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首页> 外文期刊>Plant and Soil >Effects of atmospheric CO sub(2) enrichment on delta super(13)C, delta super(15)N values and turnover times of soil organic matter pools isolated by thermal techniques
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Effects of atmospheric CO sub(2) enrichment on delta super(13)C, delta super(15)N values and turnover times of soil organic matter pools isolated by thermal techniques

机译：大气CO sub（2）富集对热技术分离的土壤有机质库中δsuper（13）C，delta super（15）N值和周转时间的影响

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摘要

CO sub(2) applied for Free-Air CO sub(2) Enrichment (FACE) experiments is strongly depleted in super(13)C and thus provides an opportunity to study C turnover in soil organic matter (SOM) based on its delta super(13)C value. Simultaneous use of super(15)N labeled fertilizers allows N turnover to be studied. Various SOM fractionation approaches (fractionation by density, particle size, chemical extractability etc.) have been applied to estimate C and N turnover rates in SOM pools. The thermal stability of SOM coupled with C and N isotopic analyses has never been studied in experiments with FACE. We tested the hypothesis that the mean residence time (MRT) of SOM pools is inversely proportional to its thermal stability. Soil samples from FACE plots under ambient (380 ppm) and elevated CO sub(2) (540 ppm; for 3 years) treatments were analyzed by thermogravimetry coupled with differential scanning calorimetry (TG-DSC). Based on differential weight losses (TG) and energy release or consumption (DSC), five SOM pools were distinguished. Soil samples were heated up to the respective temperature and the remaining soil was analyzed for delta super(13)C and delta super(15)N by IRMS. Energy consumption and mass losses in the temperature range 20-200 degree C were mainly connected with water volatilization. The maximum weight losses occurred from 200-310 degree C. This pool contained the largest amount of carbon: 61% of the total soil organic carbon in soil under ambient treatment and 63% in soil under elevated CO sub(2), respectively. delta super(13)C values of SOM pools under elevated CO sub(2) treatment showed an increase from -34.3ppt of the pool decomposed between 20-200 degree C to -18.1ppt above 480 degree C. The incorporation of new C and N into SOM pools was not inversely proportional to its thermal stability. SOM pools that decomposed between 20-200 and 200-310 degree C contained 2 and 3% of the new C, with a MRT of 149 and 92 years, respectively. The pool decomposed between 310-400 degree C contained the largest proportion of new C (22%), with a MRT of 12 years. The amount of fertilizer-derived N after 2 years of application in ambient and elevated CO sub(2) treatments was not significantly different in SOM pools decomposed up to 480 degree C having MRT of about 60 years. In contrast, the pool decomposed above 480 degree C contained only 0.5% of new N, with a MRT of more than 400 years in soils under both treatments. Thus, the separation of SOM based on its thermal stability was not sufficient to reveal pools with contrasting turnover rates of C and N.
机译：应用于自由空气的CO子（2）富集（FACE）实验中的CO子（2）在super（13）C中被大量消耗，因此为基于其δ超级的土壤有机质（SOM）中的碳更新研究提供了机会（13）C值。同时使用super（15）N标记的肥料可以研究N的转换。各种SOM分馏方法（按密度，粒度，化学可萃取性进行分馏）已用于估算SOM池中的C和N周转率。从未在FACE实验中研究过SOM的热稳定性以及C和N同位素分析。我们测试了SOM池的平均停留时间（MRT）与它的热稳定性成反比的假设。通过热重分析和差示扫描量热法（TG-DSC）分析了在环境（380 ppm）和升高的CO sub（2）（540 ppm; 3年）处理下FACE小区的土壤样品。根据差异重量损失（TG）和能量释放或消耗（DSC），区分了五个SOM库。将土壤样品加热到各自的温度，并通过IRMS分析剩余的土壤的delta super（13）C和delta super（15）N。 20-200摄氏度温度范围内的能量消耗和质量损失主要与水挥发有关。最大失重发生在200-310摄氏度之间。该池含碳量最大：环境处理土壤中有机碳总量的61％，CO浓度升高（2）下土壤有机碳总量的63％。在升高的CO sub（2）处理下，SOM池的delta super（13）C值显示从20-200摄氏度之间分解的-34.3ppt的池增加到480℃以上-18.1ppt的分解。进入SOM池中的氮与其热稳定性不成反比。在20-200到200-310摄氏度之间分解的SOM池包含新C的2％和3％，MRT分别为149年和92年。在310-400摄氏度之间分解的池包含了新碳的最大比例（22％），其MRT为12年。在环境和升高的CO sub（2）处理中施用2年后，源自肥料的氮的量在分解至480摄氏度，MRT约为60年的SOM池中没有显着差异。相比之下，在两种处理下，在480摄氏度以上分解的水池仅含有0.5％的新氮，其MRT超过400年。因此，基于其热稳定性的SOM分离不足以揭示具有相反C和N周转率的池。

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