For more than a decade, we have compared responses of mesic (subhumid) savanna grasslands (>500 mm MAP in the tropics and >600 mm MAP outside the tropics) in North America and South Africa to alterations in both fire and grazing regimes. The long-term, comparative experiment that forms the centerpiece of this cross-continental research program is located in tallgrass prairie at the Konza Prairie Biological Station (Kansas, USA) and in knob-thorn marula savanna at the Kruger National Park (Limpopo and Mpumalanga provinces, South Africa). We refer to this study as the Konza-Kruger (K-K) Experiment. At both sites, we have been manipulating grazing by removing all large herbivores (>5 kg) from research plots with permanent exclosures (each with a paired plot that grazers can freely access). These exclosures were established in replicated fire frequency experiments ongoing at each site (treatments range from >25-50 yrs of annual burning, burning every 3-4 yrs, or complete fire exclusion).
Compare mesic grassland responses to alterations in fire and grazing regimes in tallgrass prairie of North America and knobthorn-marula savanna in South Africa.
Location of Sampling Stations (watershed name, or map with grid locations): N1B, N4B, N4D, N20B.
Frequency of Sampling: From 2006-2013, annually (ANPP) and twice per growing season (plant species composition). From 2018 onward, every 5 years.
Variable Measured: ANPP, plant species composition.
Field Methods: Core Experimental Design. To manipulate the presence of large herbivores, we established replicate, 38.5/m2 (7m diameter circular) herbivore exclosures prior to the growing season in 2005/06 in unburned, intermediate burned (3 or 4 years), and annually burned areas at both Konza and Kruger. We established three blocks of seven exclosures with co-located paired plots open to grazing in each of the three fire treatments (n = 21 exclosures/treatment/site).
Vegetation Sampling Methods: Each year, we survey herbaceous plant community structure at the beginning and end of the growing season (Konza: June and August; Kruger:January and March) to capture peak abundance of early and late-season species, respectively. We sample vegetation in a permanent 2 x 2 m plot located within each of the full exclosures, partial exclosures, and paired plots. The 4 m2 plot is divided into four 1m2 subplots, and within each subplot, we estimate percent cover (to the nearest 1%) for each species rooted inside. We also sample herbaceous plant biomass in two ways. First, we measure ANPP each year at the end of the growing season inside each full exclosure by clipping all aboveground biomass in three 0.1 m2 quadrats. Clipped biomass is separated into grass, forb, woody, and previous year’s dead.