horizons (less than 4 cm) in these forests, particularly low- 

 productivity, harsh, or disturbed sites (table 5). The same 

 trend was shown for percentage of the core (table 4) and 

 total volume of sample (table 2) represented by organic 

 horizons. 



DISCUSSION 



The tendency to accumulate soil organic matter in the 

 mature, productive stands studied is probably a simple 

 reflection of biomass production (table 2). However, the 

 significantly greater accumulation on the western hemlock 

 and subalpine fir sites in western Montana (sites 1 and 2) 

 as compared to the western hemlock, white pine, and 

 grand fir sites in northern Idaho that have higher produc- 

 tivity (sites 4, 5, 6— Pfister and others 1977) may indicate 

 that the cool Montana climate slows decay of organic resi- 

 dues enough to offset higher biomass production in Idaho. 

 The thin organic horizons on low to moderate productivity 

 habitat series are commensurate with their production. 

 The low to extremely low organic reserves (organic com- 

 ponent volume by depth) on the variously disturbed sites 

 likely reflect mixing, transport, and loss of the forest floor 

 due to harvesting and site preparation (tables 2 and 5). 



The distribution of soil organic components was highly 

 variable in both combined total and individual quantity 

 (table 2). However, substantial reserves of decayed wood 

 were present in most of the old-growth stands, except 

 those likely to have a frequent fire history (sites 6, 7, 8). 

 Similarly, substantial reserves of decayed wood were pres- 

 ent in most second-growth sites except where site prepara- 

 tion had been extensive (sites 13, 14). The relatively good 

 balance between the long-lived organic components (wood 

 and humus) on most of these sites may result from a 

 usually infrequent or low-temperature fire history that 

 allows production of the large woody residues required to 

 produce soil-wood deposits. 



Numbers of ectomycorrhizal short root tips also gen- 

 erally reflected site productivity, particularly of the undis- 

 turbed stands. On the second-growth sites, short root tip 

 numbers were moderate in intermediate-aged stands and 

 low in young stands (table 3). These numbers likely reflect 

 the root density of host trees. However, reduced organic 

 horizons may also be a contributing factor. Organic 

 materials contain most of the soil nutrients (Harvey and 

 others in press) and moisture (Barr 1930; Harvey and 

 others 1978; Place 1950) and are a highly favorable 

 substrate for ectomycorrhizal activities (Fogel and Hunt 

 1979; Harvey and others 1976, 1979, in press; Maser and 

 Trappe 1984; Mikola and others 1966; Vogt and others 

 1981). ♦ 



The highly significant distribution patterns of active ec- 

 tomycorrhizal short root tips among the various soil com- 

 ponents, both within and between sites (table 3), are likely 

 brought about by the individual nature of these compo- 

 nents as conditioned by the climate and fertility of the site 

 (Harvey and others in press). For example, humus is an 

 attractive substrate for feeder roots because of its high 

 nutrient content, but its shallow depth limits moisture 

 retention. On the other hand, soil wood is moderately 

 supplied with nutrients but usually occurs in large enough 

 volumes to be a significant source for moisture. 



CONCLUSION AND APPLICATIONS 



Perhaps the most striking effect (or lack thereof) of site 

 or disturbance on numbers of ectomycorrhizal root tips, in- 

 cluding differences in host species and time (age), was the 

 generally similar distribution of ectomycorrhizal roots 

 among organic versus mineral soil horizons. In most cases 

 short root tips were concentrated in organic horizons. On 

 the two sites where this did not occur, the forest floor was 

 thin and root tips were most numerous in the surface 

 mineral layer. Thus, the surface soils, particularly the 

 organic horizons, were universally important for support- 

 ing this important feeder root activity on all 14 sites. This 

 is a clear indication that management methods likely to 

 impact soil surfaces, particularly mechanical site prepara- 

 tion and broadcast burning, should be applied with caution 

 to minimize loss or disruption of surface soil horizons, 

 organic and mineral. The extremely shallow distribution of 

 most ectomycorrhizal activity (4 cm or less) emphasizes a 

 critical need to protect this valuable resource. 



REFERENCES 



Barr, P. M. The effect of soil moisture of the establish- 

 ment spruce reproduction in British Columbia. Bulletin 

 26. New Haven, CT: Yale University, School of 

 Forestry; 1930. 57 p. 



Bjorkman, E. Forest tree mycorrhizae— the conditions for 

 its formation and the significance for the growth and af- 

 forestation. Plant and Soil. 32: 589-610; 1970. 



Berntsen, C. M. Seedling distribution on a spruce-hemlock 

 clearcut. Research Note PNW-119. Portland, OR: U.S. 

 Department of Agriculture, Forest Service, Pacific 

 Northwest Forest and Range Experiment Station; 1955. 

 7 p. 



Christy, J. E.; Sollins, P.; Trappe, J. M. First year sur- 

 vival of Tsuga heterophylla without mycorrhizae and 

 subsequent ectomycorrhizal development on decaying 

 logs and mineral soil. Canadian Journal of Botany. 60: 

 1601-1605; 1982. 



Danielson, R. M. Ectomycorrhizal association in jack pine 

 stands in northeastern Alberta. Canadian Journal of 

 Botany. 62: 932-939; 1984. 



Fogel, R.; Hunt, G. Fungal and arboreal biomass in a 

 western Oregon Douglas-fir ecosystem: distribution pat- 

 terns and turnover. Canadian Journal of Forest 

 Research. 9: 245-256; 1979. 



Hacskaylo, E. Dependence of mycorrhizal fungi on hosts. 

 Bulletin of the Torrey Botanical Club. 100: 217-223; 

 1973. 



Harvey, A. E.; Jurgensen, M. F.; Larsen, M. J. Seasonal 

 distribution of ectomycorrhizae in a mature Douglas- 

 fir/larch forest soil in western Montana. Forest Science. 

 24: 203-208; 1978. 



Harvey, A. E.; Jurgensen, M. F.; Larsen, M. J. Organic 

 reserves: importance to ectomycorrhizae in forest soils 

 of western Montana. Forest Science. 27: 442-445; 1981. 



Harvey, A. E.; Jurgensen, M. F.; Larsen, M. J.; 

 Graham, R. T. Decaying organic materials and soil qual- 

 ity in the Inland Northwest: a management opportunity. 

 General Technical Report. Ogden, UT: U.S. Department 

 of Agriculture, Forest Service, Intermountain Research 

 Station; [in press]. 



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