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Floristics and Distribution Patterns of Lichens and Bryophytes in Microbiotic Crusts of British Columbia’s Ponderosa Pine Forests Patrick Williston Department of Botany, University of British Columbia 3529 - 6270 University Boulevard, Vancouver, BC, V6T 1Z4, Canada [email protected] ABSTRACT Microbiotic crusts are an important though often overlooked component of the biodiversity and ecology of arid and semiarid ecosystems. This study lists 51 terricolous lichens and 39 terricolous bryophytes of microbiotic crusts in British Columbia’s semiarid ponderosa pine (Pinus ponderosa) forests. The list is the first to document the terricolous lichens of these forests, and adds 14 species to previous reports of the bryophytes. This study also describes successional patterns, following grazing disturbance, of invasive nonnative vascular plants, 3 native grasses, and 3 microbiotic crust species. An understanding of successional patterns is essential for managing the biodiversity of British Columbia’s ponderosa pine forests, one of the most restricted ecosystems in the province. Key words: bryophyte, lichen, microbiotic crust, Pinus ponderosa, ponderosa pine. BACKGROUND Microbiotic crusts, also called cryptogamic, cryptobiotic, microphytic, biologic, and microfloral crusts, are an important component of the biodiversity and ecology of arid and semiarid ecosystems. Unfortunately, they are also often overlooked in ecological studies and vegetation inventories. Microbiotic crusts are assemblages of bryophytes, lichens, algae, fungi, bacteria, and cyanobacteria that integrate with the soil surface of arid and semiarid ecosystems. While earlier studies have reported the common bryophytes in ponderosa pine (Pinus ponderosa) forests of British Columbia, little work has been conducted to date on the lichens, algae, fungi, bacteria, and cyanobacteria occurring in this ecosystem (Schofield 1988). This study adds to existing lists of the bryophytes of ponderosa pine forests and is the first to report the common terrestrial lichens in these ecosystems. Inquiry into the ecological functions of microbiotic crusts derives from studies conducted in the United States and Australia (West 1990; Eldridge 1993, 1996; Harper and Pendelton 1993; Belnap 1994; Eldridge and Greene 1994; Eldridge and Tozer 1996; Eldridge et al. 1997). In these regions, microbiotic crusts have been shown to influence nitrogen balance, water infiltration and retention, and water and wind erosion in grassland ecosystems (West 1990, Eldridge 1993, Harper and Pendleton 1993). Recent research in the grasslands of the Okanagan Valley of British Columbia determined that microbiotic crusts have a significant effect on water retention after rain events (Atwood 1998). Few studies have examined successional patterns in crust communities (Looman 1964). The research presented here is the first to describe patterns of succession in British Columbia’s ponderosa pine forests. MICROBIOTIC CRUSTS Despite the rich diversity of bryophytes and lichens in the semiarid interior of British Columbia, our understanding of its flora and ecology is rudimentary. McIntosh (1986, 1997) conducted the most complete survey of the bryophytes of British Columbia’s grasslands in a thesis that included a key to grassland bryophytes and reported several species new to the province. While his study did not include ponderosa pine ecosystems, several of the species overlap from the grasslands to the ponderosa pine forests. Schofield (1988) reported species belonging to ponderosa pine forests in a general survey of the biogeoclimatic zones of British Columbia. The present study adds 14 species to the existing list and provides insights into the ecology of 1 dominant bryophyte. Lichens have been the focus of intensive investigation in 4 regions of the province: the coastal Douglas-fir zone (Noble 1982), the Queen Charlotte Islands (Brodo 1995), and wet coastal and interior ecosystems (Goward and Thor 1992, Goward et al. 1994, 1996). This research lists the terrestrial lichens from 19 ponderosa pine study sites and discusses successional patterns of 2 common lichens, Cladonia pyxidata and C. chlorophaea. Efforts to describe crust communities have been more thorough in the Great Basin region of the United States (St. Clair et al. 1993). While several species from the Great Basin are shared with the British Columbia flora, genera such as Cladonia appear to increase L. M. Darling, editor. 