Terrestrial Gastropods As Focal Species for Monitoring the Ecological

Terrestrial gastropods as focal species for monitoring ecological effects of variable-retention logging practices, 2006 field season

Annual report

Prepared by Kristiina Ovaska and Lennart Sopuck Biolinx Environmental Research Ltd. 1759 Colburne Place, Sidney, BC V8L 5A2

Prepared for Western Forest Products 118-1334 Island Highway, Campbell River, B.C.

March 2007 i

ACKNOWLEDGMENTS

This project was funded by the Forest Science Program of the BC Ministry of Forests and Cascadia Forest Products (now Western Forest Products). We thank Bill Beese of Western Forest Products for his support and cooperation during this study. We also appreciate the support of Jeff Sandford in providing maps and other supplies for the field. We also thank the staff of Port McNeill Timberlands and Queen Charlotte Islands Forest Operation for facilitating our activities in the field. Luke Hyatt, Miray Campbell, Laura Matthias, and Alix Link participated in gastropod surveys. Laura Matthias also helped analyze litter samples in the lab.

Frontispiece: (Left) Inspecting an artificial cover-object for gastropods in the clearcut treatment at the Hoodoo experimental site, Queen Charlotte Islands; (Right) Port McNeill experimental site on northern Vancouver Island showing a “large-group” variable-retention treatment.

EXECUTIVE SUMMARY Terrestrial gastropods (slugs and land snails) were selected as a focal group for examining the effects of variable-retention (VR) logging practices on forest ecosystems within the Adaptive Management Program of Western Forest Products (formerly Weyerhaeuser Company Limited). From 2001 to 2003, we conducted pre-disturbance surveys in uncut forest at six experimental sites. All sites consisted of an uncut control area, clearcut, and three VR-treatment areas, which we sampled for gastropods using artificial cover-objects and by extracting small snails (adult shell diameter less than 5 mm) from samples of forest litter; the two methods provide parallel but independent measures of abundance. Post-disturbance surveys were conducted at two of these sites in 2005 (Tsitika R917; Horseshoe Lake R949; Ovaska and Sopuck 2006). This report presents results of post-logging surveys during the 2006 field season at two additional experimental sites (Port McNeill R817; Hoodoo R1000) and includes comparisons with pre-disturbance data.

The Port McNeill site is located in naturally regenerated older second-growth forest on northern Vancouver Island. The VR-treatments consisted of retention of trees within the logged matrix in large groups of about 0.8 ha, in small groups of about 0.25 ha, and in very small groups, here referred to as dispersed retention; the retention level was 15% in each treatment. We detected 14 species of gastropods at this site. Three of 8 species tested, and all small snails as a group, showed significant treatment effects in comparisons of pre- and post-logging data of relative abundance, based on sampling with artificial cover-objects. These species were Pristiloma species, Striatura pugetensis, and Vespericola columbianus. The treatment effect for a fourth species, Planigyra clappi, approached statistical significance. The clearcut consistently supported a lower abundance of these sensitive species than did the VR-treatments and the control, with the exception of V. columbianus, a habitat generalist, which responded positively to clearcutting. Of the VR-treatments, large groups supported more snails (Pristiloma species and small snails as a group) than did the other VR- treatments but were not equivalent to uncut forest. In this forest type, the small VR- groups suffered from drying out as a result of increased exposure to wind and sun and supported relatively few snails. Species diversity measures derived from artificial cover- object data showed no statistically significant treatment effects attributable to logging, but diversity was somewhat depressed in the VR-dispersed and VR-small group treatments.

At the Port McNeill site, the overall abundance of small snails in litter samples had decreased from an average of 7.5 snails/liter in 2002 to 5.6 snails/liter in 2006. The reduced abundance was largely due to logging, possibly exacerbated by dry conditions in the summer and early fall of 2006. The treatment effect was significant for all five species tested individually (Planigyra clappi, Pristiloma species, Punctum randolphii, Striatura pugetensis, Vertigo species) and for all small snails combined. The clearcut consistently supported lower abundance of these species than did the VR-treatments and the control, with the exception of Vertigo species, which had increased in the

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clearcut relative to the other treatments. Similar to artificial cover-object data, small VR- groups supported lower densities of some species than did the other VR-treatments.

The Hoodoo site is located in naturally regenerated mature second-growth forest interspersed with old growth on Graham Island, Queen Charlotte Islands. The VR- treatments consisted of the retention of trees within the logged matrix in groups of about 0.25 ha at three different retention levels: 10%, 20%, and 30%. We detected 14 species of gastropods at this site. Overall, the abundance of slugs and large snails was very low in 2006 when compared to 2002, possibly due to dry weather in the summer and early fall of 2006. Two of 8 species of gastropods tested showed significant treatment effects in comparisons of pre- and post-logging data of relative abundance, based on sampling with artificial cover-objects: Pristiloma species and Vespericola columbianus. In addition, small snails as a group showed a significant treatment effect. For Pristiloma species and for small snails as a group, abundance was reduced in the clearcut treatment and highest in the control. There were no consistent differences among the three VR-treatments. Vespericola columbianus showed a curious pattern with a steep decline in abundance in the VR-treatment with 20% retention; this effect appears to be spurious. Species diversity measures derived from artificial cover-object data showed no treatment effects attributable to logging.

At the Hoodoo site, the overall abundance of small snails in litter samples had decreased greatly, from an average of 4.8 snails/liter in 2002 to 1.7 snails/liter in 2006. This decline can be explained only partially by logging: A significant treatment effect in comparisons of pre- and post-logging data was found for small snails as a group but not for any individual species. Relatively small sample sizes in 2006 may have obscured the detection of treatment effects for some individual species.

Results for the four experimental sites sampled so far indicate that several species of forest-floor snails are sensitive to logging. In particular, a significant treatment effect has been found at all sites for Pristiloma species (Tightcoil snails), and these snails provide an excellent focal group due to their abundance and wide distribution in coastal forests of British Columbia.

Results from the experimental sites so far indicate that VR-treatments are superior to clearcutting in maintaining patterns of abundance of sensitive species of gastropods, at least over the short term. Responses of gastropods to the different VR-treatments have been mixed, depending on the forest type and individual species of gastropods. In drier second-growth forest, such as at the Port McNeill site, small VR-retention groups (0.25 ha and smaller) are susceptible to drying and provide poor habitat for sensitive species of gastropods, whereas large VR-groups (0.8 ha) are better but not equivalent to uncut forest. In moist, older forest, such as at the Hoodoo and Tsitika sites, small VR-groups (about 0.25 ha) are more effective than similar-sized groups in drier, second growth forest. So far, we have detected no differences in gastropod abundance within tree patches between 10%, 20%, or 30% retention level treatments. Differences in the abundance and diversity of gastropods within tree patches may become more pronounced over time if gastropod dispersal from group to group is facilitated within the

higher retention level treatments where the groups are closer together, on average. In addition, VR-blocks with high levels of retention should benefit from increased dispersal of gastropods from groups into the logged matrix as conditions improve in the matrix over time. When 10, 20 and 30% levels of dispersed VR-retention were compared, the 30% level supported a higher abundance of sensitive species of gastropods over the short term than did lower retention level treatments (Horseshoe Lake site).

Post-logging surveys at the remaining two experimental sites are planned for the 2007 field season, completing the first round of post-disturbance surveys, 2 – 4 years after logging. Periodic resurveys of the experimental sites in the future are needed to elucidate longer-term responses of gastropods to their pattern of recovery within different logged treatments.

TABLE OF CONTENTS

Acknowledgments ...... i Executive Summary ...... ii List of Tables...... vi List of Figures and Appendices ...... vi Plates ...... viii 1.0 Introduction ...... 1 2.0 Study Area and Methods...... 2 2.1 Study sites ...... 2 2.2 Study design...... 2 2.3 Survey methods...... 3 2.3.1 Artificial cover-objects ...... 3 2.3.2 Litter samples...... 6 2.4 Data handling and analysis...... 7 3.0 Results and Discussion ...... 9 3.1 Port McNeill Experimental Site (R817) ...... 9 3.1.1. Overview of gastropods found...... 9 3.1.2 Relative abundance in relation to treatments: ACO data ...... 12 3.1.3 Relative abundance in relation to treatments: Litter data ...... 16 3.1.4 Species diversity in relation to treatments...... 21 3.2 Hoodoo Experimental Site (R1000) ...... 23 3.2.1 Overview of species found ...... 23 3.2.2 Relative abundance in relation to treatments: ACO data ...... 26 3.2.3 Relative abundance in relation to treatments: Litter data ...... 29 3.2.4 Species diversity in relation to treatments...... 33 4.0 Summary and Conclusions ...... 34 5.0 Literature Cited...... 36

LIST OF TABLES Table 1. Number of gastropods found at the Port McNeill experimental site during pre- logging and post-logging survey periods in 2002 and 2006, respectively...... 9 Table 2. Test statistics for comparison of relative abundance (number per artificial cover-object station) of individual species and groupings of gastropods between pre- and post-logging survey periods at the Port McNeill experimental site (Manova)...... 12 Table 3. Test statistics for comparison of average density (#/liter/plot) of individual species and groupings of small snails between pre- and post-logging survey periods at the Port McNeill experimental site (Manova for repeated measures). Data from litter samples...... 18 Table 4. Test statistics for comparison of species diversity of gastropods between pre- and post-logging survey periods at the Port McNeill experimental site (Manova). Data from artificial cover-objects...... 21 Table 5. Number of gastropods found at the Hoodoo experimental site during pre- logging and post-logging survey periods in July - Nov 2002 and Sept - Nov 2006, respectively...... 23 Table 6. Test statistics for comparison of relative abundance (number per artificial cover-object station) of individual species and groupings of gastropods between pre- and post-logging survey periods at the Hoodoo experimental site (Manova). 26 Table 7. Test statistics for comparison of average density (#/liter/plot) of individual species and groupings of small snails between pre- and post-logging survey periods at the Hoodoo experimental site (Manova for repeated measures). Data from litter samples...... 31

