Population structure of lakeshore willows and ice‐push events in subarctic Québec, Canada

Abstract

The effects of ice‐push on shoreline population age structure of Salix planifolia was investigated at Clearwater Lake, a large lake (1270 km2) located in the eastern Canadian subarctic. Twenty‐three willow stands located along a gradient of exposure to ice features were studied along the shoreline of a large island. Stand characteristics are significantly correlated with the degree of shore exposure. Drift‐ice action maintains continuously vegetation free substrata furthering willow colonization in shoreline habitat. Well‐rooted shrubs withstand disturbance through vegetative regenetation, that is profuse basal sprouting in response to ice‐scouring and breakage of stems. Age structure of basal shoots is highly correlated with ice‐scar dates. The rapid turnover of stem metapopulations frequently damaged by ice allows the shrubs to live older than usually. During recent decades, drift‐ice activity contributed to maintain a fast changing shore zone, favourable for the development of shrub populations. High frequency and magnitude of ice‐push events were caused by periodic high spring water levels.

The impact of sea erosion on coastal Pinus pinea stands: A diachronic analysis combining tree-rings and ecological markers

“…precipitation in arid regions, and temperatures at highlatitude and -elevation sites (Hughes, 2002). However, they have been used only occasionally to reconstruct sea-level rise (Robichaud and Bé gin, 1997) or similar events such as shore erosion (Bé gin and Payette, 1991;, lake level fluctuations (Bé gin, 2000a), and lakeshore erosion (Bé gin, 2000b), stream erosion (Warren, 1961) and, recently, salinity of water table (Stahle et al, 2001). Such studies were based on the evidence that plant recruitment and tree growth are limited by sea vicinity, and treerings were used retrospectively for reconstructing past local coastal erosion rates (Wiles et al, 1998).…”

Ecology of freshwater shore zones

“…Floatable materials can be washed into the shore zone more or less permanently, or they can be very transient, washing up in one storm and leaving a few days later in the next. The expansion and contraction of the sheet of ice covering a lake or river can bulldoze shoreline materials into a ridge along the shore and destroy vegetation (Begin and Payette 1991). Alternatively, when the ice sheet breaks up, winds, currents, and flood waters can push large mounds of ice onto the shoreline, moving materials and destroying plants and animals.…”

“…Disturbances other than wind and wave action also are important. Ice and low temperatures can be important agents of disturbance along cold shorelines (Dall et al 1984;Begin and Payette 1991;Pugh and Davenport 1997). The importance of flooding and desiccation has already been discussed.…”

Effects of River Regulation on River-Margin Vegetation: A Comparison of Eight Boreal Rivers

“…Organisms with short generation times are often RIVER REGULATION AND MARGIN VEGETATION favored in human-made ecosystems, but such species also benefit from natural formation of disturbance patches (Grime 1979, Pickett and White 1985, Huston 1994. In areas with recurrent ice formation, ice scouring may damage or remove plants and create patches of bare soil on lakeshores and river margins, predominantly during the spring flood (Bégin andPayette 1991, Bélanger andBédard 1994). Ice scouring of riparian zones occurs regularly in the Torne and Kalix rivers during the spring flood (Raab andZachrisson 1984, Nilsson et al 1989), but is infrequent in the Vindel River.…”