@article {KNZ00590,
	title = {Photosynthetic gas exchange and water relations responses of three tallgrass prairie species to elevated carbon dioxide and moderate drought},
	journal = {International Journal of Plant Science},
	volume = {158},
	year = {1997},
	pages = {608 -616},
	abstract = {Undisturbed tallgrass prairie was exposed to ambient and elevated (twice-ambient) levels of atmospheric CO2 and experimental dry periods. Seasonal and diurnal midday leaf water potential (Ψ leaf), net photosynthesis $(A_{\text{net}})$, and stomatal conductance (g s) responses of three tallgrass prairie growth forms{\textemdash}a C4 grass, Andropogon gerardii; a broad-leaved woody C3 shrub, Symphiocarpos orbiculatus; and a C3 perennial forb, Salvia pitcheri{\textemdash}were assessed. $\Psi _{\text{leaf}}$ in A. gerardii and S. orbiculatus was higher under elevated CO2, regardless of soil moisture, while $\Psi _{\text{leaf}}$ in S. pitcheri responded only to drought. Elevated CO2 always stimulated $A_{\text{net}}$ in the C3 species, while A. gerardii $A_{\text{net}}$ increased only under dry conditions. However, $A_{\text{net}}$ under elevated CO2 in the C3 species declined with drought but not in the C4 grass. Under wet conditions, g s reduced in elevated CO2 for all species. During dry periods, gs at elevated CO2 was sometimes higher than in ambient CO2. Our results support claims that elevated CO2 will stimulate tallgrass prairie productivity during dry periods and possibly reduce temporal and spatial variability in productivity in these grasslands.},
	keywords = {LTER-KNZ, Water relations},
	url = {http://www.jstor.org/stable/2474921},
	author = {Hamerlynck, E.P. and McAllister, C.A. and Alan K. Knapp and J.M. Ham and Owensby, C.E.}
}
@article {KNZ00545,
	title = {Early season cuticular conductance and gas exchange in two oaks near the western edge of their range},
	journal = {Trees},
	volume = {10},
	year = {1996},
	pages = {403 -409},
	abstract = {Seasonal 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 ({\textpm}0.274) mmol m-2 s-1 in bur oak, and 2.66 ({\textpm}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.},
	keywords = {LTER-KNZ, Cuticular conductance, Gallery forests, Leaf development, photosynthesis, Quercus},
	doi = {10.1007/BF02185644},
	author = {Hamerlynck, E.P. and Alan K. Knapp}
}
@article {KNZ00546,
	title = {Photosynthetic and stomatal responses to high temperature and light in two oaks at the western limit of their range},
	journal = {Tree Physiology},
	volume = {16},
	year = {1996},
	pages = {557 -565},
	abstract = {Bur oak (Quercus macrocarpa Michx.) and chinquapin oak (Q. muehlenbergii Engl.) leaves were exposed to high temperatures at various photosynthetic photon flux densities under laboratory conditions to determine if species-specific responses to these factors were consistent with the distribution of these oaks in gallery forests in the tallgrass prairies of northeastern Kansas, USA. Measurements of the ratio of chlorophyll fluorescence decrease, Rfd, indicated that chinquapin oak maintained greater photosynthetic capacity than bur oak across all tested combinations of irradiance (100, 400, 700 and 1000 μmol m-2 s-1) and temperature (40, 42, 44, 46 and 48 {\textdegree}C). In both oak species, manipulation of leaf temperature to about 47 {\textdegree}C for 45 min in the field led to a 45\% decrease in carbon assimilation up to one week after the heat treatment, and to sharp reductions in stomatal conductance. Photosynthetic recovery patterns indicated that bur oak took longer to recover from heat stress than chinquapin oak, suggesting that heat stress may be important in determining distribution patterns of these oak species. Based on a comparison of the results with data from other forest species, we conclude that the photosynthetic temperature tolerances of bur oak and chinquapin oaks facilitate their dominance at the western limit of the eastern deciduous forest.},
	keywords = {LTER-KNZ, Chlorophyll fluorescence, heat stress, Quercus macrocarpa, Quercus muehlenbergii},
	doi = {10.1093/treephys/16.6.557},
	author = {Hamerlynck, E.P. and Alan K. Knapp}
}
@article {KNZ00556,
	title = {Responses in stomatal conductance to elevated CO2 in 12 grassland species that differ in growth form},
	journal = {Vegetatio},
	volume = {125},
	year = {1996},
	pages = {31 -41},
	abstract = {Responses in stomatal conductance (g st ) and leaf xylem pressure potential (ψ leaf ) to elevated CO2 (2x ambient) were compared among 12 tallgrass prairie species that differed in growth form and growth rate. Open-top chambers (OTCs, 4.5 m diameter, 4.0 m in height) were used to expose plants to ambient and elevated CO2 concentrations from April through November in undisturbed tallgrass prairie in NE Kansas (USA). In June and August, ψ leaf was usually higher in all species at elevated CO2 and was lowest in adjacent field plots (without OTCs). During June, when water availability was high, elevated CO2 resulted in decreased g st in 10 of the 12 species measured. Greatest decreases in g st (ca. 50\%) occurred in growth forms with the highest potential growth rates (C3 and C4 grasses, and C3 ruderals). In contrast, no significant decrease in g st was measured in the two C3 shrubs. During a dry period in September, reductions in g st at elevated CO2 were measured in only two species (a C3 ruderal and a C4 grass) whereas increased g st at elevated CO2 was measured in the shrubs and a C3 forb. These increases in g st were attributed to enhanced ψ leaf in the elevated CO2 plants resulting from increased soil water availability and/or greater root biomass. During a wet period in September, only reductions in g st were measured in response to elevated CO2. Thus, there was significant interspecific variability in stomatal responses to CO2 that may be related to growth form or growth rate and plant water relations. The effect of growth in the OTCs, relative to field plants, was usually positive for g st and was greatest (>30\%) when water availability was low, but only 6{\textendash}12\% when ψ leaf was high.
