Vegetation and Soil Responses to Fertilization Along the Kalahari Transect
Abstract
To better understand how soil nutrients and soil moisture interactively control vegetation dynamics in savanna ecosystems, a large-scale stable isotope fertilization experiment was conducted using four study sites with different mean annual precipitation (MAP), along the Kalahari Transect (KT). KT in southern Africa traverses a dramatic aridity gradient (from 200 mm to more than 1000 mm MAP, through the Republic of South Africa, Botswana, Namibia and Zambia), on relatively homogenous soils (deep Kalahari sands). The experimental design consisted of a randomized block design with four 21 m x 13 m plots at each site. Each plot was divided into four 10 m x 6 m subplots with a 1 m buffer zone between each subplot. Four treatments (N addition, P addition, N+P addition and control) were randomly applied to the subplots. The N and N+P additions were enriched with 15N to a signature of 10.3 ‰. Grass foliar 15N was significantly higher in the N and N+P addition than in the control or P-addition during following growing season. The differences disappeared in the second growing season. Soil 15N and soil surface CO2 fluxes were not different between treatments in both seasons for all four locations. Herbaceous biomass responses to fertilization were different in different locations. Significantly higher biomass was observed in N+P addition in driest site and in P addition in wetter site. The 15N results provide evidence of N uptake limitation and we also see evidence of productivity limitation. These results suggest that there is a complex feedback between soil and vegetation in savanna ecosystems.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2006
- Bibcode:
- 2006AGUFM.B44A..04W
- Keywords:
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- 0400 BIOGEOSCIENCES;
- 1615 Biogeochemical cycles;
- processes;
- and modeling (0412;
- 0414;
- 0793;
- 4805;
- 1851 Plant ecology (0476)