British Columbia Mine Reclamation Symposium

Control of vegetation damage by small rodents on reclaimed land Green, Jeffrey Emil, 1952- 1982-01-05

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Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1982. The Technical and Research Committee on Reclamation          CONTROL  OF  VEGETATION  DAMAGE  BY  SMALL  RODENTS  ON   RECLAIMED  LAND Paper Presented  by J.E.  Green  LGL Limited  Edmonton, Alberta                           135 Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1982. The Technical and Research Committee on Reclamation  CONTROL OF VEGETATION DAMAGE BY SMALL RODENTS ON RECLAIMED LAND INTRODUCTION Land disturbed during the mining of the oil sands of northeastern Alberta will require extensive programs of reclamation and revegeta-tion. The long term reclamation objective is to establish a self-sustaining plant community of similar productivity to that of the predisturbed state (Fedkenheuer 1979). Typically a dense ground cover of agronomic grasses and legumes has first been established to stabilize the sand dykes. Tree and shrub planting programs have then been implemented on some reclamation sites once a dense ground cover has been established. The tree and shrub planting program is considered one means of accelerating the establishment of an early serai forest com-munity. The afforestation programs have been only moderately successful, how-ever, because of the high mortality of some species of young trees (Seiner and Thompson 1977; Fedkenheuer 1979; Shopik 1980). Sapling death has been attributed to insect defoliation, to damage during planting, to disease, to nutrient and moisture deficiencies, to competi-tion with ground cover (e.g., grasses and legumes), and to small rodent damage (Radvanyi 1978; Sherstabetoff et al. 1978; Fedkenheuer 1979; Shopik 1980). Damage by small rodents, particularly Microtus pen-nsylvanicus (the meadow vole) is believed to be one of the major causes of sapling death. A study of the small rodent problem in afforestation sites was begun by LGL Limited in 1977. First, an extensive review of the literature on small mammal damage to plants and methods of control was completed (Green 1978). Field studies of small rodents, small rodent damage, vegetation cover, and tree and shrub performance in reclamation areas on the Suncor lease were begun in 1978 (Green 1980b, 1980c). Similar field studies of small rodent populations and small rodent damage in natural forest and shrub communities in the Athabasca Basin were conducted during 1978 and 1979 (Green 1980c). 137 Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1982. The Technical and Research Committee on Reclamation  METHODS STUDY PLOTS Six reclamation study areas were established on the Suncor Inc. lease during 1978 (Figure 1). All six areas were on Slope 6 (305 m to 320 m level) of the Suncor Inc. Tar Island dyke. Construction of Slope 6 was completed in the fall of 1977 and preparation for seeding was begun in the spring of 1978. Details of preparation and seeding are summarized by Green (1980a). All study plots were of similar design. Each con-sisted of a 1.13 ha (250 m x 45 m) vegetation treatment area within which was located a 0.76 ha small rodent live-trapping grid (Figure 2). Three methods of controlling small mammal damage that were recommended by Green (1978) were initially evaluated in this study—the application of an animal repellent to seedlings, the provision of supplementary food supplies/ and a reduction of ground cover. The experimental plots included a control plot, four single treatment plots, and one plot that combined three of the treatments. However, beginning in 1980, emphasis was placed on an evaluation of ground cover manipulation as a method of control. The repellent and supplementary food treatments subsequently were discontinued; a discussion of these latter treatments is included in Green (1980a). Two basic types of ground covers were assessed in this study. The first treatment involved the hydroseeded application of agronomic grasses such as creeping red fescue, brome grass, crested wheatgrass, and pubescent wheatgrass and of legumes such as alfalfa, common clover, alsike clover, and sanfoin. This seed mix was applied to the entire treatment area of the Supplementary Food, Repellent, and Control study areas. On the Stripping Trial study area, however, only a horizontal 15 m wide strip along the top and bottom of each study area was hydroseeded, such that a central 15 m wide strip was left unvegetated. The second treatment initially involved only revegetation by natural means; following preparation of the soil in 1978, no amendments or seed were applied to either the Reduced Cover or Combined Treatment study areas. In summer 1980, however, a seed mix of Agropyron violacium, Festuca saximontana, and Poa palustris was sparsely hydroseeded on these two sites. During May and early June of 1979, Suncor Inc. planted approximately 1,200 tree and shrub seedlings on each experimental plot.   