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Home , Frog, Hazelton Mountains, Tailed frog

Forest Ecology and Management 124 (1999) 35±43

Riparian management and the tailed in northern coastal forests

Linda Dupuis*,1, Doug Steventon

Centre for Applied Conservation , Department of Forest Sciences, University of , Vancouver, BC, Canada V6T 1Z4 Ministry of Forests, Prince Rupert Region, Bag 5000, Smithers, BC, Canada V0J 2N0

Received 28 July 1998; accepted 19 January 1999

Abstract

Although the importance of aquatic environments and adjacent riparian habitats for ®sh have been recognized by forest managers, headwater creeks have received little attention. The , Ascaphus truei, inhabits permanent headwaters, and several US studies suggest that its populations decline following clear-cut logging practices. In British Columbia, this is considered to be at risk because little is known of its abundance, distribution patterns in the landscape, and habitat needs. We characterized nine logged, buffered and old-growth creeks in each of six watersheds (n ˆ 54). densities were obtained by area-constrained searches. Despite large natural variation in population size, densities decreased with increasing levels of ®ne sediment (<64 mm diameter), rubble, detritus and wood, and increased with bank width. The parameters that were correlated with lower tadpole densities were found at higher levels in clear-cut creeks than in creeks of other stand types. Tadpole densities were signi®cantly lower in logged streams than in buffered and old-growth creeks; thus, forested buffers along streams appear to maintain natural channel conditions. To prevent direct physical damage and sedimentation of channel beds, we suggest that buffers be retained along permanent headwater creeks. Creeks that display characteristics favoring higher tadpole densities, such as those that have coarse, stable substrates, should have management priority over less favorable creeks. Measures should also be taken to minimize ®ne sediment inputs from roads and stream crossings. # 1999 Elsevier Science B.V. All rights reserved.

Keywords: Riparian; Headwater; Creek; Gully; Buffer; ; Tailed frog

1. Introduction growth of any frog in North America, metamorphos- ing in four in the northern portions of its range, The tailed frog, Ascaphus truei, warrants conserva- and attaining sexual maturity at six to eight years of tion priority. It is the most primitive frog in the world age (Daugherty and Sheldon, 1982; Brown, 1990). (Nussbaum et al., 1983), and the only species in the The tailed frog also has highly specialized habitat Ascaphidae family; its closest relatives reside in New requirements: headwater creeks that must ¯ow - Zealand (Family: Leiopelmatidae). It has the slowest round because of the long larval developmental period (Nussbaum et al., 1983). The creeks must be cool to *Corresponding author. Tel.: +1-604-898-4770; fax: +1-604- accommodate this species' narrow temperature toler- 898-4742 ance. For example, the require temperatures of 58 E-mail address: [email protected] (L. Dupuis) to 18.58C, the narrowest range of all North American

