1. Amaranthus, M.P., C.Y. Li and D.A. Perry. 1990. Influence of vegetation type and madrone soil inoculum on associative nitrogen fixation in Douglas-fir rhizospheres. Canadian-Journal-of-Forest-Research 20(3): 368-371.

Keywords:      planting operations

                        soil properties

Abstract: In studies in SW Oregon in 1985, Douglas fir (Pseudotsuga menziesii) seedlings grown at a site cleared of whiteleaf manzanita (Arctostaphylos viscida) and an adjacent, cleared, annual grass meadow were either inoculated with 100-120 ml per seedling of pasteurized or unpasteurized soil from a nearby Pacific madrone (Arbutus menziesii) stand, or left uninoculated. After one growing season, Douglas fir seedling whole-plant soil systems were assayed for nitrogenase activity by the acetylene reduction method. The rate of acetylene reduction in rhizospheres of uninoculated seedlings from the manzanita site (1.40 +or- 0.44 nmol/h) was significantly greater than that of uninoculated seedlings from the meadow site (0.67 +or- 0.15 nmol/h). Unpasteurized madrone soil increased the rate of acetylene reduction by >500% for inoculated seedlings grown on the manzanita site, but decreased it by 80% for those grown on the meadow site. The influence of madrone soil was apparently biotic: pasteurized madrone soil did not have a significant effect. No acetylene was reduced in soil without seedlings. Azospirillum sp., a microaerophilic nitrogen (N2) fixing bacterium, was isolated from within the mycorrhizas of inoculated seedlings harvested from the manzanita site. These results suggest that early successional ectomycorrhizal shrubs and broadleaved trees may be important in maintaining mycorrhizal fungi and associated N2 fixers after severe disturbance.

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2.
Bailey, V.L., J.L. Smith and H. Bolton, Jr. 2002. Fungal-to-bacterial ratios in soils investigated for enhanced C sequestration. Soil-Biology-and-Biochemistry 34(7): 997-1007.

Keywords:      fertilization

                        soil properties

Abstract: Fungi and bacteria govern most of the transformations and ensuing long-term storage of organic C in soils. We assessed the relative contributions of these two groups of organisms to the microbial biomass and activity of soils from five different ecosystems with treatments hypothesized to enhance soil C sequestration: (1) desert (an elevation gradient allowed comparison of soil developed in a cooler, wetter climate with soil developed in a warmer, drier climate), (2) restored tallgrass prairie (land reverted to native prairie in 1979 and neighbouring land farmed to row crops for ~100 year), (3,4) two forest types (Douglas fir [Pseudotsuga menziesii] and loblolly pine [Pinus taeda], unfertilized control and N-fertilized plots), and (5) agricultural land (conventional- and no-till management systems). The selective inhibition technique, using captan (fungicide) and oxytetracycline hydrochloride (bactericide), was used to determine the activities (respiration) of fungi and bacteria in each of these soils and substrate-induced respiration was used to measure total active soil microbial biomass C. Phospholipid fatty acid analysis was used to determine the composition of the soil microbial biomass and determine if the activities and structure of the microbial communities were related. Differences in fungal-to-bacterial (F:B) activities between treatments at a site were greatest at the prairie sites. The restored prairie had the highest F:B (13.5) and high total C (49.9 g C kg-1 soil); neighbouring soil farmed to maize had an F:B of 0.85 and total C of 36.0 g C kg-1 soil. Within the pairs of study soils, those that were tilled had lower fungal activities and stored C than those that were managed to native or no-till systems. In all pairs of soils, soils that had higher absolute fungal activities also had more total soil C and when two extreme cases were removed fungal activity was correlated with total soil C (R2=0.85). Thus, in this small set of diverse soils, increased fungal activities, more than F:B ratios, were associated with increased soil C. Practices that involved invasive land management decreased fungal activity and stored soil C compared to similar soils that were less intrusively managed.

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3.
Binkley, D. and P. Reid. 1985. Long-term increase of nitrogen availability from fertilization of Douglas-fir. Canadian-Journal-of-Forest-Research 15(4): 723-724.

Keywords:      fertilization

                        growth

                        tree physiology

                        soil properties

Abstract: [See FA 44, 4708; 46, 1837] Most Douglas-fir stands respond to nitrogen fertilizing by increasing stem growth for less than 8 yr, but one plantation at the United States Forest Service Wind River Experimental Forest in Washington State has responded for over 15 yr. In this study nitrogen concn. of foliage and fresh litter were shown to be higher in the fertilized plots (470 kg/ha N) 18 yr after fertilizing. Retranslocation of N from senescent needles was not affected and stem growth per unit N in the canopy was similar between unfertilized and fertilized plots. An index of soil N availability in the fertilized plots was twice that of unfertilized plots. The higher stem growth, leaf area, and stem growth per unit leaf area demonstrated in an earlier study appeared to be related to a sustained increase in soil N availability rather than increased N-use efficiency. An examination of soil N transformation processes is needed to complete the explanation of the unusually prolonged fertilizer response in these plots.

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4.
Blake, J., S.R. Webster and S.P. Gessel. 1988a. Soil sulfate-sulfur and growth responses of nitrogen-fertilized Douglas-fir to sulfur. Soil-Science-Society-of-America-Journal 52(4): 1141-1147.