Twelve 138 Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1982. The Technical and Research Committee on Reclamation   Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1982. The Technical and Research Committee on Reclamation    Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1982. The Technical and Research Committee on Reclamation  species of trees and shrubs were planted at 2.1 m spacings in blocks consisting of double rows of each species that varied from 14 to 20 seedlings long. Species planted were dogwood. Laurel willow, Siberian larch, Basford willow, caragana, Northwest poplar, acute willow, white spruce, Scots pine, chokecherry, Walker poplar, and Russian olive. Three blocks of seedlings were established on each study plot. The tree and shrub planting blocks on the Stripping Trial differed from the remaining five study areas in that planting blocks of paper birch, trembling aspen, alder, and Siberian larch at 1 m spacings also were established within the central unvegetated area. VEGETATION ANALYSES Vegetation analyses were conducted by LGL Limited on the six study plots during late June of 1979, 1980 and 1981. Estimates were made of the density, species composition, and vertical distribution of vegetation cover. Within each study area, information was obtained from 30 random sampling locations during 1979 and 50 random sampling locations during 1980 and 1981. The percent ground cover of each plant species present within a 1 m2 quadrat was estimated using a Braun-Blanquet cover scale (Kershaw 1966) (Figure 3). Vertical composition of vegetation was estimated following Nudds (1977). Tree and shrub densities and amounts of small rodent damage within a 16 m2 quadrat were estimated. Enumeration and evaluation of all seedlings were conducted by Suncor Inc. during June and August of 1980 and 1981. Tree and shrub assess-ments included a measure of plant height, condition, and rodent damage. Survival rates also were determined for each species. SMALL MAMMAL TRAPPING TECHNIQUES Small mammal live-trapping techniques were similar to those described by Krebs et al. (1969). The trapping grid on each study area consisted of a 5 x 20 grid of trapping stations at 10 m intervals. One live trap was placed within a 1.5 m radius of each trap station. Each study area was live-trapped for three days, once every three weeks from late April/ early May to late November during 1979 to 1981. During 1978, all study areas were live-trapped only during September and October. All new animals were ear-tagged with a numbered fingerling fish tag when first captured. After tagging or when tagged animals were captured 141 Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1982. The Technical and Research Committee on Reclamation   Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1982. The Technical and Research Committee on Reclamation  during subsequent trapping periods, the tag number, species, trap location, sex, breeding condition, weight, body length, an estimate of age, number of wounds on the posterior portion of the body, and number of sub-dermal parasites (Cuterebra spp.) were recorded. RESULTS SMALL RODENT POPULATIONS During this study, four species of small rodent, Clethrionomys gapperi, Microtus pennsylvanicus, Peromyscus maniculatus, and Zapus hudsonicus, were captured on the six study areas.  In addition, two species of shrews, Sorex cinereus and Sorex obscurus, and two species of mustelid, Mustela erminea and Mustela nival is, were captured. Woodchucks (Marmota monax), snowshoe hares: (Lepus atnericanus), and red fox (Vulpes vulpes) were observed but not captured on the reclamation sites.  Because only C. gapperi, M. pennsylvanicus, and P. maniculatus were captured regularly and in moderate to high numbers, demographic analyses were restricted to these three species. Population changes of small rodents were assessed using the minimum number known to be alive (MNA) (Chitty and Phipps 1966) as a biased estimate of population size. Comparisons of MNA estimates of C. gapperi, M. pennsylvanicus, and P. maniculatus on each of the six study areas (Figures 4 to 6) indicate that habitat use and seasonal population trends differed among study areas and among species. Microtus pennsylvanicus was the most abundant species of small rodent on most study areas. Numbers were consistently highest on the Supplemen-tary Food study area, followed by the Repellent and Control study areas (all areas with agronomic grass and legume cover). Numbers of M. pennsylvanicus increased appreciably between 1979 and 1980 on almost all study areas except the Reduced Cover study area. Peak numbers of M. pennsylvanicus were attained on most study areas by mid- to late September 1980 and remained high on some areas until spring 1981. Numbers declined rapidly on all areas during early summer 1981. Based on this study and on information obtained by Radvanyi (1978) and Michielson and Radvanyi (1979) during a four-year study of small rodent populations on established reclamation sites within the Suncor Inc. lease, it appears that M. pennsylvanicus populations in reclamation 143 Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1982. The Technical and Research Committee on Reclamation   Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1982. The Technical and Research Committee on Reclamation   Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1982. The Technical and Research Committee on Reclamation   Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1982. The Technical and Research Committee on Reclamation  sites undergo cyclic fluctuations in population size every three to four years. Michielson and Radvanyi (1979) indicated that their study populations increased from low numbers in 1975 to peak numbers during spring 1978, and then declined to low numbers in fall 1978. In this study, most