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Geology and ecosystems - a framework for understanding contemporary ecologic processes through geologic settings and processes

Coordinated geologic, ecologic, and hydrologic studies are leading to a growing awareness of the geologic controls on the structure and function of contemporary ecosystems. A longstanding issue concerns how geologic substrates influence the amount and bioavailability of plant nutrients derived from mineral weathering, as well as hydrologic properties of soils. The mosaic of different rock and surficial geologic materials (and hence plant nutrients) is the product of many factors operating over space and time, including global tectonic setting, depositional environment, crustal deformation, volcanism, climate, and the redistribution of weathered material by geomorphic processes. Considering southeastern Utah drylands as an example, ecosystem processes can be partly understood through the depositional environments of varied sedimentary rocks and their weathered products. Rocks that formed as ancient sand dunes produce sandy soils with relatively low nutrient content. In contrast, ancient deposits formed in shallow ocean, river, or lake systems, like their modern analogs, have higher nutrient contents and produce modern soils with higher amounts of silt and clay. Through knowledge of ancient depositional environments, along with geologic and chemical mapping of their spatial distributions, it is possible to predict key biogeochemical and hydrologic properties broadly across this desert landscape. In this setting, as in many other ecosystems, atmospheric dust from distant sources adds nutrients to soils developed on local bedrock. Nutrients from dust and weathered rock are redistributed over hundreds of meters across upland slopes by geomorphic processes. Moreover, dust input rates have changed over the past 20,000 years with an overall increase in potential nutrients during the past 10,000 years. Because some plant roots extend deeply into soil, the Quaternary history of dust inputs is relevant to understanding processes of modern nutrient cycling.

Reynolds, R.L., Neff, J.C., and Reheis, M., 2004, Geology and ecosystems: A framework for understanding contemporary ecologic processes through geologic settings and processes: The Ecological Society of America 89th Annual Meeting Abstracts Volume, p. 425.
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