PARENT SESSION
Poster Session 39: Late Breaking and Newsworthy Posters
Friday, August 12, 8:30 AM - 10:30 AM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
How does rainfall effect tree and grass growth? A report on rainfall manipulation experiments in the Kruger National Park, South Africa.
Rademan, Louise*,1, Bond, William1, February, Edmund1, Higgins, Steve2, 1 Department of Botany, Cape Town, South Africa2 Chair of Vegetation Ecology, Munich, Germany
ABSTRACT- The mechanisms behind the co-existence of trees and grasses are a central question in savanna ecology. Our research, based in the Kruger National Park, South Africa, aims to evaluate hypotheses that explain grass -tree co-existence. Medium-term rainfall and competition experiments replicated across a soil template and rainfall gradient have been set up using rain-out shelters and irrigation plots. Data on above ground tree and grass biomass production and below ground changes in soil moisture have been recorded for two growing seasons. The data show a decrease in grass standing crop with a decrease in rainfall amount at both sites but an increase in standing crop with an increase in rainfall at the high rainfall site. Manipulations that reduced rainfall have also resulted in a reductions in herbaceous basal cover at both sites. In addition, both sites have less grass standing crop in plots where woody plants are present. Rainfall manipulation has not greatly affected woody plant growth rate at either site. However, the removal of grasses has resulted in a large increase in woody plant basal area at Pretoriuskop, and taller woody plants at Satara. From this, we conclude that trees do not appear to be water limited whereas grasses do appear to be. In addition, there is a competitive effect between trees and grasses with each life form growing more successfully in the absence of the other.
Key words: savanna, rainfall, tree-grass, co-existence