WATERSHED-LEVEL PROTECTION AND MANGAGEMENT MEASURES FOR THE MAINTENANCE OF ASCAPHUS TRUEI POPULATIONS IN THE SKEENA REGION
Report to:
Leonard Vanderstar, Habitat Protection Biologist MWLAP, Skeena Region Box 5000, Smithers, B.C. V0J 2N0
Date: March 31st, 2003
FROM:
BOX 612 , SQUAMISH, B.C., V0N 3G0 [email protected] PH: 898-4770 FAX: 898-4742
Ascaphus Consulting 22/11/12
Executive Summary
During the summer of 2002 a wide-ranging search for tailed frogs was conducted in the Kalum and North Coast Forest Districts (n=118). The goals were 1) to clearly define the boundaries of the coastal tailed frog’s (Ascaphus truei) northern range limit, 2) to determine the environmental factors affecting distribution along a trans-mountain transect from coast to interior, 3) to survey extensively within specific watersheds to gain insight on watershed level distribution, and finally 4) to sample elevational transects along individual streams to gain insight on sub-population vertical distribution patterns.
Map-derived variables were obtained for 2002 survey sites, as well as for earlier searches (Dupuis and Bunnell 1997) with comparable data, to investigate predictors of tailed frogs at the landscape- level. This analyses showed that basin area, basin ruggedness, aspect, elevation, and biogeoclimatic subzone are important predictors of tailed frog occurrence and abundance, and in the absence of site survey data, are useful in selecting good sites.
At the landscape level, our results indicate that tailed frogs are more consistently present in the Hazelton Mountains than in the Coast Mountains. Tailed frogs are found along streams draining areas up about 50 km2; however, they are most abundant in streams draining areas between 0.3 – 10 km2. For example, they are found along the entire mainstem length of streams such as Hardscrabble, Shannon and Trapline, but are most common in the perennial valley-side tributaries to these mainstems. Basin area is inversely related to basin ruggedness; thus, tailed frogs are most abundant in more rugged basins. The highest abundances are found in streams with basins steeper than 30% basin slope. Presence/absence data show a peak in probability of occurrence in moderate (31-50%) and moderately steep (51-70%) basins. The decline in occurrence in steep (71-90%) and very steep (91+%) settings is related to increasing bedload movement and mortality. Moderate ruggedness classes also support the widest range of tadpole age classes, suggesting the highest ecological fitness. Tailed frogs also do best in moderate climatic conditions. On the windward coast, occurrence was patchy and abundance reduced in the very wet and flashy creeks of CWHvm2. Moving inland, occurrence and abundance was greatest in the CWHws2, CWHws1, and MHmm2. In the Hazelton Mountains, where climate is continental, tadpole abundance was lowest on northern aspects.
Habitat variables collected during detailed searches permitted an assessment of local factors governing abundance of tadpoles. At the site level, occurrence was determined by physical habitat factors such as water temperature, reach slope, bankfull discharge, flashiness, substrate embeddedness, and canopy cover. Tailed frog abundance was highest in streams with channel gradients between 3-40%, stream temperatures between 8-12ºC, low to nil substrate embeddedness (>50% cobble diameter exposed), low to moderate channel disturbance regime, stream-side canopy cover of 20 to 70%, and older forests.
Physiographic and watershed level differences drive distinct site level stream responses: Coastal streams are more flashy, while very rugged basins are more flashy and subject to more channel disturbances; MH sites and northern aspects are cooler; unlogged or buffered sites are less disturbed. These results are used to provide best management practices and criteria for WHA site selection and design with the goal of optimizing abundance throughout the length of the stream reserve, and reducing long-term risk of disturbance to the channel from both natural and developmental hazards. Finally, a number of appropriate areas are proposed for WHA designation. Ascaphus Consulting 22/11/12
Table of Contents
Executive Summary ...... ii
Introduction ...... 1
Study Area ...... 1
Guiding Principles ...... 2
Background Information ...... 4
TAILED FROG HABITAT REQUIREMENTS ...... 4 Important Stream Characteristics ...... 4 Important Terrestrial Characteristics ...... 4 REGIONAL AND WATERSHED-LEVEL CONTROLS AND THEIR INFLUENCE ON TAILED FROG HABITAT QUALITY ...... 5
Methods ...... 7
PRE FIELD REVIEW AND SAMPLING DESIGN ...... 7
FIELD METHODS...... 8
HANDLING, MEASURING AND CLASSIFYING TAILED FROGS ...... 8
OFFICE METHODS...... 9
MAP PRODUCTION ...... 10
PHOTO DOCUMENTATION ...... 10
STATISTICAL ANALYSES...... 10
Results ...... 12
NORTHERN RANGE OF THE TAILED FROG ...... 12
LANDSCAPE-LEVEL ASSOCIATIONS ...... 14 Coast Mountains ...... 14 Hazelton Mountains ...... 16 SITE-LEVEL ASSOCIATIONS ...... 17
Analytical Summary ...... 19
Discussion ...... 20
DEFINITION OF A POPULATION (BASED ON CASE STUDIES) ...... 20 Ascaphus Consulting 22/11/12
LANDSCAPE AND HABITAT LEVEL ATTRIBUTES OF SIGNIFICANCE TO TAILED FROGS ...... 21 Basin Area ...... 21 Climate ...... 22 Hydro-geomorphology ...... 23 Logging History ...... 26 RANGE EXPANSION ...... 26
POPULATION TRENDS ...... 27
A Conservation Strategy ...... 27
EXISTING TAILED FROG WILDLIFE HABITAT AREA MODEL ...... 27
RECOMMENDED TAILED FROG WHA MODEL...... 28 WHA Design Concepts ...... 28 Wildlife habitat features ...... 28 Wildlife habitat measures, or best management practices ...... 29 SITE SELECTION CRITERIA AND CONSIDERATIONS ...... 30
PROPOSED WILDLIFE HABITAT AREAS ...... 33
EXISTING PARKS, PROTECTED AREAS AND PROPOSED RESERVES ...... 37
Conclusions ...... 38
Acknowledgements ...... 39
Literature Cited ...... 39
Appendix A: Example Site Form ...... 45
Appendix B: Statistical (PCA) Summaries...... 46
Appendix C: Photos ...... 52
Appendix D: Map ...... 53
Appendix E: Digital Information (report, database, statistics, map) ...... 53 Watershed-level Protection and Mangagement Measures for the Maintenance of Ascaphus truei Populations in the Skeena Region
Introduction
Since the tailed frog (Figure 1) was first documented in northern British Columbia in 1966 (Hazelwood 1993), it has become clear that the species is a key inhabitant of mountain streams throughout the Coast and Mountains Ecoprovince (Dupuis et al. 2000). Throughout the species’ range, numerous research studies have demonstrated the tailed frog’s sensitivity to forestry-related disturbances (e.g., Welsh and Lind 2002; Dupuis and Steventon 1999; Corn and Bury 1989). Presently, it is considered a blue-listed species (Conservation Data Centre 2001) and is on the identified wildlife list in British Columbia (BC Ministry of Forests and BC Ministry of Environment 1999). Under the Forest Act, wildlife habitat areas (WHAs) may be designated for identified wildlife.
Thus, this project was initiated to create a landscape and habitat predictive model for the tailed frog so that appropriate conservation tactics could be outlined and WHAs defined in the North Coast and Kalum Forest Districts. Our objectives were to: (1) refine the coastal tailed frog’s northern range boundary (Figure 2), which is within the Skeena Region study area; (2) conduct detailed sampling over a wide range of environmental variability to help define key survival attributes at the habitat, watershed and landscape level; based on our improved understanding of range and watershed level distribution, (3) propose relevant protection and best management strategies for A. truei. These conservation measures would ultimately serve to help maintain the species, as well as the hydroriparian integrity of headwater streams, in the Skeena Region; (4) review and critique existing WHA design guidelines for the tailed frog; propose revised WHA design guidelines suited to the tailed frog’s ecological requirements; and propose a number of WHAs.
Study Area
The study area (Figure 2) extends from Pitt Island in the west to the Howson Range in the east, and is bounded in the south by Douglas Channel and the north by Portland Inlet and Nass River. The western part of the study area, roughly west of the Kitsumkalum Trough, lies in the Coastal Mountains and Lowlands, while the eastern portion is in the Hazelton Mountains (Holland 1976).
There is a strong shift from maritime to continental climate eastwards across the study area. The entire region is mountainous, with summits at roughly 1200 m on the coast, rising to 3000 m inland. The study area encompasses various subzones of low to mid-elevation Coastal Western
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Hemlock forests, and associated Mountain Hemlock forests at mid to upper elevations (Meidinger and Pojar 1991). Terrain above about 1300 m has a cold microclimate supporting alpine tundra and cirque glaciation on northern aspects. Orographic effects produce heavy rainfall on the coast.
Figure 2. Study area and range of the tailed frog in the North Coast and Kalum Forest Districts
Guiding Principles
Tailed frogs reside in perennial mountain streams. Adult females deposit egg masses beneath large cobbles in summer, and hatchlings emerge in the following spring. At northern latitudes it takes up to four additional summers for tadpoles to mature into juvenile frogs and begin a life of lotic and terrestrial activity (Figure 3). Thus, tailed frogs, and especially the larval life stages, are vulnerable to stochastic events occurring in the stream environment. Moreover, streams draining the smaller and steeper watersheds typically inhabited by tailed frogs are more prone to extreme events than more gentle riverine habitats. It is intuitive then that patterns of occurrence,
Landscape-level Requirements for Tailed Frogs in the Skeena Region 2 Ascaphus Consulting 22/11/12 abundance, and population structure might be dependent on fluvial geomorphic factors. A number of geoclimatic hypotheses were first outlined by Dupuis et al. (2000) in this regard.
Figure 3. Various life stages and characteristics of the tailed frog.
The fluvial environment (Figure 4) is a complex, multivariate system acting over many scales and involving feedback and hysteresis effects. At the highest level are independent basin controls, namely physiography, climate, geology, vegetation/soils, and land use. These controls influence valley slope, or ruggedness, stream discharge, bank material strength, sediment load and texture. At the site level, are channel and flow variables that directly govern tailed frog distribution and abundance, namely sediment transport rate, bedform geometry, stream power, hydraulic geometry (width, depth, slope), and bed material size.
CL IM AT E G E OL O GY
In d ep en d en t B a sin BA SIN V E G E TAT IO N SO IL S Co n tro ls PH Y S IO GRA PH Y L A N D U SE
In d ep en d en t valley stream sediment load bank material composition Ch a n n el slope dischar ge (Q) inp uts and streng th (B) Co n tro ls bed material size (D) stream sediment D ep en d a nt po wer transport rate s w d Ch a n n el channel a n d width (w) depth (d) slope (s) F low bedform geometry G eo m etr y s D B D B D velocity (v) Figure 4. Interrelationships in the fluvial system from the landscape to the site level.
Landscape-level Requirements for Tailed Frogs in the Skeena Region 3 Ascaphus Consulting 22/11/12
This project attempts to explain patterns of tailed frog distribution and abundance in the context of the entire fluvial system. Other researchers have demonstrated significance of a particular component (i.e., geology or land use), but none have provided a general model. The Skeena Region is suited to this goal in that there are strong differences in basin physiography, climate, and geology extending northeasterly from Prince Rupert to Smithers, across the northern range of the tailed frog. Since land use effects have been well studied, we are less interested in that component for this particular study.
As outlined in the methods section, our study design explicitly incorporates measures of all the components presented in Figure 4. At the landscape and watershed level, variables are derived from maps and existing information; while at the site level, variables are obtained by direct measurement. These fluvial system variables are then tested against patterns of tailed frog abundance and population structure.
Background Information
Tailed Frog Habitat Requirements Important Stream Characteristics
Tailed frogs require perennial streams due to their extended period of lotic dependence. These streams must be cool (< 18° C) in the summer because all life stages have a limited range of temperature tolerances (Brown 1975; Claussen 1973). At the micro scale, Ascaphus larval densities are highest in streams dominated by boulders and cobbles, and lowest or absent in stream channels dominated by fine gravel (sand and pebble sizes)(Stoddard 2002; Adams and Bury 2000; Wilkins and Peterson 2000; Diller and Wallace 1999; Welsh and Ollivier 1998; Dupuis and Friele 1996). It has been demonstrated in the laboratory that tailed frogs select coarser substrates (Altig and Brody 1972). Coarser substrates may provide greater interstitial space in which larvae can forage and where all individuals can seek refuge from channel disturbance events and predators (Metter 1964; Welsh and Ollivier 1998). At the meso scale, streams typically inhabited by tailed frogs are greater than 3% in gradient, and are characterized by step- pool or cascade bedforms; these channel structures develop under conditions of low sediment supply (Grant et al. 1990). Perennial streams may have intermittent sections. Important Terrestrial Characteristics
The presence of buffers (see Dupuis and Steventon 1999; Stoddard 2002) and old forests within a watershed (Stoddard 2002; Welsh and Lind 2002), are positively correlated with larval tailed frog abundance. A rapid decline in the number of fine roots after trees are felled, and a sharp decrease in the tensile strength of the remaining roots can reduce the strength of the soil mantle to the point of failure (Beschta 1978), which may lead to gully wall failures and landslides, and subsequent sediment inputs to streambeds. Undisturbed forests in a watershed can also help to maintain the hydrological regime of the hydroriparian system (Jones and Grant 1996). Dupuis and Friele (2002), Stoddard (2002), and Welsh and Lind 2002) have indicated that the percentage of old forest in a watershed is also positively correlated with adult abundance. It is likely that the increased structural complexity of old forests maintains a cooler microclimate for terrestrial, post- metamorphic individuals to forage in. Coastal tailed frogs have been located up to 500 m from perennial streams under moist conditions (Dupuis, pers. com.; Bury, pers. com.).
