From a
sustainability perspective, there are right ways and wrong ways to cut trees. A
well-planned and executed timber sale focuses on two outcomes: What are you
leaving to manage in the future (the residual)? Or, what will or have you done
to establish or release regeneration (the next forest)?
If you own
more than 20 acres of woodlands, you have likely received a letter or postcard
soliciting an opportunity to talk about harvesting trees. The letter might
refer to a “select” or “selective” harvest, or cutting only trees larger than a
certain diameter. Somehow, they all sound good. These words seem to say the
buyer will be careful and select the correct trees to harvest, right?
From a
sustainability perspective, there are right ways and wrong ways to cut trees. A
well-planned and executed timber sale focuses on two outcomes: What are you
leaving to manage in the future (the residual)? Or, what will or have you done
to establish or release regeneration (the next forest)?
Unfortunately,
terms like “select” and “selective” focus on the trees to cut, rather than the
trees to keep. The buyer will select the trees to cut using some criteria such
as tree diameter. Where these are the criteria, the select cut becomes a
diameter limit harvest and all trees above a set diameter are sold and cut. The
logic is that big diameter trees are old and smaller diameter trees are
younger. This logic of big and old vs. small and young, however, is most often
far from true.
Sometimes
the big trees are more likely of one or several species that from the start
took advantage of light, moisture, nutrients, and space and jumped ahead. These
trees were successful in getting their crowns into the developing canopy to
snatch resources away from their neighbors. In essence, they were the winners
in the race to gain the dominant position and have continued to exploit it.
When you look at a maturing woodland, you will often see that some tree species
are consistently larger in diameter. Even if you see a tree species with sizes
across the spectrum, just cutting the big ones is almost always the wrong
approach. Cutting them first is akin to “selecting” the best and leaving the
poorer.
Why does
this practice of taking the best and leaving the rest occur? When shopping for
fruit, if you take the best looking, someone gets stuck with the rotten,
misshapen apples, peaches, bananas. Who? Of course, it is the grower or the
store owner. When selling timber, if the timber buyer, or sometimes the seller,
picks the best and leaves the rest, who holds the poor quality trees?
Obviously, it is the landowner, and those actions and outcomes may extend well
into the future as that owner or a future owner tries to recover from a poorly
conceived harvesting decision.
Why would
woodland owners degrade their forest? There might be reasons. Maybe there is no
choice – there is a compelling need for money and taking the best is the only
choice. Sometimes, though, the logic of selecting the biggest and best is
perceived to make sense. That logic connects to the past and extends into the
future. “My grandfather cut these woods. He only took oak trees eighteen-inches
and up, and look at it now. There are lots of oaks and red maples.” Those red
maples or black birches were much less common when that earlier cut was made.
Lack of seed source, herbivory pressure, and other competitive plants have
changed the potential for species to succeed in many places. Sometimes woodlots
can sustain one diameter or select cut, but the careful observer might note a
subtle shift in species composition. The second select cut will shift species,
and likely quality, even further from good to worse. That is the connection to
the future. How many times can we select the best and leave the rest?
Good
harvesting plans have their basis in science, research, and good observation. A
good harvest plan concentrates on improving the quality of the woodlands and
providing sustainable options for the future growth and management of the
woods. Clearly, to practice sustainable forest management takes time – it is a
lot more than picking the best or biggest trees to cut and hoping that those
left will grow big and strong and represent the diversity of species that can
and should grow in our forests. A well-planned harvest focuses on “selecting”
the best to leave. Doing this ensures quality in the next harvest, retains
species diversity, keeps good genetic and species diversity for regeneration,
and results in a healthier and more resilient woodlot.
It is
becoming increasingly obvious to foresters, researchers, and woodland owners
that regenerating healthy and diverse forests is extremely difficult. Too
often, decisions to harvest fail to consider whether tree regeneration is
already in place and adequate. Every timber harvest should look beyond just the
trees that are cut to assess regeneration and what will benefit from the new
light resources reaching the forest floor. It is great when young seedlings are
already there; it is bad when the cover near the forest floor is exotic
invasive plants (think Japanese stiltgrass, bush honeysuckle, garlic mustard
and a host of other species) or native invasive species such as hayscented
fern, mountain laurel, beech brush, striped maple and many more. Recent
research data from the US Forest Service inventory of Pennsylvania’s forests
find that about half of our forests, having undergone sufficient canopy removal
to start to regenerate the area, have enough seedlings of desirable species to
replace the forest. Our mantra, therefore, should be “every harvest has to
consider the future forest.”
It is easy
to fall into the trap that all we have to do is harvest the big trees and
believe that the next forest will be healthy, robust, and there for the next
generation of owners. Practices that on the surface sound good – select,
selective, or harvests based on diameter – are not the tools we need to use to
care for the land. Good forest stewardship and sustaining forest values means
that we have to look forward to leave the best and take the rest.
To learn
more about how to avoid mistakes when planning to harvest timber, contact the
Natural Resources Extension Office to request copies of Forest StewardshipNumber 7: Timber Harvesting an Essential Tool and Regenerating HardwoodForests: Managing Competing Plants, Deer, and Light.
This is an excellent article that, along with the recommended reading, provides a wealth of information that is useful to the woodland owner.
ReplyDeleteAs the article mentions, forest generation and regeneration are complex subjects, and sometimes it seems that what we mere mortals do is overridden by forces of nature beyond our control. The best we can hope for is to go along for the ride and try to influence things in a positive manner.
In my comments on the article by Dan Pubanz, I described how a woodland changed during my relatively short 84 years on this earth; and that we had the first hardwood timber harvest ever in 1995. Make note of the fact that this was the first hardwood harvest of this woodland in the history of planet earth. Prior to this time, the only harvesting done was of the virgin pines and hemlocks in the hollows and spring runs.
Obviously, harvesting practices had nothing to do with my woodland transitioning from scrub oak to harvestable oaks and maples. Nature did this all on its own.
Another natural event that occurred prior to harvest was at least one Gypsy Moth cycle. Fortunately, enough healthy trees survived and seemed to grow more rapidly to harvestable size. It is also possible that more light on the forest floor caused by the Gypsy Moth kills helped the regeneration process after the harvest.
Another example of the power of nature relates to some un-reclaimed strip mining spoil piles on a small part of my property. These date back about 100 years and are possibly the oldest stripping operation in Pennsylvania. They were left entirely to the forces of nature except for some spruce, larch, and pine seedlings planted by a Penn State forestry student in the late 1940s along with some Boy Scout help.
These spoil piles have almost no harvestable hardwood, but are covered with a variety of vegetation that was propagated by nature and now provides excellent wildlife habitat. It was interesting to observe the transition from bare piles of shale to dense growth that is nearly impenetrable.
In conclusion, we can influence regeneration with harvesting practices; but nature is going to have the final word.