|
The soils of the Swan Valley are shallow and rich in clay, making them prone to compaction and erosion when disturbed by vehicles and heavy equipment. Once disturbed in these ways, the soil's ability to support vibrant forests over the long term is compromised.
While many of our tree species are able to germinate in compacted soil, tree roots need loose, crumbly ground to access nutrients and sustain growth over many decades. Our soils contain a network of fungal life that enhances nutrient absorption. When this fungal network is disrupted through soil disturbance, trees lose an important ally in the underground ecosystem.
Erosion sends valuable soil into streams, harming aquatic life. Fish, such as bull trout and westslope cutthroat trout, need oxygen-rich water for survival, and clean gravels for spawning. Siltation from eroding clay smothers eggs and depletes oxygen.
Many native understory plants are unable to compete with the noxious weeds that thrive on recently disturbed, degraded soils. Preventing soil compaction and erosion may be the most effective method of controlling noxious weed invasions.
Organic material in the form of dead, fallen trees replenishes soil. Nutrients from decaying trunks, branches, needles and leaves on the forest floor are returned to the soil, ensuring continued productivity. Rotting logs provide a "nursery" for saplings. Organic matter created from decomposing logs and forest litter, added to mineral soil and volcanic ash, combine to make our most productive soils in the valley bottom.
The Swan Valley has three basic types of land forms:
• Our subsurface rock is primarily shale and quartzite, which breaks down to form the mineral components of our soil.
• Erosonial soils -- fine silts (clay) and course sands and gravels -- are often found on the mid-slopes. Running water causes erosional soils to slide from the surface, unless they are held in place by roots and rocks.
• In the valley bottom, the soil is mostly depositional,formed by movement and settling. This includes clay, sand and gravel, transported by water. Volcanic ash, carried on the wind from the eruption of Mount Mazama (Crater Lake) and other volcanoes, is also depositional.
TIPS FOR LANDOWNERS
• Maintain a thick cover of vegetation to prevent erosion.
• Maintain adequate tree canopy to contribute future fine litter and down woody.
• Near home sites, protect habitat on the forest floor for soil building microorganisms and small animals by leaving about 8 tons per acre of woody debris that is 6 inches in diameter or larger. Farther from home sites, you can leave more, with 15 tons per acre being the ideal.
• Leave as much slash as feasible according to State fuel hazard guidelines.
• Except near home sites where slash would be a fire hazard, leave green slash for one year to allow the nutrients to leach out into the soil.
• Work only when the soil is dry, frozen, or snow-covered. If trenching or mud is detected, or if soil forms a ball in your fist, it is too wet.
• Minimize vehicle travel.
° Limit skidder/forwarder trails to 100 feet apart, except where they converge at junctions or landings. Maintain narrow trails.
° Protect the litter and duff, and the shallow surface soils, by limiting bulldozer use.
• Where feasible, harvesters should work from a slash mat created by placing slash in front of the vehicle and setting the vehicle up on it.
• Select experienced logging contractors who know when, where and how to operate their equipment to minimize soil disturbance.
• Work with a forester or other natural resource professional when planning forest management activities to obtain recommendations on how to minimize soil disturbance.
|
