UNPUBLISHED MANUSCRIPT Prepared for the B.C. Forest ...web.unbc.ca/~wetbelt/docs/Radies_et_al_2008_FSP-Y083062.pdf · 1 The ecology, conservation status, and range and magnitude of

UNPUBLISHED MANUSCRIPT Prepared for the B.C. Forest Science Program

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NOT ALL OLD-GROWTH IS EQUAL: ECOLOGICAL ATTRIBUTES AND LICHEN 2

BIODIVERSITY IN AN INLAND TEMPERATE RAINFOREST LANDSCAPE 3

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By David N. Radies1. , Darwyn S. Coxson1., Chris J. Johnson1., and Ksenia Konwicki2. 5

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1. Ecosystem Science and Management Program 7

University of Northern British Columbia 8

Prince George, B.C. 9

Canada, V2N 4Z9 10

Email contact: [email protected] 11

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2. Timberline Natural Resources Group 13

1579 9th Ave. 14

Prince George, BC 15

V2L 3R8 16

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Running Title: NOT ALL OLD-GROWTH IS EQUAL 18

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Key Words: inland temperate rainforest; canopy lichens; cyanolichens; indicators; 21

relative soil moisture; old-growth; Thuja plicata; ecosystem-based management; old-22

growth threshold targets; ecological representation. 23


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Abstract. Windward slopes of the inland mountain ranges in British Columbia support a 1

unique temperate rainforest ecosystem. Continued fragmentation and loss of old-growth 2

forests in this globally rare ecosystem, has led to calls for the identification of 3

conservation priorities between remaining stands. We address this question by surveying 4

the relative abundances of 37 canopy macrolichens over a 70-km2 area of remaining old-5

growth (>140 years) forest in the upper Fraser River watershed, British Columbia, 6

Canada. To ensure adequate representation of landscape-scale old-growth forest 7

characteristics, we divided study plots equally among leading tree species and between 8

broadly defined sites of “wet” and “dry” relative soil moisture. Other variables included: 9

minimum mean annual temperature, mean annual precipitation, solar loading, and canopy 10

openness. We used two statistical techniques: Nonmetric Multidimentional Scaling 11

ordination for analysis of lichen assemblages and logistic regression to evaluate the 12

habitat conditions of a subset of 8 lichen species previously identified as “old-growth 13

associated”. 14

Ordination suggested that community assemblages were greatly influenced by 15

both the presence and abundance of bipartite cyanolichens. These communities 16

correlated well with increasing levels of relative soil moisture, temperature, precipitation, 17

and canopy openness, with little to no significant effect of tree leading species. Logistic 18

regression models identified relative soil moisture and temperature in all parsimonious 19

models. Leading tree species, in combination with moisture and temperature, were 20

important factors explaining the presence or absence of 5 of 8 modeled lichen species. 21

Our results emphasize the importance of maintaining representative areas of old-22

growth forests that are potentially less prone to natural disturbances such as fire. Of 23


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concern to the maintenance of lichen populations in old-growth inland temperate 1

rainforests is the continued forest harvesting of low-elevation water-receiving sites. We 2

recommend conservation of these wet topographic positioned areas to meet provincially 3

set ecosystem-based old-growth threshold targets for the purpose of maintaining 4

biological diversity and ecological integrity. 5

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INTRODUCTION 1

Wet-temperate rainforest ecosystems are widely recognized as an important 2

repository of biodiversity, particularly for organisms that live within the forest canopy 3

(Kitching et al. 1993, McCune et al. 2000, Castellón and Sieving 2007). In British 4

Columbia (B.C.), important steps have been taken for conserving large regions of coastal 5

temperate rainforests (Coast Information Team 2004). However, a second major wet-6

temperate rainforest ecosystem is found on the windward slopes of interior mountain 7

ranges. This inland temperate rainforest (ITR) has many unique characteristics, including 8

globally significant assemblages of canopy lichens (Goward 1994, Arsenault and Goward 9

2000, Goward and Spribille 2005), serving as habitat for endangered populations of 10

mountain caribou (Stevenson et al. 2001), and supporting headwater spawning runs for 11

many of the Fraser River salmon populations (Kew 1992). 12

A major difference between coastal and inland temperate rainforest ecosystems in 13

B.C. is that ITR ecosystems receive approximately half the annual precipitation of the 14

former. Therefore, the development of “rainforest” attributes in the ITR is more 15

dependent on patterns of snowmelt that influence ground moisture conditions. Eng 16

(2000) noted that stands located on cool north facing slopes showed a near 10-fold 17

reduction in stand destroying fire frequency compared to stands associated with warm 18

south facing aspects in inland mountainous forests of central B.C. Beaty and Taylor 19

(2001) reiterated this influence of aspect and further identified a reduced fire frequency in 20

lower slope, water-receiving topographic positions. DeLong (1998) reported that fire 21

return intervals in wet montane forests of the upper Fraser River watershed ranged from 22

244 to over 1600 years while Sanborn et al. (2006) found a median time since fire in wet 23


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inland temperate rainforests between 800-1200 years. These results suggest that 1

disturbance processes in the wettest portions of ITR are more similar to coastal temperate 2

rainforests, where single-tree gap dynamics dominate due to tree age (Lertzman et al. 3

2002), while in drier parts of the ITR, stand replacing fires will occur, yet infrequently. 4

In the upper Fraser River watershed, this resistance to fire in wet toe-slope valley 5

bottom positions has favored the development of forest stands that contain western red 6

cedar (Thuja plicata) trees of exceptional age (i.e., 1000 years old) and stature (i.e., 3 7

meters in diameter) (Benson and Coxson 2002). Goward and Arsenault (2000) identify 8

these forest stands as “antique”: sites where the last major disturbance event, such as fire, 9

happened well before the current generation of trees established. Preliminary studies 10

(Goward 2003) in the upper Fraser River watershed have suggested that forest stands in 11

water-receiving toe-slope positions contain highly diverse communities of arboreal 12

lichens. 13

Human impacts on ITR watersheds of the upper Fraser River valley have occurred 14

mostly in valley-bottom locations. Extensive forest harvesting (and accidental fires) 15

accompanied railroad development along the upper Fraser River valley in the early 16

