277-9 Soil Memory of Expanding and Contracting Desert Boundaries

Session: Critical Zone Science: Intersection of Processes Linked to Geomorphology, Ecology, Fire and Climate

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The soil memory concept dates back to a period of Russian pedology in the late 1800s. It has been revived as a method for extracting information from soil profiles about natural cycles of climate change compared to the current rate of climate change. “Palimpsest-wise memory,” for example, when supplemented with an analysis of punctuated sedimentation or “book-wise memory”, can be particularly useful when applied to the boundary of deserts bordering semiarid regions. The Chihuahuan Desert of North America, for example, is dominated by C3 shrubs and high erosion rates in contrast to the surrounding grassland dominated by C4 grass species and low erosion. Palimpsest-wise and book-wise memory reveal multiple periods of alternating desert expansion and contraction based on alternating periods of landscape stability (soil formation) and instability (erosion) at a point on the oscillating boundary. These alternating periods range from overgrazing within the last 180 years to the major glacial/interglacial cycles within the last 800,000 years. Carbon isotopic analysis in combination with soil memory indicates an increase in C3 desert shrubs during the recent overgrazing high-erosion period and during the mid-Holocene aridity period, but otherwise indicates a system dominated by C4 grasses. In addition to soil memory acquisition, soil memory loss is an equally important concept. In the Chihuahuan Desert, memory loss occurs by the microbial oxidation of organic matter during increased aridity, by erosion that truncates soil horizons during dry periods, and by the dissolution of carbonate during wetter periods.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10801

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