The Role of Rapid Flow Paths for Nitrogen Transformation in a Forest Soil
A Field Study with Micro Suction Cups
Frank Hagedorna,
Joachim Mohnb,
Patrick Schleppia and
Hannes Flühlerc
a Swiss Federal Inst. for Forest, Snow and Landscape Research (WSL), Zürcherstr. 111, CH-8903 Birmensdorf, Switzerland
b Inst. of Plant Biology/Microbiology, Univ. of Zürich, Zollikerstr. 107, CH-8008 Zürich, Switzerland
c Inst. of Terrestrial Ecology, ETH Zürich, Grabenstr. 11, CH-8952 Schlieren, Switzerland
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Fig. 1 Micro suction cups: construction and instrumental array in the field
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Fig. 2 Distribution of mean NO-3 concentrations and relative frequencies at individual depths. Means and standard errors of three sampling dates
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Fig. 3 Soil redox potentials at different depths and water table position during the N-addition experiment. Lines represent individual redox electrodes
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Fig. 5 Chloride concentrations in the soil solution of flow paths and soil matrix at the 3- and 5-cm depths. Due to the small sample volumes, the samples were bulked during the experiment. Standard errors represent the variability of collected solution at Day 20 (3-cm depth in soil matrix: n = 6; 3-cm depth in flow path: n = 4; 5-cm depth in soil matrix: n = 8). The 5 mM Cl- m-2 was applied at the end of the simulated rainfall of 18 mm
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Fig. 7 Breakthrough curves of NH+4 and SO2-4 at various depths. The 5 mM NH+4 m-2 and 2.5 mM SO2-4 m-2 were applied after 8 mm of rain, followed by an additional 6 mm of rain. This resulted in a concentration of 360 µM NH+4 and 180 µM SO2-4 in the rainwater. The detection limit of NH+4 was 10 µM
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Fig. 4 Relation of NO-3 concentrations to locations of microcups characterized based on Brilliant Blue FCF recovery (flow path = high recovery). Nitrate concentrations of each microcup are the mean of three sampling dates. Brilliant Blue recovery is the amount sampled by each microcup within 24 h after application
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Fig. 6 The
ratio in the soil solution during the N-addition experiment. Due to the small sample volumes, the samples were bulked. Standard errors were estimated at the first and the last sampling date
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Fig. 8 Denitrification rate and NO-3 concentrations at the 5- and 20-cm depths of the soil solution sampled by suction plates. Denitrifying activity was measured with three pairs of cores during the NH+4 addition and with four pairs of cores during the NO-3 addition. NO-3 concentrations are the mean of two suction plates, installed within 50 cm of the microcups
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Fig. 9 The K2SO4-extractable NO-3 concentrations of the bulk soil (0–5 cm) and fluxes within the soil compartment. Mean and mean spatial standard errors of five plots from May 1996 to November 1997. Sampling dates: n = 15 (K2SO4-extractable); n = 28 (denitrification); n = 30 (leached NO-3); NO-3 export from subcatchments (1500 m2), 1997
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Fig. 10 Comparison of solute concentrations from flow paths and soil matrix locations to solutes at the 3-, 4-, and 5-cm depths sampled by suction plates and to solutes of the runoff from the subcatchment. Suction plates were installed within 50 cm of the microcups. Data points represent mean concentrations of 3 wk
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Copyright © 1999 by the Soil Science Society of America.
