Multiproxy lake sediment records at the northern and southern boundaries of the Aspen Parkland region of Manitoba, Canada

Abstract

Aspen parkland in central Canada may change substantially with increased warming and aridity as prairies replace forests, fire return intervals decrease, and lake levels decline. We examined the relationships among vegetation, climate, fire, and lake-ecosystem properties using lake sediment cores from the current northern and southern boundaries of the aspen parkland in southwestern Manitoba. We analyzed pollen, charcoal, sediment magnetics, biogenic silica, phosphorus, grain size, and LOI, and dated the cores using 210Pb and 14C (AMS, calibrated). The Jones Lake record, from the southern edge of the parkland, began considerably earlier (~11,000 cal BP) than the Mallard Pond record at the northern edge (~8,600 cal BP). These sites were characterized as prairie communities with low fire severity and relatively low lake productivity during the warm, dry period from 9,000-6,000 cal BP. Beginning around 6,500 cal BP at Jones Lake and 3,400 cal BP at Mallard Pond, conditions appeared to get wetter as indicated by arboreal pollen percentage increases from ~30% to 40-60% concurrent with a rise in charcoal and proxies for lake productivity (biogenic silica and percent organic phosphorus). Similar to previous studies along the prairie-forest border, we found that charcoal increased during warmer, wetter periods with increased forest cover and fuel loading rather than during warmer, drier periods of prairie dominance. Our results underscore the importance of regional changes in moisture, and its effects on lake levels and forest biomass, as a dominant control of the aspen parkland dynamics.

Diatom-based evidence of regional aridity during the mid-Holocene period in boreal lakes from northwest Ontario (Canada)

“…Spatial and temporal variability in sediment records can be attributable to many factors, including spatial variability in climate and individual responsiveness of the lakes. Potentially, the more western and closer location of Meekin Lake to the PFE explains the earlier onset of higher lake levels, whereas there may have been a lag in the response in the more northern site, as seen in Teed et al (2009). However, the timing of the transition to higher lake levels is similar between Lake 239 and Gall Lake, thus physical characteristics of the lakes, and local geological and vegetational settings, may have played more of a role in lake response than geographical position.…”

“…(a) Map showing the location of the three study lakes (Meekin, ELA Lake 239, and Gall Lake) that are located within the Winnipeg River Drainage Basin. Black dash line is the modern-day prairie-forest boundary (Teed et al, 2009). Meekin Lake is located in the Lake of the Woods/Rainy River Watershed, whereas Lake 239 and Gall Lake are located in the English River Watershed.…”

Changes in the prairie–forest ecotone in northwest Ontario (Canada) across the Holocene

“…1), however, suggest ecological and/or climate changes occurred despite the sustained high abundances of these taxa. The prolonged occurrence of middle Holocene conditions at Meekin Lake could be related to changes in fire dynamics, as previous studies have described the importance of fire in the maintenance of the eastward position of the PFE (Camill et al, 2003; Umbanhowar et al, 2006; Teed et al, 2009; Williams et al, 2009). The effect of large grazing mammals on the PFE might also be a potential mechanism in maintaining the eastward-shifted PFE.…”

Early holocene monsoonal fluctuations in the Garhwal higher Himalaya as inferred from multi-proxy data from the Malari paleolake

“…The phosphorus fractions (inorganic and organic), as proxies for paleoclimate in lake sediments of glacial-periglacial regions, have been extensively exploited, for example in Canada (Slaymaker et al, 2003;Filippelli et al, 2006;Teed et al, 2009), in southern California and Illinois, USA (Filippelli and Souch, 1999;Kirby et al, 2007), and in Costa Rica. No such attempts have been made to understand the dynamics of different species of phosphorus in the Indian subcontinent.…”