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Virtually all soil chronosequence studies have equated the degree of mineral weathering with the soil age, which is equal to the time since the cessation of erosion or deposition. The primary minerals from the parent material, however, enter the soil as the weathering front propagates downward and are depleted via chemical weathering. The residence time of minerals is thus a function of both the rate of conversion of parent material to soil (i.e., soil production) and the minerals' susceptibility to chemical weathering reactions. We find that mineral residence times are significantly shorter than the soil age. By mathematically considering the interactions among soil production and chemical weathering, we demonstrate that traditional estimates of mineral-specific chemical weathering rates from soil chronosequences may diverge by several orders of magnitude from the actual weathering rates. [ABSTRACT FROM AUTHOR]

Burrowing organisms assist in shaping earth surfaces and are simultaneously affected by the environment they inhabit; however, a conceptual framework is not yet available to describe this feedback. We introduce a model that connects the population density of soil-burrowing animals to sediment transport via energy. The model, combined with avail- able data from California hillslopes where soil erosion is driven by pocket gophers (Thomomys bottae), suggests that a gopher annually expends ∼9 kJ of energy, or ∼1% of reported burrowing energy expenditure, in generating sediment transport. The model is used to evaluate the case that gophers prefer to populate thicker soils. The results suggest that this behavior may drastically dampen the spatial and temporal variations of soil thickness and gopher populations, implying that burrowing organisms may create landscapes distinct from those affected by abiotic processes. [ABSTRACT FROM AUTHOR]