This week for Flora and Fauna Friday we have a thin porcelain-skinned nut-bearing tree, American Beech (Fagus grandifolia).
American Beech is a common tree in floodplain forests, where it relishes the moist soils rich in nutrition from periodic floods. Yet Beech does not grow well on the soggy soils of the bottomlands, sticking to the higher and drier soils of the upper floodplain. American Beech is a beautiful and unmistakable tree. Its marble-white bark puckers like goosebumps and wrinkles like muslin as it conforms like skin to its muscle furrowed trunk. This skin extends to shallow roots that often grow down over obstacles and up into a buttress. This bark in and of itself distinguishes the Beech from its Lowcountry surroundings on all but our whitest winter days. Yet on those scarce snowy mornings Beech still stands apart from its neighbors. American Beech is unique in that it holds onto its fall foliage until spring. Although thoroughly brown and devoid of life, last year’s leaves remain until new buds break. This makes Beeches easy to spot from the roadside on a frigid winter drive. Beyond the zombie leaves lies another novel feature, the bud. Beech buds are easy to ID as they are unusually long and slender, sometimes a full inch in length. These oversized buds break in fall to quickly produce a new twig with leaves. The leaves of American Beech are moderately large and elliptical with a dentate margin. Dentate leaves have a regularly toothed margin like the blade of a saw. American Beech also produces edible nuts. These nuts ripen inside a coarsely hairy pod that splits in four to dispose of the nuts within. Each pod contains two or three nuts and each nut is teardrop-shaped and triangular in cross-section.
Beech trees are a species known for strong mast reproduction. Mast reproduction is a phenomenon of many nut bearing trees and shrubs. Unlike plants that produce berries or other soft fruits, nut bearing trees do not want animals eating their fruit. When an animal eats a soft fruit, they eat the nutritious flesh around the seed and either discard the seed or swallow it whole. This helps spread the seeds of soft fruits and their parent plants encourage animals to eat them. When animals eat nuts, they crack the seed itself open and eat the embryo inside. This kills the seed and is the exact opposite of what the nut-bearing plant wants. To counteract this, some nut trees have developed mast reproduction. Mast reproduction works at the population scale with all trees in a population or region responding in unison to some environmental trigger. The type of trigger varies widely by species but all achieve the same end goal. When mast reproduction is triggered, all the trees in an area will produce a bumper crop of nuts. This unified seed production has several benefits: it improves the chances of cross-pollination in wind pollinated species, the individual plants can take full advantage of ideal growing conditions to maximize seed production, and most importantly the trees can overwhelm would-be seed eaters. This latter benefit falls within the predator saturation hypothesis and the strategy is ostensibly victory through attrition. By starving the seed eating animals of nuts on non-mast years, the plants can keep their predator’s populations relatively low. Then when the trees undergo mast reproduction, there just flat out aren’t enough squirrels, deer, mice, or turkeys to eat all the nuts before the next spring. Meaning a far higher proportion of seeds will survive to germinate than otherwise would have been possible.
American Beech can reach a considerable diameter and live for several centuries. However, few large Beech trees remain as they often grew on the most productive agricultural soils, which have long since been logged, and those that grew elsewhere were easily damaged by fire. Those large trees that do remain or those that have come up in the last century are invariably vandalized. Beech’s thin, smooth bark is seen by hikers and love-struck youths as a perfect canvas for carving. Carvings damage the thin layer of vascular cambium below the bark. Damage to this layer prevents that portion of the trunk from growing, causing the surrounding tissue to swell and callous in an attempt to heal the wound. On thin skinned trees like Beech, it can take years or even decades for these wounds to heal and even longer for callouses to disappear. A single carving is rarely a problem for a fully grown tree but trees on public parks or along hiking trails are often filleted to the point of infection. Each carving exposes the tree to infection and the wood of Beech is not particularly rot resistant. Meaning any carving may end up being the death nail for the tree.