1900s, followed by highway development on north facing slopes in the mid 1960s. Thus, 17

while DeLong (2007) identified a natural range of variability between 76-84% in the 18

cover of old-growth forests in wet mountain trench ecosystems of the upper Fraser River 19

watershed, current cover estimates of approximately 64-68% (Anonymous 2005) suggest 20

that these old forest types are under-represented relative to nonanthropogenic disturbance 21

regimes. These trends parallel those in coastal wet temperate rainforests, where historical 22


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harvesting has similarly targeted old-growth forests in valley bottom locations (Moola et 1

al. 2004) 2

Current landscape level management policies in the upper Fraser River watershed 3

specify an ecosystem-based management threshold of no less than 53% old-forest cover 4

greater than 140 years of age (Anonymous 2004). This target, influenced by both 5

ecological and socio-economic considerations, does not necessarily ensure that old-forest 6

stands of high biological value will be retained in future landscapes. Indeed, the opposite 7

may be true, in that the placement of transportation corridors through toe-slope stands in 8

the upper Fraser River watershed has resulted in disproportionate clear-cut harvesting of 9

old-forest stands in surrounding valley bottom positions. 10

In the U.S. Pacific Northwest and elsewhere canopy macrolichens have been used 11

as indicators of stand age (Hyvärinen et al. 1992, Campbell and Fredeen 2004) and 12

environmental conditions on forested landscapes (McCune et.al. 2000, 2002, Lidén and 13

Hilmo 2005). Furthermore, macrolichens have proven to be useful indicators of total 14

lichen diversity (Bergamini et al. 2005) and other taxa (Negi and Gadgil 2002) when 15

applied appropriately (sensu Niemi and McDonald 2004). Therefore, we suggest that a 16

landscape-level assessment of canopy macrolichens in ITR, could provide major 17

advances in our understanding of the role old-growth site and stand structural attributes 18

contribute to the biological integrity of these ecosystems. 19

We addressed this hypothesis by evaluating the composition and abundance of 20

canopy macrolichens in relation to structural and site attributes in 53 old-forest stands, 21

located within a 70-km2 area of the upper Fraser River watershed. Landscape-level 22

sampling was stratified to ensure equal representation of wet and dry broad relative soil 23


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moisture (BRSM) site conditions. Reasons for stratifying our study design by soil 1

moisture are twofold. First, soil moisture affects the ecology of forested landscapes 2

including the development and structure of forest stands (Lertzman 2002, Spies et al. 3

2006), plant species numbers (Zinko et al 2005), and underlying ecological processes 4

(Pastor and Post 1986, Turner 1989). Second, relative soil moisture is a forest 5

management tool, applied from site-specific forest practices (DeLong et al. 2003) to 6

coarse-filter landscape-level planning implementation using G.I.S. technology 7

(Anonymous 1999, Iverson et al. 2000). Furthermore, we stratified each of the two 8

BRSM categories into an equal number of “cedar-” (Thuja plicata), “hemlock-” (Tsuga 9

heterophylla), and “spruce-” (Picea glauca x P. engelmannii) leading stands, identifying 10

the potential influence of substrate on lichen diversity (Goward and Arsenault 2003). 11

Our analysis uses ordination approaches to examine community level responses of 12

canopy lichens, and logistic regression to examine autecological responses of a subset of 13

individual species identified by Goward (1994) as “old-growth associated”. 14

We hypothesized that lichen communities respond as ecological guilds or 15

functional groups (sensu Walker 1992) to environmental gradients within old-forest 16

stands. Following our null hypothesis, responses to environmental gradients will be 17

species-specific. Our research provides guidance on the interpretation of canopy 18

macrolichens as indicators of both microclimatic conditions and forest stand continuity in 19

old-growth inland temperate rainforests. We also address gaps in ecosystem-based 20

management strategies on the importance of site and stand-level old-growth 21

representation (Anonymous 2004, Coast Information Team 2004, Price et al. 2008). 22


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The ecology, conservation status, and range and magnitude of threats of lichens 1

are not well understood (Fazey et. al 2005). This study represents the first landscape-2

level analysis of arboreal lichen habitat attributes in old-forest stands of the inland 3

temperate rainforest of western North America. There is a pressing need for this type of 4

study, given the rapid conversion of representative valley bottom temperate rainforests to 5

plantation management and the attendant loss of old-growth associated species. 6

METHODS 7

Study Area 8

The study area is located in east-central B.C., Canada, in the upper Fraser River 9

watershed (Fig.1, Insert 1). This region is part of the inland temperate rainforest or 10

“interior wet-belt” (Stevenson et al. 2001) of the Rocky and Columbia mountains that 11

consists of: high elevation wet and very wet Engelmann Spruce Sub-alpine Fir (ESSF) 12

forests (in blue) (between 49º - 57º latitude); mid to low mountain elevation, wet and very 13

wet Interior Cedar-Hemlock (ICH) forests (in green) (between 51º and 54º latitude); and 14

extreme valley bottom locations of the very wet-cool Sub Boreal Spruce (SBSvk) forests 15

(in yellow) (between 53º and 55º latitude). 16

We focused on forests in the Slim variant of the very wet-cool ICH 17

biogeoclimatic subzone (ICHvk2) (DeLong 2003), and to a limited extent, adjacent 18

valley bottom forests within the SBSvk (Figure 1). ICHvk2 forests are dominated by 19

western redcedar (Thuja plicata), hereafter referred to as cedar and western hemlock 20

(Tsuga heterophylla), hereafter referred to as hemlock, with some Douglas-fir 21

(Pseudotsuga menziesii), hybrid white spruce (Picea engelmanni x P. glauca), hereafter 22


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referred to as spruce, and sub-alpine fir (Abies lasiocarpa), hereafter referred to as fir. 1

