Landform Selection and Soil Modifications Associated with Arctic Fox (Alopex lagopus) Den Sites in Yukon Territory, Canada C. A. S. Smith; C. M. M. Smits; B. G. Slough Arctic and Alpine Research, Vol. 24, No. 4. (Nov., 1992), pp. 324-328. Stable URL: http://links.jstor.org/sici?sici=0004-0851%28199211%2924%3A4%3C324%3ALSASMA%3E2.0.CO%3B2-1 Arctic and Alpine Research is currently published by The Regents of the University of Colorado, a body corporate, contracting on behalf of the University of Colorado at Boulder for the benefit of INSTAAR.
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Arctic and Alpine Research, Vol. 24, No. 4, 1992, pp. 324-328
Landform Selection and Soil Modifications Associated with Arctic Fox (Alopex Iagopus) Den Sites in Yukon Territory, Canada§ C. A. S. Smith,* C. M. M. Smits,t and B. G. Slough7 *Agriculture Canada, P.O. Box 2703, Whitehorse, Yukon YlA 2C6 Canada. t Fish and Wildlife Branch, Department ofRenewableResources, P.O. Box 2703, Whitehorse, Yukon YlA 2C6, Canada.
Abstract Arctic fox (Alopex lagopus) dens were examined in the unglaciated portion of the Yukon Coastal Plain and on Herschel Island. Den site selection relative to landform type was evaluated for 65 dens. O n the Yukon Coastal Plain foxes established dens on sandy fluvial and wind-modified (dunes) fluvial deposits almost exclusively. O n Herschel Island, moderately eroded landscapes were selected over noneroded, slightly eroded, and wetland terrain. The use of terrain maps proved to be useful in defining suitable den habitat. Chemical and physical properties of soil were compared on and immediately adjacent t o 25 dens. Mean values for soil temperature, depth to permafrost, soil particle size, pH, N, and exchangable K were significantly different (P < 0.05) between on-den and off-den samples in both study areas. Total carbon, total phosphorous, and C:N were significantly different on Herschel Island but not on the Yukon Coastal Plain. The role of foxes in modifying soil chemical and physical properties is discussed relative to differences inherited through the parent material properties.
Introduction The importance of den use by arctic fox (Alopex lagopus) with respect to reproduction and rearing has been discussed by Chesemore (1969), Eberhardt et al. (1983), and Macpherson (1969). Both den site conditions as well as landscape location of dens are important to reproduction and rearing. Preference for southfacing den burrow openings, well-drained soil conditions, and warmer soil temperatures on the den mound compared to the surrounding landscape are a few of the properties that often characterize arctic fox dens (0stbye et al., 1978; Smits et al., 1988). This suggests that den site selection may be landformdependent and that terrain maps might be used to assess regional denning potential and key den habitat. The presence of fox dens has impact on the vegetation ecology (Garrott et al., 1983). The lushness of the on-den vegetation community compared to the surrounding off-den tundra has been attributed to the local addition of organic materials and to increased soil aeration through mixing and digging (Underwood and Mosher, 1982; Smits et al., 1988). Although these effects have been described, we are not aware of any quantitative data having been presented for soil quality changes associated with arctic fox den activities. The objectives of our study were twofold. First, we wished to evaluate the nature of landform selection by denning arctic foxes and, second, to describe soil modifications that take place through faunal activity at den localities.
Study Area We compared arctic fox den sites on Herschel Island (101 km2), an offshore glacial feature composed of ice-thrust marine sediments (Mackay, 1959; Bouchard, 1974) with the low-lying fluvial and pediment surface of the unglaciated Yukon Coastal Plain (655 km2) (Bostock, 1970; Rampton, 1982). Each area was selected to provide a range of landscape conditions that were P CLBRR Contribution No. 92-1 1.
324 / ARCTICAND ALPINERESEARCH
typical of the Yukon Beaufort Sea coastal region (Fig. 1) and where some previous arctic fox inventory had been conducted (Smits and Slough, unpubl. data).
