02232nas a2200217   4500008004100000245007800041210006900119300001200188490000800200520152900208653003901737653001701776653000901793653001001802653001501812653002601827653002201853100001901875700002001894856010001914       2001                        eng d00aDeterminants of C3 forb growth and production in a C4 dominated grassland0 aDeterminants of C3 forb growth and production in a C4 dominated   a93 -1000 v1523 aForbs are the most abundant species within the vascular flora of tallgrass prairie and they make the greatest contribution to biodiversity of all growth forms. However, little is known about the factors that determine their productivity and growth rates. The objective of this study was to assess the controls of forb growth (absolute and relative) and production in tallgrass prairie from a long-term burning experiment at the Konza Prairie in NE Kansas. Over the 14-year study, forbs comprised 9% of the total biomass production on sites with a high fire frequency vs. 29% on the low fire frequency site, with gramminoids accounting for the remainder. Although interannual variations in peak biomass of the grasses was strongly correlated with environmental variables related to water availability, there were no similar relationships for forbs, suggesting that production of forbs and grasses responded to interannual variations in climate in different ways. Multivariate analysis of climatic controls on growth rates of grasses and forbs yielded similar results. Although forbs had low biomass and absolute growth per unit ground area in frequently burned prairie, their relative growth rates were highest in such sites. Thus, it appears that reduced growth rates of individual forbs per se do not limit forb success in annually burned prairie. Instead, direct negative effects of fire on forbs (increased mortality) may be responsible. Determinants of forb growth and productivity in unburned prairie remain unresolved.10aaboveground net primary production10aBiodiversity10afire10aforbs10aGraminoids10aRelative growth rates10atallgrass prairie1 aBriggs, J., M.1 aKnapp, Alan, K.  uhttp://129.130.186.12/content/determinants-c3-forb-growth-and-production-c4-dominated-grassland