Wayne L Strong

Pre- and postsettlement palynology of southern Alberta

Abstract A comparison of pre- and postsettlement pollen spectra from southern Alberta reveals changes in vegetation formations and vegetation composition within the region. Settlement appears to have resulted in the expansion of the Short Grass Prairie possibly due to increased grazing pressure in the Mixed Grass Prairie, whereas the Aspen Parkland has advanced southward. The response of individual types of plants to settlement was varied, but marked increases were observed in introduced plants such as Chenopodiaceae/Amaranthaceae and Taraxacum .

Climate and vegetation change during the twentieth century in the lower Peace River district, northern Alberta, Canada.

A 96-yr climate record (1908—2004), historical descriptions, multiyear (1950, 1964, 1978, 1994) lake-surface area measurements, and 1950 and 2004 physiognomically based vegetation maps were compiled to assess vegetation change in the Fox Lake area (4248 ha) within the lower Peace River district of northern Alberta. A climatic warming trend (r = 0.615, P < 0.001; 0.35°C/decade) was evident during the twentieth century, with peak precipitation occurring from 1970 to 1990. Five major wet—dry cycles, based on net water balance values (precipitation minus potential evaporation), were evident with peaks occurring at about 17(±3) year intervals. Each cycle became slightly less arid than the previous until the mid-1990s. Deciduous forests dominated upland sites in 2004, whereas deciduous shrub and juvenile tree stands comprised 78% in 1950. Total wetland area remained relatively constant between 1950 and 2004, but less meadow and more standing water were present in 2004. Lake-surface area changes suggested that wetlands were recharged by precipitation rather than floodwaters from the nearby Peace River. Low water availability and historical descriptions suggest grassland-dominated parkland-like vegetation occurred in the study area during the early part of the twentieth century, with upland shrubs replacing grasslands by 1950. Increased atmospheric water availability rather than cessation of aboriginal burning or natural fires was considered responsible for increased forest abundance after 1945. Greater aridity in response to future global warming could reduce the abundance of forests in the lower Peace River district, and shift the regional climate from a boreal to a grassland-dominated parkland climatic regime.

Wood bison population recovery and forage availability in northwestern Canada

Forage availability was assessed to determine sustainable stocking rates for eight broadly defined vegetation types (Treed Uplands, Treed Lowlands, Mixed Tall Shrub/Sedge, Closed-canopied Willow, and Open-canopied Willow, Meadow, Wetland Grass, Wetland Sedge) for use by wood bison (Bison bison athabascae), a threatened subspecies, in the Canadian boreal forest of northern Alberta. Clip plots (n=108) were used to sample peak availability of herbs and current annual growth of Salix spp. in late summer. Graminoid wetlands dominated by Carex atherodes, Carex aquatilis, Carex utriculata, Scolochloa festucacea, or Calamagrostis stricta produced 1975-4575 kg ha(-1) of fair to good quality forage, whereas treed stands produced < 250 kg ha(-1) of forb-dominated forage (>85% content), which was below a published 25% foraging efficiency threshold of 263 kg ha(-1) for bison. Upland forests that dominate the region produced < or = 1 animal unit day (AUD) of forage per hectare in summer. Most forest understory plants were of poor forage value, suggesting the potential sustainable stocking rate of such areas was actually < or = 0.3 AUD ha(-1), with even lower rates during winter due to snow cover. Herbaceous wetlands contained approximately 78 AUD ha(-1) of forage, but were considered largely unavailable in summer because of flooding and soft organic soils that make access difficult. Conversion of prime foraging habitat to agricultural land, forest expansion due to fire control, and a warmer and wetter climatic regime after the mid-1900s likely contributed to a regional reduction in carrying capacity. It is hypothesized that substantial recovery of the wood bison population toward historical levels will be constrained in northern Alberta by the availability of summer forage, and the limited extent of graminoid wetlands that provide winter foraging habitat.