Soil moisture and vegetation controls on evapotranspiration in a heterogeneous Mediterranean ecosystem on Sardinia, Italy

被引:182
作者
Detto, Matteo
Montaldo, Nicola
Albertson, John D.
Mancini, Marco
Katul, Gaby
机构
[1] Politecn Milan, Dipartimento Ingn Idraul Ambientale Infrastruct V, I-20133 Milan, Italy
[2] Duke Univ, Pratt Sch Engn, Dept Civil & Environm Engn, Durham, NC 27708 USA
[3] Duke Univ, Nicholas Sch Environ & Earth Sci, Durham, NC USA
关键词
D O I
10.1029/2005WR004693
中图分类号
X [环境科学、安全科学];
学科分类号
08 ; 0830 ;
摘要
[ 1] Micrometeorological measurements of evapotranspiration ( ET) can be difficult to interpret and use for validating model calculations in the presence of land cover heterogeneity. Land surface fluxes, soil moisture (theta), and surface temperatures (T-s) data were collected by an eddy correlation-based tower located at the Orroli ( Sardinia) experimental field ( covered by woody vegetation, grass, and bare soil) from April 2003 to July 2004. Two Quickbird high-resolution images ( summer 2003 and spring 2004) were acquired for depicting the contrasting land cover components. Aprocedure is presented for estimating ET in heterogeneous ecosystems as the residual term of the energy balance using Ts observations, a two-dimensional footprint model, and the Quickbird images. Two variations on the procedure are successfully implemented: a proposed two-source random model (2SR), which treats the heat sources of each land cover component separately but computes the bulk heat transfer coefficient as spatially homogeneous, and a common two-source tile model. For 2SR, new relationships between the interfacial transfer coefficient and the roughness Reynolds number are estimated for the two bare soil - woody vegetation and grass - woody vegetation composite surfaces. The ET versus theta relationships for each land cover component were also estimated, showing that that the woody vegetation has a strong tolerance to long droughts, transpiring at rates close to potential for even the driest conditions. Instead, the grass is much less tolerant to theta deficits, and the switch from grass to bare soil following the rainy season had a significant impact on ET.
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页数:16
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