Landscapes and Forest Management
Guest Column Article for Alpena News
by Dr. Greg Corace of the Alpena-Montmorency Conservation District
October 31, 2019
This aerial image, taken by the author over northern Lower Michigan, shows a range of cover types: agriculture in the distance, different forest types in the foreground, a range of forest management strategies (including riparian buffer), and the interface between forest and water.
In my last article I mentioned the four foundations (or precepts) of ecologically-based forest management: 1) context—the importance of planning and management over larger areas of land (landscapes); 2) continuity—the maintenance of forest structure, function, and biota between pre- and post-harvest forest ecosystems; 3) complexity— the need to create complexity and maintain biological diversity; and 4) timing— the importance of applying forest management activities at ecologically appropriate time intervals.
In this article, I’ll expand on the concept of the landscape and the importance of landscape considerations in forest planning and management. What then is a landscape, how can landscapes be classified, and how does this information inform forest management?
Landscapes are very large land units. According to the International Association for Landscape Ecology, landscapes are often measured in 1,000s of square miles (hundreds of thousands of acres or more). As such, landscapes are best viewed and analyzed using aerial imagery and software such as Google Earth. In northern Michigan, the forests in our landscapes include publicly-owned lands managed by federal, state, and county employees as well as privately-owned lands owned by corporate and non-industrial private landowners. Landscapes dominated by publicly-owned forests tend to be less fragmented by other land uses compared to landscapes dominated by privately-owned forests. Rarely does any single land owner manage all forests within a given landscape.
In Michigan, the landscape classification scheme of Dennis Albert (1995, US Forest Service) classified landscapes based on their climate, geology (including soils), water (hydrology), and past and present vegetation. These landscape characteristics can impact the types of forests found in landscapes (think: “different shades of green”) and the types of treatments used to meet ownership goals and objectives. For instance, some landscapes are dominated by very wet (hydric) soils while other landscapes are dominated by very dry (xeric) soils. These soil characteristics can drive the ecology of forests and how they might be managed. Landscapes dominated by wet soils usually have swamp forests of northern white cedar, tamarack, and black spruce. Conversely, landscapes characterized by very dry soils are often dominated by a suite of very different (but still coniferous) tree species: Eastern white pine, red pine, and jack pine. Differences in landscape soil characteristics can also dictate when forest management might occur. On wet soils, forest management is generally confined to the coldest times of the year when frozen conditions allow heavy machinery to gain access to sites without being bogged down. On very dry sites, some foresters like to work during the growing season. Logging machinery can remove the very top litter layer on the forest floor and allow tree seeds to find their way to the top layer of the soil where they can germinate.
Landscape ecologists often use the term “patch” to describe any relatively uniform feature or land use that can be observed and measured on a landscape. These patches are what we see when we see different shapes and colors on aerial imagery. A farm field may be termed a patch as might a forest stand. For a visual here, think of a landscape as a quilt, with the individual blocks on a quilt being patches of land. Similar to the diversity of quilts that can be made by moving different-colored blocks around, the arrangement of patches on a landscape can influence not only how a landscape looks, but also how it functions.
Because some wildlife species with large home ranges may use different patches in different ways at different times of the year, how patches are arranged on a landscape can be important from a biodiversity perspective. In northern Michigan, white-tailed deer may move to certain patches on the landscape during the fawning season and to different patches during the overwintering season. The spatial arrangement of these patches can therefore influence deer movement. Moreover, because browsing by white-tailed deer can impact the regeneration of trees and other plants in our forests, activities that promote a larger deer herd on one patch can impact surrounding patches because deer move within and between the seasons of the year. And because many neotropical migrant bird species nest either on the forest floor or in the sapling layer of regenerating trees, deer browse can impact biodiversity in many ways. Therefore, one might say that management of the northern Michigan deer herd and many other wildlife species relies on landscape ecology principles.
In summary, landscapes are large units of land composed of individual patches representing a range of land owners and land uses in northern Michigan. The range of land uses found in landscapes is often a result of differences in soils and other landscape characteristics. These differences within and between landscapes can also make widespread application of some forest treatments difficult as timber markets, social acceptance of forest practices, as well as flora and fauna differ between landscapes.
Next: the concept of continuity in ecologically-based forest management.
Dr. Greg Corace is the forester for the Alpena-Montmorency Conservation District. Greg has spent the last 25 years publishing forest and wildlife research and conducting forest planning, management, inventory, and monitoring on public and private lands across northern Michigan. For more information, including sources used in this article, Greg can be contacted via email (greg.corace@macd.org) or via phone (989.356.3596 x102).
