Abstracts Vol. 34, No. 2, May 2002 Spatial and Temporal Changes in Sedimentary Processes at Proglacial Bear Lake, Devon Island, Nunavut, Canada (pp 119-129) Ted Lewis, Robert Gilbert, and Scott F. Lamoureux Lacustrine sedimentary processes are identified on an intra-annual scale at proglacial Bear Lake, Devon Island. Stage recorders, recording thermistors, sediment traps, and underflow monitoring equipment were deployed during the 1999 melt season. Episodic proximal turbidity currents were measured as positive near-bottom temperature anomalies and currents. The timing of individual positive temperature anomalies was clearly associated with diurnal peaks of discharge into the lake. During the period of 23 to 25 July, continuous underflow occurred, which preceded a large discharge event by about 24 h. Sediment traps placed throughout the lake recorded sediment accumulation rates from 16 June to 4 August. An extremely large precipitation event occurred on 29 June, when coarse, carbonate-rich sediment was deposited in front of a secondary tributary by spatially limited turbidity currents. A niveo-eolian deposit was observed on the lake ice, and sediment traps were deployed under this area. Mass accumulation rates in these traps locally overwhelmed fluvially generated sedimentation. This sediment was dominantly sand, which quickly melted through the lake ice and hastened the date of localized break-up. Lacustrine Sedimentary Environments in High Arctic Proglacial Bear Lake, Devon Island, Nunavut, Canada (pp 130-141) Scott F. Lamoureux, Robert Gilbert, and Ted Lewis Combined catchment, subbottom acoustic, and sedimentary studies of high arctic, proglacial Bear Lake, Devon Island, were carried out to evaluate the role lacustrine processes and Holocene catchment evolution have had on the sedimentary record. In the proximal basin, bottom deposits up to 60 m thick are generated in partby turbid underflows associated with peak meltwater flow from the Devon Island Ice Cap. These underflows produce rhythmically laminated structures that are likely varves. In shallower locations, accumulation is slower and results from homopycnal distribution of fine suspended sediment throughout the proximal basin, resulting in a simple varve couplet. The distal basin is isolated from glacial meltwater by a shallow sill, although some fine-grained detrital carbonate transported by the glacial meltwater is deposited in both basins. In most locations in the distal basin Holocene sediments are less than 10 m thick. They are composed primarily of massive clay and some carbonate interrupted by irregular graded carbonate units produced by sporadic heavy summer rainfall and sediment transport from small plateau tributaries. Eolian sedimentation is also important throughout the lake, especially when high accumulations melt through the ice in the proximal basin, producing isolated grains and layers of coarse sand in the sedimentary record. Holocene ice margin changes have influenced the sedimentary record substantially, particularly during the mid-Holocene when the ice cap is inferred to have retreated from the catchment. Hydrology of Active Rock Glaciers: Examples from the Austrian Alps (pp 142-149) Karl Krainer and Wolfram Mostler Hydrological investigations of three active rock glaciers in the Austrian Alps (Reichenkar rock glacier in the western Stubai Alps, Kaiserberg rock glacier in the western Ötztal Alps, and Gößnitz rock glacier in the Schobergruppe) demonstrate that discharge is mainly controlled by the local weather conditions, the thermal properties of the debris layer, and the physical mechanisms that control the flow of meltwater through the rock glacier. Discharge of active rock glaciers is characterized by strong seasonal and diurnal variations. Water derived from snowmelt and summer thunderstorms is quickly released causing floods. Fair weather periods with intense melting of snow and ice cause pronounced diurnal variations in discharge. Water temperature of active rock glacier springs is constantly below 1°C during the whole melt season. Electrical conductivity of the water is low during high discharges due to high amounts of meltwater derived from snow/icemelt and/or precipitation, and high during cold weather periods and in autumn when discharge is very low and consists mainly of groundwater. The discharge pattern of active rock glaciers is similar to that of glaciers due to similar meltwater sources and flow paths. However, the average yearly mean specific discharge from active rock glaciers is significantly lower than that of glaciers. Ice Formation in an Antarctic Glacier-dammed Lake and Implications for Glacier-Lake Interactions (pp 150-158) R. Lorrain, S. Sleewaegen, S. Fitzsimons, and M. Stiévenard Perennially frozen lakes are common features in the McMurdo Dry Valleys of South Victoria Land