0378-1127/99/$ ± see front matter # 1999 Elsevier Science B.V. All rights reserved. PII: S 0378-1127(99)00051-1 36 L. Dupuis, D. Steventon / Forest Ecology and Management 124 (1999) 35±43 (Brown, 1975). Creeks must also have low levels and is characterized by a mean annual precipitation of ®ne sediment, and a high water velocity (Welsh and of 1295 mm, with maximum rainfall and instanta- Ollivier, in press). neous discharges in the fall. The mean daily tempera- Its high degree of specialization renders the tailed ture in late summer (July and August) is 16.28C, and frog vulnerable to local extirpation or to population can reach 36.28C. Temperatures are below freezing declines following disturbances; at least 75% of Brit- from November to March. ish Columbia's watersheds, hence streamside riparian zones, have been partially developed (Bunnell and 2.2. Experimental design Dupuis, 1993). A number of studies in the United States have reported tailed frog population declines The study was a retrospective examination of creeks following clear-cut logging (Noble and Putnam, 1931; subjected to one of three logging treatments: (a) uncut Metter, 1964; Corn and Bury, 1989; Welsh, 1990; (old growth) forests; (b) clear-cuts (0±15 years) with Bury et al., 1991; Welsh and Lind, 1991), possibly unbuffered creeks; and (c) clear-cuts (0±15 years) with resulting from increases in water temperature. Brown 5±60 m forested buffers. and Krygier (1970) reported a mean annual tempera- We selected three permanent creeks of each treat- ture increase of 158C in a small watershed in Oregon's ment within six drainages (experimental blocks; Coast Range, one year after logging. Similarly, stream total ˆ 54 creeks): Shannon Creek, Carpenter Creek, temperatures increased by up to 3.28C in the summer Kleanza Creek, Copper River, Trapline Creek, and following logging in the Carnation Creek watershed of Clore River. This regional strati®cation helped control northern British Columbia (Holtby, 1988). Declines for potential differences among drainages. Creeks have also been attributed to increasing levels of ®ne ranged from 0.5 to 6.4 m in wet width (1.0±15.0 m sedimentation in streams following clear-cut logging in bankfull width) and 200±660 m in elevation. Most and road building activities (Corn and Bury, 1989; road-accessible creeks within each drainage were Welsh and Ollivier, in press). surveyed, thus the sampling density was high and The following study reports the ®rst effort to docu- likely representative of larval populations and distri- ment the tailed frog's habitat needs in the more north- butions within each drainage. ern portions of its range, in western Canada. The The term creek as used here is applied as a general objectives were to (1) summarize the creek features termforsmallwatercoursesgenerally¯owingingullies. which determine habitat suitability for at Gullies are V-shaped channels, con®ned or incised northern latitudes, (2) assess the potential effects of withinnon-¯uvialmaterials(glacialtill,rock,etc.),with logging operations by contrasting the density of larvae banks of at least 40% slope. Gullies generally occur in in forested and logged headwater creeks, and (3) the steep, headwater areas of a watershed. Streams, by evaluate the potential bene®ts of riparian buffer strips contrast, ¯ow within alluvial materials (materials of as a management option. their own deposition) and are found further downstream in the watershed (Ministry of Forests and Ministry of 2. Methods Environment, 1995a). The creeks in this study were almost exclusively ¯owing in gullies. 2.1. Study area 2.3. Amphibian sampling The study area is in the Nass and of the Hazelton Mountains east of Terrace, BC (latitude We sampled from 24 July to 24 August, 1994. The 548100, longitude 129800). The relief is rugged, with density of tailed frog tadpoles within a creek was a peaks ranging from 1980 to 2286 m in elevation and count of all the individuals encountered during active valleys draining into the . The mountains searches of three systematically placed 5 m reaches, of are underlain by a complex assemblage of igneous, which the ®rst was randomly situated. Reaches were volcanic and sedimentary rocks (Holland, 1976). 