Ecohydrology of a seasonal cloud forest in Dhofar: 1. Field experiment

Abstract

We describe the ecohydrology of a unique semiarid broadleaf deciduous forest in Dhofar (Oman). The forest is surrounded by desert and is confined to a coastal area, where the summer wet season is characterized by a persistent dense cloud immersion. Using field observations, we show how clouds render the ecosystem particularly water conserving and therefore create a niche for a moist forest biome in a semiarid area in three ways. First, horizontal precipitation (collection of cloud droplets on tree canopies) added valuable water, such that about two times as much water was received below the canopy (net precipitation) compared to above (rainfall). Second, high stemflow, of about 30% to net precipitation, led to concentrated water input around the stems. Third, transpiration was suppressed during the cloudy summer season, which allowed for storage of the received water. It was only used after the end of the wet season and lasted for the following 3 months, which roughly doubled the length of the growing season. Our results demonstrate that cloud immersion may shape ecosystem hydrology in significant ways, particularly in semiarid environments.