The results of this study confirm the importance of considering interactions between indirect effects of high CO2 of plant water relations and direct effects of elevated CO2 on g st , particularly in ecosystems such as grasslands where water availability often limits productivity. A product of this interaction is that the potential exists for either positive or negative responses in g st to be measured at elevated levels of CO2.},
	keywords = {LTER-KNZ, elevated CO2, Growth form, Stomatal Conductance, tallgrass prairie, Water relations},
	doi = {10.1007/BF00045202},
	author = {Alan K. Knapp and Hamerlynck, E.P. and J.M. Ham and Owensby, C.E.}
}
@phdthesis {KNZ00491,
	title = {The ecophysiology of bur oak (Quercus marocarpa  Michx.) and chinquapin oak (Quercus muehlenbergii  Emglm.) at the western limit of their distribution},
	volume = {PhD Dissertation},
	year = {1995},
	pages = {1 -103},
	school = {Kansas State University},
	type = {Ph.D. Thesis},
	address = {Manhattan, KS},
	keywords = {LTER-KNZ, Ecophysiology},
	author = {Hamerlynck, E.P.}
}
@proceedings {KNZ00490,
	title = {Environmental and physiological factors influencing the distribution of oaks near the edge of their range},
	year = {1995},
	pages = {17 -20},
	keywords = {LTER-KNZ},
	url = {http://images.library.wisc.edu/EcoNatRes/EFacs/NAPC/NAPC14/reference/econatres.napc14.ehamerlynck.pdf},
	author = {Hamerlynck, E.P. and Alan K. Knapp},
	editor = {D.C. Hartnett}
}
@article {KNZ00455,
	title = {Effect of elevated C02 on stomatal density and distribution in a C4 grass and a C3 forb under field conditions},
	journal = {Annals of Botany},
	volume = {74},
	year = {1994},
	pages = {595 -599},
	abstract = {Two common tallgrass prairie species, Andropogon gerardii, the dominant C4 grass in this North American grassland, and Salvia pitcheri, a C3 forb, were exposed to ambient and elevated (twice ambient) CO2 within open-top chambers throughout the 1993 growing season. After full canopy development, stomatal density on abaxial and adaxial surfaces, guard cell length and specific leaf mass (SLM; mg cm-2) were determined for plants in the chambers as well as in adjacent unchambered plots. Record high rainfall amounts during the 1993 growing season minimized water stress in these plants (leaf xylem pressure potential was usually > -1{\textperiodcentered}5 MPa in A. gerardii) and also minimized differences in water status among treatments. In A. gerardii, stomatal density was significantly higher (190 {\textpm} 7 mm-2; mean {\textpm} s.e.) in plants grown outside of the chambers compared to plants that developed inside the ambient CO2 chambers (161 {\textpm} 5 mm-2). Thus, there was a significant {\textquoteright}chamber effect{\textquoteright} on stomatal density. At elevated levels of CO2, stomatal density was even lower (P < 0{\textperiodcentered}05; 121 {\textpm} 5 mm-2). Most stomata were on abaxial leaf surfaces in this grass, but the ratio of adaxial to abaxial stomatal density was greater at elevated levels of CO2. In S. pitcheri, stomatal density was also significantly lower when plants were grown in the open-top chambers (235 {\textpm} 10 mm-2 outside vs. 140 {\textpm} 6 mm-2 in the ambient CO2 chamber). However, stomatal density was greater at elevated CO2 (218 {\textpm} 12 mm-2) compared to plants from the ambient CO2 chamber. The ratio of stomata on adaxial vs. abaxial surfaces did not vary significantly in this herb. Guard cell lengths were not significantly affected by growth in the chambers or by elevated CO2 for either species. Growth within the chambers resulted in lower SLM in S. pitcheri, but CO2 concentration had no effect. In A. gerardii, SLM was lower at elevated CO2. These results indicate that stomatal and leaf responses to elevated CO2 are species specific, and reinforce the need to assess chamber effects along with treatment effects (CO2) when using open-top chambers.},
