Using Deer Fencing And Herbicides To Ensure Hardwood Regeneration In Northern New York State

Eugene Nichols

INTRODUCTION
The regeneration of desirable hardwoods including sugar maple (Acer saccharum), black cherry (Prunus serotina) and white ash (Fraxinus americana) is an important aspect for long-term timber production. To encourage regeneration of valuable hardwoods, many forest managers in the northeast have used shelterwood systems instead of clear cuts. Shelterwood cuts favor regeneration of valuable hardwoods over other species because they leave healthy, reliable seed trees and appropriate lighting conditions. However, in many parts of northwestern New York the establishment of hardwood regeneration, even under a shelterwood system, is not happening as predicted. Competing vegetation, particularly that of Rubus spp., hayscented fern (Dennstaedtia punctilobula), goldenrods (Solidago spp.), grasses and sedges. These early successional plants dominate the understories of the shelterwood cuts and block out direct sunlight to the growing seedlings. The saplings that make it above the herbaceous ground cover are often severely browsed by white-tailed deer (Odecoilius virginianus). White-tailed deer typically prefer to browse on the tree seedlings that are also economically valuable.

Difficulty regenerating hardwoods is not a problem unique to New York. A similar problem has occurred on the Allegheny Plateau in northwestern Pennsylvania, and an intensive management approach using deer fencing and herbicide treatments has been developed to attempt to ensure hardwood regeneration. Our research in northwestern New York is an attempt to understand why the regeneration process has not succeeded and if the methods developed in Pennsylvania will apply in New York. The objectives of this study are to determine 1) if eliminating the herbaceous competition through herbicide treatments will ensure hardwood regeneration, 2) if deer herbivory affects the density of hardwood seedlings and 3) if deer impacts are different when herbicides are applied.

METHODS
Four sites were chosen in the summer of 2000 in St. Lawrence County, in the northwestern portion of the Adirondack Park. Three of the 4 sites had timber management practices performed on them (thinning or shelterwood cuts)prior to our study. The final site was a salvage operation performed after the 1998 ice storm, but closely resembled a shelterwood cut in terms of residual basal area. All sites were typical northern hardwood stands primarily consisting of black cherry, sugar maple, red maple (Acer rubrum), and some scattered white ash. These areas had high densities of white-tail deer (roughly 25 deer/sqmi). The herbaceous layer was dominated with various ferns (especially hayscented fern), grasses (especially Cinna latifolia and Brachyeletrum erectum), sedges, goldenrods or rubus spp. The soils were typically glaciated, sandy outwash.

On each of the 4 sites, 4 exclosed plots were paired with unexclosed plots. Half of the pairs were sprayed with an herbicide. A mixture of Oust and RoundUp was used. RoundUp was used as a defoliant and Oust killed the rhizome rooting structures of the ferns and grasses. Herbaceous cover was measured within the plots by percent cover. The number of seedlings were counted within the plots in four classes: 0-1 ft in height, 1-3 ft in height, 3-6 ft in height and 6 ft in height to 0.5 inch DBH.

RESULTS
There were no statistically significant differences for herbaceous cover and seedling counts between the exclosed and unexclosed. The herbicide treatment successfully killed the majority of competing vegetation leaving these areas covered with dead vegetation. The herbicide treated sites had a number of black cherry, sugar maple and red maple seedlings but goldenrods were also germinating. In general, mature seedlings greater than 6 ft. in height survived the herbicide treatment but many immature seedlings did not. Since this was only the first year for this research, no statistically significant interaction between the herbicide and exclosure treatments was evident.

DISCUSSION
Exclosed and unexclosed plots did not demonstrate significant results probably because this study has only been conducted for only one growing season. The herbicide treatment proved effective in killing off all vegetation competing small seedlings (< 3ft. in height). This year's (2001) germination was apparently not affected by the herbicide treatment as a substantial number of seedlings that had sprouted. The germination was not effected by deer browsing because deer rarely target saplings under a foot.

With more time the exclosed plots treated with herbicides serve as a sanctuary for desired tree seedlings. The fate of untreated exclosures will partially depend on the dominant herbaceous cover. Untreated exclosures dominated by Rubus spp. may regenerate well because Rubus spp. do not cast the deep shade typical of dominant ferns, grasses, and goldenrods. Given enough time, unexclosed plots will probably demonstrate that high deer populations have detrimental effects on tree regeneration, especially when herbicides are not used to control competing herbaceous cover.

Although herbicide treatments were effective in killing competing herbaceous cover for the first growing season, it is uncertain whether germinating seedlings will establish prior to the regrowth of the competing vegetation. The protective seed coat of some tree species allows the seedling to develop from the seed bank immediately after herbicide treatment (especially black cherry). However, annual herbaceous species, including some grasses, sedges, and goldenrods have protective seed coats and may continue to compete with desired seedlings. This competition in the herbicide treated plots will be an interesting thing to monitor in years to come. Another problem that might arise when applying herbicides is the potential loss of mycorrhizal fungi in the soil. Trees that we are trying to regenerate have endosymbiotic relationships with these fungi. Mycorrhizal fungi need sugars to maintain a homeostasis and without the proper nutrients they will die. The herbicide kills off all plants and, therefore, potentially kills the mycorrhizae. If these newly emerging seedlings can survive the time period that mycorrhizae need to regrow, then this should not be a problem.

Contact Information
For more information contact Eugene Nichols at Kingfisher06@hotmail.com , Katie Johnson kljohn02@syr.edu or Karl Didier at kadidier@syr.edu

About The Author: Eugene Nichols
I am a transfer student from Finger Lakes Community College where I obtained an associates in Conservation Law. I am studying Environmental Forest Biology here at ESF and plan to have a focus on ornithology conversation biology. My other hobbies are short story writing and participating on the SU table tennis club team.