| BEN |
| BOTANICAL ELECTRONIC NEWS |
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| ISSN 1188-603X |
| No. 328 April 30, 2004 | aceska@victoria.tc.ca | Victoria, B.C. |
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Troms, Norway, 2-6 June 2004
Web site: http://www.geobotany.uaf.edu/cavm_workshop_2004.html
E-mail contact: Christine Martin [fncrm@uaf.edu]
SCOPE: The conference will focus on issues related to classification, mapping, and modeling of vegetation in Arctic tundra regions. The last major gathering of Arctic vegetation scientists was at the International Conference on Classification of Arctic Vegetation, held at the Institute of Arctic and Alpine Research, Boulder CO, USA, 5-9 March 1992. Since then there has been considerable progress toward classification and mapping as a means of understanding the Arctic as a single geo-ecosystem, and to aid in numerous efforts to model the response of vegetation to climate and land-use changes.
The classification portion of the conference will be primarily devoted to vegetation surveys of syntaxa or monographs on special areas or regions of the Arctic. Floristic and taxonomic papers might be accepted if they are directly of importance to vegetation science.
The mapping portion will focus on circumpolar and large-regional scale mapping efforts. Papers directed at circumpolar issues are particularly welcome. Members of the Circumpolar Arctic Vegetation Mapping (CAVM) project are encouraged to present regional maps derived from the CAVM at 1:4M scale with legends that show the dominant plant associations or plant community types.
Throughout the Pacific Rim, the yearly migration of anadromous salmon provides a pulse of nutrients for a diverse range of marine, freshwater and terrestrial organisms. Jeff Cederholm from the Washington compiled literature on marine food web interactions and noted that at least 130 species of vertebrates use migrating salmon as a food source (Cederholm et al. 2002). John Stockner, Ken Ashley and colleagues from Vancouver and Mark Wipfli and colleagues from Alaska have shown major increases in primary and secondary productivity in stream habitats from the contribution of salmon carcasses to the stream channels (Wipfli et al. 1998; review in Stockner and Ashley 2003). At river mouths from California, Oregon, Washington, British Columbia and Alaska, black bears and brown bears congregate during autumn migration and forage on salmon, acquiring some 70% of their annual protein consumption during this short period (Reimchen 1992, 1994, 2000; Gilbert and Lanner 1995; Hilderbrand et al. 1999). Coastal wolves shift from their major diet of deer in summer to that of salmon during the spawning migration (Darimont and Reimchen 2002). Numerous birds including eagles, gulls, ravens and crows also exploit the salmon nutrients. This seasonal pulse of marine nutrients is spatially and temporally associated with a major increase in diversity and abundance of animals throughout the west coast of North America.
These investigations parallel several other research programs by colleagues at UBC and at US institutions including those in Alaska and Washington but our lab has focused on identifying the contributions of salmon nutrients to the multiple trophic levels within terrestrial habitats. During an investigation of black bear feeding activity in the autumns of 1992, 1993 and 1994 on the south end of Haida Gwaii, I observed individual bears carrying salmon from the stream into the forest where feeding could occur without interference from other bears. Over the eight-week spawning period, each bear transferred up to 700 salmon into the forest leaving remnants of each carcass on the forest floor (Reimchen 1994, 1998, 2000). Most of this foraging occurred during darkness, and by the end of the spawning period, over 5000kg of carcass remnants had accumulated in a 50 m band over the kilometer of stream where spawning occurred. These abandoned tissues were used by a wide diversity of scavengers including gulls, eagles, ravens, crows and marten as well as by large quantities of invertebrates of which fly maggots were the most abundant. While collecting this information on carcasses in old growth forest adjacent to the salmon stream, I suspected that the prevalence of decomposing carcasses as well as the waste products from bears and other scavengers would provide a nutrient source for vegetation. These early observations became the focus for a greatly expanded research program in my lab funded primarily by the David Suzuki Foundation and the Friends of Ecological Reserves which now entails studies from 120 watersheds extending from Clayoquot Sound on Vancouver Island to the coastal mainland near the Broughton Archipelago north to the grizzly bear sanctuary at the Khutzeymateen River on the northern end of the province and across to Haida Gwaii. Throughout the BC coast, black bears and brown bears transfer carcasses into the forest, occasionally to distances of 150 m away from the stream, particularly on steep gradient slopes. We are quantifying the contribution of salmon nutrients at multiple levels of the terrestrial ecosystem including bryophytes, herbs, shrubs and conifers, soil and canopy invertebrates including insects, and to vertebrates such as songbirds, black bear, grizzly bear and wolves (general description of this research, graduate projects and pdf files of publications are available at http://web.uvic.ca/)
