Water use of drought-tolerant coniferous trees (Pinus brutia and Cupressus sempervirens) in a semi-arid environment

Observing ecohydrological processes of indigenous, drought-tolerant trees in arid and semi-arid regions is of profound importance for assessing the suitability of plant species for future climate conditions. The objective of this study is to quantify transpiration and soil moisture of pine (Pinus brutia) and cypress (Cupressus sempervirens) trees. The study site is located in Athalassa Forest Park, in Cyprus. The site has a surface area of 10 ha with an average slope of 4%. Average annual rainfall is 315 mm with a mean daily minimum temperature of 5° C during January and a mean daily maximum temperature of 37° C during August. The site was converted in 2011 from rainfed agriculture to a mixed forest by planting seedlings of different tree and shrub species.

Six P. brutia and six C. sempervirens trees were randomly selected for sap flow monitoring with sensors (heat ratio method) attached to the tree trunks. Forty-five soil moisture sensors were installed under the canopy, the edge of canopy and areas with no tree canopy at depths of 10 cm, 30 cm and 50 cm. Data from November 2020 to December 2021 indicated that mean total transpiration per tree was higher for C. sempervirens (≅2.2 m³) than for P. brutia (≅1.3 m³). Total rainfall during these 14 months was 339 mm. Higher transpiration of cypress trees was also reflected in the soil moisture, as canopy area soil moisture contents were generally lower for cypress than for pine for the depths of 10 and 50 cm. After rain maximum soil moisture values were similar for cypress and pine at the depth of 30 cm but the reduction of soil moisture over time was quicker for cypress. 

This research has received support from the Water JPI (Joint Call 2018) FLUXMED Project, funded through the Cyprus Research and Innovation Foundation.