Soil thickness and residence time are regulated by a dynamic interplay between soil formation and lateral transport of soil particles and solutes. To unravel this interplay and infer patterns and rates of chemical weathering, soil physical and chemical properties can be used. Here, we present an integrated approach combining numerical modeling with field measurements to assess the impact of slope gradient on soil thickness and chemical weathering at a regional scale. We first perform a number of synthetic model runs simulating soil formation, weathering, erosion, and deposition, which show that soil thickness and weathering degree decline with increasing slope gradient. We then evaluate how those functional relationships compare to soil‐landscape data observed in the field. Soils are sampled at 100 midslope positions under varying slope gradient. The weathering degree is determined using three chemical weathering indices: ratio of iron oxides to total iron (Fe _d /Fe _t ), chemical index of alteration (CIA ), and total reserve in bases (TRB ). Finally, we calibrate the Be2D model to our field data to constrain soil residence times and chemical weathering rates. The modeled weathering rates decrease with increasing soil residence time and decreasing slope gradient. The application of the soil‐landscape evolution model in Southern Brazil shows that weathering rates can vary up to 2 orders of magnitude and depend on hillslope gradient. Notwithstanding model limitations and data uncertainties, we demonstrate the potential of an integrated approach, where field data and numerical modeling are integrated to unravel the timescale of soil weathering along transport over hillslopes.

中文翻译：

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坡度梯度控制巴西亚热带地区的土壤厚度和化学风化：通过结合现场数据和建模，了解区域土壤景观演变的速率和时标

土壤厚度和停留时间由土壤形成与土壤颗粒和溶质的横向运输之间的动态相互作用来调节。为了阐明这种相互作用并推断化学风化的模式和速率，可以使用土壤的物理和化学性质。在这里，我们提出了一种将数值模拟与现场测量相结合的综合方法，以评估坡度对区域范围内的土壤厚度和化学风化的影响。首先，我们进行了许多模拟模型的模拟，模拟了土壤的形成，风化，侵蚀和沉积，结果表明土壤厚度和风化度随坡度梯度的增加而下降。然后，我们评估这些功能关系如何与实地观测到的土壤-景观数据进行比较。在变化的坡度梯度下，在100个中坡位置对土壤进行采样。Fe _d / Fe _t），化学变化指数（CIA）和总碱储量（TRB）。最后，我们根据现场数据校准Be2D模型，以约束土壤停留时间和化学风化率。模拟的风化率随土壤停留时间的增加和坡度的减小而降低。巴西南部土壤-景观演化模型的应用表明，风化速率最多可变化2个数量级，并取决于坡度。尽管存在模型局限性和数据不确定性，我们还是展示了一种集成方法的潜力，该方法集成了现场数据和数值模型，以揭示沿山坡运输的土壤风化的时间尺度。