Quantifying impacts of white-tailed deer (Odocoileus virginianus Zimmerman) browse using forest inventory and socio-environmental datasets

RESEARCH ARTICLE Quantifying impacts of white-tailed deer (Odocoileus virginianus Zimmerman) browse using forest inventory and socioenvironmental datasets Stephanie R. Patton*, Matthew B. Russell, Marcella A. Windmuller-Campione, Lee E. Frelich a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 Department of Forest Resources, University of Minnesota, St. Paul, Minnesota, United States of America * Abstract OPEN ACCESS Citation: Patton SR, Russell MB, WindmullerCampione MA, Frelich LE (2018) Quantifying impacts of white-tailed deer (Odocoileus virginianus Zimmerman) browse using forest inventory and socio-environmental datasets. PLoS ONE 13(8): e0201334. https://doi.org/10.1371/ journal.pone.0201334 Editor: Marco Apollonio, Universita degli Studi di Sassari, ITALY Received: June 13, 2017 Accepted: July 15, 2018 Published: August 23, 2018 Copyright: © 2018 Patton et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: These are third party data collected by the USDA Forest Service. All USDA Forest Service FIA files are available from the FIA datamart at: (http://www.fia.fs.fed.us/toolsdata/). Census population data available at: (https:// www.census.gov/programs-surveys/popest/data. html). Lyme disease data available through the Centers for Disease Control and Prevention at: (http://www.cdc.gov/lyme/stats/). Deer-vehicle collision reports can be obtained from the Michigan State Police (http://www.mlive.com/news/index. Elevated population levels of white-tailed deer (Odocoileus virginianus Zimmerman) can drastically alter forest ecosystems and negatively impact society through human interactions such as deer vehicle collisions. It is currently difficult to estimate deer populations at multiple scales ranging from stand, county, state, and regional levels. This presents a challenge as natural resource managers develop silvicultural prescriptions and forest management practices aimed at successfully regenerating tree species in the face of deer browsing. This study utilized measurements of deer browse impact from the new tree regeneration indicator developed by the United States Department of Agriculture Forest Service Forest Inventory and Analysis (FIA) program. Seedling and sapling abundance and other plot-level characteristics were analyzed across three states (Michigan, Minnesota, and Wisconsin) in the Great Lakes Region of the United States. Socio-environmental datasets (Lyme disease cases, deer vehicle collisions, and deer density estimates) were used in conjunction with FIA data to determine their predictive power in estimating deer browse impacts by county. Predictions from random forests models indicate that using Lyme disease case reports, the number of deer-vehicle collisions, deer density estimates, and forest inventory information correctly predicted deer browse impact 70–90% of the time. Deer-vehicle collisions per county ranked highly important in the random forests for predicting deer browse impacts in all three states. Lyme disease cases ranked high in importance for the Lake States combined and for Minnesota and Wisconsin, separately. Results show the effectiveness of predicting deer browse impacts using a suite of freely available forest inventory and other socio-environmental information. Introduction Selective browsing by white-tailed deer (Odocoileus virginianus Zimmerman) can have dramatic direct and indirect effects on forest ecosystems, including changes in the food web, PLOS ONE | https://doi.org/10.1371/journal.pone.0201334 August 23, 2018 1 / 16 Quantification and impacts of white-tailed deer browse in the Lake States, USA ssf/2013/10/database_see_where_in_michigan. html), Minnesota Department of Public Safety (https://dps.mn.gov/divisions/ots/reportsstatistics/Pages/Fact-sheets.aspx), and Wisconsin Department of Transportation (http://wisconsindot. gov/Pages/safety/education/crash-data/crashfacts. aspx). Quality Deer Management Association deer density data available from the Data Repository for the University of Minnesota at: (http://dx.doi.org/ 10.13020/D6G014). All data are open source and others would be able to access these data in the same manner as the authors (i.e. the authors did not have any special access privileges that others would not have to the data). Funding: This work was supported by the Minnesota Agricultural Experiment Station (www. maes.umn.edu, projects MIN-42-063 and MIN-42068) and the University of Minnesota Office of the Vice President for Research (www.research.umn. edu, Grant-in-Aid #23024). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing interests: The authors have declared that no competing interests exist. vegetation structure, and nutrient cycling [1,2]. White-tailed deer consume buds and twigs of young trees as well as many understory herbaceous plants. Once the terminal leader of a tree grows above the reach of deer, impacts from browsing are significantly reduced–thus, seedlings and saplings are the most vulnerable to damage [3–5]. Ungulate browsing of select species for numerous years can greatly change forest species composition and diversity [2,6], depending on abundance of browse tolerant species (e.g. increased diversity [7,8]; decreased diversity [4,9,10]). In more extreme cases, deer alter forested ecosystems such that they exist in a different stable state. These studies depict a landscape typically more similar to grasslands and inhospitable for seedling establishment [11,12]. Understanding deer browse impact on forest structure and composition is critical to predicting the resiliency and productivity of forests in the long term [13]. Deer present additional challenges to forested communities across the eastern US via indirect effects. In a Pennsylvania exclosure study, deer promoted the success of two invasive species–garlic mustard (Alliaria petiolata ((M. Bieb.) Cavara & Grande)) and Asian stiltgrass (Microstegium vimineum (Trin.) A. Camus)–and reduced the success of native plants via selective browsing [14]. The community-wide effects can also be seen further up the trophic cascade. Shrub nesting birds decline in richness and abundance when deer densities exceed eight per square kilometer in Pennsylvania [15]. In oak forests, competition for acorn mast caused a reduction in small mammal populations [16,17]. High deer browse effects also extend beyond the forest ecosystem. Over time, loss of palatable tree species and proliferation of nonpalatable species potentially affects timber markets when merchantable species are affected [3,18]. Estimating deer densities and browse impacts are challenging at broad scales. One of the ways in which browse pressure might be predicted is with (...truncated)