Assessing colonization and extirpation trends of Illinois understory herbaceous plants using robust-design occupancy models

Janssen, Eric Daniel

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https://hdl.handle.net/2142/116059 Copy

Description

Title

Assessing colonization and extirpation trends of Illinois understory herbaceous plants using robust-design occupancy models

Author(s)

Janssen, Eric Daniel

Issue Date

2022-07-10

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

• Molano-Flores, Brenda
• Zaya, David N

Committee Member(s)

• Matthews, Jeffrey
• Benson, Thomas J
• Spyreas, Greg

Department of Study

Natural Res & Env Sci

Discipline

Natural Resources and Environmental Sciences

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• robust-design occupancy models
• colonization
• extirpation
• forests
• Illinois
• plants

Abstract

Midwestern temperate forests are often small and isolated because of human disturbance. Plant species present in these forests are vulnerable to extirpation, with many landscape, site, and species characteristics influencing a species’ ability to persist in this hostile landscape. I used robust-design occupancy models to assess the role these three factors have in the occupancy, colonization, and extirpation probabilities of Illinois forest plants. Occupancy models create unbiased estimates for these probabilities by incorporating detection probability in the estimates, which has historically been overlooked in plant research. Species presences were gathered from multiple surveys of 124 sites (84 uplands, 40 floodplains) across Illinois from 1998-2017. The occupancy models created estimates for over 90% of the 426 unique species studied. Occupancy and colonization estimates were higher compared to naïve estimates, while extirpation estimates were lower. Landscape-level factors (e.g. surrounding forest and agriculture cover) influenced occupancy, colonization, and extirpation probabilities for the most species. At the site-level, species richness and mean coefficient of conservatism (mean C) influenced these parameters for the most species. For species-level characteristics, coefficient of conservatism, wetland plant indicator status, and life cycle had a significant relationship with colonization or extirpation probability. No dispersal syndromes had a significant relationship with any of the probability estimates. Occupancy, colonization, and extirpation probabilities did not differ between upland and floodplain forests. Overall, robust-design occupancy models work best for calculating probability estimates when species are present in ~11% of sites and are found in a greater number of sampling units (quadrats). Lastly, colonization probabilities were low for many species and were often lower than extirpation probabilities, which suggests decreasing species richness in these communities.

Graduation Semester

2022-08

Type of Resource

Thesis

Copyright and License Information

Copyright 2022 Eric Janssen

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