Landscape-level Requirements for Tailed Frogs in the Skeena Region 4 Ascaphus Consulting 22/11/12
Regional and Watershed-level Controls and their Influence on Tailed Frog Habitat Quality
Surficial materials in the study area are derived from glacial and post glacial processes (Clague 1984). Deposits are thick along the major valleys and may influence stream substrate in those areas; however, surficial materials are thin in mountainous areas, where bedrock exerts the strongest control on channel substrate character. Thus, bedrock type has been found to be a strong correlate with presence/absence and abundance of the tailed frog (Dupuis et al. 2000; Wilkins and Peterson 2000; Diller and Wallace 1999).
The study area is underlain by two predominant geologic provinces (Hutchinson et al 1973): the Coast Plutonic Complex, underlying the Coast Mountains, and the Intermontane Belt, underlying the Hazelton Mountains. The Coast Plutonic Complex is a wide NW trending belt extending from the outer islands (i.e., Pitt; Map 1) east to the vicinity of Terrace. It consists of high-grade metamorphic and intrusive rocks, such as amphibolite, gneiss, quartz diorite, granodiorite, and diorite. These rocks are generally strong and coarsely jointed producing cobble-boulder substrates. The Intermontane Belt consists of Mesozoic volcanics and sedimentary rocks. North of Terrace, extending up to 25 km west of the Kitsumkalum Trough, are siltstone, argillite, greywacke and conglomerate rocks. The siltstone and argillite rocks are weak and produce abundant pebble-sand sized substrate. From upper Kitimat River north to the Seven Sisters and eastward are andesitic volcanics. These rocks are characterized by a red colour, and are typically densely fractured and readily weathered producing abundant pebble-sand sized substrate. Limestone conglomerate, greywacke, volcanic sandstone and chert are found locally in the vicinity of Usk, lower Copper River, Williams and Chist Creeks. These rocks are of intermediate strength and produce cobble-pebble substrates. Thus, controlling for ruggedness and climate, one would expect better habitat, in terms of both substrate character and geomorphic disturbance regime in streams underlain by plutonic rocks versus fine sedimentary and volcanic rocks. Watershed relief (height from valley bottoms to summits) increases gradually inboard from the Coast Mountains to the Hazelton Mountains, but ruggedness (basin steepness) is greatest along the spine of the Coast Mountains. In the vicinity of Prince Rupert, topography is gentle to moderate with peaks and ridges about 600 m above the valley floor. To the south, on either side of Grenville Channel, relief attains 800-900 m and slopes are moderate to moderately steep. Moving east toward the axis of the Coast Mountains, are the Kitimat Ranges encompassing valleys such as Scotia Creek and Big Falls south of the Skeena River, and Exchamsiks, Extew, and Shames to the north. Valleys in the Kitimat Ranges were heavily scoured by Pleistocene glaciers; ridges were rounded, and cirque floors were carved down to sea level. Although, valley to ridge relief is only on the order of 1000-1200 m, the Kitimat Ranges are notable for the steep, monolithic slabs that form the valley sidewalls. Basins in the Kitimat Ranges are moderately steep to very steep. To the east are the Hazelton Mountains with relief of 1200-1700 m, and moderate to moderately steep slopes. Since an increase in ruggedness is correlated with an increase in sediment delivery (Schumm 1954) and colluvial activity (DeScally et al., 2001; Jackson 1987; Kostaschuk et al. 1986; Ryder 1971), one might predict basin steepness is inversely correlated with tailed frog occurrence and/or abundance.
There is a strong gradient in average annual precipitation from west to east (Table 1), reflected in the shift from hypermaritime to drier hemlock forests as one moves inland. Based on valley bottom stations, average annual precipitation ranges from about 2000-4300 mm at coastal sites. This amount decreases to 1600-2200 mm at fjord heads, to 1300 mm just inland near Terrace, and to 523 mm at Smithers. There are no data for montane sites, but two to three times as much
Landscape-level Requirements for Tailed Frogs in the Skeena Region 5 Ascaphus Consulting 22/11/12 precipitation might be expected at higher elevations (Montgomery 1997), especially in windward locations where orographic effects are pronounced.
Table 1. Climate trends from the coast to the interior; valley bottom stations
Location Elev Total precipitation Percent as snow Degree-days (°C) (m) (mm) (mm) +18 -0 Bonilla Island 16 2088 3 0 43 Prince Rupert 91 3067 5 - - Ocean Falls 5 4301 4 27 92 Kitimat 128 2232 22 44 331 Kildala 30 2106 15 21 260 Kemano 70 1894 15 35 286 Bella Coola 18 1677 11 33 204 Terrace 217 1295 30 49 414 Smithers 523 510 42 16 871 Source: Canadian Climate Normals 1961-1990; Environment Canada (1990)
Throughout the region, the annual stream hydrograph (with the possible exception of low relief coastal drainages where data is lacking) is characterized by a prolonged summer snow-melt freshet (May-Aug). Peak flow gradually declines through the summer and fall to a low flow period during the winter months (Nov-Feb). During fall (Sep-Nov), intense storms result in instantaneous flood peaks that exceed diurnal flood peaks during the summer freshet (Environment Canada 1991). For areas within the maritime influence, fall peaks dominate the annual maximum instantaneous flood record. In drainages sheltered from direct maritime influence, or draining the lee slope of the Hazelton Mountains, summer peaks become predominant (Table 2).
Within the study area, July-August is the warmest time of the year. Comparison of degree-day statistics (Table 1; days > 18°C and < 0°C) illustrates that the moderating effect of the maritime climate is gradually lost between the coast and Terrace, with a sharp shift to a continental climate on the lee side of the Hazelton Mountains at Smithers. The decline in the freshet in July, together with the late summer temperature peak in July-August, suggest that late summer is the primary growth period for larval frogs. Due to the maritime influence, coastal streams may be warmer, while lower flows and colder temperatures may result in cool to cold streams on the leeward side of the Hazelton Mountains. In all regions, local conditions may cause significant variation, for example, on northerly aspects where persistent snow (neve) or glaciers are present in the headwaters, streams may have higher waterpower and summer stream temperatures may remain cool, limiting productivity.
Comparing streams of similar drainage areas (350-750 km2; Table 2), the unit area discharge decreases from 1-2 m3/s/km2 on the coast, to 0.5-1.0 m3/s/km2 in the vicinity of Terrace, to around 0.25 m3/s/km2 on the leeward side of the Hazelton Mountains. Another significant trend is the increase in unit area discharge with decreasing basin area; for example, Kitimat River yields 0.65 m3/s/km2 compared to 0.93 m3/s/km2 for Hirsch Creek, a tributary of Kitimat River. The basins presented in Table 2 are one to three orders of magnitude larger than the typical tailed frog stream
Landscape-level Requirements for Tailed Frogs in the Skeena Region 6 Ascaphus Consulting 22/11/12
(0.01 – 50 km2); thus, the trends illustrated here will be much more pronounced in the streams of interest to this study.
Table 2. Stream flow records for gauged streams along transect from coast to interior
Years Basin Maintenance Unit area Range of instantaneous Drainage of area flow discharge discharge (m3/s) partitioned (n) record (km2) (Q2; m3/s) (Q2; by season (n) m3/s/km2) May-July Sep-Nov Nascall 5 383 638 1.67 none 480-925 (5) Exchamsiks 28 370 442 1.20 190-195 (2) 190-570 (26) L. Wedeene 24 188 179 0.95 114 (2) 90-400 (22) Hirsch 25 347 322 0.93 125 (1) 155-800 (24) Kitimat 27 1990 1312 0.65 550-725 (3) 715-3000 (24) Kemano 17 583 437 0.75 360 (1) 150-800 (16) Zymagotitz 31 376 243 0.65 130-160 (3) 150-550 (28) Kitsumkalum 18 2180 462 0.21 320-880 (15) 400-700 (3) Kitseguecla 12 728 198 0.27 120-315 (7) 95-605 (5) Telkwa 14 368 92 0.25 50-130 (11) 90-240 (3) Source: Environment Canada (1991) Note: Q2 flows were estimated by extreme value analysis using the Gumbel distribution (National Research Council Canada 1989).
It has been demonstrated that floods can have a detrimental effect on tadpole populations (Metter 1968). Since floods account for the majority of bedload transport (see Knighton 1984), severe mortality (by trauma) probably occurs during extreme events. Re-organization of the step-pool structure (see Chin 1989) occurs periodically (e.g., every 5-100 years; Chin 1998), and is dependant on the recurrence interval of extreme precipitation events and debris flows. Thus, mortality risk is likely highest in streams in the Coast Mountains, especially in windward locations, or in small steep basins in general.
In summary, consider the channel disturbance regimes of similar sized creeks in the Coast and Hazelton Mountains: In the Coast Mountains, the combination of very rugged topography, competent, slabby bedrock, and intense rainfall produces a flashy runoff regime with high water power during peak discharges. From the tailed frog perspective, by mobilizing bedload more frequently, this extreme hydrologic regime probably offsets, to some degree, the advantage of competent bedrock and coarse substrates. In contrast, lower flows and waterpower, hence lower bedload mobility, probably mitigates the disadvantage of weak rock types in the Hazelton Mountains.
Methods
Pre field Review and Sampling Design
Sampling sites were selected based on a review of previous search effort (Dupuis and Friele 1996; Dupuis and Bunnell 1997), with three goals in mind: (1) to identify information gaps for
Landscape-level Requirements for Tailed Frogs in the Skeena Region 7 Ascaphus Consulting 22/11/12 the sake of refining the northern range of A. truei; (2) to facilitate the gathering of information on influential environmental variables, and (3) to assess preliminary WHA recommendations (see Houwers 2001). Due to the paucity of existing data in the North Coast Forest District, the general approach was to survey as many creeks in an area as possible using available road access. In the Kalum Forest District, where most of the previous surveys were based, generally at valley bottom sites, vertical transects along individual creeks were to be conducted. This was to allow an assessment of vertical trends in habitat quality, which is critical to the WHA design process. In addition, a wide range of streams sizes was to be sampled (basin areas from 0.1-100 km2) to define the watershed level distribution, also critical to the WHA design process. These strategies had not been employed in previous surveys. A site form tailored to this project was prepared once objectives were defined; it can be viewed in Appendix A.
Field Methods
At all sites, 30 min time-constrained searches (TCS) were conducted as outlined in the RIC Standards (BC Ministry of Environment and BC Ministry of Forest 2001). Parameters measured or estimated at each survey site included (see Appendix A, site form): Creek ID, date, weather, and recorder Handheld GPS location Elevation Aspect Reach gradient Water temperature Headwater source type (groundwater, neve, glacier) Bedrock geology (plutonic, sedimentary, volcanic) and local structure Description of channel condition including geologic processes (floods, sediment floods, debris flows, snow avalanches, braiding, avulsion) and supporting evidence; channel units (step-pool, cascade, riffle, pool); degree of formation (good, moderate, poor); and step forming materials (logs, boulder, rock). Channel geometry and substrate including; bankfull width and depth; low flow width and depth; substrate lithology, angularity (round, angular), texture (%rock, boulder, cobble, pebble, sand), and embeddedness (none, low, moderate, high). Diameter of the ten largest clasts moved by flow (i.e., imbricate clasts). Distribution of coarse woody debris and logging slash. Streamside vegetation including logging history (Y/N), buffer dimensions, stand age (0- 10, 10-50, 50-100, 100+ years, or subalpine-alpine), percent canopy and understorey. Tailed frog data (number, sex, size, by cohort) and time to first detection.
Creeks were sampled during a short time interval (20 days) and the searches were located far enough apart to ensure sample independence from the perspective of tailed frogs (tadpole drift, see Wahbe and Bunnell 2001; site fidelity, Daugherty and Sheldon 1982). From a geomorphological perspective, sites located far apart on the same creek are still considered independent because channel condition varies widely over short distances along the stream length (Knighton 1984).
Handling, Measuring and Classifying Tailed frogs
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All captured individuals were measured, sexed and aged when possible, and kept in a shaded bucket of cold water until a given search was complete and the channel bed roughly reassembled. A snout-vent length (SVL) measurement was taken of newly metamorphosed froglets, juveniles, and adults. Tadpoles were measured from snout to tail tip (total length; TL) and assigned to four developmental stages (Figure 3) that reflect their five-year in-stream residency (see Brown 1975). Eggs are laid in June following the freshet; hatchlings emerge in the fall. By the second fall they are considered to be at stage one in their development; they are small and limbless (cohort 1). In year three, tadpoles are significantly larger and show varying degrees of hind-limb development (cohort 2). By the fourth fall, tadpoles have acquired well developed hind legs (cohort 3) whereas by year five, their front limbs are well formed, their oral disc gives way to a biting mouth, and their tails begin to be resorbed (cohort 4), after which time they are classified as metamorphs.
Office Methods
For 2002 sites, biogeoclimatic, forest age, and elevation data were compiled by GIS query using digital databases provided by MWLAP. Physiographic provinces (Holland 1976) were categorised as Coast vs. Hazelton (see Map 1). Coast sites are more rugged, are underlain by plutonic bedrock, and receive more and more intense precipitation. Hazelton sites are less rugged, are underlain by a mix of bedrock types, and receive less precipitation than the Coast.
Basin ruggedness (Melton’s number; Melton 1965) describes average basin slope. It differs from a simple rise over run estimate of slope by accounting for basin shape using the square root of basin area. To calculate ruggedness (H/A1/2), GIS was used to derive the relief (H) and basin area (A) above the sample. For each sample, basins were manually digitized and the areas calculated by GIS. Ruggedness was categorized into 6 classes (after Howes and Kenk 1988): 0-5% (flat); 6- 30% (gentle); 31-50% (moderate); 51-70% (moderately steep); 71-90% (steep); and >90 % (very steep).
