In order to make any decisions about how best to manage a property, one needs to first figure out one’s starting place. This piece is going to focus on the particulars of the Farm, and use this information to say a bit about bigger ideas about sustainable forestry. The main ideas that we are trying to communicate here are about determining what sort of wood products could be sustainably harvested from this property while maintaining healthy ecosystems overall.
At our farm, we have a relatively healthy second-growth forest. A second-growth forest is one that has been heavily cut for timber, and generally has smaller trees and more of those species that respond well after forest disturbances. The Manitou property has been logged several times over the last 150 years, most recently in 2008. The property has probably never been clear-cut, but has instead been ‘high-graded’, where most of the larger and more valuable trees have been targeted in successive passes of cutting while leaving behind less desirable trees. Unfortunately, high-grading is extremely common throughout many forested areas. Timber cuts actually bring a greater diversity of tree species in this area, as all sorts of light-loving trees have been able to flourish after cutting, whereas in undisturbed old-growth forests it is mostly only those trees that can grow up in partial or full shade that thrive.
The property is almost 150 acres, consisting almost entirely of hilly terrain. About 110 acres of that is well drained forested hills. There are about 20 acres of pastures dominated by perennial grasses. Another 10 acres are made up of relatively steep riparian (shoreline) areas that tend to be dominated by balsam fir and other conifers. Finally, there are perhaps 10 acres of wetter terrain, including a stream that feeds into a several acre wetland, along with several forested depressions that have seasonal ponds (known as vernal pools). The highest point on the property is 630 feet above sea level and the lowest points are along the shore of Manitou Bay at 493 feet, giving 140′ of elevation change over the property.
We can also mention a few of the other key characteristics that help define this property. We live in a ‘cold temperate’ or ‘continental’ climate, which is one that has a combination of long, cold and snowy winters accompanied by hot summers. We are in the plant hardiness zone 4b, where winter temperatures usually get no colder than -35 degrees Celsius (-30 Fahrenheit). The area receives about 90 cm (35 inches) of total precipitation, with a portion of that coming down as 200 cm (80 inches) of snow. These temperature and water patterns have enormous influence on which species inhabit the region.
The most common way that a forest is evaluated for it’s wood products potential is by making a forest inventory. One goes into forest stands and takes measurements of trees using some specialized sampling techniques, which allows one to have a good understanding of what is there even though you may only actually measure 1 or 2% of the trees. Most of the time what foresters are really interested in is the total volume of wood in a forest, because this is what determines how much lumber or paper could be made from it. This is really quite hard to measure directly, so most of the time they use a much simpler proxy, diameter at breast height (dbh). Just by going around and measuring some trees at four and a half feet off the ground, a good estimation of a total forest can be done. The final measurement that foresters use to decide what and when to cut is called ‘basal area’, which is the cross-sectional area of all the trees at breast height – imagine that all the trees were cut off at chest height and add then together the surface area of each of those tall stumps on a given piece of land. We created a forest inventory for the Manitou in 2012, and some of the results can be seen in the following tables.
|Aspen (several different species)||10|
|Other species: Black ash, Green ash, American beech, Black cherry, Rock elm, Butternut, Eastern white cedar, Eastern white pine, Red pine, Eastern hemlock||7|
This single property contains almost all of the native tree species present in the region. Sugar maple makes up a quarter of the forest, with many other species each making up 7 to 10 percent. So we have a very diverse forest, which is not uncommon in this area as most of the neighboring properties have similar topography and history of both natural and human impacts.
So that covers which species are present, but how big are the trees that we have? Tree size is tremendously important for making wood products, and bigger is usually much better. This is why loggers fight so much to get into remaining old-growth forests, as their value is immensely higher than younger forests. Bigger trees can be used for some higher value products that can’t be made from smaller trees, and also it takes much less time and effort to cut a few big trees rather than many small trees for the same amount of wood. The Manitou, like a great many forests across North America, has had loggers preferentially taking those bigger and more valuable trees while leaving the rest. This leads to size distributions like we have, as seen in the chart below.
This chart shows the amount of trees we have of various sizes, and contrasts that with the typical forestry best practices for our area. The takeaway is that we have far too many small trees, about the right amount of medium sized trees, and not nearly enough large trees.
The above graph shows the proportions of trees by basal area, which is a pretty good measure of total wood weight and volume, but it doesn’t say anything about the number of trees. Most people don’t look at trees and think about basal area, or board feet, or other forestry measurements, they think more about individual trees. It is not usually worthwhile to count the small saplings in a forest as there can be many thousands per acre, so it is usually only those that are 4″ or more in diameter that are counted. Our sampling estimated that on each forested acre there 257 trees from 4″ to 8″, 55 from 10″ to 14″, and only 6 over 16″ in diameter. Extrapolated out to the 130 forested acres, there are about 40,000 trees bigger than 4″ on our farm.