coring, ring counts, and accessing structural characteristics

(Old-Growth Definition Task Group 1986). An average of

three Douglas-fir trees in the dominant size-class were cored

on each site (Bingham and Sawyer, this volume). Age of

trees on young sites ranged from 24 to 99 years, on mature

sites from 100 to 200, and on old-growth sites 7200 years.

Eight of the young forest stands that we sampled had been

logged, and three were naturally regenerated after fire. All

mature sites were unmanaged. Moisture classification of oldgrowth terrestrial sites was based on mean percentage cover

values and the absolute constancy of particular shrub and

herb species (B. Bingham, pers. comm.). Only the old-growth

mesic sites were used for analysis of the terrestrial herpetofauna relative to forest age-class.

Landscape and macrohabitat variables-We use the term

landscape to describe variables that incorporated a broad

spatial scale (for example, elevation and distance from the

coast). We used the term macrohabitat for aspects of forest

structure and composition in general proximity to where

animals were sampled.

Plant species composition, structural features, and forest age

on terrestrial sites were gathered from three to five, 0.l-ha

circular plots in accordance with the methods described in

detail in Spies and others (1988) and Bingham and Sawyer

(this volume). All dead and down woody material with a

diameter 210 cm was measured. Values were averaged

among plots at each site and the means used to represent

that variable for the entire site. These data are reported as

macrohabitat associations.

Microhabitat variables-with each timed-search capture

we recorded type of substrate, vertical postion relative to

that substrate, the width and length of substrate objects (for

example, rocks, logs, or bark slabs), and the decay state of

logs and snags under 5 categories of decay from sound to

rotten (Maser and others 1979). Decay-class 1 was defined

as a newly fallen tree with intact bark, limbs, and twigs.

Decay-class 2 logs were sagging slightly, had intact bark,

with some large branches, but no twigs. Decay-class 3 logs

were sagging near the ground, with sloughing bark and no

large branches. Decay-class 4 logs were completely on the

ground, had little or no bark, and the wood was punky.

Decay-class 5 logs are well-decayed with soft, powdery

wood and massive invasion of roots and seedlings.

We estimated relative abundance of downed woody material by size (based on surface area) and decay-class for our

sites by pooling data across vegetation sampling plots within the same stands sampled for herpetofauna (data from

B. Bingham). These estimates included only woody material,

not bark, and were calculated separately for hardwood and

conifer species. These aspects of the habitat are reported as

microhabitat associations, and the data are presented as

frequencies of occurrence.

Sites Used for Analyses of Landscape and Habitat

Parameters

We used data from 42 terrestrial forest sites to compare

species richness, species equitability, relative biomass,

relative abundance by forest age- and moisture-class, and

structural aspects of habitat use. We omitted nine higherelevation, white fir-dominated sites and three sites on

serpentine soils because they differed greatly from our

remaining sites (appendix table 9). The high-elevation

sites were at the upper limit of the range of Douglas-fir

and contained a depauperate herpetofauna; the three serpentine sites were open, dry, and brushy with abundant

lizards, characteristic of early successional clearcuts. Of the

42 sites, half occurred in the Coast Range (coastal area) and

half were inland in the Klamath/Siskiyou Mountains (inland

area) (appendix table 9). Differences in species numbers and

relative abundance of the total herpetofauna, salamanders,

frogs, and reptiles, among forest age- and moisture-classes,

were analyzed by geographic area (coastal vs. inland). Although the coastal and inland sets of sites also showed a

latitudinal gradient, most of the species we examined range

across this gradient, therefore, we assumed no effect.

We used 39 stream sites for analyses of the aquatic herpetofauna relative to forest age and habitat variables (appendix

table 9). Captures from all three reaches on each stream were

totaled for this analysis.

Statistical Methods

No significant differences were found between years for numbers of captures per site for either the pitfall or timed-search

data (Welsh and Lind 1988) so we combined years for these

data. Comparisons of mean species richness among forest

age-classes were based on the combined pitfall and timedsearch data. We used mass data taken during pitfall sampling

to compare biomass among forest age- and moisture-classes.

In all other analyses of terrestrial herpetofauna we used data

from the timed searches.

We tested the null hypotheses of equality of animal (or species) abundance and biomass among forest age- and moistureclasses by geographic area (coastal and inland), and a lack of

association between numbers of animals and habitat variables.

