Prediction of Soil Formation as a Function of Age Using the Percolation Theory Approach
Prediction of Soil Formation as a Function of Age Using the Percolation Theory Approach
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DOI：
10.3389/fenvs.2018.00108
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发表时间：
2018-09-28
影响因子：
4.6
通讯作者：
Yu, Fang
中科院分区：
文献类型：
--
作者：
Egli, Markus;Hunt, Allen G.;Yu, Fang
最近的模拟和与现场结果的比较表明，土壤形成的化学风化，无论是从基岩或松散的材料，在很大程度上是有限的溶质运移。化学风化速率与溶质速度成正比。非反应性溶质运移描述的非高斯运输理论似乎与土壤形成率兼容。这种认识上的变化为预测土壤生产和深度跨越时间尺度的数量级开辟了新的可能性。渗透理论模拟土壤深度和生产的演变适用于新的和已公布的数据高山和地中海土壤。第一个目标是检验经验数据是否符合理论。其次，我们分析了理论和观测之间的差异，以找出理论是否是不完整的，如果需要修改现有的实验程序，哪些参数可能被错误地估计。并不是所有的输入参数所需的当前理论公式（粒径，侵蚀，并在过滤率）定期在现场收集，因此，理论必须解决如何找到这些数量从现有的气候和土壤数据库，这隐含地引入了一些不确定性。土壤质地的现有结果，通常在相关的现场报告，必须转换为结果的中值粒径，d（50），一个特定的理论输入参数。该模型相当好地跟踪了高山和地中海土壤的演变。然而，对于阿尔卑斯山的网站，我们发现，我们一贯高估土壤深度约45%。特别是在早期土壤形成过程中，化学风化更严重的限制反应动力学比溶质运移。矿物风化的动力学限制可以影响系统，直到1 kyr到最大10 kyr的土壤演变。此后，溶质运输似乎占主导地位。土壤深度演变的趋势和分散被很好地捕捉，特别是地中海土壤。我们假设，一些被忽视的过程，如生物扰动，树扔，和土地利用的变化，有助于当地的土壤重组，从而对模型的一些差异。尽管如此，该模型能够生成土壤深度，并证实随着年龄的增长，生产率下降。土壤在大约1亿年到100万年之前不会达到稳定状态。
Recent modeling and comparison with field results showed that soil formation by chemical weathering, either from bedrock or unconsolidated material, is limited largely by solute transport. Chemical weathering rates are proportional to solute velocities. Nonreactive solute transport described by non-Gaussian transport theory appears compatible with soil formation rates. This change in understanding opens new possibilities for predicting soil production and depth across orders of magnitude of time scales. Percolation theory for modeling the evolution of soil depth and production was applied to new and published data for alpine and Mediterranean soils. The first goal was to check whether the empirical data conform to the theory. Secondly we analyzed discrepancies between theory and observation to find out if the theory is incomplete, if modifications of existing experimental procedures are needed and what parameters might be estimated improperly. Not all input parameters required for current theoretical formulations (particle size, erosion, and in filtration rates) are collected routinely in the field; thus, theory must address how to find these quantities from existing climate and soil data repositories, which implicitly introduces some uncertainties. Existing results for soil texture, typically reported at relevant field sites, had to be transformed to results for a median particle size, d(50), a specific theoretical input parameter. The modeling tracked reasonably well the evolution of the alpine and Mediterranean soils. For the Alpine sites we found, however, that we consistently overestimated soil depths by similar to 45%. Particularly during early soil formation, chemical weathering is more severely limited by reaction kinetics than by solute transport. The kinetic limitation of mineral weathering can affect the system until 1 kyr to a maximum of 10 kyr of soil evolution. Thereafter, solute transport seems dominant. The trend and scatter of soil depth evolution is well captured, particularly for Mediterranean soils. We assume that some neglected processes, such as bioturbation, tree throw, and land use change contributed to local reorganization of the soil and thus to some differences to the model. Nonetheless, the model is able to generate soil depth and confirms decreasing production rates with age. A steady state for soils is not reached before about 100 kyr to 1 Myr.