LIST OF FIGURES AND APPENDICES Figure 1. Photo mosaic of the Port McNeill experimental site layout…………...... 4 Figure 2. Photo mosaic of the Hoodoo (East Yakoun) site experimental layout...... 5 Figure 3. Mean number of gastropods per artificial cover-object (ACO) station found during surveys in the spring and fall of 2002 and 2006 at the Port McNeill experimental site...... 11 Figure 4. Total monthly precipitation for Port Hardy, about 24 km north of the Port McNeill study site. Normal: Average for 1971-2000...... 11 Figure 5. Relative abundance of species and groups of gastropods showing significant treatment effects in pre- and post-logging comparisons at the Port McNeill site. Data from artificial cover-objects...... 14 Figure 6. Total number of small snails (dead and live) with adult shell diameter < 5 mm extracted from 200 liters of litter at the Post McNeill experimental site in 2002 and 2006...... 17 Figure 7. Comparison of the density of small snails extracted from litter samples during pre- and post-logging periods at the Port McNeill experimental site...... 19 Figure 8. Species diversity measures before and after logging at the Port McNeill experimental site. Data from artificial cover-objects...... 22

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Figure 9. Mean number of gastropods per artificial cover-object (ACO) station found during surveys in 2002 and 2006 at the Hoodoo experimental site...... 25 Figure 10. Total monthly precipitation for Sandspit, Moresby Island, about 45 km northeast of the Hoodoo study site. Normal: Average for 1971-2000...... 25 Figure 11. Relative abundance of individual species of gastropods showing significant treatment effects in pre- and post-logging comparisons at the Hoodoo site. Data from artificial cover-objects...... 28 Figure 12. Number of small snails (dead and live) with adult shell diameter < 5 mm extracted from 100 liters of litter at the Hoodoo experimental site in October 2002 and 2006...... 30 Figure 13. Comparison of the density of small snails (all species combined) extracted from litter samples during pre- and post-logging periods at the Hoodoo experimental site...... 32 Figure 14. Species diversity measures before and after logging at the Hoodoo experimental site. Data from artificial cover-objects...... 33

Appendix A. Relative abundance of species and groups of gastropods showing non- significant treatment effects in pre- and post-logging comparisons at the Port McNeill site. Data from artificial cover-objects. Whisker: SE ...... 38 Appendix B. Relative abundance of species and groups of gastropods showing non- significant treatment effects in pre- and post-logging comparisons at the Hoodoo site. Data from artificial cover-objects...... 41 Appendix C. Density of small snails extracted from litter samples showing non- significant treatment effects in pre- and post-logging comparisons at the Hoodoo site...... 45

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PLATES

Plate 1. This treatment area at the Port McNeill experimental site consisted of very small retained groups of trees. We considered this to be dispersed retention because of the very open nature of the site.

Plate 2. Clearcut treatment area at Port McNeill showing dense herbaceous growth 3 years after logging.

Plate 3. The second growth forest at Port McNeill lacked an understory in many areas due to the even- aged relatively dense canopy. Group retention at this site resulted in very dry interior conditions even in the large-sized group above, due to wind and solar radiation penetrating to the center of the group.

Plate 4. View of retained groups of trees and logged matrix at the Hoodoo (East Yakoun) experimental site, July 2006.

Plate 5. Retained group of trees at the Hoodoo experimental site, October 2006.

Plate 6. Control area (plot 1) showing an Artificial Cover Object (ACO) at the Hoodoo site, October 2006

Plate 7. Port McNeill site showing clearcut treatment with small retained groups of trees in the background to the right, October 2006.

Plate 8. “Haida Gwaii” slug (an undescribed species likely endemic to the Queen Charlotte Islands) on an ACO in a retained group at the Hoodoo site, October 2006.

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Plate 9. Taking litter samples from a group at the Hoodoo site, October 2006. Small snails were extracted from the litter samples in the lab.

Plate 10. Striate Tightcoil snails (Pristoloma stearnsi.) mating on an ACO at Port McNeill, October 2006.

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Plate 11. Banana slug (Ariolimax columbianus) on an ACO at Port McNeill. Banana slugs use the ACOs both for shelter and as a food source.

Plate 12. Control area (Plot 3) at Port McNeill contained a moist depression with abundant herbaceous and shrubby vegetation that supported high densities of gastropods.

1.0 INTRODUCTION Terrestrial gastropods (slugs and land snails) were selected as a focal group for examining the effects of variable-retention (VR) logging practices in forest ecosystems as part of Western Forest Product’s (formerly Weyerhaeuser’s) Adaptive Management Program (Bunnell et al. 2003). These organisms were included because of their sensitivity to changes in forest floor conditions associated with logging and their sedentary habits, which preclude escape from unfavourable conditions. As a result, gastropod faunas are thought to reflect the disturbance history of particular forest stands (Strayer et al. 1986, Prezio et al. 1999). One goal of VR logging is to retain some attributes of old-growth or mature forest in logged areas, potentially adding to the biodiversity of second-growth forests on lands managed for forestry. Gastropods may benefit from the retention of old-growth or mature forest attributes in logged areas, resulting in persistence of populations within the retained patches and their subsequent dispersal to adjacent logged areas as conditions improve over time.

This project is a continuation of a pilot study initiated in the fall of 1999. Initial studies from 1999 to 2001 focused on characterizing gastropod faunas of different forest types, developing sampling methodologies, and investigating the sensitivity of different species to logging at operational VR-sites (Ovaska and Sopuck 2000, 2001, 2002). In 2001, work began at experimental sites with the objective of comparing the effectiveness of different VR-treatments and clearcutting on maintaining patterns of species diversity and abundance of gastropods on the forest floor. From 2001 to 2003, we completed intensive pre-disturbance sampling at six experimental sites on Vancouver Island, the coastal mainland, and the Queen Charlotte Islands (Ovaska and Sopuck 2005). These pre-disturbance data will be compared with data collected after logging on the same plots. Such an experimental approach provides a powerful method for examining causal effects of different logging treatments by taking into account pre-existing differences due to habitat.

In 2005, post-logging surveys were completed at two of the six experimental sites: Tsitika site on Vancouver Island and Horseshoe Lake site near Powell River on the mainland (Ovaska and Sopuck 2006). This progress report presents the results of post- logging surveys and comparisons with pre-logging data at two additional sites: Port McNeill site on Vancouver Island and the Hoodoo site on Graham Island, Haida Gwaii (Queen Charlotte Islands). Both sites were surveyed for gastropods in 2002, before logging (pre-logging surveys) and again in 2006, 2-3 years after logging was completed in 2003-2004 (post-logging surveys). Additional post-logging surveys will be conducted at the remaining two experimental sites in 2007, completing surveys at each of the six experimental sites sampled for gastropods and followed by submission of a final report in March 2008.

2.0 STUDY AREA AND METHODS

2.1 Study sites

The Port McNeill experimental site (R817) is located about 6 km southwest of the town of Port McNeill on northeastern Vancouver Island. The site is within the Submontane Very Wet Maritime (vm1) subzone of the Coastal Western Hemlock (CWH) biogeoclimatic zone. Elevations range from 70 – 152 m above sea level (asl). The habitat consists of naturally regenerated second-growth forest, about 60 – 80 years old, often forming dense even-aged stands. The site is almost entirely coniferous, dominated by western hemlock (Tsuga heterophylla), amabilis fir (Abies amabilis), and western redcedar (Thuja plicata). Ground cover is variable and ranges from little understory and compact needle litter to dense patches of sword fern (Polystichum munitum) and thickets of salmonberry (Rubus spectabilis) in moist depressions.

The Hoodoo experimental site (R1000) is located about 14 km south of Port Clements, Graham Island, Queen Charlotte Islands (Haida Gwaii). The site is within the Submontane Wet Hypermaritime (wh1) subzone of the Coastal Western Hemlock (CWH) biogeoclimatic zone. The habitat consists of a mixture of old growth (>200 years) and second growth (80 – 100 years old) naturally regenerated coniferous forest. The terrain is very flat, and elevations range from 65 – 80 m asl. The dominant tree species are western hemlock, Sitka spruce (Picea sitchensis) and western redcedar. Several small meandering streams flow through the area. Ground cover consists mainly of a thick layer of mosses with pockets of salal (Gaultheria shallon) and huckleberry (Vaccinium spp.) in some areas. The herb and shrub layers are sparse, possibly due to deer browsing.

2.2 Study design

There were a clearcut, three VR treatments, and an uncut control area at both sites. The treatment and control areas were about 20 ha.

At the Port McNeill site, the experimental treatments were as follows: • Clearcut • VR-group (large), which consisted of retention patches 0.80 ha in size within the logged matrix • VR-group (small), which consisted of retention patches 0.25 ha in size within the logged matrix • VR-dispersed, which consisted of retention of trees in numerous very small groups throughout the treatment area • Control, which consisted of a larger uncut reference site within older second-growth forest The overall retention level at each of the three VR-treatments was 15%.

At the Hoodoo site, the experimental treatments were as follows:

• Clearcut • VR-group with 10% of trees retained • VR-group with 20% of trees retained • VR-group with 30% of trees retained • Control, which consisted of a larger uncut reference site within mixed old-growth and older second-growth forest

The retention groups or patches of trees were about 0.25 ha in size in all three VR- treatments, but the overall retention within the treatment areas varied. Thus, the groups were closer together, on average, within the higher level retention treatments.

In 2002, before logging took place, we set up four gastropod sampling plots within each of the treatment and control areas at both sites. In the VR- treatment areas, we placed the plots at locations selected by the Weyerhaeuser’s (now Western Forest Product’s) Structural Monitoring Team for surveys of vegetation and other habitat features. For the fourth plot, we randomly selected an additional site. There were six randomly chosen structural monitoring plots within the control and clearcut treatments at both sites and the dispersed treatment at Port McNeill, and from these we selected the first four plots for gastropod sampling. Within the VR-group treatments, we placed the plots within the designated tree patches, rather than within the matrix surrounding the groups. Logistic constraints prevented additional sampling of the matrix, but it can be assumed that the matrix immediately surrounding the VR-groups sampled contains similar habitat and gastropod fauna.

Each gastropod plot consisted of ten sampling stations, distributed 10 m apart along two perpendicular transect lines. Hence, there were 40 stations distributed within four plots per treatment area and a total of 200 stations per site. In 2006, we relocated the plots within the now logged area using geoposition coordinates and maps, and set them up in the same locations as previously. Maps of the experimental design for the sites, showing the placement of gastropod plots, are shown in Figures 1 and 2.