SBSvk forests are dominated by spruce and fir. 2

The distribution of remaining areas of old-forest in the ICHvk2 and SBSvk varies 3

greatly across the upper Fraser River watershed (Fig. 1). Many of the tributary valleys 4

have been heavily logged and have little remaining old-forest cover. Furthermore, based 5

on location of most logging clear-cuts, it is evident that harvesting patterns have targeted 6

low elevation wet broad relative soil moisture (BRSM) sites, most notably spruce and 7

secondly cedar. In general, wet BRSM sites are primarily found on north-facing slopes in 8

mid to lower valley positions, though they occupy a more topographically restricted band 9

in toe-slope positions on south facing slopes (i.e., compare Insert 2 and Insert 3 Driscoll 10

Ridge, Fig. 1). Wet hemlock-leading sites are more spatially confined, often occurring in 11

lower valley topographically flat positions with standing surface water. Spruce-leading 12

forests, both wet and dry, are found across upslope topographically cold locations (ESSF) 13

and extreme low elevation sites (SBS), in part, due to cold air pooling. 14

Mean annual precipitation of the ICHvk2 is 839.8 mm (374.3 mm in summer and 15

465.5 mm in winter) with a mean summer temperature of 14.7 °C and a mean winter 16

temperature of –12.1 °C. Recorded mean annual snowfall is 306.8 mm persisting on the 17

ground for up to 8 months of the year (Reynolds 1997). Slow-melting snow packs in 18

higher mountain elevations tends to keep soil moisture levels high in the ICH during the 19

summer months (Ketcheson et al. 1991), particularly on north-facing aspects. 20

Study Design 21

Field data were collected in summer 2004 and 2005. We selected 53 GIS 22

polygons to sample from a total of 120 randomly selected candidate polygons (Fig. 1). 23


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Selection criteria for eligible polygons (hereafter called stands) included: a) location in 1

the ICHvk2 and in the adjacent SBSvk (within 5 km of the ICHvk2) biogeoclimatic 2

subzones; b) forest greater than 140 years in age; c) cedar, hemlock, or spruce leading; d) 3

500 m or less from road access (for logistical purposes) and; e) at least 50 m from 4

cutblock edges, riparian areas, and deciduous forest types. We used the B.C. Ministry of 5

the Environment Predictive Ecosystem Mapping (PEM) database (an ecosystem mapping 6

conducted at a 1:50,000 scale; see Anonymous (1999)) and the B.C. Ministry of Forests 7

Vegetation Resources Inventory (VRI) database (a forest inventory mapping; see 8

Anonymous (1998)) to identify candidate polygons that met our selection criteria. 9

Sampling within old growth forests was stratified to ensure representation from 10

each of cedar-, hemlock-, and spruce-leading stands (using VRI), and from stands 11

representing both wet or dry BRSM conditions (using PEM). At each stand, we laid out 12

2 plots that shared a common centre. The lichen assessment plot was a rectangular 13

survey area 40m x 100m, with the long axis parallel with the slope to avoid marked 14

topographic changes. Each plot was assessed for 37 possible arboreal foliose lichens 15

(checklist adapted from Goward et al. 1994) using survey methods of McCune et al. 16

(2000). Each macrolichen species observed was given an abundance rating between 0 17

and 4 (with the exception of Lobaria pulmonaria): 0 = absent, 1 = rare [1-3 18

individuals/plot], 2 = uncommon [4-10 individuals/plot], 3 = common [>10 individuals], 19

4 = very abundant [covering more than half of available substrates]. For L. pulmonaria, 20

similar categorical measurements were made, yet because of its ubiquity and high 21

abundances in this ecosystem, we used a measure of “hand-size” (approximately 10 x 20 22


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cm2)/lichen plot in place of “individuals/lichen plot”. Melanelia and Parmelia lichens 1

were surveyed at the genus level. 2

The stand structure plot was a circular plot with a radius of 17.8 m. The purpose 3

of the stand structure plot was to provide more detailed information on the structural 4

components of the forest stand structure and RSM conditions. Diameter at breast height 5

(DBH) (1.3 m) was measured for all stems greater than 16.5 cm DBH, categorized by live 6

and dead stems and identified by tree species. Relative Soil Moisture (RSM) of each 7

stand was classified on a seven point scale using the moisture regime key in DeLong 8

(2003), which incorporates measurements of slope, mesoslope, aspect and soil texture. 9

Soil samples for texture analysis were obtained from within a soil pit dug to 10

approximately one meter at plot centre. 11

At each of 13 locations in each lichen assessment plot (equally spaced on 6 lines 12

radiating from plot center) four replicate measurements of canopy openness were taken 13

using a spherical densiometer. These measurements at each location were taken at 90° 14

intervals, and then averaged. We subsequently pooled all 13 averages to obtain the 15

overall “openness” of the stand. 16

Predicted mean annual precipitation and temperature for each stand was obtained 17

from the Canadian Forest Service (CFS) regional climate database (Hutchinson 1995). 18

We used mean monthly minimum temperature for the months March-October in our 19

analysis; this reflected the seasonal time period during which most lichen growth occurs 20

(Coxson and Stevenson 2007). Potential solar insolation was calculated using SAGA-21

GIS Version 2.0 (Scilands GmbH, Göttingen, Germany) solar radiation model. 22


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Data Analysis 1

Nonmetric multidimensional scaling (NMS) ordination was used to examine 2

trends in lichen community composition across stands (PC-ORD V. 4.0, McCune and 3

Mefford 1999). We then used a general linear regression model to evaluate the following 4

variables against ordination scores for Axes 1 and 2: temperature (TEMP), precipitation 5

(PRECIP), solar insolation (SOLAR), canopy openness (OPEN), relative soil moisture 6

(RSM), and basal area of cedar (BACw), hemlock (BAHw), spruce (BASx), and 7

subalpine fir (BASf). Variables were tested for multicollinearity (Stata Corporation 8

2002, College Station, Texas). For all variables, we used a tolerance score of < 0.2 to 9

indicate significant multicollinearity (Menard 2002). 10

We used logistic regression to identify important environmental factors that 11

influenced the distribution of lichens observed in our sample plots. We fit logistic 12

regression models to presence-absence data for Cavernularia hultenii, Lobaria retigera, 13

