Repeated freeze-thaw events affect leaching losses of nitrogen and dissolved organic matter in a forest soil
Repeated freeze-thaw events affect leaching losses of nitrogen and dissolved organic matter in a forest soil
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DOI：
10.1002/jpln.200700154
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发表时间：
2008-10-01
影响因子：
2.5
通讯作者：
Matzner, Egbert
中科院分区：
文献类型：
--
作者：
Hentschel, Kerstin;Borken, Werner;Matzner, Egbert
冻融作用对土壤中C和N的循环速率有很大影响，土壤冻融可引起森林生态系统中NO3-的渗漏损失。在这里，我们测试的假设，冻融触发N和溶解性有机质（DOM）从森林土壤解冻后释放，低冻结温度增强效果。未受干扰的土柱，从土壤中的挪威云杉网站要么只包括O层或O层+矿质土壤层。在-3 ° C、-8 ° C和-13 ° C的温度下对柱进行三次冻融循环。对照柱保持恒定+5 ℃。在霜冻事件之后，以4 mm d（-1）的速率对柱进行灌溉20 d。渗滤液进行了分析，总氮，矿质氮，溶解有机碳（DOC）。在170 d的试验期内，对照组从O层中提取的矿质氮总量为8.6gNm（-2）。霜冻减少了从土柱中浸出的矿物氮的量，-8摄氏度和-13摄氏度是最有效的。在这些处理中，只有3.1和4.0 g N m（-2）提取的O层。净硝化作用比净氨化作用受到更大的负面影响。严重的土壤霜冻增加了DOC从O层的释放，但只观察到在第一个冻融循环的效果。我们没有发现土壤霜冻后微生物裂解的证据。我们的实验并没有证实土壤冻融后增加氮矿化的假设。额外释放的DOC的总量是相当低的预期年通量。
Freezing and thawing may substantially influence the rates of C and N cycling in soils, and soil frost was proposed to induce NO3- 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 degrees C, -8 degrees C, and -13 degrees C. The control columns were kept at constant +5 degrees 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 degrees C and -13 degrees 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.