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.