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首页> 外文期刊>Global change biology >The input and fate of new C in two forest soils under elevated CO2
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The input and fate of new C in two forest soils under elevated CO2

机译：CO2浓度升高时两种森林土壤中新碳的输入和分配

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The aim of this study was to estimate (i) the influence of different soil types on the net input of new C into soils under CO2 enrichment and (ii) the stability and fate of these new C inputs in soils. We exposed young beech-spruce model ecosystems on an acidic loam and calcareous sand for 4 years to elevated CO2. The added CO2 was depleted in C-13, allowing to trace new C inputs in the plant-soil system. We measured CO2-derived new C in soil C pools fractionated into particle sizes and monitored respiration as well as leaching of this new C during incubation for 1 year. Soil type played a crucial role in the partitioning of C. The net input of new C into soils under elevated CO2 was about 75% greater in the acidic loam than in the calcareous sand, despite a 100% and a 45% greater above- and below-ground biomass on the calcareous sand. This was most likely caused by a higher turnover of C in the calcareous sand as indicated by 30% higher losses of new C from the calcareous sand than from the acidic loam during incubation. Therefore, soil properties determining stabilization of soil C were apparently more important for the accumulation of C in soils than tree productivity. Soil fractionation revealed that about 60% of the CO2-derived new soil C was incorporated into sand fractions. Low natural C-13 abundance and wide C/N ratios show that sand fractions comprise little decomposed organic matter. Consistently, incubation indicated that new soil C was preferentially respired as CO2. During the first month, evolved CO2 consisted to 40-55% of new C, whereas the fraction of new C in bulk soil C was 15-23% only. Leaching of DOC accounted for 8-23% of the total losses of new soil C. The overall effects of CO2 enrichment on soil C were small in both soils, although tree growth increased significantly on the calcareous sand. Our results suggest that the potential of soils for C sequestration is limited, because only a small fraction of new C inputs into soils will become long-term soil C. [References: 33]
机译：这项研究的目的是估计（i）在CO2富集下不同土壤类型对新C净输入的影响，以及（ii）这些新C在土壤中的稳定性和结局。我们在酸性壤土和钙质砂土上暴露了年轻的山毛榉-云杉模式生态系统长达4年，使二氧化碳含量升高。添加的二氧化碳在C-13中被消耗掉，从而可以追踪植物-土壤系统中的新C输入。我们测量了土壤C池中CO2衍生的新C，并将其分解成颗粒大小，并监测了呼吸以及在培养1年期间该新C的浸出。土壤类型在碳的分配中起着至关重要的作用。在酸性壤土中，新的碳在土壤中的净输入量比钙质砂高出约75％，尽管高于和高于钙质砂土分别为100％和45％。钙质砂下的地下生物量。这很可能是由于钙质砂中C的周转率较高所致，这表明，在孵化过程中，钙质砂中新C的损失比酸性壤土高出30％。因此，确定土壤碳稳定性的土壤特性对于土壤中碳的积累显然比树木生产力更为重要。土壤分馏显示，约有60％的源自CO2的新土壤C被掺入了沙子组分中。低的天然C-13丰度和宽的C / N比表明，砂级分几乎没有分解的有机物。一致地，温育表明新的土壤C被优先呼吸为CO2。在第一个月中，释放出的二氧化碳占新碳的40-55％，而散装土壤中新碳的比例仅为15-23％。 DOC的淋溶占新土壤C总损失的8-23％。尽管在钙质砂土上树木生长显着增加，但两种土壤中CO2富集对土壤C的总体影响均很小。我们的结果表明，土壤固碳的潜力是有限的，因为只有一小部分新的碳输入土壤会变成长期的土壤碳。[参考文献：33]

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