This file was created by scanning the printed publication. Errors identified by the software have been corrected; however, some errors may remain.

Responses of Small to Forest Riparian Perturbations1

2 Stephen P. Cross

Abstract.--Trapping studies at several mixed conifer forest sites in southwestern Oregon demonstrate a differentially high use of riparian habitat by small mammals. Harsh perturbations of this habitat radically affect the presence and abundance of many species. Riparian leave-strips were found to support small- communities comparable to undisturbed sites.

INTRODUCTION on some small-mammal species (Gashwiler 1970, Black and Hooven 1974, Hooven and Black 1976, Riparian areas have been identified as Campbell and Clark 1980). But little attention extremely important habitat for wildlife (Johnson has been given to comparing the effects of such and Jones 1977, Thomas et al. 1979). Much of the perturbations on wildlife such as small mammals of supporting data for this contention comes from different forest vegetational zones. Leaving a studies in arid regions where the riparian strip (buffer) of riparian and transition zone vegetation contrasts sharply with other types and vegetation along the edges of streams when the is the only local source of some essential habitat surrounding area is logged is a forest management components such as trees and free water. The practice used in some areas. There are many riparian zone in more mesic regions, although potential benefits to this practice but the recognizable, does not contrast as sharply with effects on resident wildlife populations of the nearby habitats. Trees are not so limited in streamside leave-strip are not known. distribution and free water is generally more widely available and in less demand by wildlife. The studies reported here were designed to Considering these conditions, it is appropriate to make quantitative comparisons of the small-mammal ask if there is disproportionately high use of the use of various forest vegetation zones associated riparian zone by wildlife in mesic regions. with streams. A related objective was to assess the impact of harsh forest perturbations and Natural history information suggests that riparian leave-strips on the resident small-mammal more wildlife species potentially use forest communities. riparian habitat than other nearby habitats. But quantitative assessments of species diversity and abundance are necessary to verify the predicted GENERAL STUDY AREA AND METHODS differential or disproportionate use. The studies were conducted at four sites in Streamside forest riparian vegetation is southwestern Oregon in the mixed-conifer usually distinct from nearby upland vegetation vegetation zone (Franklin and Dyrness 1973). The which is upslope and not under direct influence of study sites were widely separated and varied in the stream. The blending of riparian and upland vegetational composition. vegetation often creates a rather broad and distinctive ecoton~, usually referred to as the Small mammals were collected using three transition zone. This zone is particularly types of traps. Sherman live-traps (9 x 7.5 x important because of its potentially high value 23.5 em) and pitfall traps (5-lb plastic food for timber production, wildlife habitat, and as a container, 18.4-cm deep with 14.6-cm diameter buffer for the riparian zone. opening) were used at all the sites. Museum Special snap traps were used at two of the sites. Clearcutting and other harsh forest Bait consisted of rolled oats for the live-traps perturbations are known to have a profound effect and a mixture of rolled oats and peanut butter for the snap traps. After all traps were in place at 1 a given site there was a 4-5 day waiting period Paper presented at the North American before they were activated. During this period Riparian Conference. [University of Arizona, the pitfall traps were covered with tight fitting Tucson, April 16-18, 1985]. lids and the other traps were prebaited. Once 2 traps were activated they were checked twice Stephen P. Cross is a Professor of Biology, daily, during the 3-4 hours after sunrise and the Department of Biology, Southern Oregon State 2-3 hours before dark. College, Ashland, Oregon.