2.3 Survey methods We used two main methods to sample gastropods at the experimental sites: artificial cover-objects and litter sampling. Pilot studies in 1999 – 2001 deemed these methods most appropriate for measuring relative abundance (Ovaska and Sopuck 2001, 2002, 2003, 2004a).

2.3.1 Artificial cover-objects Artificial cover-objects consisted of sheets of corrugated cardboard that other studies (Hawkins et al. 1998) and our own previous studies had determined were effective for sampling a variety of terrestrial gastropod species that use the structures for shelter. The sheets are laid on the forest floor, flush with the ground, and allowed to weather and accumulate moisture for at least two weeks. The cover-objects can then be

Figure 1. Photo mosaic of the Port McNeill experimental site layout.

Figure 2. Photo mosaic of the Hoodoo (East Yakoun) site experimental layout.

inspected for gastropods that adhere to the surfaces of the board or use the ground interface. The advantages of this method are ease of sampling, minimal observer bias, and little disturbance to the surrounding habitat, allowing repeated surveys of sensitive habitats. Our design for the cover-object evolved over the study; hence the type and number of cover-objects used at the six experimental sites differ somewhat. Initially, we used two small (1’ x 1’), layered covers and one large (2’ x 2’) single sheet at each sampling station at Tsitika and Horseshoe Lake experimental sites in 2001 and at Port McNeill in 2002. Subsequently, we used only small cardboard covers, four per station, because small covers were found to be more effective than large cardboards, resulting in larger sample sizes (Ovaska and Sopuck 2002, 2003). Small covers (1’ x 1’) were used for post-logging surveys at all sites and consisted of two cardboard sheets stapled together, resulting in four sampling surfaces (top, bottom, and two in-between). The bottom sheet had a wavy, corrugated surface on both sides, created by stapling two single faced corrugated sheets together. The exposed corrugated surfaces were designed to enhance the substrate for the attachment of small snails.

At the Port McNeill site, there were 4 pre-logging surveys and 6 post-logging surveys of the artificial cover-objects. The pre-logging surveys were conducted in May – June (3 surveys) and October (1 survey) 2002; the post-logging surveys were conducted in May – June (2 surveys) and September – November (4 surveys) 2006. A dry spring and early summer in 2006 constrained surface activity by gastropods and necessitated that the bulk of the survey effort be delayed until after fall rains have saturated the ground.

At the Hoodoo site, there were 4 pre-logging surveys and 3 post-logging surveys of the artificial cover-objects. The pre-logging surveys were conducted in July (1 survey) and September – November (3 surveys) 2002; the post-logging surveys were conducted in September – November 2006.

2.3.2 Litter samples To obtain an additional estimate of the abundance of small snails, we collected litter samples for subsequent analysis in the laboratory. This method is very effective for sampling small (with shell diameter < 5 mm) forest floor snails and has been used successfully in previous studies in British Columbia (Cameron 1986). At the Port McNeill site, we collected and analyzed 200 liters of litter (100 l both in June and October) per year in 2002 and 2006. At the Hoodoo site, we collected 100 liters of litter per year in October 2002 and 2006.

We collected samples of litter next to the artificial cover-object stations using a small trowel. To standardize the amount and increase the variety of litter sampled, we sub- divided a 1 m x 1 m area into quarters and took a sample from the centre of each section for a total of 0.5 litres of litter at each station, resulting in two samples of 2.5 l per plot. The objective was to sample a profile of the top layer of the forest floor to a maximum depth of about 10 cm; most gastropods are found within the top layer (Hawkins et al. 1998).

In the laboratory, we first froze the samples to stop any biological activity and then air- dried them. We passed each dried sample through a set of three sieves (mesh diameters: 4.75 mm, 2.0 mm, and 0.5 mm; USA standard testing sieves 4, 10, and 15) and hand-sorted through the residues under a magnifier-lamp (11.5 cm diameter, 3 x magnification lens encircled by a fluorescent light). We collected all snails found for subsequent microscopic examination and identification. The snails were counted and sorted into dead (empty shells or shell fragments) and live specimens (i.e., snails deemed live at the time of collection, usually with the body of the animal showing through the shell). Identification of gastropods was done using descriptions in Pilsbry (1940, 1948) and Forsyth (2004). All specimens are stored in the personal collection of K. Ovaska.

2.4 Data handling and analysis We used Microsoft Excel (Version 2000) spreadsheets and data analysis tools to summarize data and prepare figures. Statistical analyses were performed using the statistical package Jmp In (Version 3.2.1, 1989–1997, SAS Institute Inc.). To examine differences between pre- and post-logging periods, we used a split-plot design with multivariate analysis of variance (MANOVA) to compare relative abundance and species diversity of gastropods. Species diversity was calculated from artificial cover- object (ACO) data only, as this method samples a wider range of species than litter sampling. Relative abundance of individual species or grouping of species was measured as (a) number of animals per ACO station per survey (ACO data) or (b) number of animals per 1 liter of forest litter per 2.5 liter sample per plot (litter sample data). In the analysis of ACO data, there were 40 data points, corresponding to ACO stations, per treatment, for a total of 200 data points at both the Port McNeill and Hoodoo experimental sites. In the analysis of the litter sample data, there were eight samples per treatment, two samples per plot, for a total of 40 data points at the Hoodoo site and 80 points at the Port McNeill site, where samples were collected both in the spring and fall. In the MANOVA models, the effect variables were treatment and plot for the ACO data and treatment and time (Hoodoo site) or treatment, season (spring versus fall), and time (Port McNeill site) for the litter sample data. For those gastropods that showed significant treatment effects in pre- and post-logging comparisons, we used the Tukey-Kramer HSD (honestly significant difference) analysis to test for statistically significant differences among all pairs of treatments (Zar 1996). For the ACO data, we performed this test on the difference between mean number of animals found per sampling station, averaged across the surveys in each year, between pre- and post- disturbance values. This test provides an exact alpha-level test when sample sizes are the same.

To obtain a measure of species diversity, we used the Shannon-Weiner and the Simpson indices of heterogeneity (Krebs 2003). The Shannon-Weiner index is particularly sensitive to rare species in a data set, whereas the Simpson index emphasizes common species. We calculated the test statistics (Shannon’s H’ and Simpson’s 1-D) for each treatment from the ACO data for both pre-logging and post- logging periods using software in Programs for Ecological Methodology (Krebs 2003).

Values for all surveys within a year were combined for these analyses. The program calculated 95% confidence intervals, unevenly distributed around the mean, for the treatments. For the Hoodoo site, the confidence intervals for pre- and post-logging data overlapped widely for all treatments; consequently statistical analysis was unnecessary. For the Port McNeill site where the confidence intervals showed less overlap, we calculated diversity measures individually for each plot and used these values as response variables in the analysis of variance models.

The probability of finding a significant effect by chance increases with the number of comparisons performed (i.e., increased Type I error or falsely detecting a significant effect where one does not exist). Therefore, for each set of comparisons, we used the sequential Bonferroni-correction to calculate experiment-wide alpha (Rice 1989). The 1st significant probability is calculated as α/k, the 2nd as α/(k-1), the 3rd as α/(k-3) and so on, where α represents experiment-wide level of significance and k the number of parameters or comparisons made. For comparisons where more than 5 species were tested individually, we set experiment-wide α = 0.1 to avoid a Type II error (i.e., failing to detect a significant effect where one exists). At both the Port McNeill and the Hoodoo site, we tested effects of logging on the relative abundance of 10 species or groupings of gastropods. Therefore, the 1st significant probability value for individual species was 0.010, the 2nd 0.011, the 3rd 0.0125, the 4th 0.014 and so on.

To illustrate patterns of abundance for individual species and groupings of species during pre- and post-logging periods, we used the average of the surveys within a year for each data point in figures comparing relative abundance and in Appendices A – D. This simplification was done to clarify the presentation of the data; note that results of each survey were included as separate data points in all statistical analyses.

Raw data associated with this study are submitted separately as MS Excel spreadsheets. These data include timing of surveys and weather conditions during each survey day in 2006, and species and numbers of gastropods found per sampling station during each survey in 2002 and 2006 (see Ovaska and Sopuck 2003 for details of survey timing and conditions in 2002).

3.0 RESULTS AND DISCUSSION

3.1 Port McNeill Experimental Site (R817)

3.1.1. Overview of gastropods found In total, we detected 14 species of gastropods at this site, consisting of three species of slugs and 11 species of snails (Table 1). All species were native. There were three species of large snails and eight species of small litter-dwelling snails with adult shell diameter less than 5 mm (Table 1). There was a striking difference in abundance between years for snails of the genus Ancotrema, which were relatively abundant in 2002 but were greatly reduced across all treatments in 2006, probably due to dry weather or natural multi-year fluctuations in populations. The slug Prophysaon foliolatum had also declined greatly. Two snails, Euconulus fulvus and Zonitoides species, and the slug Prophysaon vanattae were found only in 2006, all in very low numbers.

Overall, the abundance of gastropods was low in late May – June 2006 when compared to the same period in 2002, probably because of dry conditions. The depression in abundance was particularly noticeable for large and small snails when combined in multi- species groups (Figure 3). Lower than average amount of precipitation fell from June through October 2006 on northeastern Vancouver Island, as illustrated by data for Port Hardy (Figure 4).

Table 1. Number of gastropods found at the Port McNeill experimental site during pre-logging and post-logging survey periods in 2002 and 2006, respectively.

