Soil moisture dynamics in an eastern Amazonian tropical forest

被引:99
作者
Bruno, Rogerio D.
da Rocha, Humberto R.
de Freitas, Helber C.
Goulden, Michael L.
Miller, Scott D.
机构
[1] Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, Dept Atmospher Sci, IAG, BR-05508900 Sao Paulo, Brazil
[2] Univ Calif Irvine, Dept Earth Syst Sci, Irvine, CA 92697 USA
基金
巴西圣保罗研究基金会;
关键词
hydrology; soil moisture; root uptake; evapotranspiration; tropical forest; frequency-domain reflectometry; Amazonia; Tapajos National Forest; LBA;
D O I
10.1002/hyp.6211
中图分类号
TV21 [水资源调查与水利规划];
学科分类号
081501 ;
摘要
We used frequency-domain reflectometry to make continuous, high-resolution measurements for 22 months of the soil moisture to a depth of 10 m in an Amazonian rain forest. We then used these data to determine how soil moisture varies on diel, seasonal and multi-year timescales, and to better understand the quantitative and mechanistic relationships between soil moisture and forest evapotranspiration. The mean annual precipitation at the site was over 1900 mm. The field capacity was approximately 0.53 m(3) m(-3) and was nearly uniform with soil depth. Soil moisture decreased at all levels during the dry season, with the minimum of 0.38 m(3) m(-3) at 3 m beneath the surface. The moisture in the upper I m showed a strong diel cycle with daytime depletion due to evapotranspiration. The moisture beneath 1 m declined during both day and night due to the combined effects of evapotranspiration, drainage and a nighttime upward movement of water. The depth of active water withdrawal changed markedly over the year. The upper 2 m of soil supplied similar to 56% of the water used for evapotranspiration in the wet season and similar to 28% of the water used in the dry season. The zone of active water withdrawal extended to a depth of at least 10 m. The day-to-day rates of moisture withdrawal from the upper 10 m of soil during rain-free periods agreed well with simultaneous measurements of whole-forest evapotranspiration made by the eddy covariance technique. The forest at the site was well adapted to the normal cycle of wet and dry seasons, and the dry season had only a small effect on the rates of land-atmosphere water vapour exchange. Copyright (C) 2006 John Wiley & Sons, Ltd.
引用
收藏
页码:2477 / 2489
页数:13
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