Term of Award

Spring 2019

Degree Name

Master of Science in Biology (M.S.)

Document Type and Release Option

Thesis (open access)

Copyright Statement / License for Reuse

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

Department

Department of Biology

Committee Chair

Kerrie Sendall

Committee Member 1

John Schenk

Committee Member 2

Lissa Leege

Abstract

Climate change is altering ecosystems on a global scale, creating novel ecological scenarios with which plant species must cope. Factors such as altered precipitation and fire regimes and non-native plant invasion may negatively affect native plant species, while interactions between these stressors could magnify their impacts. The complexity of multiple stressors and the effects they have on native pine seedlings are difficult to predict without evaluating their combinations in field experiments. In a multi-year study, I investigated the effects of drought and plant invasion on three southeastern pine species under pre and post-fire conditions. We planted longleaf (Pinus palustris), loblolly (P. taeda), and slash (P. elliottii) pine into a factorial common garden experiment with the following treatment combinations: (1) native vegetation, ambient precipitation; (2) grass invasion by cogongrass (Imperata cylindrica), ambient precipitation; (3) native vegetation, drought simulated by rain out shelters; (4) grass invasion, drought. I measured growth and physiological traits of the native pine seedlings to quantify differences between treatments and species as well as pre- and post-fire differences. I found that under both pre and post-fire, drought alone was the most debilitating stressor physiologically for pine seedlings in comparison to grass invasion and the combination of drought and grass invasion, leading to decreased growth and survival. Grass invasion negatively affected seedling physiology and survival; however, in the pre-fire growing season the addition of the grass invader to drought treatments alleviated some of the physiological stress caused by unusually low seasonal rates of precipitation. Grass invasion also alleviated physiological drought stress of pine seedlings to some degree in the post-fire growing season, but I also found that the combination of grass invasion and drought resulted in significantly lower rates of seedling survival. Interactions between these stressors are thus very complex and may require unique management techniques under future climate conditions. This field experiment indicates that careful site selection will be necessary when establishing new pine plantations or restoring longleaf pine habitat, to avoid drought, plant invasion by cogongrass, and most importantly the combination of the two.

OCLC Number

1104328792

Research Data and Supplementary Material

No

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