02392nas a2200205 4500008004100000245011200041210006900153260004800222300001000270490001400280520168300294653000901977653000901986653001501995653001202010653001302022653001302035100001302048856012502061 2009 eng d00aControls of aboveground net primary production in mesic savanna grasslands: An inter-hemispheric comparison0 aControls of aboveground net primary production in mesic savanna  aFort Collins, CObColorado State University a1 -500 vMS Thesis3 a

Patterns and controls of annual aboveground net primary productivity (ANPP) are fundamental metrics of ecosystem functioning. It is generally assumed, but rarely tested, that determinants of ANPP in one region within a biome will operate similarly throughout that biome, as long as physiognomy and climate are broadly consistent. We tested this assumption by quantifying ANPP responses to fire, grazing history, and nitrogen (N) addition in North American (NA) and South African (SA) savanna grasslands. We found that total ANPP responded in generally consistent ways to fire, grazing history, and N addition on both continents. Annual fire in both NA and SA consistently stimulated total ANPP (28–100%) relative to unburned treatments at sites with deep soils, and had no effect on ANPP in sites with shallow soils. Fire did not affect total ANPP in sites with a recent history of grazing, regardless of whether a single or a diverse suite of large herbivores was present. N addition interacted strongly and consistently with fire regime in both NA and SA. In annually burned sites that were not grazed, total ANPP was stimulated by N addition (29–39%), but there was no effect of N fertilization in the absence of fire. In contrast, responses in forb ANPP to fire and grazing were somewhat divergent across this biome. Annual fire in NA reduced forb ANPP, whereas grazing increased forb ANPP, but neither response was evident in SA. Thus, despite a consistent response in total ANPP, divergent responses in forb ANPP suggest that other aspects of community structure and ecosystem functioning differ in important ways between these mesic savanna grasslands.

10aANPP10afire10aGrasslands10aGrazing10anitrogen10aSavannas1 aBuis, G. uhttp://lter.konza.ksu.edu/content/controls-aboveground-net-primary-production-mesic-savanna-grasslands-inter-hemispheric02607nas a2200325 4500008004100000245011200041210006900153300001300222490000700235520168300242653000901925653000901934653001501943653001201958653001301970653001301983100001501996700002002011700002002031700001602051700002202067700001602089700002402105700001702129700001702146700001602163700001602179700002002195856006602215 2009 eng d00aControls of aboveground net primary production in mesic savanna grasslands: An inter-hemispheric comparison0 aControls of aboveground net primary production in mesic savanna  a982 -9950 v123 a

Patterns and controls of annual aboveground net primary productivity (ANPP) are fundamental metrics of ecosystem functioning. It is generally assumed, but rarely tested, that determinants of ANPP in one region within a biome will operate similarly throughout that biome, as long as physiognomy and climate are broadly consistent. We tested this assumption by quantifying ANPP responses to fire, grazing history, and nitrogen (N) addition in North American (NA) and South African (SA) savanna grasslands. We found that total ANPP responded in generally consistent ways to fire, grazing history, and N addition on both continents. Annual fire in both NA and SA consistently stimulated total ANPP (28–100%) relative to unburned treatments at sites with deep soils, and had no effect on ANPP in sites with shallow soils. Fire did not affect total ANPP in sites with a recent history of grazing, regardless of whether a single or a diverse suite of large herbivores was present. N addition interacted strongly and consistently with fire regime in both NA and SA. In annually burned sites that were not grazed, total ANPP was stimulated by N addition (29–39%), but there was no effect of N fertilization in the absence of fire. In contrast, responses in forb ANPP to fire and grazing were somewhat divergent across this biome. Annual fire in NA reduced forb ANPP, whereas grazing increased forb ANPP, but neither response was evident in SA. Thus, despite a consistent response in total ANPP, divergent responses in forb ANPP suggest that other aspects of community structure and ecosystem functioning differ in important ways between these mesic savanna grasslands.

