00665nas a2200217   4500008004100000245006500041210006500106300001400171490000800185653003900193653001900232653001400251653000900265653001400274653001800288653002100306100002300327700002100350700002000371856005600391       2021                        eng d00aFire history as a key determinant of grassland soil CO2 flux0 aFire history as a key determinant of grassland soil CO2 flux  a579–5920 v46010aaboveground net primary production10acarbon cycling10aecosystem10afire10agrassland10asoil CO2 flux10asoil respiration1 aSlette, Ingrid, J.1 aLiebert, Alannah1 aKnapp, Alan, K.  uhttp://link.springer.com/10.1007/s11104-020-04781-003337nas a2200349   4500008004100000245011600041210006900157300001300226490000600239520233700245653003902582653000902621653001002630653001502640653001202655100002002667700001702687700002002704700001302724700002002737700002202757700002402779700001702803700001802820700001602838700001402854700001702868700001702885700001602902700001302918856005602931       2012                        eng d00aA test of two mechanisms proposed to optimize grassland aboveground primary productivity in response to grazing0 atest of two mechanisms proposed to optimize grassland abovegroun  a357 -3650 v53 a<p>Aims Mesic grasslands have a long evolutionary history of grazing by large herbivores and as a consequence, grassland species have numerous adaptations allowing them to respond favourably to grazing. Although empirical evidence has been equivocal, theory predicts that such adaptations combined with alterations in resources can lead to grazing-induced overcompensation in aboveground net primary production (ANPP; grazed ANPP &gt; ungrazed ANPP) under certain conditions. We tested two specific predictions from theory. First, overcompensation is more likely to occur in annually burned grasslands because limiting nutrients that would be lost with frequent fires are recycled through grazers and stimulate ANPP. Second, overcompensation of biomass lost to grazers is more likely to occur in unburned sites where grazing has the greatest effect on increasing light availability through alterations in canopy structure. Methods We tested these nutrient versus light-based predictions in grazed grasslands that had been annually burned or protected from fire for &gt;20 years. We assessed responses in ANPP to grazing by large ungulates using both permanent and moveable grazing exclosures (252 exclosures from which biomass was harvested from 3192 quadrats) in a 2-year study. Study sites were located at the Konza Prairie Biological Station (KPBS) in North America and at Kruger National Park (KNP) in South Africa. At KPBS, sites were grazed by North American bison whereas in KNP sites were grazed either by a diverse suite of herbivores (e.g. blue wildebeest, Burchell&rsquo;s zebra, African buffalo) or by a single large ungulate (African buffalo). Important Findings We found no evidence for overcompensation in either burned or unburned sites, regardless of grazer type. Thus, there was no support for either mechanism leading to overcompensation. Instead, complete compensation of total biomass lost to grazers was the most common response characterizing grazing&ndash;ANPP relationships with, in some cases, undercompensation of grass ANPP being offset by increased ANPP of forbs likely due to competitive release. The capability of these very different grass-dominated systems to maintain ANPP while being grazed has important implications for energy flow, ecosystem function and the trophic dynamics of grasslands.</p>10aaboveground net primary production10afire10aforbs10aherbivores10asavanna1 aKnapp, Alan, K.1 aHoover, D.L.1 aBlair, John, M.1 aBuis, G.1 aBurkepile, D.E.1 aChamberlain, A.J.1 aCollins, Scott., L.1 aFynn, R.W.S.1 aKirkman, K.P.1 aSmith, M.D.1 aBlake, D.1 aGovender, N.1 aO’Neal, P.1 aSchreck, T.1 aZinn, A.  uhttps://academic.oup.com/jpe/article/5/4/357/90869502233nas a2200217   4500008004100000245007800041210006900119300001200188490000800200520152900208653003901737653001701776653000901793653001001802653001501812653002601827653002201853100001901875700002001894856010101914       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://knz.lternet.edu/content/determinants-c3-forb-growth-and-production-c4-dominated-grassland