study populations increased from low numbers in fall 1978 to peak numbers during May and June 1981 and then declined sharply. These cyclic changes in number are similar to the 3 to 4 year cycles observed in a number of microtine populations in natural areas (Krebs and Myers 1974). Peromyscus maniculatus was present in low numbers on all study areas but was most abundant on the Reduced Cover, Combined Treatment, and Control study areas. Population trends on these three study areas and the Stripping Trial study area indicate that numbers of P. maniculatus have increased gradually over the 1979/81 period. Numbers on the Supplemen-tary Food and Repellent study areas, however, have changed little during the same period (0 to 9 animals). Prior to 1980, only one C. gapperi had been captured on any of the rec-lamation study areas. However, during late summer 1980, numbers of C. gapperi increased on all areas with the exception of the Supplementary Food study area, where no C. gapperi were captured. Numbers of C. gapperi were highest on the Combined Treatment, Reduced Cover, and Control study areas. During 1981, C. gapperi were absent from all study areas with the exception of the Reduced Cover, Combined Treatment and Control study areas during the early spring. These population trends plus reproductive information (i.e., proportions of mature animals in breeding condition, pregnancy rates) showed that M. pennsylvanicus and P. maniculatus rapidly established resident, breeding populations in reclamation areas. In contrast, C. gapperi were only sporadically abundant and appeared to be transient, non-breeding animals. VEGETATION COVER Assessments of vegetation cover on the six study areas during 1979/81 show that the vertical and horizontal structure and species composition of plant cover differed greatly among grids hydroseeded in 1978 (Supple-mentary Food, Repellent, Stripping Trial, and Control study areas) and those allowed to revegetate by natural means until hydroseeding in 1980 147 Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1982. The Technical and Research Committee on Reclamation  (Reduced Cover and Combined Treatment study areas). As of 1981, ground cover on the former group of study areas was dense and consisted primarily of a few agronomic grasses and legumes (Table 1). Tree and shrub cover generally was minimal (Table 2). In contrast, ground cover on the latter two study areas (the Reduced Cover and Combined Treatment study areas) was sparse and consisted of a wide variety of native herba-ceous plants, a number of "weeds," agronomic grasses, and some legumes. Tree and shrub cover on these two areas was well developed and included natural introductions of several native species as well as the species planted in 1979. Vertical distribution of plant cover was minimal on the four study areas hydroseeded in 1978; most plant cover was <25 cm tall (Table 3). In contrast, vertical cover on the two naturally-revegetating areas was well developed; a variety of ground cover species were present O cm to 50 cm above ground level and good development of tree and shrub growth accounted for much of the plant cover 50 cm to 150 cm above ground. TREE AND SHRUB PERFORMANCE Based on the tree and shrub assessments during 1980 and 1981, striking differences existed between the growth, condition, and survival of trees and shrubs on the areas with reduced cover and trees and shrubs on areas with dense grass/legume cover (Table 4). Trees and shrubs on the areas with reduced cover were characterized by good growth, good condition and high survival. In contrast, trees and shrubs on the areas hydroseeded in 1978 were characterized by poor to moderate growth, poor to fair condition and moderate survival. DAMAGE Before 1981, there was little damage to trees and shrubs on most study areas. Damage during 1979/80, however, tended to be greatest on the Supplementary Food study area. Damage to seedlings increased sharply during winter 1980/81. At the time of the 1981 assessments, amounts of damage were high on the Supplementary Food study area and moderate on the Repellent, Stripping Trial and Control study areas (Tables 2 and 4). All of these areas had dense ground covers predominated by agronomic grasses and legumes. In contrast, very little damage to trees and shrubs was recorded on either of the two study areas with reduced ground cover. 148 Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1982. The Technical and Research Committee on Reclamation  Table 1. Density and species composition of ground cover on the  study areas during 1981. (Mean percent cover for the 50 sample quadrats on each study area is indicated.)  149Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1982. The Technical and Research Committee on Reclamation   Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1982. The Technical and Research Committee on Reclamation   151 Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1982. The Technical and Research Committee on Reclamation   Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1982. The Technical and Research Committee on Reclamation  Comparisons of the amount of damage to different tree species during 1981 suggested that willows and poplars were most susceptible to damage, whereas white spruce and caragana were almost resistant (Green 1982). Other species such as chokecherry, dogwood, Siberian larch, Scots pine, and Russian olive suffered intermediate amounts of damage. MULTIVARIATE ANALYSES Several multivariate statistical techniques were used to assess relationships between habitat structure, amounts of damage, small rodent abundance, and tree/shrub performance. Initially a factor analysis was used to reduce a large number of habitat variables to a smaller number of independent factors that characterized vegetation cover. Factor analyses were performed on the combined vegetation data for 1980 and 1981 using the BMDP4M program (Dixon and Brown 1979). The factor analysis was performed by a standard method—a principal component analysis followed by Varimax (orthogonal) rotation of those principal components with eigenvalues exceeding 1.0. Biological interpretations of the eight habitat factors are summarized in Table 5. Values of each factor were calculated for each habitat sampling point. These values provide indices of the eight habitat characteristics measured by these factors and used in several multivariate analyses described below. Small Rodent Damage and Habitat Structure Previous studies of small mammal damage to saplings and shrubs have suggested that amounts of damage are related to habitat structure (e.g., density of ground cover, abundance, and diversity of food types, density of trees and shrubs) (e.g., Eadie 1953; Howard 1967; Buckner 1970). In this study, a stepwise multiple discriminant analysis (BMDP7M; Dixon and Brown 1979) was performed to determine which indices of habitat structure and small rodent abundance best distinguished those tree planting blocks with no damage from tree planting blocks with damage. Based on damage estimates obtained during 1980, none of the eight habitat factors or small rodent numbers were significant predictors of damage. In 1981, however, the presence or absence of damage was significantly related to the local abundance of M. pennsylvanicus and to the value of the Agropyron / hawkweed factor. The local abundance of M. pennsylvanicus was the predictor variable that best separated the two categories of damage; tree planting blocks with damage tended to occur 153 Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1982. The Technical and Research Committee on Reclamation   Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1982. The Technical and Research Committee on Reclamation  where M. pennsylvanicus was abundant, whereas tree planting blocks with no damage tended to occur where M. pennsylvanicus was not abundant. Planting blocks with no damage also tended to be located in areas with dense ground covers of A. violacium and hawkweed, whereas planting blocks with damage tended to occur where such ground cover was sparse. High values of the A. violacium / hawkweed factor were recorded on the two study areas with reduced plant cover, so the results show that damage tended to be least on those study areas. The discriminant model accurately predicted the damage category in 65.8% of the 120 tree planting blocks. Small Rodent Abundance and Habitat Structure Relationships between small rodent abundance and habitat structure also indicated that ground cover communities strongly influenced the local abundance of M. pennsylvanicus. Stepwise multiple regression (SMR) analyses of the relationship between habitat structure and small rodent abundance were performed using the BMDP2R program (Dixon and Brown 1979). Four separate SMR analyses were performed; two for M. pennsyl-vanicus in 1980 and 1981, and two for P. maniculatus in 1980 and 1981. Only habitat factors with P-ratios larger than 4.0 were allowed to enter the SMR model. During 1980, three habitat factors explained 42.5% of the spatial variation in the abundance of M. pennsylvanicus on the six study areas (Table 6). The grass/legume factor was the most important predictor variable and was positively associated with numbers of M, pennsyl-vanicus. The sanfoin factor and the common clover factor were both positively associated with the abundance of M. pennsylvanicus and accounted for an additional 2.8% and 2.6% of the variance in captures, respectively. The relationship between spatial variation in the abundance of M. pennsylvanicus and vegetation structure in 1981 was similar to that in 1980. Three habitat factors, the grass/legume, the crested wheatgrass, and the common clover factors, accounted for 38.8% of the spatial vari-ation in M. pennsylvanicus (Table 6). The grass/legume factor and the common clover factor were positively associated with abundance whereas the crested wheatgrass was negatively associated with numbers of M. pennsylvanicus. 155 Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1982. The Technical and Research Committee on Reclamation   Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1982. The Technical and Research Committee on Reclamation  Multiple regression analyses for P. maniculatus indicated that local variation in the abundance of this species during both years was poorly associated with all of the habitat variables measured. Tree and Shrub Performance and Habitat Structure Total height, survival, and condition for each of 12 tree and shrub species were evaluated by Suncor on each study area. We wanted to reduce these 36 values (3 variables x 12 species) to just a few indices of height, survival, and condition. To do this, three separate princi-pal component analyses (BMDP4M; Dixon and Brown 1979) were performed on the Suncor estimates of growth, survival, and condition, respectively. The