50 m apart from one another. The study falls within the Coastal Western Hemlock Searches were thorough and included an initial scan Biogeoclimatic Zone (Meidinger and Pojar, 1991), of the surface for active , followed by an in- L. Dupuis, D. Steventon / Forest Ecology and Management 124 (1999) 35±43 37 depth search of all the creek substrates: hand-raking by an analysis of residuals. Differences in mean sand and gravel, upturning cobbles and small tadpole density by treatment were tested by a rando- boulders, sweeping large boulder surfaces by hand, mized block ANOVA design, with drainage as the and scanning the moist banks. Surveys began at the blocking factor. This design uses the block±treatment downstream end of the reach, and proceeded in 1 m interaction as the error term (Zar, 1984). increments. Dip nets (of 1 mm mesh) were held immediately downstream of searchers to catch dis- 3.2. Relationship of creek parameters with tadpole lodged animals. A ®nal visual sweep of the reach often density revealed individuals which escaped detection during the dismantling of rif¯es. When the search was com- Univariate correlation was initially used to examine pleted the creek bottom was re-assembled. Tadpoles relationships between creek variables. A principal were measured, and returned to the top portion of the component analysis was then conducted to examine reach. which of the variables explained most of the vari- ance in the data. A multiple regression was done on 2.4. Creek characterization components with an eigenvalue greater than one, to test for their effect on tadpole numbers. The creek For each creek, we measured: water temperature characteristics de®ning the signi®cant components (8C), aspect (quadrants), average gradient (degree and were then determined based on their component percent), wet width (m), bank width (m), gully depth loadings, in conjunction with the initial correlation (m) and substrate composition (% cover). Substrate coef®cients. was classi®ed as sand (<2 mm), pebbles (2±64 mm), Only creeks without missing values were used cobbles (64±256 mm) or boulders (>256 mm), as for analysis. An level of p < 0.10 was deemed described by Howes and Kenk (1988). Substrate appropriate for testing differences, as this mode- was also categorized as rubble (angular material), rate provides a more sensitive test for the detec- gravel (round material), or mixed (rubble and gravel). tion of ecological trends (Toft and Shea, 1983; Toft, Fine organic debris (detritus) was recorded, as low (0± 1991). 2 mm deep, in <10% of the reach substrate), medium (0±2 mm deep, in 10±50% of the reach substrate), high 3.3. Effect of logging treatment on creek (on >50% of the substrate, coloured water column), or characteristics extreme (opaque water column). Finally, the percen- tage of wood debris (>1 cm in diameter) within a reach We tested for differences in the physical parameters was estimated and categorized as little (<10%), low of creeks by treatment (undisturbed, logged, or buf- (10±30%), medium (31±50%), high (51±80%) and fered) within each drainage, with a multivariate ran- extreme (>80%). Categories were based on a fre- domized block analysis of variance (MANOVA). quency distribution of the percentage estimates. All Creek parameters were grouped into two categories: measurements were taken from a transect across the (1) variables unaffected by perturbations (elevation, width of each reach's centre (2.5 m), and averaged for aspect, wet width); and (2) variables potentially in¯u- the creek. enced by treatment type (temperature, levels of ®ne and coarse organic material, and substrate composi- tion). This separation of creek variables was done to 3. Statistical analyses ascertain that the creeks within each treatment were of similar fundamental nature, thereby enabling a clear 3.1. Effect of logging treatments on tadpoles evaluation of the potential effects of treatment type on tadpole density and other creek parameters. If a Tadpole density in each creek was calculated as the MANOVA test was signi®cant, based on the Wilks number of tadpoles/(wet width  15 m). A log-trans- @ test statistic, individual parameters were examined formation of the data [ln(density ‡ 1)] was required to with univariate randomized block ANOVAs (SAS better meet the assumptions of the analyses, as shown Institute Inc., 1988). 38 L. Dupuis, D. Steventon / Forest Ecology and Management 124 (1999) 35±43