Keywords:      fertilization

                        soil properties

                        growth

Abstract: Two studies were conducted to determine the growth response of N-fertilized Douglas fir [Pseudotsuga menziesii (Mirb.) Franco] to S supplements. The relationship between response and soil SO4-S extracted with Morgan's solution, 1.22 M NaOAc + 0.53 M HOAc (pH 4.8), was used to establish critical levels for S. Douglas fir seedlings were grown in the greenhouse in the surface mineral layer (0 to 0.15 m) of 20 forest soils from western Washington and Oregon. On the average, significant increases in total dry weight (17.5%), stem diameter (10.1%), and height (6.9%) occurred when soils were fertilized with N and S in comparison to N alone. Using the Cate-Nelson procedure, growth responses to N and S were most likely to occur when soil SO4-S was below 14 mg S kg-1. Twenty eight installations were established in the field containing five treatments, three rates of N as urea, and one plot of 336 kg N ha-1 with P, K, Ca, and S. Differences in percent basal area growth between N alone and N with P, K, Ca, and S were significantly related to soil SO4-S. Over the initial 5-yr period, response over N alone was improved by 74% when soil SO4-S was <20 mg S kg-1. When the N with P, K, Ca, and S plots were retreated with only N and S, response over the next 3 yr was more than doubled compared with N alone. Identification of S responsive stands was improved by the inclusion of stand age weighted subsoil SO4-S concentrations.

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5.
Brix, H. and A.K. Mitchell. 1986. Thinning and nitrogen fertilization effects on soil and tree water stress in a Douglas-fir stand. Canadian-Journal-of-Forest-Research 16(6): 1334-1338.

Keywords:      thinning

                        fertilization

                        soil properties

                        tree physiology

Abstract: Soil and tree water potentials were studied for 10 yr in a Douglas fir stand near Shawnigan Lake, British Columbia that was treated when 24 yr old with heavy thinning (removing superscript 2/3 of b.a.) and/or fertilization with 448 kg N/ha as urea. Control plots were not thinned or fertilized. Throughout the 10 yr, thinning increased soil water potential during the dry summer periods (July-early Oct.) by as much as 1 MPa. The effect of fertilization on soil water potential was slight and nonsignificant, and only apparent towards the end of the study in spite of large increases in leaf area (50% after 7 yr). Fertilization increased water use efficiency. The favourable soil water conditions produced by thinning led to improved shoot water potential only during predawn and early morning. Removal of understorey in a thinned and fertilized plot did not affect soil or shoot water potential.

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6.
Busse, M.D., G.O. Fiddler and A.W. Ratcliff. 2004. Ectomycorrhizal formation in herbicide-treated soils of differing clay and organic matter content. Water, Air, and Soil Pollution 152:23-34.

Keywords:      release treatments

                        chemical release

                        growth

                        tree morphology

                        tree/stand health

                        soil properties

                        mycorrhizal response

Abstract: Herbicides are commonly used on private timberlands in the western United States for site preparation and control of competing vegetation. How non-target soil biota respond to herbicide applications, however, is not thoroughly understood. We tested the effects of triclorpyr, imazapyr, and sulfometuron methyl on ectomycorrhizal formation in a greenhouse study. Ponderosa pine, Douglas-fir, and white fir seedlings were grown in four forest soils ranging in clay content from 9 to 33% and organic matter content from 3 to 17%, and treated with commercial formulations of each herbicide at 0, 1.0, and 2.0 times the recommended field rate. Many of the possible herbicide-soil combinations resulted in reduced seedling growth. Root development was particularly sensitive to the three herbicides, with an average of 51% fewer root tips compared to the control treatment. The ability of mycorrhizal fungi to infect the remaining root tips, however, was uninhibited. Mycorrhizal formation was high, averaging 91% of all root tips, regardless of herbicide, application rate, soil type, or conifer species. In agreement, soil microbial biomass and respiratory activity were unaffected by the herbicide treatments. The results show that these herbicides do not alter the capability of mycorrhizal fungi to infect roots, even at concentrations detrimental to seedling growth.

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7.
Carr, W.W. 1987. Restoring productivity on degraded forest soils: two case studies. B.C. Ministry of Forests FRDA-Report 002. vi + 21 p.

Keywords:      site preparation

                        fertilization

                        tree physiology

                        growth

                        soil properties

Abstract: The use of green fallowing was studied at 2 sites, viz. (a) a coastal site at Koksilah, 15 km NW of Shawnigan Lake, British Columbia, where extensive subsoil exposure had resulted from roading operations in a highly productive Douglas fir (Pseudotsuga menziesii) and western hemlock (Tsuga heterophylla) stand, and (b) an inland site 30 km S. of Vanderhook including several landings and skid roads which had been deep-ripped to a depth of 50 cm, reducing soil density to 1350 kg/msuperscript 3. Plots at (a) were seeded in 1976 at 100 kg/ha with a grass/legume mixture including 3 spp. of Trifolium and Lotus corniculatus, and received NPK (10:30:10) at 450 kg/ha. Site nutrient levels improved substantially over 5 yr with N showing the greatest gains, and Douglas fir seedlings (1+2) planted in 1977 responded with increased foliar N and K contents and 300% greater ht. growth. Plots at (b) were seeded in 1981 at 40 kg/ha with a legume mixture of 3 spp. of Trifolium, Medicago sativa and L. corniculatus, and received NPK (19:19:19) at 300 kg/ha. Nutrient gains were found after 2 yr for P, K and especially N, and although foliar nutrient contents and growth of lodgepole pine (Pinus contorta) seedlings showed no increase, the enhancement of site nutrient capital is considered to be a gain likely to benefit commercial forestry production.

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8.
Carter, R. and K. Klinka. 1992. Use of ecological site classification in the prediction of forest productivity and response to fertilisation. South-African-Forestry-Journal (160): 19-23.

Keywords:      fertilization

growth
soil properties

Abstract: The results are presented of two related studies in southern coastal British Columbia. A total of 149 study plots in even-aged immature Douglas fir (Pseudotsuga menziesii) stands were categorized into 6 ecologically similar site associations (indicated best by climax plant communities) and into 15 soil moisture and soil nutrient combinations, for the prediction of site index. Fifty-one of these plots were used to predict basal area growth response to nitrogen fertilizer (225 kg N/ha as urea). Regression models indicated strong correlations between Douglas fir site index (m (height)/50 yr) and both indirect and direct measures of soil moisture and nutrient regimes (Rsuperscript 2 >0.72; p <0.01). Third-year basal area response to N fertilizer varied significantly among site associations (Rsuperscript 2 = 0.60; p <0.01). Site index also showed a significant relation with third-year basal area response (Rsuperscript 2 = 0.52; p <0.01), while the best predictive model included site associations and pretreatment foliar N and sulfate-S (Rsuperscript 2 = 0.64; p <0.01). It is suggested that the approach and methods of the study are applicable to predicting site-specific growth performance and response to fertilization of other tree species, including eucalypts.