first two principal components of growth, the first principal component of condition, and the first principal component of survival were used in all further analyses as indices of the respective param-eters. Seven habitat factors, similar to those described in Table 5, were used to describe plant cover on the five study areas (the Stripping Trial was excluded from the analyses because the tree planting blocks on this area were not identical to the other five areas). Three separate stepwise multiple regression analyses (BMDP2R; Dixon and Brown 1979) then were used to assess relationships between growth, condition, and survival, respectively, and the factors describing vegetation cover and small rodent abundance. Results of the analyses are summarized in Table 7; further details are provided by Green (1982). During 1980, when amounts of damage to trees and shrubs were small, tree and shrub performance was related to the density and composition of ground cover. Trees and shrubs in better condition tended to be taller than plants in poor condition. Trees and shrubs that were located in areas with ground covers dominated by F. saximontana and Lamb's quarters (i.e., the Reduced Cover and Combined Treatment study areas) or with high local abundances of P. maniculatus (again the two reduced cover study areas) also tended to be taller. This suggests that during 1980, sparse ground covers such as those present in the Reduced Cover and Combined Treatment study areas were most suitable for tree and shrub growth. In contrast, tree and shrub growth in areas dominated by a dense cover of agronomic grasses and legumes tended to be poor. Tree and shrub condition during 1980 was negatively associated with the local abundance of M. pennsylvanicus and the density of grass/legume cover. Because damage was included in the analysis but was not a 157 Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1982. The Technical and Research Committee on Reclamation   158 Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1982. The Technical and Research Committee on Reclamation   159 Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1982. The Technical and Research Committee on Reclamation  significant predictor variable of condition, the negative association between condition and M. pennsylvanicus numbers probably reflects habitat conditions that supported high numbers of these species (dense horizontal and vertical ground cover dominated by agronomic grasses and alfalfa, common clover, and sanfoin). During 1981, tree and shrub height again appeared to be negatively related to ground cover. Height of coniferous trees and most shrubs was positively associated with tree/shrub condition. In turn, tree/shrub condition was negatively influenced by increasing densities of ground cover dominated by agronomic grasses and legumes. Height of willows and poplars was negatively associated with damage or, in other words, height was negatively affected by damage. Because damage tended to be highest in areas preferred by M. pennsylvanicus, growth of poplars and willows, by inference, was poorer in areas with a dense ground cover of agronomic grasses and legumes. The close association between low tree/shrub survival and a dense ground cover of agronomic grasses and legumes and between good tree and shrub survival and habitat parameters typical of the sparse ground covers on the two reduced cover study areas (i.e., a ground cover predominated by Lamb's quarters, F. saximontana, A. violacium, and hawkweed, a high local abundance of P. maniculatus, and good vertical development of vegetation cover 25 cm to 150 cm above ground level) are in direct agreement with this conclusion. In summary, the results of the three multivariate analyses during 1980 and 1981 generally are in agreement and suggest: 1. Dense ground covers predominated by agronomic grasses (creep- ing red fescue, brome grass, and crested wheatgrass) and legumes (alfalfa and common clover) seriously hinder tree and shrub performance (e.g., poor growth, condition, and sur- vival) ; and 2. Sparse herbaceous ground covers, such as that present on the Reduced Cover and Combined Treatment study areas, appear to be the most suitable vegetation cover for good tree and shrub performance (good growth, condition, and survival). SYNTHESIS AND CONCLUSIONS Based on this study and previous research by Radvanyi (1978), Michielsen and Radvanyi (1979), and Green (198Oa, 198Oc), a number of conclusions 160 Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1982. The Technical and Research Committee on Reclamation  concerning small rodent damage to trees and shrubs on reclamation areas and the performance of tree and shrub species on reclamation areas can be stated (characteristics of small rodent populations, vegetation, tree performance, and small rodent damage on each study area are summarized in Table 8). 1. The grass/legume ground cover used to stabilize tailing sand berms creates a vegetation community highly suitable to M. pennsylvanicus. 2. Once established in new reclamation sites, M. pennsylvanicus populations can increase rapidly and undergo cyclic fluctu- ations in abundance on the order of once every three to four years. 3. New reclamation sites are only moderately suitable for P. maniculatus and are poorly suited to C. gapperi (these two species of small rodent are the most abundant species in adjacent natural forested communities). 