Hiking Through the Fern
By: Matt O'Brien
Tags: Management, Forest, Plants, Fern

The forest floor densely covered by fern along the Tanbark Trail, Allegheny National Forest. Photo by Matt O’Brien

The North Country National Scenic Trail is a hiking trail that spans from North Dakota to Vermont (NPS, 2015). The final length of the trail will be around 4,500 miles and will be the longest of the eleven designated National Scenic Trails (NPS, 2015). Luckily, this trail passes through the Allegheny National Forest and is only a short drive from where I live. One of my favorite passages of the Allegheny portion of the trail is on a scenic railroad grade heading towards Chappel Bay of the Allegheny Reservoir. On this grade, I got to walk under second-growth trees with ferns on the forest floor as far as I could see. As I progressed further on the grade, the ferns started to decrease and the forest was abundant with not only second-growth trees, but seedlings and shrubs on the forest floor as well. Why was there a such a difference in the forest between where fern was and was not present? I didn’t think too much on the question until I hiked elsewhere in the National Forest. On the Tanbark Trail, outside of Warren, PA, I yet again ran into a fern dominated forest. Second-growth trees were scattered among the fern dominated portions of the forest, just like I had seen previously on the NCT, and seedlings and shrubs abundant in areas scarce of ferns. Both of these observations have begged me to ask: does fern growth impacts forest regeneration? I decided to investigate this question by selecting specific species of ferns and how they impact regeneration of plant species.

Impact of Hay-scented Fern on Forest Regeneration

Hay-scented fern (Dennstaedtia punctilobula) occurs in open woods, clearings, and on roadside banks (Conard, 1908). It prefers well-drained areas that have sandy or stony soil (Conard, 1908). When optimal growth conditions are present, the hay-scented fern (D. punctilobula) usually forms thick beds (Conard, 1908). When the fern grows in thick beds and starts to dominate the forest floor, it begins to out compete any seedlings that are growing below the ferns. Another characteristic that allows it to grow is that it is unpalatable to deer, as herbivory by white-tailed deer (Odocoileus virginianus virginianus) is considered the most important reason for failure in forest regeneration (Horsley, 1981; Marquis and Brenneman, 1981; Tilghman, 1989). Due to these factors, hay-scented fern (D. punctilobula) impacts the growth of several species. For example, where fern cover is dense, there are approximately 80% fewer Black Cherry (Prunus serotina) seedlings and surviving seedlings invariably fail to become established (Horsley, 1977b; Horsley and Marquis, 1983). Hay-scented fern (D. punctilobula) impacts the growth of Black Cherry (P. serotina) seedlings by altering the availability of light close to the forest floor (Horsley, 1993).

A close up image of Hay-scented Fern (Dennstaedtia punctilobula). “Hay-scented Fern” by Amada44 is licensed under the Creative Commons Attribution 2.0 Generic License

A Sugar Maple (Acer saccharum) seedling growing in the Allegheny National Forest. An example of one of the species that can be impacted by Hay-scented (D. punctilobula) growth. Photo by Matt O’Brien

Hay-scented fern (D. punctilobula) also impacts growth of other tree species as well. The presence of these ferns impacts Northern Red Oak (Quercus rubra) by reducing height, shoot growth, root growth, root branching in the organic horizon, and ectomycorrhizal infection rates (Lyon and Sharpe, 1996). Sugar Maple (Acer saccharum) seedlings are sixteen times less likely to occur in an area with Hay-scented Fern (D. punctilobula) presence (sharpe halofsky).

