Seminar on Role of Trees as Crowbars, Rhythmic Tap Dancers and Amplifiers in Soil Production

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The Department of Biological and Agricultural Engineering will present a seminar featuring Jill Marshall, assistant professor of geosciences, about the role of trees in soil production.

The seminar will take place at 10:45 a.m. Friday, Dec. 6, in room 219 of John A. White Jr. Engineering Hall.

The abstract:

Cracking the Critical Zone: The role of trees as crowbars, rhythmic tap dancers and amplifiers in soil production

While trees serve as rebar-like soil stabilizers over short time scales, over longer time scales tree-driven forces can damage, disrupt and detach bedrock in thin to no soil settings. In these settings, we presume that trees play a significant role in creating soil, with models centered on tree throw. However, little is known regarding how — or how often — trees damage rock, create fractures or expand fractures in fresh and weathered bedrock. This question is complicated by a paucity of available data and methods to measure forces at the bedrock-root interface.

Here I present preliminary data from a novel technique that measures root and wind-induced forces at the rock-root interface measured at the Boulder Creek, Eel River and Redlair Critical Zone Observatories. Combining force sensors at the tree-rock boundary with precipitation, solar radiation, wind, tree sway data, and acoustic emission sensors I have begun to quantify tree-driven soil-production mechanisms. Data suggests that trees damage and detach rock due to daily water uptake, rain, and wind events, while charismatic tree throw may matter less than belowground damage. The frequency, magnitude and style of wind-driven tree forces varies among species. This suggests that changes in water availability and forest structure, driven by variations in lithology and climate, may greatly influence soil production rates.