There were 200 sampling stations; 200 l of litter was examined both in 2002 and 2006. Species codes are used in spreadsheets of raw data. Pre-logging surveys, 2002 Post-logging surveys, 2006 (4 surveys) (6 surveys) Species CODE Artificial Litter samples: Artificial cover- Litter samples: cover-objects Live (dead) objects Live (dead) Slugs: Pacific Banana-slug, Ariolimax ARICO 94 NA 176 NA columbianus Yellow-bordered Taildropper, PROFO 38 NA 15 NA Prophysaon foliolatum Scarletback Taildropper, Prophysaon PROVA 0 NA 2 NA vanattae Large Snails: Lancetooth snails, Ancotrema spp. ANC sp 78 NA 8 NA

Robust Lancetooth, Haplotrema HAPVA 19 NA 31 NA vancouverense

Pre-logging surveys, 2002 Post-logging surveys, 2006 (4 surveys) (6 surveys) Species CODE Artificial Litter samples: Artificial cover- Litter samples: cover-objects Live (dead) objects Live (dead) Northwest Hesperian, Vespericola VESCO 223 NA 428 NA columbianus Small Snails (adult shell width < 5 mm):

Toothless Column, Columella edentula COLED 12 2 (7) 20 6 (1)

Brown hive, Euconulus fulvus EUCFU 0 0 6 0

Western Broadwhorl, Planigyra clappi PLACL 408 140 (113) 276 150 (63)

Broadwhorl Tightcoil, Pristiloma PRIJO 0 15 (6) 0 3 (2) johnsoni Tightcoil species, Pristiloma spp.1 PRI sp 716 245 (115) 1538 201 (56)

Conical Spot, Punctum randolphii PUNRA 53 117 (104) 234 80 (28)

Northwest Striate, Striatura pugetensis STRPU 245 208 (257) 397 217 (204)

Vertigo species, Vertigo spp. VER sp 151 67 (52) 355 69 (44)

Vertiginid (unidentified juvenile of Vertiginid 1 12 (30) 0 4 (1) family Vertiginidae) Zonitoides species ZON sp. 0 0 1 0 1Pristiloma stearnsii, P. lansingii, and juvenile Pristiloma species that could not be assigned to species with confidence.

Port McNeill: Seasonal Abundance

5.0

n Spring-2002 o i 4.0 Spring-2006 at

st Fall-2002

O 3.0 Fall-2006 C A r

e 2.0

# p 1.0 ean M 0.0 Slugs Large Snails Small Snails

Figure 3. Mean number of gastropods per artificial cover-object (ACO) station found during surveys in the spring and fall of 2002 and 2006 at the Port McNeill experimental site. Top of bar – mean; whisker – SE. Values were averaged across treatments and surveys for each year.

Normal Port Hardy: Total precipitation 2002 2006 400 350 )

m 300 m (

n 250 io t 200 a it 150 ip c e

r 100 P 50 0

n r r y n l g p t v c Ju e o Ja Feb Ma Ap Ma Ju Au S Oc N De Figure 4. Total monthly precipitation for Port Hardy, about 24 km north of the Port McNeill study site. Normal: Average for 1971-2000. Source: Environment Canada website (http://www.climate.weatheroffice.ec.gc.ca).

3.1.2 Relative abundance in relation to treatments: ACO data Sufficient sample sizes for statistical comparisons existed for eight species of gastropods. Three species showed significant treatment effects in comparisons of relative abundance between pre- and post-logging periods: Pristiloma species, Striatura pugetensis, and Vespericola columbianus (Table 2). The treatment effect approaches significance for a fourth species, Planigyra clappi (P = 0.02; Table 2). There was a significant plot effect for three gastropods, Planigyra clappi, Striatura pugetensis, and Vespericola columbianus, indicating that their abundance also varied among sampling plots within treatment areas, irrespective of the logging treatments.

Table 2. Test statistics for comparison of relative abundance (number per artificial cover-object station) of individual species and groupings of gastropods between pre- and post-logging survey periods at the Port McNeill experimental site (Manova).

Bolding indicates significant effects1. Pre-logging period – 2002 (4 surveys), post-logging period - 2006 (6 surveys). Treatment Plot (within treatment)

Species or group Wilks’ F4,180 P Wilks' F15,180 P lambda lambda Ariolimax columbianus 0.9448 2.6300 0.0360 0.8855 1.5513 0.0916 Haplotrema vancouverense 0.9889 0.5038 0.7330 0.9513 0.6140 0.8612 Planigyra clappi 0.9391 2.9196 0.0226 0.7865 3.2569 <0.0001 Pristiloma species 0.8351 8.8856 <0.0001 0.9066 1.2360 0.2485 Punctum randolphii 0.9617 1.7898 0.1328 0.8708 1.7806 0.0403 Striatura pugetensis 0.7489 15.0902 <0.0001 0.8320 2.4229 0.0031 Vertigo species 0.9829 0.7825 0.5379 0.9774 0.2776 0.9967 Vespericola columbianus 0.8766 6.3325 <0.0001 0.7687 3.6116 <0.0001 Groupings: Slugs (3 spp.) 0.9415 2.7981 0.0275 0.8992 1.3453 0.1795 Small snails (8 spp.) 0.8898 5.5739 0.0003 0.9023 1.2998 0.2062 1Sequential Bonferroni correction was applied to achieve experiment-wide alpha of 0.1 (Rice 1989)

Patterns of abundance for Pristiloma species, S. pugetensis, and Planigyra clappi were consistent with adverse effects of logging: after logging, abundance was greatest in the control and depressed in the treatment areas when compared to pre-logging densities (Figure 5). For all three snails, numbers were most depressed in the clearcut treatment after logging.

For Pristiloma species, the control supported significantly more snails than did the VR- small group and clearcut treatments. Among the logging treatments, the VR-dispersed and VR-large groups supported higher abundance of these snails than did the clearcut (Tukey-Kramer HSD test, α < 0.05). For Striatura pugetensis, the control supported significantly more snails than did the VR-small group, VR-dispersed, and clearcut treatments (Tukey-Kramer HSD test, α < 0.05). The clearcut differed significantly from

all other logging treatments. Planigyra clappi decreased greatly in the clearcut after logging, but unfortunately its numbers were very low in the VR-groups in the uncut forest, precluding comparisons among the different VR-treatments.

Vespericola columbianus had increased somewhat in the clearcut treatment relative to the control and other treatments after logging, and at first glance appeared to have benefited from the removal of the tree canopy and subsequent growth of herbaceous vegetation in the opened areas, at least in the short term. This snail is a habitat generalist (Forsyth 2004) and is often present in moist, open habitats, in addition to forest stands (KO and LS, unpublished data). Its abundance, however, had declined significantly in the small VR-groups when compared to other treatments and the control (Tukey-Kramer HSD test, α < 0.05). The small groups suffered from drying out as a result of exposure to wind and sun, apparently reducing their suitability to these snails.

Treatment effects were non-significant for the remaining four species tested, although two (Punctum randolphii, Vertigo species) showed trends towards decreased abundance in the clearcut (Appendix A). Among VR-treatments, large groups tended to support more Vertigo species than did the other treatments, but otherwise there were no trends. Three species that were relatively abundant in 2002 were rarely found in 2006 (Ancotrema species, Columella edentula, Prophysaon foliolatum); hence effects of the treatments on their populations could not be tested statistically (but see Appendix A for graphs of the data).

Small snails as a group showed a significant treatment effect in pre-post logging comparisons (Table 2, Figure 5). The control supported significantly more small snails than did the clearcut (Tukey-Kramer HSD test, α < 0.05). Among the logging treatments, VR-large groups supported significantly more snails than did the clearcut. Data for eight species of snails were combined to create this group. Three species contributed disproportionately to this group: Pristiloma species (45.1%, 54.4%), Planigyra clappi (25.7%, 9.8%), and Striatura pugetensis (15.4%, 14%)(% contribution during pre- and post-logging surveys, respectively). Vertigo species contributed 9.5% and 12.6% and Punctum randolphii 3.3% and 8.3%, while the remaining three species contributed less than 1% each during the pre- and post logging surveys, respectively.

Figure 5. Relative abundance of species and groups of gastropods showing significant treatment effects in pre- and post-logging comparisons at the Port McNeill site. Data from artificial cover-objects. P-value denotes significant treatment effect in pre- and post-treatment comparisons.

Tightcoil species (Pristiloma sp.) Pre-logging 3.50 P < 0.0001 Post-logging 3.00 n o

i 2.50 at st

O 2.00 C A r

e 1.50

# p 1.00 ean

M 0.50

0.00 Clearcut VR-dispersed VR-small-group VR-large-group Control

Northwest Striate (Striatura pugetensis) Pre-logging 1.40 P < 0.0001 Post-logging 1.20

n o

i 1.00 t

sta O 0.80 C

A r e 0.60 # p

an 0.40 e M 0.20

0.00 Clearcut VR-dispersed VR-small-group VR-large-group Control

Western Broadwhorl (Planigyra clappi)

2.50 Pre-logging P = 0.02; NS Post-logging

2.00 n o i at 1.50 O st C

A r e 1.00 # p ean M 0.50

0.00 Clearcut VR-dispersed VR-small-group VR-large-group Control 15

Figure 5 (continued). Relative abundance of species and groups of gastropods showing significant treatment effects in pre- and post-logging comparisons at the Port McNeill site. Data from artificial cover-objects. P-value denotes significant treatment effect in pre- and post-treatment comparisons.

Northwest Hesperian (Vespericola columbianus)

0.90 P < 0.001 Pre-logging 0.80 Post-logging 0.70

n o i

at 0.60 st 0.50

r ACO e 0.40

# p 0.30 an

e M 0.20

0.10

0.00 Clearcut VR-dispersed VR-small-group VR-large-group Control

Small snails (8 species)

Pre-logging 7.00 P = 0.003 Post-logging 6.00 n o

i 5.00 stat

O 4.00 AC r

e 3.00 p # 2.00 ean M 1.00

0.00 Clearcut VR-dispersed VR-small-group VR-large-group Control

3.1.3 Relative abundance in relation to treatments: Litter data The overall abundance of small snails in litter samples had decreased somewhat from 2002 to 2006, from an average of 7.5 snails in 2002 to 5.6 snails per liter of litter (dead and live snails combined). This decline is associated with lower than average rainfall in the summer and early fall of 2006 (Figure 4). However, analyses incorporating effects of logging treatments show that the decline for many species is attributable to logging rather than to differences between spring and fall or between years (significant “treatment” effect and non-significant “season” and “time” effects in multivariate analyses of variance; Table 3). Dry conditions in 2006 probably exacerbated the effects of logging.