10aANPP10afire10aGrasslands10aGrazing10anitrogen10aSavannas1 aBuis, G.M.1 aBlair, John, M.1 aBurkepile, D.E.1 aBurns, C.E.1 aChamberlain, A.J.1 aChapman, P.1 aCollins, Scott., L.1 aFynn, R.W.S.1 aGovender, N.1 aKirkman, K.1 aSmith, M.D.1 aKnapp, Alan, K. uhttps://link.springer.com/article/10.1007%2Fs10021-009-9273-101851nas a2200205 4500008004100000245010700041210006900148300001000217490000700227520115400234653000901388653001201397653001601409653002201425653001301447100001901460700002201479700001701501856012701518 2004 eng d00aFire effects on mycorrhizal symbiosis and root system architecture in southern African savanna grasses0 aFire effects on mycorrhizal symbiosis and root system architectu a1 -100 v423 aMycorrhizal symbiosis is a key factor influencing aspects of grassland and savanna structure and functioning including plant growth, competition, population and community dynamics, and responses to fire and herbivory. This study assessed the effects of fire on mycorrhizal symbiosis and root system architecture (RSA) in South African savanna grasses. Eighteen grass species were sampled across contrasting fire frequency treatments in the Kruger National Park experimental burn plots. All eighteen species studied were highly colonized by arbuscular mycorrhizal fungi (AMF). Both mycorrhizal symbiosis and RSA were strongly affected by fire, with an increase in AMF colonization and a decrease in root branching and fine root development with decreasing fire frequency. Greater water limitation in frequently burned savanna may result in greater fine root development, thus reducing plant dependency on AMF for acquisition of soil resources. Reduced mycorrhizal colonization in frequently burned savanna may also be driven by higher phosphorus : nitrogen ratios, or indirect effects related to higher grazing intensities in frequently burned sites.10afire10aGrasses10amycorrhizas10aroot architecture10aSavannas1 aHartnett, D.C.1 aPotgieter, A.L.F.1 aWilson, G.T. uhttp://lter.konza.ksu.edu/content/fire-effects-mycorrhizal-symbiosis-and-root-system-architecture-southern-african-savanna03998nas a2200205 4500008004100000245009000041210006900131260003700200300001000237520329300247653002303540653002203563653000903585653001303594100002103607700001903628700001903647700001703666856010903683 2002 eng d00aFire behaviour as a key factor in the fire ecology of African grasslands and savannas0 aFire behaviour as a key factor in the fire ecology of African gr bMillpress, Rotterdam Netherlands a204 -3 a

The effect of fire on natural ecosystems involves the response of living organisms to the release of heat energy through the combustion of plant material. The manner in which and the factors that influence the release of heat energy, involves the study of fire behaviour. In Africa there is a serious deficiency of knowledge concerning the behaviour of fires and this is particularly applicable to the savanna and grassland areas of the continent. Virtually no attempt has been made to quantify the dynamics of the release of heat energy during a fire and the subsequent response of plants to it. The determination of such relationships helps explain many of the apparently inexplicable effects of fire that are often cited in the literature. Research on the effects of fire has been conducted throughout the grassland and savanna areas of Africa, particularly in southern Africa, since the early period of the 20th century. An interesting feature about these early investigations and subsequent research up until 1971, was that it focused on the effects of season and frequency of burning on the forage production potential of the grass sward and the ratio of bush to grass in savanna areas However, in 1971 a conference was convened in the United States of America in Florida, by the Tall Timbers Research Station on the theme of "Fire in Africa". The major benefit that accrued from this conference was the realization that in Africa the study of fire behaviour and its effects on the ecosystem, as described by type and intensity of fire, had been largely ignored in all the fire research that had been conducted up until that time. As a consequence a research program was initiated in South Africa and later extended to East Africa, to characterise the behaviour of fires burning in savanna and grassland vegetation and determine the effect of type and intensity of fire on the vegetation. The overall effect of type of fire is that surface head fires and crown fires have the least effect on grasses and have the potential to have the greatest effect on trees. This is because the heat is released above ground level away from the growing points of the grasses and closest to the growing points of the trees. Conversely, surface back fires have the opposite effect on grass and tree vegetation. This is because the heat is released close to ground level where the growing points of grasses are located and away from the growing points of the trees in the canopy. The overall effect of fire intensity is that grasses are generally not sensitive to increasing fire intensities because their growing points are located close to ground level away from the release of heat energy. Conversely trees are sensitive to increasing fire intensities because their growing points are generally exposed to the release of heat energy in the canopy of the trees. These effects explain why intense fires favour the development of grassland and open savannas and vice versa. The behaviour of surface head and back fires is currently being compared in southern African savannas and tall grass prairies in North America and results indicate that fires burning in grass dominated communities behave similarly and may therefore have similar effects on grass and tree vegetation globally.

10aAfrican grasslands10aAmerican prairies10afire10aSavannas1 aTrollope, W.S.W.1 aTrollope, L.A.1 aHartnett, D.C.1 aViegas, D.X. uhttp://lter.konza.ksu.edu/content/fire-behaviour-key-factor-fire-ecology-african-grasslands-and-savannas