Herbivory and Competing Vegetation Interact as Site Limiting Factors in Maritime Forest Restoration

Emily C Thyroff,Owen T Burney,Douglass F Jacobs

doi:10.3390/f10110950

Emily C Thyroff, Owen T Burney + Show 1 more

Open Access

https://doi.org/10.3390/f10110950

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Abstract

Herbivory and competition during the regeneration phase influence forest successional dynamics. We demonstrated the importance of using the Target Plant Concept to identify and overcome site limiting factors for subtropical maritime forest restoration associated with deer browsing and competition. Quercus virginiana Mill. (live oak) bareroot seedlings were planted into clearcuts along the US Southern Atlantic coast with different treatment combinations of herbivory control (fenced or non-fenced) against white-tailed deer (Odocoileus virginianus Zimm.) browsing and competing vegetation removal (none, one-year, or two-years). After three growing seasons, mean seedling survival was 61% with no significant treatment differences. Control of browse and vegetation interacted to facilitate growth of live oak; seedlings were significantly larger for all response parameters (diameter, height, crown width) when fenced and treated with vegetation control. Removal of vegetation improved seedling performance only in fenced plots, however, indicating a shift in pressure from herbivory to competition as the most limiting site factor when deer were excluded. After the second growing season, foliar nitrogen was greater in fenced plots than non-fenced plots and greater in two-year vegetation control subplots than non-vegetation control subplots. This result, however, was absent after the third growing season. Three years after clearcutting, there was no evidence of Q. virginiana natural regeneration in non-fenced plots. Even with artificial regeneration in non-fenced plots, Q. virginiana growth was slow, indicating that herbivory was a key limiting factor. Our findings illustrate the importance of accounting for site limiting factors and may aid in developing management prescriptions to promote semi-evergreen oak regeneration in ecosystems with high pressure from herbivory and competing vegetation.

Highlights

Worldwide, forests are challenged by herbivore behavior, population sizes, and changes in herbivore pressure on forest systems [1]
Overall of vegetation control was different between the fencing treatments and the effects varied over time
Our research provides evidence that restoration of maritime forests through artificial regeneration of a keystone species is possible following clearcutting

Summary

Introduction

Forests are challenged by herbivore behavior, population sizes, and changes in herbivore pressure on forest systems [1]. Herbivory by cervids (i.e., elk, deer, etc.), smaller mammals, and feral grazing animals such as cattle and hogs is a common forest regeneration concern across ecosystems [2,3,4,5,6,7,8]. Reduction of predators, and habitat fragmentation have contributed to high densities of herbivores resulting in over-browsing [1,9]. Browsing preference has potential to change forest dynamics as recruitment composition shifts towards less desired species [4,10,11,12]. When excluding animal browsers from forest regeneration sites, non-desired competing vegetation is protected. A resulting shift toward competing vegetation as a dominant limiting factor suggests

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