We used a 2-factor analysis of variance (ANOVA) to test for

differences in species numbers and relative abundance of

higher taxa (orders) among age- and moisture-classes in each

area (Dixon 1985:BMDP, 2V). Analysis of the relation of

individual species to forest age- and moisture-classes were

397
restricted to those that were found on at least one-third of

sites. We incorporated results from an earlier analysis of

these data where relationships with forest age- and

moisture-classes within and among coastal and inland areas

were examined using one-way analysis of variance followed

by multiple comparisons (Welsh and Lind 1988). Two

species were restricted primarily to either our coastal

(California slender salamander) or inland area (Del Norte

salamander); their relations to habitat were analyzed only

within the appropriate area.

We used Jaccard’s similarity coefficient to compare species

composition among forest age- and moisture-classes (Sneath

and Sokal 1973: 131):

Sj= a ,

a+b+c

in which, for any two classes, a = number of species in

common, b = number of species in the first class only, and

c = number of species in the second class only.

Mean biomass for the most common species and higher taxa

is reported by forest age-class (coastal and inland areas combined), based on combined fall pitfall samplings from 1984

and 1985-a total of 115,200 trap-nights. We have no way

of estimating the actual area sampled by our pitfall grids;

however, we assumed that they sampled the same area on all

sites regardless of slope or topography. We emphasize that

these are not density data. We recognize that many species

are not effectively sampled by pitfalls (for example, snakes,

clouded salamanders, and treefrogs) and we do not assume,

even for those species sampled effectively, that all individuals in the grid area were captured. We present these data as

relative biomass. We used a l-factor analysis of variance

(ANOVA) to test for differences in biomass among forest

age- and moisture-classes (Dixon 1985:BMDP, IV).

Correlation and all-possible-subsets regression analysis were

used to examine the relationships of the herpetofauna to forest vegetation, structure, and landscape characteristics (Dixon

1985: BMDP, 9R; Neter and others 1989). Forest age and

geographic area (distance from coast) were included as continuous variables in this analysis. We analyzed a total of 36

biologically relevant variables relative to captures per personhour (timed search) of salamanders (all species combined),

reptiles (all species of lizards and snakes combined), and the

four most abundant species of salamander. We selected the

36 variables from an independently derived data set of over

60 measures of forest structure and composition (Bingham

and Sawyer, this volume) that we judged biologically relevant to the herpetofauna, and that reduced redundancy (such

as selecting hardwood log volume over hardwood log

weight). All-possible-subsets regression was performed on

subsets of 15 variables that were most highly correlated with

each species or species group but that were not highly intercorrelated (R < 0.80). For each species or group, we report

the best univariate and multivariate models with up to five

variables, based on maximum adjusted R2.

Chi-square goodness-of-fit tests were used to examine the

relation between the size, type, and decay-class of downed

wood available and the microhabitat associations of the total

herpetofauna and selected salamander species.

We emphasize that our inferences are drawn from observations and not experimental manipulations. Although our

results are described in the context of hypothesis-testing,

our study was primarily exploratory. Because the total

number of sites we sampled in each age- or moisture-class

was small, we caution against broad inferences. We report

actual P-values for our analyses so that readers may judge

the level of significance of any particular test result. For

purposes of discussion, we use alpha level < 0.05 to indicate

significance.

Results and Discussion

Composition of the Herpetofauna

We captured 6419 individuals by all sampling methods

combined from the 54 terrestrial and 39 aquatic sites; 97.6

percent were amphibians and 2.4 percent reptiles (table 1).

Most captures (88.1 percent) were salamanders, clearly the

dominant group among the forest herpetofauna of this region.

Bury and Corn (1987), using pitfall/drift-fence arrays in similar forested habitats in the Oregon and Washington Cascades,

also found salamanders to comprise a high proportion (51.9

percent) of the herpetofauna. Their data also indicated a high

proportion of frogs (42.5 percent) but most of these captures

resulted from intercepting groups of dispersing young-of-theyear at a few stands. Using these data to estimate the relative

abundance of frogs in the Cascade forests would probably

give inflated values, although we would expect frogs are

probably more abundant there than here because of the

higher and more consistent precipitation in Oregon and

Washington.