2000. Proceedings of a Conference on the Biology and Management of Species and Habitats at Risk, Kamloops, B.C., 15 - 19 Feb.,1999. Volume Two. B.C. Ministry of Environment, Lands and Parks, Victoria, B.C. and University College of the Cariboo, Kamloops, B.C. 520pp. 769 WILLISTON in diversity and cover with latitude, making British Columbia’s flora unique (Goward and Ahti 1997). PONDEROSA PINE FORESTS British Columbia’s ponderosa pine forests are restricted to the lowlands and low slopes of the driest valleys in the southcentral and southeastern regions of the province. The mean annual rainfall is 280–500 mm (Meidinger and Pojar 1991). These forests are characterized by hot, dry summers and cool winters with little snowfall (Meidinger and Pojar 1991). The canopy is comprised of broadly spaced ponderosa pine, with Douglas-fir (Pseudotsuga menziesii) appearing in draws and wetter areas. The understory vegetation is dominated by the perennial bunchgrasses Festuca campestris and Elymus spicata, and includes a diverse array of forbs and shrubs. Historically, these forests were subject to natural periodic fires; however, grazing has since replaced fire as the primary source of disturbance, resulting in an increase in the dominance of early-successional vegetation. Turf-forming Poa pratensis and the annual Bromus tectorum, both of which are aggressive, nonnative graminoids, have replaced native perennial bunchgrasses in areas of heavy disturbance (Daubenmire 1968, 1970). Indeed, ponderosa pine forests in a natural condition are rare in British Columbia—a conservation issue worthy of concern. METHODS STUDY AREA The study was conducted along a glacial lake-bed terrace east of Kamloops, B.C. The sites were oriented along an 18-kmlong east/west transect on the south side of the South Thompson River. The elevation ranged between 500 and 600 m, and slopes remained between 2 and 15%, with a north aspect. Sites represented early (E), mid (F), late (L), and natural (P) seral stages and were restricted to a zonal position in the Ponderosa Pine biogeoclimatic zone (Lloyd et al. 1990). Site history and the condition and composition of the dominant vegetation were used to determine seral stages. Five sites were sampled at each seral stage except the mid-seral stage, which was sampled at 4 sites. In total there were 19 sites. SAMPLING Fieldwork was conducted using a frame with 10 precise sampling points. The frame was positioned at random intervals along 5 50-m transects on a 40-m baseline. Each transect was sampled with 10 placements of the sampling frame to yield 100 points per transect. These points were used to determine the percent cover of vascular plants and microbiotic crust species. Crust specimens were curated as described by Rosentreter et al. (1988). 770 RESULTS AND DISCUSSION BRYOPHYTE AND LICHEN SURVEY Table 1 lists the terricolous bryophytes and lichens observed while conducting this research, including 14 species of terrestrial bryophytes not previously reported for the ponderosa pine forests of British Columbia (Schofield 1988). This list includes those species observed in the study area and does not constitute a complete survey of the ponderosa pine forest ecosystem. Voucher specimens of these species are located at the University of British Columbia herbarium and the British Columbia Ministry of Forests, Range Branch in Victoria. Williston (1999) provides an illustrated key to the common bryophytes and lichens of the ponderosa pine forests and associated grasslands of British Columbia. VASCULAR PLANTS The successional transition of forested grassland ecosystems from nonnative annual grasses to native bunchgrasses in the British Columbia Interior has been previously described (McLean and Marchand 1968). This study builds upon existing knowledge by examining some of the ecological effects of these species’ distributions and vegetation structure changes. Early successional vegetation is comprised of native and nonnative annual grasses with a high cover of the native perennial Stipa comata (Figs. 1 and 2). Over time, the cover of S. comata and nonnative grasses decreases and the cover of large native perennial bunchgrasses such as Festuca campestris and Elymus spicata increases (Figs. 3 and 4). The shrub Artemesia tridentata, a species known to be unpalatable to cattle (the primary nonnative agent of disturbance in this ecosystem), increases in cover under intensive grazing management strategies (Daubenmire 1970). A. tridentata provides shade in early seral sites; however, the chemistry of its litter differs from that of the bunchgrasses. This is reflected in the distribution patterns of microbiotic crust species, which