Stream discharge was calculated using the relationship cross-sectional area (A) times velocity (V) equals discharge (Q). Bankfull discharge is considered roughly equivalent to the two-year return flow (Q2) (Knighton 1984; Whiting et al. 1999). It is a reasonable estimate of the maintenance flow, or that which moves the majority of bedload, thereby determining the equilibrium channel geometry. Bankfull width and depth collected in the field were used to calculate bankfull area. Flood velocity (V) was derived using the approach of Costa (1983), whereby the mean diameter of the ten largest clasts (D90) moved by the flow is entered into the power function: V=0.18*(D90)0.487, where D90 is measured in millimetres.
Channel disturbance intensity was determined qualitatively based on observed channel processes and condition as described in the field methods, above. Four ranks were derived, as follows: (1) Very high - evidence of a debris flow within the last 3 years. Channel is scoured, or with fresh debris flow deposits, is subject to braiding and avulsion, and channel units are poorly formed. (2) High - chronic high-energy disturbance including snow avalanches, bouldery sediment floods, flashy discharge, and high bedload transport. Sidewall instability may be common along channel. Channel units are poorly or moderately formed. (3) Moderate – moderate disturbance including evidence of small, fined-grained sediment flood lobes, infrequent debris flow activity (time since is > 5 years) with revegetation of deposits, and more stable flow regime. Scattered sidewall instability may be present. Channel units are moderate to well formed.
Landscape-level Requirements for Tailed Frogs in the Skeena Region 9 Ascaphus Consulting 22/11/12
(4) Low - normal to stable flooding regime. Large substrates appear stable and are often mossed over, and bedload transport is moderate to low. Channel units are well formed. Flashiness, or the difference between groundwater derived base flow and runoff flow, was calculated by the ratio between bankfull cross sectional area and low flow cross sectional area. Low values of the ratio indicate a stable flow regime, while larger values indicate flashy regime.
Since intense channel disturbances cause mortality, there is an increased probability of death for an individual with increasing residence time in the lotic environment, and this might lead to a skewed life stage structure in higher disturbance regimes. Thus, three life-stage structure rankings were derived: (1) cohort 1 only, indicates chronic or recent mortality; (2) cohorts 1 and 2; and (3) cohort 3 or older are present, suggesting good fitness and good breeding habitat. This measure should be viewed with caution, as abundance of younger age classes can also be a sign of population increase.
Map Production
To illustrate search effort in the Skeena Region, and to refine range limits, all location data from this and previous surveys (Dupuis and Bunnell 1997; Hazelwood, unpubl. data) were coded as present or not-detected, and plotted on a 1:250 000 scale base map using albers (Map 1). Samples provided by Hazelwood consist of his observations, primarily by visual encounter survey, plus some incidental records from fisheries biologists, consultants and mushroom pickers. For visual reference on Map 1, physiographic provinces (Holland 1976), existing reserves of various kinds, and locations of stream gauging stations are shown. Locations of proposed WHAs are also indicated, but potential boundaries of WHAs are not shown in detail, as that work is considered beyond the scope of this project.
Photo Documentation
Annotated photos are provided as an Adobe Acrobat File on a CD in Appendix C.
Statistical Analyses
The data used in the analyses included records from the summer of 2002, on which this report is based, and time-constrained searches conducted by Dupuis Consulting (Dupuis and Bunnell 1997); both datasets had comparable site description and abundance data. Independent variables were selected on the basis of representation within the dataset, and known relevance to tailed frog biology (see discussion). Following fieldwork and refinement of the range, all sample sites beyond the assumed range limit were deleted for the purpose of statistical analyses.
Variables were organized into landscape or site level categories based on whether they were derived from a map or in the field (Table 3). Landscape level (map- derived) variables were stratified into Coast Mountains and Hazelton Mountains physiographic regions, following the rationale presented in the discussion above, and analysed separately. Within each region tests on tadpole occurrence were performed using the whole data set (all basins), and then on a subset of basins less than 10 km2 in area because these small basins are geomorphically different from large ones. They are typically drained by steep creeks that flow on coarse colluvial beds whereas large basins are drained by low gradient rivers flowing on alluvial beds. Although tailed frogs are found along rivers, creeks are more characteristic of tailed frog habitat than rivers. Site level (field-derived) variables were not stratified.
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Table 3. Map and field variables included in the Principal Components Analyses
MAP FIELD Derivation/description of values (units) Physiography Coastal (windward; steep; competent); Hazelton (leeward; variable geology) BGC zone Biogeoclimatic subzone Basin area Digitized map area (m2) Basin (m/m); coded as 1=0-5%, 2=6-30%, 3=31-50%, 4=51- Ruggedness 70%, 5=71-90%, 6=>90% Aspect Compass orientation of slope (degrees) Elevation GIS-queried (m) Geocode Geocode 1=plutonic, 2=weak volcanic, 3 = fine sedimentary, 4=mixed lithology Rslope Reach slope (%) over a distance of 50 m Wtemp Water temperature ( C) Channel Index based on qualitative rank: 1=extreme; 2=high; 3= Disturbance moderate; 4= low Intensity Embeddedness 0=none; 1=low; 2=moderate; 3=high Logged 0=no; 1=yes; 2=partial (one-side of creek) Riparian cover Percent tree cover in riparian zone (%; left bank + right bank / 2) Discharge Stream discharge (m3/s) Flashiness Bankfull versus low flow ratio
Principle Component Analysis (PCA) was employed to investigate the relationship of tailed frogs to landscape- and site-level parameters, because this test (1) does not require normality; (2) can handle categorical and ordinal variables; (3) permits the evaluation of many variables at a time; and (4) can integrate many related measurements into summary components (EPA 2002).
Once independent variables were organized into principle components, these components were defined by the variables with the highest component loadings (Appendix B). Those with an Eigenvalue greater than 1 were examined for their influence on tailed frog occurrence and abundance. Occurrence (presence/absence) was analysed using logistic regression. Abundance was analysed using multiple regression. Count data from all life stages of the tailed frog show a negative binomial distribution (tadpole skewness=1.66; variance much larger than the mean), including numerous zeros. This is a common occurrence in ecological frequency counts (White and Bennetts 1996). Sites with no occurrence were thus excluded from multiple regression and
Landscape-level Requirements for Tailed Frogs in the Skeena Region 11 Ascaphus Consulting 22/11/12 tadpole density was log transformed to meet the assumptions of normality and homogeneity of variance (Krebs 1989). Any further exploration of relevant variables was done using Goodness of Fit, Logistic or Linear Regressions, or ANOVAs depending on whether the dependent and independent variables were nominal, ordinal or measured, and based on the measure of central tendency and dispersion for each variable.
Statistical analyses were performed using SAS software, Version 8.1 (SAS Institute 2000). An alpha level of p < 0.10 was deemed appropriate in testing for significance of habitat variables, as it provides a more sensitive test for the detection of ecological trends (Toft and Shea 1983, Toft 1991).
Results
Searches in 2002 enabled us to fine-tune the species northern range limit and collect additional information on variables deemed relevant to their distribution and survival. For increased power 28 time-constrained searches (190 tadpoles) from the 1990s, with comparable tailed frog abundance data and habitat parameters, were merged to the 2002 dataset to determine which habitat variables serve as good predictors of presence and abundance.
Mean tadpole abundance in the Coast Mountains was 0.17± 0.03 individuals per minute, and tailed frogs occurred in 57% of sites. Mean tadpole abundance in the Hazelton Mountains was 1.7 times higher (0.28 ± 0.05 individuals per minute), with occurrence in 62% of searched sites.
Table 4. Sample sites, August 2002
Date Physiographic Region Hazelton Mountains Coastal Ranges August 5-6 Howson (n=9) August 7, 9-11 Hardscrabble/Shannon (n=19) August 8, 12 Trapline/Williams (n=15) August 13 Scotia (n=7) August 14 Hayward/Big Falls (n=10) August 15 Pitt Island (n=5) August 16 McNeil/Lachmach (n=7) August 16 Goat (n=2) Ishkinsheeksh (n=4) August 17 Ryan (n=5) Kitimat North (n=6) August 18 Simla (n=4) August 19 Kleanza (n=8) Shames (n=8) August 20 Unnamed (n=4) Kitimat South (n=3) August 21 Bowbes (n=6) August 22 Ascaphus Creek (n=3)
Northern Range of the Tailed Frog
Prior to this seasons work, the northern range limit had tentatively been drawn along Portland Canal and up the Nass River to Tseax River, then south along the Kitsumkalum Trough to the
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Maroon-Goat Creek divide (Dupuis and Bunnell 1997; Corkran and Thoms 1996). Eastwards, the range was assumed to be roughly coincident with the geologic contact between marine siltstone to the north and igneous and volcanics to the south; this boundary generally follows Fiddler Creek to Mount Knauss, crosses the Skeena River and follows Oliver Creek, encircling Mount Quinlan, and then trends south along Red Canyon Creek to the Copper River. Although incidental records were known for the west side of Copper River (Bustard, pers. com.) between Treasure Creek and Red Canyon Creek, occurrence on the east side of the Copper River was not known. The western range limit was thought to be governed by relief; tailed frogs would be absent on the low lying coastal plain, and the range limit would coincide with the trace of a specific contour elevation, say 400 m asl. A number of offshore islands with suitable topography could support tailed frogs, as the species has been recorded on Gribble, Princess Royal, and King Islands to the south.
Following this seasons work, the range was refined (Map 1). In the vicinity of Prince Rupert, the McNeil and Lachmach River drainages were extensively searched (n=7), yielding no occurrence. We had previously searched in the Port Edward-Phelan area (n=2) with no occurrence. Given the good habitat in these drainages, this was surprising, as positive records exist on a small creek nine kilometres east of Lachmach River mouth and across the Skeena in Scotia Creek. We concluded that there is no occurrence west of Work Channel. Hazelwood however, has provided a record for Kaien Island, Prince Rupert. On February 19, 2003, Friele searched two suitable creeks crossing Ridley Island Road, on Kaien Island, and one creek crossing Highway 16 between Lachmach and McNeil Rivers, and found no tadpoles despite extensive simplification of habitat. In light of our extensive search effort, we need to verify the Kaien Island record before accepting it. On the north and east side of the Kitimat Ranges, searches were conducted in Ishkeenickh River drainage, yielding no positive occurrence. We had previously searched extensively (n>25) in the area north of Kitsumkalum Lake including both sides of Nass River and Portland Canal yielding no positive records north of Mayo Creek. However, Hazelwood provided second hand records from the Nass Basin. Again, these records need to be verified before they can be accepted.
Thus, in the north we have drawn the Coastal range limit starting on the divide between the Lachmach and Khyex Rivers, then swinging NE along the Khutzemateen-Exchamsiks, Ishkeenickh-Extew, and Kitsumkalum-Nelson River divides to the south shore of Kitsumkalum Lake (Map 1). Within this area, tailed frogs have been confirmed in small drainages found along the northern shore of the Skeena River, but due to access constraints, no records exist for the Exchamsiks, or Exstew River drainages. Hazelwood has provided records from Khyex River. In addition, we have positive records for Kasiks, Shames, Zymagotitz, Erlandsen, Star, Nelson and Mayo River drainages.
Due to limited access, there is very sparse sampling on the mainland coast south of the Skeena River (Map 1). Five searches were conducted on suitable creeks on Pitt Island and tailed frogs were not recorded. Previous sampling (n=11) has been conducted in the vicinity of Kumealon Inlet camp, with no positive occurrence (Dupuis and Bunnell 1997). It appears as though the tailed frog has not made it west of the Ecstall River. Scotia, Big Falls, Hayward and Cuthbert River drainages have been sampled, with occurrence in Scotia and Big Falls, but not in Hayward or Cuthbert. Farther south there are records from Gribbell and Princess Royal Islands and the inlets to the east (Gardner Canal area), suggesting the western range runs south from Douglas Channel, down Grenville Channel, and then west to encompass Princess Royal Island.
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In the Hazelton region there are no records for areas north of Maroon and Fiddler Creeks (Map 1). We have positive occurrence from Carpenter Creek and Bowser Flats area and Hazelwood has provided records from Gosling Creek draining the east slope of Mt Knauss and a site on the east side of Skeena River near Dorreen. We have searched extensively further north along the Skeena River with no positive occurrence. Thus, our previous definition of the northern Hazelton range limit remains unchanged. However, it would be interesting to check whether an isolated population inhabits the Seven Sisters group, which would have been accessed via Oliver Creek. To the east and southeast, we have positive occurrence from the northern end of the Howson Range, just south of Red Canyon Creek on the east side of Copper River, and south along the west side of Copper River, continuing into the headwaters of the Clore River. Hazelwood provided four records from Miligit, Many Bear, and Limonite Creek drainages. Based on our sampling experience in the northern part of the Howson Range, the Miligit and Many Bear records must be from side drainages to the main creeks cited, and probably represent the easternmost range limit. The records from Limonite Creek may be from the mainstem, as this creek drains from a lake in Telkwa Pass. Bustard (pers. comm., 2003) sampled extensively in the Gosnell and Burnie drainages, south of Telkwa Pass, and reported no occurrence. Southeast, on Tahtsa Lake, Hazelwood reported a second hand record from Huckleberry Mine area on Tahtsa Reach. This record is located on the very eastern side of the Tahtsa Ranges on the edge of the Nechako Plateau (Holland 1976). Thus, the eastern range limit follows the west slope of the Howson Range, probably encompasses a portion of the Kitnayakwa River drainage, then follows the divide between Clore and Burnie Rivers to the Clore headwater then trends SE along the east side of the Tahtsa Range.