Nephroma isidiosum, Nephroma occultum, Platismatia norvegica, Peltigera collina, 14

Sticta fuliginosa and Sticta oroborealis, species previously identified as old-growth 15

associated by Goward (1994). Independent variables we assessed for each lichen species 16

included: categorized broad RSM (BRSM categorized as wet or dry see below) canopy 17

openness (OPEN), average minimum temperature (TEMP), average annual precipitation 18

(PRECIP), solar insolation (SOLAR), and categorized leading tree species (LEAD, 19

categorized as Cw, Hw, or Sx, see below) 20

Plots were classified as wet when the BRSM was above 4 on the 7 point relative 21

soil moisture scale, and dry if the BRSM was less than 4 (corresponding to mesic or 22

submesic sites in DeLong’s (2003) moisture regime key). When stands were classified as 23


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a 4 (mesic), vegetation and soil characteristics were used to separate wet versus dry 1

BRSM categories. When identifying the leading species (LEAD), a stand was 2

determined leading in cedar (Cw), hemlock (Hw), or spruce (Sx), based on the tree 3

species that had the highest Basal Area in the stand (to be consistent with VRI 4

classification methodology). 5

We tested thirteen combinations of independent variables that served as plausible 6

explanatory hypotheses for the distribution of each lichen species: 1.BRSM X OPEN X 7

TEMP X PRECIP; 2. BRSM X OPEN X TEMP X SOLAR; 3. BRSM X PRECIP; 4. 8

BRSM X TEMP; 5. LEAD X BRSM; 6. LEAD X OPEN X TEMP; 7. LEAD X OPEN X 9

PRECIP; 8. LEAD X OPEN X SOLAR; 9.LEAD X PRECIP; 10. LEAD X TEMP; 11. 10

OPEN X PRECIP X SOLAR X TEMP; 12. OPEN X PRECIP; 13.OPEN X TEMP. We 11

used Akaike’s Information Criterion with a correction for small sample size (AICc) 12

(Johnson and Omland 2004) to identify the most parsimonious logistic regression model. 13

All AICc values were subtracted from the lowest AICc value in each model set to derive 14

the AIC difference (AICc dif). We then calculated the AICc weights (AICcw) and 15

interpreted this value as the approximate probability that the model with the largest value 16

was the most parsimonious of the set (Johnson and Omland 2004). We calculated the 17

area under the Receiver Operating Characteristic (ROC) curve for the top-ranked models 18

(Munoz and Felicisimo 2004). ROC scores allowed us to evaluate the ability of the most 19

parsimonious model to predict the distribution of lichens on the landscape. 20

We used Multi-Model Inference (MMI) to determine the relative importance of 21

the predictor variables for each species (Johnson and Omland 2004). MMI uses the 22

AICcw to average the coefficients from all variables within the set of models for each 23


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lichen species and thus accounts for variation attributed to model selection uncertainty. 1

We used 95% confidence intervals, corrected for model selection uncertainty, to assess 2

the strength of effect of each predictor covariate on the dependent variable. 3

RESULTS 4

Of the 37 species and 2 genera (Melanelia spp. and Parmelia spp.) of arboreal 5

lichens surveyed within the 53 study plots, we found that 18 of the 19 cyanolichens were 6

more frequent and occurred with greater abundance in stands that had wet BRSM 7

conditions (Table 1). The only exception to this pattern was the cyanolichen Nephroma 8

resupinatum, which occurred infrequently (2 sites), but abundantly (greater than 10 9

thalli/site) in both wet and dry stands. The chlorolichens occurred with relatively even 10

frequency and abundance between stands with wet and dry soil moisture conditions, the 11

noticeable exception being Cavernularia hultenii, which had a much higher frequency of 12

occurrence in stands with wet BRSM conditions. 13

Stand ordinations showed clustering of bipartite cyanolichens in the upper left 14

quadrant of the plot (Fig. 2). This included regionally rare species such as Lobaria 15

retigera and Nephroma occultum to the more commonly abundant bipartate cyanolichens 16

such as Nephroma isidiosum, Pseudocyphellaria anomala, and Sticta fuliginosa. The 17

tripartite cyanolichen Lobaria pulmonaria, was found widespread throughout the 18

ordination, although it displayed some tendency of increasing abundance in the upper left 19

quadrant of the plot (Fig. 2). Most of the chlorolichens were widely distributed, showing 20

no strong placement preference along the two ordination axes. 21

Temperature and precipitation were significantly correlated with both axis 1 and 22

axis 2 ordination scores (Table 2). When fit to a linear regression, data for Axis 2 23


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demonstrated the best fit (R2 = 0.656), with the variables relative soil moisture (P = 1

0.002), temperature (P = 0.005), canopy openness (P = 0.010), precipitation (P = 0.020), 2

and basal area of spruce (P = 0.028) accounting for a significant proportion of the 3

variation. Only temperature (P = 0.001) and precipitation (P = 0.021) were correlated 4

with Axis 1 ordination scores (R2 = 0.548). Mean annual temperature, relative soil 5

moisture, basal area, and canopy openness co-varied (Table 3). 6

When fitting and assessing the suite of logistic regression models we noted few 7

similarities among the 8 old-growth associated lichen species (Table 4). The exceptions 8

were N. occultum and C. hultenii, for which the best predictive models consisted of 9

leading tree species and wet or dry BRSM status (although these two lichens selected for 10

different leading tree species). The variables associated with the most parsimonious 11

models for each lichen species were: temperature (6 species), leading tree species (5 12

species), relative soil moisture condition (4 species), openness (4 species), and 13

precipitation (1 species) (Table 4). ROC scores ranged from 0.7175 (P. norvegica) to 14

0.9183 (N. isidiosum), indicating a good to excellent fit for each of the lichen species 15

(Table 4). 16

Averaged coefficients suggested that all variables, other than precipitation and insolation, 17

had some influence (positive or negative) on the distribution of one or more old-growth 18

associated lichen species (Fig. 3). Dry BRSM status had a 0 to negative effect on the 19

presence of the eight lichen species, and wet BRSM status showed positive effects (both 20

with relatively small confidence intervals). Canopy openness (OPEN) showed 0 or 21

slightly positive effects. The temperature variable had the largest effect on the 22

distribution of N. isidiosum or S. oroborealis, though confidence intervals were quite 23


