Soil
Compaction and Rutting
Operating any logging equipment, including horses and so-called “light-on-the-land”
logging equipment has the potential to damage woodland soil resources
by causing compaction and rutting.
Compacted soil resists absorption of water, restricts movement of air
around the roots, and produces a physical barrier to the development of
roots. The combination of these factors can significantly decrease tree
growth. Rutting restricts the movement of water through and across the
soil profile making the rutted area too wet to grow trees and robbing
the surrounding areas from moisture they would otherwise receive. More
importantly, rutting cuts the surface roots of trees, which are the roots
that provide trees with the vast majority of their nutrients and moisture.
Wet soils are considerably more prone to compaction and rutting then dry
soils, and medium texture (loamy) soils are most prone to permanent compaction.
The easiest way to minimize compaction and rutting is to operate logging equipment only when the ground is fully frozen. This is why winter is the busiest logging season, so it can be difficult to acquire the services of loggers during the winter, particularly the most reputable loggers. Also, because winter is the busiest logging season, some mills experience seasonal shortages of wood during summer, so logging that can safely occur during the summer can often yield a landowner significantly higher stumpage values. Furthermore, some compaction and rutting can occur even during winter, so provisions to minimize soil damage are a critical component of any logging contract. Jim and Marlene Zdanovec learned this lesson the hard way. If you can get either Jim or Marlene out of the woods long enough to tell you this story, you will be able to clearly hear the regret in their voices. In their first venture into clearcutting aspen, the Zdanovecs contracted with a mill to bring in a sub-contracted logger to cut their wood. Without direct contact with the logger, their wood was cut in the spring when the ground was soft and wet. Once all of the money had already changed hands, the Zdanovecs realized that the rutting was so severe that all of the aspen roots had been severed and no aspen was going to regenerate.
A common mechanism for minimizing compaction is to restrict the abundance of skid trails across a site. Skid trails are the travel routes that logging equipment use to move around a stand. Some specifications on skid trail layout can be outlined in a logging contract, but, at the very least, a logging contract should specify a maximum skid trail width and a minimum distance between skid trails. This approach will concentrate compaction onto these defined trails, but will also restrict the prevalence of compaction across the site. Many woodland owners develop trails for recreation in advance of any logging operation, and these trails provide an excellent opportunity for skid trail location. Some people argue that not restricting traffic to skid trails and asking the contractor to try to produce an even impact across the entire ground surface of a site can manage compaction better than a defined system of skid trails. However, the majority of the negative impacts from compaction occur from the first pass of heavy equipment, so this strategy of dispersing the impact will typically have a larger cumulative negative impact on the productivity of the site. Fines per linear foot for length of skid trail that is too close to a neighboring skid trail is a common tool to enforce these contract limits.
Contract provisions for fining per linear foot of ruts in excess of a specified limit is a common tool used to minimize rutting. Some contracts contain provisions that define the physical characteristics of a rut in detail, particularly definitions of the minimum depth to classify as a rut. Then these contracts detail restrictions on the maximum cumulative length of rutting acceptable across a logging job. While rutting is highly undesirable, a small amount of rutting is sometimes unavoidable, so these types of limits are typically more practical than a complete ban.
Another common tool used by landowners to limit soil damage is to restrict the types of equipment that can operate in their woodlots. Pole skidders, iron mules, and bulldozers are commonly used in logging to pull trees from the woods, but these machines are not designed to be light on the land. These types of logging equipment are best used during the season of fully frozen ground or on sites with very light sandy soils. However, there are newer logging technologies being developed today that can remove large amounts of wood while producing minimal soil compaction. Some high-flotation wheeled and tracked forwarders that lift and carry the wood off the ground and carry it out in a bunk can produce a footprint on the ground that is lighter than a walking person. Timber processors can also be used which limb the trees and spreads the slash in front of them, which significantly reduces the impact to the soil as this equipment travels across the slash.