Landscape-level Associations
Coast Mountains
In the Coast Mountains, in the test using all basins tadpole occurrence was significantly influenced by PC CAO-1, which had high component loadings for biogeoclimatic zone and elevation (CAO-1, Logistic Regression: X2=10.93; sig.=0.0009; n=73). For the subset of small basins (<10 km2) PC CSO-1 also significantly affected occurrence (CSO-1, X2=7.82; sig.=0.005, n=64). Appendix B outlines statistical results in more detail.
Tadpole abundance in all basins was significantly correlated with PC CAA-1, which had high component loadings for biogeoclimatic zone, basin area, and ruggedness (CAA-1, Multiple Regression: F=3.37; p=0.08, n=31). This relationship was not quite significant when only small basins were considered (CSA-1, F=2.39; p=0.13, n=30), due to limited sample size following exclusion of zero data.
Geology had a high loading in both of these principle components, but since the Coast Ranges overlaps almost exclusively with the coastal plutonic complex, it has no obvious relationship to tadpoles in this region.
Tadpoles occurred significantly less at high elevations (Logistic Regression: X2=54.36; sig.=0.04) but this result may be due to a sampling bias; most Coast Mountains sites were at low to mid elevation because of limited accessibility.
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Tadpoles do well biogeoclimatic subzone variants with moderate moisture and temperature regimes: tadpole occurrence and abundance was lower in the very wet maritime subzone (CWHvm) of the Coast Mountains, than anywhere else (Table 5).
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Table 5. Tadpole distribution in relation to Biogeoclimatic zone
CWHws1 CWHws2 CWHvh2 CWHvm MHmm1 MHmm2 AT Coast Mountains No. samples 16 5 3 30 1 4 0 Positive sightings 6 4 0 10 1 3 0 No. tadpoles 66 24 0 64 1 50 0 Hazelton Mountains No. samples 25 38 0 0 0 23 1 Positive sightings 15 29 0 0 0 8 1 No. tadpoles 207 332 0 0 0 105 1 Both Regions No. samples 41 43 3 30 1 27 1 Positive sightings 21 33 0 10 1 11 1 No. tadpoles 273 356 0 64 1 155 1 % Occurrence 51 77 - 33 - 41 - Avg abundance 13 11 - 6 - 10 - (#/30 min.)
In the Coast Mountains, tadpole abundance was 0.18 ± 0.04 individuals per minute in small basins (≤ 10 km2) compared to 0.08 ± 0.04 in large ones. Small basins tend to be more rugged (Linear Regression: F=11.16; p=0.002; correlation matrix in Appendix B) and thus more suited to tailed frogs because of their coarser substrates. Within these smaller basins, occurrence and abundance peaks in moderate settings (Table 6; the six ruggedness categories were reduced to three more general ones due to small sample sizes).
Table 6. Tadpole occurrence and abundance in gentle to very steep watersheds <10km2
Watershed Ruggedness % Occurrence Mean tadpole/minute ± S.E. Gentle (6-30%) 57 (n=7) 0.15 ± 0.06 (n=4) Moderate (31- 70%) 65 (n=17) 0.36 ± 0.07 (n=11) Steep (71+%) 50 (n=12) 0.32 ± 0.08 (n=6)
Hazelton Mountains
In the Hazelton Mountains, for all basins and small basins tadpole occurrence was significantly affected by the second principle component, which has high component loadings for ruggedness, elevation and aspect (all basins: HAO-2, Logistic Regression: X2=7.87, sig.=0.005, n=65; small basins: HSO-2, X2=5.13, sig.=0.02, n=54).
For all basins, tadpole abundance was correlated with principle component HAA-2, which had high component loadings for ruggedness, elevation and geology (HAA-2, Multiple Regression: F=5.42; p=0.03, n=42). This relationship was not as strong when small basins were considered (HSA-2, F=2.59; p=0.12, n=36), again because of the smaller sample size due to the exclusion of zero data.
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Tadpole occurrence and abundance was greater in small basins than in large ones; occurrence was 65% versus 43% and, with zero data excluded, abundance was 0.5 ± 0.07 individuals per minute (n=47) versus 0.15 ± 0.07 (n=6). In the small basins, tadpole occurrence and abundance appear to be lowest in the gentle drainages (Table 7), with a slight peak noted in the moderate class.
Table 7. Tadpole occurrence and abundance in gentle to very steep watersheds <10km2
Watershed Ruggedness % Occurrence Mean tadpole/minute ± S.E. Gentle (6-30%) 47 (n=19) 0.16 ± 0.05 (n=9) Moderate (31- 70%) 70 (n=37) 0.52 ± 0.11 (n=26) Steep (71+%) 67 (n=15) 0.47 ± 0.10 (n=10)
Tadpole abundance was not directly correlated to rock type (e.g., mean abundance in creeks containing coarse rocks was 0.21 ± 0.04 (n=68) compared to 0.21 ± 0.06 (n=32) in creeks flowing on volcanics, 0.36 ± 0.09 (n=12) on sedimentary rocks, or 0.38 ± 0.07 (n=16) on mixed rock types). When tadpole occurrence in various rock types was examined by ruggedness class, no clear patterns were evident (Logistic Regression: X2=4.0; sig.=0.26); therefore the inclusion of geology appears to have no bearing on abundance in the Hazelton Mountains. However, this may be an artifact of small sample sizes, and/or of survey bias; the sites in the best rock types (plutonic) were primarily in the Hardscrabble watershed where runoff regime and ruggedness were high. By contrast, all sites in the least favourable rock types (sedimentary) were in less dynamic streams with low water transport potential, where the effects of poor rock type were less likely to be felt.
A logistic regression testing frequency of occurrence to elevation and aspect combined, yielded significant results for both variables (X2=91.73; sig.=0.02 and X2=2.73; sig.=0.096, respectively) because north-facing creeks are cold at high elevation, but warm to tolerable levels downstream. Cold creeks yield fewer tadpoles. There is no direct significant relationship between elevation and abundance (ANOVA: F=1.7; p=0.44), but a negative relationship was noted in the field for many creeks. Sample size and spatial variability may confound this analysis.
Site-level Associations
At the habitat level, tadpole occurrence was significantly influenced by principle component FO- 2, which has high component loadings for water temperature, reach slope, bankfull discharge and embeddedness (FO-2, Logistic Regression: X2=10.87; sig.=0.001, n=57). This grouping essentially represents the complex interaction of substrate and hydrology in determining physical habitat. Only embeddedness has a strong direct influence on occurrence; the other variables interact producing a low disturbance state (good for frogs) or a high disturbance state (bad for frogs), as illustrated by Table 8. Discharge is directly related to basin area – tailed frog occurrence is low in large basins, and by corollary at sites with high discharge.
Tadpole abundance was correlated with PC FA-1, which has high loadings for logging history and its correlate riparian cover, embeddedness, and disturbance index (FA-1, Multiple Regression: F=6.83; p=0.01, n=57).
Tadpole occurrence and mean abundance were much higher at sites with nil to low embeddedness than at sites with moderate to highly embedded substrates (Table 8). Channel disturbance had a notable influence on tadpole occurrence and abundance. Tadpoles occurred most frequently in
Landscape-level Requirements for Tailed Frogs in the Skeena Region 17 Ascaphus Consulting 22/11/12 moderately disturbed sites, and least frequently in highly disturbed ones (Table 8). Within tadpole-bearing creeks, abundance was very low in creeks prone to snow avalanches and high calibre sediment floods, and highest in creeks subject to low calibre sediment floods (moderate disturbance; Table 8). Older cohorts (2+ years) were found primarily in moderately disturbed channels (47% of all sites with tadpoles) and low energy systems (31% of all tadpole-bearing sites), indicating very dynamic systems are less favourable.
Table 8. Summary of habitat-level tailed frog tadpole associations
Bedload Movement and Disturbance % Tadpole Abundance Indicators Occurrence (tadpoles/minute ± SE) Logging History 71 (n=71) 0.38 ± 0.05 (n=47) Undisturbed stands 29 (n=29) 0.24 ± 0.05 (n=17) Logged stands Embeddedness 75 (n=40) 0.44 ± 0.17 (n=30) None and low 47 (n=60) 0.25 ± 0.03 (n=34) Moderate and high
Channel Disturbance Intensity 30 (n=30) 0.19 ± 0.11 (n=9) High energy/recent debris flow 91 (n=34) 0.44 ± 0.06 (n=31) Moderate disturbance 67 (n=36) 0.27 ± 0.03 (n=24) Low calibre sediment floods
The influence of water temperature on occurrence is best explained by the observation that tadpoles were not found in creeks colder than 6°C.
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Analytical Summary
A summary of the interrelated watershed and stream level parameters (see Figure 4) that affect tadpoles in their lotic environment is provided in Table 9.
Table 9. Summary of factors affecting larval tailed frogs (all basins)
Significant Landscape Regression Comments Parameters Statistics Coast Ranges Occurrence: BGC zone, X2=10.93 Tadpole occurrence and abundance was lower in CWHvm, most likely due to the high waterpower and flashy elevation, geology Sig.=0.0009 discharge of windward creeks. Bedrock is generally competent throughout. High elevation sites were under- represented in this study due to their limited accessibility. Small basins (0.3 to 10km2) have characteristics Abundance: BGC zone, F=3.37 providing best tailed frog habitat: they are generally more rugged (moderate to very steep), which results in greater basin area, ruggedness P=0.08 waterpower and coarser substrates. When ruggedness was simplified as gentle (class 2), moderate (class 3, 4) and steep (class 5, 6) to increase sample size, tadpoles appeared to occur less frequently in the gentle and steep drainages; abundance in tadpole-bearing creeks was highest in moderate to steep ones. Hazelton Ranges Occurrence: Ruggedness X2=5.13 Abundance and occurrence were greatest in small basins. Although sample size was too small to show the aspect, elevation Sig.=0.005 significance of this relationship, it is known that smaller basins provide better tailed frog habitat. Within small basins, tadpole occurrence and abundance were lowest in gentle drainages. Aspect and elevation together Abundance: Ruggedness F=5.42 influenced tadpole occurrence: north-facing sub-basins at high elevation (>900 m) were too cold for tailed frogs to elevation and geology; P=0.03 be reproductively successful in. Elevation and geology did not affect tadpole numbers; their high loadings in the principle component analysis for abundance likely reflect sampling biases.
Significant Habitat Regression Comments Variables Statistics Coast and Hazelton Mtns Occurrence: Water F=9.19 Occurrence and abundance were higher in moderately disturbed sites, and lowest in creeks subject to high calibre temp, discharge, slope, P=0.003 sediment floods and snow avalanches. This reflects the landscape level result indicating reduced occurrence and embeddedness abundance for the steepest basins. Tadpole abundance was low in highly embedded substrates; embeddedness is F=6.83 often higher in logged over channels. Water temperatures less than 6oC do not support tadpoles. Discharge was Abundance: Logging P=0.01 inversely related to occurrence; this mirrors the landscape level result with basin area - basin area is directly history, embeddedness, correlated with discharge and is often used as a surrogate – indicating tailed frogs prefer smaller basins. channel disturbance
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Discussion
Definition of a Population (based on case studies)
To understand more about watershed level distribution and what constitutes an element occurrence at the northern range of A. truei, large watersheds were sampled from their confluences with major rivers upstream to their headwaters. Description of these drainages and summaries of tailed frog searches are as follows:
Hardscrabble Creek is a glaciated, east flowing tributary to the Skeena River. The majority of the watershed is underlain by granodiorite with inclusions of coarse sedimentary rock in the mid valley, and a small area of fine sedimentary rock near the mouth. The watershed is about 53 km2, with divides between 1500-1600 m and small peaks to 1700 m, and the mainstem channel gradient varies from 3-8%. Tributaries are moderately steep to very steep (50-120%), confined within deep rock gullies, and with channel gradients of 17-52%. Streams in the headwater and at higher elevations are cold (4-6oC), while mid slope streams are cool (6-8oC) and those at low elevation and along the mainstem reach 8-11oC. In the headwaters, the mainstem channel is subject to snow avalanches, high-energy, bouldery sediment floods and periodic debris flows. There is evidence of a recent large sediment flood (bouldery terraces 1-2 m tall) extending all the way along the mainstem channel to the mouth, a distance of 12 km from the headwaters. Tributaries are subject to snow avalanches, sediment floods and infrequent debris flows. One tributary creek had been recently affected by debris flow activity. A total of 17 surveys were conducted within the Hardscrabble Creek watershed. Tadpole numbers were low along the mainstem (1-3 indiv./30 min.), and none were found in a sample near the mouth at Skeena River. Along tributaries, tadpole numbers were often high but variable on lower slope positions, and low at mid slope sites. The highest numbers (10-40 individuals/30 min search) occurred at sites with warmer temperature (9-10 oC) and lower disturbance intensities. Tailed frogs were not common in the cold creeks at the backend of the drainage, which drains from neve and glacier ice and is subject to snow avalanche activity. Nor were tadpoles found in the cold higher elevation reaches of tributaries closer to the valley mouth.
Trapline Creek is a non-glaciated, east flowing tributary to Clore River. It is underlain by weak volcanic bedrock. The watershed area is about 40 km2, with divides at about 1400-1500 m. Peaks at the head of Moraine Creek, the largest tributary, reach about 1600 m. The mainstem gradient is about 3%. Tributaries are moderately steep (ruggedness of 50-70%), with channel gradients of 10-35%. Although stream temperature in the headwaters above 600-700 m elevation, near the pass with Williams Creek, are cold (<6oC), stream temperatures elsewhere range from 8-10oC. The channel mainstem is susceptible to flooding and normal fluvial processes such as lateral channel migration. Tributaries are subject to normal flooding, moderate bedload movement and infrequent debris flows, with the exception of Moraine Creek. This tributary has a very steep headwater and is deeply gullied, and the fan at its mouth is disturbed by recent debris flow activity. Larger tributaries are deeply gullied, but smaller creeks are not. Based on 15 searches in the Trapline Creek watershed, tailed frogs were not located in the cold headwaters of the mainstem, or along the disturbed lower reach of Moraine Creek. Elsewhere, tadpole numbers ranged from 1-36/30 minute search, with the highest numbers and widest distribution of cohorts along the low to mid slopes of tributary creeks. One of the best sites was near the mainstem mouth, just upstream from the confluence with Clore River. At this location, the river is confined in a canyon and local hydraulics produce good substrate conditions.