Table 1 Tadpole densitiesa in undisturbed and disturbed creeks of the Hazelton Mountains, British Columbia, in 1994

Treatment Drainage

Creek Shannon Carpenter Kleanza Copper Trap Clore Old 1 0.0 3.4 0.3 0.0 0.0 9.2 Growth 2 4.3 2.6 0.1 1.5 0.0 2.3 3 4.6 2.0 0.0 1.3 0.0 0.9

Buffered 1 0.5 0.8 0.6 4.4 1.1 0.0 Clear-cut 2 2.2 9.7 2.5 0.0 2.3 0.0 3 2.7 1.3 5.8 5.6 Ð 0.9

Clear-cut 1 0.0 0.0 0.2 0.0 0.1 0.0 2 0.0 0.0 Р0.4 0.7 0.2 3 0.0 0.0 3.1 0.0 0.0 1.0 a Number of tadpoles/(wet width  survey length).

4. Results Variables with the greatest apparent correlation to tadpole density were bank width, detritus, wood, We sampled 53 of the 54 selected creeks (the last rubble and ®ne sediment levels (Table 2); many creek was ephemeral), and encountered a total of 2149 of these variables are interdependent. Creek tadpoles and 20 subadult/adult tailed frogs. Tadpoles structure (bank width and levels of ®ne sediment, were present in roughly 60% of the creeks, and their wood and detritus) explained 28% of the variance density varied from 0 to 9.7 individuals/m2 (Table 1). in the data (PC 1: Table 3). Climate variables (elevation and water temperature) explained 4.1. Creek parameters 21% of the variance (PC 2: Table 3). Topo- graphy (aspect and gradient) explained 18% of the The creeks sampled in each treatment were physi- variance (PC 3: Table 3). Rubble substrates had cally similar: elevation, aspect, stream gradient, bank high loading values in components one, two and width, and the amount of rubble did not differ sig- three. Tadpole density was signi®cantly correlated ni®cantly between treatments (MANOVA: Wilks with principal components one and three (Table 4), @ ˆ 0.519, p ˆ 0.821, n ˆ 45 creeks without missing con®rming the simple correlation coef®cients of values). Table 2.

Table 2 A correlation table showing the basic relationship between creek variables

Variable Temperature Elevation Aspect Slope Width Rubble Detritus Wood Fines

Temperature 1.00 Elevation 0.75 1.00 Aspect 0.45 0.02 1.00 Gradient 0.05 0.09 0.37 1.00 Bank width 0.37 0.32 0.06 0.29 1.00 Rubble 0.30 0.27 0.21 0.52 0.75 1.00 Detritus 0.21 0.18 0.03 0.22 0.70 0.13 1.00 Wood 0.02 0.14 0.13 0.38 0.66 0.23 0.93 1.00 Fine sediment 0.35 0.32 0.47 0.40 0.04 0.34 0.59 0.57 1.00 Tadpolesa 0.24 0.05 0.36 0.06 0.69 0.62 0.72 0.80 0.80 a [ln (tadpole density ‡ 1)]. L. Dupuis, D. Steventon / Forest Ecology and Management 124 (1999) 35±43 39

Table 3 A principal component analysis demonstrating how various creek variables interacted

Creek variable Component loading

123456789 Wood 0.769 0.456 0.11 0.099 0.18 0.007 0.208 0.183 0.263 Detritus 0.728 0.495 0.229 0.143 0.155 0.189 0.031 0.003 0.303 Bank width 0.685 0.289 0.371 0.143 0.24 0.223 0.367 0.207 0.061 Fine sediment 0.683 0.019 0.342 0.017 0.54 0.273 0.039 0.211 0.071 Elevation 0.251 0.691 0.231 0.519 0.03 0.157 0.21 0.26 0.002 Temperature 0.329 0.657 0.439 0.064 0.262 0.094 0.373 0.209 0.043 Aspect 0.25 0.029 0.671 0.624 0.173 0.117 0.109 0.201 0.037 Slope 0.174 0.452 0.636 0.232 0.14 0.525 0.09 0.028 0.06 Rubble 0.426 0.485 0.481 0.249 0.376 0.263 0.16 0.217 0.087

Variance (%) 27.8 21.0 18.4 9.2 7.4 6.1 4.6 3.6 2.1

Table 4 A multivariate ANOVA testing the significance of principle components on tadpole density (n ˆ 34 creeks with no missing variables)

Variable Coefficient Standard error Standard coefficient Tp(two-tailed)

Constant 0.799 0.120 0.000 6.641 0.000 Factor 1 0.323 0.122 0.412 2.646 0.013 Factor 2 0.020 0.122 0.025 0.160 0.874 Factor 3 0.249 0.122 0.318 2.042 0.050

