October 13, 2022
Ed February to present Division of Biology Seminar
Submitted by Division of Biology
Ed February, emeritus associate professor at the University of Cape Town, will present "Tree Survival Among Grasses in Savanna" as part of the Division of Biology Seminar Series at 3:30 p.m. Monday, Oct. 17, in Ackert Hall 221.
Tropical savannas are comprised primarily of an overstory of trees with an herbaceous C3 understory. In these systems, rainfall is distinctly seasonal with a cool dry season of approximately eight months followed by a hot wet season. In most savannas, soils are nutrient-poor and often limited in both nitrogen and phosphorous. There have been several hypotheses explaining how woody plants avoid competing with grasses for resources. These hypotheses may be divided into either resource‐based or disturbance‐based hypotheses. Resource‐based hypotheses propose that, in semi‐arid savannas, woody plants and grasses utilize different soil horizons for resources: grasses use surface soil horizons, while woody plants obtain their resources from deeper down.
Disturbance‐based hypotheses, however, argue that woody plants seldom out‐compete grasses and, when they do, they are prevented from reaching maturity because of disturbances such as fire and herbivory. These hypotheses do not however acknowledge the low nutrient status of savanna soils rather, suggesting that water is the critical niche axis, with resource‐based models invoking root niche partitioning for water, while disturbance‐based hypotheses proposing that woody plants will only grow fast enough to escape fire or herbivory, and reach maturity, if sufficient water is available. February proposes that rather than water, it is differences in nutrient uptake and use between woody plants and grasses that are an important, but poorly appreciated, mechanism contributing to woody–grass dynamics in savannas.
If you would like to visit with February, please contact Jesse Nippert at firstname.lastname@example.org.