Quantifying Impacts of Deer Browsing and Mitigation Efforts on Hardwood Forest Regeneration

Caleb H Redick, Purdue University

Abstract

1.1 Temperate hardwood forests in the eastern United States Temperate hardwood forests provide food and habitat for wildlife as well as valuable wood products. These forests contain a wide diversity of species, with some of the most important ecological and commercial species including oaks, hickories, cherries, and walnuts. Oaks, in particular, are a foundational species for many temperate forest types, which grow in dry and mesic environments (van de Gevel et al., 2012). In the Midwestern USA, oak-hickory forests are the most prominent forest type, making up to 71% of Indiana forests (Gormanson and Kurtz, 2017). Northern red oak and white oak are important timber species in the eastern USA. Black cherry is a minor component of many northern hardwood forest types and has valuable wood (Burns and Honkala, 1990). 1.2 Limiting factors to hardwood regeneration Oak forests across the eastern USA are shifting to a mixed mesophytic species composition dominated by maples and beeches (Acer-Fagus) (van de Gevel et al., 2012; Hart et al., 2008). A combination of factors has led to decline of oak and hickory regeneration in the Midwest, including reduced frequency of fire, changes in harvest practices, and herbivory by white-tailed deer (Odocoileus virginianus) (Csigi and Holzmueller, 2015; McEwan et al., 2011). The decline of oak is present in other countries as well, including Sweden and Japan (Petersson et al., 2019; Takatsuki, 2009). Disturbances that create canopy openings and reduce competition release light resources for the understory and benefit regeneration of fire-tolerant and moderately shade-tolerant and intolerant species. For example, oaks and American chestnuts both historically relied on disturbances such as wind or ice storms to create canopy gaps (van de Gevel et al., 2012). A lack of surface fires and single-tree selection harvesting practices have both contributed to the establishment of understory sugar maple and American beech, which are late-successional shadetolerant species (Holzmueller et al., 2011). Even disturbance is reintroduced, however, invasive plants and deer herbivory present additional challenges to temperate forest regeneration and management. 1.3 The threat of damage by deer Animal herbivory, resulting from high populations of native ungulates or novel introductions of deer, goats, or cattle, poses a problem in forest regeneration globally (Kuijper et al., 2010; Petersson et al., 2019; Takatsuki, 2009; Whitaker, 2009). Silvicultural techniques that produce small clearcuts and sharp forest edges create attractive habitat for herbivores, but often lead to a concentration of food resources insufficient to satiate the animals without resorting to woody seedlings (Reimoser and Gossow, 1996). For example, in southern Sweden, an increase in deer and moose populations and a concomitant increase in basal area (due to changes in harvesting practices) have caused a regional decline in oak sapling density (Petersson et al., 2019). Similarly, in Japan increasing Sitka deer populations threaten to change plant communities (Takatsuki, 2009). In the eastern USA, reduced hunting pressure, loss of predators, and the adaptability of deer to anthropogenic landscapes and structures have contributed to an increase in white-tailed deer populations (Whitaker, 2009). Deer herbivory stunts tree growth, hindering seedlings from growing into the overstory and allowing herbaceous species to overtop them (McKenna and Woeste, 2004; Putman and Moore, 1998; Webster et al., 2008). In addition, browsing of terminal buds reduces the quality of timber by encouraging trees to grow multiple leaders, which lead to split, crooked trunks (McKenna and Woeste, 2004).

Degree

M.Sc.

Advisors

Jacobs, Purdue University.

Subject Area

Agronomy|Ecology|Forestry|Wood sciences

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