269 Small mammals trapped alive were identified, The transition zone, located between the sexed and aged when possible, and toe-clipped for riparian and upland zones, includes a distinctive individual identification. Emphasis was placed on combination of vegetative characteristics of the live-trapping to minimize any increase in other two zones. This area is dominated by immigration that might be caused by removal and to Douglas-fir in the canopy to a greater extent than study the influence of streams on local movements. the other zones. There are some western redcedar, bigleaf maple, and grand fir (Abies grandis) also Data from each sample plot were placed in present. Twenty-five species of ground cover were contingency tables and analyzed with the recorded with whipple vine (Whipplea modesta), chi-square statistic. Since small-mammal trapping twinflower (Linnea borealis), mosses, snowberry, is somewhat selective and may not accurately and grasses being the most abundant.. Widths of reflect the true community structure, the the riparian and transition zones are somewhat Brillouin index (log to base 2) was used as a variable depending upon slope and aspect. measure of diversity. Two quantitative values for similarity, the quotient of similarity and percent Small-mammal communities in each of the zones similarity, were used to compare small-mammal were sampled in the following manner. Two-row samples from various habitats or test plots. The belt transects were placed parallel to the stream former takes into account only the presence or in each vegetative zone. Each row consisted of 20 absence of species, whereas the latter also takes stations divided into two separate 10-station into account the relative abundances of the sections. The resulting pattern had 40 stations various species. Derivation and use of the above in each zone in the form of two replicate quantitative measures are described in Brower and 20-s ta tion belt t ran sects. The two rows of each Zar (1984). transect were 12.5-m apart while the distance between stations within a row was 15-m. The two 20-s tation transects within each zone were offset DIFFERENTIAL USE OF RIPARIAN HABITAT - SODA CREEK from those of the other zones to avoid interference. The riparian transect was The specific objective of this study was to positioned so that the two rows of traps were on compare small-mammal abundance, community opposite sides of the stream. This was done in composition, and diversity in a coniferous forest order to stay within the relatively narrow zone of streamside riparian zone with neighboring riparian vegetation and to allow mammals utilizing habitats. this zone equal exposure to both rows of traps, as in the other zones.

Study Site and Methods Two Sherman live-traps and one pitfall trap were placed within 2.5-m of the station marker. The live-traps were placed on opposite s~des of The Soda Creek study site is located in an the station marker and moved roughly 90 after old-growth forest in the foothills of the southern each two days of trapping. The traps were Oregon Cascades, 23-km northeast of Ashland, T37S, activated on 23 June 1981 and remained in R3E, Sections 19 and 20, Willamette Meridian at operation for 10 days (9 nights). Total trap-days ca. 900-m elevation. The creek flows northerly (nights) were identical for each zone. into the south fork of Little Butte Creek, part of the Rogue River drainage. Although relatively small (streambed ca. 5-m), the creek influences Results and Discussion the surrounding vegetation to the extent that three typical zones (i.e. habitats) may be Since the small-mammal samples from the recognized. replicate transects within each of the three habitat zones were not significantly different (p The riparian zone is dominated by Douglas-fir > 0.05) they were combined for further analysis. ( Pseudotsuga menziesii), bigleaf maple (Acer The species captured and the associated measures macrophyllum), white alder (Alnus rhombifol~ of abundance and diversity within each habitat and western redcedar (Thuja pl~) in the canopy zone are shown in table 1. The species and understory. Shrub species in the understory frequencies in the samples from the three zones include hazel (Corylus cornuta), ocean are significantly different (p < 0.001). Pairwise spray (Holodiscus discolor), and ninebark comparisons of the samples indicate that the (Physocarpus capitatus). Thirty species of ground riparian is significantly different from both the cover plants were identified with mosses, bedstraw transition (p < 0.001) and upland (p < 0.001) but (Galium sp.), thimbleberry (Rubus. parviflorus), the transition is not significantly different from snowberry (Symphoricarpos albus), and grasses the upland (p > 0.05). Sample size, an indication occurring most frequently. ----- of abundance, is similar in the riparian and transition zones (106 and 102, respectively), The upland zone has a canopy and understory almost double that of the upland zone (54). also dominated by Douglas-fir with some western redcedar and Pacific madrone (Arbutus menziesii), Species richness is greatest in the sample from the riparian zone, intermediate in the and occ~sional Ponderosa pine (Pinus ponderosa) and Cal~fornia black oak (Quercus kelloggii). transition zone, and lowest in the upland zone. There are very few shrubs present. Twenty-two The computed diversity indices follow the same species of ground cover were identified but most trend. All the species captured in either the ground is devoid of cover. upland or transition habitats are also present in