The major natural historical observation to emerge from our studies throughout the coast, and one that is familiar to all coastal First Nations, is that the diversity of predators and scavengers that congregate in estuaries and rivers during spawning migration is directly related to the density of salmon in the river. On the British Columbia mid-coast, highly productive rivers have salmon spawning density as high as 50,000 per kilometer of river and associated with these salmon are congregations of up to 10 wolves, 15 bears, 50 bald eagles, 100's of crows and ravens, up to 4000 gulls and numerous song birds. For each of these taxa, it is largely the spawned-out salmon carcasses that provide the major food source over a two-month period. Blowflies are the major consumers of the carcass remnants. Usually within three to four days after abandonment by the bears, the carcasses are a mass of maggots. The entire soft tissues will be consumed within a week after which the maggots disperse onto the surrounding substrate and bury into the surface mosses. Maggot densities in the moss substrate commonly reach 100 /m2. One of my graduate students, Morgan Hocking, has found that the majority of adult blow flies collected in riparian forests in spring and summer have major isotopic enrichment in 15N and 13C signatures, confirming their trophic origin from salmon carcasses the previous autumn. Hocking has also sampled other invertebrate taxa including earthworms, beetles and spiders from multiple trophic levels from habitats above and below waterfalls and observed major enrichment of 15N below the falls compared with above the falls. The extent of 15N enrichment was greatest at higher trophic levels. This was not due to direct consumption of salmon carcasses but rather due to indirect consumption from salmon-derived nitrogen subsidies to litter, soil and vegetation N pools. (Hocking and Reimchen 2002) The total nitrogen in the invertebrates could be partitioned to source and these results showed that 18-78% of nitrogen was originally derived from salmon, with specific levels depending on species and watershed. Total biomass of insects is up to an order of magnitude higher in forests adjacent to salmon spawning areas relative to riparian forests without access to salmon. Another graduate student, Katie Christie, has now shown that songbirds are more abundant in forests adjacent to salmon spawning areas and have major enrichment in 15N isotopic signatures during the late summer derived from consumption of blowflies as well as higher trophic levels invertebrate predators such as spiders. Research by other members of our lab including Chris Darimont who is investigating coastal wolves has demonstrated that samples of hair yield very clear evidence for a seasonal shift in diet from terrestrial prey to salmon (Darimont and Reimchen 2002). Another lab member, Dan Klinka, is investigating the salmon foraging activity of Kermode bear as a comparison with earlier work on brown bear (Klinka and Reimchen 2000).
One of the surprising results from our studies is the extent of salmon nutrient uptake by riparian vegetation. Mosses and liverworts comprise the dominant ground cover throughout temperate rainforest ecosystems in the North Pacific Rim and these are essential to numerous edaphic processes including temperature regulation and moisture retention. Bryophytes commonly absorb nutrients from precipitation and canopy through fall as well as from underlying soils and N-fixers. Our lab, in particular Chad Wilkinson, has investigated the contribution of salmon- derived nitrogen to eight species of mosses and liverworts (Rhytidiadelphus loreus, Hylocomium splendens, Sphagnum girgensohnii, S. squarrosum, Rhizomnium glabrescens, Kindbergia oregana, Conicephalum conicum and Pellia neesiana) above and below waterfalls that are barriers to salmon migration and at a control river without salmon. Overall, Delta 15N signatures ranged from 2% to 7% higher below the falls near the salmon stream than above the falls or at the adjacent control watershed that had no salmon. Delta 15N values were highest in mosses from sites where salmon bone fragments were present in the substrate, indicative of a carcass transfer during previous years. Isotopic values were also high in mosses adjacent to wildlife trails. We also examined percent nitrogen in the moss tissues as nitrogen is generally considered to be a proxy for photosynthetic rate and is the principal limiting nutrient in temperate forest ecosystems. We observed increased levels of tissue nitrogen below the falls and in sites where salmon carcasses were prevalent indicating microspatial heterogeneity in the salmon nutrient pools of these forests. Moss species richness and prevalence of nitrogen-rich soil indicators were also highest in forests adjacent to the salmon stream (Wilkinson et al. submitted). We have examined the contribution of salmon nutrients to other riparian vegetation including Blechnum spicant, Menziesii ferruginea, Oplopanax horridus, Rubus spectabilis, Vaccinium alaskense, V. parvifolium and Tsuga heterophylla. 15N values were enriched by 1.4% to 9.0% below the falls depending on species and watershed, indicating that 10% to 60% of tissue nitrogen was marine-derived (MDN). As well, %N in foliar tissues was slightly higher below the falls, with the majority of variance occurring between vegetation species. Of interest is that salmonberry, one of the common riparian shrubs, had the highest percent tissue nitrogen of the six most common riparian species (Mathewson et al. 2003; Reimchen et al. 2003). Community structure also differed with higher incidence of nitrogen-rich soil indicator species below the waterfalls.
