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The Farmer and His Prize Bull: A High-Grading Analogy

Posted: August 28, 2015

Many landowners allow the woods, which they love so much, to be “select cut,” as some call it. In reality, they are confusing what they think is a good practice with one that is actually negatively impacting the health of their woods.
An example of a mixed species, even-aged forest. What happens to the species and trees when a high grade is imposed on it?

An example of a mixed species, even-aged forest. What happens to the species and trees when a high grade is imposed on it?

No, this is not a farming story. We don’t have the answers to improving lines of beef or milk cattle. Someone may, but not here. Sorry. This is a story about forests, about the trees, about forest history, and about the actions we take in the woods.

As a forester and an educator, I get to talk with many passionate people--people who care so deeply about their woods that they work at it beyond rational economic decisions and into their love. These aren’t all longtime woods-owners; they are also people who just inherited or just bought woodland because they love it. Very often they have woodlands because they want to care for it in a way that makes it better. Yet whether long-tenured or short-, many landowners allow the woods, which they love so much, to be “select cut,” as some call it. In reality, they are confusing what they think is a good practice with what is actually negatively impacting the health of their woods. What is often incorrectly described as a “select cut” is known to foresters as high grading or diameter limit cutting – different names for the same practice. Unfortunately, the misconception that select cuts are a good thing persists.

So what is high grading, select cutting, or diameter-limit cutting? The quick and dirty answer is, “It’s taking the best and leaving the rest.” High grades remove the biggest trees (assumed to be the “oldest” or “most mature”), or trees above a certain diameter (hence, diameter limit). Landowners often think they are doing the right thing, in efforts to thin a stand, make a little income, or “give the little trees a chance to grow up and become big trees…”

It would be so easy if it worked this way. Unfortunately our past history doesn’t make Pennsylvania forests good candidates for this type of harvesting activity. Around the end of the 19th century and start of the 20th, most of Pennsylvania was clearcut. Discoveries of iron ore led to iron furnaces being built to fuel the industrial revolution, and those iron furnaces needed fuel to melt the ore to make pig iron to ship to urban industrial centers. That fuel came in the form of charcoal, made from trees. Colliers (charcoal-makers) cut down huge swaths of the woods to create the charcoal and feed the furnaces. In addition to charcoal production, lumber was a high value commodity, and the leather industry used hemlock for the tannic acid in the bark to tan hides. There was tremendous draw on the forest resource, such that much of the state was essentially cleared of trees in a relatively short window of 30 to 50 years.

How does that past affect our present forests? Many of Pennsylvania’s trees, especially the oaks, grew from stump sprouts, on those same stumps cut for products. Others, early successional species that like a lot of light and bare mineral soil, have seeds that blow around and can take advantage of clear sites. Blue jays and other nut hoarders moved acorns and other hard mast around, spreading the oaks, hickories, and chestnuts. However, this history of regrowth from one earlier time period means that the majority of trees in Pennsylvania’s forests are approximately the same age, the little ones and the big ones.

There are two things to know about how trees grow that play into this story: first, different tree species can tolerate different light conditions and grow at different rates. Second, even within the same species of the same age, there are winners and losers in the race to grow tall and have wide crowns.

Take a look at the image accompanying this piece. This sketch represents a mixed species, even-aged stand or group of trees in a forest, grown out for, say, one hundred years. In it, on the right hand curve we see the trees that are fast growers and who like a lot of sun (early successional species, in this example black cherry), which got established quickly and grew. We don’t see a lot of little black cherries in this forest, because they need a lot of sunlight to get started and, with the other species in the mix, we can tell that there’s not a lot of sunlight reaching the forest floor. The middle curve is the mid-successional species (in this example white ash) that are a little more tolerant of shade. In this curve there are some big ones that had great growing sites, or were of better breeding stock, and some smaller ones that are falling behind. The left hand curve represents the late successional species, sugar maple here, that can germinate and grow in not much light. There are a lot of little ones because they can hang on in the understory of the forest for many years. In this stand we have three different species, of about the same age, with different growing rates based both on the potential of the site, competition, and the differences in the trees’ preferred growing spaces.

Now impose a diameter limit cut on this stand (represented by the vertical dotted line) and what happens? Depending on where you impose it, what limit or size tree is cut? The best and biggest trees are often taken, and sometimes whole species are lost.

Look at the dotted line. What happened to our stand of trees? We just lost almost all of the early successional species, the black cherry. We lost the better half (and biggest) of the white ash, and the very best of the sugar maple. Black cherry is a forest food for wildlife. What did we just do to that food source in these woods? Oak is an intermediate shade tolerant species – it likes a little sun, but can tolerate a little bit of shade. What if oak were the middle curve and wildlife was an important landowner goal in the woods? What would happen to your favorite wildlife food producer? What happens when we implement the next high grade on the stand? What is going to be left?

Recently I read an article by a very smart forest landowner who was paying attention to the forest history on his hunting camp – an area repeatedly high graded. He came up with a great analogy which then got further modified by a conversation with another smart person about this topic. Imagine the trees are your herd of cattle. Does it make sense to cull your best breeding stock and expect to get the strongest lines from those left? No one faults the farmer for harboring his prize bull. Why do we not offer the same consideration to our trees?

What should be done instead? If the interest is in opening up a stand to allow for growth on the remaining trees (space, light, water, and nutrients for tree growth are limiting resources), consider taking the worst first and freeing those best ones to grow a little bigger. If it’s time to start the forest cycle over with a new, young forest, do preliminary work to ensure that you have regeneration from those best trees on the ground before you remove them – this may mean opening up the canopy to allow a little more light for seedlings to get established, paying a great deal of attention to potential threats from invasive or competitive plants, and then in a few years you can remove the big trees. It may mean erecting a fence to protect some seedlings so they aren’t all removed or damaged by deer so they have a chance to grow tall.

Trees are a renewable resource. Eventually the better trees can be cut, but it takes experience, practice, and much consideration to decide when to make this next harvest and to do it well. We are lucky trees grow well here in Pennsylvania. If we continue to make decisions about harvesting our woods that remove the best trees, that remove whole species of trees, we lose options for the future forest. We lose forest health and forest diversity, which trickle down to the wildlife and to us. Let’s stop high grading our woods and keep those “prize bulls” around, until they’ve proven their breeding potential in creating the next forest.

Contact Information

Allyson Brownlee Muth, Ed.D.
  • Forest Stewardship Program Associate
Phone: 814-865-3208