The influence of soil processes on carbon isotope distribution and turnover in the British uplands
The influence of soil processes on carbon isotope distribution and turnover in the British uplands
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DOI：
10.1046/j.1365-2389.1999.00222.x
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发表时间：
1999-03-01
影响因子：
4.2
通讯作者：
Howard, DM
中科院分区：
文献类型：
--
作者：
Bol, RA;Harkness, DD;Howard, DM
了解土壤内以及土壤类型之间碳的自然变化对于改进高纬度和中纬度生态系统应对全球变暖的碳循环预测模型至关重要。我们测量了来自英国高地的灰化土、棕色灰化土和滞腐灰土的土壤有机质 (SOM) 中的碳同位素分布（C-12、C-13 和 C-14），然后将其与这些土壤中的碳总量和周转进行比较。为此，我们对每种土壤类型的六个剖面以 2 厘米的间隔进行采样。 Stagnohumic Gleysols 顶部 28 厘米的平均碳储存量是其他两种土壤的两倍。所有土壤的C-13含量和C-14年龄普遍随深度增加而增加，同位素变化与主要成土特征之间也存在显着的相关性。后者表明土壤形成过程对于确定 SOM 中保留的碳同位素特征具有重要意义。 1960 年以来形成的有机物在任何土壤中均未发现低于 5 厘米。显然，表层（LF 和 Oh）中的有机碎屑迅速矿化。这与我们模拟的年净碳通量一致，该模型表明这些土壤排放的二氧化碳超过 80% 来自每个剖面的顶部 5 厘米。尽管这些土壤含有大量碳，但它们似乎不能快速同化和保留 SOM。大多数碳的平均停留时间在 2-50 年范围内，因此土壤对于大气中过量的二氧化碳来说是相当无效的汇。在预测的未来“温室”气候下，这些土壤可能有利于微生物更快地分解有机物质，因此是二氧化碳的潜在来源，因此可能会加速全球变暖。
Understanding the natural variation of carbon within the soil, and between soil types, is crucial to improve predictive models of carbon cycling in high and mid-latitude ecosystems in response to global warming. We measured the carbon isotope distributions (C-12, C-13 and C-14) in soil organic matter (SOM) from Podzols, Brown Podzolic soils and Stagnohumic Gleysols from the British uplands, which were then compared with the total amounts and turnover of carbon in these soils. We did so by sampling at 2-cm intervals down six profiles of each soil type. The average amount of carbon stored in the top 28 cm of the Stagnohumic Gleysols is twice that of the other two soils. The C-13 content and C-14 age show a general increase with depth in all soils, and there is also a significant correlation between isotopic variation and the main pedogenic features. The latter suggests that soil-forming processes are significant in determining the carbon isotope signatures retained in SOM. Organic matter formed since 1960 is not found below 5 cm in any of the soils. Evidently organic detritus in the surface layers (LF and Oh) is rapidly mineralized. This accords with our modelled net annual C fluxes which show that more than 80% of the CO2 emanating from these soils is derived from the top 5 cm of each profile. Although these soils contain much carbon, they do not appear to assimilate and retain SOM rapidly. The mean residence time of most of their carbon is in the 2-50 years range, so the soils are fairly ineffective sinks for excess CO2 in the atmosphere. Under the predicted future 'greenhouse' climate, likely to favour more rapid microbial decomposition of organic materials, these soils are a potential source of CO2 and are therefore likely to accelerate global warming.