270 Table 1.--Small-mammal species abundance and DIFFERENTIAL USE AND HARSH PERTURBATION - LOUIS diversity in three habitat zones adjacent to CREEK Soda Creek. The first objective of this study was identical to that described for Soda Creek. Species and Habitat Zone Another objective was to compare the small mammals Summary Riparian Transition Upland from the riparian and upland zones in an old-growth coniferous forest to similar locations in a neighboring clearcut. Deer mouse 23 14 13 California red-backed vole 24 35 18 Study Area and Methods Trowbridge's shrew 25 43 23 Pacific shrew 13 3 0 The Louis Creek study site is located on the Shrew-mole 13 7 0 western flank of the Cascade Mountains, ca. 470-m Jumping mouse 6 0 0 elevation, 17.7-km northeast of Myrtle Creek, Siskiyou 1 0 0 T28S, R3W, sections 29 (forest) and 30 (clearcut), Vole species 1 0 0 Willamette Meridian. Louis Creek flows southeasterly into South Myrtle Creek, part of the Total species 8 5 3 Umpqua River drainage. The creek is quite small Total individuals 106 102 54 (streambed ca. 2-m) and the associated open Diversity (H) 2.39 1. 7 5 1.44 (non-canopied) corridor is also small, but a Evenness (J) .8524 .7976 .9763 riparian zone along the edges of the creek can be recognized. The transition and upland zones are also recognizable although the edges are not as clearly defined as in the more xerically situated the riparian zone sample. Conversely, five of the Soda Creek site. species captured in the riparian zone are absent in the samples from one or both of the other The three vegetation zones may be zones. The riparian zone sample has the highest distinguished on the basis of the combinations of number of individuals for six species while the dominant canopy·and understory. The riparian zone transition zone has the highest number of is characterized by a canopy dominated by western individuals for two species. hemlock (Tsuga heterophylla) with some representation of western redcedar, Pacific yew The quotient of similarity (table 2), based (Taxus brevifolia), and grand fir. The understory only on species composition, indicates that the of this zone is dominated by vine maple (Acer riparian and upland samples are less similar to circinatum) with some Pacific dogwood (Cornus each other than the other combinations. But when nuttallii). A few red alder (Alnus rubra) are the number of each species is also considered, as unique to this zone. The transition zone canopy in percent similarity, the transition and upland is also dominated by western hemlock followed by zones are more similar to one another than the western redcedar, grand fir, and Douglas-fir. The other combinations, which agrees with the understory is again dominated by vine maple but chi-square analysis. also includes California hazel (Corylus cornuta) and western hemlock. A few bigleaf maple occur in These data indicate differential occupancy both the riparian and transition zones. The patterns in the three habitats sampled. The Soda upland zone canopy is dominated by grand fir and Creek riparian zone appears to support a more Douglas-fir with western hemlock scarcely diverse small-mammal fauna than the adjacent represented. The understory is dominated by forested habitats. Most species also occur in incense cedar (Libocedrus decurrens) and saplings greater abundance in this habitat, but a high of Douglas-fir and grand fir. number of two species in the transition zone makes it comparable in total abundance to the riparian Riparian zone ground cover has the highest zone. density and the greatest number of unique species. The upland zone ground cover has lower density and few unique plant species while the transition zone Table 2. --Community comparisons of small mammals has moderate density and virtually no unique in' the three zones adjacent to Soda Creek species. (R = riparian, T = transition, U = upland). A clearcut, located to th~ immediate west of the forest study area was used for another study plot. The site was logged, prepared and replanted Characteristic Habitats Compared during the summer and fall of 1977. It was R x T R x U T x U sprayed with herbicides each year from 1978 through 1981 to reduce competition with conifer seedlings. Total species 8 8 5 Species in both 5 3 3 The trap transect pattern for sampling small Quotient of similarity .769 .545 .750 mammals in the forest was similar to the one used Percent similarity 69.8 67.9 89.2 at Soda Creek. The interstation distance was 10-m between rows and 12-m within each row. Two

