近日，加州理工学院Emily C. Geyman团队研究了岩石强度对土壤生成的贡献。相关论文于2025年11月12日发表在《自然》杂志上。

学界早有假说，并已观察到，在更薄的土壤之下，土壤的生成速率更快。然而，目前尚不清楚的是：土壤厚度是自上而下调控土壤生成的驱动变量，还是说，土壤厚度仅仅是响应由下至上控制的基岩风化变化的结果。回答这一问题之所以困难，是因为共同决定土壤厚度的土壤生成与侵蚀这两个过程之间的反馈，其对扰动的响应时间尺度长达数千至数百万年，这对科学家来说太长而无法直接观测。

研究组利用圣安德烈亚斯断层沿线一个瞬态山脉进行“空间替代时间”分析，其非凡的构造背景使得对抬升、土壤生成和侵蚀进行独立量化成为可能。该研究表明，在一次构造抬升脉冲之后，岩石到土壤的转化在上方土壤变薄之前就已加速，但与此同时，地形应力增加，岩石发生弱化。这一观测结果挑战了“土壤生成速率主要由土壤厚度控制”的长期假设，反而为一种自下而上、由岩石强度主导的土壤生成机制提供了证据。

附：英文原文

Title: The contribution of rock strength to soil production

Author: Geyman, Emily C., Paige, David A., Lamb, Michael P.

Issue&Volume: 2025-11-12

Abstract: It has long been proposed1, and then observed2,3, that faster rates of soil production occur beneath thinner soils. It remains uncertain, however, whether soil thickness is the driving variable regulating production from the top-down2,3,4,5,6, or whether soil thickness is simply responding to changes in bedrock weathering controlled from the bottom-up7,8. Answering this question is difficult because the feedbacks between soil production and soil erosion, the processes that jointly govern soil thickness2,9,10, respond to perturbations on timescales of thousands to millions of years11,12, timescales that are too long for scientists to observe directly. Here we leverage a space-for-time substitution at a transient mountain range along the San Andreas Fault13,14,15, where the remarkable tectonic setting allows for independent quantification of uplift, soil production and erosion. We show that, following a pulse of tectonic uplift, the conversion of rock to soil accelerates before the overlying soils thin, but at the same time that topographic stresses increase7 and the rock weakens16. This observation challenges the long-standing assumption that soil production rates are controlled predominantly by soil thickness1,2, and instead lends evidence for a bottom-up, rock strength control on soil production.

DOI: 10.1038/s41586-025-09751-z

Source: https://www.nature.com/articles/s41586-025-09751-z