LAKE RECORDS OF SOIL DEVELOPMENT AND ECOSYSTEM STATUS IN ALPINE SETTINGS
Joffre Lake lies just west of the Coast Mountains divide, and Kokwaskey Lake lies east of the divide, positioned about 70 km east from Joffre Lake. Both records extend back to regional deglaciation, at ~11 Ka, and exhibit similar P records, revealing the regional history of soil and ecosystem development. Lake sediments show a dominance of mineralized P forms in the early (11-10 Ka) portion of the record, reflecting a regional landscape dominated by bedrock and unweathered glacial deposits just after glacial retreat. From 10-8.5 Ka, an increase in organic and occluded P forms in the lake sediments indicates increased soil formation and maturity. The interval from about 8.5-1 Ka is marked by relatively constant conditions. Although organic and occluded P together reached about 30%, mineralized P forms still dominated the total P content, reflecting both relatively immature regional soils (attributable to steep unstable slopes) and the continued presence of upstream alpine glacial sources of rock flour input. Both records reveal a shift coinciding with the onset of Little Ice Age conditions over the last ~1 ky, with mineralized P forms once again overwhelmingly dominating the sediment record. This shift is rapid, and indicates that the landscapes returned to a state of soil development similar to that of the earliest Holocene.