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As indicated by these case studies and additional observations during 2002 surveys, A. truei occurs and breeds along sub-basin mainstem channels draining watersheds of up to about 50 km2 in area. Suitable mainstem channels have gradients of 3-10% and are known to support fish; abundances are generally low, but areas with suitable substrate may support tailed frogs in good numbers. Mainstems represent important breeding habitat, migration corridors, and source areas for steeper tributaries that are periodically affected by extreme events that cause high mortality along their length. Tributaries, ranging from about 0.03 to 10 km2 in area, typically with moderately steep to very steep basins, support breeding throughout, provided summer water temperatures remain above 6oC. No tadpoles were located where water temperatures were less than 6oC.
Areas with higher intensity disturbance regimes support fewer tadpoles, often with younger cohorts represented, suggesting regular mortality. Mid to low elevation (<900 m asl) reaches are generally the most productive along tributary streams, with highest numbers and widest distribution of cohorts on streams with warmer temperatures and lower disturbance intensity. Thus, a population (occurrence) can be considered to be those animals occupying a drainage basin of up to 50 km2 area (e.g., Hardscrabble, Shannon, Trapline). Occurrences within tributaries (i.e. Joe Bell) that drain into larger mainstems (i.e., Skeena River) may be grouped with those in adjacent tributaries (i.e., Apprentice) if overland distances are not excessive. In the absence of knowledge of the basin-wide distribution, a tailed frog occurrence must be separated from other occurrences by a physical barrier (e.g., icefield), two kilometers of suitable habitat, or one kilometer of unsuitable habitat (Gaines 2002; NatureServe 2002) to be considered a distinct population.
Landscape and Habitat Level Attributes of Significance to Tailed Frogs
Landscape- and habitat-level attributes important in governing tailed frog distribution and abundance are discussed together because habitat level variables are dependent on basin and channel controls in the hierarchy of the fluvial system (Figure 4). In many cases some landscape level variables (i.e., basin area) serve as proxies for those at the habitat level (i.e., discharge).
Basin Area
Tailed frogs were far more common in small basins (0.3 to 10 km2) than large ones (10-50 km2), and except for a few drifters are absent from rivers draining areas in excess of 50 km2 (Figure 5). These small basins represent typical moderate to very steep tributaries that feed sub-basin mainstems. It would seem that both physical and biotic factors might determine this selection. From the physical point of view, basin area is inversely correlated with both ruggedness and reach gradient. Rivers draining large basins have gradients of 1% or less; those draining smaller basins have gradients of 1 to 5%; basins smaller than 10 km2 usually have gradients steeper than 5%. Channel structure and substrate changes with gradient: for example, pool, riffle, rapid, cascade, and step channel units have average slopes of 0.5%, 1%, 3%, 5.5% and 17% respectively (Grant et al. 1990). Pool-riffle habitats consist of sandy gravels, while steeper habitats are coarser (Figure 4). It is known that tailed frogs select for coarser substrates (Altig and Brody 1972). Although the lower end of the tailed frog distribution overlaps with fish, selection for steeper tributaries may also be a predator avoidance strategy. Tailed frog occurrence is highest between reach gradients of 3 to 40%, while the upper limit for fish is assumed to be about 20% gradient.
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Figure 5. Tadpole abundance plotted against basin area shows greatest abundance in streams draining basins of 0.3-10 km2 in area.
Climate
Tadpoles were scarce in the wettest biogeoclimatic zone (CWHvm) of the Coast Ranges because intense and prolonged precipitation produces very high storm runoff. In combination with rugged topography, this runoff yields high discharges, stream power and flashiness (as discussed below). The resulting in-stream conditions are conducive to high tailed frog mortality.
Larvae were noted to be absent from creeks cooler than about 6°C. A plot of temperature versus precipitation partitioned by sources (Fig. 6) indicates that snow and ice melt creeks are cooler, and cool more rapidly with elevation, than groundwater source creeks. In late summer, glacier-
Figure 6. Stream temperature partitioned by headwater source.
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-fed creeks are 3 to 6°C near their sources, warming to about 10°C at lower slope positions. In contrast, creeks sustained through the late summer period by groundwater base flows are generally 7 to 8°C near their spring sources, warming to 11-13°C downstream.
The warmest stream temperatures (13-15°C) were noted at Scotia Creek, in a rain fed tributary near the coast. Lake-fed creeks (i.e. Simla) may also have warm outflows, but may cool downstream with the addition of groundwater sources. Since tailed frogs were not found in creeks with late summer temperatures less than 6°C, the relationship in Figure 6 suggests that tadpoles are not likely to be found along glacier-fed creeks above 800-1000 m in elevation. Given the usual northern orientation of glaciers, this also links into the control shown by the interaction between aspect and elevation in the Hazelton Mountains (Appendix B). It follows that at mid to high elevations in the continental climate prevalent in the Hazelton Mountains, tailed frogs are more reproductively successful in the warmer, south-facing creeks (Figure 7).
N
Abundance (tads/30 min) 1 2 3 4 5 6 7 8 9 10 11 12 13
Figure 7. Mean number of tadpoles per 30 minute search, in relation to aspect in the Hazelton Mountains
Hydro-geomorphology
Bankfull discharge estimates were plotted against the catchment area above the sample site (Fig. 8), producing an area-discharge plot for basins between 0.1 to 100 km2 in size. When the data is partitioned by physiographic region the trend lines indicate that, for a given basin area, Coastal creeks yield 2.5-3 times more runoff than Hazelton creeks. This is an increase over larger basins, where, for drainages ranging from 350 to 750 km2 in size (Table 2), Coastal creeks yield twice as much runoff than Hazelton creeks.
Landscape-level Requirements for Tailed Frogs in the Skeena Region 23 Ascaphus Consulting 22/11/12
Figure 8. Area-discharge relationship indicates progressive increase in discharge toward the west.
The negative correlation between unit area discharge and basin area holds for small, ungauged basins (Table 10), as demonstrated by data taken from the trend lines in Figure 8 and Table 2.
Table 10: Decrease in unit area discharge (Q2) with increase in basin area
Physiographic Basin area (km2) Region 0.2! 10! 100! 200* Coast 4.8 1.8 1.2 1 Hazelton 1.8 0.7 0.43 0.27 ! from Figure 8; * adjusted from Table 2
A histogram of the flashiness index (Fig. 9) indicates that more Coastal creeks are flashy.
Figure 9: Peak to low flow ratios; more Coastal creeks are flashy, more Hazelton creeks are stable.
Landscape-level Requirements for Tailed Frogs in the Skeena Region 24 Ascaphus Consulting 22/11/12
In summary, field measurements and stream gauging data demonstrate that coastal streams produce greater discharge and are more flashy than similar sized streams further inland, and that this effect is most pronounced in basins typically occupied by tailed frogs. Although flashiness did not significantly correlate with tailed frog occurrence or abundance, it is intuitive that these relationships influence tailed frog distribution within the wettest subzone (CWHvm) of the Coast. However, more data may be required to bear this out statistically. Tadpole density was greater in low to moderately disturbed sites than in high energy ones (Table 8). These effects on occurrence and abundance are linked to the incidence of bedload transport and the increased risk of tadpole trauma (mortality).
Ruggedness and basin area did have a significant influence on tadpole numbers. Since sites draining large basins (>10 km2) have low ruggedness values, simply by virtue of their size, and due to their finer substrates and the presence of fish, they support fewer tailed frogs (Figure 5). Thus, it is more appropriate to examine the relationship of tailed frogs to ruggedness in sites within tributary basins (subbasins less than 10 km2). Within smaller basins tadpole abundance is lowest in gentle drainages (Tables 6 & 7). The higher abundance in steeper drainages is due to the presence of coarser substrates in these creeks. Figure 10 shows the ruggedness values for sampled Coast and Hazelton Mountains. The data suggest that Coastal basins are more rugged than Hazelton basins; however, this is not a true representation, as there is some sampling bias to moderate and moderately steep basins in the Hazelton group. More data in steep and very steep basins, especially in the Hazelton Mountains, would probably demonstrate an even stronger relationship between abundance and ruggedness.
Figure 10: Basin ruggedness for sampled sites in the Coast and Hazelton Mountains
Our prediction was that increasing ruggedness would be detrimental to tailed frog tadpoles, due to the increasing instability of channel substrate with increasing steepness. Tadpole occurrence was greatest in moderately steep basins. Although tailed frogs may seek small rugged basins to avoid predation and/or to find the best substrates, mortality factors reduce their total fitness in the steep and very steep basins.
Landscape-level Requirements for Tailed Frogs in the Skeena Region 25 Ascaphus Consulting 22/11/12
Geology had a high loading in the significant principle components of the Coast and Hazelton Mountains, always in relation to ruggedness. Where rock type was poor, waterpower was correspondingly low, offsetting the negative effects of high sediment loading. We note that few steep basins were sampled in the Hazelton Mountains (Figure 10) where poor rock types are found. It would be useful to sample more steep basins in this area to further examine the interaction between geology and ruggedness on tadpole occurrence and abundance.
Logging History
Sedimentation, measured as substrate embeddedness, is the primary factor governing tadpole numbers at a habitat level. Sedimentation impacts on larval tailed frogs have been well documented (Dupuis et al. 2000; Wilkins and Peterson 2000; Diller and Wallace 1999; Welsh and Ollivier 1998; Dupuis and Friele 1996; Bury and Corn 1988). In this data set logging history and its correlate riparian canopy cover did not significantly influence tadpole occurrence or abundance. The effects have been well documented by other studies however (i.e., Dupuis and Steventon 1999). The interesting result in this study was the significant effect of geology on abundance, but only in logged creeks. This is due to the high post-logging sediment production in areas of weak rock type, an effect originally proposed by Dupuis and Steventon (1999).
Range Expansion
The entire Cordillera, except for the higher peaks, was ice-covered during the last glaciation (Clague 1985) and there were no glacial refugia suitable for tailed frogs north or west of the Cordilleran ice sheet (see discussion in Ritland et al. 2001). Thus, colonization of the Coast Mountains would have progressed steadily northwards after the onset of deglaciation, 13,000 years ago (see Friele and Clague 2002) and, similar to other species, northward migration that began with deglaciation, may still be occurring.
Habitat appears suitable in drainages such as McNeil, Lachmach, Kitsumkalum, and Ishkeenickh, yet tailed frogs are not found there. Since habitat quality is good in many creeks within these sub- basins, it appears the animals have not yet colonized them. The pattern of the northern range limit may be partly shaped by geographic barriers. Based on the tailed frogs life history, and supported by demographic patterns observed in southeastern BC (Dupuis and Friele 2002) and observations made by Wahbe and Bunnell (2001), it is suspected that adult tailed frogs disperse upstream, or against the current, while tadpoles disperse by downstream drift. Entering a watershed from its mouth, adults may colonize all tributaries and eventually reach drainage divides. Adult seasonal migrations (probably both upstream and downstream in response to discharge and temperature changes; Adams and Frissell 2002) and tadpole drift would serve to colonize new drainages accessed via headwaters. With this model in mind, we note that the lower reaches of Kitsumkalum River upstream of Kitsumkalum Lake, and the lower reaches of Exstew, Exchamsiks, Kasiks, Khyex, Lachmach, and McNeil Rivers are sluggish, meandering rivers flowing in wetland habitat. These habitat types may present a barrier to upstream (hence northward) dispersal. The second form of dispersal barrier in this area is the very rugged, and extensively glaciated headwaters. Thus, only a few low passes, such as between Nelson and Mayo Creeks in the east and Khyex and Toon Rivers in the west may be suitable for headwater dispersal. Finally, bedrock along Kitsumkalum Trough, north of Kitsumkalum Lake, consists of a weak, fine sedimentary type, and colonization of these streams may be restricted by disturbance regime. Certainly, overland (versus riparian) dispersal between tributaries does occur and passes
Landscape-level Requirements for Tailed Frogs in the Skeena Region 26 Ascaphus Consulting 22/11/12 are crossed. In this light, we regard the present northern range limit within the Kitimat Ranges as a migration front, with northward colonization still occurring. Similarly, the lower Ecstall River may be a barrier as tailed frogs do not appear to have made it west of the Ecstall into the Kumealon River area.
Population Trends
Clearcut logging and road construction can alter hydrological regimes of watersheds, accentuating peak discharges and decreasing summer base flows (Jones and Grant 1996). Clearcutting, road construction and road use also result in increased sedimentation (Reid and Dunne 1984; Beschta 1978). A decline in tadpole abundance following timber harvesting has been well documented and has been attributed largely to post-logging sedimentation of creek channels (Gaige 1920; Noble and Putnam 1931; Metter 1964; Bury 1983; Bury and Corn 1988; Corn and Bury 1989; Aubry and Hall 1991; Gilbert and Allwine 1991; Welsh and Lind 1991; Kelsey 1995; Dupuis and Friele, 1996; Bull and Carter 1996; Dupuis and Steventon 1999; Maxcy 2000; Welsh and Ollivier 1998; Welsh and Lind 2002). This finding is supported by our results which showed a strong relationship between tadpole abundance and logging history, substrate embeddedness, and channel disturbance. The relationship is probably strongest in steep creeks with incompetent rock and high discharge rates. This effect occurs at least in the short (1-20 year) to medium (20-80 year) term, until sediment additions have had a chance to flush through the system, allowing streams and riparian areas to stabilize.