271 additional transects, similar in relative location low quotient of similarity (table 4). But when and interstatioP distances to the riparian and the numbers of each species are also considered, upland zones in the forest, were placed in the the two zones show a relatively high percent clearcut. Trapping regimen was identical to Soda similarity, a reflection of the equally high Creek. Trapping began on 18 August and was numbers of three species. completed on 28 August 1981. The frequencies of small mammals in the samples from the ripar·ian zone of the forest and Results and Discussion the clearcut are significantly different (p < 0.001). This is also true for the upland region The frequencies of small mammal captures from of the forest and the clearcut. Species richness the replicalc transects within each of the habitat and other measures of diversity are higher for the zones of both the forest and the clearcut were not forest riparian than in the clearcut riparian signifi,..:::ucly different (p ) 0.05) so those samples. But sample size, an indication of samples were pooled. The capture frequencies, density, is greater in the clearcut. To a lesser total individual captures, and sample diversity degree, this also holds true for the forest and are shown in table 3. Within the forest, the clearcut upland samples but they are comparable in capture frequencies of the samples from the three richness and other measures of diversity. Species habitat zones are significantly different (p < composition within a given zone is quite different 0.001). Also, when the samples from the habitat (tables 3 and 4) in the forest and clearcut zones are compared in a pairwise fashion, they are samples. Only six of 12 species occurred in both significantly different (p < 0.01). riparian zones and only four of 10 occurred in both upland zones. This results in relatively low Sample size indicates that small mammals are quotients of similarity. The percent similarity, somewhat more abundant in the forest riparian zone however, indicates that the respective riparian than in the other two forest zones. Species zones of the forest and clearcut are more similar richness is highest in the riparian and transition to one another than the riparian and upland zone zone samples. The diversity indices grade from of the forest. The composition and frequencies of highest in the riparian to lowest in the upland. species from the upland zone of the forest and The greatest similarity of species occurs between clearcut are very dissimilar~ the riparian and transition zones (table 4). When numbers of each species are also considered, as in Individual species patterns in the three percent similarity, it is evident that the Louis Creek forest habitat zones are similar to riparian and upland zones are the least similar. those observed at Soda Creek. The jumping mouse (Zapus sp.) is almost completely restricted to the Frequencies of small mammals in samples from riparian habitat in both forests. Other species, the two zones of the clearcut are also such as the northern flying (Glaucomys significantly different (p < 0.001). Species sabrinus) and shrew-mole (Neurotrichus gibbsii), richness, abundance, and diversity are highest in show preference tendencies for the conditions the riparian zone sample. Although 10 species found in the riparian zone. The marsh shrew were captured in the clearcut, only five of them ( Sorex bendirii) is represented by only one were found in both zones, producing a relatively capture in the riparian zone at Louis Creek but,

Table 3.--Small-mammal species abundance and diversity in three habitat zones adjacent to Louis Creek.

Species and Forest Clearcut Summary Riparian Transition Upland Riparian Upland

Deer Mouse 18 20 9 56 so California red-backed vole 11 25 31 0 0 Trowbridge's shrew 26 19 33 24 19 Pacific shrew 16 12 6 10 0 Townsend's chipmunk 8 3 11 8 6 Pacific jumping mouse 25 1 0 36 0 Creeping vole 3 3 1 39 37 Northern flying squirrel 3 1 1 0 0 Shrew-mole 1 1 0 0 0 Other (2 species) 1 1 0 0 0 California ground squirrel 0 0 0 5 4 Dusky-footed woodrat 0 0 0 0 8 Other (2 species) 0 0 0 2 1

Total species 10 10 7 8 7 Total individuals 112 86 92 180 125 Diversity (H) 2.60 2.30 1.99 2.39 2.10 Evenness (J) .841 • 7 57 .763 .831 • 7 58

272 Table 4.--Community comparisons of small mammals in the various habitat zones at Louis Creek (R = riparian, T = transition, u = upland, ClC = clearcut, For = forest).

