Framework for studying the hydrological impact of climate change in an alley cropping system

- We simulated the long-term hydrology of a tree-based alley cropping system.
- Framework combines field data, local climate projections and a HYDRUS model.
- Hydrological forecast for 2041-2070 suggests an overall drier soil.
- Notwithstanding, critically wet periods of one day may occur more frequently.
- Simulated future conditions non-critical for vegetation during snow-free season.

SummaryAlley cropping is an agroforestry practice whereby crops are grown between hedgerows of trees planted at wide spacings. The local climate and the physiological adaptation mechanisms of the trees are key factors in the growth and survival of the trees and intercrops, because they directly affect the soil moisture distribution. In order to evaluate the long-term hydrological impact of climate change in an alley cropping system in eastern Canada, we developed a framework that combines local soil moisture data with local projections of climate change and a model of soil water movement, root uptake and evapotranspiration. Forty-five frequency domain reflectometers (FDR) along a transect perpendicular to the tree rows generated a two-year dataset that we used for the parameterization and evaluation of the model. An impact study with simulations based on local projections of three global and one regional climate simulation suggest that the soil becomes drier overall in the period between 2041 and 2070, while the number of critically wet periods with a length of one day increases slightly with respect to the reference period between 1967 and 1996. Hydrological simulations based on a fourth climate scenario however point toward wetter conditions. In all cases the changes are minor. Although our simulations indicate that the experimental alley cropping system will possibly suffer drier conditions in response to higher temperatures and increased evaporative demand, these conditions are not necessarily critical for vegetation during the snow-free season.