in Antarctica. Some of them, called wet based, contain liquid water capped by a permanent ice cover between 2.5 and 6 m in thickness. The others, called dry based, are ice-block lakes. The thickness of the latter may far exceed those of the former. Their level is rising from freezing of the surface flooding of summer meltwater. However, we show here for the first time, using isotopic analyses together with an ionic and gas content and composition study, that the ice of one of these dry-based lakes has been formed by complete freezing from top to bottom of a closed water reservoir and not by successive layers of icings (aufeis) piling on top of each other. We also show how this lake, dammed by a cold-based glacier, has contributed to the formation of the basal ice layer of this glacier. Population Age Structure of Nematodes in the Antarctic Dry Valleys: Perspectives on Time, Space, and Habitat Suitability (pp 159-168) Dorota L. Porazinska, Diana H. Wall, and Ross A. Virginia Patterns of nematode population dynamics in an extreme environment were studies in the McMurdo Dry Valleys of Antarctica. Nematode populations are sensitive to soil disturbance and are useful indicators of environmental change. We hypothesized that the pristine soil environments of Antarctica that are suitable for life would support stable both spatially and temporally nematode populations. We established three sampling sites across an elevation gradient in Taylor Valley and sampled each site at larger and smaller spatial scales three-times over a 6-yr period (1993, 1995, and 1999). Nematode variables and soil moisture were significantly different among years. Soil moisture, nematode abundance, and life cycle parameters varied also with elevation, but not spatial scale at the grid size over the 6 yr. Generally, soil moisture declined during the time of the study and was greatest at the lowest elevation. Throughout the 6 yr, Scottnema lindsayae was most abundant at the highest elevation and dominated all sites, while Eudorylaimus antarcticus was most abundant at the lowest elevation. Plectus antarcticus was present only at the lowest elevation. While Scottnema was negatively correlated with soil moisture, Eudorylaimus and Plectus showed a positive relationship. Similarities among nematode species in life cycle characteristics (e.g., long life cycles and low reproductive rates) may indicate adaptive strategy for survival in the Dry Valley soil environments. The differences, however, may indicate species specific sensitivity to changes in the soil characteristics such as moisture. Temporal variation of variables describing nematode populations in Antarctic soil suggests the nematode species respond to short-term climate variation and, thus, may be affected by long-term climate change. A Classification of Subantarctic Heard Island Vegetation (pp 169-177) Dana M. Bergstrom, Jennie Whinam, and Lee Belbin The vascular and bryophyte floras of subantarctic Heard Island were classified using cluster analysis into six vegetation communities: Open Cushion Carpet, Mossy Feldmark, Wet Mixed Herbfield, Coastal Biotic Vegetation, Saltspray Vegetation, and Closed Cushion Carpet. Multidimensional scaling indicated that the vegetation communities were not well delineated but were continua. Discriminant analysis and a classification tree identified altitude, wind, peat depth, bryophyte cover, and extent of bare ground, and particle size as discriminating variables. The combination of small area, glaciation, and harsh climate has resulted in reduced vegetation variety in comparison to those subantarctic islands north of the Antarctic Polar Front Zone. Some of the functional groups and vegetation communities found on warmer subantarctic islands are not present on Heard Island, notably ferns and sedges and fernbrakes and extensive mires, respectively. Postdispersal Seed Predation on Sisyrinchium arenarium (Iridaceae) at Two Elevations in the Central Chilean Andes (pp 178-184) Alejandro A. Muñoz and Mary T. K. Arroyo Postdispersal seed predation in alpine communities has received surprisingly little attention. We evaluate the magnitude of seed predation by ants and avian granivores in the perennial herb Sisyrinchium arenarium through a field experiment at two different elevations (2700 and 2000 m) in the central Chilean Andes. A total of 96 pots, containing 50 seeds each, were placed at each elevation and randomly assigned to one of four treatments: control, bird exclusion, ant exclusion, and total exclusion (wind control). We also compare the activity of ants and avian granivores at the two elevations. Mean percentage seed removal by wind was 23 and 21% at 2700 and 2000 m elevation, respectively. Overall, after subtracting seed loss by wind, seed removal by granivores was low at both sites (2-14%), although it was significantly