Areas and Habitats Compared

Characteristic Forest Clearcut For x ClC R x T R X U T X U R xU R u

Total species 11 10 10 10 12 10 Species in both 9 7 7 5 6 4 Quotient of similarity .900 .824 .824 .667 .667 .571 Percent similarity 71.3 58.7 7 3.1 73.3 63.9 30.9

based on life history information (Maser et al. EFFECT OF A RIPARIAN LEAVE-STRIP - MIDDLE AND 1981), it is likely to be restricted to that zone. SOURGRASS CREEKS With the exception of one individual of one species, a mole ( Scapanus sp.), all species that The objective of these studies was to assess were sampled in the transition and upland zones the effect of leaving a strip of forest riparian were also sampled in the riparian zones.. This and transition vegetation, when the neighboring finding is important when considering the relative area ls harshly perturbed, on the resident value of the different zones as travel corridors small-mammal community. or permanent living space. Study Area and Methods Clearcutting and the other associated harsh perturbations had some striking affects on the Middle Creek zonally associated small-mammal communities. Some species, such as the deer mouse (Peromyscus The Middle Creek study site is located in the maniculatus) and creeping vole (Microtus oregoni), Klamath Mountains, ca. 12.5-km west of Glendale, appear to be more abundant in both the riparian T31S, R7W, Section 25, Willamette Meridian at ca. and upland zones of the clearcut than in the 457-m elevation. This moderate-sized (streambed forest. The jumping mouse also occur in larger ca. 6-m) creek flows westerly into Cow Creek, part numbers in the riparian zone of the clearcut than of the Umpqua River drainage. in the forest. Some species, such as the California ground squirrel ( The local forest is dominated by Douglas-fir beecheyi), dusky-footed woodrat (Neotoma and grand fir. Oregon ash (Fraxinus latifolia), fuscipes), Townsend's vole (Microtus townsendii), vine maple, and red alder are abundant in the and house mouse (Mus musculus) occur only in the riparian zone. Salal (Gaultheria shallon) is a clearcut samples. Effects on other species, such common groundcover. Since this is a comparison as Townsend's chipmunk ( townsendii) and study of two similarly vegetated sites, a Trowbridge's shrew (Sorex trowbridgii) seem to be description of other distinctive zonal minimal. --- characteristics is unnecessary.

A species very closely tied to the riparian Two plots were used for study. The upstream zone of the forest, the Pacific jumping mouse, was (full-forest) plot is largely undisturbed not lost in the clearcut. Other species, such as old-growth forest with attendant vegetative zones the California red-backed vole (Clethrionomys on the south side of the stream. The north side californicus), northern flying squirrel, of the stream is variously disturbed, with a dirt shrew-mole, and thr~e others that occur in the road running parallel to it about 25-m away. The forest, were not found in the clearcut. The downstream (leave-strip) plot, located Pacific _shrew ( Sorex pacificus), found in all approximately • 5-km to the west, is essentially a three zones of the forest, is only present in the streamside strip or corridor of forest vegetation. riparian zone sample from the clearcut. The north side of the strip is formed by the road described above and the south side is bordered by another road on the edge of a clearcut plantation These findings suggest that the majority of containing ponderosa pine saplings. The major small mammals residing in mixed-conifer difference between the two plots is that the south communities in southwestern Oregon are capable of side of the full-forest plot blends into upland living in the riparian zone. Some species survive forest whereas the south side of the leave-strip even when this zone is harshly perturbed, while plot is an abrupt forest edge bordered by a road others are exterminated or have populations and clearcut. The small-mammal samples from both reduced. Riparian leave-strips or buffers have sites were collected from the south side of the been suggested as a means of mitigating losses and creek in the riparian and transition vegetation providing connections between forest habitat zones. The average width of the leave-s trip on islands. the south side of the experimental site is 67-m.

273 Two parallel rows of 20 stations, with 10-m Table 5 .--Small-mammal abundance, diversity, and spacing, were placed 5-m and 15-m, respectively, similarity in full-forest and leave-strip from the south edge of the creek in each plot. plots at Middle Creek. One live-trap, one snap trap, and one pitfall trap partially filled with water were placed within 2.5-m of each station marker. Traps were tended Species Full-forest Leave-strip for ten consecutive days, 7-16 July 1980.

