Table 1 — Incidence of Armillaria spp. signs and/or symptoms on 

 randomly selected 0.04-ha plots classified by climax 

 vegetation series on 15 Northern Rocky Mountain 

 National Forests 





Average 



Number 



Number 



Proportion 





site 



of 



with 



with 



Climax indicator 



index^ 



plots 



Armillaria 



Armillaria 



Subalpine fir 



16.15 



235 



15 



0.42 



Douglas-fir 



16.46 



^18 



6 



.33 



Grand fir 



19.81 



42 



33 



.79 



Western redcedar 



21.95 



10 



10 



1.00 



Western hemlock 



22.56 



15 



14 



.93 



x2 = 29.38, d.f. = 4, prob. of larger = 0.0005. 



'Average height at 50 years (meters) of all conifer species in the series 

 obtained from Cooper and others (in press); Pfister and others (1977); 

 Steele and others (1981). 



^Includes the single mountain hemlock series plot. 



^Includes the single ponderosa pine series plot. 



Armillaria. The distribution on the more productive series 

 seems essentially continuous (table 2). Within the grand fir 

 series, two habitat types characterized as hot-dry (CARU 

 and SPBE) failed to yield Armillaria. Of the 60 remaining 

 plots, only two (one ABGR/CLUN and one TSHE/CLUN) 

 failed to yield Armillaria. 



There was good continuity between habitat types where 

 Armillaria was and was not found, regardless of geo- 

 graphic location. For example, Armillaria was absent 

 from cold-dry habitat types (ABLA/VASC and ABLA/ 

 XETE) on both northern (Flathead, Kootenai, Lolo, and 

 St. Joe) and southern (Payette, Boise, and Wallowa- 

 Whitman) National Forests. On the other hand, if one of 

 the habitat types that supported Armillaria elsewhere (for 

 instance, ABLA/CLUN) occurred near ABLA/VASC or 

 ABLA/XETE, Armillaria was present as shown by the 

 triangles (auxiliary plots with, random plots without) on 

 figure 1. 



Epiphytic Rhizomorphs 



When Armillaria was found, records included presence 

 or absence of typical rot, fans, and rhizomorphs. Quan- 

 titative data about rhizomorph biomass were not recorded, 

 but variation in the ease of finding rhizomorphs was 

 evident. 



Rhizomorph occurrence on living hardwoods (or dead 

 portion of a living clump), dead conifers, and the various 

 species of living conifers showed significant variation by 

 chi-square analysis (table 3). Rhizomorphs were found on 

 about 40 percent of the healthy conifer root systems of 

 sapling or larger sized trees. There were also significant 

 differences between conifer species (significant hetero- 

 geneity chi-square in table 4), particularly with Douglas-fir 

 and grand fir. 



Table 2— Delineated habitat types and status of Armillaria spp. on 

 120 0.04-ha plots randomly located within 15 National 

 Forests of the Northern Rocky Mountains 



Average Percentage 



Habitat 



site 



Climatic 



Number 



with 



type^ 



index^ 



characterization 



of plots 



Armillaria 



PIPO/SYAL 



15. 



,5 



Hot and dry 



1 







PSME/JUCO 



9. 



8 



Hot and dry 



2 







PSME/VAGL 



14. 



,9 



Cool and dry 



2 



100 



PSME/CARU 



15, 



,2 



Hot and dry 



6 







PSME/VACA 



16 



.2 



Frost pocket 



1 







PSME/PHMA 



17, 



.7 



Warm and dry 



6 



67 



ABLA/VASC 



12 



.8 



Cold and dry 



8 







ABLA/MEFE 



14, 



.3 



Cold and moderate 



6 



83 



ABLA/ALSI 



14 



,6 



Cold and moderate 



2 



100 



ABLA/VAGL 



14 



.9 



Cool and dry 



3 



100 



ABLA/VACA 



15 



.2 



Frost pocket 



2 







ABLA/XETE 



15 



.8 



Cold and dry 



6 







ABLA/CACA 



17 



.4 



Cold and wet 



1 







ABLA/ACGL 



18 



.0 



Cool and dry 



1 



100 



ABLA/CLUN 



19, 



.8 



Cool and moderate 



5 



80 



ABL/VSTAM 



21 



.9 



Cold and wet 



1 







ABGR/LIBO 



16 



.5 



Warm and dry 



3 



67 



ABGR/CARU 



18 



.0 



Hot and dry 



1 







ABGR/XETE 



18 



.6 



Cool and moderate 



5 



100 



ABGR/VAGL 



19 



.2 



Cool and dry 



5 



100 



ABGR/CLUN 



21 



,0 



Cool and moderate 



12 



92 



ABGR/PHMA 



22 



.3 



Warm and dry 



6 



100 



ABGR/ASCA 



22 



.6 



Cool and moderate 



4 



100 



ABGR/SPBE 



24 



,1 



Hot and dry 



6 







THPL/ASCA 



21 



,3 



Warm and moderate 



3 



100 



THPL/ATFI 



21, 



.6 



Warm and wet 



1 



100 



THPL/CLUN 



21, 



.9 



Warm and moderate 



3 



100 



THPL/ADPE 



23, 



.5 



Warm and wet 



3 



100 



TSHE/CLUN 



22, 



,6 



Warm and moderate 



11 



91 



TSHE/GYDR 



22, 



,9 



Warm and wet 



1 



100 



TSHE/ASCA 



23, 



,8 



Warm and moderate 



3 



100 



'Species identification: PlPO = Pinus ponderosa, PSME = Pseudotsuga 

 menziesii, ABLA = Abies lasiocarpa, ABGR = Abies grandis, THPL = 

 Thuja plicata, TSHE = Tsuga heteroptiylla, SYAL = Symphoricarpus 

 albus, JUCO = Juniperus communis, VAGL = Vaccinium globulare, CARU 

 = Calamagrostis rubescens, VACA = Vaccinium caespitosum, PHMA = 

 Piiysocarpus malvaceus, VASC = Vaccinium scoparium, MERE = Menzie- 

 sia ferruginea, ALSI = AInus sinuata, XETE = Xeroptiyllum tenax, CACA 

 = Calamagrostis canadensis, ACGL = Acer glabrum, CLUN = Clintonia 

 uniflora, STAM = Streptopus amplexifolius, LIBO = Linnaea borealis, 

 ASCA = Asarum caudatum, SPBE = Spiraea betulifolia, ATFI = Athyrium 

 felix-femina, ADPE = Adiantum pedatum, GYDR = Gymnocarpium 

 dryopteris. 



^Average height at 50 years (meters) of all conifer species in the series 

 obtained from Cooper and others (in press); Pfister and others (1977); 

 Steele and others (1981). 



3 