4. High local abundances of M. pennsylvanicus are closely associ- ated with development of dense grass and legume ground cover. 5. Damage to trees and shrubs tends to be most severe in areas with a high local abundance of M. pennsylvanicus, strongly suggesting that this species is largely responsible for the girdling damage on reclamation areas. 6. Assuming this relationship is correct, local abundances of M. pennsylvanicus appear to be the proximate cause of damage, whereas the development of dense vegetation cover dominated by agronomic grasses and legumes is the ultimate cause of damage. 7. Development of dense ground covers of grass and legumes can result in reduced tree and shrub performance (poor growth, condition and survival), possibly as a result of competition for nutrients and water. In addition to providing information on these aspects of small rodent demography, small rodent damage, vegetation cover, and tree/shrub performance, this study has provided an opportunity to observe the 161 Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1982. The Technical and Research Committee on Reclamation   Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1982. The Technical and Research Committee on Reclamation  establishment of two types of ground cover communities in reclamation areas—agronomic grass and legume ground cover and a natural succes-sional ground cover—and the subsequent use of these areas by small rodents. At the start of this study (summer 1978), no plant cover was present on any of the six study areas and it is likely that all areas were un-inhabited by small rodents. Following hydroseeding of four of the six study areas and the subsequent establishment of sparse grass and legume cover, small rodents had begun to utilize the hydroseeded areas by the early fall 1978. In adjacent natural forest communities C. gapperi is the most abundant species of small rodent, P. maniculatus is moderately abundant, and M. pennsylvanicus is only common within pockets of suitable vegetation (Green 1980c). However, the creation of reclamation areas with good development of grass and legume cover has provided a large area of habitat, highly suitable for habitation by M. pennsylvanicus and, to a lesser extent, P. maniculatus. It appears, then, that the creation of grass and legume-dominated reclamation areas has allowed M. pennsylvani-cus to establish large resident, breeding populations in an area that formerly was not well suited for this species. These populations increased rapidly and now appear to undergo cyclic fluctuations in number (as described by Krebs and Myers [1974]) on the order of once every three to four years. In contrast, C. gapperi has not become well established in reclamation sites even though it is abundant in adjacent forested sites. Because C. gapperi prefers mature forested communities, failure of this species to establish on the existing reclamation sites is not unexpected. However, as tree and shrub cover increases on the reclamation sites, increased use of these areas by C. gapperi can be expected. The reclamation study areas appear to provide an adequate habitat for P. maniculatus; breeding populations have become established and numbers are similar to those in some adjacent forested areas. Peromyscus maniculatus prefers natural areas with well-developed tree and shrub cover and will likely increase in number as trees and shrubs become better established on the reclamation sites. 163 Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1982. The Technical and Research Committee on Reclamation  Reclamation practices, currently in use in the Fort McMurray area generally involve hydroseeding with a mix of a soil stabilizer, agro-nomic grasses and legumes. This results in the rapid establishment of a vegetation mat that reduces soil erosion. Tree and shrub planting programs have been undertaken in order to accelerate the establishment of a self-sustaining vegetation community and to aid in soil stabiliza-tion. Results of this study indicate, however, that the dense ground covers and tree planting programs are not compatible for two major reasons. First, the dense grass and legume ground covers probably compete with the young trees and shrubs for water and nutrients. The poor growth, condition, and survival of trees and shrubs in areas of dense ground cover suggests that the grass and legume species used are capable of reducing tree and shrub performance. Trees and shrubs stressed by competition would be less able to withstand the additional stress of small rodent damage and consequently would be more susceptible to damage. And second, the development of dense grass and legume cover creates a vegetation community highly suitable for M. pennsylvanicus. Girdling damage by M. pennsylvanicus can reach high levels during the peak phase of this small rodent's population cycle. Because trees and shrubs in areas of dense grass and legume cover may already be stressed by competition and because the same ground cover ultimately results in increased amounts of damage (as a result of high M. pennsylvanicus numbers), poor tree and shrub performance can be anticipated. Because stabilization of the tailings sand berms is necessary to reduce erosion by wind and water, the use of ground covers cannot be totally eliminated. Some form of ground cover and/or soil stabilizer is necessary. Widespread use of an artificial soil stabilizer, such as hydromulch, is not feasible