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9.
Carter, R.E., E.R.G. McWilliams and K. Klinka. 1998. Predicting response of coastal Douglas-fir to fertilizer treatments. Forest-Ecology-and-Management 107(1/3): 275-289.

Keywords:      fertilization

growth
soil properties

Abstract: A broadly-based, intensive Douglas-fir (Pseudotsuga menziesii) fertilizer experiment throughout southern coastal British Columbia (48 sites) was used to examine 3- and 6-yr crop tree growth responses to prescribed fertilizer applications (N alone, and N + additional nutrients identified as potentially deficient by foliar analysis). Absolute and relative basal area responses were evaluated in relation to site associations of the provincial ecosystem classification system, site index (SI), and a large number of site and stand chemical and physical properties. Few of the site and stand variables examined as possible response prediction criteria appeared to have any real utility. The strongest relationships found were between relative basal area response and (1) site index (Rsuperscript 2 0.46 for both 3- and 6-yr responses), (2) mineral soil mineralizable-N (Rsuperscript 2 0.50 and 0.46 for yr 3 and 6 responses, respectively), and (3) total mineralizable-N (Rsuperscript 2 0.47 and 0.50 for yr 3 and 6 responses, respectively). In all cases average relative response declined with increasing site quality. However, there were highly productive sites (SI50 <more or =>35 m) characterized by an absence of growing-season water deficits and relatively low foliar N concentrations (12-13 g/kg) which showed significant fertilizer responses. These sites are where the greatest financial returns from fertilizing may be realized. Relationships identified between site and stand variables and basal area responses were, in many cases, different from those found by other researchers for coastal Douglas fir. This brings the portability of identified relationships into question.

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10.
Chappell, H.N., D.W. Cole, S.P. Gessel and R.B. Walker. 1991. Forest fertilization research and practice in the Pacific Northwest. Fertilizer-Research 27(1): 129-140.

Keywords:      fertilization

                        soil properties

Abstract: A review showed that most Pacific Northwest USA Douglas-fir (Pseudotsuga menziesii) forest sites are nitrogen deficient. Mineral cycling research has shown high C:N ratios and low nitrification rates for soils in the region. Research and development projects in the Pacific Northwest have produced an information base that is used to select sites and stands for fertilization and to forecast growth after treatment. Much of the basis for operational fertilization programmes in western Oregon and Washington comes from cooperative research; current activities for these programmes are directed toward improving site-specific response information. Forest fertilization in the Pacific Northwest has become a major silvicultural practice over the past two decades. Forest industry and government organizations managing forest lands in western Oregon and Washington apply nitrogen fertilizer to Douglas-fir stands over a range of soil and stand types. About 50 000 to 55 000 ha are fertilized each year, and future programmes will probably be of similar magnitude. Most current plans for management regimes including fertilization require multiple applications.

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11.
Chappell, H.N., C.E. Prescott and L. Vesterdal. 1999. Long-term effects of nitrogen fertilization on nitrogen availability in coastal Douglas-fir forest floors. Soil-Science-Society-of-America-Journal 63(5): 1448-1454.

Keywords:      fertilization

                        soil properties

Abstract: The aim of this study was to determine if N availability was elevated 8 to 12 years after repeated N fertilization, and if the effects of N fertilization were related to the soil N capital. Rates of N cycling in control and fertilized plots of Douglas-fir (Pseudotsuga menziesii) in Oregon, USA, were compared by measuring net N mineralization rates in forest floors and by estimating rates of N turnover from the litterfall/forest floor ratio. Litterfall N contents, litter N concentrations, and rates of N turnover increased along the gradient in soil N capital in both control and fertilized stands. Fertilization did not affect litterfall N content, but C:N ratios of litter and forest floors were significantly lower in fertilized stands along the gradient. Turnover rates of N in the forest floors were not higher in fertilized plots than in control plots, nor were rates of net N mineralization affected by fertilization. Net nitrification rates were higher in some of the plots that received 1120 kg N ha-1 than in control plots. Nitrogen fertilization did not result in a sustained increase in N cycling and N availability analogous to a higher site N capital, and the effect of N fertilization was not related to the initial soil N capital of these sites.

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12.
Childs, S.W. and L.E. Flint. 1987. Effect of shadecards, shelterwoods, and clearcuts on temperature and moisture environments. Forest-Ecology-and-Management 18(3): 205-217.

Keywords:      planting operations

                        tree/stand health

                        soil properties

                        tree physiology

                        tree phenology

Abstract: A comparison was made of two common techniques used to improve seedling survival on hot, dry reforestation sites. Adjacent shelterwood and clearcut sites in SW Oregon, USA, planted with 2+0 Douglas fir, were located and instrumented to compare temp. and moisture. In addition, cardboard shadecards were placed beside half of the seedlings studied. Seasonal measurements or observations of soil moisture, soil temp., solar radiation, air temp., stomatal diffusion resistance, seedling phenology and survival provided the basis for comparisons. Shelterwoods and shadecards improved seedling survival in relation to the clearcut. Both treatments affected soil temp. but the nature of the effects was different. The shelterwood canopy reduced solar radiation incident at the soil surface and caused cooler soil temp. throughout the soil profile. Shadecards reduced soil temp. only to a depth of 20 mm. Both treatments reduced the duration of periods of high soil temp. Shelterwood treatment delayed seasonal water loss and reduced seedling water stress as measured by stomatal resistance. Shadecards did not significantly affect seedling stomatal resistance. Differences in seedling survival caused by shadecards and shelterwoods are apparently due to different influences on the seedling microclimate. Shelterwood causes a large reduction in soil temp. as well as decreased seedling water stress. Shadecards modify the soil temp. less extensively and so have less effect on seedling survival.