The marine sediments that compose the bulk of Herschel
Island were thrust and deposited by a late Wisconsinan glaciation
(Rampton, 1982). The sediments are predominantly ice-rich silts
and clays with occasional ridges and stringers of sand and gravel.
The island is undergoing rapid thermal and water erosion that
produces many gulleys and erosional landforms. Spits and off-
shore bars are common along the island's coastline (Smith et al.,
1989).
The Yukon Coastal Plain east of the Firth River was gla-
ciated at the time of the formation of Herschel Island; however,
glaciation did not proceed farther west (Dyke and Prest, 1987). The unglaciated portion of the coastal plain is devoid of glacial landforms other than some outlying gravelly glaciofluvial deposits. The majority of the area was dominated by large fluvial fans of the Malcolm and Firth rivers.
Methods Arctic fox dens were initially located in the study areas by systematic, low-altitude aerial surveys according to the method outlined by Smits et al. (1988). Consistent and uniform effort was made in summer reconnaissance flights between 1984 and 1988 to locate and plot all dens. Sixty-five dens were located, 30 on the coastal plain and 35 on Herschel Island. The association of dens with specific landscape conditions was evaluated using the most recent and detailed terrain (geomorphology) maps available for the areas. For Herschel Island, a terrain map (Smith et al., 1989) at a scale of 1:25,000 was used to define landforms on which dens were located. This map consisted of eight named landform-based mapping units which describe both soil and vegetation conditions for the island. Definitions of each named mapping unit are given in Table 1. On the unglaciated Yukon Coastal Plain a Geological Survey of Canada regional surficial geology map (Rampton, 1982) at a O 1992 Regents of the University of Colorado
B e o u f o r f
S e a
FIGURE 1. Locations and extent of the two study areas in northern Yukon Territory.
TABLE 1
Arctic fox den distribution on Herschel Island and Yukon Coastal Plain according to terrain mapping units
Map unit name
Description
Area (km2)
Number of fox
dens observed
Selectivity
Herschel Island, total area 101.1 km2, 35 dens Komakuk Jaeger Herschel Thrasher Guillemot Plover Avadlek Orca
Slightly eroded uplands Moderately eroded uplands Level uplands Strongly eroded uplands Polygonal wetlands Upland patterned ground Marine spits and beaches Fine alluvium
Avoided Selected Avoided Proportional Proportional Proportional Avoided Avoided
Yukon Coastal Plain, total area 654.8 km', 30 dens Fluvial Lacustrine Colluvial Glaciofluvial Marine
River fans and deltas Lake-bottom sediments Slope wash Glacial outwash Spits and beaches
scale of 1:125,000 was used for analysis. The legend was composed of 17 mapping units based on Quaternary landforms, of which five occurred in the study area (Table 1). Mapping methods and composition of individual mapping units are given by Smith et al., (1989) and Rampton (1982). While the size of the study areas and the map scales used in the analysis differed, the maps were used to represent the landscape condition at the den site in both areas. Each surveyed den was allocated to a mapping unit. Total area covered by each mapping unit was calculated using a digital planimeter and expressed as a percentage of the study area. The statistical technique evaluating preference or avoidance for an individual map unit involved the use of a Bonferroni Z statistic (Neu et al., 1974). Our sample size met the required conditions necessary for the use of this technique as outlined by