We suspect that our sampling regime probably underestimated the reptile component of the herpetofauna because of

timing. The timed searches were performed in early to midspring, and the pitfalls were run in mid- to late fall corresponding with the fall rains. Both periods would favor the

capture of amphibians, but are, respectively, early and late

for the best reptile sampling. Combining total captures from

our timed-search and pitfall data, we found 2.4 percent were

reptiles. Bury and Corn (1987) ran their arrays from late

398
Table 1-A comparison of numbers of captures by order for

herpetofauna collected by 4 sampling methods in Douglas-fir/

hardwood forests of northwestern California and southwestern

Oregon from 1984 to 1986

Taxa

mature stands is a result of these sites being generally closer

to ponds and streams than other sites. This proximity to

riparian areas tended to increase the number of species

(particularly amphibians) detected relative to sites farther

from water.

Method

Sala- All

manders Frogs Lizards Snakes Turtles species

Pitfall traps

Timeconstrained

searches

Areaconstrained

aquatic

searches

Opportunistic

observations

1580 48 13 1 0 1642

3156 49 95 29 0 3329

914 508 0 0 0 1422

8 4 4 9 1 26

All methods

combined

Percentage

of total

5658 609 112 39 1 6419

88.1 9.5 1.7 0.6 <0.01 100

May through the dry summer months and into the fall; they

reported 5.6 percent of captures were reptiles. Also, they

used funnel traps with their pitfall arrays, which significantly

increased their capture of snakes.

Relations of the Herpetofauna to Forest Age, Moisture,

and Geographic Area

Species richness and species similarity-Combining all

methods, we found 31 species, 16 reptiles and 15 amphibians,

on the 54 terrestrial and 39 aquatic sites (table 2); the number

of species per site ranged from 1 to 13.

I Analysis (ANOVA) of numbers of terrestrial species among

geographic areas and forest age- and moisture-classes for 42

terrestrial sites (appendix table 9) indicated no significant

differences in species richness among age- or moistureclasses, but a significant difference between coastal and

inland areas and a significant interaction effect between

forest age and area (table 3). We found greater species richness in the Coast Range, Four of the five species detected in

the coastal area but not inland (four snakes species) are

known to occur in the vicinity of our inland sites. Only the

fifth species, the arboreal salamander, has not been reported

from this part of California (Stebbins 1985). Consequently,

differences in geographic areas do not appear to reflect true

biogeographic differences but are probably best explained as

an artifact of the difficulty of sampling for snakes (Welsh

1987, Welsh and Lind 1988). The significant interaction

effect between forest age and area results from detecting

more species in the mature age-class in the coastal area only.

We consider that the greater richness found on the coastal

Although we did not find significant differences in species

richness among forest age- or moisture-classes, we did find

notable differences in species composition. Using presenceabsence data, we calculated Jaccard’s similarity index for 10

randomly selected sites in each forest age-class. These results

(table 4) indicated higher similarity among species for the

mature and old-growth sites and lower similarity between the

young sites and both of the older age-classes.

These differences among age-classes are attributable to the

loss, after logging, of certain amphibian species that occur in

the older age-classes and the addition of several lizard species that prefer the open, drier, and warmer areas resulting

from clearcut logging. Bury and Corn (1988a), Raphael

(1988c), and Raphael and Marcot (1986) also found more

lizards in early successional stages after timber harvest.

Using the similarity index for four randomly selected sites in

each moisture-class indicated lowest similarities between the

wet and dry sites. Differences in species composition among

moisture-classes are also attributable to amphibian species

being replaced by reptile species on the relatively more xeric

and generally more open old-growth dry sites (table 4).

Species equitability-We examined species evenness or

equitability by plotting the numbers of captures for the 10

most abundant species vs. species rank, with data (timedsearch) from 10 sites in each forest age-class (only the mesic

sites from the old-growth set). We ranked the species from

most to least abundant along the x-axis. Results indicated

that the herpetofaunal assemblage of this area, like other

herpetofaunal communities both temperate and tropical

(Scott 1982), is dominated by a few species and hence displays low equitability (fig. la). We found little difference

among forest age-classes. A similar analysis for four randomly selected sites in each old-growth moisture-class

indicated no apparent differences (fig. lb).

