Fig 1.
Turkey Lakes Watershed (upper panel) and location of the study lake and nearby Upper Mallot Lake in the context of regional forest zones (lower panel). Data sources: Vegetation data extracted from ref no. [38] and base map layers extracted from the CanVec+ digital cartographic reference product produced by Natural Resources Canada in 2015. Both data sources are licensed under the Open Government License—Canada (http://www.nrcan.gc.ca/earth-sciences/geography/topographic-information/free-data-geogratis/licence/17285). Figures generated using ArcGIS.
Table 1.
Physical characteristics, median pH, alkalinity and nutrient concentrations for Wishart Lake for 1980–1985.
Data from ref no. [35].
Table 2.
Po-210 activities used to model ages in Wishart Lake core WS04/WS03.
Po-210 is assumed to be in secular equilibrium with Pb-210.
Table 3.
Wishart Lake Sediment Core (WS03) AMS radiocarbon dates.
Dates were calibrated using the INTCAL09 calibration curve and the program Calib v6 [47].
Fig 2.
Age-depth model for the Wishart Lake sediment record.
The model was developed using a linear regression model fit to calibrated radiocarbon dates, recent chronological data points derived from the Ambrosia pollen rise (depth 40 cm) and activity of 210Pb (lower boundary used, depth 50 cm). Radiocarbon dates (the five lowermost points) are shown with histograms corresponding to the probability distribution of calibrated dates [53]. Figure generated using clam for R [53].
Fig 3.
Holocene diatom stratigraphy for Wishart Lake.
Diatom species are displayed in percent abundance. Only taxa appearing at >2.5% abundance in any one sample are plotted out of a total of 280 taxa recorded. Sample points where rare taxa appear at <0.5% abundance are displayed by the + symbol. Three significant zones were delineated using cluster analysis (solid red lines, with the dashed grey line separating Zone 1 into two sub-zones). The solid green line in the upper zone indicates the Ambrosia rise. The age axis is in calibrated, calendar years BP where year -61 is the time of core collection (2011 AD). Full diatom counts are available at neotomadb.org (Dataset ID = 19788; http://apps.neotomadb.org/Explorer/?datasetid=19788). Diagram plotted using C2 [64].
Fig 4.
Ordination results for Wishart Lake diatoms and Upper Mallot Lake pollen assemblages.
Detrended Correspondence Analysis axis 1 (solid lines) and axis 2 (dashed lines) for Wishart Lake diatom record (lower panel) and for the past ~7200 cal. yr BP Upper Mallot Lake pollen record (upper panel; raw pollen data from ref. [20] and publicly archived at neotomadb.org). Red lines delineate Wishart Lake diatom zones from cluster analysis; dashed grey line indicates the subdivision of Zone 1. Analysis and diagram generated using the rioja package for R [62].
Fig 5.
Post-settlement changes in Wishart Lake sediments.
Changes in % abundance of Cyclotella sensu lato diatoms (orange curve), % Ambrosia pollen (black curve) and sediment bulk density (blue curve), are shown as a function of age in cal yr BP, with 0 yr BP = 1950 AD. Figure plotted using standard R plotting functions.