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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >Impacts of chronic N input on the carbon and nitrogen storage of a postfire Mediterranean-type shrubland
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Impacts of chronic N input on the carbon and nitrogen storage of a postfire Mediterranean-type shrubland

机译：长期氮输入对地中海大火后灌木丛碳氮存储的影响

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Mediterranean-type shrublands are subject to periodic fire and high levels of nitrogen (N) deposition, but little is known how chronic N deposition affects carbon (C) and N storage during succession. We conducted a long-term experiment in Californian chaparral to test the hypothesis that chronic N enrichment would increase postfire C and N accumulation. The experimental layout consisted of a randomized design where four 10 × 10mplots received 5 g Nm~(-2) annually since 2003 and four 10 × 10m plots served as controls. Aboveground and belowground C and N pools and fluxes were measured seasonally (every 3months) for a period of 10 years. Added N rapidly increased soil extractable N pools and decreased soil pH; however, total soil C and N storage were not affected. Added N plots initially had significantly lower C and N storage than control plots, presumably because of nutrient losses from leaching and/or higher belowground C allocation. However, rates of aboveground N and C storage became significantly higher in added N plots after 4–5 years of exposure, thus increasing fuel buildup, which has implications for future fire intensity. This recovering chaparral stand is not yet “N saturated” after 10 years of chronic N input. However, N leaching continues to be higher in added N plots, indicating that postfire chaparral stands in high-N deposition areas can be important sources of N to groundwater/aquatic systems even if productivity is stimulated by N input.
机译：地中海型灌木丛经常遭受大火和高水平的氮（N）沉积，但人们几乎不知道长期的氮沉积如何在演替过程中影响碳（C）和氮存储。我们在加利福尼亚州丛林进行了一项长期实验，以检验长期富氮会增加大火后碳和氮积累的假说。实验布局由随机设计组成，自2003年以来，每年有4个10×10m的样地接受5 g Nm〜（-2），并以4个10×10m的样地作为对照。定期（每3个月）对地下和地下C和N池和通量进行测量，为期10年。增加的氮迅速增加了土壤可提取的氮库，降低了土壤的pH值;但是，土壤总碳和氮的储存量不受影响。最初添加的N个地块的C和N储藏量比对照地块低得多，这大概是由于淋溶养分流失和/或地下C分配增加所致。但是，在暴露4-5年后，在增加的N个地块中，地上N和C的存储速率显着提高，从而增加了燃料积聚，这对未来的火灾强度有影响。经过10年的长期氮输入后，这种恢复的睑板架仍未“饱和”。但是，在增加的N个图上，N的淋溶作用仍然较高，这表明即使N输入增加了生产力，高N沉积区的后燃林也可能是地下水/水系统N的重要来源。

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