The treatment effect was significant for all five species tested individually and for all small snails combined (Table 3). A similar pattern is evident whether both dead and live snails (at the time of collection) or only live snails are considered. Empty shells of these small snails are very thin and presumably disintegrate or are consumed by other litter invertebrates within one season. The results are consistent with adverse effects of logging for four species (Planigyra clappi, Pristiloma species, Punctum randolphii, and Striatura pugetensis) and for all small snails as a group. Two of the above species (P. clappi and S. pugetensis) show a pronounced decrease in the clearcut but an increase in the small VR-group treatments; two species (P. randolphii and Pristiloma species) and small snails as a group show a decrease in the clearcut treatment relative to the control and all VR-treatments (Figure 7). In contrast, one snail (Vertigo species) showed an increase in the clearcut treatment after logging relative to other treatments, where its abundance had decreased slightly (Figure 7).

The small snails group consisted of seven species, four of which contributed disproportionately to the data. The following values show the percentage contribution of these main contributors during pre- and post-logging surveys, respectively: Striatura pugetensis (31.2%, 37.3%); Pristiloma species (24.2%, 22.8%); Planigyra clappi (17.0%, 18.9%); Vertigo species (8.0%, 10.0%). The remaining four species contributed less than 3% each to the group.

Figure 6. Total number of small snails (dead and live) with adult shell diameter < 5 mm extracted from 200 liters of litter at the Post McNeill experimental site in 2002 and 2006.

800 Port McNeill litter samples: 700 Spring-2002 Spring

) Spring 2006 600 ead d 500

ve & i l 400 ( s l ai 300

sn f 200

# o 100

0 . . D L p A U p id ils E C IJO R P s in a L A R I s N R g O P R R ti sn PL P PU ST r ll C VE e a V m ll s A

800 Fall 2002 Port McNeill litter samples:

700 Fall 2006 Fall ) 600 ead

d 500 ve & i l 400 (

s l

ai 300

sn f 200

# o 100

. D L O p A U . id ls E IJ s P sp in ai L AC I R g n UNR R rti s PL PR PR P ST e ll CO VE V a sm ll A

COLED – Columella edentula; PRIJO – Pristiloma johnsoni; PRI sp. – Pristiloma species (P. stearnsii & P. lansingii); PUNRA – Punctum randolphii; STRPU – Striatura pugetensis; VER sp. – Vertigo species; Vertiginid (total number for family Vertiginidae: COLED, VER sp., and unidentified juveniles).

Table 3. Test statistics for comparison of average density (#/liter/plot) of individual species and groupings of small snails between pre- and post-logging survey periods at the Port McNeill experimental site (Manova for repeated measures). Data from litter samples.

A. Live snails: Treatment Season Time Species or group Wilks' Wilks' Wilks' F P F P F P lambda 4,74 lambda 1,74 lambda 1,74 Planigyra clappi 0.8769 2.5979 0.0430 0.9920 0.5983 0.4417 0.9995 0.0359 0.8502 Pristiloma species 0.8559 3.1144 0.0200 0.9789 1.5915 0.2111 0.9823 1.3365 0.2514 Punctum randolphii 0.8549 3.1402 0.0193 0.9978 0.1636 0.6871 0.9787 1.6071 0.2089 Striatura pugetensis 0.8536 3.1736 0.0183 0.9988 0.0863 0.7698 0.9993 0.0514 0.8213 Vertigo species 0.8826 2.4614 0.0526 0.9716 2.1601 0.1459 0.9999 0.0104 0.9191 All small snails 0.8490 3.2907 0.0154 0.9972 0.2062 0.6511 0.9959 0.3040 0.5831 (combined)

B. Live and dead snails (i.e., includes empty shells): Treatment Season Time Species or group Wilks' Wilks' Wilks' F P F P F P lambda 4,74 lambda 1,74 lambda 1,74 Planigyra clappi 0.8536 3.1718 0.0184 0.9980 0.1475 0.7020 0.9906 0.2906 0.5915 Pristiloma species 0.8640 2.9121 0.0270 0.9931 0.5165 0.4746 0.9666 2.5583 0.1140 Punctum randolphii 0.8541 3.1591 0.0187 0.9908 0.6858 0.4103 0.9465 4.1814 0.0444 Striatura pugetensis 0.8329 3.7123 0.0083 0.9987 0.0949 0.7588 0.9966 0.2515 0.6175 Vertigo species 0.8790 2.5457 0.0464 0.9909 0.6824 0.4114 0.9997 0.0239 0.8777 All small snails 0.8432 3.4396 0.0124 0.9999 0.0002 0.9875 0.9772 1.7257 0.1923 (combined)

Figure 7. Comparison of the density of small snails extracted from litter samples during pre- and post-logging periods at the Port McNeill experimental site.

P-value indicates significant treatment effect between pre- and post-logging samples.

Western Broadwhorl, Planigyra clappi: Live & dead snails P = 0.018 5.0 Pre-logging 4.5 Post-logging 4.0

er 3.5 t

i 3.0 1 l

r e 2.5 y p t i 2.0 s n

e 1.5 D 1.0 0.5 0.0 Clearcut VR-Dispersed VR-Small-group VR-Large-group Control

Tightcoil snails Pristiloma species: P = 0.027 Live & dead snails 5.0 Pre-logging 4.5 Post-logging 4.0

er 3.5

lit 3.0 1 r e 2.5

y p it 2.0 s

n e 1.5 D 1.0 0.5 0.0 Clearcut VR-Dispersed VR-Small-group VR-Large-group Control

Conical Spot, Punctum randolphii: P = 0.019 Live & dead snails 4.5 Pre-logging 4.0 Post-logging 3.5

r te

i 3.0 l 1 r 2.5 pe

y 2.0 t i

ns 1.5 e D 1.0 0.5

0.0 Clearcut VR-Dispersed VR-Small-group VR-Large-group Control 20

Figure 7 (continued). Comparison of the density of small snails extracted from litter samples during pre- and post-logging periods at the Port McNeill experimental site.

P-value indicates significant treatment effect between pre- and post-logging samples.

Northwest Striate, Striatura pugetensis: Live & dead snails P = 0.008 10.0 Pre-logging 9.0 Post-logging 8.0

r e 7.0 lit 6.0 1 r e 5.0 p y

it 4.0 s n

e 3.0 D 2.0 1.0 0.0 Clearcut VR-Dispersed VR-Small-group VR-Large-group Control

Vertigo snails, Vertigo species Live & dead snails P = 0.046 2.5 Pre-logging Post-logging 2.0

r te i l 1.5

1 r

pe y t i 1.0 ns e

D 0.5

0.0 Clearcut VR-Dispersed VR-Small-group VR-Large-group Control

All small snails (7 species) Live & dead snails P = 0.012 30.0 Pre-logging 25.0 Post-logging

er t i 20.0 1 l

r e 15.0 y p t

i s

n 10.0 e D 5.0

0.0 Clearcut VR-Dispersed VR-Small-group VR-Large-group Control

3.1.4 Species diversity in relation to treatments We detected no statistically significant effects that could be attributed to logging (Table 4; Figure 8). However, a trend towards depressed diversity is evident in VR-dispersed and VR-small groups after logging (Figure 8). The two indices used differed in their emphasis – Simpson’s index emphasizes common species and Shannon-Weiner index rare species in the data set – but both showed very similar patterns (Figure 8). There was a significant “time” effect with both indices, indicating that the pattern of diversity between 2002 and 2006 was different, irrespective of logging treatments (Table 4). This difference likely reflects declines of several species across the treatments, possibly as a result of prolonged dry conditions.

Table 4. Test statistics for comparison of species diversity of gastropods between pre- and post-logging survey periods at the Port McNeill experimental site (Manova). Data from artificial cover-objects.

Bolded values indicate significant effects.

Wilks Index or effect F DF P lambda Simpson index: Treatment (between subjects) 0.7604 1.1815 4/15 0.3586 Time (within subjects) 0.6876 6.8150 1/15 0.0197 Time x Treatment (within subjects) 0.8388 0.7206 4/15 0.5911 Shannon-Weiner index: Treatment (btw subjects) 0.7133 1.5073 4/15 0.2500 Time (within subjects) 0.6119 9.5153 1/15 0.0075 Time x Treatment (within subjects) 0.8378 0.7258 4/15 0.5879

Figure 8. Species diversity measures before and after logging at the Port McNeill experimental site. Data from artificial cover-objects. Whisker – 95% confidence interval.

Port McNeill: Simpson Diversity Index Pre-logging 0.90 Post-logging 0.85

) 0.80 D - 1

( 0.75 e r

u 0.70 s

e 0.65

y 0.60 t

si 0.55

ver i D 0.50 0.45 0.40 Clearcut VR-dispersed VR-small group VR-large group Control

Port McNeill: Shannon Weiner Diversity Index Pre-logging Post-logging 3.00 2.80

) 2.60 ' H 2.40 e ( r

u 2.20 s a

e 2.00 y m

t 1.80 i s r 1.60 ve i

D 1.40 1.20 1.00 Clearcut VR-dispersed VR-small group VR-large group Control 23

3.2 Hoodoo Experimental Site (R1000)

3.2.1 Overview of species found In total, we detected 14 species of gastropods at this site, consisting of four species of slugs and 10 species of snails (Table 5). All species were native. Slugs included an undescribed species and genus, related to the jumping-slugs (genus Hemphillia), that was first discovered in 2002 at this site (Ovaska and Sopuck 2003, 2004b). There were four species of large snails and six species of small litter-dwelling snails with adult shell diameter less than 5 mm (Table 5). Species richness of small snails was relatively low at this site when compared to gastropod faunas farther south (Ovaska and Sopuck 2005). Interestingly, overall abundance of small snails was greater in 2006 than in 2002, while abundance of slugs and large snails was much lower.

Overall, the abundance of slugs and large snails was relatively low in 2006 when compared to the 2002 (Figure 9). In particular, two species of slugs (Ariolimax columbianus; Prophysaon foliolatum) and two species of large carnivorous snails (Haplotrema vancouverense; Ancotrema species) that were relatively common at the site in 2002 had declined drastically by 2006 (Table 5, Appendix B), possibly as a result of dry summer conditions preceding the surveys in 2006. Rainfall was less than usual from April to October that year on the archipelago that normally receives much precipitation throughout the year (Figure 10).

Table 5. Number of gastropods found at the Hoodoo experimental site during pre- logging and post-logging survey periods in July - Nov 2002 and Sept - Nov 2006, respectively.

