Date of Award:

5-2016

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Ecology

Advisor/Chair:

Andrew Kulmatiski

Abstract

As the atmosphere warms, precipitation events are likely to become less frequent but more intense. While extensive efforts have been made to understand how changes in mean annual precipitation will affect plant growth, particularly in semi-arid systems, relatively little is known about how increasing precipitation intensity will affect plant growth and hydrologic cycles. A recent study by Kulmatiski and Beard (2013) found that small increases in precipitation intensity increased woody plant growth and decreased grass growth in a three-year experiment in a savanna system, Kruger National Park. Here we report results from the following two years of that experiment. Due to naturally large precipitation events, plant available water was similar between treatment and control plots in the last two years of the study allowing us to test woody plant and grass responses to treatment removal (i.e., legacy effects). Treatment effects on grass and tree growth disappeared within months of treatment removal. However, due to a legacy effect of treatments, tree mass was greater in treatment that control plots at the end of the experiment. Measurements of root recruitment and hydrological tracer uptake, but not root volume helped explain plant growth responses to treatments. Results suggest that savanna plants respond rapidly to changes in precipitation intensity, but because of legacy effects, occasional increases in precipitation intensity can result in long-term shrub encroachment.

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