«Abstract Weixelman, D. A., B. Hill, D.J. Cooper, E.L. Berlow, J. H. Viers, S.E. Purdy, A.G. Merrill, and S.E. Gross. 2011. A Field Key to Meadow ...»
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iii Abstract Weixelman, D. A., B. Hill, D.J. Cooper, E.L. Berlow, J. H. Viers, S.E. Purdy, A.G. Merrill, and S.E.
Gross. 2011. A Field Key to Meadow Hydrogeomorphic Types for the Sierra Nevada and Southern Cascade Ranges in California. Gen. Tech. Rep. R5-TP-034. Vallejo, CA. U.S. Department of Agriculture, Forest Service, Pacific Southwest Region, 34 pp.
The purpose of this document is to provide a dichotomous key to meadow hydrogeomorphic types for the Sierra Nevada and Southern Cascades of California. This classification and field key uses both hydrology and geomorphology to identify fourteen meadow types. Strengths of the classification include its ability to clarify the relationship between hydrology and geomorphology and meadow function.
Meadows are extremely valuable to society and to the natural systems that support society.
Meadows reduce peak water flow after storms and during runoff, recharge groundwater supplies as they release water into the ground, protect streambanks and shorelines, filter sediments, provide habitat for a wide variety of wildlife, and serve important recreational and cultural functions. Because of these multiple purposes, land managers face a special challenge to maintain, restore, and manage meadows. To aid in management, a classification of meadows is needed that uses both hydrology and geomorphology in identifying types and functioning of meadows. Potential uses for this classification include stratifying meadows for condition assessment and as an aid in mapping or delineating meadow features on the landscape.
Keywords: meadow, hydrology, hydrogeomorphology, geomorphology, wetland, Sierra Nevada The Authors Dave A. Weixelman (email@example.com), Regional Rangeland Ecologist, Pacific Southwest Region, USDA Forest Service, Vallejo, CA.
Barry Hill, Regional Hydrologist, Pacific Southwest Region, USDA Forest Service, Vallejo, CA.
David J. Cooper, Senior Research Scientist, Department of Forest, Rangeland and Watershed Stewardship, Colorado State University, Fort Collins, Colorado.
Eric L. Berlow, Ecologist, Western Ecological Research Center, US Geological Survey, Yosemite Field Station, Yosemite, CA.
Joshua H. Viers, Associate Research Scientist, Department of Environmental Science and Policy, and Associate Director, Center for Watershed Sciences, UC Davis Sabra E. Purdy, Research Scientist, Center for Watershed Sciences, UC Davis, Davis, CA Amy G. Merrill, Senior Riparian Ecologist, Stillwater Sciences, Berkeley, CA Shana E. Gross, Ecologist, US Forest Service, Lake Tahoe Management Basin, South Lake Tahoe, CA iv
ACKNOWLEDGEMENTSThe authors wish to thank Anne Yost, Regional Range Program Manager for the Pacific Southwest Region of the USDA Forest Service in Vallejo, CA, for general support and funding for this document.
The authors wish to thank the Grants Pass Water Laboratory, Grants Pass, OR, for permission to modify and use an illustration from their website. All photos in this document were taken by Dave Weixelman.
Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not
imply endorsement by the U.S. Government. The authors also wish to thank the following reviewers:
Todd Keeler-Wolf, Chief Vegetation Ecologist, California Department of Fish and Game Sherman Swanson, Department of Natural Resources and Environmental Science, University of NevadaReno Jeff Tenpas, Pacific Southwest Region Watershed Improvement Program Mgr., US Forest Service Sylvia Haultain, Ecologist, National Park Service, Sequoia and Kings Canyon National Parks Leigh Sevy, Rangeland Conservationist, US Forest Service Kathleen Sevy, Rangeland Conservationist, US Forest Service Matthew Freitas, Department of Plant Sciences, UC Davis Dawn Coultrap, Rangeland Conservationist, US Forest Service Kendra Sikes, Vegetation Ecologist, California Native Plant Society Gregg Riegel, Ecologist, US Forest Service Gail Bakker, Hydrologist, US Forest Service John Lorenzana, retired range conservationist, US Forest Service Erin Lutrick, Hydrologist, US Forest Service Nick Jensen, Botanist, UC Davis Peggy Moore, Plant Ecologist, US Geological Survey, Western Ecological Research Center Tom Kimball, Research Manager, US Geological Survey, Western Ecological Research Center v
TABLE OF CONTENTS
inflow, and throughflow describe whether a meadow is a source, sink, or pass-through system respectively. Meadows perform different functions, depending on the gradient of the groundwater table and the topography of the land surface. The relationship of the groundwater table and the land surface dictates which function - groundwater recharge or discharge - a meadow performs. Groundwater recharge adds water to the groundwater system whereas groundwater discharge takes water from the groundwater system. Meadows may include areas that are wetland, but depending upon the wetland definition being used, not all areas within meadows will necessarily meet that definition's criteria.
Therefore, when trying to determine if a meadow or part of a meadow is a wetland, the user must first decide on the wetland definition to be used, and then determine if the meadow or part of the meadow meets these criteria.
Meadows that develop on mineral soils can be separated from meadows that occur on organic soils (peatlands) where an accumulation of peat creates the substrate, influences groundwater conditions, selects for specialized vegetation, and modifies surface morphology of the wetland.
Sources of water in meadows can be precipitation, groundwater, or surface flow, or a combination of these sources. Meadows that receive little groundwater inflow or surface water inputs are often precipitation and/or snowmelt dominated and become dry during summer.
Sometimes these precipitation and/or snowmelt dominated meadows are located in depressions with an impervious layer which retains precipitation and prevents the discharge of groundwater.