Controlling Hay-scented Fern

Climate change has impacted ecosystems across the globe by altering conditions over time. Spread of Hay-scented fern (D. punctilobula) has been able to benefit from climate change. Soil acidification caused by acid deposition is one of the ways that climate change has altered ecosystem conditions that allow optimal growth conditions for these ferns to grow and spread on the forest floor (Robert 1994; Drohan and Sharpe 1997). Soil acidification leads to base cation leaching, increasing aluminum concentrations, and an imbalance of Calcium and Aluminum in soil solutions and in the rhizosphere (Sharpe and Halofsky, 2004). Areas in forests where the soil is acidic may limit regeneration of tree species that are sensitive to acidic conditions and leads to an increase in acid-tolerant plant species that are able to adapt to a changing environment (Sharpe and Halofsky, 2004). Hay-scented fern (D. punctilobula) is one of these species that are able to adapt to changing environmental conditions and could continue to do so with changing environmental conditions due to global climate change (Sharpe and Halofsky, 2004). Due to the adaptability of this plant species, there have been studies on how to control the growth and spreading of this fern species and others. For example, if deer browsing is either reduced or completely eliminated, tree species such as Black Birch (Betula lenta) and White Pine (Pinus strobus) could be able to establish and outcompete fern colonies (de la Cretaz and Kelty, 1996). This means that forest management strategies, such as thinning of the overstory, should be delayed until deer herbivory can be managed (de la Cretaz and Kelty, 1996).

References

Conard, H. S. (1908). The Structure and Life-History of Hay-scented Fern. Carnegie Institution of Washington. https://books.google.com/books?hl=en&lr=&id=ExIoAAAAYAAJ&oi=fnd&pg=PA1&dq=hay-scented+fern&ots=rkbnrlUkTI&sig=qRKdKiNpbkE2J5Nu73pBI4Q8fm4#v=onepage&q=hay-scented%20fern&f=false

de la Cretaz, A. L., & Kelty, M. J. (1999). Establishment and control of hay-scented fern: a native invasive species. Kluwer Academic Publishers. 10.1023/A:1010098316832

Horsley, S.B. (1977). Allelopathic interference among plants. II. Physiological modes of action, pp. 93–136, in H.E. Wilcox, and A.F. Hamer (eds.). Proceedings of the 4th North American biology workshop. State University of New York, College of Environmental Science and Forestry, Syracuse.

Horsley, S.B. (1981). Control of herbaceous weeds in Allegheny hardwood forests with herbicides. Weed Sci. 29:655–662.

Horsley, S.B., and Marquis, D.A. (1983). Interference by weeds and deer with Allegheny hardwood reproduction. Can. J. For. Reg. 13:61–69.

Horsley, S. B. (1993). Role of Allelopathy in Hay-scented Fern Interference with Black Cherry Regeneration. Plenum Publishing Corporation. 10.1007/BF00980704

Lyon, Johnathon., & Sharpe, William. E. (1996). Hay-scented fern (Dennstaedtia punctilobula(Michx. Moore) interference with growth of northern red oak (Quercus rubra L.)seedlings. Heron Publishing. 10.1093/treephys/16.11–12.923

Marquis, D.A., and Brenneman, R. (1981). The impact of deer on forest vegetation in Pennsylvania. USDA Forest Service General Technical Report NE-65.

National Park Service. (2015, April 10). North Country Trail. National Park Service. https://www.nps.gov/noco/faqs.htm

Robert, J.R. (1994). Long-term changes in forest soil acidity in northern Pennsylvania. Pennsylvania State University. 187 p. M. Sc. thesis.

Drohan, J.R. and Sharpe, W.E. (1997). Long-term changes in forest soil acidity in Pennsylvania, USA.Water, Air, and Soil Pollution 95: 299–311

Sharpe, William E.; Halofsky, Jessica E. (2004). Hay-scented Fern (Dennstaedtia punctilobula) and Sugar Maple (Acer saccharum) Seedling Occurrence with Varying Soil Acidity in Pennsylvania. In: Yaussy, Daniel A.; Hix, David M.; Long, Robert P.; Goebel, P. Charles, eds. Proceedings, 14th Central Hardwood Forest Conference; 2004 March 16–19; Wooster, OH. Gen. Tech. Rep. NE-316. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northeastern Research Station: 265–270.

Tilghman, N.G. (1989). Impacts of white-tailed deer on forest regeneration in northwestern Pennsylvania. J. Wildl. Manage. 53:524–532.