Source Sum-of-square DF Mean square Fp

Regression 5.505 3 1.835 3.733 0.022 Residual 14.748 30 0.492

Tadpole densities were more than four times substrate. There was no signi®cant relationship higher in creeks with <40% ®ne sediment than in between rubble and reach gradient; overall gradient creeks with large amounts of sand and pebbles (from headwater to fan apex) was not measured. (Fig. 1). Tadpole densities also decreased with increasing detritus levels in the water column (Fig. 2). An identical pattern was observed for wood levels: tadpoles were absent in wood-®lled creeks, whereas densities averaged 26.5 Æ 12.2 SE in creeks with <50% wood. Small creeks were more likely to be clogged: detritus-clogged creeks averaged 1.4 m Æ 0.2 SE in bank width (n ˆ 9), whereas creeks devoid of detritus averaged 4.5 m Æ 0.6 SE in size (n ˆ 25). Creeks with a rubble (®ne angular) substrate had a mean of 17 tadpoles Æ 4.6 SE whereas gravel or mixed (gravel ‡ rubble) creeks had a mean of 40.1 Æ 7.8. Small creeks were more prone to have rubble. More speci®cally, creeks with rubble sub- strates averaged 2.8 Æ 0.3 SE in width compared with Fig. 1. Tadpole density (averaged across drainages) Æ SE, in 5.2 m Æ 0.7 SE in creeks with a gravel or mixed creeks with low and high levels of fine sedimentation. 40 L. Dupuis, D. Steventon / Forest Ecology and Management 124 (1999) 35±43

@ ˆ 2.53, p ˆ 0.062, n ˆ 45). Organic materials were far more abundant in clear-cut creeks (Table 5): det- ritus levels were high (opaque water column) in 43% of clear-cut creeks as compared to 18% of buffered creeks and 0% of creeks in old growth. Similarly, clear-cut creeks were often completely covered in slash and coarse downed wood. Fine sediment levels (sand and pebbles < 64 mm in diameter) were consis- tently higher in clear-cut creeks (Table 5). Although temperature differed signi®cantly between old growth, buffered and logged creeks, all values fell within the range of tolerance of tailed frogs (ˆ168C).

Fig. 2. Tadpole density (averaged across drainages) Æ SE, in creeks with various levels of detritus (categories defined in 5. Discussion Section 2). 5.1. Natural variability in the density of tailed frog tadpoles 4.2. The effect of logging on tailed frogs and their habitat Tadpole densities vary greatly under natural con- ditions. This study suggests that their numbers are Tadpole density differed signi®cantly by logging primarily affected by creek structure (Tables 2±4), treatment (ANOVA: F ˆ 3.74; p ˆ 0.0612, n ˆ 53). namely creek width, substrate composition, and the Unbuffered clear-cut creeks generally had low den- amount of coarse and ®ne organic material. High sities (Table 1). On average, buffered creeks had proportions of ®ne materials (both sand and detritus), densities similar to those found in old growth. There in particular, can be signi®cant agents in mortality, as was, however, considerable variability in tadpole den- has been demonstrated for ®sh (Newcombe and Mac- sity within a single treatment type (e.g., some old- Donald, 1991), tailed frogs (Bury and Corn, 1988; growth creeks contained the largest densities of tad- Bull and Carter, 1996; Welsh and Ollivier, in press), poles, others contained none). One clear-cut creek had and other (Bury and Corn, 1988). Fine a density (3.1/m2) exceeding the average for undis- materials can adversely affect aquatic organisms by turbed or buffered treatments (Table 1). clogging gravel (Murphy et al., 1981; Hawkins et al., Treatment affected levels of detritus, wood, ®ne 1983), altering populations (Newbold sediment, and water temperature (MANOVA: Wilks et al., 1980), or changing the character of a channel

Table 5 Mean characteristics (Æ SE) of logged and undisturbed creeks in the vicinity of Terrace, British Columbia

Creek parameter Treatment

old growth (n ˆ 18) buffered (n ˆ 18) logged (n ˆ 17)

Elevation (m) 460 Æ 40 563 Æ 25 485 Æ 35 Creek width (m) 3.7 Æ 0.7 3.9 Æ 0.5 3.1 Æ 0.7 Predominant aspects E, S E, SE E, SE Temperature (8C) 12.9 Æ 0.5 13.1 Æ 0.3 14 Æ 0.04 Fine sediment (% cover) 34.7 Æ 539Æ 552Æ 4 Detritusa 0.33 Æ 0.14 0.73 Æ 0.2 1.78 Æ .29 Coarse woody debrisb 0.39 Æ 0.12 0.75 Æ 0.2 2.33 Æ .33 a Index of fine organic material in water column (0±3). b Index of the estimated percent cover of downed wood 510 cm (0±4). L. Dupuis, D. Steventon / Forest Ecology and Management 124 (1999) 35±43 41