suggest that some late successional species, such as Brachythecium albicans, are able to colonize under the cover of A. tridentata, while others are not (Fig. 7). MICROBIOTIC CRUST SPECIES Cladonia pyxidata is 1 of the most common crust species in the ponderosa pine forests of British Columbia. This species increases in cover in the mid-seral stage and then decreases with succession (Fig. 5). C. pyxidata is a soil colonizer and is able to utilize soil substrata created by natural and humancaused disturbances. An increase in substratum availability in the mid-seral stage probably accounts for the greater cover of C. pyxidata. Cladonia chlorophaea is most commonly found beneath the grass litter of native perennial bunchgrasses such as Festuca campestris and Elymus spicata. It is not surprising that this species increases in cover in later seral stages where bunchgrasses dominate the understory (Fig. 6). Proc. Biology and Management of Species and Habitats at Risk, Kamloops, B.C., 15–19 Feb. 1999. Microbiotic Crusts of Ponderosa Pine Forests Table 1. A list of the terricolous bryophytes and lichens from the study area in the ponderosa pine forests of the southern interior of British Columbia. Liverworts Barbilophozia hatcheri (Evans) Loeske* Cephaloziella divaricata (Sm.) Schiffn. Lophozia excisa (Dicks.) Dum.* Ptilidium ciliare (L.) Hampe* Ptilidium pulcherrimum (G. Web.) Hampe* Mosses Aloina brevirostris (Hook & Grev.) Kindb. Barbula convoluta Hedw. Brachythecium albicans (Hedw.) Shimp. in B.S.G. Brachythecium collinum (Schleich. ex C. Mull.) Shimp. in B.S.G. Bryum argenteum Hedw. Bryum caespiticium Hedw. Buxbaumia aphylla Hedw.* Ceratodon purpureus (Hedw.) Brid. Desmatodon convolutus (Brid.) Grout Dicranum polysetum Sw.* Dicranum scoparium Hedw. Didymodon vinealis (Brid.) Zander Ditrichum flexicaule (Swaegr.) Hampe* Encalypta rhaptocarpa Schwaegr.* Encalypta vulgaris Hedw.* Fissidens bryoides Hedw.* Funaria hygrometrica Hedw. Homalothecium aeneum (Mitt.) Lawt. Hylocomium splendens (Hedw.) B.S.G. Hypnum revolutum (Mitt.) Lindb. Hypnum vaucheri Lesq. Mnium spinulosum B.S.G.* Phascum cuspidatum Hedw. Pohlia nutans (Hedw.) Lindb. Polytrichum juniperinum Hedw. Polytrichum piliferum Hedw. Pseudoleskeella tectorum (Brid.) Broth. Pterygoneurum subsessile (Brid.) Jur. Pterygoneurum ovatum (Hedw.) Dix. Rhytidiadelphus triquetrus (Hedw.) Warnst. Rhytidiopsis robusta (Hedw.) Broth.* Sanionia uncinatus Loeske* Tortula ruralis (Hedw.) Gaertn. et al. Weissia hedwigii Crum* Lichens Acarospora schleircheri (Ach.) A. Massal. Amandinea punctata (Hoffm.) Coppins & Scheid Arthonia glebosa Tuck. Bryonora castanea (Hepp) Poelt Buellia geophilla (Florke ex Sommerf.) Lynge Caloplaca jungermanniae (Vahl) Th. Fr. Caloplaca tominii Savicz Candelariella terrigena Rasanen Catapyrenium squamulosum (Ach.) Bruess Cetraria ericetorum Opi Cladina arbuscula (Wallr.) Hale & Culb. Cladina mitis (Sandst.) Hustich Cladina rangiferina (L.) Nyl. Cladonia borealis S. Stenroos Cladonia botrytes (K. Hagen) Willd. Cladonia cenotea (Ach.) Schraerer Cladonia cervicornis (Ach.) Flot. Cladonia chlorophaea (Florke ex Sommerf.) Spreng. Cladonia cornuta (L.) Hoffm. Cladonia ecmocyna Leighton Cladonia fimbriata (L.) Fr. Cladonia gracilis (L.) Willd. Cladonia mulitformis G. Merr. Cladonia phyllophora Hoffm. Cladonia pocillum (Ach.) Grognot Cladonia pyxidata (L.) Hoffm. Cladonia rei Schraerer Cladonia subulata (L.) F. H. Wigg. Cladonia sulphurina (Michaux) Fr. Cladonia symphycarpa (Florke) Fr. Collema tenax var. crustaceum (Kremp.) Degel. Diploschistes muscorum (Scoop) R. Scant Endocarpon pusillum Hedw. Leptogium sp. Nephroma parile (Ach.) Ach. Ochrolechia upsaliensis (L.) A. Massal. Peltigera canina (L.) Willd. Peltigera didactyla (With.) Laundon Peltigera didactyla var. extenuata (Nyl.) Goffinet & Hastings Peltigera lepidophora (Vainio) Bitter Peltigera malacea (Ach.) Funck Peltigera ponojensis Gyel. Peltigera rufescens (Weis) Humb. Physconia muscigena (Ach.) Poelt Placynthiella uliginosa (Schrader) Coppins & P. James Polychidium muscicola (Sw.) Gray Psora cerebriformis W. A. Weber Psora globifera (Ach.) A. Massal. Psora montana Timdal Stereocaulon sp. Xanthoria wyomingica (Gyel.) Hale * Denotes species added to reported lists of bryophytes of British Columbia’s ponderosa pine forests. Proc. Biology and Management of Species and Habitats at Risk, Kamloops, B.C., 15–19 Feb. 1999. 