Selected Avoided Avoided Avoided Avoided
Roscoe and Byars (197 1). This technique compares the proportion of dens located on each unit with areal availibilty of each map unit using the chi-square statistic. If the chi-square test is significant (i.e. a = 0.05), then Bonferroni confidence limits are constructed, and the map unit is assigned to one of the following categories; selected, avoided, or proportional (no preference). Subsequent to plotting den localities on the landform maps, systematic, paired on-den and off-den soil sampling was conducted at a total of 25 den sites. On the Yukon Coastal Plain, 8 dens located on the fluvial mapping unit were sampled. On Herschel Island, 17 dens located on four different mapping units were sampled. The number of mapping units sampled and the distribution of sampled dens reflected the diversity in landforms utilized as den sites on Herschel Island and the coastal plain. At each den locality soil temperatures were measured in
TABLE 2
On-den and off-den soil physical propertiesfor composited samples
n
Mapping unit
Site
Temp
("C at 10 cm) depth
Depth to
perma frost
% sand
% silt
% clay
Textural class
Herschel Island 1
Plover-slightly eroded with patterned ground
On-den Off-den
9.0 5.0
60.0 35.0
82.8 67.6
109.9 22.7
7.2 9.7
7
Komakuk-slightly eroded
On-den Off-den
9.6 6.9
59.1 34.9
70.7 39.3
24.7 45.0
3.3 15.3
7
Jaeger-moderately eroded
On-den Off-den
8.9 7.0
64.2 37.5
73.6 57.3
24.9 40.0
1.9 5.0
2
Thrasher-strongly eroded
On-den Off-den
10.0 7.0
75.5 40.5
49.0 18.5
43.5 44.0
8.0 36.0
Loam Silty Clay Loam
Total
On-den Off-den
63.5' (13.6) 36.7 (7.7)
70.6* (9.9) 46.1 (19.6)
26.1* (9.1) 40.5 (14.6)
3.4* (3.6) 13.4 (12.3)
Sandy Loam
Loam
84.7* (18.4) 67.5 (6.6)
87.8* (4.3) 82.5 (10.5)
7.1* (3.5) 11.6 (9.4)
4.9* (1.1) 5 0 (1.1
Sand
Loamy Sand
17
9.3* (1.3) 6.8 (1.7)
Loamy Sand Sandy Loam Sandy
Loam
Loam
Loamy Sand
Sandy Loam
Yukon Coastal Plain (all dens located on Fluvial mapping unit) 8
Total
On-den Off-den
5.2* (1.1) 4.5 (1.2)
* Indicates significantly different values at a = 0.05 level. Standard deviation of total values given in parentheses.
July 1988 and 1989 at 10 cm depth at two on-den points and two adjacent off-den points and mean values for each set recorded. Also surface (0-1 5 cm) soil samples were collected at random from six points on the den surface (excluding den openings) and from six points on the surrounding landscape within a 50 m radius of the den. Samples of approximately 150 cm3 were collected using an Oakfield sampling tube. The six individual samples were then composited and mixed subsequent to laboratory analyses. To evaluate modifications of soil nutrient regime by foxes, major nutrient element contents were determined. Soil particle size analysis was conducted to determine the proportions of sand, silt, and clay in each sample. Soil samples were air-dried and ground prior to analyses. All analyses wereconducted on the < 2 mm soil fraction. Six chemical properties were analyzed using percent methods outlined by Sheldrick (1 984): pH in CaCl,, total percent carbon and total percent nitrogen by Leco induction furnace, total phosphorous by acid digestion, exchangeable potassium by NaCl extraction, and particle size by pipet method. Soil texture classes are according to (ACECSS, 1978). Differences in soil properties for all on and off dens samples within each study area were analyzed by comparison of sample means of paired observations using Student's T-test (at the a = 0.05 level of significance).
