Ecohydrology of a seasonal cloud forest in Dhofar

The hydrology of a semiarid broadleaf forest in Dhofar (Oman) is investigated by performing a field experiment and a modeling study. Based on the results of the field experiment, the ecosystem in Dhofar is classified, for the first time, as a seasonal deciduous cloud forest. Owing to the seasonal cloud cover, the soil storage in this ecosystem is filled and emptied in such a fashion that allows trees to allocate most of the water to transpiration by their relatively deep roots. In addition to annual rainfall amounts of about 100 millimeters, more water is gained by trees directly through interception of cloud droplets (horizontal precipitation). Through- fall measured below the canopy is about twice the rainfall measured above the canopy. Stemflow contributes about one third of the total water received by the soil. Soil moisture observations are consistent with increased infiltration in proximity of the tree trunks. Sap flow and meteorological observations indicate that transpiration is suppressed during the wet season, which allows for deep infiltration of the water received at the surface. This soil water storage supports transpiration by the relatively deep-rooted trees for up to four month into the dry season. All these factors combine to shape and enhance the water conserving nature of the ecosystem, and to allow for tree dominance in an otherwise too dry environment. A dynamical vegetation model is used to investigate tree- grass competition in this arid region. The model simulations elucidate the role of clouds in reducing the available energy for transpiration during the wet season. Without representing this role in the model, the simulated soil water storage by the end of the wet season is not enough to allow for tree survival and dominance.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Civil and Environmental Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2005

Author dc:creator

• Hildebrandt, Anke, 1975-

Advisor dc:contributor.advisor

• Elfaith A.B. Eltahir.

• Civil and Environmental Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/31135

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/31135