Mammalian herbivores reinforce ecological state transitions in the Chihuahuan Desert

Andreoni, Kieran

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https://hdl.handle.net/2142/124466 Copy

Description

Title

Mammalian herbivores reinforce ecological state transitions in the Chihuahuan Desert

Author(s)

Andreoni, Kieran

Issue Date

2024-05-03

Director of Research (if dissertation) or Advisor (if thesis)

Schooley, Robert

Committee Member(s)

• Bestelmeyer, Brandon
• Schauber, Eric

Department of Study

Natural Res & Env Sci

Discipline

Natural Res & Env Sciences

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• African oryx
• Cattle
• Desert rodents
• Dryland ecology
• Grasslands
• Herbivory
• Lagomorphs
• Landscape change

Abstract

Woody plant encroachment is a main driver of landscape change in drylands globally. In the Chihuahuan Desert, past livestock overgrazing interacted with prolonged drought to convert vast expanses of black grama (Bouteloua eriopoda) grasslands to honey mesquite (Prosopis glandulosa) shrublands. Such ecosystem state transitions have greatly reduced habitat for grassland wildlife species, increased soil erosion, and inhibited the delivery of ecosystem services to local communities. The potential for wild herbivores to trigger or reinforce shrubland states may be underappreciated, however, and few studies compare herbivory effects across multiple consumer taxa. Here, I address the roles of multiple mammalian herbivores in driving or reinforcing landscape change in the Chihuahuan Desert by examining their effects on plant communities over multiple spatial and temporal scales, as well as across plant life stages. Moreover, I studied these herbivore effects in the context of precipitation pulses, long-term climate influences, competitive interactions, and habitat structure. I used two long-term studies that hierarchically excluded herbivores by body size over 25 years (Herbivore Exclosure Study) and 21 years (Ecotone Study), and a perennial grass seedling herbivory experiment. Native rodents and lagomorphs were especially important in determining grass cover and plant community composition in wet periods and affected perennial grass persistence over multiple life stages. Conversely, during drought, climate drove declines in perennial grass cover, promoting shrub expansion across the landscape. In that shrub-encroached state, native small mammals reinforced grass loss in part because habitat structure provided cover from predators. This research advances our understanding of an underappreciated component of ecosystem change in drylands – small mammal herbivory – and highlights the need to incorporate positive feedbacks from native small mammals into conceptual models of grassland-shrubland transitions.

Graduation Semester

2024-05

Type of Resource

Thesis

Copyright and License Information

Copyright 2024 Kieran Andreoni

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