Results LANDFORM SELECTIVITY The nature and diversity of landforms and resultant terrain map units differ as a result of the differences in the size and physiography of the two study areas. Table 1 outlines the map unit names, the occurrence of dens on each and the selectivity for each unit. On Herschel Island, 32 of the 35 dens identified were located on eroded terrain. The majority of the island had a slightly eroded character (Komakuk map unit, Table 1). While seven dens were identified on this unit, they were proportionately un-
der-represented and the unit was therefore interpreted as being avoided. The moderately eroded terrain (Jaeger map unit) was the selected unit for denning and the key landscape condition utilized by arctic foxes. The other units had proportional representation. Strongly eroded terrain (Thrasher) provided erosional mounds suitable for some denning, raised mounds within the polygonal wetlands (Guillemot) were utilized in two cases, and on nonsorted patterned ground (Plover) in one case. None of the other mapping units defined for the island exhibited any den activity. On the unglaciated coastal plain, fluvial landforms were the selected landscape for den location (Table 1). In many cases small eolian ridges formed on the fluvial sands provided the well drained, excavatable material suited for den construction. One den was located on a lacustrine landform. These low-lying, often poorly drained landforms generally lacked the required relief or were too wet for denning. No den activity was recorded in any other map unit. PHYSICAL AND CHEMICAL SOIL PROPERTIES In all cases, mean values for soil temperature and the depth to permafrost were higher on-den than off-den. On Herschel Island, the texture of den soils differed depending on the degree of landscape erosion. On the slightly to moderately eroded mapping units, (Plover, Jaeger, and Komakuk, Table 1) the dens were located in sandy outcrops within the generally fine-textured soils that comprise the upland portion of the island. The den soils ranged from 49 to 82% sand (Table 2), mean percent sand in off-den soils in individual mapping units was approximatly 15 to 30% less. On the strongly eroded unit (Thrasher), the dens were located on erosional remnant mounds formed in exposed fine-textured marine sediments. The den soils in the Thrasher mapping unit were loam (49% sand, 8% clay),the off-den textures were silty clay loam (18% sand, 36% clay). All differences between on-den and off-den mean values for sand, silt, and clay were significantly different.
TABLE 3
On-den and off-den soil chemical properties for composited samples exch.K n
Mapping unit
Site
pH
O/oC
%N
%P
(meq/ 100 g)
C:N
Herschel Island 1
Plover-slightly eroded with patterned ground
7
Komakuk-slightly eroded
7
Jaeger-moderately eroded
2
Thrasher-strongly eroded
17
Total
Yukon Coastal Plain (all dens located on Fluvial mapping unit)
8
Total
On-den Off-den
6.36* (0.16) 6.56 (0.21)
* Indicates significantly different values at a = 0.05 level. Standard deviation of total values given in parentheses.
On the Yukon Coastal Plain, all dens were located on sandy fluvial landforms. The materials utilized for den sites were only slightly coarser (87.8% sand) than the surrounding landscape (82.5% sand) but all mean values for sand, silt, and clay were significantly different between on-den and off-den soils. Results of the six chemical property analyses are given in Table 3. In all cases soil p H was lower on-den than off-den. This is the result of slight acidification through the addition of fecal material, urine and decay of transported organic food materials at the den site. Absolute differences in soil pH between the two study areas reflect the differences in geologic parent material origins of the two study areas (i.e. alkaline marine sediments on Herschel Island versus slightly acidic fluvial sediments on the coastal plain). Similiar trends for increased nutrient (N, P, K) levels in on-den soils exist for each of the individual Herschel Island mapping units as well as the combined datasets for the two study areas. The distribution of total C, which is a measure of organic matter in soils, differed in the two study areas. On Herschel Island, both the soils on the dens and the surrounding landscape initially had distinct surface humus layers; the transport of organic materials to the den site eventually produced higher percent C on-den relative to off-den soils. On the coastal plain, mounds utilized by foxes were usually dune features formed on the fluvial landform. These appeared to be naturally lower in organic matter than the surrounding tundra. Although nutrients were imported to these den sites (seen as higher total N values) the total soil organic matter remained lower on-den than offden on the coastal plain. On Herschel Island total soil C was higher on-den than in the off-den samples. Total nitrogen was higher on-den than off-den in both study areas. There was little difference in the values for phosphorous and potassium at all sites. The C:N ratio is a measure of the degree of organic matter decomposition and the ability for microbial mineralization and nutrient release (Tisdale and Nelson, 1975). The on-den values indicate that the humus in the den soils is mineralizable and considerable plant-available nutrients may be present. On Herschel Island significant differences were evident for
all physical and chemical properties analyzed. On the coastal plain total P and C:N were not significantly different (Table 3).