greater at the higher elevation (2700 m). This was concordant with the greater activity of ants and granivorous birds there. Seed removal by ants was greater than by birds at the higher site (14 vs. 4%, respectively), but did not differ at the lower elevation (3 vs. 2%, respectively). Results contrast with those reported for central Chilean mediterranean-type climate shrublands at lower elevations where avian and rodent granivory is important, while that by ants is low. Future studies considering plant species with different seed characteristics (e.g., size, shape, energetic value) and taxonomic affiliation will be necessary to assess the general importance of this ecological process in the central Chilean Andes and alpine areas in general. Relationships between Flowering Phenology and Fruit-set of Dwarf Shrubs in Alpine Fellfields in Northern Japan: a Comparison with a Subarctic Heathland in Northern Sweden (pp 185-190) Gaku Kudo and Shizuo Suzuki Relationships between flowering phenology and fruit-set of 10 ericaceous species were studied in three alpine fellfields in the Taisetsu Mountains, northern Japan. Flowering season varied from late May to early August among species. There was a positive correlation between flowering time and fruit-set under natural conditions. Pollinator exclusion by net-bagging and hand-pollination revealed that very low fruit-set in early-flowering species was caused by severe pollen limitation, while late-flowering species tended to have high fruit-set with slight pollen limitation. Such seasonal patterns reflect the changes in seasonal activity of pollinating insects, which are highly influenced by ambient temperature. A similar research program was conducted in a subarctic heathland in northern Sweden with almost similar species composition. In Sweden, however, there was no positive correlation between flowering time and fruit-set. The difference between the alpine fellfields and the subarctic heathland may be caused by the specific seasonal pattern of temperature change in either region. A steep increase in air temperature from early to mid-summer in the alpine fellfields in Japan may cause an increase in pollinator availability with progress of season. Effects of Snowfall Fluctuation on Tree Growth and Establishment of Subalpine Abies mariesii near Upper Forest-limit of Mt. Yumori, Northern Japan (pp 191-200) Takuya Kajimoto, Takeshi Seki, Shigeto Ikeda, Hiromu Daimaru, Toru Okamoto, and Hiromichi Onodera We examined effects of annual snowfall fluctuation on tree growth and establishment in a mature stand (ca. 200 yr old) of Japanese subalpine Abies mariesii Mast. near upper forest-limits at leeward site. Relatively tall and aged fir trees (<5 m, <100 yr old) retained various scars of past mechanical damage due to snow pressures, e.g., multiple-, tip dieback- and broken-stems, and canopy anomaly. Ring-width pattern analysis showed that these deformed trees mostly experienced abrupt growth reduction. Some events of such abrupt growth reduction occurred simultaneously just after winters with heavy snowfall (e.g., mid-1960s), indicating that the A. mariesii trees often suffered from snow damage due to settlement force of excess snowpack. Particularly, in snowy winters, mechanical breakage of branches were likely to occur intensively at the height of 1 to 3 m above the maximum snowpack level of normal snowfall winters (ca. 3 m). On the other hand, some aged, but suppressed, trees sharply enhanced their growth rates simultaneously after such period of the intensive snow damage. This indicated that the snow damage upon the relatively tall trees sometimes facilitated regeneration of nearby shaded-trees by creating small-scale gaps. The snow-induced disturbance events may have occurred at about 10-yr intervals during the last half of 20th century. Our findings suggested that population dynamics of A. mariesii near its upper forest-limit, especially located at leeward and snowy site, was closely affected by the repetitive events of snow damage following snowy winters: the event primarily acted as a major limiting factor for canopy development of individuals, and sometimes triggered growth of suppressed-trees. Spatial Structure and Associations in a Pinus canariensis Population at the Treeline, Pico del Teide, Tenerife, Canary Islands (pp 201-210) M. Srutek, J. Dolezal, and T. Hara Variation in spatial pattern and its consequences for intraspecific associations, regeneration, and allometric relationships in a population of Pinus canariensis was studied along an altitudinal gradient at the treeline on the west-northwest slope of Pico del Teide (Mount Teide) in Tenerife, Canary Islands. We sampled 11 plots (20 by 20 m), situated 30 m a.s.l. apart along a 4380 m transect which ran from the treeline at (2020 m a.s.l.) to the forest interior (1720 m a.s.l.). In