Long-Term Soil Productivity
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Long-Term Soil Productivity Detrimentalcompaction in volcanic ash and pumice soils is an increase in soil bulk density of 20 percent Soil is a basic nonrenewable resource. The or more over the undisturbed level. In other soils, demands for sustained timber production create an increase in soil bulk density of 15 percent or a need for maintaining long-term soil productivity. more over the undisturbed level, a macropore The ability of soils to remain productive depends space reduction of 50 percent or more, and/or a largely on the management practices that are reduction below the 15 percent level as measured allowed. Future management will likely include by an air permeameter. shorter rotations of timber, the use of mechanical timber harvesting equipment and more complete Displacement utilization of woody residues The effect of repeated activities, over a long period of time, has the Soil dsplacement is the horizontal movement of greatest potential of lowering forest soil productivity. soil from one place to another, triggered by The maintenance or enhancement of the soil mechanical force such as a tractor blade Regional resource is a primary goal of management standards define soil displacement as detrimental when more than 50 nercent of the toosoil or The components of long-term soil productivity humus-enrichedAI and/or AC horizons is removed have been identified as the preservation oP from an area of 100 square feet or more which is at least 5 feet in width 1. Suriace litter and topsoil layers; 2 Soil organic matter and its replacement; Burning 3 Soil organisms and biological systems; and 4. Soil porosity, structure, drainage and aeration. Soils are considered to be severely burned when the top layer of mineral soil has been significantly The goal is to maintain or enhance soil productivity changed in color, usually to red, and the next This directs the Forest Soil Program to measure, one-half inch blackened from organic matter quantify and evaluate the effects of management charring by heat conducted through the top layer. activities on the natural capacity of soils to heal after disturbances The Forest-Wide standard/ Erosion guidelines for soils as well as FSM 2521 R6 supplement No.50, June 1987 provide a basis Surface erosion is the detachment and transport from which to measure these changes. of individual soil particles by wind, water or gravty. Surface erosion occurs as the loss of soil is a Compaction fairly uniform layer across the land surface or in many small rills. Soil compaction is an increase in the soils bulk density and a decrease in its porosity, resulting In summary, the prevention of soil damages before from the application of mechanical forces such as they occur is better than trying to rebuild productive weight and vibration. It usually reduces the capacity. In the past, the Forest tried soil moisture productivity of the land (Helms, 1978; Froehlich, as a critera to control ground skidding equipment. 1972 and 1979; Meurisse, 1978). Air and water In certain situations it is very effective, but may movement into and within the soil affect biological have limited success because of naturally varying activity, and ultimately nutrient availability neces- soil moisture levels within a sale area. The current sary for vigorous plant growth. Changing soil emphasis is toward a 'fixed ground skidding" properties through human activities that induce network designed to concentrate the machine compaction, puddling, erosion, displacement and disturbance within allowable levels. Where lands mass movement (Boyer, 1981) will lower the sites exceed tolerable levels of soil damage, reclamation ability to produce. In particular, soil compaction measures are warranted. These include tillage of on many Sites has led to decreased water infiltra- compacted soils, back blading of mounds or tion, accelerated erosion of topsoils, damage to berms, fertilization, or spreading of biologically soil biological systems and reduced seedling rich organic materials to rebuild the organic matter growth (Cochran and Brock, 1985). levels EIS 3 - 7 Water good shape and exhibit little of the traditional problems associated with cattle grazing6 (loss of Streams cover, channel widening, loss of banks) Stream temperatures are cold, outflow from spring vents The Deschutes is a remarkably forgiving Forest, is characteristically between 40 and 45 degrees slopes are gentle and soils are very porous'. Fahrenheit and downstream temperatures rarely While there are localized road erosion problems, exceed 70 degrees7. Best management practices there are very few documented instances of are used to maintain streamside vegetation and accelerated surface erosion or stream sedimenta- channel stability whenever a management activity tion and cummulative effects are not of is proposed along a stream or lake. significance2 Problems do occur under severe conditions such as rain on frozen ground or rapid 'Larsen, Daniel M Soil Resource Inventory, Deschutes National Forest, Pacific Northwest Region, 1976 snowmelt. The Forest is actively treating road network drainage problems which cause the =Hughes, Dallas Letter (2500) documentingsewice trip October greatest amount of erosion and sedimentation? 