Depth-dependent soil mixing persists across climate zones
Depth-dependent soil mixing persists across climate zones
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DOI：
10.1073/pnas.1914140117
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发表时间：
2020-04-21
影响因子：
11.1
通讯作者：
Mahan, Shannon A.
中科院分区：
文献类型：
--
作者：
Gray, Harrison J.;Keen-Zebert, Amanda;Mahan, Shannon A.
长时间（>10（2）年）的土壤混合增强了支持土壤生态的养分通量，有助于沉积物和污染物质的分散，并通过地球上最大的陆地碳库调节碳通量。尽管其基础的重要性，我们缺乏强大的理解的速度和模式的土壤混合，主要是由于缺乏长期的时间尺度数据。在这里，我们表明，发光，用于地质测年的矿物的光敏感特性，可以被用来作为一个长时间尺度的土壤中的沉积物示踪剂，以揭示土壤混合的结构。我们开发了一个概率模型的运输和混合的示踪剂颗粒和相关的发光在土壤中，并与全球汇编的发光与深度在不同的位置进行比较。模型数据的比较表明，土壤混合率随土壤深度而变化，这种深度依赖性在气候和生态区持续存在。深度依赖性与混合强度随深度线性或指数下降的模型一致，尽管我们的数据在这些情况下没有解决。我们的研究结果支持了长期怀疑的想法，即深度依赖性混合是一个空间和时间上持久的土壤特征。气候控制土壤混合的模式和强度与深度的证据仍然难以捉摸，需要进一步研究土壤混合过程。
Soil mixing over long (>10(2) y) timescales enhances nutrient fluxes that support soil ecology, contributes to dispersion of sediment and contaminated material, and modulates fluxes of carbon through Earth's largest terrestrial carbon reservoir. Despite its foundational importance, we lack robust understanding of the rates and patterns of soil mixing, largely due to a lack of long-timescale data. Here we demonstrate that luminescence, a light-sensitive property of minerals used for geologic dating, can be used as a long-timescale sediment tracer in soils to reveal the structure of soil mixing. We develop a probabilistic model of transport and mixing of tracer particles and associated luminescence in soils and compare with a global compilation of luminescence versus depth in various locations. The model-data comparison reveals that soil mixing rate varies over the soil depth, with this depth dependency persisting across climate and ecological zones. The depth dependency is consistent with a model in which mixing intensity decreases linearly or exponentially with depth, although our data do not resolve between these cases. Our findings support the long-suspected idea that depth-dependent mixing is a spatially and temporally persistent feature of soils. Evidence for a climate control on the patterns and intensities of soil mixing with depth remains elusive and requires the further study of soil mixing processes.