each plot, we recorded height, diameter at breast height (DBH) and location of all tree stems (>130 cm in height), number of seedlings and saplings, and percent cover of vegetation layers. Stand basal area and maximum tree height decreased with altitude. The spatial distribution of P. canariensis was characterized by increasing regularity with tree size irrespective of altitude. The decrease in intensity of clumping with tree-size and the uniform pattern in older stages indicated intraspecific resource competition. The tree response to increasing altitude was largely associated with restricted height growth. At the treeline, the trees similar in diameter to those of lower-altitude sites were substantially shorter. The seedling and sapling density decreased significantly with increased altitude and increased in stands with increased basal area and canopy cover. Tree density along the altitudinal transect was similar, but trees at high-altitudes were shorter with smaller crowns, thus creating less favorable conditions for seedling and sapling survival. The positive or facilitating relationship between canopy trees and seedlings and saplings suggests that environmental factors (here stressful conditions) perform a key role in seedling establishment. Our results suggest that competitive relationships among canopy trees play a key role in generating stand structure. Dry Heath Arctic Tundra Responses to Long-Term Nutrient and Light Manipulation (pp 211-218) L. Gough, P. A. Wookey, and G. R. Shaver Long-term fertilization studies in several arctic ecosystems have demonstrated dramatic responses of plant community structure with concomitant changes in ecosystem properties. Although these results are well documented in moist tussock and wet sedge tundra, dry heath tundra has been less studied. In an Alaskan dry heath arctic tundra, we conducted a biomass harvest of plants that received additional nitrogen (N, 10 g m-2 yr-1) and/or phosphorus (P, 5 g m-2 yr-1) or reduced light (50% of ambient) for 8 yr. We expected responses to be similar to those of other arctic tundra communities with increased biomass resulting from added nutrients and species responding individualistically to generate the community-level response. However, total vascular biomass did not change in the dry heath tundra in response to any treatment, although individual species and functional group biomass differed from controls. Aboveground productivity, estimated using new apical growth, significantly increased in the N and N+P plots caused by significantly greater abundance of a tussock-forming grass, Hierochloe alpina. The lowest species richness was recorded in the N alone plots, where a deciduous shrub, Betula nana, had its greatest biomass, and richness also declined in N+P plots. Plots that received P alone had similar biomass and species richness to controls, although shrubs decreased in abundance. The shade treatment caused minor biomass differences, marginally less new apical growth, and slightly lower species richness compared to control plots. These results were similar to several ongoing studies in Alaskan moist tussock and wet sedge tundras where aboveground productivity increased in response to added N and/or P but biomass response lagged. This shift in the dry heath tundra from an evergreen shrub to a grass dominated system in the N and N+P plots may cause profound ecosystem function changes as woody biomass capable of long-term carbon storage is lost. Fates of Added Nitrogen in Freshwater Arctic Wetlands Grazed by Snow Geese: The Role of Mosses (pp 219-225) Peter M. Kotanen Previous studies have shown that the growth of fresh-water grasses and sedges eaten by breeding colonies of Snow Geese responds weakly to nitrogen additions, and also is poorly able to compensate within the same season for tissues lost to geese. These results contrast with the rapid responses to grazing and fertilization that have been observed in salt-marsh species. A possible explanation is that the mosses prominent in fresh-water wetlands rapidly sequester added nitrogen, preventing access by forage species to the fecal inputs provided by foraging geese. To investigate this hypothesis, I added ecologically realistic amounts of ammonium and nitrate labelled with 15N to the surface and rooting zone of experimental plots in freshwater wetland vegetation at two Snow Goose colonies. Results indicate that the presence of mosses did not prevent forage species from rapidly taking up ammonium and nitrate added either at or below the moss surface. Nonetheless, most of the added 15N was absorbed by the moss layer; consequently, mosses tend to divert nitrogen away from forage species and into long-lasting peat. In the long term, this may reduce the ability of freshwater forage plants to recover from damage by increasing populations of Snow Geese.