ISSN:
1573-0417
Keywords:
stable isotopes
;
paleohydrology
;
carbon cycling
;
cellulose
;
treeline
;
Northwest Territories
;
Canada
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Geosciences
Notes:
Abstract Analysis of δ18Ocellulose, δ13Corganic matter, and δ13Ccellulose at about 100 year intervals from organic matter deposited in Toronto Lake, Northwest Territories, Canada, revealed an 8000-year history of rapid, post-glacial hydrologic change at the treeline zone. Several mid-Holocene phases of enriched δ13Corg and δ13Ccell, caused by elevated lake productivity, declining [CO2(aq)], and closed basin conditions, were abruptly terminated by intervals of open hydrology recorded by sharply depleted δ18Ocell. Two of these events, at 5000 and 4500 BP, are correlated with increased total organic content and Picea mariana pollen concentration, which indicate that high levels of productivity were also accompanied by northern treeline advances. A third treeline advance at about 2500 BP is also marked by an apparent outflow event from Toronto Lake, but this was not associated with δ13Corg/cell enrichment in the sediment record because rapid and substantial lake water renewal probably prevented productivity-driven enrichment of the dissolved inorganic carbon and replenished the CO2(aq) supply to thriving phytoplankton. However, high sediment organic content during this period suggests increased productivity. Increases in the inflow:evaporation ratio at about 6500 and 3500 BP were also sufficient to cause Toronto Lake to overflow but the prevailing climate during these periods apparently did not favour appreciable northward treeline migration or changes in lake productivity.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00196779
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