Relative abundance-Analysis (ANOVA) of the number of

captures (timed-search data-total herpetofauna) by geographic

area and forest age- and moisture-class indicated significant

differences in total numbers of individuals among forest

age-classes (table 3). In a previous analysis of the same data,

we found that these differences were significant only between

the young and the old-growth sites (old > young, P < 0.05:

Welsh and Lind 1988) but not between the two older ageclasses.

399
Table Z-Total captures from all sampling methods and summary of analyses of relative abundance by forest age-class of 

herpetofaunal species in Douglas-fir/hardwood forests of northwestern California and southwestern Oregon 

Species 

SZZElpltig 

method(s)” 

Fmes and toads 

T%led frog 

western toad’ 

Pacific treefrog 

Footbill yellow-legged frog 

Red-legged frog’ 

Salamanders 

Northwestern salamandd 

Pacific giant salamander 

Olympic salamander 

Roughs!& newt 

Del Norte s&ma,,de# 

EIlSatilIe 

Black salamander 

Clouded salamander 

Arboreal salamandera 

California slender salamanderf 

Turtles 

Western pond tonle’ 

Lizards 

Western fence lizards 

Sagebrush lizardg 

Westem skid? 

Southern alligator lizard’ 

Northern alligator lizard 

SllakeS 

Robber boa’ 

Sharptail snake’ 

Ringneck snake’ 

RaCera 

California mountain kioesnakoa 

common garter makee - 

Western terremiial garter mkee 

Western aquatic garter snakeC 

Northwestern garter snake’ 

Western rattlesnakea 

AC.PF.TC.OP 

PF,TC 

TC,PF,OP 

PF,AC 

OP 

PF,TC,OP 

AC,PF,TC 

TC,AC,OP,PF 

TC,PF,AC 

TC,PF 

TC,PF 

TC,PF,AC 

TC.PF.OP 

PF’ 

TC,PF 

OP 

TC,PF,OP 

TC, 

TC,PF 

~:,PF.OP 

TC 

TC.OP 

TC 

TC.OP 

TC 

TC 

TC 

TC 

TC,PF 

OP 

Mean relative abundance 

among forest age-classes”. c 

0.001 A 

-.366 

,392 

,254 B 

,001 B 

,377 

,016 B 

,036 

,701 

,495 

-.014 

-.239 

400 
Table 3-F-statistics and P-values from Z-factor analyrs of 

variance of species richness (timed-search and pitfall data) and 

relative abundance of higher taxa of herpetofauna (timed-search 

data) by forest age- and moisture-class in coastal and inland 

areas 

Total number 

of species 1.48 12.83 3.36 0.75 0.50 2.98 

cw (.001) C.05) (.49) (.49) cw 

Tolal helpetofauna” 3.33 .oo 2.42 1.14 0.85 

co3 (.99) (.W (.30) (.45) 

A” datM”dUS” 3.08 28 .13 2.24 Lo7 .84 

(.04) WN VW C.14) (.32) (.45) 

A” frogs 1.01 1.48 2.84 7.41 2.33 7.72 

C.38) (-23) CW cow (.15) ww 

A” reptiles 2.68 2.87 .56 2.88 .81 1.76 

(.09) WI) (.57) (.09) (.38) W) 

Table 4-Jaccard similarity index values” for species of herpetofauna in 3 age-classes and 3 moisture-classes of Douglas-tirl 

hardwood forest 

Age-class YOUFIg Old growth 

Mature 

Old-growth 

Total number 

of species 

Moisture-class 

0.54 

.48 

16 (.62)b 

Old-wet 

0.71 

21 (.62) 

Old-mesic 

15 (.73) 

Old-drv 

Old-mesic 

Old-dry 

Total number 

of species 

.64 

.50 .67 

10 (.80) 13 (.69) 17 (.59) 

Species rank 

1 2 3 4 5 5 7 8 9 10 

Species rank 

Salamanders (timed-search data, all species combined) 

showed a significant difference among age-classes (table 3), 

also occurring in greater numbers on old-growth forest sites 

(old > young, P < 0.05: Welsh and Lind 1988). Of the eight 

species of salamanders sampled in sufficient numbers for 

statistical analyses, half were significantly more abundant 

on old-growth forest sites: Olympic salamander, Del Norte 

salamander, ensatina, and California slender salamander 

(table 2). 

401 
Although this analysis failed to detect significant differences 

among moisture-classes for the total herpetofauna or salamanders (table 3), in a previous analysis of these data, using 

the Games and Howell modification of the Tukey test, we 

found significant differences between the mesic and dry categories for both of these groupings (Welsh and Lind 1988). 