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large. In combination with temperature and/or BRSM, L. retigera, P. norvegica, and S. 1

oroborealis showed greatest affinities to stands leading in hemlock and to a lesser degree 2

cedar. C. hultenii, a chlorolichen, was related almost exclusively to hemlock and 3

negatively to both cedar and spruce leading stands whereas N.occultum, a cyanolichen, 4

showed preference to cedar dominated forests and a negative association with both 5

hemlock and spruce dominated forests. Spruce had either no effect or a negative 6

influence on the presence of the 8 lichen species we tested. As with temperature, 7

confidence intervals were often quite large for leading tree species (Fig. 3). 8

DISCUSSION 9

The first major question of our study was whether distinct assemblages of old-10

growth dependant foliose macrolichens were distributed equally across an old-growth 11

forest landscape of Inland Temperate Rainforest (ITR). A homogenous distribution of 12

lichens would suggest that arboreal lichens do not respond to stand characteristics other 13

than the criteria of reaching ages of 140 years or older. Our ordination plots show a clear 14

assemblage of lichen species within a representative subset of old-growth forests greater 15

than 140 years of age. These assemblages occurred mostly at low elevations with 16

topography that favored the accumulation of soil moisture. Of the old-forest associated 17

species identified by Campbell and Fredeen (2004) the following more regionally rare 18

species, C. hultenii, L. hallii, N. isidiosum, and N. occultum, were either limited to or 19

more frequent and abundant in stands with wet BRSM conditions. Other old-growth 20

associated lichens designated by Campbell and Fredeen (2004), such as H.rugosa, 21

H.vittata, L. scrobiculata, N. helveticum, N. parile, P. anomala and S. fuliginosa, were 22

more widely distributed in our old forest stands, but were still far more abundant on wet 23


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BRSM sites. A third set of old-growth associated lichens identified by Campbell and 1

Fredeen (2004), chlorolichen species such as Hypogymnia rugosa and P. norvegica, were 2

widely distributed in both wet and dry stands greater than 140 years of age. 3

From these results, we can identify an appropriate use of macrolichens as 4

indicators at this regional scale. First, the presence and high abundance of L. pulmonaria 5

across most of our research sites (wet or dry) proved to not be highly sensitive to site-6

specific conditions and lichen diversity in our study area (as suggested by Campbell and 7

Fredeen (2004). This result concurs with Kalwij et al. (2005) that suggested that 8

L.pulmonaria at the site level is not sensitive to landscape disturbances, but could be a 9

useful indicator of lichen diversity and disturbance frequencies when comparing among 10

regional landscapes. We postulate that within regional landscapes, the presence and 11

abundance of bipartate cyanolichens would serve as more appropriate indicators of 12

potential biodiversity “hotspots” (sensu Bergamini et al. 2005), canopy microclimate 13

conditions (Stevenson and Coxson 2008) and site disturbances (Goward 1994). We must 14

caution, however, that the proliferation of a guild of bipartite cyanolichen species is a 15

reflection of individual species’ ability to disperse and persist at a particular site. 16

Therefore, while we may identify that L.retigera and N.occultum are both found in 17

greater numbers and frequencies in sites of wet BRSM, we must also be aware that co-18

varying ecological attributes found in wet BRSM (i.e., soil moisture, temperature, and 19

site disturbance) could influences the presence of these regionally rare macrolichens 20

differently. Our data suggests that sites of wet BRSM status are biodiversity hotspots due 21

to a combination of optimal microclimatic conditions (due to lichen establishment 22

limitations) and potential stand continuity (due to lichen dispersal limitations). 23


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Although Glavich et al. (2005) pointed to temperature and moisture as major 1

predictors of cyanolichen diversity over a vast region of coastal wet temperate 2

rainforests, our correlation of environmental attributes with ordination scores suggests 3

that gradients of temperature and moisture play an important role in shaping cyanolichen 4

assemblages at finer scales of distribution. Temperature has long been inferred as an 5

important environmental variable in structuring ITR cyanolichen communities. Canopy 6

cyanolichens rapidly diminish in abundance as stand composition shifts from cedar-7

hemlock to spruce-fir with increasing elevation (Goward 1994). Studies on cyanolichen 8

physiology suggest that processes of carbon assimilation and nitrogen fixation are highly 9

rate-limited at low temperatures (Sundberg et al. 1996). Interactions with precipitation, 10

which can be viewed as a proxy for the duration of thallus hydration, are also fairly 11

straightforward. Lichen growth models are highly sensitive to the duration of 12

physiological activity (Sundberg et al. 1996). Coxson and Stevenson (2007) showed that 13

most growth in L. pulmonaria populations from the ITR coincides with precipitation 14

events in the spring and summer (the exception being some snowmelt events in the early 15

spring). Although thalli are often hydrated for long time periods in the late fall and 16

winter, they are commonly frozen and experience very low light availability, and hence 17

cannot realize much growth potential. 18

The opposing trends in temperature and precipitation with increasing elevation in 19

ITR mountain valleys would appear to have major constraints on the establishment of 20

canopy cyanolichens. However, site moisture and relative humidity are not related solely 21

to precipitation. The amount of slope above a position on the landscape is a major factor 22

in determining site moisture (Campbell and Coxson 2001). Relative soil moisture status 23


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was significantly correlated with axis 2 of the NMS ordination and was a significant 1

variable in a majority of best model sets predicted by logistic regression for individual 2

species. Where wet BRSM status coincides with warmer valley bottom conditions, 3

lichen communities escape the constraints that would otherwise be placed on their 4

development by regional gradients of temperature and precipitation. We hypothesize that 5

the greater relative humidity found within the lower canopy of these stands extends the 6

duration of periods of metabolic activity experienced by canopy lichens after 7

precipitation events. This, in combination with the form in which the precipitation falls 8

