Selbyana 20(2): 268-275. 1999. THE BIODIVERSITY OF ARTHROPODS FROM NORTHERN TEMPERATE ANCIENT COASTAL RAINFORESTS: CONSERVATION LESSONS FROM THE HIGH CANOPY NEVILLE N. WINCHESTER* AND R:rCHARD A. RING Department of Biology, University of Victoria, P.O. Box 3020, Victoria, British Columbia, Canada, V8W 3N5 ABSTRACT. The biodiversity crisis in global forests continues to be accelerated by habitat loss and con­ sequent extinctions of floral and faunal species assemblages that cannot adjust to rapid, and often large scale, habitat alterations. In an effort to record arthropod diversity in northern temperate rainforests we have studied canopy arthropods in a number of Vancouver Island rainforest types since 1992. Based on these fin~ings we summarize results to answer the following questions: (1) Does guild proportionality vary among different, geographically separated ancient rainforests? (2) Does the numerical dominance of the predator guild by spiders change across these ancient rainforests? (3) Do these ancient rainforests act as repositories for arthropod biodiversity? Answers to these questions are needed to address the issues that surround the maintenance of biological diversity (form and function) in these ancient forests and, in a broader context, rainforests throughout the world. Key words: arthropods, biodiversity, British Columbia, temperate rain forest, conservation, canopy INTRODUCTION (Scudder 1994) and apply system-based conser­ vation approaches across a wide range of forest The global biodiversity crisis continues to be types (Harding & McCullum 1994). accelerated by habitat loss (Wilson 1988, Soule 1991, Raven & Wilson 1992, Laurance 1997) and consequent extinctions of floral and faunal Canopy Arthropods species assemblages (Lockwood 1987, Erwin 1991, Whitmore & Sayer, 1992) that cannot ad­ The study of forest canopies in determining just to rapid, and often large-scale, habitat alter­ the structure of arthropod assemblages and the ations (Winchester and Ring 1996a, 1996b, systematics of canopy arthropods has increased Stork et al. 1997, Winchester 1997a). In tem­ rapidly during the last 20 years (Stork & Best perate zones some of the last remaining tracts of 1994, Stork et al. 1997) . In general, canopies intact ancient coniferous forests occur in the Pa­ of rainforests contain a large percentage of the cific Northwest of North America (Franklin species present in these forest systems and the 1988) and the "coastal temperate rainforest" of most speciose group is the arthropods (see Stork British Columbia represents approximately 25% et al. 1997). Canopies of natural forests in tem­ of the worldwide coastal temperate rainforests perate (Schowalter 1989, Winchester & Ring (Kellogg 1992). In British Columbia, intact 1996a, 1996b, Behan-Pelletier & Winchester coastal ancient forests are becoming endangered 1998, Winchester 1997a, 1997b) and tropical re­ systems (Winchester 1993, 1997c, Winchester & gions (Erwin 1983, Stork 1988, Basset 1997, Ring 1996a, 1996b) and figures suggest that Didham 1997, Davies et al. 1997, Hammond et 49% by area of "old growth" (vs. 53% "ma­ al. 1997, Kitching et al. 1997) contain largely ture" from satellite imagery) remains as of 1995 undescribed and little understood assemblages (MacKinnon & Eng 1995). Nowhere is the re­ of arthropods that have greatly expanded esti­ duction of ancient forests more apparent than on mates of the total number of insect/arthropod Vancouver Island where during the last 60 years species. In this paper we summarize some of the an increase in logging activities has reduced the patterns of arthropod biodiversity from three number of intact watersheds (>5000 hectares) northern temperate ancient forest sites where re­ so that only 6 of 89 remain (Winchester 1993, search has focused on canopy arthropods. In par­ 1997c, Winchester & Ring 1996a, 1996b). The ticular we discuss observations on guild struc­ ongoing fragmentation of these landscapes has ture and ask the following questions: (1) Does heightened the awareness for a need to under­ guild proportionality vary among sites? (2) Do stand/determine the endemic fauna and flora characteristics of the predator guild vary among sites? In addition we present evidence from the Carmanah Valley canopy suspended soil studies * Corresponding author. to support the hypothesis that ancient forest can- 268 WINCHESTER & RING: CANOPY ARTHROPODS IN TEMPERATE RAINFORESTS 269 FIGURE 1. Map location of the Mt. Cain (1), Upper Carmanah Valley (2), and Rocky Point (3) canopy research sites, Vancouver Island, British Columbia, Canada. opies act as repositories for arthropod biodiver­ canopy sites and details of our sampling proce­ sity. dures can be found in: Winchester (1997a, 1997b), Carmanah Valley, and Winchester and Fagan (in press) Mt. Cain. Sampling procedures METHODS AND MATERIALS used at Rocky Point follow the protocols out­ We have been sampling selected ancient rain­ lined by Winchester (1997a, 1997b) for the Car­ forests on Vancouver Island, British Columbia, manah Valley. Canada, since 1992 with most of our work fo­ cused on