HR: 14:45h
AN: H43I-05    [Abstracts]
TI: Vegetation Dynamics and Soil Water Balance in a Water-limited Mediterranean Ecosystem on Sardinia, Italy
AU: * Montaldo, N
EM: nicola.montaldo@unica.it
AF: Dipartimento di Ingegneria del Territorio, Universita' di Cagliari, Via Marengo, 3, CAGLIARI, 09125, Italy
AU: Albertson, J D
EM: john.albertson@duke.edu
AF: Department of Civil and Environmental Engineering, Duke University, Box 90287; CIEMAS, Rm 2465, Durham, NC 27708-0287, United States
AU: Mancini, M
EM: marco.mancini@polimi.it
AF: DIIAR, Politecnico di Milano, Piazza Leonardo da Vinci, 32, MILANO, 20133, Italy
AB: Semi-arid regions, such as around the Mediterranean, suffer from broad desertification processes produced by both natural and human influences. Mediterranean ecosystems are commonly heterogeneous savanna-like ecosystems, with contrasting plant functional types (PFTs, e.g., grass and woody vegetation) competing for the water use. At the same time the structure and function of the vegetation regulates the exchange of mass, energy and momentum across the biosphere-atmosphere interface, influencing strongly the soil water budget. With the objective to investigate vegetation dynamics, soil water budget and land-surface fluxes interactions in a water-limited ecosystem, an extensive field campaign in a Mediterranean water-limited field is performed, and a parsimonious and robust vegetation dynamic model (VDM) is coupled to a 3-component (bare soil, grass and woody vegetation) LSM. The case study is in Orroli, situated in the mid-west of Sardegna within the Flumendosa river watershed. Sardinia is a region that suffers from water scarcity, and the Flumendosa basin plays a primary role in the water supply for much of southern Sardinia, including the island's biggest city, Cagliari. The site landscape is a mixture of Mediterranean patchy vegetation types: trees, including wild olives and cork oaks, different shrubs and herbaceous species. An extensive field campaign started in April 2003. More than three years of data are available. Interestingly, hydrometeorological conditions of the monitored years strongly differ, with dry and wet years in turn, and a wide range of hydrometeorological conditions can be analyzed. Land-surface fluxes and CO2 fluxes are estimated by an eddy correlation technique based micrometeorological tower. Soil moisture profiles were also continuously estimated using water content reflectometers and gravimetric method, and periodically leaf area index (LAI) estimates of both plant types are made using the Accupar LP-80 by Decagon Devices Inc. Furthermore, two high spatial resolution (2.8 m) Quickbird satellite images were acquired in August of 2003 and March 2004 for defining the spatial organization of the main land cover types around the tower for two contrasting seasons of the year (Summer and Spring). A parsimonious ecohydrologic model is developed. The VDM computes the change in biomass over time as difference between the rate of production (e.g., photosynthesis) and the rate of destruction (e.g., respiration and senescence). VDM incorporates two PFTs using basic rules regarding competition for a limiting resource. The VDM is then coupled to a 3-component LSM, with the VDM providing the green biomass and the LAI evolution through time, and the LSM using this information in the computation of the land surface fluxes and updating the soil water content in the root-zone. The coupled VDM-LSM model is successfully tested for the case study, demonstrating high model performance for the wide range of eco-hydrologic conditions. The inclusion of the VDM in the LSM is demonstrated to be essential when studying the climate-soil-vegetation interactions of these water-limited ecosystems. Results demonstrate also that vegetation dynamics are strongly influenced by the inter-annual variability of atmospheric forcing, with grass leaf area index changing significantly each spring season according to seasonal rainfall amount.
DE: 1813 Eco-hydrology
DE: 1818 Evapotranspiration
DE: 1843 Land/atmosphere interactions (1218, 1631, 3322)
DE: 1866 Soil moisture
DE: 1875 Vadose zone
SC: Hydrology [H]
MN: 2007 Fall Meeting