) was significantly higher in chinquapin oak than in bur oak. Later in the growing season, Anet and gleaf increased dramatically in both species, and were significantly higher in bur oak relative to chinquapin oak. We concluded that bur and chinquapin oak have a number of leaf gas exchange characteristics that minimize seasonal water loss. These characteristics are distinct from trees from more mesic sites, and are consistent with the distribution patterns of these trees in tall-grass prairie gallery forests.10aCuticular conductance10aGallery forests10aLeaf development10aphotosynthesis10aQuercus1 aHamerlynck, E.P.1 aKnapp, Alan, K.  uhttp://lter.konza.ksu.edu/content/early-season-cuticular-conductance-and-gas-exchange-two-oaks-near-western-edge-their-range02956nas a2200205   4500008004100000245014300041210006900184300001300253490000700266520219300273653001902466653002202485653001902507653001202526653002202538653002602560100002102586700002002607856012302627       1994                        eng d00aLeaf-level responses to light and temperature in two co-occurring Quercus (Fagaceae ) species: implications for tree distribution patterns0 aLeaflevel responses to light and temperature in two cooccurring   a149 -1590 v683 aLeaf-level responses to light environment (sun vs. shade) and high temperature were compared in two gallery forest oaks, bur oak (Quercus macrocarpa) and chinquapin oak (Quercus muehlenbergii). Our goal was to determine if species-specific differences in response to light or temperature could explain the distribution of these oaks in tallgrass prairie gallery forests. On the Konza Prairie Research Natural Area in NE Kansas (USA), bur oak is more abundant than chinquapin oak along lower reaches of streams where the forests are most productive and canopy closure is greatest. We hypothesized that bur oak is better able to acclimate physiologically to reduced light availability than chinquapin oak. Leaf level acclimation to low light in both oaks occurred through reduced photosynthetic light compensation points (PLC) (bur oak, 60.77 ± 3.02 μmol photons m−2 s−1 in sun leaves vs. 29.25 ± 0.29 photons m−2 s−1 in shade leaves; chinquapin oak, 49.47 ± 2.82 photons m−2 s−1 in sun leaves vs. 26.48 ± 1.74 photons m−2s−1 in shade leaves), resulting from nearly 50% reductions in dark respiration and specific leaf mass in both species. Apparent quantum requirement (Qreq; mol photons mol−1 O2) did not differ between sun and shade leaves in either species, and only bur oak showed differences in sun and shade leaf shape. We also hypothesized that chinquapin oak, which is more abundant in exposed, upper stream reaches, has greater photosynthetic tolerance to the high temperatures characteristics of this region. The maximum temperature tolerances (Tmax) of these oaks were compared by measuring increases in chlorophyll fluorescence. For most of the growing season, Tmax in chinquapin oak was 2.0°C higher than in bur oak. Field measurements of leaf vs. air temperatures in seedlings and adult trees indicated that Tmax was more likely to be exceeded in bur than in chinquapin oak, particularly in seedlings exposed to high solar radiation loads. We concluded that differences in thermal tolerance, in addition to previously documented differences in water relations are important determinants of distributional patterns of these oaks within gallery forests.10agallery forest10aLight acclimation10aphotosynthesis10aQuercus10atallgrass prairie10aTemperature tolerance1 aHamerlynck, E.P.1 aKnapp, Alan, K.  uhttp://lter.konza.ksu.edu/content/leaf-level-responses-light-and-temperature-two-co-occurring-quercus-fagaceae-species