Tag: Oak

Falling Acorns

Although summer has continued its fierce rearguard action well past a reasonable concession date, autumn is here.  True to the colloquial name, “fall”, the trees are divesting themselves. But I’m not talking about leaves; there is still a lot of green in the trees at the moment.  I’m looking at acorns, specifically white oak acorns.

The white oak (Quercus alba) is an all-around excellent tree.  Large, long-lived, and handsome, much can be said about this species and its lumber (including being crucial for bourbon barrels and earning USS Constitution its “Old Ironsides” nickname).  But on this October day I want to talk about the nut of the oak. 

White oaks are the flagship of a cluster of species known as the white oak group (which include English oak, burr oak, post oak, overcup oak, and scores of others), as opposed to the red oak group (locally represented by the southern red oak, northern red oak, water oak, pin oak, and others). White oaks produce acorns on a one-year cycle – that is, spring blooms will develop into acorns in the early autumn, while red oaks take two years to produce.  Red oak acorns tend to drop later in the season, and are much more bitter due to the higher tannin content.  On the plus side, red oak acorns will be available to deer during the hungry months before green-up, while white oak acorns germinate soon after hitting the forest floor.

White oak acorns have been falling in prodigious quantities for a couple of weeks now.  The tree which stands closer to the house than the deer like to venture has carpeted the ground with the leathery brown nuts. This is definitely a good mast year (“mast” is the collective term for nuts, berries and seeds from trees that are eaten by wildlife) for white oaks.  You see, oak mast production is hit-and-miss; several years may go by before there is a bumper acorn crop for a given locale and species.  Acorns are sought after by a great many birds and mammals, so on an average year few if any acorns will actually make it to germination.  Periodically, a super-abundant crop of acorns will flood the market as it were, providing more nuts than wildlife can consume or stockpile, and increasing the chance that a tree’s attempt at reproducing will be successful.  Naturally, the extra food is welcomed by turkeys, deer, squirrels, jays, and other hungry critters.  It’s good for wildlife when there are several oak species in the local forest – if the northern red oak is a bust this fall, perhaps the scarlet oak will be a boom. 

This is a good year for the critters to fatten up on white oak acorns.  We’ll soon see if the red oaks will call, raise, or fold.

Windthrown

How is a climax forest renewed?  How does it go from dense overstory canopy to grasses, forbs, and tree seedlings?  Nowadays, the chainsaw is the chief instrument of change.  Beyond human actions, the likely sources for canopy-opening are fire (from lightning) and wind.  My corner of the Piedmont met the latter last week.

It was likely a straight-line wind barreling ahead of a thunderstorm, although a small tornado was possible. It came with freight train roar and the snap and crash of century-old trees. A morning’s survey of the damage revealed windthrows and snapped tops, in singles and groups.  A few widowmakers will merit wary observation in the weeks to come. 

Here, the red oaks were more likely to be thrown, while white oaks usually snapped.  I suspect this is in part due to the root systems – while all oaks spread lateral roots beyond their canopy driplines, white oaks delve deeper into the soil, chasing water and anchoring themselves more firmly that their red kin.

Below is the most impressive root ball I found today.  Look closely on the right side.  That two-tone walking stick with the black cap on top is five feet tall.  Using that for scale, the web of roots hold a block of soil over 20 feet wide!  It’s clear that the roots extended 10 or 15 feet beyond that.

The windthrows give us an opportunity to look at the soil profile.  The leaf litter and decayed organic material mixes with mineral soil to create a rather thin topsoil layer; here, litter and topsoil measure around four inches. Below that is the clay-rich loam common to this area – stripped of rich topsoil by a century or two of poor land management.  After decades of rest, this spot has recovered a scant few inches of organic soil.

The logs will do their part, as insects and fungi convert wood to soil.  However, the falling giants create a more immediate change.  The new gaps in the canopy break the sunlight blockade which the dominant trees impose upon everything below them.  Unbroken canopy is not a hospitable place for shade-intolerant plants; apart from the hardy muscadines, there is little green to be found on our forest floor. Yearly, pine seedlings rise and die in short order, starved of the sun’s energy.  Even oak, hickory, and beech seedlings struggle to subsist on whatever only dappled or filtered light reaches them.  These hardwoods may spend many years in a shrubby state, if they don’t succumb to solar neglect.  But things change when a gap opens in the canopy.  Sun-fed trees get a sudden boost of energy and growth, reaching towards the sky. 

Where there is a gap vacated by two or three trees,  and a dozen or more seedlings pushing through the leaf litter, there will eventually be competition for that space.  Assuming no more disturbances, a decade or so will find the trees trying to outgrow each other – overtopping their neighbors and claiming the underground real estate until the victorious few take their place in the canopy.

I won’t be here to see the outcome, but I’m betting on the oak. Regardless, so long as people leave this forest alone, the gradual renewal of the climax forest will continue on every acre.