Frogs detected by terrestrial sampling (timed-search data, 

all species combined) were not significantly more abundanr 

in any forest age-class (table 3). We did find significant 

moisture-class effects and moisture-class and area interaction 

effects, however, these. results reflect the fact that terrestrial 

annrans (mostly Pacific treefrogs) were significantly more 

abundant on our mesic sites within the Coast Range (mesic > 

wet, P = 0.02: Welsh and Lind 1988). This result may be due 

to the fact that the mesic sites were generally closer to appropriate breeding habitat for treefrogs. Terrestrial anurans were 

absent from most of our inland sites, probably because the 

inland area is drier than the coastal area. These climatic differences between areas probably account for rhe significant 

interaction effect between moisture-class and area indicated 

for frogs (table 3). 

The forest age-class analysis did not yield significant relations for species of terrestrially sampled frogs (table 2). Intapreting our results for the abundance of frogs and aquaticbreeding salamanders relative to forest age- and moistureclass is confounded because we did not gather data on distances from our forest sites to suitable breeding habitat for 

these species. Proximity of breeding habitat is probably the 

single most important factor in determining the presence and 

relative abundance of these species. Bury and Corn (1988a) 

reported marked increases in numbers of these amphibians 

on sites near appropriate breeding habitat, regardless of 

forest age or moisture-class. 

Our aquatic sampling (area searches) detected two species of 

frogs, the foothill yellow-legged frog and the tailed frog. The 

tailed frog was significantly more abundant in streams associated with old-growth forests (table 2). 

Reptiles as a group did not appear to be significantly influenced by geographic area, forest age, or forest moisture 

(table 3). but our samples were small for these taxa. 

The only reptile species for which we had adequate numbers 

to compare abundances among forest age-classes was the 

northern alligator lizard. It was detected in similar numbers 

in all forest age-classes (table 2). 

Table S-Mean relative biomass, in grams, from pitfall sampling 

in different age- and moisture-classes of Douglas-fir/hardwood 

fwests In northwestern California and southwestern Oregon 

i145.60 - 

Mean biomass-We found a pattern of increasing biomass 

of terrestrial amphibian species from young to old-growth 

forest age-classes (table 5). Because of high variances among 

sites within both age- and moisture-classes, however, analysis 

(l-factor ANOVA) indicated only one species, the California 

slender salamander, to have significantly higher biomass on 

older stands (F = 6.99, P = 0.009). 

Ensatina accounted for 67 percent of the relative biomass 

(all sites combined) followed by the Pacific giant salamander at 16 percent. Some notable differences were found in 

some species’ relative contributions to abundance and 

biomass. The Pacific giant salamander had low mean relative abundance (0.182/1000 trap-nights), but its mean biomass exceeded that of the more abundant California slender 

salamander (1.23/1000 trap-nights) and the Del Norte 

salamander (3.65/1000 trap-nights) in most forest age- and 

moisture-classes (table 5). These two smaller salamanders 

accounted for 1 percent and 9 percent of the biomass, 

respectively. 

402 
Differences between the Coast Range and the Klamath

Mountains-Although we consider the difference in mean

number of species between coastal and inland areas (table 3)

to be an artifact of sampling difficulties rather than a reflection of true biogeographical differences, we did find

some evidence of real differences between these areas. For

example, we found significantly more black salamanders and

a pattern of higher abundance for many other species in the

Coast Range, although differences were not statistically significant for the other species (Welsh and Lind 1988). We

think that the explanation for these results lies in differences

in the suitability of habitats for the herpetofauna. Progressing

from the influences of the Pacific Ocean eastward toward

interior California is a pronounced environmental gradient

characterized by high precipitation, both rain and fog, and

mild temperatures along the coast, to lower precipitation and

more extreme temperatures-both highs and lows-farther

inland (Kahrl 1979:5, 13). Conditions along the coast create

more suitable conditions for forest-dwelling herpetofauna,

particularly amphibians, than do conditions inland. This

climatic gradient may have affected the number of species

(table 3), the increasingly patchy distribution of their populations, and their relative abundance (see below). For example,

we found the black salamander on 43 percent of coastal

stands versus 19 percent of inland stands (also see Lynch

1981). Either actual densities of individuals of many but not

all species are greater in coastal areas, or more equable

coastal habitats tend to increase the likelihood of detection of

individuals and of less-common species because of more

accessible retreats (near or on surface vs. subsurface cover).