Discussion and Conclusion The selection of moderately eroded terrain on Herschel Island for denning is likely related to the prevalence of erosional features (i.e. mounds) that are reported to provide suitable aspect, drainage, and protection from winds (Chesemore, 1969). The strongly eroded terrain provided some habitat but areas undergoing active erosion or having very steep slopes were not suited for denning. Slightly eroded or noneroded terrain, the most common landform conditions on the island, appeared to lack suitable niches for den establishment. Den sites on the Yukon Coastal Plain were almost completely confined to the sandy fluvial and associated dune deposits. This very common landform type covered over 80 percent of the study area. By comparison, on Herschel Island the majority of dens were concentrated on a moderately eroded landform type which covered only 20 percent of that study area. Although fox dens appear to be nonrandomly associated with particular landforms, the availability and distribution of these landforms alone does not determine den abundance within a physiographic region. Factors such as prey availability and distribution, and tenitorial behavior may also play an important role in this regard. Our study suggests that it is feasible to evaluate the suitability of an area to sustain fox dens using various scales of terrain maps over a range of physiographic conditions. Both the Yukon Coastal Plain surficial geology map (based on age and origin of landform) and the Herschel Island terrain map (based on landform and associated degree of erosion) worked well in stratifying the landscape in a way that could be related to denning habitat. In the Yukon Beaufort Sea coastal region we can make some predictions about the distribution of prime denning habitat by using terrain maps to extrapolate our knowledge beyond the immediate study areas. Difference between faunal sites and the surrounding landscape are strongly evident in the field. Denning activity added
food scraps, bones, and fecal material to the den soil such that over time nutrients (N, P, and K) became higher on-den relative to off-den. Lush growth and a change in the dominant species in the vegetation community are evident near dens (Garrott et al., 1983), bird nests, or faunal remains. While we are able to demonstrate differences in various total nutrient element levels, greater differences might be shown by comparing plant-available or mineralizable nutrient levels (Waring and Bremner, 1964). The measurement of nutrients mineralized under standardized laboratory conditions provides indices ofthe more labile nutrient pools and can reveal changes in the character of organic matter that may be independent of total nutrient levels (Olson and Lowe, 1990). Some differences between on-den and off-den soil properties are the result of inherent parent material properties. These differences illustrate that Arctic foxes select den sites based to some extent on these properties (percent sand, percent clay, percent silt as well as stone content) which do not change over time through denning activities. However, nutrient levels, soil chemistry, and the thermal regime are changed by denning activity. Over long periods of time these properties are significantly altered relative to the surrounding landscape as foxes import nutrients, lower the permafrost table and physically mix the soil. In doing so they change the productivity of the soil. Faunal activity must be considered a vital component in nutrient cycling in tundra ecosystems.
Acknowledgments The study was funded by the Yukon Department of Renewable Resources, Agriculture Canada's Centre for Land and Biological Resources Research, and the Northern Oil and Gas Action Program (NOGAP). Part of the work was performed as a Wildlife Management Program under the Inuvialuit Final Agreement. Some heliopter support was provided by Polar Continental Shelf Project. We thank Margot Santry for her assistance with data processing and statistical analyses. We thank the Canadian Park Service for allowing us to work in Northern Yukon National Park. The cooperation of the Department of National Defense, Ottawa, and of Felec Services Inc., Winnipeg are greatly appreciated.
References Cited Agriculture Canada Expert Committee on Soil Survey (ACECSS), 1987: The Canadian System of Soil Classlfrcation. 2nd ed. Agriculture Canada Publ. 1646. 164 pp. Bostock, H. S. 1970: Physiographic regions of Canada. Geological Survey of Canada, Map 1254A. Scale 1:500,000. Bouchard, M., 1974: Geologie de depots de file Herschel, Territoire, du Yukon. M.Sc. thesis, Universitk de Montrkal, Montreal. 125 pp.
