LAUSR

Precipitation that is intercepted by vegetation is generally considered as lost to the terrestrial hydrological cycle. However, if it is absorbed by the plants or reduces their transpiration, the intercepted water contributes positively to forest hydrology. The aim of this study was to investigate the absorption of intercepted water by a conifer and an angiosperm tree species. Pots of 2–3-year-old plants of × Cupressocyparis leylandii and Quercus robur were wrapped in plastic bags to exclude stemflow and throughfall from their water supply. Samples of both species were conditioned to two levels of aboveground wetting (sprinkled or un-sprinkled) and two levels of soil moisture (dry or moist). The periodical sprinkling with water droplets, lasting 5 h during two nights and 10 h in 1 day, ensured continuous aboveground wetting of plants during these periods. Weight changes of the plants were monitored after air drying in darkness for 3 h and wiping off any remaining surface water. Absorption of intercepted water was apparent for both species at night, when transpiration was close to zero. During the day, sprinkled plants of Q. robur had reduced rates of transpiration. For C. leylandii on dry soil sprinkling reduced water consumption during the first 24 h by 9%, while for Q. robur, the reductions were 46% and 27% for plants on dry and moist soils, respectively. These reductions in water consumption following sprinkling indicate that transpiration reduction and absorption of intercepted water deserve attention in studies of forest hydrology.