The vertical distributions of Parmelia olivacea and a few other epiphytic lichens on trunks of deciduous trees were studied in relation to maximum snow depth along an oceanic-continental climate gr...

Patterned wetlands occur extensively throughout the Canadian subarctic and boreal regions. These areas are important because of their hydrological and chemical interaction with other ecosystems, aquatic and terrestrial. However, there is a lack of knowledge on the hydrology of many wetland types in the boreal and subarctic regions, particularly patterned fens. This paper examines the relationship between the flux and storage of water both within a patterned wetland and between it and the adjacent ecosystems. It is hypothesized that patterned wetlands alternate between two hydrological phases. The first occurs when the water supply exceeds the depression storage capacity of the patterned wetland pools, and the wetland drains as a single source area, while receiving inputs from adjacent nonwetland portions of the basin. As a result, basin discharge during such periods is relatively high. The second phase occurs when the loss of water through seepage and evaporation leads to disconnection of the wetland pools into separate microcatchments within the pool-ridge complex. Under this condition, basin discharge is relatively low, maintained only by a limited source area immediately upstream of the outlet. Through an explanation of the hydrological processes and linkages among subsystems, an understanding of the processes governing runoff from a basin with a patterned wetland at its outlet is obtained. It is demonstrated that the discharge response of patterned wetlands is distinctive from that of other wetland types because the large storage capacity of the wetland pools delays runoff contributions from large portions of the wetland and surrounding basin.

Lichenometric ages of active glacigenic rock glaciers and Matthes (Little Ice Age) moraines, together with sediment cores from basins below these landforms, provide evidence for a glacier advance -3000 yr ago in the Sierra Nevada, California. Diameters of the largest lichens (70-108 mm) on the Mendel rock glacier indicate that it began forming well before the onset of the Little Ice Age (LIA) (-700 yr BP). Smaller lichens (30-45 mm) on the Matthes moraines of Darwin and Conness glaciers suggest that they formed during the LIA. The apparent lack of pre-LIA Holocene moraines below clean glaciers in the Sierra Nevada demonstrates that the pre-LIA Neoglacial advance must have been less extensive than the Matthes advance. Sediment cores recovered below Matthes glacial deposits provide additional support for a pre-LIA Neoglacial advance. Three cores from a meadow directly below the Powell rock glacier record grus deposition (suggesting nonglacial, summer-dominant mass wasting) between about 5300 and 3600 14C yr BP (--6000-3900 cal yr BP), and alternating gyttja and silt (suggesting cooler, winter-dominated precipitation) after about 3600 14C yr BP (3900 cal yr BP). A lake core from below Conness Glacier shows a transition from higher-organic sediments (10-16% total organic carbon) to lower-organic sediments (2-4% total organic carbon) at approximately 3200 14C yr BP (3400 cal yr BP), suggesting formation and growth of the glacier in the cirque at that time.

The Rivière George Caribou Herd (RGCH), in northern Québec, erupted during a few decades to culminate at approximately 800,000 animals by 1990. The RGCH appeared regulated by competition for summer forage. Repeated browsing and trampling reduced summer range productivity to 50% compared to ungrazed areas, lichens and dwarf birch having been mostly responsible for this reduction. A reconnaissance flight in 1991 and intensive field work the following two summers suggested that caribou use of dwarf birch leaves was light following the period of peak numbers. We hypothesized that birch stands would show signs of rapid and vigorous recovery in 1993-1994. We surveyed five heavily browsed birch stands, and two inaccessible, lightly browsed ones. Although utilization of birch leaves by caribou ranged between 0 and 6% during the 1994 growing season, heavily browsed stands exhibited no signs of rapid and strong recovery. Young plants did not abound in heavily browsed stands compared to lightly browsed ones, neither was wood accumulation faster in the former than in the latter. Stem density and height were similar in heavily browsed and lightly browsed stands. However, the leaf/wood ratio and the percent dry weight of leaves and wood were higher in lightly browsed than in heavily browsed stands, which resulted in approximately twice as high leaf biomass in lightly browsed than in heavily browsed stands. We hypothesized that previous intense caribou browsing caused a persistent suppression of dwarf birches, and that stems could not accumulate sufficient reserves during a growing season to deploy more leaves in the next spring in order to return the leaf/wood ratio to a normal value. We discuss the consequences of such a reaction of dwarf birch to herbivory on the demography of the RGCH.

Largest lichens (genus Rhizocarpon) were measured on 2800 boulders sampled systematically at 28 sites on a thin triangular talus. Sites with similar lichen-size frequency distributions were grouped and used to interpret the temporal and spatial patterns of rockfall supply. Most of the slope yields size-distributions of largest lichens that reflect the history of rockfall activity over at least the last 400 yr. A general increase in surface age diagonally downslope suggests boulders are supplied by rockfall rather than avalanching, with no evidence of postdepositional redistribution. At one corner of the talus foot the lichen-size distributions have reached equilibrium, suggesting negligible supply of boulders during the late Holocene. Sites at the apex of the talus are dominated by small lichens. Simulation modeling is used to reconstruct possible temporal patterns of debris supply to different parts of the talus, and competing models are tested by estimating the thickness of talus predicted to have accumulated during the Holocene. The normal rate of rockfall during the late Holocene is estimated to result in burial of about 4% of the talus surface each 25 yr. Rates of rockfall supply during the 18th century, the coldest phase of the Little Ice Age, are estimated to have been almost five times the normal late Holocene rate. Results are consistent with talus formation under periglacial conditions during the Holocene; a paraglacial origin is unnecessary.

