IMPACTS ON VEGETATION are so small that only those species tolerant of shade and representing late successional stages can be perpetuated. In low density stands this cutting system may favor species of a less tolerant nature. Approximately 900 acres would be subjected to this harvest method under the proposed action. Commercial Thinning Commercial thinning, proposed for application on 15,225 acres in the JKS YUS, also opens the forest canopy but to a lesser degree than clearcutting or shelterwood cutting. Although understory vegetative growth may be somewhat stimulated, canopy opening is not generally sufficient to allow development of early plant succession. Commercial thinning promotes accelerated rates of wood production in uncut trees. Thus, commercial thinning may be viewed as accelerating natural succession. This impact is generally negligible, however, since all merchantable timber would eventually be harvested. 3.5.1.2 Yarding Systems Yarding is the movement of felled timber to a control point from which the logs are loaded onto a truck. Based on past timber sale contracts within the planning area, it is estimated that approximately 65 percent of the proposed harvest would be yarded by cable methods and 35 percent by tractor. Both cable and tractor yarding entail dragging logs across the forest floor. Logs are constantly in contact with the soil in tractor yarding, whereas with certain cable yarding methods the logs are suspended above the soil for most of the way to the landing. Tractor yarding, therefore, causes greater proportional mortality to forest floor vegetation than cable yarding. According to studies reported by the Environmental Protection Agency (U.S. EPA 1973), tractor yarding following clearcutting in western Washington resulted in baring 26.1 percent of the site to mineral soil. If this relationship is applicable to the JKSYUs, approximately 365 acres can be expected to be completely denuded of ground vegetation by the proposed action. U.S. EPA (1973) also reports that high lead cable yarding in conjunction with clearcutting bared 12.1 percent of the site to mineral soil. Application of this data to the JKSYUs indicates that approximately 315 acres would be made bare of ground vegetation by clear cutting followed by cable yarding. By assuming that the regeneration cut of a shelterwood system (which removes up to 60 percent of the forest canopy) results in only 60 percent of the soil surface impacts of a clearcut, it is estimated that regeneration cutting followed by tractor yarding would bare approximately 1,490 acres. It is further estimated that regeneration cutting followed by cable yarding would bare approximately 1,280 acres. The shelterwood final harvest cut (which removes the remainder of the canopy) in conjunction with tractor yarding is estimated to remove all the ground vegetation on approximately 1,200 acres. Shelterwood removal in conjunction with cable yarding is expected to bare the soil on approximately 1,030 acres. In total, both yarding systems are expected to contribute to the total removal of approximately 5,000 acres of surface vegetation due to shelterwood harvest in the JKS YUS over the 10-year life of the proposed action. Depending on the severity of subsequent erosion, the majority of the denuded areas can be expected to naturally revegetate within 1 or 2 years. Both yarding methods may injure standing trees, exposing them to insect or fungus infestation which may eventually result in death. Tractors, or the logs being dragged by them, may collide with trees, bruising or slashing them. Logs suspended from cables may slip or swing into standing trees causing upper stem or crown injuries. The extent of mortality or injury to trees is impossible to estimate but is expected to be minor. Alteration of plant habitat is a function of soil disturbance and the destruction of vegetation which previously grew on the disturbed site. Skid trails and vehicle tracks, in addition to destroying vegetation, compact the soil, reducing its suitability for certain species of plants and favoring the invasion of species tolerant of compaction. Yarding activities, especially tractor yarding, disturb forest litter and expose bare mineral soil, creating a better seed bed for many species (including Douglas-fir and most other conifers). Conifer reproduction, therefore, is enhanced by yarding activity, especially if associated soil compaction is not too great. Skid trails often serve as channels for overland runoff and may reduce moisture infiltration on slopes. Therefore, less moisture is available for plants near the upper ends of these trails, whereas plants at the lower ends of the trails may receive a disproportionate share. Depending upon topography, overland flow may impound at the lower ends of skid trails, creating temporary pools, or it may flow unimpeded into streams. In the former situation some vegetation (especially herbs) may be lost because of inundation while water-loving ephemerals may become established in the temporary pools. In the latter situation moisture stress may develop in the upper drainages, and gullies created by overland flow may cut to bedrock and remain unvegetated. 3.5.1.3 Road Construction and Maintenance Construction of new roads is expected to add approximately 375 miles of road to the current network in JKSYUs. This construction would amount to approximately 1,770 acres. Many discrete impacting operations are associated with road construction and renovation. They include operation of tracked and wheeled vehicles, blasting, excavating, deposition of overburden and water IMPACTS ON VEGETATION application. All of the impacts are long term and are expected to persist until roads are abandoned and rehabilitated. Most of the roads to be constructed within the JKS YUs would be permanent with all-weather surfacing. This type of road requires construction techniques which completely eliminate vegetation from the roadway and shoulder. Subsequent maintenance activities prevent natural succession. Therefore, initial construction eliminates the existing vegetation while traffic and regular maintenance prepetuate the impacts of construction. The ultimate impact of road construction and maintenance would be complete elimination of biological productivity (including timber production) on the entire 1,770 acres devoted to new road construction in the JKSYUs and prepetuation of this impact for the time that these roads remain under maintenance. In addition to elimination of roadway vegetation, construction and maintenance may injure or kill adjacent vegetation. This effect could occur from bruises due to machine operation or from herbicide overspray along road shoulders. Road construction severely alters plant habitat both on-site and off-site. Soil compaction within the roadway is usually so great that many years would be required for plants to recolonize, even if there were no traffic or maintenance. Road surfaces are pitched to allow drainage. As water drains from the roadway and off the shoulders it creates moist soil conditions and provides habitat for plant species tolerant of disturbed soil and periodic excesses of water. Removal of vegetation from the roadway provides increased sunlight for roadside plants, which generally accelerates their growth in response. These factors (increased moisture, soil disturbance and increased sunlight) are often responsible for the rank growth of roadside "invader species" which are periodically removed by herbicide treatment or other maintenance. Blasting and excavation for roadways often generates spoil materials which are unsuitable for construction use or are in excess of needs. These materials are often deposited in areas away from the site. This practice creates a potential adverse impact to off-site vegetation which may be injured or completely covered by the deposition of overburden. 