Trail Cutting and Maintenance Guidelines
Northern Hardwood Forest Type
Northern hardwoods is a diverse forest community whose species composition varies with geography. This discussion will focus on mountains in northern New England. Northern hardwood forests occur on the mid and lower elevations of northeast mountains. Unlike spruce-fir which grow through their life cycles together, northern hardwood forests tend to be uneven-aged.
The defining species in all northern hardwood types is Sugar Maple (Acer saccharum). Also prominent are Yellow Birch (Betula alleghaniensis), Paper Birch (Betula papyrifera), American Beech (Fagus grandifolia), Stripped Maple (Acer pensylvanicum), Balsam Fir (Abies balsamea), Red Spruce (Picea rubens), Mountain Ash (Sorbus americana, and Mountain Maple (Acer spicatum). At lower elevations, Eastern Hemlock (Tsuga canadensis), Red Maple (Acer rubrum), and Eastern White Pine (Pinus strobus) are found. An understory shrub, Hobblebush (Viburnum alnifilium) is a dominant nuisance species for skiing and riding.
Northern hardwood forests offer the best opportunities for ski terrain development because the soils in mid and low elevations are more stable than in upper elevations, the uneven-aged growth regime offers numerous regeneration options, and these forests can tolerate much more human impact than spruce-fir forests. Regardless of forest type, the themes of snow retention, regeneration, and soil loss apply.
Maintaining the Edge
Regarding retention of natural snow, spruce-fir forests retain their foliage all year, and the ability of these forest edges to catch and hold snow is much greater than that of northern hardwood forests. Northern hardwoods are predominantly deciduous, dropping their leaves in the fall, and so its "snow fence" function is not as robust as with spruce-fir.
Annual mowing of trails right up to their edges does not allow young trees to grow, and as the mature trees defining the edge die, trails can slowly become wider ("edge creep"). Ski trails are not golf courses, and they should not be maintained like golf courses either. The forest will rapidly fill in unmowed areas with seedlings. Therefore annual mowing plays a pivotal role in selecting replacements for existing trees, where new trees will grow, and the shape of the trail in the future. This is a simple practice with far-reaching effects.
Trails are breaks in the forest, and abundant sunlight reaches the forest floor along their edges. A dense wall of undergrowth and young trees results. Trees compete with one another for sun, water, and soil nutrients, and they will grow tall as they reach for the sunlight. But being in dense groups, their stems remain relatively thin and pliable. Managers can select and "release" well-formed, vigorous trees by cutting competing vegetation from around them. Without the competition, selected trees will start growing laterally and their height gains will slow. Lateral growth is both of branches, and thickening of the main stem. This makes for stronger trees that will be able to withstand the rigors of wind, snow, and human activity as they grow and become the dominant trees of the trail edge. It is important to bear in mind that the practice of releasing selected trees thins the trail edge, but when done judiciously, snow retention functions are not compromised.
Another edge issue regards sections of forest that divide adjacent trails. As the width of forest dividing trails decreases, the ability of that forest to catch and hold snow becomes increasingly tenuous, especially with northern hardwoods because they are deciduous. Managers should keep a close eye on relatively narrow sections of forest dividing trails. If the sections start taking on a thin look - defined as decreasing numbers of stems per acre - then measures should be taken to halt the trend. These include discouraging skiers and riders from using these areas, leaving unmowed buffers along trail edges, and selected release of any spruce and fir present.
Islands are Essential
If the management goal of a trail is to keep it entirely open and devoid of trees, then maintenance of the edges and erosion control are the management focus. But for glades and woods lines, the management goal is to maintain a degree of forest cover in and over the trail. Since northern hardwoods are generally uneven-aged, maintenance of forest cover (not allowing the glade or woods line to morph into an open trail) is a question of maintaining a growing stock of younger trees within the trail to replace the mature ones as they die. This is most effectively accomplished using islands.
"Islands" are uncut areas within trails composed of brush (understory shrubs) and trees of various ages. In order of decreasing importance, islands serve three functions:
In response to the burgeoning woods skiing/riding popularity, many ski areas cut glades and put them on trail maps. Using the golf course mentality, the forest is manicured, removing all vegetation under a certain stem diameter, six inches for example, over a wide area. A park-like aesthetic results. If annual maintenance keeps all vegetation in check, then glade will evolve into an open trail. Since glades tend to be cut wider than open runs because of the remaining trees, the risk of decreased snow retention and land slides is magnified. Big, wide, park-like glades are very unhealthy from a silvicultural standpoint.
Fortunately the solution is low-tech: When cutting glades and woods lines, leave interspersed islands of brush and young trees. The glade or line will have an untidy, less defined look, but islands provide the regenerative base to sustain the glade or woods line. While large trees may be in islands, the goal is to have young trees growing in these islands. Young trees are defined as trees are vunerable to being killed by skier/rider traffic, or less than five inches in diameter at chest level.
Why leave islands that take up more room and look messy instead of individual young trees? The reason is that individual trees will be steadily mangled and killed by skier/rider traffic, such as the red spruce sapling to the right. Work at Mad River Glen has clearly demonstrated that individuals left alone are doomed, especially in woods lines. Conversely, when trees are left in groups as islands, the outer trees protect the inner ones. Trees on the perimeter are sacrificed so the inner ones can grow to a size where they are immune to ski/board edge cuts, and in collisions, the humans loose.
The need for leaving regeneration in islands is the same for both official glade trails and woods lines, except that woods lines are, by definition, supposed to be more like a forest. Sustaining the elemental experience of skiing and riding in the woods requires lines that are less tame, more irregular, with plenty of regenerative capacity.
When laying out a glade or woods line, remember the rule that the result must be fun to ski and ride. Islands should compliment the flow of the terrain and the rhythm of turns. This is especially important for woods lines which are narrower and less clean than official glades.
Elevation, air pollution, and the regenerative cycle of spruce-fir combine to make upper elevation forests the most diffcult place to maintain ski terrain with minimal environmental degradation. It can be done, but management options are limited to narrow trails without snowmaking, or wider ones with snowmaking. Glades in spruce-fir are not sustainable, and woods terrain maintenance is problematic. Ski areas with greater proportions of spruce-fir forest must look to the mid and lower elevations for ski/ride terrain development of all kinds where at least the impacts weather and pollution are minimized.
In contrast, northern hardwoods tend not to grow at upper elevations, are uneven-aged, grow faster, and occupy more stable terrain. Therefore northern hardwoods offer the greatest management flexibility to create sustainable tree skiing and riding. The caveat is that in northern hardwoods, managers must be much more vigilant to guard against snow retention degradation through incremental loss of tree regeneration.