In Defense of Beech Trees

Beech (Fagus grandifolia) are one of my all time favorite trees. They are considered a climax tree species in this region along with maple and hemlock. They stand tall, they support a wide range of species as a food and shelter tree, they are long lived and, their trunks have a smooth, elephantine bark that really makes them stand out. Sadly, this smooth bark also makes them targets for dumb humans who need to proclaim love, peace, or the date in which they were there by carving it into the bark amongst other idiotic scribbles (Fig. 1).

Figure 1. Dumb Hippy Petroglyph

The bark of a tree is it's first line of defense from a wide range of fungi and diseases that would love to feast on tree tissues. There are two types of fungi present in North America that are particularly damaging to beech trees. The fungi are known collectively as beech bark disease but scientifically they are Neonectria faginata and Neonectria ditissima. Sources say these fungi were introduced from Europe and first made its appearance in Maine back in 1932. Beech bark disease is deadly in some circumstances and severely crippling in others. A few trees do show some genetic resistance to infection. The fungus works its way into the living tissue just under the thin bark of the beech and causes cankers to form. If enough tissue is killed, the tree is effectively girdled and it will die. In a majority of the cases the cankers zap enough energy from the tree that it no longer can sufficiently reproduce which has rippling effects through entire forests. As mentioned above, beech are a climax tree species which basically means they are a dominant species in maturing forests. They also a masting species which means that every few years they produce massive seed crops which provide food for numerous forest dwelling species like squirrels and turkey. If this food source is lost, it can spell disaster for forest biodiversity.

So how does the fungus get into the tree? Well, one of the most common ways is due to an invasive scale insect known as the beech scale (Cryptococcus fagisuga). This invasive insect pest was introduced to our forests back in 1985 in an arboretum in Ohio. The females penetrate the bark with their feeding tube and feed on the juices of the tree. They secrete a waxy substance so it is easy to see which trees are infested (Fig. 2).

Figure 2. Beech scale on a beech

Their feeding habits leave small wounds in the thin bark which then serve as infection sites for the fungal spores of beech bark disease. This is bad enough but of course humans add insult to injury every time carving is added to the bark of a beech tree. Carving opens up the bark far worse than the beech scale making infection inevitable. The beech in Fig. 1 is showing the characteristic cankers forming under the bark that are no doubt from the nice pot leaf petroglyph.

We have to be smarter in how we interact with our forests. We need them more than we will ever realize. We have already lost the American chestnut (Castanea dentata) and the American elm (Ulmus americana) as ecologically functional species thanks to other invasive fungi. We are currently losing our ash (Fraxinus sp.) species thanks to the emerald ash borer, hemlocks (Tsuga canadensis) to the hemlock wooly adelgid (also a scale insect) and now beech are in danger. These were all lost due to pests introduced via the horticultural trade. There is even evidence that sugar maple (Acer saccharum) are in decline though the causes of this are a little more difficult to pin down. Our forests are losing some of their most keystone tree species. Change is inevitable over time but at what cost?

Further Reading:

http://www.baycounty-mi.gov/Docs/Health/GypsyMoth/BeechBark.pdf

http://www.dnr.state.oh.us/tabid/5218/default.aspx

http://na.fs.fed.us/fhp/bbd/

http://en.wikipedia.org/wiki/Beech_bark_disease