Net CO2 uptake for Agave tequilana in a warm and a temperate environment

The main objective was to evaluate the effects of seasonal variations in ai r temperature, soil water content, and irradiation on the net rate of CO2 u ptake for Agave tequilana growing in a warm subtropical environment (Amatit an, Jalisco, Mexico) and in a temperate subtropical environment (Arandas, J alisco, Mexico). At Amatitan, the lowest value of positive daily net CO2 up take (141 mmol/m(2)/d) occurred at the end of the summer rainy season and t he highest values during the winter (578 and 921 mmol/m(2)/d); at Arandas, the lowest value (188 mmol/m(2)/d) occurred at midsummer and the highest va lues at the end of the summer (763 mmol/m(2)/d) and in late winter (572 mmo l/m(2)/ d). The highest values of daily net CO2 uptake in both localities r eflected prolonged daily periods of net CO2 uptake thar included both dayti me and nighttime assimilation accompanied by high rates of nocturnal net CO 2 uptake doe to moderate nighttime air temperatures. High temperatures in t he summer reduced daily net CO2 uptake at both localities bur in late summe r, the nighttime temperatures ac Arandas were moderate, which lead to high daily net CO2 uptake. Leaf succulence allowed substantial daily net CO2 upt ake when the soil water content was relatively low during the winter and th e spring (January-March). Indeed, appreciable daily net CO2 uptake occurred throughout the year for A. tequilana at both localities, indicating that t his CAM plant species can sequester carbon even during prolonged dry period s.