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Why Thinning Matters

 range of red pine

Figure 1. The natural range of red pine (Pinus resinosa) in the northeastern US; Source: commons.wikimedia.org.

In general, in northeastern forests, tree regeneration occurs naturally. While the regeneration may not be of desired or high-value species due to intense selective browsing by deer, under normal circumstances, an open field with nearby seed trees could result in up to 50,000 seedlings per acre, which is more than enough if we want to end up with 50 to 100 high-quality trees per acre in a mature forest 80 to 100 years later.

But what are the consequences of not being able to carry out the timely thinning and reduction of stand density that foresters would like to achieve? How does thinning—or the lack of thinning—affect the quality of the sawlogs produced, and what are the effects on the value of the products that are able to be made from those logs? Let’s examine an example from my woodlot that demonstrates the long-term benefits of thinning.

https://drive.google.com/open?id=10eGkyikT4fh6XJ0L2Z60P2EI6zyGY79N

White pine (Pinus strobus) is found throughout New York State, while red pine (Pinus resinosa) has a much more limited range in New York (Figure 1). As part of the reforestation efforts that took place in the first half of the 20th century, large numbers of conifers were planted in abandoned agricultural fields. Recognizing that open-field plantings of white pine would result in the white pine weevil (Pissodes strobi) infesting the terminal leaders of many of these young trees destroying their future lumber value, many fields were instead planted with red pines. This resulted in stands of red pine being planted far outside of its native range and preferred soils in many areas of New York.

We are fortunate in having two areas planted in red pine by two different owners on our current property. One small area of one acre was planted with very close spacing of the trees and was never managed in any way thereafter. The second area of five acres was planted in 1927 and was heavily thinned in the 1940s when the trees were about 6 inches in diameter. You can still see the evidence of this thinning from the hundreds of partially decayed stumps that are still visible on the plot. I was fortunate to be able to obtain the history of this plot from my neighbor, who was born in 1906, and who planted and thinned these trees with his father. They also trimmed the remaining trees with pole saws, removing branches and branch stubs on the lower stems, resulting in butt logs with clear lumber.

My wife, who is both younger and smarter than me, works from a home office. After I retired in 2012, she decided that the best way to get me out of the house so she could have a peaceful and quiet work environment was to encourage me to buy a tractor and sawmill. I was going to buy a small manual sawmill, but one of my more knowledgeable and practical friends identified the challenges of a manual mill, so I ended up getting the smallest hydraulic mill that Wood-Mizer makes, the LT-35. Sometimes it is a wonderful thing to have a spouse who wants to get rid of you and friends who realize your limitations.

The acquisition of the tractor and sawmill has resulted in my sawing lots of red pine to build a heated wood-working shop which was strongly encouraged by my wife to get rid of me in cold weather. So I have ended up sawing many thousands of board feet of red pine, which led me to begin to understand how the size of a log influences the value of the product obtained from that log.

Width Comparison of Thinned vs Unthinned Trees

Width Comparison of Thinned vs Unthinned Trees. Photo credit Edward Neuhauser.

When sawing logs, it is the diameter of the small end of the log that will determine the size and amount of lumber that you can obtain from that log. The larger end of the log will all be sawn off in the 4 slab cuts that ideally also cut off all of the bark. When I saw for boards that are 10-feet long, I cut an 11-foot log to make sure I have 6 inches of trim on both ends of the lumber. So if I cut a 15-inch DBH (diameter at breast height) red pine, assuming a 1-foot stump, it is the diameter of that log at 12 feet that determines the dimensions of the lumber that I will be able to obtain from that log. A 15-inch DBH red pine log would result in the diameter of that log at 12 feet that would range from 11 to 13 inches.

In designing my shop, I decided that I wanted to use board and batten siding that was 1 inch thick. Then the question became: what size boards and battens could I obtain from the available red pine logs? The battens were easy to figure out; I decided that I would use battens 3 inches wide. These were readily obtainable from the first board cut in a log after the slab cut.

If you take into account the amount of wood that you have to take off in the slab cuts, a 10 to 12-inch diameter log on the small end will allow you to cut 8 inch wide boards. The red pines were about 70 to 75 feet tall, allowing me to obtain up to five 11 foot logs per tree, as it is characteristic of closely planted red pine to have long straight stems (of little taper) topped by short crowns. If the diameter of the small end of the 5th log on the tree was at least 6 inches, I could saw two 2” x 4”s from that log, for a total of 13.4 board feet (one board foot equals 144 cubic inches of wood; to calculate, take length x width x thickness, all in inches, and divide by 144 to determine total board feet).

I found that I could obtain some 10 inch wide boards from some of the larger diameter butt logs, but not very many. One problem with wide boards is that they can have a tendency to warp if they are not correctly placed on a wall. One way to minimize this problem is to follow the suggestion from barn builders of old: “Place the bark to the barn.” This means placing the outside of the tree towards the inside of the building. This way if the board warps, as some will, the cupping will not result in a split board.
So I ended up cutting primarily 8-inch boards, mostly from the butt logs, and some of the 2nd logs, and 1” x 3”s, 1” x 6”s, 2” x 4”s and 2” x 6 ”s from the rest of the logs from higher on the stems.

So how does this relate to the usefulness of the logs from plots of thinned and unthinned red pine? The red pine grown on the thinned plots had many trees that reached 15” DBH, with clear stems, while the red pines on the unthinned plot limited the DBH to 6 to 8 inches, and as these trees were never pruned, they were riddled with dead branch stubs, which further reduced their utility and value.

To demonstrate the value of thinning, I compared the amount of lumber obtained from the butt logs of 2 red pines of the same age, but the larger tree had more space (and its crown more access to sunlight) to grow. From the 10 foot log whose narrow end diameter was 10”, I obtained 2- 1”x 6”, 3- 1”x 8” and 2- 2”x 4”s, for a total of 44 board feet of lumber. From the log whose narrow end diameter was 12”, I obtained 3- 1”x 6”, 7- 1”x 8”s and 2- 2”x 4”s, for a total of 75 board feet of lumber. So I obtained 70% more lumber from a log that was only 2” larger in diameter (see figure 2). I also obtained 4 additional boards of the more valuable lumber, the 1”x 8”s. So the thinning that took place in the 1940’s really paid off when the stand was harvested and the logs sawn for lumber.

I would be lucky to get a couple of 2” x 4”s from the butt log of the trees on the unthinned plots, and probably would get little or nothing from the second log on these trees. While the red pine on the unthinned plots would be suitable for pulp, they really would not be suitable (or worth the effort) for lumber. So as my experience with these two stands demonstrates, thinning really does matter, as what happens early in the life cycle of a stand can have great consequences for the final value of its timber.
On a final note, one of the best benefits of New York Forest Owners Association (NYOFA) membership is the willingness of more experienced members to share their knowledge with others. Early in my sawing career, I was very fortunate to have a visit at my place from million board foot sawyer Dave Williams. Dave showed me in one afternoon how to get much more lumber from my logs, resulting in thousands of additional board feet of lumber since his visit, boards that would have previously ended up in the slab pile. It is NYFOA members like Dave that make NYFOA the wonderful organization that it is today.

Ed Neuhauser is a NYFOA board member who saws lumber in Groton, NY.