Sap flow in Al Ghaf trees growing in the hyper-arid desert of Abu Dhabi

W. Al Yamani, S.R. Green, R. Pangilinan, S. Dixon, P. Kemp, B.E. Clothier
The arid forests of Abu Dhabi provide a variety of valuable provisioning, regulating and cultural ecosystem services. However, given the hyper-arid environment, they also require irrigation for tree survival. Our research goal here is to establish how much water the trees use when irrigated by groundwater (GW). We are carrying out experiments at Madinat Zayed in the western desert on a range of forest species. We report results from Al Ghaf trees (Prosopis cineraria) planted on a 7×7 m grid. Tree water use is measured using the compensation heat-pulse method (CHPM) with sensors implanted into the trunks of four trees. Irrigation is supplied via in-line drippers (two tree-1) using saline groundwater with an electrical conductivity (EC) of about 8-10 dS m-1. Data are presented to illustrate the daily patterns of tree water use in response to the prevailing microclimate. During the cooler times of the year, when maximum air temperatures (Tmax ~30°C) and vapour pressure deficits (VPD ~3 kPa) are lower, the diurnal pattern of sap flow follows the potential evaporative demand (ETo). During the hottest times of the year, when Tmax is approaching 50°C and VPD GROTERDAN6 kPa, we observe a mid-day depression of sap flow relative to ETo. Stomatal control appears to be an important adaptive response used by Al Ghaf trees to reduce their water loss during periods of high evaporative demand.
Al Yamani, W., Green, S.R., Pangilinan, R., Dixon, S., Kemp, P. and Clothier, B.E. (2018). Sap flow in Al Ghaf trees growing in the hyper-arid desert of Abu Dhabi. Acta Hortic. 1222, 127-134
DOI: 10.17660/ActaHortic.2018.1222.28
compensation heat-pulse, crop factor, irrigation, modelling, Prosopis cineraria

Acta Horticulturae