(i.e., rain versus snow), would identify more optimal habitat — particularly for 9

cyanolichens, which need direct contact with water to resume physiological activity 10

(Budel and Lange 1991). This is evident where one finds adjacent dry BRSM stands with 11

much lower canopy lichen diversity, notwithstanding very similar exposure to 12

temperature and absolute precipitation. 13

Old-forest stands that develop in wet BRSM areas tend to share many common 14

attributes. Basal areas of cedar, fir, and spruce are greater, presumably reflecting the 15

influence of subsurface water on tree growth, and indirectly, the greater exclusion of fire 16

as a major natural disturbance agent (Eng 2000, Beaty and Taylor 2001). Importantly, 17

wet stands tended to have a more open canopy structure, reflecting the greater role of gap 18

dynamics within old-forest stands in water-receiving positions (Benson and Coxson 19

2002, Lertzman et al. 2002, Radies and Coxson 2004). For canopy cyanolichens, this 20

combination of abundant light in a humid lower canopy environment creates ideal 21

conditions for growth and establishment (Coxson and Stevenson 2007). Spies and 22

Franklin (1991) postulated that receipt of groundwater flow and attendant transfer of 23


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nutrients was a major determinant of the overall growth, development and structure of 1

coastal wet temperate rainforests. Spies et al. (2006) further pointed out the importance 2

of recognizing these site-specific factors when developing plans for the conservation of 3

old-growth forests. Conversely, higher fire return intervals on upslope positions, 4

particularity those of south-facing aspects (Eng 2000), have most likely limited the 5

accumulation of rare lichen species — due to both dispersal limitations (Sillett et al 2000) 6

and unfavorable site and structural characteristics for lichen establishment (as discussed). 7

Our second major question was whether old-growth lichens, when examined 8

individually, would select similar environmental variables. The same variables played an 9

important role in predicting the presence or absence of individual species. All 8 of the 10

so-called “old-growth associated” lichen species had either temperature or BRSM as 11

major predictive variables in their best model sets (> 0.1 Akaike’s weight), with 6 of 12

these species having both predictor variables present. However, of the 8 species, only 2 13

species shared similar parsimonious models and 5 demonstrated varying affinities to 14

leading old-growth stand type — indicating habitat limitations for some lichen species 15

across our study area and the importance of stand representation. 16

Presence of the endangered cyanolichen species N. occultum was predicted best 17

by wet cedar-leading stands. Evidence suggests that undisturbed wet cedar-leading 18

stands have persisted for time periods well in excess of the age of the oldest trees, 19

fulfilling definitions of antique forest stands (Goward and Arsenault 2000). This 20

suggests that N. occultum is most likely dispersal limited, proliferating only in stands that 21

reach exceptional ages. Thalli of N. occultum, however, may also be influenced by 22

greater nutrient availability in water receiving (wet BRSM) stands. These sites receive 23


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groundwater flow from upslope catchment areas, potentially representing a landscape 1

level transfer of soluble nutrients. Further, on sites where cedar dominates, enrichment of 2

exchangeable soil calcium can occur through deposition of CaCO3 in litterfall (Graff et 3

al. 1999), a potentially important factor in subsequent enrichment of throughflow 4

precipitation as it passes over canopy foliage. 5

Most of the “old-growth associated” lichens that selected for leading species also 6

demonstrated wide confidence intervals around the respective coefficients. These large 7

intervals can be explained by the broad autoecological requirements of individual species 8

themselves and/or the broad scale at which forest stands were measured (in this case, 9

leading stand type). Importantly, our measurement of “leading-tree species” does not 10

identify the gradient of mixed conifer forest of cedar, hemlock, spruce and fir most often 11

found in these forest types. However, the association of lichens within this gradient of 12

mixed stand types could help explain the similar positive influence of both cedar and 13

hemlock leading forests on the presence of L. retigera, P.norvegica, and S. oroborealis. 14

This finding also suggests a broader ecological tolerance to stand conditions by certain 15

“old-growth associated” lichens, but not for all. 16

From the perspective of setting priorities for the conservation of canopy lichen 17

communities, the retention of representative old-forest stands in areas of water-receiving 18

valley bottom positions should be a high priority for land-use planners. This strategy will 19

also ensure old-growth ITR landscapes are more resilient by mimicking natural 20

disturbance regimes (sensu Drever et al. 2006) and protecting regions of temperate 21

mountain coniferous forests less prone to fire disturbance —such as north-facing aspects 22

(Eng 2000), moderate slope terrain, and valley bottom locations (Beaty and Taylor 2000). 23


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We also suggest that forest harvesting practices in these regions needs to be more 1

complex including variable retention single tree and small patch cuts that reflect the 2

natural range of variability in disturbance events that characterizes these wet old-growth 3

forest systems (Lertzman et al 2002, Radies and Coxson 2004). Across dry BRSM sites, 4

particularly those areas more prone to both insect outbreak and fire, clearcut harvesting 5

may be a more suitable prescription. We emphasize that harvesting strategies must 6

recognize spatial and temporal scale and pattern discrepancies between wet and dry 7

BRSM forest types. Ecosystem-based forest management would not “borrow” 8

disturbance patterns from one moisture type and prescribe it to another (i.e., frequent 9

clear-cuts in wet BRSM sites). 10

Current spatial representation of old-forests in protected areas in the ICHvk2 is 11

approximately 6%, — well below the ecosystem-based threshold target of 53% set for the 12

upper Fraser River watershed (Anonymous 2004). Given that many of the rare lichens 13

were only found in one or two wet sites (and not the same ones), it is highly unrealistic to 14

expect that current protected areas will maintain canopy lichen diversity within regional 15

landscapes. Furthermore, continued clear-cut forest harvesting in representative wet, low 16

elevation old-growth forest stands, will likely ensure a greater loss of macrolichen 17

biodiversity prior to reaching regionally set ecosystem-based old-growth threshold targets 18

(Anonymous 2004). Indeed, past harvesting of old-forest stands in wet BRSM sites may 19

already have incurred an “extinction debt” (Berglund and Jonsson 2005) in the upper 20

