02060nas a2200181   4500008004100000245012000041210006900161300001300230490000700243520137000250653002901620653001601649653002301665653002601688100002101714700002001735856012301755       1996                        eng d00aPhotosynthetic and stomatal responses to high temperature and light in two oaks at the western limit of their range0 aPhotosynthetic and stomatal responses to high temperature and li  a557 -5650 v163 aBur 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 °C). In both oak species, manipulation of leaf temperature to about 47 °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.10aChlorophyll fluorescence10aheat stress10aQuercus macrocarpa10aQuercus muehlenbergii1 aHamerlynck, E.P.1 aKnapp, Alan, K.  uhttp://knz.lternet.edu/content/photosynthetic-and-stomatal-responses-high-temperature-and-light-two-oaks-western-limit