(Bury and Corn, 1988). Welsh and Ollivier (in press) rotting of the root mat after logging leads to a decline suggest that the ®lling of interstitial spaces in the in rooting strength in the soil mantle, resulting in gully streambed may be particularly detrimental to tailed wall failures and open-slope landslides (Beschta, frogs. These spaces are primary microhabitats for the 1978). The erosion of road surfaces, ditches and tadpoles, offering them additional foraging substrates, cutbanks is also a signi®cant source of sediment, thermal and predatory refuge, and a means of escaping particularly when traf®c intensity is high. According bedload movements associated with seasonal ¯oods to Reid and Dunne (1984), heavily used roads produce and debris ¯ows. Altig and Brodie (1972) found that up to 130 times more sediment than abandoned roads. tadpoles avoided sand substrates (<5 mm) in a labora- Small creeks are generally not buffered, and they are tory setting. Our results con®rm the detrimental effect often crossyarded and ®lled with woody debris. Since of ®ne materials to tailed frog tadpole densities they lack the water power required to ¯ush ®ne organic (Figs. 1 and 2), particularly in small creeks, which and inorganic material, they are often the most lack the water power to ¯ush out accumulated severely impacted creeks. This presents a serious materials. liability to tailed frog larval populations when one Fine sediments occur naturally in creeks, and their considers the lack of protection applied to small abundance is governed by the nature of the sur®cial streams that are not ®sh-bearing (Forest and bedrock materials in channels and gully sidewalls. Management Assessment Team, 1993; Ministry of Competent rocks, such as granite, tend to resist ero- Forests and Ministry of Environment, 1995b). sion and break down into coarse substrates whereas The retention of buffers along creeks appears to less competent rocks, such as ®ne-grained siltstone or mitigate some effects of clear-cutting (Table 1). Buf- highly fractured rocks along faults, break down into fered creeks do not seem to experience infusions of silt, sand and rubble. Gullies incised in sur®cial ®ne sediment (Table 5). Newbold et al. (1980) materials may experience an increased incidence of obtained similar results in a study of macroinverte- shallow sliding failure of sidewalls following logging, brates, where was signi®cantly adding increased levels of ®ne sediment to channels. greater in streams with buffers (>30 m) than in streams The occurrence of rubble in some creeks in this study without buffers. Because tailed frogs do not tolerate re¯ected the presence of highly fractured bedrock in high temperatures and high rates of evapotranspiration gully sidewalls and channel ¯oors. Since these mate- (Claussen, 1973), buffers might also help to protect rials were readily available, they characterized creeks terrestrial juveniles and adults. Due to small sample with unstable beds (high bedload transport volumes), sizes and large variability in creek types, we could not and were strongly correlated with low tadpole test the difference between small and wide buffers. densities. According to Bull and Carter (1996), the presence of a 30 m buffer on either side of small creeks are a 5.2. Effects of logging on tailed frog tadpoles signi®cant variable in predicting the abundance of adult tailed frogs in Oregon. The tailed frog is clearly sensitive to logging prac- tices (Table 1). This is in agreement with studies in Washington, Oregon and northern California (Noble 6. Conclusions and Putnam, 1931; Corn and Bury, 1989; Welsh and Lind, 1991), which show greatly reduced abundances In summary, there is considerable variability in the of tailed frogs in streams in logged areas compared to density of tailed frog tadpoles, which indicates that streams in old-growth forests. further studies are needed to fully understand the Although the movement of sediments in gullies is species management needs at the habitat and land- complex and linked with hydrology, gradient, and scape levels. In this study, we showed that