Partitioning the impact of environmental factors on lake concentrations and catchment budgets for base cations in forested ecosystems

•We examine base cation budgets (BCQ) and concentrations (BCC) in forested catchments.•Climate is the most important driver of BCQ and BCC in the study area.•We develop multivariate models that explain up to 69% of variation in BCC and BCQ.

Seventy-two forested lake catchments were studied in Quebec (Canada) to examine the influence of climate, atmospheric deposition and catchment characteristics on base cation (BC) concentrations in lake waters (BCC) and base cation budgets at the catchment scale (BCQ). The catchments are located along a bioclimatic gradient in a vast (180 000 km2) study area underlained by the Canadian Shield. Multivariate statistical approaches are used to simultaneously assess the effects of multiple environmental factors on cation fluxes. Mean annual BCC were 132, 40, 24 and 7 μmolc l−1 for Ca, Mg, Na and K, respectively. Mean annual BCQ estimates showed exports of 0.826, 0.251, 0.135 and 0.043 kmolc ha−1 an−1 for Ca, Mg, Na and K, respectively. There were strong similarities in the spatial variation of BCC and BCQ, and also in their links with environmental factors. We hypothesized that the spatial variability of both, BCC and BCQ, were strongly influenced by the spatial variability in the rates of mineral weathering reactions. Variance partitioning indicated that climate-related effects accounted for 51.6% and 52.7% of the variation in BCQ and BCC, respectively. Nonetheless, lake/catchment morphometry and variables linked to solutes sources (lithology, atmospheric deposition and soil properties) were also included in some models. Overall, BCC and BCQ were positively affected by temperature, precipitation as rain and sulphate depositions, and negatively influenced by precipitation as snow and the number of frost days. Multivariate models explaining up to 69% of variation in BCC and BCQ were developed. This study shows the strong impact of climatic drivers on base cation budgets and, thus, on mineral weathering at the regional scale on the Canadian Shield.