There were 200 sampling stations; 100 l of litter was examined in 2002 and 2006. Codes are used in spreadsheets of raw data. Pre-logging surveys, 2002 Post-logging surveys, 2006 (4 surveys) (3 surveys) Species CODE Artificial cover- Litter samples: Artificial cover- Litter samples: Live objects Live (dead) objects (dead) Slugs: Pacific Banana-slug, Ariolimax ARICO 59 NA 3 NA columbianus Yellow-bordered Taildropper, PROFO 275 NA 36 NA Prophysaon foliolatum Scarletback Taildropper, PROVA 4 NA 5 NA Prophysaon vanattae Haida Gwaii Slug (cf "Staala STAGW 8 NA 7 NA gwaii"; undescribed species) Large Snails: Lancetooth snails, Ancotrema spp. ANC sp 21 NA 2 NA

Pre-logging surveys, 2002 Post-logging surveys, 2006 (4 surveys) (3 surveys) Species CODE Artificial cover- Litter samples: Artificial cover- Litter samples: Live objects Live (dead) objects (dead) Pygmy Oregonian, Cryptomastix CRYGE 3 NA 6 NA germana Robust Lancetooth, Haplotrema HAPVA 174 NA 41 NA vancouverense Northwest Hesperian, Vespericola VESCO 98 NA 53 NA columbianus Small Snails (adult shell width < 5 mm):

Toothless Column, Columella COLED 25 9 (3) 25 1 (0) edentula Brown hive, Euconulus fulvus EUCFU 12 1 (0) 120 2 (0) Tightcoil species, Pristiloma spp.1 PRI sp 584 84 (55) 458 71 (13) Conical Spot, Punctum randolphii PUNRA 24 90 (21) 95 13 (2) Northwest Striate, Striatura STRPU 49 60 (70) 100 46 (14) pugetensis Vertigo species, Vertigo spp. VER sp 256 18 (23) 180 6 (4) Vertiginid (unidentified juvenile of Vertiginid 0 27 (36) 6 0 (0) family Vertiginidae) 1Mostly Pristiloma stearnsii and juvenile Pristiloma species that could not be assigned to species.

Hoodoo site: Abundance by gastropod group 2.0 Fall 2002 n o

i Fall 2006

at 1.5

st O

A 1.0 y

# b 0.5

ean

M 0.0 Slugs Large snails Small snails

Figure 9. Mean number of gastropods per artificial cover-object (ACO) station found during surveys in 2002 and 2006 at the Hoodoo experimental site.

Sandspit: Total precipitation 250 )

m 200 m (

n 150 io t a it 100 Normal ip 2002 c

e 2006 50 Pr

n b r r y n l g p t v c e p Ju u c e Ja F Ma A Ma Ju A Se O No D

Figure 10. Total monthly precipitation for Sandspit, Moresby Island, about 45 km northeast of the Hoodoo study site. Normal: Average for 1971-2000. Source: Environment Canada website (http://www.climate.weatheroffice.ec.gc.ca).

3.2.2 Relative abundance in relation to treatments: ACO data Sufficient sample sizes for statistical comparisons existed for eight species of gastropods. Two species showed significant treatment effects in comparisons of relative abundance between pre- and post-logging periods: Pristiloma species and Vespericola columbianus (Table 6). There was a significant plot effect for three gastropods, Euconulus fulvus, Pristiloma species, and Prophysaon foliolatum, indicating that their abundance also varied among sampling plots within treatment areas.

Table 6. Test statistics for comparison of relative abundance (number per artificial cover-object station) of individual species and groupings of gastropods between pre- and post-logging survey periods at the Hoodoo experimental site (Manova).

Bolding indicates significant effects1. Pre-logging period – 2002 (4 surveys), post-logging period - 2006 (3 surveys). Treatment Plot (within treatment)

Species or group Wilks' F4,180 P Wilks' F15,180 P lambda lambda

Euconulus fulvus 0.9808 0.8821 0.4758 0.8506 2.1070 0.0114 Haplotrema vancouverense2 0.9767 1.0734 0.3711 0.9193 1.0532 0.4035 Pristiloma species 0.7832 12.4538 <0.0001 0.7564 3.8654 <0.0001 Prophysaon foliolatum2 0.9601 1.8698 0.1177 0.8112 2.7932 0.0006 Punctum randolphii 0.9894 0.4805 0.7500 0.9185 1.0647 0.3924 Striatura pugetensis 0.9931 0.3110 0.8704 0.9125 1.1505 0.3149 Vertigo species 0.9614 1.8089 0.1290 0.8995 1.3402 0.1824 Vespericola columbianus 0.8963 5.2063 0.0005 0.9384 0.7880 0.6988 Groupings: Slugs (4 spp. combined) 0.9634 1.7112 0.1494 0.8111 2.7956 0.0006 Small snails (7 spp. combined) 0.9006 4.9686 0.0008 0.7771 3.4429 <0.0001 1Sequential Bonferroni correction was applied to achieve experiment-wide alpha of 0.1 2Sample sizes were relatively small for these species during the post-logging period

Patterns of abundance for both Pristiloma species and Vespericola columbianus were consistent with adverse effects of logging (Figure 11). For Pristiloma species, abundance had increased in the control but not in the VR-treatments and had declined in the clearcut between 2002 and 2006. The control differed significantly from all other treatments in pair-wise comparisons of the pre-post-logging data (Tukey-Kramer HSD test, α < 0.05). Responses of the snails to the three VR-treatments were similar. This pattern indicates that the VR-treatments were more effective than clearcutting in maintaining population densities, but that these treatments were not equivalent to the uncut forest. Interpretation is complicated by apparent multi-year fluctuations in abundance of the snails. Pristiloma species also showed a significant treatment effect at the Port McNeill site and at both experimental sites surveyed in 2005 (Tsitika and Horseshoe Lake), and these snails appear to be particularly sensitive to logging.

The abundance of Vespericola columbianus showed a peculiar pattern: It had increased in the control and decreased in two of the VR-treatments, particularly in the 20% retention treatment, but had remained unchanged in the clearcut treatment (Figure 11). Statistically significant differences existed between the control and VR-30% and VR- 20% treatments in pre-post-logging comparisons (Tukey-Kramer HSD test, α < 0.05). These effects are difficult to interpret, as the species is a habitat generalist and may respond positively to logging, as found at the Port McNeill site. At that site, however, its abundance had declined somewhat after logging in small VR-groups, which suffered from drying out as a result of exposure to wind and sun, which may also have been the case at the Hoodoo site.

The treatment effect was non-significant for the remaining six species tested, and there were no apparent trends in the data (Appendix B). Of the species tested, two had declined drastically by 2006 (Haplotrema vancouverense, Prophysaon foliolatum), and hence the results may not be accurate. Two other species (Ancotrema species, Ariolimax columbianus) had declined to an extent that statistical analysis of the data was infeasible (Appendix B).

As at the Port McNeill site, small snails as a group showed a significant treatment effect, whereas slugs as a group did not (Table 6, Figure 11). The control supported significantly more small snails than did the clearcut (Tukey-Kramer HSD test, α < 0.05). The control also supported significantly more snails than did the VR-30% treatment. The remaining VR-treatments were statistically similar to the control. There had been an overall increase in abundance in the control and to a lesser extent in all three VR- treatments but not in the clearcut. This trend largely parallels that for Pristiloma species, which dominated the group. Data for seven species of snails were combined to create this group. Two snails contributed disproportionately to this group: Pristiloma species (61.5%, 46.5%) and Vertigo species (26.9%, 18.3%)(% contribution in 2002 and 2006, respectively). The contributions of the remaining species were as follows: Striatura pugetensis (5.2%, 10.2%), Euconulus fulvus (1.3%, 12.2%), Punctum randolphii (2.5%, 9.7%), Columella edentula (2.6%, 2.5%) and unidentified vertiginids (0%, 0.6%).

Figure 11. Relative abundance of individual species of gastropods showing significant treatment effects in pre- and post-logging comparisons at the Hoodoo site. Data from artificial cover-objects. P-value denotes significant treatment effect in pre- and post-treatment comparisons.

Northwest Hesperian (Vespericola columbianus)

0.35 Pre-logging P = 0.0005 Post-logging 0.30

n 0.25

st O

C 0.20 A

r e 0.15 # p n a e

M 0.10

0.05

0.00 Clearcut VR-Group-10% VR-Group-20% VR-Group-30% Control

Tightcoil species (Pristiloma spp.) Pre-logging

2.00 Post-logging P < 0.0001 1.80 1.60 n

t 1.40 s

O 1.20 C A r

e 1.00

# p 0.80 an e

M 0.60 0.40 0.20

0.00 Clearcut VR-Group-10% VR-Group-20% VR-Group-30% Control

Small snails (7 species)

3.00 Pre-logging P = 0.0008 Post-logging

2.50 n st

2.00 O AC r

e 1.50 p #

ean 1.00 M

0.50

0.00 Clearcut VR-Group-10% VR-Group-20% VR-Group-30% Control 29

3.2.3 Relative abundance in relation to treatments: Litter data Based on litter samples, the overall abundance of small snails had decreased from an average of 4.8 to 1.7 snails per liter of litter, from 2002 to 2006 (Table 7; Figure 12. Reflecting this decrease, there was a statistically significant “time” effect for small snails as a group in comparisons of pre- and post-logging data (Table 7). Curiously, artificial cover-object data show a slight increase, rather than a decline, in relative abundance of small snails (Figure 9). The two methods measure somewhat different strata of the forest floor: While artificial cover-objects measure surface abundance, litter sampling measures densities of snails within the forest litter. Dry conditions, as seen in 2006, may have reduced the accumulation of small snails in the litter during the summer and then populations on the surface rebounded in the fall with increased rainfall.

A significant treatment effect in comparisons of pre- and post-logging data was found for small snails as a group but not for any individual species. A similar pattern is evident whether both dead and live (at the time of collection) snails or only live snails are considered. There was a trend towards reduced abundance of small snails as a group in all treatments after logging, whereas densities within the control were relatively unchanged (Figure 13). Curiously, among the logged treatments, VR-groups in the 20% and 30% retention treatments tended to support least snails when compared to pre- logging densities. The results are difficult to interpret because of the decline of small snails across the treatments from 2002 to 2006 in litter sample data, and resulting small sample sizes during the post-logging surveys. Small post-logging sample sizes and variability among samples within treatments contributed for lack of statistically significant effects for individual species. For example, litter samples showed trends towards decreased abundance of Pristiloma species and Punctum randolphii in all logged treatments similar to those found for all snails (see Appendix D), but the results are either statistically non-significant (Pristiloma species) or insufficient sample sizes during post-logging period precluded analysis (P. randolphii).

