Carbon burial and infill rates in small Western Boreal lakes: physical factors affecting carbon storage

Abstract

Effects of depression depth (ZT), lake surface elevation (ES), catchment area:lake surface area (AT:AO), trophic status, and surficial geology on sediment burial rates in small Western Boreal Plain lakes were assessed using content and chronology of cores from a relatively large and small lake on each of moraine (M), glaciofluvial (GF), and glaciolacustrine (GL) deposits. Aquatic and terrestrial plant and sediment carbon:nitrogen (C:N) suggested most buried C was aquatic. The rate of long-term total C burial averaged 31 g·m–2·year–1 (range: 0–84 g·m–2·year–1); this was recently 79 g·m–2·year–1 (range: 40–180 g·m–2·year–1) (higher and more variable rates than previously reported for Boreal lakes). Long-term C accrual rate and sediment depth increased with increasing ZT. In each landform, a relatively low base elevation (EB = ES – ZT) lake began accumulating sediment thousands of years before a high EB lake. GF depressions were deeper and had accrued more C·m–2 (and infilled) faster than M and GL lakes; a large GF lake had no organic sediment, perhaps because of large groundwater inputs. Increasing AT:AO corresponded with increasing C accrual rates where precipitation and evaporation dominated (surface runoff infrequent) (M and GL) but not where groundwater dominated (GF lakes) lake water budgets, illustrating the importance of landform and depression characteristics in regionalizing lake-C burial estimates.