because of the large size of the reclamation areas. The solution appears to be the development of a seed mix which will result in a ground cover community with several characteristics: 1. a well-developed root system to help stabilize the tailings sand; 2. a poor capability to compete with trees and shrubs for water and nutrients; 164 Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1982. The Technical and Research Committee on Reclamation  3. a minimal development of above-ground plant cover to reduce the attractiveness to M. pennsylvanicus; and 4. a reproductive capability sufficient to maintain a self- sustaining vegetation community. Several species of grasses, which may meet these criteria, are currently being tested on the Reduced Cover and Combined Treatment study areas. Tree and shrub survival might also be enhanced through timing of the reclamation program. For example, trees and shrubs might first be planted on reclamation sites and allowed to establish prior to the application of a sparse ground cover mix. In addition, because M. pennsylvanicus populations appear to reach high numbers only once every three to four years and because damage can be expected to increase to critical levels during these peak, years, trees and shrubs should be planted immediately following the population decline. The trees and shrubs consequently would have two to three complete growing seasons before the next population peak of M. pennsylvanicus and likely would be better able to withstand the stress of girdling damage. 165 Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1982. The Technical and Research Committee on Reclamation  REFERENCES CITED Buckner, C.H. 1970. The strategy for controlling rodent damage to pines in the Canadian mid-west. Proc. Vert. Pest. Conf. 4:43-48. Chitty, D. and E. Phipps. 1966. Seasonal changes in survival in mixed populations of two species of vole. J. Anim. Ecol. 35:313-331. Dixon, W.J. and M.B. Brown, eds. 1979. BMDP-79. Biomedical computer programs P-series. Univ. of Calif. Press, Berkeley. 880 pp. Eadie, W.R. 1953. Responses of Microtus to vegetative cover. J. Mammal. 34:263-264. Fedkenheuer, A.W. 1979. Native shrub research for oil sands reclama-tion. Professional paper 1979-4, Syncrude Canada Ltd. 14 pp. Green, J.E. 1978. Techniques for the control of small mammal damage to plants: a review. Prep, for the Alberta Oil Sands Environmental Research Program by LGL Ltd., environmental research associates. AOSERP Report 38. 111 pp. Green, J.E. 1980a. Small mammal populations of northeastern Alberta. II. Populations in reclamation areas. Prep, for the Alberta Oil Sands Environmental Research Program by LGL Ltd., environmental research associates. AOSERP Report 108. 136 pp. Green, J.E. 1980b. Small rodent populations and related damage to trees and shrubs on reclamation areas. 1980 Field Studies Interim Report. Prep, for Suncor Inc. and Alsands Energy Ltd. by LGL Ltd., environmental research associates. 56 pp. Green, J.E. 1980c. Small mammal populations of northeastern Alberta. I. Populations in natural habitats. Prep, for the Alberta Oil Sands Environmental Research Program by LGL Ltd., environmental research associates. AOSERP Report 107. 301 pp. Green, J.E. 1982. Small rodent populations and related damage to trees and shrubs on reclamation areas. Prep, for Alsands Energy Ltd. and Suncor Inc. by LGL Ltd., environmental research associates. 121 pp. 166 Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1982. The Technical and Research Committee on Reclamation  Howard, W.E. 1967. Biocontrol and chemosterHants. Pages 343-386 in W.W. Kilgore and R.L. Doutt, eds. Pest control: biological, physical and selected chemical methods. Academic Press, New York. Kershaw, K.A. 1966. Quantitative and dynamic ecology. Edward Arnold Publ. Limited, London. 183 pp. Krebs, C.J., B.L. Keller, and R.H. Tamarin. 1969. Microtus population biology: demographic changes in fluctuating populations of M. ochrogaster and M. pennsylvanicus in southern Indiana. Ecology 50:587-607. Krebs, C.J. and J.H. Myers. 1974. Population cycles in small mammals. Adv. in Ecol. Res. 8:267-399. Michielsen, J. and A. Radvanyi. 1979. Great Canadian Oil Sands small mammal study. Final report. Prep, for Great Canadian Oil Sands Limited. 65 pp. Nudds, T.D. 1977. Quantifying the vegetative structure of wildlife cover. Wildl. Soc. Bull. 5:113-117. Radvanyi, A. 1978. The return of the rodents—year three in the assessment of harmful small mammals in the Alberta oil sands reclamation and afforestation program. Final report. Fisheries and Environment Canada, Can. Wildl. Serv. 82 pp. Seiner, J. and R. Thompson. 1977. Reclamation for afforestation by suitable native and introduced tree and shrub species. Prep, for the Alberta Oil Sands Environmental Research Program by the Alberta Forest Service, Lands Use Branch, Sub-project VE 7.1. 93 pp. Sherstabetoff, J., G.B. Dunsworth, and S.K. Takyi. 1978. An interim report on reclamation afforestation by suitable native and intro-duced tree species. Prep, for the Alberta Oil Sands nvironmental Research Program by the Alberta Forest Service. AOSERP Report 41. 115 pp. Shopik, T.D. 1980. 1979 Afforestation Report. Suncor Inc. Oil Sands Division. Environmental Affairs. 1980-02-05. 17 pp. + appen-dices. 