Fraser ITR. 21


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Conclusions 1

The application of indicator species requires an understanding of both the natural history 2

of the organism and the appropriate use of scale and measurement. Our data suggest that 3

at site-specific scales in mountainous old-growth ITR, bipartate cyanolichens could prove 4

useful in the determination of areas of high biological value due to both optimal site 5

conditions (relating to lichen establishment) and potential longevity of the stand itself 6

(relating to lichen dispersal). Given the reduction in the total area of these site types due 7

to anthropogenic activities, we recommend that old-forest stands in the upper Fraser 8

River watershed that have wet BRSM status be given immediate consideration for 9

protected area status. These sites represent significant biodiversity hotspots for canopy 10

lichens that are essential for the maintenance of biodiversity within larger regional 11

landscapes. The distribution of these organisms highlights the importance of 12

appropriately identifying soil moisture site discrepancies in old-growth forests for the 13

purposes of executing effective ecosystem-based management thresholds and strategies. 14

Therefore, when applying old-growth thresholds to temperate old-growth rainforests, the 15

question, “how much is really enough?” (Price et al. 2008), must also be coupled with, 16

“of what kind, in what location, and in what context?”. Otherwise, the objective of 17

setting thresholds targets for the purposes of maintaining biodiversity will most likely 18

miss its mark. 19

20

21


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ACKNOWLEDGEMENTS 1

We are grateful to M.E. Gauthier, C. Helenius, J. Kelly, D. Khurana and C. LeBoutier for 2

assistance with fieldwork. We thank S. Stevenson, P. Sanborn and C. DeLong for 3

reviews of draft manuscripts and assistance with the development of methods; T. Goward 4

for assistance with lichen identifications; and J. Campbell for review of the final 5

manuscript draft. The Canadian Forest Service supplied climate data. The Sustainable 6

Forest Management Network, the B.C. Forest Science Program, Mountain Equipment 7

Coop, and the University of Northern B.C provided funding. 8

9


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Table 1. Macrolichen presence/absence by number of sites containing each species and 1

abundance distribution (in brackets) in the upper Fraser River watershed. Abundances 2

denote frequency of occurrence of each species based on a three point scale: very low 3

equals 1-3 thalli, low equals 3-10 thalli, and common equals more than 10 thalli per site. 4

One exception, is L. pulmonaria*, which was measured by number of handful sizes (10 x 5

20 cm2) as opposed to thalli measurements. 6

Species

Dry Stand Plots

(27 sites total)

Wet Stand Plots

(26 sites total)

Number of site occurrences and occurrences by

abundance scale: very low (VL), low (L), common (C)

CHLOROLICHENS # of dry sites (VL, L, C) # of wet sites (VL, L, C)

Cavernularia hultenii 7 (5,2,0) 14 (7,3,4)

Cetraria cetroides 0 1 (1,0,0)

Hypogymnia austerodes 2 (2,0,0) 1 (1,0,0)

H. bitteri 18 (3,7,8) 17 (2,6,9)

H .imshaugii 0 1 (1,0,0)

H. metaphysodes 19 (4,4,11) 14 (7,3,4)

H .occidentalis 26 (0,1,25) 26 (0,0,26)

H .oroborealis 3 (3,0,0) 2 (2,0,0)

H. physodes 27 (0,0,27) 26 (0,0,26)

H. rugosa 19 (4,11,4) 20 (4,10,6)

H. tubulosa 27 (0,4,23) 26 (0,2,24)


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H. vittata 23 (4,9,10) 25 (0,4,21)

Melanelia spp. 15 (11,3,1) 15 (7,7,1)

Parmelia spp. 27 (0,0,27) 26 (0,0,26)

Parmeliopsis ambigua 26 (3,11,12) 26 (1,9,16)

P. hyperopta 27 (2,6,19) 26 (1,4,21)

Platismatia glauca 27 (0,0,27) 26 (0,0,26)

P. norvegica 18 (5,8,5) 17 (5,7,5)

Tuckermannopsis chlorophylla 27 (1,9,17) 26 (2,1,23)

T. orbata 7 (3,3,1) 2 (2,0,0)

Vulpicida pinastri 12 (6,4,2) 14 (7,4,3)

CYANOLICHENS # of dry sites (VL, L, C) # of wet sites (VL, L, C)

Leptogium burnetiae 0 1 (1,0,0)

L. saturninum 2 (1,0,1) 4 (2,0,2)

Lobaria hallii 0 3 (3,0,0)

Lobaria pulmonaria* 27 (1,1,25) 26 (0,0,26)

Lobaria retigera 2 (2,0,0) 12 (6,2,4)

Lobaria scrobiculata 19 (9,7,3) 23 (1,10,11)

Nephroma bellum 11 (4,5,2) 18 (7,7,4)

Nephroma helveticum 23 (4,6,13) 26 (0,3,23)

Nephroma isidiosum 11 (4,6,1) 23 (6,5,12)

Nephroma occultum 3 (3,0,0) 11 (10, 1, 0)

Nephroma parile 24 (4,7,13) 26 (0,3,23)


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Nephroma resupinatum 1 (0,1,0) 1 (0,0,1)

Peltigera collina 1 (0,1,0) 5 (3,1,0)

Polychidium dendriscum 0 7 (2,3,2)

Pseudocypellaria anomala 19 (8,8,3) 26 (3,6,17)

Sticta fuliginosa 17 (10,4,3) 23 (2,4,17)

Sticta limbata 0 2 (2,0,0)

Sticta oroborealis 3 (1,2,3) 12 (5,4,3)

Sticta wrightii 2 (2,0,0) 1 (1,0,0)

1

2


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Table 2. Multiple linear regression estimates for the log-transformed environmental 1

variables temperature, precipitation (mean minimum temperature, March to October), 2

solar loading, canopy openness, relative soil moisture, and basal area of cedar (Cw), 3

hemlock (Hw), spruce (Sx), and fir (Sf) calculated against Axis 1 (R2 = 0.548, f-ratio = 4

5.529, P < 0.001) and Axis 2 (R2 = 0.656, f-ratio = 8.701, P < 0.001) ordination scores (n 5

