Abisko, Sweden

Dataset code ABK

Research area
Longitude
23.52° to 17.67°
Latitude
67.07° to 67.07°
Publication
  • 2002, Bigler, C. and Hall, R.
Main publication summary

Bigler, C. and Hall, R. 2002. Diatoms as indicators of climatic and limnological change in Swedish Lapland: a 100-lake calibration set and its validation for paleoecological reconstructions. Kluwer Academic. Journal of Paleolimnology 27: 97-115.

This study investigated the distribution of subfossil diatom assemblages in surficial sediments of 100 lakes along steep ecological and climatic gradients in northernmost Sweden (Abisko region, 67.07° N to 68.48° N latitude, 17.67° E to 23.52° E longitude) to develop and cross-validate transfer functions for paleoenvironmental reconstruction. Of 19 environmental variables determined for each site, 15 were included in the statistical analysis. Lakewater pH (8.0%), sedimentary loss-on-ignition (LOI, 5.9%) and estimated mean July air temperature (July T, 4.8%) explained the greatest amounts of variation in the distribution of diatom taxa among the 100 lakes. Temperature and pH optima and tolerances were calculated for abundant taxa. Transfer functions, based on WA-PLS (weighted averaging partial least squares), were developed for pH (r2 = 0.77, root-mean-square-error of prediction (RMSEP) = 0.19 pH units, maximum bias = 0.31, as assessed by leave-one-out cross-validation) based on 99 lakes and for July T (r2 = 0.75, RMSEP = 0.96°C, max. bias = 1.37 °C) based on the full 100 lake set. We subsequently assessed the ability of the diatom transfer functions to estimate lake-water pH and July T using a form of independent crossvalidation. To do this, the 100-lake set was divided in two subsets. An 85-lake training-set (based on single limnological measurements) was used to develop transfer functions with similar performance as those based on the full 100 lakes, and a 15-lake test-set (with 2 years of monthly limnological measurements throughout the icefree seasons) was used to test the transfer functions developed from the 85-lake training-set. Results from the intra-set cross-validation exercise demonstrated that lake-specific prediction errors (RMSEP) for the 15-lake test-set corresponded closely with the median measured values (pH) and the estimations based on spatial interpolations of data from weather stations (July T). The prediction errors associated with diatom inferences were usually within the range of seasonal and interannual variability. Overall, our results confirm that diatoms can provide reliable and robust estimates of lake-water pH and July T, that WA-PLS is a robust calibration method and that long-term environmental data are needed for further improvement of paleolimnological transfer functions.
Parameter (unit) Result_AVG Result_MAX Result_MIN N (samples)
Ca meq/L 0.1 1.03 0.01 100
Cl meq/L 0.03 0.1 0.01 100
COND uS/cm 2.08 12.8 0.56 100
DOC mg/L 3.5 13.4 0.2 100
K meq/L 0.01 0.05 0 100
Mg meq/L 0.04 0.18 0.01 100
Na meq/L 0.04 0.11 0.01 100
pH 6.66 8.07 5.79 100
Si mg/L 0.79 3.06 0.01 100
SO4 meq/L 0.04 0.36 0.01 100
TEMP °C 10.39 17.5 2.4 100
TOC mg/L 4.08 14.9 0.7 100

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