Mammalian herbivores reinforce ecological state transitions in the Chihuahuan Desert

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.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Natural Res & Env Sciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2024

Author dc:creator

• Andreoni, Kieran

Contributors dc:contributor

• Schooley, Robert
• Bestelmeyer, Brandon
• Schauber, Eric

• African Oryx
• Cattle
• Desert Rodents
• Dryland Ecology
• Grasslands
• Herbivory
• Lagomorphs
• Landscape Change

Statement dc:rights

• Copyright 2024 Kieran Andreoni

Language dc:language

en, eng

Handle dc:identifier

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

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F124466