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13.
Childs, S.W., H.R. Holbo and E.L. Miller. 1985. Shadecard and shelterwood modification of the soil temperature environment. Soil-Science-Society-of-America-Journal 49(4): 1018-1023.

Keywords:      planting operations

                        soil properties

Abstract: A study was conducted on steep, south-facing slopes in southwest Oregon to assess the effect of two common reforestation practices on the soil thermal environment. Three clearcut sites and three shelterwood sites were instrumented to measure soil temperature at five depths in the vicinity of shaded and unshaded Douglas-fir seedlings. Since the soils studied were skeletal, heat capacities of both fine and coarse soil fractions were determined for each site. These data were used to estimate soil heat fluxes. Shelterwoods decrease soil temperatures approximately 6 K when compared with clearcuts. This result holds at both 20- and 320-mm depths. Shelterwoods also decrease the depth of diurnal heating and decrease maximum hourly heat loss and gain values by 73 and 80 W/msuperscript 2, respectively. Shadecards, cardboard rectangles placed to the southwest of seedlings, generally have little effect on the soil temperature regime of skeletal soils but are effective in reducing daily heat flux. The dominant shadecard effect is a decrease in average daytime heat flux by 22 W/msuperscript 2, but shadecards also decrease average nighttime fluxes. Shelterwoods ameliorate seasonal soil temperature conditions significantly and may be an appropriate technique in situations where cumulative soil heating limits reforestation success. Shadecards should be useful in situations where heat stress events of only a few days are a problem. Over a season, shadecards exert little control, and their influence on stress is limited. Since all soils studied had high heat capacities due to large rock fragment content the conclusions of this study may be limited to soils with large soil heat capacity.

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14.
Colinas, C., R. Molina, J. Trappe and D. Perry. 1994a. Ectomycorrhizas and rhizosphere microorganisms of seedlings of Pseudotsuga menziesii (Mirb.) Franco planted on a degraded site and inoculated with forest soils pretreated with selective biocides. New-Phytologist 127(3): 529-537.

Keywords:      planting operations

                        fertilization

                        soil properties

                        mycorrhizal response

Abstract: Inoculation of planting holes with small amounts of soil from a mature forest or a plantation can improve formation of ectomycorrhizas on Pseudotsuga menziesii seedlings in degraded clearcuts in southwestern Oregon. To determine the component(s) of transferred soil responsible for increased ectomycorrhiza formation, soil from a clearcut, a mature forest and a plantation was treated with one of the following: (1) fertilizer to test for the effect of nutrients, (2) dimethoate and carbofuran to test for the effect on microarthropods or nematodes, (3) fumagillin to test for the effect on protozoa, (4) captan to test for the effect on fungi, (5) penicillin and oxytetracycline to test for the effect on bacteria, (6) pasteurization to test for the effect of active forms of organisms, (7) Tyndallization to test for the effect of resting forms of organisms, or (8) water as a control. The effect was studied of inoculation with soil subjected to these treatments on number and types of ectomycorrhizas, on length of active mycelium, and on number of active bacteria in the rhizosphere. Inoculation with untreated forest or plantation soils increased the number of ectomycorrhizas but did not change the mycorrhizal types present. Most agents had different effects in different soils. Inoculation with pasteurized and Tyndallized clearcut and plantation soils increased the number of Rhizopogon- and Thelephora-type ectomycorrhizas and decreased the number of active bacteria, as did untreated forest soil. It is hypothesized that the role of the soil transfer is to provide a rhizosphere environment free from a deleterious organism present in the clearcut. In this environment, beneficial organisms present in the clearcut or brought in with the seedling from the nursery can proliferate.

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15.
Curtis, R.O., D.D. Marshall and D.S. DeBell. 2004. Silvicultural options for young-growth Douglas-fir forests: the Capitol Forest study - establishment and first results. Pacific Northwest-Research-Station,-USDA-Forest-Service General-Technical-Report PNW-GTR-598. xi + 110 p.

Keywords:      thinning

                        commercial thinning

                        economics

                        soil properties

Abstract: This report describes the origin, design, establishment and measurement procedures and first results of a large long term cooperative study comparing a number of widely different silvicultural regimes applied to young-growth Douglas-fir (Pseudotsuga menziesii) stands managed for multiple objectives. Regimes consist of (1) conventional clear felling followed by intermediate thinning; (2) retention of reserve trees to create a two-aged stand; (3) small patch cuts dispersed within a thinned matrix, repeated at approximately 15-year intervals to create a mosaic of age classes; (4) group selection within a thinned matrix on an approximate 15-year cycle; (5) continued thinning on an extended rotation; and (6) an untreated control. Each of these regimes is on operation-size units (approximately 30 to 70 acres each). A LIDAR system was used to scan the surface of the 2 miles2 that encompass the Blue Ridge study site on the Capitol State Forest, near Olympia, Washington, USA. This measurement technology emits laser pulses that are reflected by vegetation, buildings, or the ground surface. Output variables from the study to be evaluated include conventional timber growth and yield statistics, harvest costs, sale layout and administration costs, aesthetic effects and public acceptance, soil disturbance, bird populations, and economic aspects. Descriptive statistics and some initial results are presented for the first replicate, established in 1997-98.

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16.
Donegan, K.K., L.S. Watrud, R.J. Seidler, S.P. Maggard, T. Shiroyama, L.A. Porteous and G. DiGiovanni. 2001. Soil and litter organisms in Pacific Northwest forests under different management practices. Applied Soil Ecology 18:159-175.