the Carmanah Valley. However, we Sample Sorting and Data Analyses have added four sites that encompass a range of forest types covering a wide geographic range on Vancouver Island (FIGURE 1). For the pur­ Guilds poses of this paper we will focus on three sites; All insects were removed from each branch Mt. Cain, Carmanah Valley and Rocky Point sample and prepared for identification. An in­ (FIGURE 1). formative view of canopy arthropods can be At each site we have carried out basic arthro­ gained by placing them in guilds defined in pod inventories with a variety of sampling tech­ terms of feeding habits. The guilds used in this niques. Data used in guild analyses were gath­ study were structured after work by Root (1967, ered using a branch clipping program. Resident 1973) and further elaborated upon by Moran and microarthropods were collected from suspended Southwood (1982) and Stork (1987). The six soils using a hand held moss/soil corer and ex­ guilds recognized in this study were: phytopha­ tracted using Tullgren funnels. ges, epiphyte fauna, scavengers, predators, par­ The characteristics of our northern temperate asitoids, and tourists. All arthropods except the 270 SELBYANA Volume 20(2) 1999 TABLE 1. Means of percentage of arthropod individ­ TABLE 3. Comparison of the number of families, gen­ uals recorded from three samples sites (tree, time era, species and individuals of arachnids from for­ and height are pooled), arranged by guild. N est canopies of three coniferous rainforest types scores are the number of branch samples collected on Vancouver Island, British Columbia, Canada. from each of four tree species (AA = Abies ama­ bilis, TH = Tsuga heterophylla, SS = Picea sitch­ Fami- Gen- Spe- Indivi· ensis, PM = Pseudotsuga menziesii). Site Zone lies era des duals Mt. Cain CWHvm2 10 16 25 344 Rocky Mt. Mt. Carmanah CWH 10 12 18 313 Cain Cain Carmanah Point 19 1269 Guild (AA) (TH) (SS) (PM) Rocky Point CDFmm 9 13 Predators 46.7 42.2 37.2 38.7 Phytophages 6.2 18.3 41.3 12.7 Parasitoids 3.2 0.3 11.8 4.0 viduals/kg dried plant material for all individuals Epiphyte fauna 0.0 0.0 8.3 1.2 for each study site from the branch-clipping Scavengers 9.9 12.0 1.0 10.1 sampling program are presented in TABLE 1. The Tourists 5.5 10.6 0.4 7.6 emerging pattern of high predator loading is consistent across all sites and supports the pre­ viously published data for the Carmanah (Win­ Acarina and Collembola collected from the chester 1997a). Predator guild proportions in our branch-clippings were identified to family and studies are higher than those reported by Moran arranged by guild. Guilds were expressed as a and Southwood (1982) and Stork (1987). Nu­ percentage of total individuals pooled over all merical dominance of functional groups in this sample parameters. study supports the previous findings from decid­ The predator guild is mainly composed of uous forests by Schowalter and Crossley (1987) arachnids (Araneae) and was divided into six and coniferous forests by Schowalter (1989). sub-guilds based on species foraging strategy The number of spider families and species rich­ similarities. Web builders were divided into cat­ ness are similar in each study site (TABLE 2) and egories of spiders with similar web characteris­ this trend is also evident when comparing the tics, including permanent webs, daily webs and arachnid canopy community (TABLE 3). Numer­ sheet webs. Hunting spiders included arboreal ical dominance of spiders has been reported hunters, fast hunters and jumping hunters. from other temperate studies (Nielsen 1975, Total arachnid composition was compared for Ohmart & Voigt 1981, Voegtlin 1982). The each site and arboreal spiders collected from the maintenance of high predator loading in a struc­ branch clipping samples were tabulated. turally and functionally diverse ecosystem such as the Carmanah Valley supports previous find­ Suspended soils ings by Kareiva (1983), Risch (1981) and Oribatid species composition from trap type Schowalter (1986, 1989). Despite similarities in (moss/soil cores and Malaise traps) for all sites spider richness between sites, spider communi­ in the Carmanah Valley were tabulated and ex­ ties are dissimilar (TABLE 4). These results agree pressed in a similarity figure. somewhat with those reported by Halaj et al. (1998) where spider communities on different conifer species were found to be similar, but dif­ GENERAL DISCUSSION ferences in community structure were noted for Canopy Guild Structure Relative abundances of different guilds, ex­ TABLE 4. Percentage of arachnid individuals recorded from each of three sample sites (all factors pressed as percentage of mean number of indi- pooled), arranged by functional group. Rocky TABLE 2. Comparison of the number of families, gen- Sub·guild Mt. Cain Carmanah Point era, species and individuals of arachnids from three coniferous rainforest types on Vancouver Is- Web builders land, British Columbia, Canada. Permanent web 10.7 9.3 15.4 Daily web 16.7 1.1 2.1 Fami- Gen- Spe- Indivi- Sheet web 24.3 35.7 57.3 Site Zone lies era cies duals Active hunters Mt.