Effect of tree shelter design on water condensation and run-off and its potential benefit for reforestation establishment in semiarid climates

Tree shelters are able to act as radiative condensers and so harvest dew in significant amounts, although previous studies have overlooked this fact. This influence on dew harvesting and its quantification through soil water supply as a function of tree shelter single and double wall design was studied in a plantation trial of Pinus halepensis for two different walled shelters. A continuous monitoring of microclimate, soil water content and seedling development was accomplished. Both shelters had higher dew point temperature and lower minimum temperatures which conducted to an increment of dew formation, although the only shelter with single wall structure and semicircular microtubes registered a significant increase in soil moisture. This difference was associated with a poorer dew run-off process in the twin-wall shelter, indicating a design effect. However, seedling height growth in the single walled shelter was smaller indicating that only when soil moisture becomes over 6% does affect growth. Since in Mediterranean climate water is the principal restriction to plant establishment, the importance of dew formation may be significant in tree shelter design as related to plant survival and growth.