	keywords = {LTER-KNZ, Andropogon gerardii, elevated CO2, Salvia pitcheri, stomatal density, tallgrass prairie},
	doi = {10.1006/anbo.1994.1159},
	author = {Alan K. Knapp and Cocke, M. and Hamerlynck, E.P. and Owensby, C.E.}
}
@article {KNZ00443,
	title = {Leaf-level responses to light and temperature in two co-occurring Quercus (Fagaceae ) species: implications for tree distribution patterns},
	journal = {Forest Ecology and Management},
	volume = {68},
	year = {1994},
	pages = {149 -159},
	abstract = {Leaf-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 {\textpm} 3.02 μmol photons m-2 s-1 in sun leaves vs. 29.25 {\textpm} 0.29 photons m-2 s-1 in shade leaves; chinquapin oak, 49.47 {\textpm} 2.82 photons m-2 s-1 in sun leaves vs. 26.48 {\textpm} 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{\textdegree}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.},
	keywords = {LTER-KNZ, gallery forest, Light acclimation, photosynthesis, Quercus, tallgrass prairie, Temperature tolerance},
	doi = {10.1016/0378-1127(94)90042-6},
	author = {Hamerlynck, E.P. and Alan K. Knapp}
}
@article {KNZ00444,
	title = {Stomatal responses to variable sunlight in Bur Oak (Quercus macrocarpa Michx.) leaves with different photosynthetic capacities},
	journal = {International Journal of Plant Science},
	volume = {155},
	year = {1994},
	pages = {583 -587},
	abstract = {Interspecific comparisons of stomatal response to variable light have generally supported the hypothesis that stomatal adjustments are more rapid in plants with high photosynthetic capacity. We compared stomatal responses to variable light in bur oak (Quercus macrocarpa) leaves that had low photosynthetic capacity and high apparent anthocyanins levels ("red leaves") with responses in green leaves. When incident sunlight was experimentally varied, stomatal conductance (gs) in red leaves was no less responsive than in green leaves. In both leaf types, gs declined at the same rate ($18.9\ {\rm mmol}\ {\rm m}^{-2}\ {\rm s}^{-1}\ {\rm min}^{-1}$) upon shading and increased at the same rate ($13.4\ {\rm mmol}\ {\rm m}^{-2}\ {\rm s}^{-1}\ {\rm min}^{-1}$) when reilluminated. The only difference in stomatal response in red leaves was an overall reduction in gs compared with green leaves. In shade, net photosynthetic rates (${\rm A}_{\text{net}}$) in red leaves were very low (${\rm ca}.\ 2.3\ \mu {\rm mol}\ {\rm m}^{-2}\ {\rm s}^{-1}$) but still nearly 70\% of full sun rates ($3.2\ \mu {\rm mol}\ {\rm m}^{-2}\ {\rm s}^{-1}$). In contrast, ${\rm A}_{\text{net}}$ in green leaves reduced by nearly 50\% in shade ($7.2\ \mu {\rm mol}\ {\rm m}^{-2}\ {\rm s}^{-1}$) relative to full sun rates ($14.1\ \mu {\rm mol}\ {\rm m}^{-2}\ {\rm s}^{-1}$). Internal CO2 concentrations ( C i) were always ${\rm ca}.\ 50\ \mu {\rm L}\ {\rm L}^{-1}$ higher in red than in green leaves. Upon reillumination, ${\rm A}_{\text{net}}$ in red leaves immediately returned to preshade levels, while green leaves recovered more slowly, perhaps because of stomatal limitation, as indicated by reduced C i. We concluded that, although rapid stomatal responses are often correlated with photosynthetic capacity among species, within Quercus macrocarpa, stomatal responses to rapidly varying light are not related to leaf photosynthetic capacity.},
	keywords = {LTER-KNZ},
	url = {http://www.jstor.org/stable/2475031},
	author = {Hamerlynck, E.P. and Alan K. Knapp}
}
