Impact of Climate Change on Soil Hydro-Climatic Conditions and Base Cations Weathering Rates in Forested Watersheds in Eastern Canada

Daniel Houle,Fougère Augustin,Christian Gagnon,Gérald Dermont,Charles Marty

doi:10.3389/ffgc.2020.535397

Abstract

Increases in mean annual air temperature (MAAT) and mean annual precipitation (MAP) are projected for north eastern North America, which will alter soil hydro-climatic conditions and hence the rate of many soil processes. Among them, chemical weathering of soil minerals is an essential source of base cations (BC) which control the acid-base status of surface waters and are crucial for forest nutrition. In this modeling study, MAAT and MAP projections from a regional and a global climate models were first used to project changes in soil temperature (MAST) and soil water content (SWC) with the ForStem and ForHym models for 21 eastern Canadian forested catchments. The models predicted an increase in MAST by 2.03-2.05°C and 2.87-3.42°C for the 2041-2070 and 2071-2100 periods, respectively, and small decreases (<5%) in SWC. In a second step, these projected changes in MAST and SWC were used to estimate changes in BC weathering rates (WR) and soil pH with the geochemical model PROFILE. The simulations indicated that BC WR would increase by 13-15% and 20-22% for the 2041-2070 and 2071-2100 periods, respectively. The increase in BC WR was accompanied by an increase not only in base cation concentrations, but also in soil pH at most sites, suggesting that future temperature increase has the potential to ameliorate the acid-base status and the fertility of soils in eastern Canada through its impact on WR.

Highlights

Recent climatic simulations have shown that mean annual air temperature (MAAT) may rise by up to 4–7◦C by the end of the century relative to the 1971–2000 period under a scenario of high greenhouse gas (GHG) emissions (RCP 8.5) in southern Québec, Canada (Ouranos, 2015)
We estimated the potential changes in chemical weathering rates (WR) and base cations (BC) availability that would result from changes in soil hydroclimatic conditions only
This study shows that the projected climate warming in the region would result in a mean annual soil temperature (MAST) increase of 2.03–2.05◦C and 2.87–3.42◦C during the same periods

Summary

Introduction

Recent climatic simulations have shown that mean annual air temperature (MAAT) may rise by up to 4–7◦C by the end of the century relative to the 1971–2000 period under a scenario of high greenhouse gas (GHG) emissions (RCP 8.5) in southern Québec, Canada (Ouranos, 2015). Results reported by Li et al (2016) showed a strong positive correlation between mean annual temperature and the rate of CO2 consumption associated with the weathering of basaltic rocks These studies suggest an increase in chemical weathering rates in response to climate warming, potential reduction of soil moisture resulting from increased evapotranspiration (Milly, 1992) associated with higher temperature may counteract the increase in soil processes due to warmer temperatures. Such a mechanism has been reported for microbial SOM mineralization and nitrification rates (Venterea et al, 2003; Groffman et al, 2009; Durán et al, 2014)

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Conclusion