Vineyard energy partitioning between canopy and soil surface: dynamics and biophysical controls

Abstract

or sparse planting crops, soil surface plays an important role in energy balances processes within the soil-canopy-atmosphere continuum, thus it?s necessary to partition field energy fluxes into soil surface and canopy, to provide useful information to reduce agricultural water use and develop evapotranspiration models. Field experiments were conducted in vineyard during four growing seasons, to examine the energy partitioning among soil surface, canopy and field separately. Vineyard energy fluxes including latent heat ( LE ) were measured by eddy covariance system, and canopy latent heat (LEc) was obtained from sap flow, then latent heat from soil surface (LEs) was calculated as the differences between LE and LEc. Bowen ratio and the ratio of latent heat to available energy were used to examine energy partitioning. Results indicate daily and hourly LEs obtained from LE and LEc overestimated microlysimeters derived values by 13.0 and 10.8% respectively. Seasonal average latent heat accounted for 59.0-64.3, 65.8-77.8 and 56.6-62.5% of corresponding available energy for vineyard, canopy and soil surface, respectively. Soil water content and canopy were the main controlling factors on energy partitioning. Surface soil moisture explained 32, 11 and 52% of the seasonal variability in energy partitioning at field, canopy and soil surface, respectively. LAI explained 41 and 26% of the seasonal variability in energy partitioning at field and soil surface. Air temperature was related to canopy and field energy partitioning. During wet periods, soil can absorb sensible heat from canopy and LEs may exceed soil surface available energy. While during dry periods, canopy may absorb sensible heat from soil and LEc may exceed canopy available energy.