02026nas a2200133   4500008004100000245012500041210006900166300001300235490000700248520147900255653002201734100001801756856011801774       1991                        eng d00aEffects of fire in tallgrass prairie on growth and reproduction of prairie coneflower (Ratibida columnifera: Asteraceae)0 aEffects of fire in tallgrass prairie on growth and reproduction   a429 -4350 v783 a<p>Effects of fire on growth and reproduction of the perennial forb Ratibida columnifera were studied on the Konza Prairie Research Natural Area in northeastern Kansas, USA. Populations were sampled in seven different tallgrass prairie watersheds that varied in fire frequency and in the number of years elapsed since the last fire. Plants from sites not burned for many years were 2.6 times larger and produced 50% more stems than plants from recently burned sites. Number of seeds per plant was also higher in long-unburned sites due to greater numbers of flower heads per plant and greater numbers of achenes produced per head. Reproduction effort (ratio of inflorescence biomass to total vegetative biomass) was 33% lower in annually burned prairie than in any of the other sites. Significant differences in the relationships of inflorescence biomass to vegetative plant biomass in burned vs unburned sites indicated that burning causes direct changes in plant reproductive effort independent from its effects on plant size. There was no clear relationship between patterns of seed production among sites and patterns of R. columnifera abundance. Ratibida columnifera responses to fire are most likely a result of changes in the relative competitive abilities of forbs and the dominant perennial grasses due to post-fire changes in abiotic conditions rather than a result of direct effects of fire on the fate of buds and subsequent vegetative and floral development</p>10atallgrass prairie1 aHarnett, D.C.  uhttp://knz.lternet.edu/content/effects-fire-tallgrass-prairie-growth-and-reproduction-prairie-coneflower-ratibida02235nas a2200157   4500008004100000245010500041210006900146300001500215490000700230520163800237653002201875100002001897700001701917700001801934856012501952       1989                        eng d00aRelationship between mycorrhizal dependence and competitive ability of two tallgrass prairie grasses0 aRelationship between mycorrhizal dependence and competitive abil  a2608 -26150 v673 a<p>The impact of mycorrhizal symbiosis on growth of Andropogon gerardii (big bluestem) and Koeleria pyranidata (junegrass) was compared. Andropogon gerardii was 98% dependent on the symbiosis, whereas K. pyranidata displayed less than 0.02% dependence. Mycorrhizal fungus inoculation resulted in 50 times larger A. gerardii plants but did not alter growth of K. pyradidata. When competing in pairs, A. gerardii dominated when the mycorrhizal symbiosis was present and K. pyradidata dominated when it was not present. Dry weight of mycorrhizal A. perardii was altered, whether grown alone or with K. pyranidata, but mycorrhizal K. pyranidata grew well only in the absence of competition and failed to grow appreciably if A. gerardii was present. Without mycorrhizal fungus inoculation, A. gerardii did not grow and had no deleterious effects on K. pyranidata. When P. fertilization was substituted for mycorrhizal fungus inoculation, A. gerardii grew better alone than in competition with K. pyranidata at low P levels but was not affected by competition at high P levels. Koeleria pyranidata was not affected by competition at low P levels, but high P fertilization resulted in reduced dry weight of K. pyranidata plants when in competition with A. gerardii. Phenologic separation of growing seasons avoids interspecific competition between these two grasses and may be one mechanism contributing toward their coexistence. Since low temperatures limit mycorrhizal nutrient uptake, phenologic separation of growing seasons could also avoid the competitive advantage of warm-season grasses conferred by their mycorrhizal dependence</p>10atallgrass prairie1 aHetrick, B.A.D.1 aWilson, G.T.1 aHarnett, D.C.  uhttp://knz.lternet.edu/content/relationship-between-mycorrhizal-dependence-and-competitive-ability-two-tallgrass-prairie