Deer mouse 6 13 Sourgrass Creek California red-backed vole 6 5 Trowbridge's shrew 18 12 Sourgrass Creek is located in the Klamath Siskiyou chipmunk 11 8 Mountains, approximately 12. 9-km west of Galice. Jumping mouse 6 2 It is a relatively small (streambed ca. 3-m) Pacific shrew 4 1 stream which flows into Silver Creek, a tributary Northern flying squirrel 1 0 Long-tailed vole 1 of the Illinois River. The study sites w~re 0 located in T35S, R9W, sections 2 and 3, Willamette Bushy-tailed woodrat 0 2 Meridian at ca. 1050-m elevation. Shrew-mole 0 1

Vegetatively, the general area is dominated Total species 8 8 by Douglas-fir and western hemlock in the Total individuals 53 44 overstory and Port-Orford-cedar (Chamaecyparis Diversity (H) 2.27 2.16 lawsoniana) and grand fir in the understory. Evenness (J) .853 .827 Western azalea (Rhododendron occidentale) and salal are common ground cover. The riparian zone Species in both 6 is narrow but distinguishable by some unique Quotient of similarity • 7 50 vegetation, including red alder in the understory. Percent similarity 74.9 The vegetation was judged to be similar in the various study plots. for the two plots and the community similarity Four streamside plots were used for study. indices are high. Two species are unique to the These plots are designated A to D from upstream to samples from each plot, but sample sizes for these downstream. Plots A and D were in relatively four species are low. The jumping mouse, Pacific undisturbed forest. Plots B and C were streamside shrew, and shrew-mole, species closely tied to the leave-strips resulting from recent (one year old) riparian zone, were found in the leave-strip. The clearcuts on one side of the creek and a road and California red-backed vole, an apparent forest partial cutting on the other. Plot B had obligate, was also found in the forest leave-strips approximately 9-m wide on the leave-strip. The northern flying squirrel, clearcut side and slightly larger and more another forest obligate, was not found in the variable on the road side. Plot C had a leave-strip. This may be because of inadequate leave-strip approximately 12-m wide on the sampling (only one was caught in the full-forest clearcut side and variably about 20-m wide on the area) or lack of minimum area for home range. road side. These leave-s trips form corridors of forest vegetation between relatively undisturbed Sourgrass Creek yielded similar results. areas. Since the species frequencies of small mammals captured within the two full-forest plots (A and To sample each of these plots two parallel D) and within the two leave-strip plots (B and C) rows of 10 stations were placed on opposite sides were not significantly different (p ) 0.05) each of the creek. The stations within a row were 10-m type was combined (table 6) for further analysis. apart and each station was 2.5-m from the edge of Capture frequencies in the full-forested and leave the creek. In most instances the stations were strip plots are not significantly different ( p > within or next to the riparian zone. One 0.05). Measures of diversity and community live-trap, one snap trap, and one pitfall, similarity also show the two types of plots to be partially filled wj. th water, were placed within very similar. Of interest is the maintenance of 2-m of each station marker. The traps were tended the high numbers of California red-backed voles, a for 10 consecutive days, 7-16 October 1980, and forest obligate, in the leave-strips. the pitfall traps were left in place for an additional five days. Although the Middle Creek and Sourgrass Creek sites differ in location, size of stream and associated riparian zone, and size of leave Results and Discussion strips, they yielded similar results. It appears that many small-mammal species are able to utilize Frequencies of small mammals in the samples forest riparian leave-strips to the extent that from the Middle Creek full forest and streamside their composition and abundance are maintained at leave-strip plots were not significantly different normal levels. However, much remains to be (p > 0.05). Examination of table 5 indicates learned about the effects of variations in such that sample size, an indication of abundance, is vegetation strips. Size, both length and width, slightly lower in the leave-strip plot but that and degree of connectivity with similar habitat species composition is very similar in the two are variables that undoubtedly affect some plots. Species richness and diversity are similar species.

274 Table 6.--Small-mammal abundance, diversity, and resident and transient wildlife remains to be similarity in full-forest and leave-strip determined. plots at Sourgrass Creek.