creek history of disturbance (Schumm, 1977), logging and substrate composition plays an important role in gov- road building are known to increase the frequency and erning tadpole numbers and that buffered riparian magnitude of sediment inputs to channel beds (Reid zones appear to be important in maintaining stream and Dunne, 1984; Sauder et al., 1987). The gradual integrity and tailed frog tadpole densities. Although 42 L. Dupuis, D. Steventon / Forest Ecology and Management 124 (1999) 35±43 water temperature increased following logging, it Brown, H.A., 1990. Morphological variation and age-class remained within the tolerance level of tailed frog eggs determination in overwintering tadpoles of the tailed frog, Ascaphus truei. J. of Zool., Lond. 220, 171±184. and larvae. Bunnell, F.L., Dupuis, L.A., 1993. Riparian habitats in British Columbia; their nature and role. In: (K.H. Morgan and 6.1. Management suggestions M.A. Lashmar, Eds.) Riparian Management and Research. Proceedings of a workshop held in Kamloops, B.C. 4,5 May, Tadpole habitat appears to be negatively affected 1993. Special Publication of the Fraser River Action Plan, primarily by increased sedimentation resulting from Environment Canada, and the Canadian Service Delta. logging disturbances. In small permanent creeks, the Bull, E.L., Carter, B.E., 1996. Tailed frogs: distribution, ecology natural rate of erosion and sedimentation should be and association with timber harvest in northeastern Oregon. maintained as close as possible. United States Forest Service, Pacific Northwest Research Buffering of small permanent creeks seems to Station, Portland, Oregon, Research Paper 497, pp. 11. greatly reduce the impact of timber harvesting, mostly Bury, B.R., Corn, P.S., 1988. Responses of aquatic and streamside amphibians to timber harvest: a review. In: Raedeke, K.J. (Ed.), by preventing yarding debris from entering the chan- Streamside management: riparian wildlife and forestry inter- nel, and by reducing the incidence of post-logging actions. Proceedings of a 1987 Symposium, February 11±13, failure into gully channels. Buffers should be designed Institute of Forest Resources, University of Washington, to minimize windthrow or other physical disturbances Seattle, Washington, Contribution 59, pp. 165±181. to the creek. If forested buffers are not retained, Bury, R.B., Corn, P.S., Aubry, K.B., Gilbert, F.F., Jones, L.L.C., 1991. Aquatic amphibian communities in Oregon and Wa- physical damage from crossyarding should be avoided shington. In: Ruggiero, L.F., Aubry, K.B., Carey, A.B., Huff, by falling and yarding away from channels. M.H. (Technical Coordinators), Wildlife and vegetation of Road and stream crossing construction may impact unmanaged Douglas-fir forests. United States Forest Service, tailed frog habitat downstream if not properly con- Pacific Northwest Research Station, Portland, Oregon, Gen. ducted. Measures to minimize sediment input, such as Tech. Rep., 285, pp. 353±362. Claussen, D.L., 1973. The thermal relations of the tailed frog, grassseeding, armouring ditchlines and culvert out- Ascaphus truei, and the Pacific treefrog, regilla. Comp. falls, and deactivating roads following logging, are Biochem. Physiol. 44, 137±171. important. Corn, P.S., Bury, R.B., 1989. Logging in Western Oregon: The nature of the bedrock geology and sur®cial Responses of headwater habitats and stream amphibians. For. materials of creeks can help determine headwater Ecol. and Manage. 29, 39±57. Daugherty, C.H., Sheldon, A.L., 1982. Age determination, growth, protection and management priorities within a given and life history of a Montana population of the tailed frog drainage. Creeks characterized by competent bedrock (Ascaphus truei). Herpetologica 38, 461±468. and coarse sur®cial materials, and which are not Forest Ecosystem Management Assessment Team, 1993. Forest subject to debris ¯ows, are most favourable for tailed ecosystem management: an ecological, economic and social frog tadpoles. An effort should be made to protect the assessment. U.S. Dept. 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