Forest stand improvement is a very common recommendation under forest management plans that we write, but what is their ecological basis? Forest stand improvement thinnings can take many forms. Most commonly they are either thinning from below or crop tree management.
By thinning from below foresters are seeking to mimic low- to moderate-intensity wildfires. Such wildfires were common hundreds of years ago and helped shape the forest that we know today. By favoring thick-barked species such as oaks and pine, such fires helped develop native wildlife and plant communities and were an important ecological process. Of course your insurance company would likely not be happy if you started flicking matches into the forest. But by cutting thin-barked species, especially those with smaller diameters, we can get the same outcome using a slightly different process.
Crop tree management is slightly different in that we specifically identify high-quality and or high wildlife value trees that we wish to retain on the property. Next we identify lower-value trees (either economic value or ecological value) that are competing with the trees designated to remain. Some of those trees that are directly competing with residual trees are designated to be cut.
Both systems are designed to increase the health and vitality of the residual forest as well as the individual trees designated to remain. Since many of the residual trees are oaks and other thick-barked species, these methods correspond well to the outcomes of light- and medium-intensity wildfires. When such thinning is combined with competing understory vegetation control, we also have the added benefit of improving groundcover quality and improving the chances for developing new seedlings and saplings that should become the next generation of trees as the older trees die off.
As once-far-away disease problems become resident in northern and central New Jersey -- such as emerald ash borer and bacterial leaf scorch -- we are further reminded that our forests are dynamic, disturbance-dependent ecosystems. They will change whether we like it or not. By following the ecological processes that developed these forests in the first place we have our best chance for keeping them healthy in the long term.