General Natural History
The American Beech tree (Fagus grandifolia) is a deciduous hardwood tree, native to eastern North America. Its habitat ranges in Canada from Nova Scotia to southern Ontario, and in the United-States from its western limit of Illinois, south to northern Florida (Forrester, McGee & Mitchel 2003). Although, it may have a wide range, F. grandifolia stands tend to be located where the soil is predominantly well-drained, loamy podzols derived from glacial till (Latty, Charles & Marks 2004). F. grandifolia can grow up to 20 – 35 meters in height and live upwards of 300 years; it is also covered with a distinctive smooth silver-gray bark and produces dark green foliage (Forrester, McGee & Mitchel 2003). The tree also produces hard mast (nuts), which are small and sharply angled contained within a soft-spined husk.
When considering the long lifespan of the beech, it is no surprise that it will typically not create large quantities of mast until approximately 60 years of age (Faison & Houston 2004).
In-part due to the vast range in which F. grandifolia can be found, and the abundance in which it can be found in that range, it plays an important role in the forest ecosystem. Many vertebrates, large and small, from black bears to squirrels depend on the hard mast produced by the beech for survival; many rely on it as an important autumn food source (Faison & Houston 2004). In the case of the American black bear (Ursus americanus) as well as many others, it is possibly the most important food source. This is especially true for those in the northern range of F. grandifolia’s habitat, which is dominated by spruce-hardwood forests; the hard mast produced by the tree may be the only available to the animals (Faison & Houston 2004).
F. grandifolia’s importance to animals not withstanding, it is also a defining factor in the ecology of the forest’s soil. Due in part to the green foliage created by F. grandifolia it plays an important role in the nitrogen cycle. Its leaves contain the highest concentration of nitrogen (3.0%) of all canopy trees growing in North America’s eastern forests (Latty, Charles & Marks 2004). The thick foliage also restricts a large portion of light from reaching the forest floor and in autumn, when the foliage falls, the thick layer of slowly decomposing leaf litter it produces also inhibits the ability for new species to take hold (Forrester, McGee & Mitchel 2003).
Specific Natural History and Research Done
There is a lot of research out there on the American beech tree concerning the Beech Bark Disease (BBD). This disease has killed many beech trees across North America (Latty, Canham & Marks 2003). It is caused by two organisms, the introduced beech scale Cryptococcus fagisuga, and one of two fungi, either the native Nectria galligena or the invasive Nectria coccinea var. faginata (the latter one is more often associated with the disease) (Latty, Canham & Marks 2003; Faison & Houston 2004).
BBD starts when a forest becomes heavily infested by the beech scale insects (Faison & Houston 2004). They invade the trees and feed on the bark, causing death to the bark cells (Ehrlich 1934). This renders the trees susceptible to infection by the fungi (Ehrlich 1934). This results in the death of many beech trees, sometimes within one or two years (Ehrlich 1934). After this, the forest consists of root sprouts and a few large trees; tree mortality is usually lower in this aftermath stage (Faison & Houston 2004).
There are various factors that determine the extent of beech scale invasion and infection on American beech trees. Some factors include: genetic resistance to scale infection (about 1% of the population); the formation of crustose lichens on the bark, making unfavourable conditions for the insect; the nutritional content of the bark; and presence of predators (Houston 1994; Latty, Canham & Marks 2003). Another important factor is the prevalence of wind, animals and people in the environment, as this is how they are transported (Wainhouse 1980; Houston 1994). Tree diameter is another important consideration; the larger the tree, the more susceptible it is to invasion by the beech scale (Latty, Canham & Marks 2003).
There are also factors that determine extent of fungi infection. The most important one being the extent of infestation by beech scales, as fungus can only invade where the scale has colonized (Ehrlich 1934; Houston 1994). Furthermore, populations of fungus can be affected by parasites, such as Nematogonum ferrugineum, and by the prevalence of wind and rain in the environment, as this is how they spread (Houston 1994).
This disease has huge effects on the ecosystem and humans alike (Barker et al. 1997; Hane 2003). BBD greatly reduces the mast production of beech trees; many animals depend on the nuts as a food source (Latty, Canham & Marks 2003). The disease causes defects in the wood, such as cracking and falling away of the bark, which can affect the quality of the wood for human use (Ehrlich 1934; Barker et al. 1997).
Seeing as these trees are also an important sink for soil nitrogen, their increased mortality affects nitrogen cycling (Latty, Canham & Marks 2003). Furthermore, the increased mortality of mature trees, and the cutting down of infected trees for disease control, has resulted in higher amounts of beech saplings in the forest, which has an adverse effect on maple tree seedling survival, and results in stands of genetically susceptible American beech trees (Hane 2003; Latty, Canham & Marks 2003).
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Barker, M.J., Pijut, P.M, Ostry, M.E. & Houston, D.R. (1997) Micropropagation of juvenile and mature American beech. Plant Cell Tissue and Organ Culture, 51, 209-213. DOI: 10.1023/A:1005953212568
Erhlich, J. (1934) The beech bark disease: A Nectria disease of Fagus, following Cryptococcus fagi (Baer.). Canadian Journal of Research, 10, 593-692. DOI: 10.1139/cjr34-070
Faison E.K. & Houston D.R. (2004) Black bear foraging in response to beech bark disease in northern Vermont. Northeastern Naturalist, 11, 387-394. DOI: 10.1656/1092-6194(2004)011[0387:BBFIRT]2.0.CO;2
Forrester, J.A., McGee, G.G. & Mitchell, M.J. (2003) Effects of beech bark disease on aboveground biomass and species composition in a mature northern hardwood forest. Journal of the Torrey Botanical Society, 130, 70-78. DOI: 10.2307/3557531
Hane, E.N. (2003) Indirect effects of beech bark disease on sugar maple seedling survival. Canadian Journal of Forest Research, 33, 807-813. DOI: 10.1139/X03-008
Houston, D.R. (1994) Major new tree disease epidemics: Beech bark disease. Annual Review of Phytopathology, 32, 75-87. DOI: 10.1146/annurev.phyto.32.1.75
Latty, E.F., Canham, C.D. & Marks, P.L. (2003) Beech bark disease in northern hardwood forests: The importance of nitrogen dynamics and forest history for disease severity. Canadian Journal of Forest Research, 33, 257-268. DOI: 10.1139/X02-183
Latty E.F. Charles D. Canham C.D. & Marks P.L. (2004) The effects of land-use history on soil properties and nutrient dynamics in northern hardwood forests of the Adirondack Mountains. Ecosystems, 7, 193-207. DOI: 10.1007/s10021-003-0157-5
Wainhouse, D. (1980) Dispersal of first instar larvae of the felted beech scale, Cryptococcus fagisuga. Journal of Applied Ecology, 17, 523-532. DOI: 10.2307/2402634