Precipitation dominated meadows can also occur on a number of different landforms and typically results in a dry meadow type.
Meadows also form in landscape positions where water actively discharges in the form of springs or seeps, particularly on hillslopes, at the base of hills and at the base of alluvial fans. These groundwater dominated meadows may also receive overland flow but they have a steady supply of water from groundwater. Most meadows in low points and in areas of valley fill (alluvium) are dominated by overland surface flow or a combination of surface and groundwater flow. Meadows that occur on alluvium or in valley bottoms or swales that lack a stream channel are often fed by subsurface groundwater without significant surface water inputs. Riparian meadows are found on floodplains and terraces associated with stream channels. Riparian meadow systems are fed both by surface water from flood events and by subsurface groundwater. The amount of lateral groundwater inflow from the hillslopes as compared to basal-groundwater inflow is often a key determinant of the type and pattern of meadow vegetation (Loheide et al. 2009). Further, groundwater inflow from the hillslope, to the hillslope/riparian interface, and ultimately to the riparian zone is strongly affected by bedrock permeability in granitic regions (Katsuyama and Ohte 2005).
Riparian meadows can be further broken down based on slope steepness as low, middle, or high gradient.
Stream gradient is correlated with riparian vegetation (Quistberg and Stringham 2009), flow velocity, substrate material, floodplain development, channel morphology and stream habitat types (pools, riffles, runs, etc.)(Rosgen 1994, Montgomery and Buffington 1997). Lacustrine fringe meadows are located along lake shores where the water elevation of the lake influences the water table of the adjacent meadow.
These riparian (associated with a stream or river), and lacustrine (associated with a lake) meadows come in contact with, store, or release large quantities of water.
CLASSIFICATION OF MEADOWS
Efforts to classify meadows in the Sierra Nevada have used plant communities (Sumner 1941, Bennett 1965, Pemble 1970, Chabot and Billings 1972, Taylor 1976, Ratliff 1979 and 1982, Benedict and Major 1981, Jackson and Bliss 1982, Benedict 1983, Taylor 1984, Halpern 1985, Manning and Padgett 1995, Cheng 2004, Potter 2006, Barbour et al. 2007, Sawyer et al. 2009), general topography (Harkin and Schultz 1967, Benedict and Major 1982, Ratliff 1986), elevational range (Sharsmith 1959), site potential (Weixelman et al. 1999, Rundel et al. 2009), stratigraphy from the Holocene record (Wood 1975), moisture gradient as wet, moist, and dry (Klikoff 1965), and peatland types (Cooper and Wolf 2005, Weixelman and Cooper 2009, Sikes et al. 2010).
Figure 1. The geographic extent (green shading) covered by the classification for the Sierra Nevada and Southern Cascade ranges in California.
This classification and field key uses both hydrology and geomorphology to identify fourteen meadow hydrogeomorphic types and takes many concepts from Brinson (1993). The geographic extent where this classification has been used is shown in Figure 1. Plant nomenclature in this document follows Hickman (1993). Strengths of the classification include its ability to clarify the relationship between hydrology and geomorphology and meadow function. Landform features, water sources, and water flow directions are an integral part of this hydrogeomorphic classification. Patterns of landform occurrence, the source and amount of water in a meadow, and the path the water takes through the meadow have reoccurring characteristics that help identify and stratify meadows for management interpretations. The individual types in this classification, together with plant species information, would allow for a determination of ecological function based on the relationship between meadow type, ecological functioning, and plant functional groups.
USING THE KEY
Meadows, as defined above, may contain one or more hydrogeomorphic types depending on landscape position, water sources, and flow direction. The dichotomous key is designed to help the user identify these individual hydrogeomorphic types. In some cases, the meadow may be composed of only one hydrogeomorphic type, in other cases there will be two or more hydrogeomorphic types present.
To use this key, start by locating a representative section of the meadow. The representative section should generally be consistent in soil moisture, and occur on a single dominant landform. Once this representative section of the meadow area has been located, the dichotomous key can be used to determine the hydrogeomorphic type. Definitions of terms used in the key can be found in Appendix A.
If the meadow includes sites that are distinctly different in landscape position and/or soil moisture characteristics, those sites may need to be keyed separately. In that case there may be more than one hydrogeomorphic type present in the meadow.
An example of a meadow is shown in Figure 2. In this figure, there is a stream channel running the length of the meadow and the predominant landform is a floodplain adjacent to the stream channel.
Representative sampling locations are marked by an “X.” At these sampling locations, the dichotomous key was used to identify a hydrogeomorphic type. The dominant type was the riparian low gradient.
Also present were two other hydrogeomorphic types within the meadow, a discharge slope type located on a toeslope and a dry type located on a terrace at the outer edge of the meadow. This example illustrates the concept of a meadow and component hydrogeomorphic types which make up the meadow.
Figure 2. Illustration of a meadow and the component hydrogeomorphic types which make up the meadow.
Also shown are the representative locations (marked by X’s) where the dichotomous key was used in the field to identify the component hydrogeomorphic types.
FIELD KEY TO MEADOW HYDROGEOMORPHIC TYPESNote: More than one hydrogeomorphic type may occur in a meadow area.
4a. Occurs in a topographic depression with a closed elevation contour that allows accumulation of surface water. If standing water is present, the water depth is less than (or is judged to be less than) 2 meters (6.6 feet) deep. The depression may have any combination of inlets and outlets or lack them completely.
Water either does not flow through the depressional meadow or the flow is essentially imperceptible.
Includes artificially created depressions due to impoundments, causeways, and roads. May or may not be surrounded by upland vegetation 5