Adult densities are also known to be highest in areas of older forest (Welsh and Lind 2002; Stoddard 2002; Richardson and Neill 1998; Welsh 1990), where dessication stresses are lowest (Chen 1992: Johnston and Frid 2002) and structural diversity is highest (Franklin 1988), providing better foraging opportunities. In the Skeena Region there are very few valleys that are not developed. With extensive first pass valley-bottom and some second pass mid-slope logging, and based on the discussion above, it would follow that tailed frog populations are reduced significantly below natural levels. Especially since the logged portions of the valleys were the most productive tailed frog habitat.
A Conservation Strategy
Existing Tailed Frog Wildlife Habitat Area Model
Under the Forest Practices Code, Wildlife Habitat Areas (WHA), as defined by the Identified Wildlife Management Strategy (BC Ministry of Environment and BC Ministry of Forests 1999), may be proposed for identified wildlife, such as the tailed frog. In general, a WHA is defined and within it features may be delineated where special habitat protection is required. Under the existing provincial guidelines the tailed frog WHA design is as follows: Key natal tailed frog habitat is described as consisting of perennial headwater creeks with stable channel beds, coarse substrates, adjacent forest cover, and lack of fish. Objectives of the tailed frog WHA are to maintain water quality and natural flow regime, and to maintain structural elements of mature forest adjacent to tailed frog streams. The existing design of a WHA consists of a reserve 500 m long along length of stream with 50 m buffers. Within the buffer there is a 20 m no-log zone, and a 30 m management zone with restricted timber harvest. Priority is to be given to creeks with
Landscape-level Requirements for Tailed Frogs in the Skeena Region 27 Ascaphus Consulting 22/11/12 high tadpole abundances, several neighbouring tributaries, old growth buffers, and riparian connectivity.
It is arguable that the objectives stated above may not be met given the design protocol. The first priority, to maintain water quality (more precisely substrate quality) and natural flow regime, requires management at the watershed level whether this be a 1 km2 or 50 km2 area. Infrastructure that affects flow regime and sediment quality to the greatest extent are roads, and to a lesser extent harvested area (Jones and Grant 1996; Grant, 2001). Thus, design of a WHA as a 500 m long strip within a watershed provides no legislative power to the responsible agency to manage for the stated objectives. For example, if a WHA were defined along the lower slopes of a tributary channel and normal forestry operations were carried out within the rest of the watershed, it is quite possible that the channel upstream of the WHA would have multiple road crossings and no, or ineffective, buffers (see example from Hardscrabble Creek, sites HS-12 & HS-13, discussed in Selection Criteria section, below). In this scenario, sediment from ditch-lines and gully sidewall failures could introduce excessive sediment into the channel; this material would work its way downstream and negatively impact the WHA.
Further critique is warranted: the habitat section makes reference to key natal streams consisting of perennial headwaters. Headwater streams, a vague term, may be taken to imply first order streams, which are often less productive. It is our experience that key natal streams consist of second and third order streams (Dupuis and Friele 2002; Welsh and Lind 2002), and that breeding occurs along mainstems in streams draining areas up to 50 km2. To be precise, in this project the most productive sites were found to have catchments of 0.3 to 10 km2 in area. Lack of fish is also noted as a condition: much of the lower reaches of all tailed frog bearing systems coincide with fish habitat - fish and tailed frogs are not mutually exclusive.
Recommended Tailed Frog WHA model
WHA Design Concepts
In our view, a WHA boundary should follow the catchment boundary above a defined point on a stream. The intent of this is to provide the responsible agency with control over the activities that occur within the WHA, and that have potential impacts on the stream. It must be stressed that logging may still be allowed within the boundary of the WHA, under strict operational guidelines. The total catchment area of a designated stream will not be more than 10 km2, with 1-5 km2 being most probable (see Table 9).
Referring to general WHA design principles, WHA management strategy employs measures and features. Measures are applied within the WHA and consist of best management practices, as outlined below; the feature is the designated channel with appropriate buffers. Buffers should be designed to reflect terrain conditions (i.e. set at gully slope breaks etc.) and not necessarily set arbitrarily at 50 m. Designated buffers should extend the full length of the channel from the stream confluence to the upper limit of the operable forest, and not be limited to 500 m in length.
Wildlife habitat features
Wildlife habitat features are defined as all perennial stream channels within the WHA. Maintaining or recovering the integrity of the feature can be achieved by establishing riparian buffers. Buffer edges should extend 50 metres from the water’s edge, or to the gully sidewall
Landscape-level Requirements for Tailed Frogs in the Skeena Region 28 Ascaphus Consulting 22/11/12 crest, whichever is greater. Clearcutting and salvage operations should be prohibited within the buffer. Feathering or topping should be employed if necessary to ensure that buffer edges are windfirm (see Stathers et al., 1994). The number of road crossings should be minimized and ditch runs designed to minimize direct sediment contribution to the channel. All instream works should employ sediment control measures, and timing windows should be geared to reduce sedimentation inputs. Thus, rainfall shutdown guidelines should be employed and instream works in fall and winter should be avoided.
Wildlife habitat measures, or best management practices
The general wildlife measures are geared to provide clean and stable gravel substrates, natural step-pool channel morphology, and maintain or restore modulated peak flows, riparian vegetation, stream temperatures within tolerance limits, and adult foraging areas. Specific measures include:
minimizing road densities and stream crossings; undulating road grades to disperse road surface water; keeping roads away from steep slopes (scarps) with direct connectivity to streams; maintaining naturally dispersed water flows (seepages, non-classified drainages and streams should be supplied with cross-drainage structures where intersected by roads); reducing the length of ditch runs, and not spoiling ditchwater directly into defined channels; constructing narrow roads to minimize site disturbance and reduce groundwater interception in the cut slope; using sediment-control measures on cut- and-fill slopes and ditch lines (e.g., grass- seeding, armouring ditch lines and culvert outfalls); de-activating roads as per the Forest Practices Code; prohibiting logging within gullies and slope stability class V polygons; minimizing site disturbance during harvesting, especially in stability class IV terrain and in polygons with high sediment transfer potential to streams; developing a higher level management plan that considers issues around “hydrological green-up” and runoff response; and minimizing the use of chemical applications (e.g., dust-palliative polymer stabilizers and soil binders that can be sprayed within ditch lines) and herbicides because of their potential toxicity to amphibians.
For details on road construction and maintenance, refer to the Forest Road Engineering Guidebook (BC Ministry of Forests and Ministry of Environment 1995a). Information can also be obtained from the Soil Conservation Guidebook (BC Ministry of Forests and Ministry of Environment 2001), the Community Watershed Guidebook (BC Ministry of Forests and Ministry of Environment 1996) and the Site Preparation Guidebook (BC Ministry of Forests and Ministry of Environment 1995b).
In extensively developed areas, management initiatives within the WHA should focus on watershed restoration and recovery. This may include: (1) channel and gully assessments; (2) in- stream works to restore step-pool morphology and reduce sediment transport; (3) streamside planting to stabilize banks, road deactivation to reduce sediment inputs; and (4) the planning of
Landscape-level Requirements for Tailed Frogs in the Skeena Region 29 Ascaphus Consulting 22/11/12 forest ecosystem networks (FENs) and old growth management areas (OGMAs)(see BC Ministry of Forests and Ministry of Environment 1995c).
Site Selection Criteria and Considerations
For each biophysical variable found to influence tailed frog abundance and distribution, we have been able to define a range of values that optimize fitness. The optimal categories or ranges of these landscape and habitat-level parameters are listed in Table 11. More data in steeper basins is needed to investigate the relationship between ruggedness, geology and tailed frog abundance at the landscape level, and reach slope, rock type, discharge and flashiness and the site level.
Table 11. Optimal biophysical conditions for tailed frog tadpoles
Landscape Parameter Ideal Range Biogeoclimatic Zone Subvariants* CWHws2, CWHws1, MHmm2 Basin Area (km2)* 0.3 - 10 Watershed Steepness (%)* 31-70 Elevation (m)* <900 Logging history* Old growth on one or both sides of creek Aspect South, East, West Reach slope (%) 3-40 Disturbance Regime Low to moderate energy systems Substrate Embeddedness None; or low to moderate (<50% embedded) Bankfull width 1-6.5 Water temp (°C) 8.0-15 Riparian canopy cover (%) 55 – 70 (averaged across banks) * map-derived variables
Productive tailed frog streams drain moderate to very steep basins (ruggedness >30%). Since these basins may be prone to periodic high intensity disturbance events (debris flows, sediment floods; Figure 8), the designation of a single channel as a WHA could leave the protected population threatened by extreme events. If a single channel is designated it should have moderate to moderately steep basin ruggedness (30-70%), with an irregular long profile, so that extreme events are not likely to carry along the full length of the channel. Optimally, two adjacent channels would be included in the WHA, since it is less likely that extreme events would affect both channels at the same time. These channels would be separate forks of a single tributary, or connected by a mainstem channel supporting breeding tailed frogs. Recolonization of the affected channel could then occur overland through the terrestrial matrix or along the connected riparian network. These concepts are outlined by the example provided in Figure 11.
Landscape-level Requirements for Tailed Frogs in the Skeena Region 30 Ascaphus Consulting 22/11/12
Figure 11. Copper River tributary. Natural rockslide and debris flow in Spring 2002 travelled 3 km along length of channel, causing extirpation along 40% of available habitat within basin. Basin is moderately steep with straight channel profile. Tributary creeks will provide colonizers.
Since watershed headwaters are higher in elevation and relief, tributary streams draining valley- head areas are often colder, and subject to more intense disturbance events (DeScally et al., 2001). Thus, tributaries closer to valley-mouths or draining the face units between watersheds may be better suited to WHA designation. South facing tributaries are preferred.
Tadpole abundance is usually used as a guide to the selection of good sites. However, this measure should be used with caution as sites with high abundance may be sinks (Pulliam 1988; VanHorne 1983). For example, site UN-4 along the west side of Copper River had high abundance. This site was located at the apex of the alluvial fan, but just downstream from the site the stream went underground in fan gravels. Thus, the high concentration of individuals resulted from contraction of habitat as flows declined, combined with tadpole drift from upstream. Further contraction of the stream would have resulted in high mortality at the site. We have encountered this situation at other sites as well. One notable example was along the lower reaches of Bonser Creek (GIS case 399; Dupuis and Bunnel 1997), where we recorded the highest density of tadpoles in 54 area constrained searches executed in 1994. Again this was a site where the stream went subsurface just downstream of the search.
With this caveat in mind, WHAs are best selected when one has knowledge of the vertical distribution of abundance along a creek. The best candidates will have high to moderate abundance in the elevation range below about 900 m elevation. Sites with reduced abundance at mid elevation and up are considered fair to poor candidates. For example, in Hardscrabble Creek, high abundances were recorded at low elevation on two south facing creeks (sites HS-8 & HS-
Landscape-level Requirements for Tailed Frogs in the Skeena Region 31 Ascaphus Consulting 22/11/12
13), however, no occurrence was recorded at the two sites above HS-8 (HS-9 and HS-10). Similarly, the mid slope site above HS-13 (HS-12) had low abundance, while no tadpoles were recorded at the upper slope site (HS-11). Factors causing these elevational trends were probably cold water temperatures and high sediment loads. WHAs on these creeks will have productive channels only below about 600 m elevation.
Although the lower reaches of a system may be the most productive, in most cases it is still necessary to have control over the activities that occur upslope in the watershed. For example, a helicopter block was recently harvested between the two Hardscrabble tributaries mentioned above. The block consisted of a 400 m long clearcut on straight to shallowly gullied, 70% slopes. Since both creeks are deeply cut in steep-sided bedrock gullies, wide buffers were left due to inaccessibility of the timber. In the spring of 2002 a large snow avalanche released within the block boundaries and blasted through the buffer, causing extensive damage and uprooting numerous trees. The debris directly entered the channel just downslope of site HS-12 causing damage to the far bank. A deposit of snow and coarse woody debris about 10 m deep, 15 m wide and 50 m long remained in the channel as late as September, 2002 (Friele 2002). The clearcut is situated on stability class IV terrain, in a polygon with direct channel connectivity. Therefore, the debris slide hazard is moderate to high, with a high potential for sediment delivery to the channel. Any debris introduced to the channel may result in deleterious impacts to tailed frog habitat downstream.
The Ascaphus Reserve meets all the optimal criteria noted above: the watershed drains an area of about 3 km2; it is located on a southeasterly facing slope between Sand and Carpenter Creeks. Summer flows are largely maintained by groundwater sources and stream temperatures are warm (9-12°C). The watershed is moderately steep (50-70%), encompassing a dendritic network of tributary streams, with irregular long profiles and typical channel gradients of 10-15%. These characteristics offset the fact that the bedrock quality is poor (fine grained sedimentary), resulting in a low disturbance intensity. Sampling in 2002 showed that low to mid slope position sites supported high tadpole abundance (17–23 tadpoles/30 min) with wide representation of cohort classes. Upper slopes support lower numbers, but breeding was confirmed; this was the only site where a tailed frog egg nest was located in 2002. Adults have been found up to 1500 m elevation along Joe Bell and Apprentice Creeks (Hazelwood 1994). Thus, the Ascaphus reserve is a good model for future WHAs.
By way of example, the criteria discussed above are applied to selection and design of potential WHAs in Trapline Creek (Figure 12). The ground between the TR-1 and TR-10 basins is unlogged and is not crossed by a road. The area is south facing, with moderate to high abundance below 900 m asl. The basins are extensively gullied, have moderate to moderately steep ruggedness, and convex channel profiles. Weak volcanic bedrock, leading to bank instability and sediment loading, is mitigated by streams with low water power, although infrequent debris flows do occur. Conventional logging in this area would undoubtedly result in aggravated gully wall instability, with a high potential for post-logging debris flow activity. A WHA encompassing TR-1 and TR-10 basins is preferred. If only one basin was to be chosen, the one feeding site TR- 10 is preferred since it has multiple tributary channels.