Forest Landscape and Habitat Structure: Macrohabitat

Associations

Herpetofaunal abundances (timed-search data) were related

to macrohabitat characteristics of the forest by using correlation and regression analyses for 36 variables (table 6).

We report the five “best” single predictor-variables of animal

abundance, and the best multivariate models (up to five variables) for the most common species of salamanders and for

salamanders and reptiles as a whole (table 7).

Salamanders-As a group, salamanders were significantly

related to macrohabitat variables associated with late-successional stages of the forest (table 7): increasing densities of

large trees, particularly hardwoods, and large snags, and a

decreasing density of small conifers. Also of importance in

predicting salamander numbers were landscape variables

(table 6) indicative of relative moisture in the habitatdistance from coast (negative correlation) and presence of

seeps. The third type of variable that entered into our predictive models for salamanders were ground layer variables:

percentage cover of rock, a significant indicator of protective

cover, and percentage vegetation cover from 0 to 0.5 m high.

Table 6-Macrobabitat variables used for multiple regression

analysis

Landscape variables

Forest age (years)

Elevation (m)

Solar (KgCal/cm2[Langleys]/year)

Presence of streams

Presence of seeps

Distance from coast

Tree variables

Small conifers (all tree variables are stems/ha)

Large conifers (>80 cm diameter at breast height [d.b.h.])

Small hardwoods

Large hardwoods (>50 cm d.b.h.)

Small trees

Large trees

Basal area conifers (m2/ha)

Basal area hardwoods

Total basal area

Conifer importance (number of stems + basal area)

Hardwood importance

Canopy cover (ocular percentage cover estimate; mean of 3-5

200 m

2

 plots/stand)

Coarse woody debris variables

Large snags (>50 cm d.b.h. & >4.5 m tall)

Small snags

Large conifer logs (>50 cm diameter & >15 m long; pieces/ha)

Small conifer logs

Small hardwood logs

Large logs

Small logs

Large-log weight (metric tons/ha)

Small-log weight

Conifer-log volume (m3/ha)

Hardwood-log volume

Sound-log volume

Decayed-log volume

All-log volume

Ground layer variables

Litter depth (mm; average of 36-60 profiles/stand)

Rock (ocular percentage-cover estimate; mean of 3-5 200 m

2

plots/stand)

Ferns (ocular percentage-cover estimate; mean of 3-5 200 m

2

plots/stand)

0-.5 m vegetation cover (ocular percentage-cover estimate; mean

of 3-5 200 m

2

 plots/stand)

Vegetation cover was negatively correlated with salamander

abundance, but this may be a sampling artifact. Given equal

search time on otherwise comparable sites (timed-search

method), the site with the thicker understory might yield

fewer salamanders because of increased difficulty in finding

obscured cover materials (Welsh and Lind 1988).

403
Table 7-Results of multlple regression analysis for abundance of selected herpetofauna (tbnedsearch data) relative to macrohabitat variables (the 5 best Angle variables and the best multivariate models are given) 

Variables in model 

R’ 

C” (4.) F P 
Table 7-mntlnued 

Variables in model Ca 

R= 

(adi) 

Ensatina-We caphred more ensatina, by both timed search 

and pitfalls than any other species (table 2; Welsh and Lind 

1988). Significant relationships with large-tree and largehardwood densities (positive correlations) and small conifers 

(negative correlation) (table 7) are consistent with significandy higher abundances of ensatina on old-growth sites 

(table 2). Also significant in our predictive models for this 

species are variables indicative of protective cover: density 

of small hardwood logs @ositive correlation), and vegetation 

cover fmm 0 to 0.5 m tall (negative correlation-see explanation above, under salamanders). Presence of seeps, possibly an indication of relatively moister soils, was also important for ensatina. Previously (Welsh and Lind 1988), we 

found significantly more ensatina in the inland area. The 

appearance here in two of OUT models of a positive COTrelation with “distance from coast” (table 7) is consistent 

with OUT earlier result. This finding contrasts with the negative correlation for salamanders as a whole (table 7). Despite 

its ubiquity in the moist, cool forests of the Pacific Northwest 

and in contrast to other native salamanders, ensatina appears 

to have greater tolerance of the higher temperatures and 

lower moisture that are characteristic of interior forested 

areas of northern California. This tolerance is further evidenced by its distribution in other parts of California, particularly the Sierra Nevada, and the mountains of southern 

California (Stebbins 1985). 

