Effect of soil moisture on canopy conductance of Amazonian rainforest

Estimates of canopy conductance, gc, were derived from hourly eddy-covariance measurements of evaporation for a primary forest site near Manaus, Brazil, using an inverted Penman–Monteith equation. These data were used to calibrate Jarvis-type models of canopy conductance including and excluding a soil moisture dependence. A period of low canopy conductance in the observations coincided with low soil moisture and high humidity deficit. The model was able to capture this decrease in diurnal maximum gc only when a soil moisture dependence was included. The optimised value of wilting point in the soil moisture function was 465 m3 m−3, which was comparable with estimates from soil hydraulic properties.