Keywords:      planting operations

                        site preparation

                        prescribed fire

                        soil properties

Abstract: Soil and litter organisms were monitored for their response to different forest management practices. Litter and soil cores (0-10, 10-20 cm) were collected at approximately 8-week intervals over a 19-month period from a low elevation 110-140-year-old Douglas fir (Pseudotsuga menziesii) forest and adjacent 8-year-old clearcut in the Oregon Cascades, and from a high elevation 200-250-year-old Douglas fir forest and adjacent 5-year-old clearcut in the McKenzie River drainage. The low elevation clearcut had been broadcast burned and replanted with Douglas fir trees and a grass (Dactylis and Lolium)-legume (Trifolium and Lotus) mixture whereas the high elevation clearcut was not burned, large woody debris was left, and it was replanted with Douglas fir, Noble fir [Abies procera], Grand fir [Abies grandis], and western white pine [Pinus monticola]. The litter and soil cores were analysed for types of microarthropods and numbers of nematodes, fungi, culturable, aerobic bacteria, spore-forming bacteria, and chitin-degrading bacteria. Microbial community metabolic profiles, using the Biolog method, were also generated for the 0-10 cm soil samples. Populations of Pseudomonas spp. were analysed in the litter and soil samples using 16S rDNA fingerprints. Plant surveys were conducted to identify potential relationships of soil organisms to plant community composition. At both elevational field sites, there were significantly (P < 0.05) higher levels of nematodes and microarthropods in litter and soil in forest plots than in clear felled plots. Bacterial and fungal populations were also significantly higher in litter in forest plots than in clear felled plots at the high elevation site. In the litter and soil at the low elevation site and the soil at the high elevation site, however, microbial levels were higher in clear felled plots than in forest plots. The Pseudomonas spp. populations and the microbial community metabolic profiles in the 0-10 cm soil differed significantly between the forest and clear felled plots at the low elevation site but not at the high elevation site. At both elevational field sites, the plant cover (%) and plant density were significantly higher in clear felled plots than in forest plots. These observed differences in the population size and composition of organisms between mature forests and both low management and high management clearcuts demonstrated the impacts forest management practices may have on the soil ecosystem.

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17.
Edmonds, R.L. and T. Hsiang. 1987. Forest floor and soil influence on response of Douglas-fir to urea. Soil-Science-Society-of-America-Journal 51(5): 1332-1337.

Keywords:      fertilization

                        thinning

                        growth

                        soil properties

Abstract: Data from the Regional Forest Nutrition Research Project (RFNRP) in Washington and Oregon were analyzed to improve stand-specific prediction of Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] response to urea fertilization. The response variable (relative difference in volume growth between fertilized and control plots 4 yr after fertilization with 448 kg N/ha) was regressed against 28 stand and site variables (e.g., age, elevation, forest floor C/N ratio, soil cation exchange capacity, etc.) using stepwise multiple regression analysis. Data from 120 installations were stratified by thinning level (thinned or unthinned), geographic location (provinces), and site quality (site index and class). Forest floor C/N ratio was the dominant variable related to response. In thinned installations of high site quality (site classes 1 and 2), 60% of variation in response was explained by the forest floor C/N, and 75% of the variation in response was explained with inclusion of surface soil exchangeable K. In thinned, low site quality stands, response was not as well related to forest floor C/N. Analysis of the data by province indicated that S may be limiting in southwest Oregon and P in coastal Washington.

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18.
Feller, M.C. 1988. Relationships between fuel properties and slashburning-induced nutrient losses. Forest-Science 34(4): 998-1015.

Keywords:      site preparation

                        prescribed fire

                        soil properties

Abstract: The relations between slash load, slash and forest floor consumption variables, and species origin of slash (slash type) on one hand and nutrient (N, P, S, K, Na, Mg and Ca) losses to the atmosphere during slashburning on the other were studied by burning 50 plots, each 2.25 msuperscript 2 in area. The plots contained known amounts of slash materials derived from four major southwestern British Columbia tree species (Tsuga heterophylla, Thuja plicata, Chamaecyparis nootkatensis and Pseudotsuga menziesii) and were burned under different weather conditions. Nutrient losses (g/msuperscript 2) decreased in the order N > Ca > S > K > Mg > P > Na and were generally within the range of such losses recorded for operational prescribed burns in western North America. Losses of all nutrients except Na were positively correlated with fuel consumption. Nitrogen and S exhibited the best correlations, whereas no correlations were found for Na. Of the fuel consumption variables considered, depth of forest floor consumed, then total slash consumption, were best correlated with nutrient loss. Losses of most nutrients generally increased with slash load and as slash type changed from Tsuga to Pseudotsuga to Thuja/Chamaecyparis. This was partly due to the effects of slash load and slash type on fuel consumption, and partly due to their effects on burning-caused changes in nutrient concn. in slash materials. The study suggests that nutrient losses to the atmosphere during operational slashburns can be minimized by minimizing forest floor and large diameter slash consumption during burning.

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19.
Feller, M.C. 1990. Herbicide application followed by prescribed fire to convert a brushfield into a conifer plantation in south coastal B.C.: a combination of the initial effects of two treatments. B.C. Ministry of Forests FRDA Report 146. 40 p.

Keywords:      site preparation

                        chemical preparation

                        prescribed fire

                        growth

                        tree/stand health

                        soil properties

                        stand conditions

Abstract: A field study was carried out in Pseudotsuga menziesii stands in British Columbia, Canada, to investigate the effects on vegetation of glyphosate applications in September 1987 or July 1988, followed by burning in October 1988. Results did only show slight differences between treatments.

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20.
Feller, M.C., J.P. Kimmins and K.A. Scoullar. 1983. FORCYTE-10: calibration data and simulation of potential long-term effects of intensive forest management on site productivity, economic performance, and energy benefit/cost ratio. In I.U.F.R.B. Symposium on. Forest Site and Continuous Productivity; Seattle, Washington; August 22-28, 1982. Eds. R. Ballard and S.P. Gessel. Pacific-Northwest-Forest-and-Range-Experiment-Station, USDA-Forest-Service General-Technical-Report PNW-GTR-163 Part B. 179-200 pp.