Landscape-level Requirements for Tailed Frogs in the Skeena Region 32 Ascaphus Consulting 22/11/12
Figure 12. Trapline Creek showing sample sites and potential WHAs. Table 11 provides additional detail
Proposed Wildlife Habitat Areas
Proposed WHAs (Table 12) are situated in small south, east or west facing, moderate to moderately steep basins, and, where possible, irregular valley profiles that could break up the run- out of any potential slide or flood. WHA sites were placed in undisturbed areas, or partially logged sites with buffers and few road crossings, to provide good terrestrial habitat quality for adults and low anthropogenic channel disturbance. Tadpole abundance was also used as a selection criterion. Based on existing data for the Skeena Region, good numbers include 0.3+
Landscape-level Requirements for Tailed Frogs in the Skeena Region 33 Ascaphus Consulting 22/11/12 individuals per minute for time-constrained searches, or 3+ individuals/m2 for area constrained searches; the presence of older cohorts suggests a site with good ecological fitness.
Houwers’ (2000) proposed WHAs were taken into account as her primary selection criteria was streamside forest integrity, in addition to old-growth adjacency, fish presence, distance to nearest road, and length of creek. Tadpole abundance is a key indicator of habitat quality, which wasn’t considered in Houwers’ analysis. This information was retrieved from Dupuis and Bunnell (1997), and used to adjust her rankings. Houwers’ list of 36 sites was then short-listed and combined with additional sites from 2002 searches.
In the following list of proposed WHAs, spatial representation is considered to ensure that sub- populations in many sets of environmental conditions are protected. Ultimately, the protection of wider genetic pool may enhance the species ability to withstand such changes as global warming. A final factor in considering proposed WHA locations is distance from existing protected areas. For example, although there are many good creeks in the vicinity of Ascaphus Creek, it is better to protect creeks throughout the Skeena Region than to focus them all in one area.
This list of proposed WHAs is not exhaustive. More sites can be proposed and evaluated according to the criteria proposed in Table 11. In fact, the Coastal Inventory Team (CIT), headed by Tony Hamilton, has used the criteria in Table 11 to develop a GIS-based spatial model predicting optimal tailed frog habitat throughout the Mid and North Coast Forest Districts (Curtis and Ciruna 2003). Further, opportunities may exist to double up WHAs with existing reserve proposals to provide more encouragement for protection. For example, a number of Community Watersheds are proposed in the vicinity of Terrace (Table 13), yet only the Deep Creek watershed is formally designated. Many of the proposed community watersheds meet the criteria presented above and would make could candidates for WHA status.
Landscape-level Requirements for Tailed Frogs in the Skeena Region 34 Ascaphus Consulting 22/11/12
Table 12. Proposed WHA sites based on key landscape and habitat level variables
Creek Name Easting Northing Aspect Rugged- Basin Logging Comments ness (%) Area history (km2) Hazelton Mountains
Hardscrabble 538249 6062998 South 89 1.1 not No occurrence at mid (HS-9) and upper (HS-10) (HS-8) disturbed slopes; high sed contribution from gully sidewalls and cold temperatures; Range of viable habitat below 600 m Trapline 560977 6030898 East 72 1.8 not Deeply gullied in weak volcanic bedrock; old disturbed (TR-1,2,3) debris flows note; conventional logging will probably result in extensive gully sidewall failure activity and channel sedimentation Trapline 559724 6030107 East 47 3.4 not Deeply gullied in weak volcanic bedrock; old disturbed (TR-10) debris flows note; conventional logging will probably result in extensive gully sidewall failure activity and channel sedimentation Trapline 561920 6031961 South 51 2.5 flats Lower 500 m (below bench); runs through an (TR-6; GIS 765 from Dupuis and upstream are old growth patch with coarse stable substrates; Bunnell (1997)) logged protected from upslope hazards by large bench. Ascaphus (G. Hazelwood site; 543407 6064681 ESE 69 3 partially Configuration and location of this informal GIS 730-731 in Dupuis and logged reserve area represent an ideal WHA design. Bunnell 1997; AS-1, 2, 3) Fillslope pullback required. Shannon-Hardscrabble Face 540205 6059462 South 71 0.9 not Good tailed frog productivity along its length; (SHF1-3) disturbed originates from subalpine forest Shannon (GIS 401 in Dupuis and 536592 6060091 South 72 0.8 not Lake-fed with sub-alpine source Bunnell 1997) disturbed West Copper trib (UN-1 & UN-4) 565606 6067624 South 49 2.5 not West side of Copper river near NE range limit; disturbed weak volcanics; lower site is on apex of alluvial fan, where water flows underground during low flow periods; good abundance from mid slopes down
Landscape-level Requirements for Tailed Frogs in the Skeena Region 35 Ascaphus Consulting 22/11/12
Creek Name Easting Northing Aspect Rugged- Basin Logging Comments Ness (%) Area history (km2) West Copper trib (GIS 749 in 565850 6058400 East 63 1.0 not Km 38.1 on Copper Mainline; weak volcanics Dupuis & Bunnell 1997) disturbed and low flows; warmer temp. mid slope down Gosling (GIS 371 in Dupuis & 541226 6075298 NE 60 6.6 Hazelwood found >50 tadpoles; Non-glaciated Bunnell 1997) headwaters; NE range limit
Little Wedeene 515391 5998491 North 83 1.0 old growth Take Br1000 at km 19, for 4 km (GIS 264,265 in Dupuis & upstream; Non-glaciated headwaters Bunnell 1997) clearcut below Kleanza (GIS 743, 745 from 558192 6048292 South 61 2.4 buffered Km 22.3 on Kleanza Mainline; weak volcanics Dupuis & Bunnell 1997) and low flows; valley head location; cold temps moderated by southern aspect Coast Ranges Agate (GIS 247 from Dupuis & 453032 6008182 South 66 3.2 not Western most site; low tadpole numbers Bunnell 1997) disturbed Shames (S1-6) 503173 6037435 South 38 5.6 not Mid elevation area with north fork (SH-1) disturbed draining sub-alpine forest; main headwater cold. creeks in ski Good abundance in vicinity of ski hill. area buffered Scotia 459727 5997809 East 60 3.1 Logged; Productive coastal creek; warm temperatures; mid-seral extensively logged in lower reaches; recovery of stages stream side buffers needed Princess Royal Island 505390 5882690 South 58 2.2 Not visited; within proposed park area, north side of Bear Lake UTM coordinates given in NAD 83
Landscape-level Requirements for Tailed Frogs in the Skeena Region 36 Ascaphus Consulting 22/11/12
Existing Parks, Protected Areas and Proposed Reserves
There are no legally protected areas within the tailed frog’s range in the North Coast Forest District. Within Kalum District, Kitlope and Gitnadoix provincial parks provide large areas where tailed frog habitat is fully protected. These areas are located at the southern and northern edges of the range within the district, with both representing the Coast Mountain physiographic unit (Map 1).
The Ascaphus Reserve, within the Hazelton Mountains, was established for a research project where the impacts of logging could be studied using a paired basin (Apprentice-Joe Bell) approach (Ardea Biological Consulting 1999). With the completion of the project much of the Joe Bell watershed has been placed in informal reserve. The area was a proposed ecological reserve, but was rejected because more than 12% of the area (i.e., 15%) is developed. The basins are crossed by three roads and contain one clearcut. The upper road exhibits extensive tension cracking and settlement along the fillslope, and the risk of detrimental sedimentation to Joe Bell Creek is present (Friele 2002).
Shames Ski Area Reserve, within the Coast Mountains west of Terrace, was established to prevent forestry operations within the Ski Area boundary. Again, this is an informal log-around agreement. At the present level of development, the reserve provides protection to a mid slope population. However types of water uses, the nature of sediment and erosion controls, and future development goals are unknown.
Along the Skeena River and in the vicinity of Terrace there are a number of proposed community watersheds (Table 13). According to the Community Watershed website and Kalum Forest District planning maps, proposed community watersheds are situated west of Usk, east of Skovens and Kleanza, and Kitimaat Village. Deep Creek, near Terrace, is the only designated community watershed.
Table 13: Community watersheds in the Skeena Region within the range of the tailed frog
Community Creek Name Mapsheet Area (km2) Usk Shackleton Creek 103I.068 ~0.75 Skovens Skovens Creek 103I.068, 069 ~0.75 Kleanza Swede/ Singlehurst Creek 103I.068, 069 ~6.25 Terrace Deep Creek 103I.068, 058 ~4 Drake Drake Creek 103I.058 1.5 Eneeksagilagaguaw Eneeksagilagaguaw Creek 103I.057 1.4 Spring Spring Creek 103I.058 3.6 Wathl Wathl Creek 103H.097 121
Logging is allowed within community watersheds, but the planning standards are higher than for normal crown lands (BC Ministry of Forests and BC Ministry of Environment 1996). At the planning stage, greater attention is paid to terrain mapping with regard to potential landsliding, sediment erosion and connectivity to stream channels. However, there is no provision for mandatory buffering of perennial streams. Thus, community watersheds provide some protection with respect to instream life stages, but no protection for adult life stages of the tailed frog.
Landscape-level Requirements for Tailed Frogs in the Skeena Region 37 Ascaphus Consulting 22/11/12
Conclusions
Throughout the world, changing patterns of land use have resulted in habitat loss and in the fragmentation of what remains. This has lead to alterations in the community composition and processes that maintain ecosystem integrity. Attempts to reverse any decline in ecosystem quality requires knowledge of key spatial, compositional and functional attributes necessary for the health of a given ecosystem (Franklin 1993). “Focal” species can be useful at defining the minimal conservation requirements of disturbed ecosystems because their persistence is threatened by change (Lambeck 1997). For example, focal species that are dispersal-limited can define minimal landscape connectivity attributes. Those that are intolerant of change in certain environmental variables can define essential habitat compositional features. Along the same line, umbrella species have landscape level needs, and protecting them can ensure that species with smaller spatial requirements are also protected (Tracy and Brussard 1994; Wilcove 1993; Noss 1990).
There is no protection and/or special management around non-fish-bearing streams in British Columbia, or in many other jurisdictions. The recognition of this point led to the Symposium entitled “Small Stream Channels and Their Riparian Zone: their Form, Function and Ecological Importance in a Watershed Context” held at UBC in February 2002. Because of its lotic and terrestrial life stages, and because streams link whole watersheds, the coastal tailed frog (Ascaphus truei) provides the opportunity to look at a whole ecosystem (hydroriparian) as advocated by Franklin (1993). Its duel life stages make it an ideal focal species for guiding mountain stream management and protection because it is dispersal and habitat limited in both environments. Furthermore, it represents the largest and most common vertebrate in most headwaters, and is the dominant grazer, thereby serving as an umbrella species whose needs encapsulates those of other mid to upper-slope hydroriparian system inhabitants. The Coastal Inventory Team (CIT) of British Columbia has recognized the value of tailed frogs as a focal animal. The species, along with grizzly bears, salmon, and other key species, are being used to generate a model of regional protection and management priorities for the mid and north coast.
It is now understood that tailed frogs thrive in streams with intermediate disturbance regimes. The species primarily inhabits small rugged basins, where steeper turbulent flow results in coarser substrates favoured by tadpoles for foraging and refugia, and where fish predation can be avoided. Although it seems tailed frogs select steeper systems, by migrating upstream, tailed frog abundance is reduced in extreme environments by mortality. Extreme bedload movement causes trauma: the incidence of bedload transport increases in steep to very steep basins, and in areas with intense rainfall and flashy creeks. These factors may be compounded by the presence of weak bedrock, contributing abundant sediment to the channel system. Within a watershed, the back-ends of valleys are higher than valley mouths. Thus, creeks in valley-head settings are typically prone to snow avalanches, debris flows, and flashiness resulting from more pronounced orographic effects (DeScally et al., 2001), and support fewer tailed frogs. Temperature extremes are also not favoured by tailed frogs. At the northern range cold temperatures are limiting. High elevation sites, northern aspects, and creeks fed by late summer snow and ice melt have low abundance. Tadpoles are generally absent if temperatures are less than 6oC. As an indicator species, the survival requirements of Ascaphus truei have provided much insight for forest managers and land stewards regarding valuable mountain stream ecosystems, and on how to maintain the integrity of all non fish-bearing waters, whether they present moderate or extreme fluvial conditions. In addition, minimizing damage to their upstream environment will prevent downstream conditions from being impacted.
Landscape-level Requirements for Tailed Frogs in the Skeena Region 38 Ascaphus Consulting 22/11/12
Acknowledgements
Alex Frid, Donnavan Meirhofer, Len Vanderstar, and Chris Broster helped in the field. Bear Creek contracting and Interfor provided support while in Scotia Creek. Arnold Moy conducted GIS. Kirsten Gurney provided statistical advice. Grant Hazelwood provided additional tailed frog records, a number of them very useful in defining range boundaries, and reviewed the draft report.
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Appendix A: Example Site Form
Site Form 30 minuteTCS Recorder: Weath er: Date:
Ar ea & creek ID: Direction s:
Sample UTM Datu m: Zone: E: N: EPE:
Slope pos ition: lo wer midd le u pper Reach gradient (5 0 m average): Stream ord er:
Asp ect: Elevation (m): Water temp. (C): Roll: Pho tos:
Valley Geometry Total relief (m): Valley side pro file: Straigh t Con cave Con vex irregular
Valley side channel o verall slo pe(%): Headwater comments:
Bedrock Geology Field descriptio n:
Note: presence of metamorphic banding or foliation; local faults or shearzones; dimensions of representative fracture or joint sp acing (m); n ominal size class o f b edrock d eriv ed debris (e.g ., talu s/ru bble).
