Threats to Forest Trees
A few of the trees that we observed at Deep Woods are currently under threat due to certain diseases and insect infestations. For example, the butternut tree (Juglans cinerea) is particularly threatened by a fungal infection called canker disease. Infected trees have dark, sunken areas found around leaf scars and buds called cankers, and often die from the disease quite quickly. Butternut conservation efforts have been somewhat ineffective, as there is no direct way to prevent the spread of the disease in wild tree populations. As a result, conservation efforts have been focused on isolating trees and artificially increasing their fitness to ensure the survival of the species (Farlee et. al. 2). Another significant threat to forest trees is the hemlock wooly adelgid, an invasive insect that parasitizes eastern hemlock trees. The adelgid is native to Asia and is not preyed upon in North America, so it feeds freely upon eastern hemlocks, causing a significant decline in their population. Conservation efforts have included chemical treatments to hemlock trees, as well as introduction of certain Asian predatory beetles to control the adelgid population (Nature Conservancy).
The Appalachian Gametophyte
Vittaria appalachiana, commonly known as the Appalachian gametophyte, is a particularly interesting member of the fern family which we observed at Deep Woods. V. appalachiana is one of the only species of fern whose mature sporophytes have never been observed. While most ferns reproduce sexually by producing spores in their sporophyte life stage, V. appalachiana has only been observed reproducing asexually in its gametophyte life stage. The reproductive cells of V. appalachiana, called gemmae, are significantly larger than most fern spores, meaning their range of dispersal is more limited. These gemmae are thus dispersed only short distances by water, wind, and animals (gemmae dispersal in bryophytes is known to occasionally be facilitated by slugs). It has additionally been observed that many suitable areas in the Appalachian gametophyte’s range have not been colonized, even when in close proximity to the population. Considering these observations, botanists have found that the current distribution of V. appalachiana could only be possible if it had once reproduced via spore dispersal. Thus, botanists have concluded that V. appalachiana must have lost its ability to reproduce sexually around the time of the last ice age (Pinson & Scheuttpelz 669). Furthermore, it is not likely that the current populations of Appalachian gametophyte are being influenced by long-distance dispersal from a different sporophyte source; this would contradict phylogenetic trees constructed from the genetic and morphological data of ferns in the region. It is most likely that the wide range of the Appalachian gametophyte is a result of sexual reproduction and spore dispersal that the fern lost its ability to perform (674).
Two Members of the Birch Family
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Farlee,L., Woeste, K., Ostry, M., McKenna, J., and Weeks, S. “Conservation and Management of Butternut Trees.” Northern Journal of Applied Forestry. 26(1):9-14.https://www.extension.purdue.edu/extmedia/FNR/FNR-421-W.pdf
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Pinson, Jerald B. and Scheuttpelz, Eric. 2016. “Unravelling the origin of the Appalachian gametophyte, Vittaria appalachiana.” American Journal of Botany, 103(4): 668–676
Petrides, George A. A Field Guide to Trees and Shrubs: Northeastern and North-Central United States and Southeastern and South-Central Canada. Houghton Mifflin, 1998.
“Sensitive Fern.” Missouri Department of Conservation. https://mdc.mo.gov/discover-nature/field-guide/sensitive-fern
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