The small snails group consisted of seven species, three of which contributed disproportionately to the data. The percentage contribution of these three species was as follows during pre- and post-logging surveys, respectively: Striatura pugetensis (26.2%, 34.9%); Pristiloma species (28.0%, 48.8%); Punctum randolphii (22.3%, 8.7%).

Figure 12. Number of small snails (dead and live) with adult shell diameter < 5 mm extracted from 100 liters of litter at the Hoodoo experimental site in October 2002 and 2006.

Hoodoo litter samples

500 2002 450 2006 )

d 400 a e 350 d

& 300 e

liv 250 (

ils 200 a n 150 s f

o 100 # 50 0 COLED EUCFU PRI sp. PUNRA STRPU VER sp. Vertiginid Small (tot) snails (tot)

COLED – Columella edentula; EUCFU – Euconulus fulvus; PRI sp. – Pristiloma species (mostly P. stearnsii); PUNRA – Punctum randolphii; STRPU – Striatura pugetensis; VER sp. – Vertigo species; Vertiginid (total number for family Vertiginidae: COLED, VER sp., and unidentified juveniles). 31

Table 7. Test statistics for comparison of average density (#/liter/plot) of individual species and groupings of small snails between pre- and post-logging survey periods at the Hoodoo experimental site (Manova for repeated measures). Data from litter samples.

Bolding indicates significant effects. Sequential Bonferroni correction was applied to achieve experiment-wide alpha of 0.1 (Rice 1989). Between subjects: Treatment & Season (spring versus autumn); Within subjects: Time. Insufficient post-logging observations for comparisons existed for 4 additional species (Columella edentula, Euconulus fulvus, Punctum randolphii, Vertigo species).

A. Live Snails Treatment Time Species or group Wilks' Wilks' F P F P lambda 4,35 lambda 1,35 Pristiloma species 0.8552 1.4811 0.2289 0.9897 0.3655 0.5494 Striatura pugetensis 0.8406 1.6594 0.1815 0.9737 0.9449 0.3377 All small snails (combined) 0.6741 4.2310 0.0067 0.7030 14.7890 0.0005

B. All Snails (dead and live) Treatment Time Species or group Wilks' Wilks' F P F P lambda 4,35 lambda 1,35 Pristiloma species 0.9101 0.8648 0.4946 0.8827 4.6508 0.038 Striatura pugetensis 0.8807 1.1852 0.3343 0.8742 5.0352 0.0313 All small snails (combined) 0.7071 3.6245 0.0142 0.5994 23.3918 <0.0001

Figure 13. Comparison of the density of small snails (all species combined) extracted from litter samples during pre- and post-logging periods at the Hoodoo experimental site. P-value indicates significant treatment effect between pre- and post-logging samples.

All Small Snails: Live snails

7.0 P = 0.007 Pre-logging 6.0 Post-logging

5.0 er

t i

1 l 4.0 r e y p

t 3.0 i s n

e D 2.0 1.0

0.0 Clearcut VR-Group-10% VR-Group-20% VR-Group-30% Control

All Small Snails: Live & dead snails

12.00 P = 0.01 Pre-logging Post-logging 10.00 r e

t 8.00 i 1 l r e

p 6.00 y t i s

n 4.00 e D

2.00

0.00 Clearcut VR-Group-10% VR-Group-20% VR-Group-30% Control 33

3.2.4 Species diversity in relation to treatments Species diversity was similar across all treatments and showed widely overlapping 95% confidence intervals in pre- and post-logging comparisons, and we detected no effects that could be attributed to logging (Figure 14). Both the Simpson’s index, which emphasizes common species, and the Shannon-Weiner index, which emphasizes rare species, showed very similar patterns (Figure 14).

Figure 14. Species diversity measures before and after logging at the Hoodoo experimental site. Data from artificial cover-objects. Whisker – 95% confidence interval.

Hoodoo site: Simpson Diversity Index Pre-logging 0.90 Post-logging 0.85

) D

- 0.80 1

(

e r 0.75

asu

e 0.70

y m

t 0.65 i

s r

ve 0.60

i D 0.55

0.50 Clearcut VR-Group 10% VR-Group 20% VR-Group 30% Control

Hoodoo site: Shannon-Weiner Diversity Index

Pre-logging 3.10 Post-logging 2.90 ) ' 2.70 H ( e r 2.50 u as

e 2.30 m y t i 2.10 s r ve

i 1.90 D 1.70

1.50 Clearcut VR-Group 10% VR-Group 20% VR-Group 30% Control

4.0 SUMMARY AND CONCLUSIONS At the Port McNeill experimental site, relative abundance of 3 of 8 gastropod species tested showed significant treatment effects in pre- post-logging comparisons and a 4th approached significance, based on sampling with artificial cover-objects. Numbers of Pristiloma species (P. stearnsii and unidentified juveniles), Striatura pugetensis, Planigyra clappi, as well as numbers of small snails as a group, were depressed in the logged treatments, particularly in the clearcut. Conversely, the snail Vespericola columbianus had increased in the clearcut, and appeared to have benefited from enhanced herbaceous vegetation after logging, at least in the short-term. The VR- treatments (15% retention in small or large groups or in dispersed pattern in tiny groups of trees) supported more snails of sensitive species than did the clearcut but were not equivalent to uncut forest. Large VR-groups were better than the small groups or dispersed treatment. In dense second-growth forest prevalent at this site, tree patches within the small group treatment supported a very sparse understory, and the ground dried out as a result of exposure to wind and sun. The drying was pronounced in 2006 as a result of little rainfall that seldom penetrated the ground in the groups. The large groups were also susceptible to drying out in this forest type due to edge effects, but to a lesser extent than small groups. In analyses of litter samples, there was a significant treatment effect for all five species tested individually and for all small snails combined. The results support those of the artificial cover-object data.

At the Hoodoo experimental site, 2 of 8 species tested showed significant treatment effects in comparisons of relative abundance between pre- and post-logging periods, based on sampling with artificial cover-objects: Pristiloma species and Vespericola columbianus. Effects for V. columbianus, a habitat generalist, showed depressed abundance in the VR-treatments, particularly in the 20% and 30% retention. For Pristiloma species, as well as for small snails as a group, abundance was greatest in the control and depressed in the clearcut treatment. VR-treatments were more effective than clearcutting in maintaining population of small snails but were not equivalent to the uncut forest. Patterns of abundance were similar in the three VR-treatments (10%, 20%, 30% group retention) two years after logging. The treatments at the Hoodoo experimental site form replicates for those at the Tsitika experimental site on northern Vancouver Island, surveyed in 2001 and 2005, and the results for the two sites were similar. Differences in abundance of gastropods within the tree patches of the different retention levels are expected to become more pronounced over time, as dispersal from group to group might be facilitated within the higher retention level treatments. Although not sampled during this study, gastropod abundance in the matrix within VR-group treatment areas is also expected to increase over time as a result of dispersal from groups, especially in areas with higher retention levels. Because densities of gastropods in VR-groups tend to be higher than in logged areas, VR-blocks with higher ratios of retained groups to logged matrix are expected to have higher numbers of gastropods within the block, thus facilitating recolonization of the logged matrix as conditions improve over time.

Treatment effects were also significant for Pristiloma species (mostly P. stearnsii) at the two experimental sites, Tsitika and Horseshoe Lake, surveyed previously (Ovaska and Sopuck 2006), and this species consistently shows sensitivity to logging across sites. Other sensitive species include the small snails Striatura pugetensis and Planigyra clappi. Populations of some other gastropods deemed sensitive to logging, such as large carnivorous snails (Haplotrema vancouverense; Ancotrema species), had decreased drastically at the experimental sites surveyed in 2006, precluding detailed analyses. Summer droughts in 2006 on northern Vancouver Island and the Queen Charlotte Islands may have been responsible for the declines.

In some cases, interpretation of the data was complicated by multi-year fluctuations in gastropod populations due to weather or other habitat changes unrelated to logging. However, pre-post-disturbance comparisons were very useful because abundance of many species of gastropods varied greatly among treatment areas and plots in the uncut forest. Post-logging patterns of abundance for several species were similar to what would be expected with the presumption of adverse effects of logging, and erroneous conclusions would be possible in the absence of pre-disturbance data.

Post-logging surveys at the two remaining experimental sites sampled previously for gastropods (Moakwa on northeastern Vancouver Island; Goat Island in Powell Lake on the mainland) are planned for 2007. These surveys will complete the first round of post- logging surveys at the experimental sites and will permit more detailed analyses of the effectiveness of the different logging treatments on gastropod populations.

In conclusion, the following points are becoming evident from the data collected at experimental sites so far: • Clearcutting (20 ha in size) negatively affects some sensitive species; declines are most evident in dry (well drained) areas of clearcuts, while moist pockets supporting abundant herbaceous growth provide refuges for gastropods within the clearcut. • Gastropod abundance in VR-treatments is usually higher than in clearcuts but is not equivalent to abundance in the uncut forest. • Among VR-treatments, larger groups tend to be better than small groups; small groups are susceptible for drying out, especially in dense second-growth stands, such as at the Port McNeill site. • Among VR-treatments, few differences have been found in gastropod abundance within tree patches of different retention percentage (10%, 20%, 30%), 2 - 4 years after logging. This finding is not surprising, as the patches are often similar in size but differ in their dispersion within the logged matrix. There may be positive effects in the future, as colonization is expected from groups into the matrix over time. • Effectiveness of different VR-treatments varies among sites; treatments that work in moist old-growth forest, such as at the Tsitika site, are not necessarily best in drier, dense second-growth forest, such as at the Port McNeill site, where small groups with sparse understory and a lack of large diameter coarse woody debris are subjected to excessive drying.

• More frequent droughts associated with climate change are expected to result in catastrophic changes in abundance of some species of gastropods; logging treatments that conserve moisture on the forest floor may ameliorate these effects.

