averaging 20 percent, and an elevation of approximately 

 2,800 m. The primary ectomycorrhizal host is 165-year-old 

 lodgepole pine. Subalpine fir and Engelmann spruce occur 

 occasionally. 



Site 8 (PP-W) is a ponderosa pine climax located in 

 northeastern Washington near Spokane. It has a west 

 aspect, a slope averaging 25 percent, and an elevation of 

 approximately 700 m. The only ectomycorrhizal host is 

 200-year-old ponderosa pine (Pinus ponderosa Laws.). 



Sample Sites, Second-Growth 



Three of the six disturbed sites were chosen to provide a 

 uniform habitat series (subalpine fir climax type) from a 

 localized geographic area representative of a common com- 

 mercial forest in the Inland Northwest. The other three 

 were chosen to provide a comparison with drier conditions 

 (Douglas-fir climax type) from the same geographic area 

 (western Montana). To represent a variety of harvesting 

 and natural stand situations frequently found in the Inland 

 Northwest, treatments (disturbance type) were chosen to 

 provide a variation in time since disturbance and in 

 species dominance. 



Site 9 (MIX-i) (i = intermediate-aged) is a subalpine fir 

 climax type in western Montana adjacent to the Hungry 

 Horse Reservoir. It has an east aspect, a slope averaging 

 40 percent, and an elevation of approximately 1,500 m. 

 This is an old wildfire-impacted site that now supports a 

 mixed-species, pole-sized, 80-year-old stand of primarily 

 Douglas-fir. Subalpine fir is also abundant. Western white 

 pine, grand fir, and birch {Betula papyrifera Marsh) occur 

 occasionally. 



Site 10 (LPP-i) is a Douglas-fir climax type in western 

 Montana near Martin City. It has a west aspect, a slope 

 averaging 5 percent, and an elevation of approximately 

 1,200 m. This is an unharvested site with the previous 

 stand terminated by wildfire. The present stand is 

 50 years old. The primary ectomycorrhizal host is lodge- 

 pole pine. Douglas-fir occurs occasionally. 



Site 11 (WL-y) (y = young-aged) is a subalpine fir climax 

 type in western Montana adjacent to the Coram Experi- 

 mental Forest. It has a north aspect, a slope averaging 

 15 percent, and an elevation of approximately 1,300 m. 

 This is a harvested site (clearcut and broadcast burned) 

 with a planted, 15-year-old stand of western larch. The 

 primary ectomycorrhizal species is western larch. No other 

 hosts occurred within the plot. 



Site 12 (DF-i) is a Douglas-fir climax type in western 

 Montana on the University of Montana's Lubrecht Ex- 

 perimental Forest. It has a west aspect, a slope averaging 

 10 percent, and an elevation of approximately 1,200 m. 

 The site has an extensive harvesting history (intermittent 

 selective cutting) and now has a mixed-size, intermediate- 

 aged stand (60 to 120 years old) of nearly pure Douglas- 

 fir. The primary ectomycorrhizal species is Douglas-fir. No 

 other host occurred within the sampled area. 



Site 13 (PP-i) is a Douglas-fir climax type in western 

 Montana adjacent to the Hungry Horse Reservoir. It has a 

 southwest aspect, a slope averaging 50 percent, and an 

 elevation of approximately 1,300 m. This harvested site 



(partial cut with an underburn) now has a residual stand 

 of ponderosa pine, 80 to 100 years old. The primary ec- 

 tomycorrhizal host is ponderosa pine. An occasional, small 

 Douglas-fir occurred within the sampled area. 



Site 14 (LPP-y) is a subalpine fir climax type in western 

 Montana near the town of Hungry Horse. It has a west 

 aspect, a slope averaging 5 percent, and an elevation of 

 approximately 1,200 m. The previous stand originated as a 

 result of wildfire in 1929. The stand was harvested by 

 clearcut (with an occasional seed tree). At the time of sam- 

 pling there was a 15-year-old regenerating stand of lodge- 

 pole pine. Lodgepole pine was the only ectomycorrhizal 

 host, with no other hosts in the sampled area. 



Climate 



Thirteen of these sites are representative of the typical 

 Inland Northwestern climate characterized by cold wet 

 winters and warm dry summers. The weather on these 

 sites is generated primarily by Pacific frontal systems. 

 Site 7 is located on the east side of the Continental Divide 

 so is more often impacted by continental weather, in- 

 cluding frequent summer rainfall generated by thunder- 

 storm activity. 



STUDY METHODS 



Individual soil samples consisted of 10- by 38-cm soil 

 cores (Jurgensen and others 1977) taken randomly, five 

 from around each plot center, 10 plot centers scattered 

 evenly (approximately 30-m spacing) over 1 ha of uniform 

 conditions on each of the 14 study sites. Conditions evalu- 

 ated for uniformity included slope, aspect, soils, distur- 

 bance, stocking, and understory vegetation. Samples were 

 taken during late spring and early summer over several 

 years (1978 to 1982) to obtain maximum ectomycorrhizal 

 activity for each site (Harvey and others 1978). Each soil 

 core was subdivided in the field into the following com- 

 ponents or horizons: Htter (Oj horizon); humus (O2 hori- 

 zon); brown cubicle decayed soil wood, also referred to as 

 the O3 horizon (Harvey and others 1979); surface mineral 

 soil (the first 5 cm); and the remaining mineral soil to a 

 depth of 30 cm. Each fraction was hand-separated and 

 placed in a plastic bag immediately after collection. Vol- 

 ume and depth occupied by each fraction was determined 

 by measuring its depth in the undisturbed core. 



In the laboratory, each soil fraction was shaken for ap- 

 proximately 5 minutes in a standard 2-mm soil sieve. 

 Decayed wood, humus, or mineral aggregates were gently 

 crumbed before sieving. Soil and root material greater 

 than 2 mm were thoroughly washed in running water and 

 examined microscopically for ectomycorrhizal short roots. 



Active ectomycorrhizal root tips were counted with the 

 aid of a dissecting microscope (10-50 x). Each active tip 

 was counted, even though in many cases it was part of a 

 complex structure. No attempt was made to count or dif- 

 ferentiate between root tips that were inactive and those 

 that were dead. The criteria used for identifying "active" 

 ectomycorrhizal root tips have been described (Harvey and 

 others 1976). 



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