Keywords:      thinning

                        fertilization

                        soil properties

                        economics

                        computer modeling

Abstract: FORCYTE (FORest nutrient Cycling and Yield Trend Evaluator) is a computer simulation model of forest plant biomass production, litterfall, and decomposition, complete with nutrient cycling, nutrient limitation on growth, and a variety of management interventions. The model is a computerized approach to the estimation of the effects of varying thinning and fertilizer regimes, utilization level, and rotation length on site nutrient budgets, stand productivity, and the economic performance and energy efficiency of management. The model has evolved over 5 years to its present version FORCYTE-10, which is briefly described. Accompanying the development of FORCYTE, there has been a series of field research projects. Detailed biomass and biogeochemical descriptions of age sequences of Douglas-fir stands on both good and poor sites have been prepared for purposes of model calibration and testing. The present report summarizes some of the results of the FORCYTE-10 field studies on Vancouver Island, British Columbia, and presents some examples of the use of the model when calibrated with these data.

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21.
Flint, L.E. and S.W. Childs. 1987. Effect of shading, mulching, and vegetation control on Douglas-fir seedling growth and soil water supply. Forest-Ecology-and-Management 18(3): 189-203.

Keywords:      release treatments

                        chemical release

                        manual release

                        growth

                        soil properties

Abstract: Harsh environments on many harvested sites in SW Oregon necessitate site modifications for successful regeneration of Douglas fir. A 2-yr study was made with 350 seedlings to assess the effects of 12 soil-surface shading, mulching, and vegetation control techniques on seedling growth and soil temp. and moisture environments. Major effects of treatments were to lower soil surface temp., reduce soil surface evaporation, and reduce vegetative competition for soil water. These affected seedlings by adjusting the timing of seedling growth and reducing soil water loss to increase available water for seedling use. Final seedling shoot vol. and stem diam. both differed among treatments. Seedlings in treatments where competing vegetation was controlled showed significantly greater growth than seedlings in other treatments. Soil water loss in treatments where either soil surface evaporation was controlled by mulching, or where competing vegetation was controlled, was significantly less than water loss from the shaded and control treatments. Soil water loss in treatments with vegetation controlled by herbicide was significantly less than in treatments with vegetation controlled by scalping. Seedlings showed greatest growth with treatments that elicited the most efficient use of available microsite water either by reducing soil surface evaporation or vegetation competition.

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22.
Fox, T.R. 2004. Nitrogen mineralization following fertilization of Douglas-fir forests with urea in Western Washington. Soil-Science-Society-of-America-Journal 68(5): 1720-1728.

Keywords:      fertilization

                        soil properties

Abstract: Nitrogen mineralization following repeated applications of urea fertilizer was determined in the A horizon soil from two stands of Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] in the Cascade Mountains of Washington. Repeated applications of urea at rates ranging from 0 to 600 kg N ha-1 were made at annual and 5-yr intervals over a 6-yr period. Nitrogen fertilization increased N mineralization potential in these soils. However, soil N mineralization followed a quadratic relationship with the total amount of N applied in fertilizer over the 6-yr treatment period, increasing up to total application rates of 450 kg N ha-1 and then declining at higher rates. The decrease in N mineralization rates at the high N fertilization rates may be due to changes in the quality of soil organic matter, which reduced the effectiveness of extracellular enzymes and decreases the rate of decomposition and mineralization. Soil pH dropped following urea fertilization, with greater declines observed in the highest rates of urea fertilizer. Decreases in extractable Ca and Mg levels in the soil accompanied the decline in soil pH. These results suggest that high rates of nitrification occurred and that nitrate leaching was stripping Ca and Mg from the cation-exchange complex in these soils. It appears that repeated applications of urea fertilizer at low to intermediate rates may increase long-term N availability and thus improve soil quality. However, annual applications of high rates of urea may decrease soil quality because under these circumstances N mineralization did not increase and there was a loss of cations from the soil.

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23. Frey Klett, P., J.L. Churin, J.C. Pierrat and J. Garbaye.
1999. Dose effect in the dual inoculation of an ectomycorrhizal fungus and a mycorrhiza helper bacterium in two forest nurseries. Soil Biology and Biochemistry 31:1555-1562.

Keywords:      nursery operations

                        growth

                        carbon allocation

                        mycorrhizal response

                        soil properties

Abstract: Disinfected soil at two Douglas-fir (Pseudotsuga menziesii) bare-root forest nurseries was inoculated with three doses (8 X105, 8 X107 and 8 X109 cfu [colony forming units]/m2) of the rifampicin-resistant mycorrhiza helper bacterium Pseudomonas fluorescens strain BBc6R8 and the ectomycorrhizal fungus Laccaria bicolor strain S238N. In one of the two nurseries, two doses of fungal inoculum (50 and 100 mg/m2 dry weight (DW) mycelium entrapped in alginate beads at the constant dose of 1 litre/m2) were tested. For all bacterial treatments the density of P. fluorescens BBc6R8 in the soil, determined by dilution plating, dropped below the detection limit (10-2 cfu/g DW soil) 2 weeks after inoculation. Fifteen weeks after inoculation, the introduced bacterium was detected by enrichment only in the treatments inoculated with the highest bacterial dose. Two years after inoculation, P. fluorescens BBc6R8 was not detected in the soil of any of the bacterial treatments. Five months after inoculation and sowing, bacterial inoculation significantly increased the percentage of mycorrhizal short roots on plants inoculated with either low or high amounts of L. bicolor, in one of the nurseries. The lowest bacterial dose increased mycorrhizal colonization from 45 to 70% in plants inoculated with the low amount of fungal inoculum, and from 64 to 77% in plants inoculated with the high amount of fungal inoculum. The lowest bacterial dose increased mycorrhizal colonization more than the highest bacterial dose. The same L. bicolor mycorrhizal index (70%) was obtained with 50 mg/m2 DW mycelium plus the bacterium than with twice this fungal dose and no bacterium (64%). Two years after inoculation, the height of the mycorrhizal Douglas-firs in the other nursery was significantly increased by the lowest bacterial dose (from 40.7 to 42.6 cm). It was indicated that co-inoculating a helper bacterium together with an ectomycorrhizal fungus is an efficient way to optimize controlled mycorrhization techniques for the production of high-quality Douglas-fir planting stocks. It was confirmed that BBc6R8 acts at a low population density (less than 10-2 cfu/g soil), this contrasts with most PGPR [plant growth promoting rhizobacteria?] effects where the minimal inoculation dose of 105 cfu/g soil is required to obtain the beneficial effect.