5.0 LITERATURE CITED Bunnell, F., G. Dunsworth, D. Huggard, and L. Kremsater. 2003. Learning to sustain biological diversity on Weyerhaeuser’s coastal tenure. Report prepared by Weyerhaeuser Company Limited, Nanaimo, British Columbia. Cameron, R. A. D. 1986. Environment and diversities of forest snail faunas from coastal British Columbia. Malacologia 27:341–355. Forsyth, R. G. 2004. Land Snails of British Columbia. Royal British Columbia Museum handbook. Royal BC Museum, Victoria, BC. Krebs, C. J. 2003. Programs for Ecological Methodology, 2nd edition. Version 6.1.1. Hawkins, J. W., M. W. Lankester, and R. R. A. Nelson. 1998. Sampling terrestrial gastropods using cardboard sheets. Malacologia 39:1–9. Ovaska, K. and L. Sopuck. 2000. Evaluation of the potential of terrestrial gastropods (slugs and snails) for monitoring ecological effects of logging practices on forest-floor conditions on Vancouver Island, British Columbia. A pilot study, October-November 1999. Prep. by Biolinx Environmental Res. Ltd. for Weyerhaeuser Company Ltd. Ovaska, K. and L. Sopuck. 2001. Potential of terrestrial gastropods and salamanders as indicators for monitoring ecological effects of variable-retention logging practices. A pilot study, in the North Island Timberlands, May-November, 2000. Prepared by Biolinx Environmental Research Ltd. for Weyerhaeuser Company Ltd. Ovaska, K. and L. Sopuck. 2002. Terrestrial gastropods and salamanders as indicators for monitoring ecological effects of variable-retention logging practices. A pilot study, May-October, 2001. Report prepared by Biolinx Environmental Research Ltd. for Weyerhaeuser Company Ltd. Ovaska, K., and L. Sopuck. 2003. Terrestrial gastropods as indicators for monitoring ecological effects of variable-retention logging practices. Pre-disturbance surveys at experimental sites, May – October 2002. Report prepared by Biolinx Environmental Research Ltd. for Weyerhaeuser Company Ltd., Nanaimo, BC. Ovaska, K. and L. Sopuck. 2004a. Terrestrial gastropods as indicators for monitoring ecological effects of variable-retention logging practices. Pre-disturbance surveys at experimental sites, May – November 2003. Report prepared by Biolinx Environmental Research Ltd. for Weyerhaeuser Company Ltd., Nanaimo, BC. Ovaska, K. and Sopuck, L. 2004b.Distribution and status of rare forest slugs in western Canada Results of 2003 and 2004 field seasons. Report prepared by Biolinx Environmental Research Ltd. for Endangered Species Recovery Fund (World Wildlife Fund and Environment Canada).

Ovaska, K. and L. Sopuck. 2005. Terrestrial gastropods as indicators for monitoring ecological effects of variable-retention logging practices. Synthesis of field data, fall 1999 – 2003. Report prepared by Biolinx Environmental Research Ltd. for Weyerhaeuser Company Ltd., Nanaimo, BC. Ovaska, K. and L. Sopuck. 2006. Terrestrial gastropods as indicators for monitoring ecological effects of variable-retention logging practices. (2005 field season). Report prepared by Biolinx Environmental Research Ltd. for Cascadia Forest Products, Nanaimo, BC. Pilsbry, H. A. 1940. Land Mollusca of North America (north of Mexico). The Academy of Natural Sciences of Philadelphia, Monograph 1:575–994, i–ix. Pilsbry, H. A. 1948. Land Mollusca of North America (north of Mexico). The Academy of Natural Sciences of Philadelphia, Monograph 2:521–1113, i–xlvii. Prezio, J. R., M. W. Lankester, R. A. Lautenschlager, and F. W. Bell. 1999. Effects of alternative conifer release treatments on terrestrial gastropods in regenerating spruce plantations. Can. J. For. Res. 29:1141–1148. Rice, W. R. 1989. Analyzing tables of statistical tests. Evolution 43: 223–225. Strayer, D., D. H. Pletscher, S. P. Hamburg, and S. C. Nodvin. 1986. The effects of forest disturbance on land gastropod communities in northern New England. Can. J. Zool. 64:2094–2098. Zar JH. 1996. Biostatistical Analysis. Vol. Upper Saddle River, New Jersey, USA:Prentice Hall.

Appendix A (continued). Relative abundance of species and groups of gastropods showing non-significant treatment effects in pre- and post-logging comparisons at the Port McNeill site. Data from artificial cover-objects. Note that effects for following species are plotted but small sample sizes in 2006 precluded statistical analyses: Ancotrema species, Columella edentula.

Lancetooth species (Ancotrema sp.)

0.30 Pre-logging Post-logging 0.25 n io

at 0.20 st

O C 0.15 A

r e

p #

0.10

an e

M 0.05

0.00 Clearcut VR-dispersed VR-small-group VR-large-group Control

Robust Lancetooth (Haplotrema vancouverense)

0.08 Pre-logging Post-logging 0.07

n 0.06 o i t 0.05 sta O

C 0.04 A r

e 0.03 # p

ean 0.02

M 0.01

0.00 Clearcut VR-dispersed VR-small-group VR-large-group Control

Toothless Column (Columella edentula)

0.25 Pre-logging Post-logging

0.20 n o

stati 0.15 O C A r e 0.10 # p ean

M 0.05

0.00 Clearcut VR-dispersed VR-small-group VR-large-group Control

Conical Spot (Punctum randolphii)

1.20 Pre-logging Post-logging 1.00 n o i 0.80 stat O C A

0.60 r e p

# 0.40 ean M 0.20

0.00 Clearcut VR-dispersed VR-small-group VR-large-group Control

Vertigo species (Vertigo sp.)

0.80 Pre-logging 0.70 Post-logging

n 0.60 o ati 0.50 st O C

A 0.40 r e p 0.30 #

ean 0.20 M

0.10

0.00 Clearcut VR-dispersed VR-small-group VR-large-group Control

Appendix B. Relative abundance of species and groups of gastropods showing non- significant treatment effects in pre- and post-logging comparisons at the Hoodoo site. Data from artificial cover-objects. Whisker: SE; Note that effects for following species are plotted but small sample sizes in 2006 precluded statistical analyses: Ariolimax columbianus, Ancotrema species.

Pacific Banana Slug (Ariolimax columbiana)

0.16 Pre-logging Post-logging 0.14

0.12 n st

O 0.10 AC r

e 0.08 # p 0.06 an e M 0.04

0.02

0.00 Clearcut VR-Group-10% VR-Group-20% VR-Group-30% Control

Yellow-bordered Taildropper (Prophysaon foliolatum) Pre-logging 0.70 Post-logging 0.60

n 0.50 st

C 0.40 A r e p 0.30 # ean

M 0.20

0.10

0.00 Clearcut VR-Group-10% VR-Group-20% VR-Group-30% Control

Slugs (4 species) Pre-logging

0.80 Post-logging

0.70

0.60 n st

O 0.50 r AC

e 0.40 # p 0.30 ean M 0.20

0.10

0.00 Clearcut VR-Group-10% VR-Group-20% VR-Group-30% Control

Appendix B (continued). Relative abundance of species and groups of gastropods showing non-significant treatment effects in pre- and post-logging comparisons at the Hoodoo site. Data from artificial cover-objects.

Lancetooth (Ancotrema) species

0.08 Pre-logging 0.07 Post-logging

n 0.06 st

O 0.05 C A r 0.04 e

# p 0.03

ean 0.02 M

0.01

0.00 Clearcut VR-Group-10% VR-Group-20% VR-Group-30% Control

Robust Lancetooth (Haplotrema vancouverense)

0.40 Pre-logging 0.35 Post-logging

0.30 n t s 0.25 ACO

e 0.20 # p 0.15 an e M 0.10

0.05

0.00 Clearcut VR-Group-10% VR-Group-20% VR-Group-30% Control

Toothless Column (Columella edentula)

0.18

0.16 Pre-logging 0.14 Post-logging n

st 0.12 O AC

0.10 r e

p 0.08 # an

e 0.06 M 0.04

0.02

0.00 Clearcut VR-Group-10% VR-Group-20% VR-Group-30% Control

Brown Hive (Euconulus fulvus)

0.50

0.45 Pre-logging 0.40 Post-logging

n 0.35 st O

C 0.30 r A

e 0.25 p

# 0.20 an e

M 0.15 0.10 0.05 0.00 Clearcut VR-Group-10% VR-Group-20% VR-Group-30% Control

Conical Spot (Punctum randolphii)

0.30 Pre-logging 0.25 Post-logging n st

0.20 ACO r

e 0.15 p # an

e 0.10 M

0.05

0.00 Clearcut VR-Group-10% VR-Group-20% VR-Group-30% Control

Northwest Striate (Striatura pugetensis)

0.45 Pre-logging 0.40 Post-logging 0.35 n

st 0.30 O 0.25 r AC e

p 0.20 #

ean 0.15 M 0.10

0.05

0.00 Clearcut VR-Group-10% VR-Group-20% VR-Group-30% Control

Vertigo species (Vertigo spp.)

0.90

0.80 Pre-logging Post-logging 0.70 n

st 0.60 O 0.50 r AC e

p 0.40 #

ean 0.30 M 0.20

0.10

0.00 Clearcut VR-Group-10% VR-Group-20% VR-Group-30% Control

Appendix C. Density of small snails extracted from litter samples showing non- significant treatment effects in pre- and post-logging comparisons at the Hoodoo site. Whisker: SE; Small post-logging sample sizes precluded statistical analysis of data on Punctum randolphii.

Tightcoil species: Live & dead snails

3.0 Pre-logging Post-logging 2.5

r e 2.0 lit 1 r

p 1.5

y it s

n 1.0

e D 0.5

0.0 Clearcut VR-Group-10% VR-Group-20% VR-Group-30% Control

Conical Spot: Live & dead snails

3.0 Pre-logging Post-logging 2.5

t 2.0 i 1 l r e 1.5 y p t

i s

n 1.0 e D 0.5 0.0 Clearcut VR-Group-10% VR-Group-20% VR-Group-30% Control

Northwest Striate: Live & dead snails

2.5 Pre-logging Post-logging 2.0 r

e t i l

1 1.5

pe y t i 1.0 ns e

D 0.5

0.0 Clearcut VR-Group-10% VR-Group-20% VR-Group-30% Control