Reach type: Hillslo pe channel (<3 m sid ewall) Gully (>3 m sidewall) Fan Flo odp lain
If gully : Sid ewall length (m): Sid ewall material: Sid ewall instability: Y N
Channel proces ses: Flo ods Sediment floo ds Debris flows Sn ow avalanches Avu lsio ns Braiding Evid ence:
Note: presence/absence of moss on substrate; bed armouring (imbricate/loose); presence ofsediment wedges (thickness, age, abu ndance, n omimal clast size); recent debris flow/sediment floo ds (levees, age estimate from regen.); etc.
Channel units (features 1-7 channel width s in length ): well formed moderately formed no t formed Poo l (smooth water) Rif fle (rip pled with <10 % turbu lent) Rapid (10-5 0% turb ulent) Cascade (>5 0% turb ulent) Step formin g materials (rapid s & cascades): Log Bou lder Rock
Bankful width (cm): Bankful d epth (cm): Wet width (cm): Wet depth (cm):
Subs trate Poly lithic Mo nolith ic Angu lar Rou nded Bedrock channel Embededn ess: h igh mediu m low non e
Textu re: %Bould er (0.2 5-4.0 m): %Cobb le (64-2 56 mm): %Pebble (2-6 4 mm): %Sand (<2 mm):
Ten lar gest clasts B-axis (cm): Average:
Coarse wo ody debris: scattered jams log ging slash: light mediu m heavy Vegetation Log ged: Y N Buf fer leng th (m): Righ t bank : Left b ank: Fire regen.: Y N Stand age: <1 yr 1-1 0 y rs 10 -50 yrs 50 -100 yrs 10 0+ yrs Su b-alpine Alpine
Percent cano py (5 m in) Righ t bank : Left b ank: Percent und erstorey Righ t bank : Left b ank:
TAFR: late summer coho rts after Brown (19 90) 2: Lar ger 3: Develop ed 4: Losing # Adults Hatchlin g 1 head±h ind bud s hin d legs disk and tail Meta Juv enile male
Time 1st d etection: Note: record SVL (frogs), TL (tad) and tissue sample #’ s in field b ook .
Landscape-level Requirements for Tailed Frogs in the Skeena Region Ascaphus Consulting 22/11/12
Appendix B: Statistical (PCA) Summaries
Note: only eigenvalues greater than one and then significant results are shown.
Landscape-level Parameters (map-derived) Coast Mountains/all basins/occurrence Note small basins data are not shown as results are similar.
Correlation Matrix
Variable ruggedness aspect elevation geology Basin BGC area zone ruggedness 1.00 -0.17 -0.23 -0.05 -0.47 -0.13 aspect -0.17 1.00 0.06 -0.04 0.112 -0.08 elevation -0.23 0.06 1.00 0.50 -0.15 -0.60 geology -0.05 -0.04 0.50 1.00 -0.16 -0.46 Basin area -0.47 0.11 -0.15 -0.16 1.00 0.09 BGC zone -0.13 -0.08 -0.60 -0.46 0.09 1.00
Eigenvalues of the correlation matrix
Principle Eigenvalue Proportion of variability Cumulative component explained proportion CAO-1 2.10 0.35 0.35 CAO-2 1.55 0.26 0.61
Eigenvectors
Variable Component Loading* PC1 PC2 ruggedness 0.00 -0.70 aspect 0.04 0.35 elevation 0.59 0.18 geology 0.54 0.02 basin area -0.20 0.60 biogeoclimatic zone -0.57 0.00 *The highest positive and negative loadings are highlighted for ease of interpretation
Logistic Regression analysis with tadpole occurrence as dependent variable
Landscape Parameters X2 Value Likelihood
CAO-1 (biogeoclimatic zone, elevation, geology) 10.93 0.0009 CAO-2 (Basin area and ruggedness) 0.12 0.73
Landscape-level Requirements for Tailed Frogs in the Skeena Region Ascaphus Consulting 22/11/12
Landscape-level Parameters (map-derived) Coast Mountains/all basins/abundance
Correlation Matrix
Variable ruggedness aspect elev geology Basin area BGC zone ruggedness 1.00 -0.19 -0.16 0.08 -0.70 -0.41 aspect -0.19 1.00 0.04 -0.09 0.08 -0.11 elevation -0.16 0.04 1.00 0.41 -0.20 -0.48 geology 0.08 -0.09 0.41 1.00 -0.30 -0.43 Basin area -0.69 0.08 -0.20 -0.30 1.00 0.38 BGC zone -0.41 -0.11 -0.48 -0.43 0.38 1.00
Eigenvalues of the correlation matrix
Principle Eigenvalue Proportion of variability Cumulative component explained proportion CAA-1 2.34 0.39 0.39 CAA-2 1.47 0.25 .63
Eigenvectors
Variable Component Loading* PC1 PC2 ruggedness 0.42 -0.57 aspect -0.07 0.33 elevation 0.33 0.57 geology 0.41 0.32 basin area -0.51 0.31 biogeoclimatic zone -0.52 -0.19 *Highest positive and negative loadings highlighted for ease of interpretation
Multiple Regression Analysis with tadpole abundance as dependent variable
Landscape Parameters F Value Probability
CAA-1 (Biogeoclimatic zone, basin area; ruggedness 3.37 0.08 and geology) CAA-2 (Ruggedness, elevation) 0.02 0.90
Landscape-level Requirements for Tailed Frogs in the Skeena Region Ascaphus Consulting 22/11/12
Landscape-level Parameters (map-derived) Hazelton Mountains /all basins/occurrence Note small basins data are not shown as results are similar.
Correlation Matrix
Variable ruggedness aspect elevation geology basin BGC area zone ruggedness 1.00 -0.14 0.00 -0.01 -0.54 -0.02 aspect -0.14 1.00 0.27 -0.03 0.01 -0.07 elevation -0.001 0.27 1.00 0.16 -0.48 0.02 geology -0.01 -0.03 0.16 1.00 -0.25 -0.09 Basin area -0.54 0.01 -0.48 -0.25 1.00 0.16 BGC zone -0.02 -0.07 0.02 -0.09 0.16 1.00
Eigenvalues of the correlation matrix
Principle Eigenvalue Proportion of variability Cumulative component explained proportion HAO-1 1.83 0.30 0.30 HAO-2 1.30 0.22 0.52
Eigenvectors
Variable Component Loading* PC1 PC2 ruggedness 0.43 -0.54 aspect 0.08 0.68 elevation 0.47 0.47 geology 0.31 0.10 basin area -0.68 0.12 biogeoclimatic zone -0.17 -0.06 *Highest positive and negative loadings are highlighted for ease of interpretation
Logistic Regression analysis with tadpole occurrence as dependent variable
Landscape Parameters X2 Value Likelihood
HAO-1 (basin area, elevation, ruggedness) 0.18 0.67 HAO-2 (Basin area and ruggedness) 5.59 0.02
Landscape-level Requirements for Tailed Frogs in the Skeena Region Ascaphus Consulting 22/11/12
Landscape-level Parameters (map-derived) Hazelton Mountains/all basins/abundance
Correlation Matrix
Variable ruggedness aspect elevation geology Basin area BGC zone ruggedness 1.00 0.06 -0.07 -0.07 -0.54 -0.01 aspect 0.06 1.00 0.24 -0.09 -0.18 -0.15 elevation -0.07 0.24 1.00 0.23 -0.38 0.07 geology -0.07 -0.09 0.23 1.00 -0.27 -0.04 Basin area -0.54 -0.18 -0.38 -0.25 1.00 0.11 BGC zone -0.01 -0.15 0.07 -0.04 0.11 1.00
Eigenvalues of the correlation matrix
Principle Eigenvalue Proportion of variability Cumulative component explained proportion HAA-1 1.80 0.30 0.30 HAA-2 1.23 0.21 0.51 HAA-3 1.12 0.19 0.69
Eigenvectors
Variable Component Loading* PC1 PC2 PC3 ruggedness 0.41 -0.64 0.29 aspect 0.31 0.02 -0.71 elevation 0.44 0.52 -0.12 geology 0.29 0.10 0.34 basin area -0.67 0.14 -0.18 biogeoclimatic zone -0.13 0.15 0.51 *Highest positive and negative loadings are highlighted for ease of interpretation
Multiple Regression Analysis with tadpole abundance as dependent variable
Landscape Parameters F Value Probability
HAA-1 (Basin area, Elevation, Ruggedness) 0.76 0.39 HAA-2 (Ruggedness, Elevation, Geology) 5.42 0.03 HAA-3 (Aspect, Biogeoclimatic zone) 0.30 0.59
Landscape-level Requirements for Tailed Frogs in the Skeena Region Ascaphus Consulting 22/11/12
Habitat Level Parameters (Field Measurements)-occurrence
Correlation Matrix
Variable water geology reach bankfull flash embed disturb logged riparian temp slope discharge index or not canopy wtemp 1.00 -0.36 -0.16 0.20 -0.06 0.04 0.23 0.12 -0.13 geology -0.36 1.00 0.34 -0.14 0.02 -0.05 0.02 -0.11 0.31 rslope -0.16 0.34 1.00 -0.29 0.23 0.10 0.20 0.03 0.14 discharge 0.20 -0.14 -0.29 1.00 -0.01 -0.08 0.06 -0.01 -0.03 flash -0.06 0.02 0.23 -0.02 1.00 0.10 0.05 0.06 -0.03 embed 0.04 -0.05 0.10 -0.08 0.10 1.00 -0.17 0.85 -0.18 disturb 0.23 0.02 0.20 0.06 0.05 -0.16 1.00 -0.16 0.21 logged 0.12 -0.11 0.03 -0.01 0.06 0.86 -0.16 1.00 -0.18 canopy -0.13 0.31 0.14 -0.03 -0.03 -0.18 0.21 -0.18 1.00
Eigenvalues of the correlation matrix
Principle Eigenvalue Proportion of variability Cumulative proportion component explained FO-1 2.10 0.23 0.23 FO-2 1.84 0.20 0.44 FO-3 1.30 0.14 0.58
Eigenvectors
Variable Component Loading* PC1 PC2 PC3 water temp 0.22 -0.36 0.50 geology -0.33 0.42 -0.09 rslope -0.17 0.50 0.33 discharge 0.08 -0.38 0.14 flash 0.03 0.24 0.30 embeddedness 0.54 0.36 0.09 disturbance -0.22 -0.07 0.69 logging 0.57 0.29 0.11 riparian cover -0.37 0.14 0.17 *Highest positive and negative loadings are highlighted for ease of interpretation
Regression Analysis with occurrence as dependent variable
X2 Value Likelihood FO-1 (Logged, embeddedness, riparian cover, disturbance) 0.47 0.49 FO-2 (Reach slope, discharge, water temp, embeddedness) 10.87 0.001 FO-3 (Water temp, Channel disturbance, geology) 0.34 0.60
Landscape-level Requirements for Tailed Frogs in the Skeena Region Ascaphus Consulting 22/11/12
Habitat Level Parameters (Field Measurements)-abundance
Correlation Matrix
Variable water geology reach bankfull flash embed disturb logged riparian temp slope discharge index or not canopy wtemp 1.00 -0.30 0.06 -0.08 0.01 0.16 0.20 0.18 -0.15 geology -0.30 1.00 0.23 -0.24 0.24 -0.08 0.16 -0.13 0.29 rslope 0.06 0.23 1.00 -0.33 0.44 0.11 0.33 0.03 0.20 discharge -0.08 -0.24 -0.33 1.00 -0.06 -0.14 -0.18 -0.02 -0.11 flash 0.01 0.24 0.44 -0.06 1.00 0.25 0.11 0.20 -0.05 embed 0.16 -0.08 0.10 -0.14 0.25 1.00 -0.21 0.92 -0.25 disturb 0.20 0.16 0.20 -0.18 0.11 -0.21 1.00 -0.24 0.20 logged 0.18 -0.13 0.03 0.02 0.20 092 -0.24 1.00 -0.26 canopy -0.15 0.29 0.14 -0.11 -0.05 -0.25 0.20 -0.26 1.00
Eigenvalues of the correlation matrix
Principle Eigenvalue Proportion of variability Cumulative proportion component explained FA-1 2.32 0.23 0.23 FA-2 2.05 0.20 0.44 FA-3 1.30 0.14 0.58
Eigenvectors
Variable Component Loading* PC1 PC2 PC3 water temp 0.20 0.07 0.71 geology -0.26 0.35 -0.43 rslope -0.07 0.56 0.10 discharge 0.06 -0.39 -0.11 flash 0.12 0.45 -0.14 embeddedness 0.57 0.24 -0.12 disturbance -0.27 0.31 0.47 logging 0.59 0.16 -0.13 riparian cover -0.36 0.17 -0.13 *Highest positive and negative loadings are highlighted for ease of interpretation
Regression analysis with abundance as dependent variable
F Value Probability FA-1 (Logged, embeddedness, riparian cover, disturbance) 6.83 0.01 FA-2 (Reach slope, Flashiness, Discharge) 1.17 0.28 FA-3 (Water temp, Channel disturbance, geology) 0.42 0.52
Landscape-level Requirements for Tailed Frogs in the Skeena Region Ascaphus Consulting 22/11/12
Appendix C: Photos
(Compact disc)
Landscape-level Requirements for Tailed Frogs in the Skeena Region Ascaphus Consulting 22/11/12
Appendix D: Map
Landscape-level Requirements for Tailed Frogs in the Skeena Region Ascaphus Consulting 22/11/12
Appendix E: Digital information (report, database, statistics, map)
Landscape-level Requirements for Tailed Frogs in the Skeena Region