Figure 1. Lake specific trends in total atmospheric S deposition, runoff, surface air temperature, NDVI and lake DOC concentration.

Estimated Theil-Sen’s slope values (y⁻¹) based on site-specific Regional Kendall Tests for (a) catchment total atmospheric S deposition, (b) runoff, (c) surface air temperature, (d) NDVI and (e) lake DOC concentration during the study period (1986–2011). Positive temporal trends are depicted using shades of red, whereas negative temporal trends are depicted using shades of blue. A stronger shade in either trend direction denotes a faster trend when compared regionally. The categorization levels were determined using R’s pretty function on absolute slope values⁷³. All S deposition trends where negative, and all temperature trends where positive, 85% of the DOC trends and 76% of the NDVI trends were positive, and 65% of the catchments displayed negative runoff trends. Overall, the mean regional trends for the whole study area for all five variables were significant (positive for NDVI, temperature and DOC, negative for S deposition and runoff, Regional Kendall Tests with lakeID as block, n = 70, all with p < 0.017). Figure created in R v. 3.2.1 (URL http://www.R-project.org/)⁶¹ using the libraries raster⁶⁰ and sp⁷⁴.