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Repeated freeze–thaw events affect leaching losses of nitrogen and dissolved organic matter in a forest soil
Author(s) -
Hentschel Kerstin,
Borken Werner,
Matzner Egbert
Publication year - 2008
Publication title -
journal of plant nutrition and soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 87
eISSN - 1522-2624
pISSN - 1436-8730
DOI - 10.1002/jpln.200700154
Subject(s) - dissolved organic carbon , leaching (pedology) , chemistry , soil water , organic matter , cycling , experimental forest , frost heaving , soil horizon , nitrification , soil organic matter , environmental chemistry , nitrogen , agronomy , soil science , environmental science , ecology , geology , forestry , geotechnical engineering , organic chemistry , biology , geography
Freezing and thawing may substantially influence the rates of C and N cycling in soils, and soil frost was proposed to induce NO $ _3^- $ losses with seepage from forest ecosystems. Here, we test the hypothesis that freezing and thawing triggers N and dissolved organic matter (DOM) release from a forest soil after thawing and that low freezing temperatures enhance the effect. Undisturbed soil columns were taken from a soil at a Norway spruce site either comprising only O horizons or O horizons + mineral soil horizons. The columns were subjected to three cycles of freezing and thawing at temperatures of –3°C, –8°C, and –13°C. The control columns were kept at constant +5°C. Following the frost events, the columns were irrigated for 20 d at a rate of 4 mm d –1 . Percolates were analyzed for total N, mineral N, and dissolved organic carbon (DOC). The total amount of mineral N extracted from the O horizons in the control amounted to 8.6 g N m –2 during the experimental period of 170 d. Frost reduced the amount of mineral N leached from the soil columns with –8°C and –13°C being most effective. In these treatments, only 3.1 and 4.0 g N m –2 were extracted from the O horizons. Net nitrification was more negatively affected than net ammonification. Severe soil frost increased the release of DOC from the O horizons, but the effect was only observed in the first freeze–thaw cycle. We found no evidence for lysis of microorganisms after soil frost. Our experiment did not confirm the hypothesis that soil frost increases N mineralization after thawing. The total amount of additionally released DOC was rather low in relation to the expected annual fluxes.