Technical Abstract: This chapter describes general characteristics and components of the energy and water balances in arid regions, with specific examples from the Jornada Basin. Various research efforts to characterize the energy and water balances and resultant carbon dioxide fluxes in the Jornada Basin are detailed. We provide a brief overview of how plant physiology interacts with energy and water balances in this region. The purpose of this chapter is to characterize the general abiotic conditions and some physiological traits of plants in this semiarid region.