167 Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1982. The Technical and Research Committee on Reclamation  ACKNOWLEDGEMENTS A number of individuals contributed much to the study throughout 1978 to 1981. In particular, I would like to thank Vance Buchwald, Hazel Hurtak, Kathy Bruce, and Brian Braidwood for their contributions to the field study, data analyses and report preparation. I also would like to thank D. Whitford for key punching of the field data and preparation of the typescript; K. English and B. Harvie for assistance in computer analyses; and D. Dabbs, J. Richardson, and T. Shopik for their review of an earlier version of this paper. I also would like to thank D. Klym (Land Environment Manager, Suncor Inc.) and D. Dabbs (Alsands Energy Ltd.) for their support and assis-tance and T. Shopik (Lands System, Suncor Inc.) for provision of the tree and shrub assessment data for 1980 and 1981. Funding of this program was provided by the Alberta Oil Sands Environ-mental Research Program during 1978 and 1979 and by Alsands Energy Ltd. and Suncor Inc. during 1980 and 1981. 168 Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1982. The Technical and Research Committee on Reclamation  DISCUSSION RELATING TO JEFF GREEN'S PAPER Frank Pells, Brenda Mines: Is the cycle of mice independent of your planting cycle? Answer: It could be coincidental and I really can't answer your question. We started our study in 1978 and unfortunately that was the year that the microtene populations declined very rapidly on the older reclamation sites that had already been established. It's interesting that Al Kennedy, when speaking about the Esso Project at Judy Creek yesterday said that they also had high population numbers for 1981 and high amounts of damage. One of the things that has been suggested, for natural populations anyways, is that these populations cycle circuitously across very wide geo-graphical regions so perhaps it doesn't really matter when you start your areas - you still may have cycling populations which could be influenced by immigration of animals from older reclama-tion sites. When the numbers go up there, you're probably going to get very high influx into your reclamation sites. Phil Burton, Monenco Consultants: Jeff, would you say that rodent damaged is associated more with high shoot cover of the ground (grasses and legumes) or with litter accumulation? Answer: Our analysis couldn't distinguish that - I think both are important. Basically they both add to the ground cover which protects the small rodents from predation and climatic extremes. Rodents definitely go for areas of very high ground cover accumula-tion. They need to have some green shoot material for food, but they also like to have a lot of plant accumulation for nesting, and building runways. Jack Thirgood, U.B.C.:  How do you apply the grass turf in strips? Answer: One of the treatments which I didn't go into very much is called the stripping trial. What we did was to seed a ten metre wide horizontal band at the top of the berm and another ten metre band across the bottom, leaving a band which varied between 20 m and 25 m wide in the middle which was unseeded. Then trees were 169 Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1982. The Technical and Research Committee on Reclamation  planted into that. The trees have done somewhat better, but one of the problems we face with working on a slope is water washing grass seed down into the area so that it begins to seed over like the other areas. Jack Thirgood, U.B.C.: I hope not (interval of unclear recording). Have you tried removing the turf? Answer: We haven't tried that. Prior to our study Suncor did try a manipulation in which they would clear off one and a half metre radius and plant the trees into that. The area wasn't big enough and the grass came back very quickly. An alternative reclamation strategy might be to do something like we've done on our two reduced-cover plots in which you plant your trees first and use physical means of controlling erosion be it through soil stabiliz-ers or sand-bagging or whatever. It's fairly labour intensive. But get the trees well established, let the roots get going, then plant your sparse shrubbery. Jack Thirgood, U.B.C.: Could you plant the trees and then use a herbi-cide? Answer: That would probably be a very acceptable technique. Dave Fraser, University of Victoria: Did anybody try habitat manipula-tion to increase prédation pressure? Answer: One of the problems with that technique is that predators only remove excess of microtene populations. Predators can keep that peak population down, but in natural situations they can't stop the cycling. I suspect that prédation might reduce the population but it isn't going to be as effective as habitat manipulation which can result in very large changes in population numbers. Dave Fraser, University of Victoria: How about leaving islands of natural vegetation to relieve pressure on reclaimed areas? 170 Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1982. The Technical and Research Committee on Reclamation  Answer: Yes, and that would also be one route of investigation into making these reclamation sites more suitable for other types of wildlife species as well. C.J. Lloyd, U.B.C.: (Distorted recording. The question related to selecting damage resistant species for planting.) Answer: Among the tree species we planted there is a definite prefer-ence for white spruce and caragana. There are clearly certain species which they leave strictly alone. 171 

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