= 51) 6

Variable Coefficient SE t P

AXIS 1

CONSTANT 40.199 18.270 2.200 0.033

Temperature -6.139 1.726 -3.557 < 0.001

Precipitation -13.848 5.751 -2.408 0.021

Solar Loading 1.240 0.751 1.652 0.106

Basal Area (Hw) 0.180 0.127 1.420 0.163

Basal Area (Cw) 0.110 0.101 1.089 0.283

Basal Area (Sx) -0.146 0.137 -1.068 0.292

Basal Area (Sf) 0.209 0.199 1.049 0.301

Relative Soil Moisture -0.806 0.943 -0.855 0.398

Canopy Openness -0.301 0.479 -0.628 0.534

AXIS 2

CONSTANT -61.304 22.412 -2.733 0.009

Relative Soil Moisture 3.760 1.158 3.247 0.002

Temperature 6.139 2.118 3.002 0.005


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Canopy Openness 1.58 0.588 2.689 0.01

Precipitation 17.019 7.060 2.411 0.02

Basal Area (Sx) -0.383 0.168 -2.280 0.028

Basal Area (Hw) 0.263 0.155 1.694 0.098

Solar Loading 1.429 0.992 1.551 0.129

Basal Area (Sf) 0.322 0.245 1.317 0.195

Basal Area (Cw) 0.115 0.124 0.928 0.359

1

2


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Table 3. Mean and standard deviation of stand variables. N = 27 and 26 respectively for 1

dry and wet broad relative soil moisture (BRSM) stands in the upper Fraser River 2

watershed. 3

Stand

Type

Stand Variables

Mean

Temperature

(°C)1.

Minimum

Mar.-Oct.

Temperature

(°C) 1.

Annual

Precipitation

(mm) 1.

Solar Loading

(kWh/m2)1.

% Canopy

Openness2.

Mean SD Mean SD Mean SD Mean SD Mean SD

DRY 3.1 0.4 1.4 0.4 831.3 41.2 1208.7 238.0 8.6 2.8

WET 3.5 0.4 1.8 0.3 811.5 32.9 1218.0 108.2 14.1 6.3

Stand

Type

Stand Variables

Stand Basal

Area

(m2/ ha) 2.

Basal Area

Fir

(m2/ ha) 2.

Basal Area –

Cedar

(m2/ ha) 2.

Basal Area –

Hemlock

(m2/ ha) 2.

Basal Area –

Spruce

(m2/ ha) 2.

Mean SD Mean SD Mean SD Mean SD Mean SD

DRY 76.6 27.7 2.9 2.8 34.8 41.0 16.1 14.9 8.4 9.8

WET 80.2 48.8 4.0 4.9 43.1 64.9 13.7 21.3 11.0 11.5

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Table 4. Predicted best model sets (> 0.1 AICcw) for presence of the old-forest associated 1

macrolichens and receiver operating characteristic (ROC) results for best models in the 2

upper Fraser River watershed. Abbreviations for model variables are as follows: broad 3

relative soil moisture (BRSM); leading tree species (LEAD); canopy openness (OPEN), 4

mean annual precipitation (PRECIP) and; mean minimum temperature, March – October 5

(TEMP). Abbreviations in brackets ―cedar (Cw), hemlock (Hw) and wet BRSM (wet) 6

― represent categorical variables with greatest influence. 7

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Species Best Model Sets (>0.1 AICcw) AICcw ROC

Cavernularia hultenii LEAD (Hw) X BRSR (wet) 0.972 0.856

Lobaria retigera LEAD (Hw) X OPEN X TEMP 0.607 0.914

Nephroma isidiosum BRSM (wet) X OPEN X TEMP X PRECIP 0.419 0.918

Nephroma occultum LEAD (Cw) X BRSM (wet) 0.881 0.815

Platismatia norvegica LEAD (Hw) X TEMP 0.525 0.718

Peltigera collina BRSM (wet) X TEMP 0.333 0.737

Sticta fuliginosa OPEN X TEMP 0.458 0.850

Sticta oroborealis LEAD (Hw) X OPEN X TEMP 0.956 0.956

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Figure Legends. 1

Figure 1. Landscape distribution of old-growth cedar, hemlock, and spruce-leading 2

forests (separated by both wet and dry broad relative soil moisture conditions) in the very 3

wet cool Interior Cedar Hemlock (ICHvk2) and adjacent very-wet cool Sub-Boreal 4

Spruce (SBSvk) biogeoclimatic zones of the upper Fraser River watershed. Forests north 5

of the Fraser River are part of the Rocky Mountain formation, while forests south of the 6

Fraser River are part of the Columbia Mountain formation. Insert 1 indicates study 7

location in British Columbia, Canada. Insert 2 and 3 identifies old-growth forest type on 8

north and south-facing aspects of Driscoll ridge respectively. Reference points indicate 9

plot-sampling locations. 10

Figure 2. Overlay of species abundance in the upper Fraser River watershed in 2005 on 11

stand ordinations for the tripartate macrolichen Lobaria pulmonaria, and the bipartate 12

cyanolichens: L. retigera, Sticta fuliginosa, Nephroma isidiosum, Nephroma occultum, 13

and Pseudocyphellaria anomala 14

Figure 3. Coefficients and 95% confidence intervals of independent variables for each of 15

the eight “old-growth associated” lichen species in the upper Fraser River watershed 16

generated using logistic regression. Abbreviations of variables as follows: dry relative 17

soil moisture (dry); wet relative soil moisture (wet); canopy openness (Densio); mean 18

minimum temperature (Temp); Mean annual precipitation (Precip); solar loading (Solar); 19

cedar-leading (cw); hemlock-leading (hw); and spruce-leading (sx). 20

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Figure 1. 1


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Figure 2. 1


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Figure 3. 1

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Documents

UNPUBLISHED MANUSCRIPT Prepared for the B.C. Forest ...web.unbc.ca/~wetbelt/docs/Radies_et_al_2008_FSP-Y083062.pdf · 1 The ecology, conservation status, and range and magnitude of