We have also been able to identify historical signatures of salmon-nutrient loading to the riparian zone through analyses of yearly growth rings taken from cores of ancient trees. This has been approached in two methods 1) a direct measurement of yearly growth rate and 2) analyses of 15N signatures and percent N levels in individual rings. These ongoing studies yield clear evidence for increased average growth of conifers with access to salmon. We tested whether there was a yearly growth signature that correlated with yearly differences in actual salmon counts made by Department of Fisheries over the last 50 years. Some trees show very strong correlations between yearly salmon abundance and tree growth when lagged from 1 to 3 years but most trees nearby show only weak or no such relationships. The same trend occurs with analyses of 15N signatures in the tree rings. Some trees have high lagged correlation between salmon abundance over the last 50 years and 15N levels in the rings yet adjacent trees show no associations. We are currently trying to identify the best habitat predictors for these trees that show excellent tracking between salmon abundance and nitrogen signatures. Currently, I have obtained 1150 cores of ancient trees in 120 watersheds throughout coastal British Columbia and these cores have the potential of yielding a 300-year history of salmon abundance and riparian nutrient loading on our coast.
These investigations are still in their infancy but the emerging data provide a reasonably clear picture of a multi- trophic level linkage between marine and terrestrial ecosystems. When up to 70% of the nitrogen in mosses, herbs, shrubs, ancient trees, canopy insects, songbirds and bears in coastal forests is derived from the central Pacific ocean via the life history of the salmon, the implications of spatial and temporal differences in salmon abundance are substantive. Since 1880, salmon have declined by approximately 80-90% on the west coast of North America due to the combination of over-fishing, large scale commercial logging, dam construction as well as fluctuations in oceanic productivity. What effects if any have there been of this decline and would they be detectable if they did occur? Our studies and those from other labs have found lower levels of estuarine, stream and riparian community diversity in watersheds without access to salmon and these differences are also evident within rivers above waterfalls that are barriers to salmon movement. We have observed that above waterfalls, there are lower species diversity of mosses, lower incidence of nitrogen-rich plant indicator species, lower biomass of insects, lower densities of songbirds and lower growth rate of conifers. This suggests that the estimated 80-90% reduction in salmon abundance throughout the coast will lead to a reduction in carrying capacity and shifts in the plant and animal community structure that converges to that resembling watersheds without access to salmon.
For over thirty years, Hans Roemer's thesis on forest classification on the Saanich Peninsula has been available only as photocopies at the University of Victoria library, on microfilm (e.g., the University of British Columbia library), or as photocopies of photocopies (e.g., Library of the British Columbia Ministry of Forests).
This spring I managed to convince Hans that his thesis is still a relevant source of valuable phytosociological information and he gave his consent to putting his thesis on the British Columbia Ministry of Forests web site as a .pdf file. Rick Scharf and Steve Netherton scanned the original copy and converted it to pdf, and the BC Ministry of Forests library supervisor Roxanne Smith put it on their library web site. Many thanks to all people involved in this project!
Here is the Abstract of Hans Roemer's thesis:
The forest vegetation on the Saanich Peninsula, Vancouver Island, is classified in 7 associations, 12 subsassociations and 20 variants, on the basis of 400 releves. Communities are distinguished by diagnostic species groups, which were derived by computer sorting of vegetation tables (Ceska and Roemer, 1971). The rationale of decisions in the classification process is discussed both in terms of floristic differentiation and numerical similarity.
Detailed descriptions of each community include its physiognomy and life forms, its diagnostic species groups, community statistics and habitat. Extensive vegetation tables form an important part of this work.
Relationships of forest vegetation to environmental factors are considered at the level of single species, species groups and communities. Major habitat variables are correlated with species and species groups through non- parametric statistical methods. The main floristic gradient exhibited in ordered vegetation tables is recognized to be correlated with general moisture conditions. Most other environmental variables appear to coincide with and partly depend on moisture conditions.
Soils, watertables and stand climates are described for subjectively selected stands representative of the communities. Soils are classified on the basis of 40 detailed soil profiles and 150 routine examinations by soil auger. Communities are strongly correlated with morphological types of profiles, but are only partly correlated with soil units of the current Canadian classification. Distinctive watertable types are found for the moist-site communities. Important differences are shown in maximum water levels, duration of high water levels, and range of watertable fluctuation for three major communities. Prediction of watertable conditions according to species composition is proposed.
Succession and climax are discussed. The forest community on mesic sites is the Pseudotsuga-Berberis association on Orthic Dystric Brunisols. Communities of the driest sites are the Quercus-Erythronium and the Arbutus-Pseudotsuga associations, those on wettest sites the Alnus-Athyrium and Populus-Pyrus associations. The former occur on Lithic Sombric and Lithic Dystric Brunisols, and the latter on Organic soils and Gleysols. Only fragments of the Pinus contorta bog forest remain.
A reconstruction of the pattern of the original forest communities is attempted for valley sites now under agricultural use. The evaluation of an open, park-like landscape in the Quercus vegetation complex is interpreted as a combined result of subregional climate, microclimate and early human history.