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24.
Gagnon, J., C.G. Langlois, D. Bouchard, F.l. Tacon and F. Le Tacon. 1995. Growth and ectomycorrhizal formation of container-grown Douglas-fir seedlings inoculated with Laccaria bicolor under four levels of nitrogen fertilization. Canadian Journal of Forest Research 25:1953-1961.

Keywords:      nursery operations

                        nursery fertilization

                        growth

                        carbon allocation

                        tree physiology

                        tree morphology

                        mycorrhizal response

                        soil properties

Abstract: Container-grown Douglas fir (Pseudotsuga menziesii) seedlings were inoculated at the time of sowing with a Laccaria bicolor mycelial suspension produced in a fermentor. They were grown in a peat moss-vermiculite substrate under four levels of N fertilization (7.2, 14.4, 21.6 and 28.7 mg/seedling per season (N1, N2, N3 and N4, respectively)) to determine the N level suitable for both ectomycorrhizal development and seedling growth. After 18 weeks in the greenhouse, seedlings inoculated with L. bicolor had 44%, 32%, 44% and 5% of their short roots mycorrhizal when fertilized with N1, N2, N3 and N4, respectively. Only when they were fertilized with N4 did the L. bicolor seedlings have significantly greater shoot height than the controls. For the other growth parameters, they were not significantly different from control seedlings for any of the N levels. After 18 weeks, regardless of the level of N, seedlings inoculated with L. bicolor had significantly lower N concentrations (%) and contents (mg/seedling) than the uninoculated ones. Consequently, for the same production of biomass, the mycorrhizal seedlings had taken up less N than the nonmycorrhizal ones. The efficiency of applied N, expressed in terms of produced biomass, decreased when the N fertilization increased; mycorrhizal and nonmycorrhizal seedlings did not tend to be different. The efficiency of the absorbed N also decrease with the level of applied N, but less rapidly, and tended to be greater for the mycorrhizal seedlings than for the nonmycorrhizal ones. Therefore, the mycorrhizal infection improved the utilization of the absorbed N. N3 was the best of the four N levels used, since it was the only one that maximized both the ectomycorrhizal formation and the growth of the seedlings. In other words, a total seedling N concentration of 1.6% and a substrate fertility of 52 p.p.m. N are appropriate to optimize both the ectomycorrhizal development and the growth of Douglas fir seedlings.

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25.
Gessel, S.P., R.E. Miller and D.W. Cole. 1990. Relative importance of water and nutrients on the growth of coast Douglas fir in the Pacific Northwest. Forest-Ecology-and-Management 30(1-4): 327-340.

Keywords:      fertilization

                        growth

                        soil properties

Abstract: The Douglas-fir region in northwestern North America is characterized by abundant moisture supply during winter, extended dry periods during the growing season and significant differences in water availability. Many soils have low fertility and indigenous tree species respond to nitrogen fertilization, especially Douglas fir (Pseudotsuga menziesii). Although irrigation of commercial forests in this region is currently impractical, questions arising about the relative importance of water and nutrients were examined using long-term growth data from three studies. At Pack Forest (Washington), fertilization without irrigation doubled growth rates, and no positive growth responses were measured from irrigation. Short-term (5 yr) irrigation with sewage effluent containing many nutrients resulted in a six-fold increase in biomass production for poplar and three-fold for Douglas fir as compared to irrigation with equal volumes of river water. Volume growth in 12- to 65-yr-old stands in southwestern Oregon was increased by fertilization at about 70% of the locations; annual gain averaged 2.73 msuperscript 3/ha for 5-12 yr. Response was not related to annual precipitation, which ranged from 81 to 279 cm, nor other moisture-related variables. Absolute and relative volume response showed highest correlation with soil carbon : nitrogen ratio. Compared with nutrition, moisture does not seem to be a major limiting factor for growth in the Douglas fir region of the Pacific Northwest.

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26.
Harrison, R., D.S. Xue, C. Henry and D.W. Cole. 1994a. Long-term effects of heavy applications of biosolids on organic matter and nutrient content of a coarse-textured forest soil. Forest-Ecology-and-Management 66(1/3): 165-177.

Keywords:      fertilization

                        soil properties

Abstract: Long-term changes in soil properties due to a single heavy application of municipal biosolids (municipal sewage sludge) on a coarse-textured glacial outwash soil were evaluated. Study sites, located at the Pack Experimental Forest, 100 km S. of Seattle, Washington, were clearcut, cleared, fertilized with 500 t/ha of municipal biosolids and planted with either Lombardy poplar (Populus nigra var. italica), Douglas fir (Pseudotsuga menziesii) or ponderosa pine (Pinus ponderosa) in 1975. Soil samples were taken in 1990 from treated stands and from adjacent (unamended) control sites by horizon to a depth of 185 cm. Biosolids-amended samples had greater amounts (mg/g) of C (139 vs. 67), N (12 vs 3.4), P (14 vs. 2.2) and S (2.5 vs. 0.4) contents in 0-7 cm mineral soil and other surface soil horizons, compared with control soil horizons, but showed no significant differences below 25 cm. Soil pH ranged from 0.4 to 1.0 units lower in biosolids-amended vs. unamended soil throughout the sampled soil horizon. Soil cation exchange capacity was higher in the surface soil horizons of treated plots (30 vs. 18 mmolc kg-1 in 0-7 cm soil), but there were no significant differences below 50 cm. Biosolids-amended samples had greater amounts (mg/g) of total Ca (13 vs. 6.1 in 0-7 cm soil) and K (1.9 vs. 1.5 in 0-7 cm soil) throughout the sampled soil profile. Total Mg was relatively constant (2.0-3.0) throughout the sampled soil profile. Study results indicate that one of the primary objectives of the original biosolids application (increasing total nutrients in the rooting zone of the forest soil) extended at least 15 years from the application date.

