By Dr. Allan Houston
It was an idea compelled with increasing indications that the eastern hardwood forest is growing older and regeneration is lacking. While growing older seems positive, it must be considered in the context of a forest growing older while at the same time being picked over with repeated harvests. As a result, it is a forest slowly occupied with less and less quality. All the while, no widespread attempts are made to regenerate the forest.
Myself and my colleague, Dr. Scott Shlarbaum at the University of Tennessee, decided to attempt genetic improvement of various hardwood species, particularly oak, and follow this by planting highly selected trees into the explosion of woody and herbaceous competition that follows a clearcut. And, then walk away, leaving the seedlings to their fate.
Most scientists said it would not work.
To date there are over 20 species with more than 20,000 trees are under study. To illustrate, for example, if northern red oak was bearing, we identified 30 or so trees that were at least a quarter of a mile apart to prevent genetic kinship. With repeated visits to each tree, and in direct competition with squirrels, deer and turkeys, we collected between 500 and 1,000 acorns.
These acorns are considered to be “half siblings” because while the mother tree is the one dropping the acorns, the paternal influence, represented in pollen coming in from everywhere, cannot be known.
These acorns are transported to a nursery where they are carefully planted and kept separate by mother tree. All summer the seedlings receive an intense irrigation and fertilization regime; and by the time they are lifted in the fall, can be as much as 6 feet tall.
Once lifted, again kept separate by mother tree, they are transported to Knoxville, placed in cold storage and over the winter each tree is graded according to several criteria, including the degree of “first order lateral roots,” the stout offshoots from the main root, a trait that correlates with good growth and survival. The best of these trees are taken to Ames and planted in orchard settings with each tree’s pedigree kept separate.
As the orchards develop, trees are evaluated for various traits, and not just timber production, but wildlife attributes too. For example, in a water oak orchard the progeny of one mother tree tends to hold their acorns aloft until well after the first of the year, a trait that might be excellent for wildlife. Another “family” produces smaller than normal acorns, a trait perhaps good for various birds, quail included.
We have also collected plum twigs from the various patches and created rooted hedgerows in an attempt to preserve a quickly vanishing part of the historical landscape.
Of course, as might be imagined the resources needed to accomplish this are large, with nursery space and treatments, greenhouses, equipment, labor to sort, grade, mark, transport and plant the trees. Each tree is virtually irreplaceable. Therefore, electric fences are erected around the orchards to discourage deer from destroying the plantings. Actually, the fences serve more in the way of “advice” than a complete deterrent. But, after a generation or two of deer have experience with the fences tend to stay out of the orchards, mostly.
It has been astounding to discover the variability within even a single species. Acorn production is a case in point. Some trees bear early and tend to be prolific throughout their life. Some start in mid-life and tend to bear well from then on, some begin well then slack off to become nearly barren, and some families simply tend to not have many acorns at all. Stem form can vary among families, with some having a strong inclination to form forks, at about the same height, not a desirable timber trait.
The project also tested the ability of these trees to compete once planted behind a clear-cut and left to fight it out with the ensuing explosion of competition.
Typically, sycamore and sweetgum in the bottoms and yellow polar in the uplands dominate the regeneration; and while these are good species for some purposes, they fail to provide many of the timber and wildlife benefits of oaks.
A particular objective of the study was to create mixed stands as opposed to single-species plantations. We want to enrich the developing regeneration with our selected trees. The objective is to have about 36 planted trees per acre at maturity. Given the normal stature of a large oak, 36 trees per acre would capture about half of every acre and would be of enormous interest to any timber buyer. Or squirrel or turkey or deer.
A person needs to chop their way into a young stand for measurements to get a true appreciation for how fierce the competition can be in the early years. Briars, weeds, vines, trees and more briars form a spiderweb of competition. Not all the planted trees live. Many are outpaced and dwindle into the shade. But, some make it and some make it spectacularly.
These are not small studies. In one planting of over 4,000 trees, with cherrybark and swamp white oak featured, there are many trees that approach 60 feet tall at 15 years of age; and, before we project them as being “winners,” they must also surpass rigorous crown-size-and-position parameters.
I tell students the greatest expense in forestry is “failure,” because poor decisions can last a long time. A stand that develops and grows through a full rotation without oak, if oak was possible, is a form of failure, at least to someone who must deal with the stand years down the road.
The project has developed into the very leading edge of hardwood silviculture. That leap of faith and the entire project, from beginning to date, 20 years of work, and with trees in nurseries and greenhouse soon to be planted, would not be possible without the continuing support of the Trustees of the Shackelford Trust.