We compared tree-ring structure and formation for Pinus uncinata Ram. and Pinus sylvestris L. in the Central Spanish Pyrenees. Ring width and the number of tracheids in the latewood and in the entire ring were measured monthly during the growing period in 1993. Both species developed the major part of the tree ring between 10 June and 18 July, although the tree ring formed earlier in P. sylvestris. Tree-ring growth was delayed in the highest elevation stand. Ring width and the number of tracheids in the tree ring were functionally correlated. Pinus uncinata had smaller tree rings with fewer cells in radial transects. Latewood development, including formation, later coloration, and cell wall apposition, started in July and ended in October. Tree rings show greater latewood density and color contrast in P. uncinata. Characteristic tree rings show latewood tracheids with thin cell walls and wide cell lumina in many P. sylvestris cores. The analysis of the intra-annual ring growth and structure variability has thrown light on some interannual assumptions such as phenological variability controlled by climate. In conjunction with past dendroclimatological studies, this work shows the existence of a delay between ring growth and structure and their controlling climatic factors.

Living and dead foraminifera have been investigated along three transects away from tidewater glaciers of northern Novaya Zemlya. There are three glacier-proximal dominant foraminiferal taxa: Allog...

The effect of established shrub willows (Salix commutata and S. phylicifolia) was tested in a primary successional ecosystem at Lyman Glacier forefront in the North Cascade Range (Washington, U.S.A.). To examine the hypothesis that early successional plant individuals form centers of establishment for subsequent vascular plant colonizers, two experiments were conducted to assay the effect of shrub willows on the establishment and survival of indigenous plants. First, the occurrence of indigenous plant species under willow canopies was compared with their occurrence beyond the canopies (experiment 1). Second, the separate effects of willow canopies and associated soils on germinant emergence and survival of an indigenous taxon, Pinus contorta, were evaluated (experiment 2). Both experiments indicated that the shrub willows do not serve as nuclei that facilitate the establishment of new, emerging plant individuals. In experiment 1, the willow canopy had no effect on the observed frequency of most indigenous taxa. Five species, however, were negatively associated with the willow canopies. In experiment 2, willow canopies inhibited the germinant emergence of P. contorta. The greatest emergence occurred in soils transferred from beneath willow canopies to areas beyond the canopies. Results from the two experiments suggest that while the willow canopy is either neutral or inhibitory in its effect on establishment of indigenous plants, the soil developing beneath the willow can actually be a positive factor towards plant establishment.

We estimate the means and the interannual variability during the last 30 yr of the mass balances of the small glaciers of the world (all glaciers except for the two large ice sheets), as well as the influence of these mass balance changes on fluctuations of sea level and their relation to climate. The mass balance data base was enriched by data for glaciers of the Arctic islands, Antarctica, and mountainous areas of Siberia, Central Asia, and the Caucasus, which have not been included in previous compilations. We also use a new estimate of the total area for the small glaciers on Earth: 680 × 103 km2. The global mean mass balance as a function of time was calculated three ways: the arithmetic mean for all glaciers (Gb1), arithmetic mean for a group of representative glaciers with long-term mass balance records (Gb2), and an area-weighted mean (Gb3). The last was calculated for seven large regions in order to estimate the contribution of small glaciers to sea-level change more precisely. The results include the following: • Gb1 and Gb2 show good correlations with each other and with global air temperature anomalies, with correlation coefficients around 0.90. • Gb3 produces a new global mass balance value, averaging −130 ± 33 mm yr−1, totaling −3.9 m in water equivalent for 1961–1990 period, or 0.25 ± 0.10 mm yr−1 in sea-level equivalent. This is about 14 to 18% of the average rate of sea-level rise in the last 100 yr. In the years with unusually negative mass balances, ice wastage contributed about 0.9 mm yr−1 to global sea-level rise, about 50% of the average rise over the recent past. • The contribution of glaciers to sea-level rise has increased greatly since the middle 1980s and even more steeply since the late 1980s, which is in agreement with the rise of global temperature.

Roots of 40 taxa of vascular plants from subantarctic Macquarie Island were examined to determine their mycorrhizal status. Samples comprised 36 flowering plant taxa (Spermatophyta) from 16 families, and 4 nonflowering plant taxa (Pteridophyta) from 4 families. No arbutoid, ericoid, or ectomycorrhizae were observed, nor did we collect the fruiting bodies of any fungi whose presence would indicate or suggest the presence of ectomycorrhizal associations. Fifteen of the plants examined showed vesicles, but vesicles and arbuscles were observed in only three plants: Hydrocotyle novae-zeelandiae (Apiaceae), Pleurophyllum hookeri (Asteraceae), and Acaena magellanica (Rosaceae). Dark septate fungi were observed in the roots of 21 plant species. The one species of orchid found on the island, Corybas dienemus, showed typical orchid mycorrhizae.