Chesemore, D. L., 1969: Den ecology of the arctic fox in northern Alaska. Canadian Journal of Zoology, 47: 12 1-1 29. Dyke, A. S. and Prest, V. K., 1987: Late Wisconsin and Holocene history of the Laurentide ice sheet (map 1703A, sheet 1). Gkographie Physique et Quaternaire, 4 1: 237-263. Eberhardt, L. E., Garrott, R. A., and Hanson, W. C., 1983: Den use by arctic foxes in northern Alaska. JournalofMammalogy, 64: 97-102. Garrott, R. A., Eberhardt, L. E., and Hanson, W. C., 1983: Arctic fox den identification and characteristics in Northern Alaska. Canadian Journal of Zoology, 6 1: 423426. Mackay, J. R., 1959: Glacier ice-thrust features of the Yukon coast, Canada. Geographical Bulletin, 13: 5-2 1. Macpherson, A. H., 1969: The dynamics of Canadian arctic fox populations. Canadian Wildlife Service Report Series, 8. 52 PP. Neu, C. W., Byers, C. R., and Peek, J. M., 1974: A technique for analysis of utilization-availabliliy data. Journal of Wildlife Management, 38: 54 1-545. Olson, B. M. and Lowe L. E., 1990: Effects of intensive vegetable production on chemical properties and nutrient mineralization of a British Columbia humisol. Canadian Journal of Soil Science, 70: 445460. Dstbye, E., Skar, H. J., Svalastog, D., and Westby, K., 1978: Arctic fox (Alopex lagopus) and red fox (Vulpes vulpes) on Hardangervidda; den ecology, distribution and population status. Meddelelserfra Norsk Viltforskning, 3: 1-66. Rampton, V. N., 1982: Quaternary geology ofthe Yukon Coastal Plain. Geological Survey of Canada Bulletin, 3 17. 49 pp. + maps. Roscoe, J. T. and Byars, J. A., 197 1: An investigation of the restraints with respect to sample size commonly imposed on the use of the Chi-square statistic. Journal of American Statistical Association, 66: 755-759. Sheldrick, B. H. (ed.), 1984: Analytical Methods Manual, 1984: Land Resource Research Institute. Agriculture Canada, Research Branch, Ottawa. LRRI Contribution No. 84-30. 182 PP. Smith, C. A. S., Kennedy, C. E., Hargrave, A. E., and McKenna, K. M., 1989: Soil and Vegetation ofHerschel Island. Research Branch, Agriculture Canada, Ottawa. LRRC Contribution No. 88-26. 101 pp. + maps. Smits, C. M. M., Smith, C. A. S., and Slough, B. G., 1988: Physical characteristics of arctic fox (Alopex lagopus) dens in northern Yukon Territory, Canada. Arctic, 4 1: 12-1 6 Tisdale, S. L. and Nelson, W. L., 1975: Soil Fertility and Fertilizers. 3rd ed. New York: Macmillan. 694 pp. Underwood L. and Mosher, J. A., 1982: Arctic fox (Alopex lagopus). In Chapman J . A. and Feldhamer, G. A. (eds.), Wild Mammals of North America: Biology, Management and Good Economics. Baltimore: Johns Hopkins University Press, 491503. Waring, S. A. and Bremner, J. M., 1964: Ammonium production in soil under water-logged conditions as an index of nitrogen availability. Nature, 201: 95 1-952.
Ms submitted March 1992
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References Cited Den Use by Arctic Foxes in Northern Alaska Lester E. Eberhardt; Robert A. Garrott; Wayne C. Hanson Journal of Mammalogy, Vol. 64, No. 1. (Feb., 1983), pp. 97-102. Stable URL: http://links.jstor.org/sici?sici=0022-2372%28198302%2964%3A1%3C97%3ADUBAFI%3E2.0.CO%3B2-J
An Investigation of the Restraints with Respect to Sample Size Commonly Imposed on the Use of the Chi-Square Statistic John T. Roscoe; Jackson A. Byars Journal of the American Statistical Association, Vol. 66, No. 336. (Dec., 1971), pp. 755-759. Stable URL: http://links.jstor.org/sici?sici=0162-1459%28197112%2966%3A336%3C755%3AAIOTRW%3E2.0.CO%3B2-F
