Geologic and geomorphic controls on the occurrence of fens in the Oregon Cascades and implications for vulnerability and conservation

Wetlands
By: , and 

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Abstract

Montane fens are biologically diverse peat-forming wetlands that develop at points of groundwater discharge. To protect these ecosystems, it is critical to understand their locations on the landscape and the hydrogeologic systems that support them. The upper Deschutes Basin has a groundwater flow system that supports baseflow in many rivers, but little is known about the wetland types and groundwater dependence of the thousands of wetlands within the watershed. In 292 randomly selected wetlands, we quantified landscape metrics thought useful for discriminating montane fens from non-peat-forming wetlands. We inspected these wetlands and classified 67 of them as fens. Of the landscape metrics, only geology reliably differentiated fens from other types of wetlands. Nearly all fens develop in low-permeability glacial till found at approximately 1400–1800 m in elevation, and are concentrated in areas mantled by pumice deposits that originated primarily from the eruption of Mt. Mazama approximately 7700 years BP. Stratigraphic and hydrologic factors indicate the fens are supplied by perched aquifers in glacial till, instead of the deeper regional aquifer system. Their hydrogeologic setting makes the fens highly vulnerable to expected changes to recharge associated with climate change, but not to groundwater pumping from the regional aquifer.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Geologic and geomorphic controls on the occurrence of fens in the Oregon Cascades and implications for vulnerability and conservation
Series title Wetlands
DOI 10.1007/s13157-015-0667-x
Volume 35
Issue 4
Year Published 2015
Language English
Publisher Society of Wetland Scientists
Publisher location McClean, VA
Contributing office(s) Volcano Hazards Program, Oregon Water Science Center
Description 11 p.
First page 757
Last page 767
Country United States
State Oregon
Other Geospatial Cascade Range
Online Only (Y/N) N
Additional Online Files (Y/N) N