Winter cover cropping increases albedo and latent heat flux in the Texas High Plains

Abstract:

Winter cover crops represent a land-use change that may sequester carbon in the soil and improve agriculture sustainability, while potentially also changing the Earth’s radiative balance and resulting biophysical feedbacks to climate through alterations in albedo and latent heat fluxes. Understanding the mechanisms underlying these alterations to the radiative balance is important for making reliable future climate projections. However, data on cover crop biophysics is nearly non-existent and previous modeling studies have been forced to use data from summer plants for parameterization, likely biasing predictions. The goal of this project was to determine how climate and leaf traits impact winter albedo and evapotranspiration with and without cover crops in the Texas High Plains, a cold semi-arid ecosystem with low annual rainfall. We set up a winter cover crop experiment with Secale cereale, xTriticosecale [Secale × Triticum], and fallow fields to estimate the change in albedo and latent heat flux that results from a switch to winter cover cropping. The albedo of winter cover crops was higher than the soil albedo, resulting in an increase in top-of-atmosphere reflected radiation of 7–14% when converting from fallow fields to cropped fields. There was an additional cooling effect through an over 100% increase in latent heat flux due to the presence of cover crops, resulting in an overall cooling effect of winter cover crops. While this effect is likely to be region-specific, these results strongly indicate that winter cover crops play an important role in determining the surface albedo and latent heat flux of agricultural fields and will provide a direct cooling effect in this region. The connection between climate, soil, and leaf-level drivers of crop albedo presented here can be used to more accurately predict these biophysical effects in land surface models.