3.5.1.4 Development Practices Development practices are carried out to reestablish trees on forest land following harvest or natural catastrophes and ensure satisfactory or optimum growth. Individual practices are not necessarily used simultaneously, neither are they usually all applied to a single area. Many of the practices provide alternative methods, the choice of which is dependent upon the conditions of the area. Gross Yarding Gross yarding is an intensification of a conventional yarding method. As such, the effects of the vegetation and resulting impacts on the forest environment would be an extension of those analyzed under Section 3.5.1.2 Yarding Systems. Approximately 33,000 acres of logged sites would undergo slash removal by gross yarding if the proposed timber management plan is implemented. Assuming that gross yarding would bare about 15 percent of the treated acreage, it can be speculated that approximately 4,950 acres would be bared by gross yarding. Slash Burning Slash disposal by burning would be practiced on about 23,700 acres. The effects of burning would be short term and limited to small areas. While the chance of wildfire would be present, State and BLM safety measures would reduce the hazard. Conifer and other plant seed could be destroyed or made sterile by the heat from the burning. Some plants, such as most grasses, have growing points that are close to or below the ground surface and can survive all but the hottest fire. Many shrubs have the ability to resprout from surviving stumps and roots and are stimulated by fire. So, while the immediate impact of burning would be bare, black ground, secondary succession (accelerated by the crown canopy removal) would produce a more vigorous vegetative cover than existed before the area was burned. The burning and deposition of ash and the resultant changes in soil moisture relationships, nutrient availability and soil temperatures would alter the structure of the original understory plant community. Scheduled replanting of coniferous seedlings in the seedlings in the area would contribute to the alteration as a fire-induced plant community became established. Threatened or endangered species could be lost to the community. Scarification Scarification completely removes woody shrubs and removes or injures many plants in the herbaceous layer. Impacts resulting from scarification are expected to be short term. Threatened or endangered species could be killed or damaged. Soil moisture relationships would be affected by the break-up of the soil surface and the intermingled surface organic matter. The disturbance of the soil would affect the availability of nutrients to the detriment of some species and the favor of others, due both to the physical mixing and to the changes in soil moisture relationships. Removal of vegetative material, which through a death and decay process ultimately would have become recycled nutrients for new plant growth, would result in a loss of nutrients. IMPACTS ON VEGETATION Sudden removal of the lower canopy and shrub canopy would allow more light to reach the herbaceous layer, releasing those species to achieve their full photosynthetic growth potential. Increased exposure to sunlight would also affect soil temperature, which in turn affects soil moisture relationships and a large range of biochemical reactions. Soil temperature increase would generally favor increased soil microbial activity and increased plant growth up to a point, beyond which any temperature increase would severely limit plant growth, especially by newly germinated plants or planted seedlings. The primary impact of scarification upon forest vegetation would be a change in the structure of the pre-existing community. This change could mean total loss or reduction in quality of habitat on the site for affected species, including any threatened or endangered species present. Under the proposed timber management management plan, approximately 22,300 acres would be mechanically scarified before replanting. Chemical Vegetation Control (Herbicides) Herbicides are used to manipulate the species composition, size, density, vigor and presence of of vegetation. In forestry applications, the desired effect is acceleration of plant succession from early successional stages to later stages dominated by conifers. This acceleration occurs by selective limitation of competition from plants characteristic of early stages in favor of rapid Douglas-fir establishment and growth. Herbicides would be used in the JKSYUs both for site preparation (on 17,540 acres) and conifer release (12,150 acres). Both applications are targeted at the removal of nonconiferous species to provide a competitive advantage for conifers. Different herbicides work best for different target species and herbicides are often used in combination. The direct vegetational impacts of silvicultural herbicide treatments are short term. Grass may be controlled for only 1 to 3 years with atrazine and dalapon while conifer seedlings become established. Grass may then partially reoccupy the site until Douglas-fir crown closure shades it out. Similarly, many species of shrubs will resprout after treatment. Brush may resume dominance after site preparation spraying. However, it will generally not resume dominance after stand release spraying. Therefore, the net short-term impacts of successful site preparation spraying in the JKSYUs would be a temporary reduction (of unquantifiable magnitude) of the natural productivity of grasses on approximately 3,600 acres proposed for stand release treatments with atrazine and/or dalapon. In addition, natural production of forbs and shrubs would be reduced on approximately 8,300 acres to be treated for stand release. A temporary reduction in the natural productivity of grasses, shrubs, and herbaceous species would be expected on approximately 8,300 acres proposed for site preparation spraying with dalapon and atrazine. Temporary productivity reductions for herbs and shrubs would be anticipated for all 16,560 |