ACKNOWLEDGEMENTS Species Full-forest Leave-strip This project was supported by the Bureau of Land Management, Oregon State Office. Bureau Deer mouse 10 12 personnel participating directly in the study California red-backed vole 32 36 included Dave Montgomery, Joe Lint, Cliff Oakley, Trowbridge's shrew 18 20 and especially Jerry Mires and Joe Witt. Bill Pacific shrew 4 4 Neitro provided direction and support throughout Creeping vole 0 2 the study. Student field assistants included Siskiyou chipmunk 0 Scott Peets, Jeff Henry, Dianne Seymour, Joe Shrew-mole 0 Beech, and Les Mayer. Claire Farrell, Russell Davis, and Bill Gaud, who also aided with the Total species 6 5 statistics, reviewed drafts of the manuscript. Total individuals 66 74 Diversity (H) 1.69 1.67 Evenness (J) • 712 .773 LITERATURE CITED

Species in both 4 Black, J. C., and E. F. Hooven. 1974. Response Quotient of simi~arity .727 of small-mammal communities to habitat Percent similarity 96.1 changes in western Oregon. p. 177-186. In H. C. Black, ed. Wildlife and reforestation in the Pacific Northwest. 236 p. School of Forestry, Oregon State University, Corvallis, DISCUSSION AND CONCLUSIONS Oreg. Brower, J. E., and J. H. Zar. 1984. Field and Streamside riparian zones of low to laboratory methods for general ecology. 266 mid-elevation mixed-conifer forests of p. Wm. C. Brown Co., Dubuque, Iowa. southwestern Oregon are inhabited by small-mammal Campbell, T. M., and T. W. Clark. 1980. communi ties that are more diverse and generally Short-term effects of logging on red-backed more dense than in neighboring habitats. The voles and deer mice. Gr. Basin Nat. riparian habitat contains virtually all the 40(2):183-189. small-mammal species that are present in the Franklin, J. F., and C. T. Dyrness. 1973. neighboring transition and upland zones, but the Natural vegetation of Oregon and Washington. reverse situation is not true. A streamside USDA For. Serv., Gen. Tech. Rep. PNW-8 •. 417 vegetative leave-strip appears to maintain p. Pac. Northwest For. and Range Exp. Stn., riparian communi ties of small mammals at levels Portland, Oreg. comparable to nearby undisturbed areas. Gashwiler, J. S. 1970. Plant and mammal changes on a clearcut in western Oregon. Ecology. Forest riparian corridors have been suggested 51:1018-1026. as a means of linking forest habitat islands such Harris, L. D. 1984. The fragmented as old-growth Douglas-fir (Harris 1984). Evidence forest--Island biogeography theory and the from this study indicates that such a management preservation of biotic diversity. 211 p. strategy might serve small mammals very well. But Univ. Chicago Press, Chicago, Ill. terrestrial small mammals are relatively sedentary Hooven, E. F., and H. C. Black. 1976. Effects of compared to other wildlife, and it is likely that some clear-cutting practices on small-mammal larger leave-strips might be required to satisfy populations in western Oregon. Northwest the requirements of permanent living space for Sci. 50(4):189-208. more vagile species. Nevertheless, judging by Johnson, R. R., and D. A. Jones, tech. coord. these small-mammal studies, even small 1977. Importance, preservation, and leave-strips that include riparian habitat have management of riparian habitat: A symposium. greater potential •tor serving as travel or [Tucson, Ariz., July 9, 1977.] USDA For. dispersal corridors between larger habitat islands Serv., Gen. Tech. Rep. RM-43, 217 p. Rocky than leave-s trips in other zones. This is Mt. For. and Range Exp. Stn .. , Fort Collins, certainly not unexpected since the riparian zone Colo. is more environmentally diverse and can, Maser, C., B. R. Mate, J. F. Franklin, and C. T. hypothetically, provide habitat requirements for a Dyrness. 1981. Natural history of Oregon greater variety of wildlife than other forest coast mammals. USDA For. Serv., Gen. Tech. habitats. The fact that streamside leave-s trips Rep. PNW-133, 496p. US Print. Off. maintain populations of several types of small Washington, D.C. mammals indicates that a variety of food niches Thomas, J. W., C. Maser, and J. E. Rodiek. 1979. are also maintained. The small mammals themselves Riparian zones. Pp. 40-47. In J. W. Thomas, may serve as food for larger predatory wildlife ed. Wildlife habitats in managed that use the strip for travel from one large forests--The Blue Mountains of Oregon and habitat area to another. Optimum or minimum size Washington. USDA For. Serv., Agric. Hndbk. of streamside leave-strips that are self­ No. 553. US Print. Off. Washington, D.C. maintaining and can provide habitat for both

275