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27.
Harrison, R.B., S.P. Gessel, D. Zabowski, C.L. Henry, D.S. Xue, D.W. Cole and J.E. Compton. 1996. Mechanisms of negative impacts of three forest treatments on nutrient availability. Soil-Science-Society-of-America-Journal 60(6): 1622-1628.

Keywords:      fertilization

                        growth

                        soil properties

                        tree/stand health

Abstract: Many forest management treatments are directly aimed at maintaining or enhancing forest productivity. There may also be secondary effects that detract from this goal. Three case studies in Washington state, USA, are discussed in which several mechanisms may have led to adverse secondary impacts. In the first study, pulp and paper (PIT) sludges were mixed into soil and growth of Douglas-fir (Pseudotsuga menziesii), noble fir (Abies procera) and western white pine (Pinus monticola) was monitored. There was a significant negative correlation of height and diameter growth and C:N ratio for Douglas-fir and western white pine. In a second study, effects of 50 years of red alder (Alnus rubra) and Douglas-fir growth on soil chemistry and stand productivity were compared. When the 50-year-old stands were cut and red alder was established by planting into the soil of the former Douglas-fir and red alder forests, a reduction in available P in the soil of the previous red alder stand was observed. In a third study, high rates of low C:N ratio organic matter (300 t/ha) were added in municipal biosolids (~8000 kg N/ha) to Douglas-fir and grand fir (Abies grandis) plantations. Excess organic N in the biosolids apparently mineralized, nitrified, and contributed to soil acidification and accelerated cation leaching. Severe Mg deficiency (0.25 g/kg in biosolids-treated vs. 0.93 g/kg in untreated areas) might be the cause of observed foliar chlorosis and poor growth rates.

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28.
Harrison, R.B., C.L. Henry, D.W. Cole and D. Xue. 1995. Long-term changes in organic matter in soils receiving applications of municipal biosolids. In Carbon forms and functions in forest soils. Eds. W.W. McFee and J.M. Kelly. Soil Science Society of America Inc., Madison WI. pp. 139-153.

Keywords:      fertilization

                        soil properties

Abstract: Soil concn of C, N, P, Ca, Mg, K, pH, and CEC were compared at two forest sites of contrasting mineralogy and management in Washington, U.S.A., after the application of municipal biosolids. The soil on the Pack forest site was an extremely coarse-textured outwash soil whilst that of the Mt. Pilchuck Tree Farm was a sandy outwash soil. The Pack forest was characterized by 80-yr-old second growth Douglas fir (Pseudotsuga menziesii) with an understory of salal (Gaultheria shallon). The Mt. Pilchuck Tree Farm site was characterized by 60-yr-old second growth Douglas fir with an understory of salal. Both sites were harvested and cleared prior to the initiation of the studies. The forest floors were different in the biosolids-amended soils compared with the unamended soils, with more highly humified material and fewer fine roots. Large increases in C, N, and P concn in the amended plots were restricted to the top 27 cm of soil. Ca and Mg increases were observed at the Pack Forest amended site but not at the Mt. Pilchuck Tree Farm site. At both sites the pH was lower in the amended plots. The differences between the sites are discussed with reference to soil type and management practices. Implications for long-term nutrient retention are considered.

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29.
Harrison, R.B., C.L. Henry and D.S. Xue. 1994b. Magnesium deficiency in Douglas-fir and grand fir growing on a sandy outwash soil amended with sewage sludge. Water, Air, and Soil Pollution 75(1/2): 37-50.

Keywords:      fertilization

                        tree/stand health

                        tree physiology

                        soil properties

Abstract: Soil and plant samples were collected from chlorotic plantations of grand fir (Abies grandis) and Douglas fir (Pseudotsuga menziesii) near Seattle, Washington state, USA, in winter 1989. The soils had been amended in 1981 with an average of 300 dry t/ha of municipal sewage sludge. The sludge amendment resulted in an N application rate of approximately 8000 kg/ha. Foliage analysis indicated that a severe Mg deficiency (0.25 g/kg in sludge-treated vs. 0.93 g/kg in untreated areas) might be the cause of chlorosis. No other nutrient showed concentrations in the deficient or toxic ranges. Trace metal levels in foliage were increased significantly for Ni, Cd and Cr at sludge-treated sites, but were not at toxic levels. Soil samples taken to a depth of 1.4 m indicated the potential for soil acidification (up to 0.9 pH unit) in soil surface horizons. In addition, exchangeable Ca, Mg and K may have been depleted in surface horizons. Exchangeable Al and Fe were greater in the surface of sludge-treated sites. These observations, and the loss of much of the nitrogen added during the sludge amendment, indicated that nitrification and cation leaching were the most likely mechanism for acidification and depletion of exchangeable cations. Fertilizing the plantation with MgSO4 or dolomitic limestone was carried out in spring 1990. New foliage collected in June 1990 was non-chlorotic and significantly higher in Mg concentration than unfertilized foliage (1.1. vs. 0.7 g/kg, respectively). The results of this study indicate that it is important to assess the potential for initiating a nutrient deficiency due to secondary effects of sludge application in forest systems.

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30.
Heilman, P. 1983. Effects of surface treatment and interplanting of shrub alder on rowth of Douglas-fir on coal spoils. Journal-of-Environmental-Quality 12(1): 109-113.

Keywords:      planting operations

                        site preparation