Plant Profile: Tree Regeneration and More

The ‘Naturalist at Large’ by the retired biology professor Bernd Heinrich is a feature in the Natural History Magazine; always a favorite of mine. In the last issue of the magazine he writes about ‘The Lives of Trees in the Forest [Growing up in a tough neighborhood]’.

Last year in his northern New England woods he observed a phenomenon that had occurred last 30 years before – the flowering of sugar maple. The tremendous seed production that followed had outstripped all the seed predators’ and parasites’ ability to consume them all. In fact, they had formed lawn-like carpets on the forest floor. In my travels in Illinois over past decades I have on a few occasions encountered such mass maple recruitment; very visible even on the drive-by because of their lawn-like appearance.

In the 30 years that I have been involved with the management of the Shoal Creek CA I have not seen even one maple seedling; nor in decades prior. I remember thickets of young sugar maple from the 1960’s that made for slow going. When might that mass germination event have occurred and what conditions triggered it? It would be good to know, even if we are not all that interested in a repeat. To the contrary we have eliminated literally thousands of maple trees where they had invaded the original oak – hickory upland woodlands. Intense woodland grazing by livestock, lack of historical fire regimes of grazing in the previous 100 years and then sudden cessation of such grazing was now seriously changing the character of our woods. There is another whole story here.

Why then this column? Please bear with me. In late October of last year, I had walked the steep slopes, ravines and uplands of a barrens community. These were ablaze with color; wonderful photo subjects were seen everywhere.

We call this the ‘connector barrens’ project, now in the early stages of recovery. It had been recommended by two eminent ecologists in a recent paper. The barrens to the north and to the south had been recognized in fly-overs during the natural areas inventory in the 1970’s and further explored later on by the state botanist John Schwegman. Removal of sugar maple early on and more recently a reduction of the dominant black oak canopy had dramatically improved the ground flora. Here, as in all other barrens areas, it was not only the herbaceous layer but an abundance of hickory, oak tree and other grubs that became much more apparent, increasing from a few puny stems to an abundance of stout ones in each grub cluster. On the most xeric sites oaks, largely black and red oak, form mounds, colorful in their autumnal garb. They can be quite difficult to tell apart as both may have bright fall foliage. Sometimes you can tell that it is black oak, by far the most common species everywhere, from some distance. The leaves are large, often a bit amorphous. They are amazingly different from those that are falling at the time from mature trees. We could explore here the difference between physiological and chronological age, as it so well expressed here in the black oak species. Looking at the buds, especially apical buds, should make identification easy. But that is often not the case as some buds are intermediate in features. Perhaps we are looking at hybrids. It is complicated. While red oak grubs are common, large trees are not, even being downright rare. Large red oak trees are prized for their lumber and the area was heavily timbered at the time of construction of Lake Yaeger in the early 1960’s. Large black oak still abound. Quite a few toppled as our contractor has girdled many here and elsewhere in recent years. They were truly rotten to the core, with the interior being a crumbly reddish mass, almost to the cambium. Perhaps many already had such issues then and were therefore avoided by the lumbermen.

On that same October walk I encountered large patches of yellow color. On close inspection they consisted of thousands of white oak seedlings. I pulled away some of the sticky clay soil from the thin stem of a sample some weeks later. The seedlings were devilish hard to find without remaining foliage. The sample had a sizable base with old stem remnants and scars. Repeated top kill may be due to our fire management and winter browsing by our huge deer herd. Some years ago, maybe 10, I did a count, revealing some 100 stems per 1 square meter. It was a rather shaded location and the number of survivors decreased drastically over the years. That time included a severe drought in 2012.

I recall growing some white oaks in my early nursery days from seedlings that I had purchased. There was little growth and I wondered why. To my considerable amazement digging them up was quite a chore. The knitting needle-like whips were attached to a huge carrot-like fleshy root descending well over 1 ½’ at which point I severed it. No wonder locals called oaks tap rooted. Are they really? See photo above.

Further on, on the flat ridges, an abundance of oak clusters, still many black but also red, lots of white, blackjack, chinquapin and post oak had shot up 3-5’ since the last burn. Some even exceeded that growth rate. They are oaks, supposedly slow growing; so how can they be capable of so much growth?

More recently I walked the lake shore line and took note of a scruffy oak, maybe 6’ tall or so, hanging over the top of the steep bank. The exposed roots extended 12’ in each direction, all near the surface and no tap root. How much further did they go? Clearly, the oak grubs in the barrens have such an extensive root system as well. Of course, all trees and certainly these grubs are in intense competition with one another. Which one will grow into a large tree, which one will succumb to competition along the way? The spacing between the grubs is close, so only a few will make it.

An overriding question for me has been the age of our mature barrens trees, whether hickory, hop-hornbeam or oak. So far, no ring count has exceeded 120 years. But is that an accurate measure of their age? I have walked the barrens since the 1950s. The grubs were there then, most if not all being the same ones! It would not be a stretch to think that our larger post, white and blackjack oaks that survived past timbering for one reason or another are really well over 200 years old! There is never a dull moment as you walk these woods–  lots and lots of questions though.

The Hidden Life of Trees, by Peter Wohleben, 1915 has been good reading as it sheds wonderful insights into life and competition in the forest. It is a ‘dog eat dog’ (or shall we say ‘tree eat tree’) world out there!