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Deep Soil Water Dynamics and Depletion by Secondary Vegetation in the Eastern Amazon

^a ZEF, Center for Development Research, Univ. of Bonn, Walter-Flex-Str. 3, 53113 Bonn, Germany
^b Institute of Soil Science and Forest Nutrition, Univ. of Göttingen, Büsgenweg 5, 37077 Göttingen, Germany
^c EMBRAPA Amazônia Oriental, Trav. Dr. Enéas Pinheiro s/n, Cx. Postal 48, 66095-100 Belém–Pará, Brazil
^d CIMMYT, Apdo. Postal 6-641, 06600 Mexico, D.F., Mexico

View larger version (19K): [in a new window]   Fig. 1. Textural distribution and percentage of clay-flocculation (Brazilian classification) of the soil of the study site, as well as the mean soil bulk density of the soil of a neighbored 5-yr-old fallow (according to earlier studies; n = 16, bars denote the SE).

View larger version (33K): [in a new window]   Fig. 2. Daily precipitation of the study area in 1997 and 1998.

View larger version (28K): [in a new window]   Fig. 3. Relative mean throughfall (PT) under the fallow vegetation in 1997 and 1998 (Sá, personal communication, 1999); dotted straight line: linear regression (R2 = 0.212, n = 64), gray line: linear regression of 95% confidence intervals of PT, dotted upper line: calculated relative net precipitation.

View larger version (21K): [in a new window]   Fig. 4. Mean root mass density of 1- to 12-yr-old fallow vegetation (according to Sommer et al., 2000; n = 60, bars denote the SE), its cumulative percentage distribution (secondary x axis) and the distribution as entering the soil water model.

View larger version (39K): [in a new window]   Fig. 5. Soil water retention and hydraulic conductivity of the three distinguished soil increments; the scaling range is given by the lowest and highest values of K and (in combination with r) of Table 4.

View larger version (35K): [in a new window]   Fig. 6. Observed and predicted pressure head dynamics at 30, 90, 300, 600, and 735 cm over the 2-yr observation period.

View larger version (16K): [in a new window]   Fig. 7. Observed and predicted soil water contents on 6 Nov. and 10 Dec. 1997 (bars denote SE of n = 2).

View larger version (22K): [in a new window]   Fig. 8. Water contents measured by means of neutron probe in relation to model predictions of different times during the rainy season and transitional period of 1998 as well as those gravimetrically determined on 6 Nov. and 10 Dec. 1997 (values below 0.17) distinguished according to the measuring depth.

View larger version (20K): [in a new window]   Fig. 9. Relation of modeled to micrometeorologically observed transpiration (TModel/Ta) during the 2-yr observation period.

View larger version (25K): [in a new window]   Fig. 10. Modeled soil water content over the 10-m profile on 30 Mar. 1997 (maximum soil water storage), 22 Aug. 1997 (beginning dry season), and 8 Jan. 1998 (minimum soil water storage).

View larger version (43K): [in a new window]   Fig. 11. Soil water storage dynamics of 0- to 6- and 6- to 10-m soil depth in 1997 and 1998.