9, 1984 Regional Oftice. Pacific Northwest Region These problems occur on a small percentage of the Forest and are not common on a Forest-wide "McCammon, Bruce. Hydrologic investigation of the Effects of basis. Best management practices, which include Timber Harvesting and Road Construction within Watersheds Tributary to the Metolius River Deschutes National Forest, proper road location and design and streamside Pacific Norfhwest Region. 1984 management prescriptions, are utilized to protect against accelerated erosion or sediment problems. 'McCammon, Bruce Prediction of Flood Magnitude and Frequency on the Deschutes National Forest (a) and Streamflow Streamflow on the Forest generally originates Summary of the Deschutes National Forest (b) Deschutes from deep-seated springs. As such, streamflow is National Forest, Pacific Northwest Region, 1979 very stable and is not subject to frequent flooding? USatterfhwaite, Thomas Unpublished Field Evaluations of Other than under severe conditions, such as Channel Stabiilty Deschutes National Forest, Pacific Northwest rain-on-snow, streams on this Forest are rarely Region, 1979 high enough to overtop their banks. Channel stability, evaluated in terms of bank slope, vegeta- 'Hughes, Dallas Letter (2540)dated September IO, 1982 tive cover, cutting, deposition, and debris, is 'good' Regional Office, Pacific Northwest Region or ?ai? with some zones of 'excellent'5. Streams 'McCammon, Bruce Numerous Technical Reports and Sum- flowing through permanent range, which has maries on Water Quality Monitoring, Deschutes National Forest, been grazed over the last several decades, are in Paclfic Northwest Region, 19781985 EIS 3 - 8 A good example of this is the Metolius River, which Class 4 streams are intermittent or empheremal. rises from a series of spring vents near Black The miles of stream by class are. Butte. The Metolius is one of the largest spring- driven streams in the United States. Such streams Class Mlles are not subject to the wide fluctuation of flow commonly found in the western US. Flooding 1 161 occurs only under extreme circumstances, such 2 181 as rapid snow melt on frozen ground. 3 1 64 4 226 Another consequence of the very stable flows are generally well armored banks which are in good The surface water yield on the Forest during a condition. Riparian vegetation is also in good normal water year is approximately 2.26 million condtion throughout most of the Forest and serves acre feet (based on water year 1978). Much of to protect the streambanks from occasional this water is immediately used as it leaves the over-bank flow Forest boundary for irrigation. domestic domestic water supply, and to generate hydropower. Nearly There is one exception to the very stable flows, all the water leaving the Forest receives some well armored streambanks and excellent riparian beneficial use by humans prior to reaching the zone conditions. Approximately 35 percent of the Columbia River. streambank along the Upper Deschutes from Wickiup Reservoir to Benham Falls in an unstable, highly eroding condition Lakes This condition is caused by the release schedule The Forest has some of the most strikingly scenic of local irrigation districts. The normal historical water bodies on the West Coast Lakes are glacial, flow for the Upper Deschutes near Wickiup volcanic, and man-made in origin Some have Reservoir was almost 1,500 cubic feet per second surface inflow but no surface outflow (Davis, (cfs). Currently irrigation districts hold all but 20 Sparks) Others have no inflow but considerable cfs in Crane Prairie and Wickiup Reservoirs during surface outflow (Little Lava, the source of the the winter and early spring (November through Deschutes River). April) and then release over 2,000 cfs during the There are a total of 304 lakes on the Forest, many irrigation season. of which are small glacially formed lakes in Wildernesses near the Cascade crest. There are Frost action on the high pumice streambanks three major irrigation reservoirs on the Forest: during the winter, when flow is very low, causes Wickiup, Crane Prairie, and Crescent Lake. They piping and disintegration Past efforts to mitigate provide a total storage of about 341,000 acre feet this degradation have met with little success used to irrigate lands north and east of Bend and as far north as Madras. Short of very expensrve mechanical measures, specialists who have studied the stuation believe Two lakes (Paulina and East) lie within the caldera the only remedy is to return the stream to a more of Newberry volcano. While there is no suiface even year-around flow. inflow into these lakes, one stream does flow out of Paulina Lake. This is a unique hydrologic regime, There are more than 732 miles of stream on the isolated and tied to an area of significant geother- Forest. There are four stream classifications based mal energy potential. on the beneficial uses and the potentialfor affecting downstream watercourses.