From FEIS for Silver Fire Recovery Project -- July, 1988

Key Indicator - Total Organic Matter Retained On Site

Total organic matter (TOM) has been selected as the key indicator for the issue of site productivity. Categories of TOM for any site include 'above ground' trees, shrubs, and herbs; "on ground" duff, litter, and dead wood; and "below ground" soil organic matter and roots. The above ground organic matter is the single most indicative factor that is affected by timber harvest, fuels treatment, and reforestation, and is also the component that can be most easily managed and monitored. Fuels treatment and reforestation along with timber harvest offer methods to manage large and small woody materials on

site and the means to monitor the decomposition and value of this material over time.

Background

Sustainable productivity of forests in the northwestern United States is an emerging issue and concern. Processes by which organic and mineral components and their associated nutrients are stored, cycled, and lost from forest ecosystems have been documented by Harvey and others (1980; 1987). Zinke and others (1982) have documented the close association between organic matter and nutrients and the losses of nitrogen, phosphorus, magnesium, and potassium from the forest ecosystem by intensive management. Work in both the United States and Australia (McColl and Powers, 1984; Squires and others, 1985) documents that productivitv may be reduced for one or more rotations when significant losses of soil organic matter, nitrogen, and sulfur accompany mechanical site preparation and fuels treatment. Experimental work in Australia suggests that litter and logging residues maintain forest productivity in the second rotation at the first rotation level. This work by Squires and others (7985) shows that residues serve as a mulch to enhance water storage, keep weeds down, and retain nutrients. For whole tree harvest of western hemlock, Sachs and Sollens (1986) found a linear decline of soil organic matter accompanying successive rotations. In another study of whole tree harvest, Kimmins (1977) found that losses of nutrients and organic matter are significant, and that the value of organic matter as a sink for nutrient capital becomes more important as the rates of removal approach the rates of replacement.

Losses of nutrients that accompany timber harvest followed by prescribed fire is a concern and is being monitored in the Pacific Northwest Region (Little and Klock, 1985). Their study shows that care must be used in yarding unmerchantable material (YUM) and in prescribed burning if we are to save nitrogen, sulfur, duff, litter, and woody residues for the next rotations. Boyer and Dell (1980), in a research summary of the effects of fire on soils following timber harvest in the northwestern U.S., show the strong relationship between residual organic matter and the availability of nutrients and moisture. Other research by Amaranthus and Perry (1987; In Press) in southwestern Oregon shows a decline in mycorrhizal activity and seedling survival associated with high losses of organic matter following timber harvest and slash burning. Freedman (1981) has

shown that site quality decreases with the combined and interactive effects of fire and harvest.

Organic matter, including large and small woody material, soil organic matter, and forest floor litter has been shown to be the most important factor in maintenance of site quality of western coniferous forest ecosystems (Harvey and others, 1987; Kimmins, 1977). Methods by which it may be measured and managed in forest ecosystems have been identified by Maser and Trappe (1984) and Brown (1985).

Organic Matter Categories

Total organic matter (TOM) for a typical site before the fire, averaged 367 tons per acre, with a range of 220 to 515 tons per acre. For clarification, TOM was arbitrarily divided into three categories: "Above ground" herbs, shrubs, and trees; "on ground" duff, litter, and dead wood; and "below ground" roots and soil organic matter.

Above ground components - 57 percent of total organic matter (210 tons)

Pre-fire weight of above ground organic matter was estimated to be 210 tons per acre based on average tree, shrub, and herb stocking on the burned area. For the tree weight, tops and branches were estimated at 20%, boles at 60%, and roots at 20% of the total (Wenger, 1984; Maxwell and Ward, 1980). Using standard weights for Douglas-fir wood, it was determined that average pre-fire tree weight was 200 tons per acre with a range of 125 to 375 tons. The weight of shrubs and herbs was estimated at 10 tons per acre with a range of 5 to 15 tons using methods of Gholz and others (1979) and with help of fuels specialists. Fire reduced the above ground material by 10 (5%), 20 (10%), and 40 (20%) tons per acre for low, moderate, and high intensity burned areas.

On ground components - 6 percent of total organic matter (22 tons)

Pre-fire duff, litter, and dead woody materials were estimated at 22 tons per acre, with a range of 1 1 to 33 tons from the Regional Photo Series (Maxwell and Ward, 1980) with verification by fuels specialists. 11 (50%), 20 (90%), and 21 (95%) tons per acre for low, moderate, and high intensity burned areas.

Below ground components - 37 percent of total organic matter (135 tons)

Pre-fire soil organic matter averaged 85 tons per acre with a range of 80 to 90 tons, based on soil test data. On average, there is 5 percent organic matter in the top 12 inches of soil, with most in the top 4 inches, and a sharp reduction in organic matter from 5 to 12 inches below the ground surface. Fire reduced soil organic matter by 2 (2%), 4 (5%), and 8 (10%) tons per acre for low, moderate, and high intensity burned areas.