771 WILLISTON Figure 1. Percent cover of invasive, nonnative vascular plants over 4 successional stages: early (E), mid (F), late (L), and natural (P). Cover is the mean per transect. Figure 2. Percent cover of Stipa comata over 4 successional stages, as described in Figure 1. Figure 3. Percent cover of Festuca campestris over 4 successional stages, as described in Figure 1. Figure 4. Percent Cover of Elymus spicata over 4 successional stages, as described in Figure 1. 772 Proc. Biology and Management of Species and Habitats at Risk, Kamloops, B.C., 15–19 Feb. 1999. Microbiotic Crusts of Ponderosa Pine Forests Figure 5. Percent cover of Cladonia pyxidata over 4 successional stages, as described in Figure 1. Figure 6. Percent cover of Cladonia chlorophaea over 4 successional stages, as described in Figure 1. Brachythecium albicans is most abundant in partially shaded microsites. In most stages, this pleurocarpous bryophyte is common in needle litter beneath ponderosa pine. In early seral stages it is also under Artemesia tridentata, while in the natural condition, where its cover is greatest, it occurs under the cover of bunchgrasses (Fig. 7). CONCLUSIONS Figure 7. Percent cover of Brachythecium albicans over 4 successional stages. Proc. Biology and Management of Species and Habitats at Risk, Kamloops, B.C., 15–19 Feb. 1999. This study lists 51 terricolous lichens and 39 terricolous bryophytes known to occur in British Columbia’s ponderosa pine forests. This list represents the first for the lichens of this ecosystem and adds 14 species to previous reports of the bryophytes. Trends in the cover of vascular plants, bryophytes, and lichens suggest the following patterns with succession: 1) nonnative vascular plants decrease; 2) Stipa comata and Cladonia pyxidata have the greatest cover in the mid-seral stage and then decrease; 3) the large, native, perennial bunchgrasses Festuca campestris and Elymus spicata, and the lichen Cladonia chlorophaea increase; and 4) the pleurocarpous bryophyte Brachythecium albicans decreases in the mid-seral stage and has its greatest cover in the natural condition. Analysis suggests that the surface vegetation in ponderosa pine ecosystems is composed of a dynamic community of vascular and nonvascular organisms with discernible early 773 WILLISTON and late successional species. By examining the patterns of vascular plants and microbiotic crust species it is possible to determine which seral stage a site is in. Evaluating seral development is essential to managing rangelands for an array of successional stages, and for protecting representative areas that are in a natural condition. Research in progress will elaborate on relationships between microbiotic crust species and successional patterns in this ecosystem. ACKNOWLEDGEMENTS Thanks to: G. Bradfield, research design, statistics, manuscript review, and supervising; M. Fairbarns, research design and logistics; S. Ford, logistics; G. Hayes, logistics; T. Goward, taxonomic consultation and manuscript review; K. Johnston, fieldwork; T. McIntosh, taxonomic consultation; T. Redding, logistics; K. Sadler, manuscript review; R. Tucker, research design and site selection; C. Wulff, manuscript review; and W. Zhang, statistics and manuscript review. Financial support was provided by the British Columbia Ministry of Forests, Range Branch. LITERATURE CITED Atwood, L. 1998. Ecology of the microbiotic crust of the antelope-brush (Purshia tridentata) shrub steppe of the south Okanagan, British Columbia. M.Sc. thesis, Univ. British Columbia, Vancouver, BC. Belnap, J. 1994. Potential role of cryptobiotic soil crusts in semiarid rangelands. Pp. 179–185 in S. B. Monsen, and S. G. Kitchen, eds. Proc. Ecology and management of annual rangelands. U.S. Dep. Agric. For. Serv., Boise, ID. Intermountain Res. Stn. Brodo, I. M. 1995. Lichen and lichenicolous fungi of the Queen Charlotte Islands, British Columbia, Canada. I. Introduction and new records for British Columbia, Canada, and North America. Mycotaxon 56:135–173. Daubenmire, R. 1968. Plant communities: a textbook of plant synecology. Harper and Row, New York, NY. _____. 1970. Steppe vegetation of Washington. Washington Agric. Exp. Stn., Pullman, WA. Tech. Bull. 62. 131 pp. Eldridge, D. 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Great Basin Nat. 53:5–12. West, N. E. 1990. Structure and function of microphytic soil crusts in wildland ecosystems of arid and semi-arid regions. Adv. in Ecol. Res. 20:179–223. Williston, P. 1999. Floristics and successional patterns of microbiotic crusts in ponderosa pine forests of southern inland British Columbia. M.Sc. thesis. Univ. British Columbia, Vancouver, BC. 115 pp. Proc. Biology and Management of Species and Habitats at Risk, Kamloops, B.C., 15–19 Feb. 1999.