Social and ecological dimensions of non-native grass management in working landscapes

Many grasslands are working landscapes, defined as environments where economic productivity has the potential to coexist with other ecosystem services, including biodiversity. However, biodi-versity in working grasslands is threatened by the dominance of non-native grasses used as cattle forage. Although controlling non-native grasses using herbicide or intensive grazing is sometimes assumed to improve habitat, it is unclear how this control impacts grassland birds or their arthro-pod prey, both taxa of conservation concern. Furthermore, devising outreach strategies to support conservation on private land through non-native grass control is challenged by the lack of research exists on landowner willingness to control these economically valuable grasses. To address these unknowns, I have studied the social and ecological dimensions of non-native grass management. Chapter 1 of my dissertation provides a review covering non-native grass history, prevalence, and ecosystem services and disservices. I follow this review with three studies conducted in the Grand River Grasslands of southern Iowa and northern Missouri, a region in the Great Plains where non-native grasses are widespread on both nature reserves and private lands. Chapter 2 and 3 are ecological studies conducted in the context of a landscape-scale exper-iment, with treatments including herbicide, native seeding, and grazing. In Chapter 2, I monitored grassland birds and arthropods on 18 sites (2015-2018). I found that controlling non-native grass-es with herbicide was linked to decreased abundance in the first year after treatment for a few bird species, but increased abundance for multiple birds and arthropod orders after several years. Com-bining herbicide with intensive grazing produced increased abundance of dickcissels (Spiza ameri-cana) and decreased abundance of Henslow’s sparrows (Centronyx henslowii) and bobolinks (Dolichonyx oryzivorus), indicating that combining these treatments creates trade-offs for disturb-ance-sensitive species, potentially through reduced cover of native plants. Herbicide alone may make grasslands more attractive to some birds one or two years after the initial disturbance. In Chapter 3, I explored the breeding ecology of dickcissels in 2016 on a subset of the sites from Chapter 2 (n=4) to determine if increased abundance corresponded to higher reproductive success or increased prey abundance. I found no effects of herbicide treatments on nestling condition or arthropods provisioned to nestlings, but I did observe increases in fledgling production and nest abundance on patches sprayed with herbicide. These results indicate that, for dickcissels, herbicide and native seeding increased reproductive success, although dickcissels tended to avoid nesting in intensively grazed areas. In Chapter 4, I assessed the possibilities for management on the private lands that constitute more than 80% of the Grand River Grasslands. Using complementary frameworks, the Theory of Planned Behavior and Norm Activation Model, I examined factors influencing landowner willing-ness to manage non-native gasses. Based on a mixed-mode survey implemented in 2017 (n=456; 32.7% response rate), positive attitudes toward management and increased social norm pressures were associated with increased sentiments of moral responsibility to reduce non-native grasses. These personal norms, together with attitudes, positively influenced willingness to implement man-agement. The power of norms to explain decisions suggests that people could be engaged in man-agement by leveraging moral responsibility and influential social groups. Taken together, these results suggest that 1) controlling non-native grasses is beneficial to many grassland birds and their arthropod prey in the long term, although there are short-term trade-offs, and 2) there are untapped opportunities to engage landowners in restoration of grasslands in-vaded by introduced grasses. Targeted landowner outreach holds potential to increase the long-term biodiversity value of pastures overtaken by non-native grasses, but careful application of manage-ment is necessary to ensure desired outcomes for grassland birds.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Natural Res & Env Sciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2020

Author dc:creator

• Coon, Jaime J.

Contributors dc:contributor

• Miller, James R.
• Schooley, Robert
• van Riper, Carena J.
• Benson, Thomas J.

• grasslands
• grassland birds
• tall fescue
• grassland management
• arthropods
• conservation social science
• rangeland social science
• environmental management

Statement dc:rights

• Copyright 2020 Jaime Coon

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/108586

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/108586