Can Cutting Your “Junk Trees” Power Your City and Improve Your Forest?

How managing low-use wood for bioenergy can incentivize sustainable forest management.
Can Cutting Your “Junk Trees” Power Your City and Improve Your Forest? - Articles


Consider how you work in your forest. When you select a tree to cut for firewood, rather than a large, straight tree of a desirable species, you would likely choose a smaller tree with a crook or Y that shows signs of rot at its base. The value system we place on individual stems in our forests is rather intuitive, based on the way we use different kinds of stems and the services they provide. A tree's value depends on several factors including its species, size, form, condition, quality, function, and accessibility, and depending on the management goals for a given forest, the same tree can be valued very differently by each person who looks at it. A large, straight black cherry has high value as a sawtimber or veneer tree, but for a landowner more interested in wildlife habitat, the real value of that stem may be the food it provides to animals. Likewise, if the tree exhibits black knot, its value for timber decreases, but to a woodworker interested in bowl turning, it brings an opportunity for a unique and beautiful piece of art.

In the past, Pennsylvania landowners were primarily interested in the timber value of their trees, and with a singularly focused value system, the norm was to remove the stems of highest quality and leave behind poorly formed trees that were not as well suited to the site where they grew. This practice, called "high-grading," has left a legacy of "low-use wood" in our forests. Some people even call these "junk" trees, and they are abundant in Pennsylvania. In fact, about 57% of the wood in Pennsylvania's forests is considered low-use wood, and about 73% of that material is on private land. These trees often have lower economic value for traditional timber markets, compete with higher-value trees, shade out desirable regeneration, decrease the health and vigor of a stand leaving it more vulnerable to disturbance, and perpetuate poorer genetics in the seed bank due to past high-grading. Management that specifically targets low-use wood can help landowners manage these forest health issues, and wood energy markets are an excellent driver for that.

Wood energy markets, like other low-use wood markets including pallets, pulp, mulch, OSB, plywood, particleboard, wood shavings, etc., can accept wood material of lower quality than would be suitable for traditional timber markets. Most wood used for energy in Pennsylvania is used to produce heat or electricity through combustion. Many schools and hospitals use wood boiler systems to heat and power their facilities, many homes are primarily heated with wood, and some coal plants incorporate wood into their coal streams to produce electricity. Wood pellets are also a familiar wood energy product in Pennsylvania. Wood can also be gasified to run turbines for electrical generation and can even be made into liquid fuels like ethanol and gasoline. All of these markets are fed primarily by low-use wood. Several cutting options that could greatly improve the long-term quality of your forest focus strongly or solely on the use of this material and therefore depend on those markets.

One such cut is a timber stand improvement (TSI) cut. Think of this almost like the opposite of a highgrade. In a TSI cut, poorer-quality material is removed to allow more space, light, and other resources to the highest-valued stems that remain. Invasive plant removal might be another primary goal of a TSI cut. As the residual stems thrive, they might grow in size to increase in timber value, develop larger crowns to produce more mast for wildlife, or have a better chance to regenerate in a less crowded understory. TSI cuts can be tailored to one person's specific management goals for her land.

Another example of a cut that might yield a high amount of low-use wood is a salvage or sanitation cut. With the many pests and pathogens visiting our forests including hemlock wooly adelgid, emerald ash borer, Asian longhorned beetle, beech bark disease, and gypsy moth to name just a few, it is important to remember that foresters can help mitigate these issues through cutting procedures. These types of cuts reduce the number of infected trees, seek to manage the future spread of a pest problem, encourage stump sprouting on cut stems to encourage regeneration, and offer an expert eye toward vigorous stems that should be retained to make sure the species continues to be represented in the stand, either by staying healthy enough to survive the disturbance or by producing good quality seed.

Even some more traditional, sawtimber-centric cuts can produce a lot of low-use wood. In a shelterwood cut, for example, the first cut removes most of the low-use material and smaller trees, leaving a low density of high-quality stems to increase in size and produce enough seed to ensure good regeneration. When enough regeneration present, the final cut can safely remove the largest stems while ensuring that a good crop of trees will grow back on the site. In such a treatment, the first cut is mostly lower-value material, but having a market for this material can help float the cost of that early intervention that is necessary for achieving higher returns on the final cut and the assurance of good regeneraton.

These are just a few examples of management options; thinnings, dense and dead wood removal for fire prevention, and many other cuts also center on low-use wood. However, it is important to remember that some retention of what many would classify as low-use wood is very important. Tree tops left from a cut should stay on the site to help nutrients cycle back into the soil. Dead snags, downed logs, and "wildlife trees" with many branches, cavities, and flaking bark are extremely valuable not just for game species but also for insect predators like woodpeckers, bats, and small mammals that help control problem insects and increase the health and resiliency of your forest. Remember too that not all small trees are low-use. Many understory species like dogwood and hawthorn provide important structural diversity and food for wildlife. Rare species that might be underrepresented in your stand should stay behind. A few conifers can provide thermal cover for wildlife and add to structural diversity in the stand as well. Working with a forester can help you prioritize what to retain.

So what should you do as a landowner with this information?

  • Think carefully about your values and goals for your forestland. Write down your top priorities and think often about this list.
  • Understand how low-use wood on your land works for or against those priorities.
  • Hire a professional forester to inventory your forest and recommend a management plan that fits your priorities.
  • If cutting low-use wood is a major part of this management plan, expect ups and down in demand. Some of the markets for low-use wood can be volatile. Be flexible in scheduling cutting activities.
  • Take a long-term view of your forest as an investment and as a legacy. Know that a low-use wood cut might make little or no profit in the short term but could add value to your forest in the long term.

To educate yourself more on the place of wood energy markets in your forest management plan, check out a few resources on this topic, especially "A Primer on Woody Biomass Energy for Forest Landowners." You can also contact your local extension office for guidance on this and other natural resource questions.