Del Norte salamander-This species was found primarily 

on sites in the Klamath/Siskyou mountains, and a subset of 

sites within their geographic range was used in the analysis 

(a = 18). Del None salamander abundance varied positively 

with forest age, basal area of hardwoods, and large trees, and 

negatively with small conifers (table 7). a pattern indicative 

of late-successional forest. Percentage cover of rock was also 

important. This species was always found on sites with rocky 

soils, and most captures occurred in direct association with 

rock or under woody debris in contact with rock. The reason 

for the addition of two negatively correlated variables describing downed woody material in the multivariate models 

for this species (table 7) is not clear. 

California slender salamander--This species was found 

primarily on sites in the Coast Range, and a subset of sites 

within their geographic range was used in the analysis (n = 

21). The greatest amount of variation in numbers was accounted for by the landscape variables of elevation and 

distance from coast (negative correlations; table 7). A single 

cover variable-percentage cover of rock-and several 

variables indicating late-successional forest also proved 

to be significant. Significance of the late-sucessional forest 

variables is consistent with earlier analyses that found the 

slender salamander to ouxn in greater abundance on oldgrowth sites (table 2; Welsh and Lind 1988). 

405 
- 

Litter Rock Bark 

Substrate 

Logs 

We performed a second multiple regression on the slender 

salamander data to determine the importance of forest structural factors apart from the overriding factors of elevation and 

distance from coast (table 7). The second analysis brought 

in additional variables that covaried positively with latesuccessional forest, such as forest age and large hardwoods, 

but these variables were not significant. The cover variable 

sound-log volume and the presence of seeps were significant 

in oar second multivariable model, however. Bingham and 

Sawyer (this volume) found sound-log volume to be greater 

on old growth than young or mature sites, and the positive 

correlation with abundance of slender salamanders once 

again indicates an association with older forests. The negative 

correlation with presence of seeps is difficult to explain and 

may be spurious. 

Clouded salamander-Our analysis of data for this species 

indicated an association with cool, moist forest with positive 

correlations with increasing canopy cover and presence of 

seeps. Its abundance was also related to decayed woody debris (significant positive correlations with small-log weight, 

decayed-log volume, and small conifer logs). The remaining 

variables entering models are consistent with these asscciations (table 7). The low adjusted R2 for our best model 

(0.331) explained less than half the variation in abundance, 

however. 

Species 

Reptiles--Our analysis of reptiles is based on a total sample 

of 151 captures of 15 species, including both snakes and lizards (table 2). Lumping such a diverse array of species has 

obvious shortcomings, but it offers an informative contrast 

to macrohabitat use by the salamanders which dominate the 

forest helpetofauna of this region. Five significant variables 

entered the model; reptile abundance was negatively correlated with all of them (table 7). Collectively, high values 

of these variables indicated cool, moist, late-successional 

forests--clearly not optimal habitat for most reptiles. Additional variables that entered the regression models were also 

indicative of late-successional forests and negatively correlated with reptile abundance. The only variable that 

showed a positive correlation with reptile abundance was 

“solar,” a measure of incident radiation (Frank and Lee 

19&f, as would be expected with a group of heliothermic 

species. The adjusted R2 for our best model (0.270) indicated 

these variables explained little of the observed variation in 

reptile abundance. 

Forest Landscape and Habitat Structure: Microhabitat 

Associations 

Substrates-We analyzed all timed-search captures by substrate, combining them into four categories (fig. 2). Of 2769 

total captures, 87.5 percent were associated with dead, woody 

plant material-logs, snags, and bark. We analyzed the distrbutions of the five most commonly captured salamanders 

relative to these substrate categories (fig. 3). Ninety-nine 

percent of clouded salamanders, 89 percent of slender salamanders, 93 percent of ensatina, and 90 percent of roughskin 

newts were captured in association with dead, woody plant 

material. The slender salamander was more commonly encountered in the litter layer, and the Del None salamander 

more commonly captured among rocks, than any of the other 

salamander species (fig. 3). 

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