Pre-fire root weight was estimated to be 50 tons per acre with a range of 25 to 75 tons. We assumed that roots comprise 20 percent of the 210 tons of tree, shrub, and herb mass per acre (Wenger, 1984). Fire reduced the root mass by 3 (5%), 6 (12%), and 12 (25%) tons per acre for low, moderate, and high intensity burned areas.

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Reductions of TOM by wild fire, log removal, and YUM/slash treatment

Figures I through 4 display distribution of total organic matter for 8 scenarios that depict pre-fire, post-fire, and post-fire/harvest conditions. These data present the user an opportunity to visualize amounts of organic matter remaining after harvest and YUM/slash treatments.

Figure 5 shows reductions of total organic matter for incremental increases in bole removal and YUM/slash treatments. Columns 1 and 2 display increasing bole removal and reduction of TOM starting at 22, 14, and 7 percent post-fire reduction levels for high, moderate, and low intensity burns. Columns 3 and 4 show YUM/slash losses and the cumulative reduction of TOM for bole removal and YUM/slash treatments.

Reduction of TOM Reduction of TOM Cumulative

Bole with Bole from YUM/Slash Reduction

Removal* Removal Treatment of TOM

HIGH 0%(post-fire) 22%

20% 30% 2% 32%

Fire 40% 39% 4% 43%

Loss 60% 47% 6% 53%

22% 80% 55% 9% 64%

100% 63% 11% 74%

MOD 0%(post-fire) 14%

20% 22% 2% 24%

Fire 40% 31% 4% 35%

Loss 60% 39% 6% 45%

14% 80% 47% 9% 56%

100% 55% 11% 66%

LOW 0%(post-fire) 7%

20% 15% 2% 17%

Fire 40% 24% 4% 28%

Loss 60% 32% 6% 38%

7% 80% 40% 9% 49%

100% 48% 11% 59%

Range of 0 to 1 00 percent bole removal corresponds to 0 to 60 thousand board feet per acre.

Implications

Organic matter losses would directly effect soil chemical and physical properties. Losses of organic materials would expose mineral soil to erosion. Runoff would increase where puddled and crusted, bare mineral soil occurs. Available soil water would be reduced as large and small organics are lost by decay and erosion. Soil microflora and microfauna types and species would shift along with changes in soil temperature and in soil chemistry. Nutrient storage and release would decrease as organics are reduced or removed. Similarly, on-site nutrients including, nitrogen, phosphorus, magnesium and potassium would be reduced with loss of organics. Indirectly and in combination these properties would affect productivity of all forest resources. Certainly, the effects would vary with soil types, plant associations and ecosystem processes, but change would occur. Whether the changes would measureably affect productivity in the near-term or long-term depends on inherent site quality. On low site land that has low organic and

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nutrient reserves, the effect may be observable and measureable within a rotation or less. For high site land that has large organic and nutrient reserves, the effects may be less easily detected or perhaps immeasureable in the near-term. (It is important to point out here the two "functional" pools of organic matter. The soil pool is the critical short-term concern following fire because it stabilizes nutrients and microbes and thereby provides the focus for stand regrowth. The above ground pool represents a longer-term supply of large and small woody material, which has a quite different function in the soil, supplying water storage, sites for nitrogen fixation, and an array of biological functions, most of which are active for many years.)

Uncertainties

It is for the uncertain relationships between organic matter and productivity, that we are reluctant to assign precise amounts of organic matter for retention during timber harvest. Uncertainty, however lies not with absence of a relationship, but with the strength of the relationship and the quality and quantity of organic residues to be saved on site. By reserving organic matter supplies today we would preserve options until research solidifies the ties between organics retained now and productivity in the future.

Opportunlties

Retention of woody residues provides an opportunity to mitigate organic losses and to maintain potential productivity. In that biologic activity centers on the organic residues, we should strive to retain materials that would supply decomposition products for 5 to 250 years. Further, there is a need to strike a balance between retention which would maintain the site and that which would create unacceptable fire risk and planting conditions (Dell and Ward, 1971; Harvey and others, 1987). The Siskiyou National Forest Position Statement (1987) gives guidance for retention of standing and down large woody material following harvest. The guide indicates types and amounts of large and small woody materials and methods to retain them on site including:

Leave 5 to 20+ pieces of large woody material (logs) per acre, each greater than 40 cubic feet.

Retain one cluster of 5 to 10 standing dead or live trees per 5 to 20 acres of harvest unit.

Retain 4 to 14 standing dead or live wildlife trees per acre.

Retain occasional uncut areas of 1 to 5 acres with dead or live trees, as centers for biological activity.

Reduce or omit YUM.

Reduce or omit fuels treatment.

Benefits

Preservation of future options by saving organic residues on site.

Maintenance of productivity of all resources in the next 100 to 300 years.

Maintenance of nutrients from large and small woody materials retained on site.

Maintenance of hiding cover, nesting habitat, and food sources for wildlife.

Maintenance of soil moisture retention by large and small organic residues. Reduced soil erosion with more woody material for cover and check dams. Maintenance of soil microfloral and microfaunal activity.

Lower logging costs for limited or no YUM. Lower immediate fuels treatment costs.

Risks

Increased fire hazard for several decades.

Increased potential wildfire suppression costs.

