Date of Award:

8-2026

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Wildland Resources

Committee Chair(s)

Kari E. Veblen (committee chair), Yong Zhou (committee co-chair)

Committee

Kari E. Veblen

Committee

Yong Zhou

Committee

Peter B. Adler

Abstract

Savannas are unique ecosystems, where trees and grasses live together across the landscape, not quite forming full forests or open grasslands. The ability for trees and grass to coexist is largely the result of widespread disturbances, such as fire. Fire in savannas is largely thought of in how it maintains plants above ground, however, fire also plays a key role in ecosystem and plant processes belowground. First, fire can change how soil nutrients, namely phosphorus, are cycled. Phosphorus is a key nutrient that plants need to function, and plants acquire phosphorus through their roots. Frequent fire can enhance phosphorus availability, which could then alter how plants use their roots to obtain phosphorus. However, there is little known about how savanna grasses are changing their roots in order to acquire phosphorus. 

In this study, I used a long-term fire experiment in Kruger National Park to address how different fire frequencies are altering the availability of phosphorus, and if these changes in available phosphorus change how grasses are using their roots. 

I found that under frequently burned savannas, there were higher amounts of plant available phosphorus than infrequently burned or unburned savannas. However, roots did not respond to the different levels of phosphorus availability. Instead, roots responded to the different fire frequencies, where grasses in frequently burned savannas had more conservative rooting strategies, while grasses in unburned savannas had more acquisitive rooting strategies. This suggests that savanna grass roots do not respond to the availability of phosphorus alone, and that other impacts of fire can influence how grasses change their roots to acquire resources. These findings highlight the need for future belowground studies to consider the broader impacts of fire to accurately predict savanna ecosystem structure.

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