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

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.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Natural Resources and Environmental Sciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2022

Author dc:creator

• Janssen, Eric Daniel

Contributors dc:contributor

• Molano-Flores, Brenda
• Zaya, David N
• Matthews, Jeffrey
• Benson, Thomas J
• Spyreas, Greg

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

Statement dc:rights

• Copyright 2022 Eric Janssen

Language dc:language

en, eng

Handle dc:identifier

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

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F116059