Loss of merchantable wood products.

Literature Cited

Amaranthus, M. P., and D. A. Perry. In Press. Mycorrhizal formation and growth of Douglas-fir seedlings in three southern Oregon vegetation types. In: Maintaining long-term productivity of Pacific Northwest forests. Proceedings of a symposium; 1987 Mar. 31-Apr. 2; Corvallis, Oregon. Timber Press, Portland, Oregon.

Amaranthus, M. P., and D. A. Perry. 1987. Effect of soil transfer on ectomycorrhiza formation and the survival and growth of conifer seedlings on old, nonreforsted clearcuts. Can. Jour. For. Res. 17: 944-950.

Boyer, D. E. and J. D. Dell. 1980. Fire effects on Pacific Northwest forest soils. USDA Forest Service Pacific Northwest Region, Portland, Oregon.

Brown, E. R., Tech. Editor. 1985. Management of wildlife and fish habitats in western Oregon and Washington. Part 1 - Chapter 8, Dead and down woody material. USDA Forest Service Pacific Northwest Region, Portland, Oregon.

Dell, J. D. and F. R. Ward. 1971. Logging residues on Douglas-fir region clearcuts: Weights and volumes. USDA Forest Service Research Paper PNW-1 15. Pacific Northwest Forest and Range Experiment Station, Portland, Oregon.

Freedman, B. 1981. Intensive forest harvest: A review of nutrient budget considerations. Information Report M-X-121. Maritimes Forest Research Centre, Canadian Forestry Service, Dept of the Environment. Fredericton, New Brunswick, Canada.

Gholz, H. L., C. C. Grier, A. G. Campbell, and A. T. Brown. 1979. Equations for estimating biomass and leaf area of plants in the Pacific Northwest. Research Paper 41. School of Forestry, Oregon State Univ., Corvallis, Oregon.

Harmon, M. E., J. F. Franklin, F. J. Swanson, P. Sollins, S. V. Gregory, J. D. Lattin, N. H. Anderson, S. P. Cline, N. G. Aumen, J. R. Sedell, G. W. Lienkaemper, K. Cromack, Jr., and K. W. Cummins. 1986. Ecology of coarse woody debris in temperate ecosystems. Adv. in Ecol. Res. 15:133-302.

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Harvey, A. E., M. F. Jurgensen, and M. J. Larsen. 1979. Role of Forest fuels in the biology and management of soil. USDA Forest Service General Technical Report INT-65. Intermountain Forest and Range Experiment Station, Ogden, Utah.

Harvey, A. E., M. F. Jurgensen, and M. J. Larson. 1980. Biological implications of increasing harvest intensity on the maintenance and productivity of forest soils. In: USDA Forest Service General Technical Report INT-90. Environmental consequences of timber harvesting in Rocky Mountain coniferous forests. pp. 211-220. Intermountain Forest and Range Experiment Station, Ogden, Utah.

Harvey, A. E., M. F. Jurgensen, M. J. Larsen, and R. T. Graham. 1987. Decaying organic materials and soil quality in the Inland Northwest: A management opportunity. USDA Forest Service General Technical Report INT-2-25. Intermountain Forest and Range Experiment Station, Ogden, Utah.

Kimmins, J. P. 1977. Evaluation of the consequences for future tree productivity of the loss of nutrients in whole tree harvesting. Forest Ecol. and Mgt. 1: 1 69-1 83.

Little, S. N., and G. 0. Klock. 1985. The influence of residue removal and prescribed fire on distributions of forest nutrients. USDA Forest Service Research Paper PNW-338. Pacific Northwest Forest and Range Experiment Station, Portland, Oregon.

Maser, C., and J. M. Trappe, Tech. Editors. 1984. The seen and unseen world of the fallen tree. USDA Forest Service General Technical Report PNW-164. Pacific Northwest Forest and Range Experiment Station, Portland, Oregon.

McColl, J. G., and R. F. Powers. 1984. Consequences of forest management on soil-tree relationships. In: Nutrition of Plantation Forests, pp. 379-412. Academic Press, London.

Sachs, D., and P. Sollens. 1986. Potential effects of management practices on nitrogen nutrition and long-term productivity of western hemlock stands. Forest Ecol. and Mgt. 17

(1): 25-36.

Siskiyou National Forest Position Statement. 1987. Unpublished Report. Forest Management Team notes of May 27, 1987 on file at Forest Supervisors Office, Grants Pass, Oregon.

Squire, R., P. W. Farrell, D. W. Flinn, and B. C. Acberli. 1985. Productivity of first and second rotation stands of radiata pine on sandy soils. II. Height and volume growth at five years. Australian Forestry. 48 (2): 127-137.

Wenger, K. F. 198-4. Forestry Handbook, 2nd Edition. John Wiley and Sons. New York, New York.

Zinke, P. W., A. G. Stagenberger, M. J. Font, B. W. Parker, and R. G. Stine. 1982. Elemental drain of fertility from a Sierra mixed conifer forest site due to intensive harvest of fuels. California Forestry Note, No. 82. California Department of Forestry, Sacramento.

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