Spatial Distribution of Soil Heat Flux Under a Sour Cherry Tree

Abstract

AbstractThis paper presents data on the spatial variability of surface soil heat flux in an orchard (Prunus cerasus L.), evaluates the error involved in estimating the surface soil heat flux, and develops a method by which a spatial average may be taken. Surface soil heat flux was calculated from measurements of the heat flux at the approximately 5‐cm depth and of the heat stored above the heat flux plate. The heat flux plate calibrations were corrected for the thermal conductivity of the soil as measured in situ. Measurements were made at six sites both under an orchard tree and in the open between trees. Results showed that the nighttime flux under the tree was occasionally < 50% of the values measured in the open. In contrast, the daytime spatial and temporal variability was very high and occasionally a small upward flux was recorded under the trees while a near maximum downward flux was being recorded in the open or under the tree a short time earlier or later. A spatial average was calculated by weighting the soil heat flux values by the area of the orchard they represented using an integration procedure. The spatial averages showed that 50–80% of the nighttime net radiation loss from the orchard was derived from the soil.