Soil water recharge for grassed and forested land covers on the Oak Ridges Moraine, southern Ontario, Canada

Abstract

Soil water recharge (R) below 1 m depth was estimated via a 1-d water balance for grasslands, hardwood stands and red pine plantations on the Oak Ridges Moraine (ORM) in southern Ontario, Canada. Annual R values (431–696 mm) were in the order of previous estimates for outcropping sands and gravels on the ORM (∼400 mm); however, they only partially supported hypothesized differences in R between land covers. Annual R was similar for grasslands and hardwood stands and exceeded that for red pine plantations. However, there were no consistent differences in R between land covers for growing or dormant seasons, due to relatively large uncertainties for R estimates as well as inter-site differences in the soil's ability to store and transmit inputs below 1 m. Nevertheless, shifts in annual R appear to have accompanied historical land cover changes from hardwood-conifer stands → agricultural fields → red pine plantations → regenerating hardwoods. Growing season R in hardwoods makes a larger contribution to total R than for other land covers, partly due to spatially focused throughfall and stemflow contributions to R. Results highlight the role of land cover differences when assessing spatial variations in R along the ORM.