02546nas a2200133   4500008004100000245008000041210006900121300001300190490000600203520206800209100001702277700002002294856009802314       2003                        eng d00aAbiotic constraints on the establishment of Quercus seedlings in grasslands0 aAbiotic constraints on the establishment of Quercus seedlings in  a266 -2750 v93 aHigh evaporative demand and periodic drought characterize the growing season in midwestern grasslands relative to deciduous forests of the eastern US, and predicted climatic changes suggest that these climatic extremes may be exacerbated. Despite this less than optimal environment for tree seedling establishment, deciduous trees have expanded into adjacent tallgrass prairie within the last century leading to a dramatic land cover change. In order to determine the role of light and temperature on seedling establishment, we assessed carbon and water relations and aboveground growth of first-year Quercus macrocarpa seedlings exposed to one of three conditions: (1) intact tallgrass prairie communities (control), (2) aboveground herbaceous biomass removed (grass removal), and (3) shade plus biomass removal to reduce light (PFD) to levels typical of the grassland-forest ecotone (shade). In the 2000 growing season, precipitation was 35% below the long-term average, which had a significant negative effect on oak seedling carbon gain at midseason (photosynthesis declined to 10% of maximum rates). However, net photosynthesis and stomatal conductance in the shade treatment was ca. 2.5 and 1.5 times greater, respectively, than in control treatment seedlings during this drought. During this period, leaf and air temperatures in control seedlings were similar whereas leaf temperatures in the shade treatment remained below air temperature. A late-season recovery period, coincident with decreased air temperatures, resulted in increased net photosynthesis for all seedlings. Increased photosynthetic rates and water relations in shaded seedlings compared to seedlings in full sun suggest that, at least in dry years, high light and temperature may negatively impact oak seedling performance. However, high survival rates for all seedlings indicate that Q. macrocarpa seedlings are capable of tolerating both present-day and future climatic extremes. Unless historic fire regimes are restored, forest expansion and land cover change are likely to continue.1 aDanner, B.T.1 aKnapp, Alan, K.  uhttp://knz.lternet.edu/content/abiotic-constraints-establishment-quercus-seedlings-grasslands00772nas a2200205   4500008004100000245010400041210006900145260004400214300001300258653002200271100001200293700002000305700002000325700001900345700001700364700001900381700001800400700002000418856012800438       2003                        eng d00aRainfall timing, soil moisture dynamics, and plant responses in a mesic tallgrass prairie ecosystem0 aRainfall timing soil moisture dynamics and plant responses in a   aTucson, AZbUniversity of Arizona Press  a147 -16310atallgrass prairie1 aFay, P.1 aKnapp, Alan, K.1 aBlair, John, M.1 aCarlisle, J.D.1 aDanner, B.T.1 aMcCarron, J.K.1 aWeltzin, J.F.1 aMcPherson, G.R.  uhttp://knz.lternet.edu/content/rainfall-timing-soil-moisture-dynamics-and-plant-responses-mesic-tallgrass-prairie-ecosystem00700nas a2200205   4500008004100000245008600041210006900127300001300196490000800209100001400217700001900231700001700250700001500267700001900282700001600301700002000317700002000337700002400357856011300381       2002                        eng d00aAltered rainfall patterns, gas exchange and growth in C3 and C4 grassland species0 aAltered rainfall patterns gas exchange and growth in C3 and C4 g  a549 -5570 v1631 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://knz.lternet.edu/content/altered-rainfall-patterns-gas-exchange-and-growth-c3-and-c4-grassland-species01540nas a2200229   4500008004100000245009000041210006900131300001500200490000800215520084900223100002001072700001401092700002001106700002401126700001601150700001901166700001701185700001701202700001501219700001901234856005701253       2002                        eng d00aRainfall variability, carbon cycling and plant species diversity in a mesic grassland0 aRainfall variability carbon cycling and plant species diversity   a2202 -22050 v2983 a<p>Ecosystem responses to increased variability in rainfall, a prediction of general circulation models, were assessed in native grassland by reducing storm frequency and increasing rainfall quantity per storm during a 4-year experiment. More extreme rainfall patterns, without concurrent changes in total rainfall quantity, increased temporal variability in soil moisture and plant species diversity. However, carbon cycling processes such as soil CO2 flux, CO2 uptake by the dominant grasses, and aboveground net primary productivity (ANPP) were reduced, and ANPP was more responsive to soil moisture variability than to mean soil water content. Our results show that projected increases in rainfall variability can rapidly alter key carbon cycling processes and plant community composition, independent of changes in total precipitation.</p>1 aKnapp, Alan, K.1 aFay, P.A.1 aBlair, John, M.1 aCollins, Scott., L.1 aSmith, M.D.1 aCarlisle, J.D.1 aHarper, C.W.1 aDanner, B.T.1 aLett, M.S.1 aMcCarron, J.K.  uhttps://science.sciencemag.org/content/298/5601/220202614nas a2200277   4500008004100000245008000041210006900121300001300190490000700203520177300210653001201983653001701995653002102012653001202033653002202045100001402067700001902081700001702100700001502117700001902132700001602151700002002167700002002187700002402207856010502231       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://knz.lternet.edu/content/carbon-and-water-relations-juvenile-quercus-species-tallgrass-prairie00587nas a2200133   4500008004100000245010900041210006900150260004300219300001000262490001400272653002200286100001700308856012800325       2001                        eng d00aGallery forest expansion in tallgrass prairie: mechanisms facilitating oak seedling and juvenile success0 aGallery forest expansion in tallgrass prairie mechanisms facilit  aManhattan, KSbKansas State University  a1 -750 vMS Thesis10atallgrass prairie1 aDanner, B.T.  uhttp://knz.lternet.edu/content/gallery-forest-expansion-tallgrass-prairie-mechanisms-facilitating-oak-seedling-and-juvenile02348nas a2200181   4500008004100000245018500041210006900226300001300295490000700308520164000315653002001955653001201975653001301987653001202000100001702012700002002029856011702049       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://knz.lternet.edu/content/growth-dynamics-gallery-forest-oak-seedlings-quercus-macrocarpa-michx-and-quercus