A Classification of the Riparian Vegetation of the South Platte and Republican River Basins, Colorado 1998 Final Report
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A Classification of the Riparian Vegetation of the South Platte and Republican River Basins, Colorado 1998 Final Report by Gwen Kittel, Erika VanWie, and Mary Damm Colorado Natural Heritage Program Colorado State University College of Natural Resources 254 General Services Building Ft. Collins, Colorado 80523 June 1998 i ACKNOWLEDGMENTS Financial support for this study was provided by a grant from the Environmental Protection Agency (EPA) Region VIII, through the Colorado Department of Natural Resources, with in-kind services from the Colorado Natural Heritage Program. Additional funding was provided by the Bureau of Land Management's Colorado Office, the Bureau of Reclamation, and the Denver Water Board. We’d like to thank Karen Hamilton and Dale Vodenahl of the EPA, Doug Robotham of the Colorado Department of Natural Resources, Brenda Mitchell of the Bureau of Land Management, Will Tully of the Bureau of Reclamation, and Bob Curfasi and Don Kennedy of the Denver Water Board for their continued support. We'd also like to acknowledge all Riparian Task Force members for their support and technical assistance, and for making this project a success. The Riparian Task Force is a cooperative group of 14 agencies joined by a Memorandum of Understanding and dedicated to the development of a state wide riparian classification for Colorado (see Appendix E). Several individuals contributed to the success of this project. Lea Spears assisted in field data collection on in the South Platte study area, and entered data into the computer. Amy McMullen assisted in field data collection and edited early versions of this manuscript. Many people assisted with the logistics of the field season. We also would like to thank Will Tully of the BOR for assistance with access to BOR lands on the South Platte River, and the DOW managers, Larry Budde for providing camping, access, maps, advice and local history about DOW lands along the South Platte River. We thank Jeff Losche and Maggie Marston of the Pawnee National Grassland for lending us maps, providing free camping, and providing access to Research Natural Areas on the Grassland. Jonathan Friedman and Mike Scott of the NBS provided land owner information, and stimulating discussions on riparian ecology. In addition, Betsy Neely and Patrick Bourgeron of The Nature Conservancy conceived the idea of a state- wide basin by basin riparian classification project, and developed the methodology. Many private landowners provided access to their lands, without their cooperation this project would not be a success. ii TABLE OF CONTENTS ACKNOWLEDGMENTS .............................................................................................................. ii SUMMARY.....................................................................................................................................1 INTRODUCTION ...........................................................................................................................2 STUDY AREA ................................................................................................................................5 METHODS ....................................................................................................................................22 Representative site selection..............................................................................................22 Classification Basis............................................................................................................26 Collection of vegetation and environmental data .............................................................27 Data Analysis and Classification Criteria..........................................................................28 Determination of Ecologically-Significant Sites ...............................................................31 RESULTS and DISCUSSION.......................................................................................................35 Lower (Plains) South Platte Watershed.............................................................................35 Upper (montane) South Platte Watershed .........................................................................37 KEY TO THE RIPARIAN PLANT ASSOCIATIONS OF THE SOUTH PLATTE RIVER BASIN, COLORADO .......................................................................................................48 II.A.4.e OPEN TREE CANOPY, EVERGREEN, TEMPERATE SEASONALLY FLOODED/SATURATED ................................................................................................60 Abies lasiocarpa Alliance..................................................................................................60 Subalpine fir-Engelmann spruce/thinleaf alder (Abies lasiocarpa-Picea engelmannii /Alnus incana ssp. tenuifolia) Plant Association...................60 Subalpine fir-Engelmann spruce/aquatic sedge (Abies lasiocarpa-Picea engelmannii/Carex aquatilis) Plant Association .......................................66 Sub-alpine fir-Engelmann spruce/Drummond willow (Abies lasiocarpa-Picea engelmannii/Salix drummondiana) Plant Association...............................70 Subalpine fir-Engelmann spruce/mountain bluebells (Abies lasiocarpa-Picea engelmannii/Mertensia ciliata) Plant Association.....................................75 Picea pungens Alliance .....................................................................................................80 Colorado blue spruce/thinleaf alder (Picea pungens/Alnus incana ssp. tenuifolia) Plant Association ......................................................................................80 Colorado blue spruce/red-osier dogwood (Picea pungens/Cornus sericea) Plant Association.................................................................................................84 Colorado blue spruce/river birch (Picea pungens/Betula occidentalis) Plant Association.................................................................................................87 Pinus ponderosa Alliance..................................................................................................90 Ponderosa pine/thin-leaf alder (Pinus ponderosa/Alnus incana) Plant iii Association.............................................................................................................90 Pseudotsuga menziesii Alliance.........................................................................................93 Douglas-fir/river birch (Pseudotsuga menziesii/Betula occidentalis) Plant Association.................................................................................................93 II.B.2.c. OPEN CANOPY, COLD-DECIDUOUS, SEASONALLY FLOODED/SATURATED, TREE DOMINATED ASSOCIATIONS...........................................................................96 Populus x acuminata Alliance ...........................................................................................96 Unclassified Populus x acuminata Stands.............................................................96 Populus angustifolia Alliance............................................................................................96 Unclassified Populus angustifolia Stands: ............................................................96 Narrowleaf cottonwood/thinleaf alder (Populus angustifolia/Alnus incana) Plant Association.................................................................................................98 Narrowleaf cottonwood/river birch (Populus angustifolia/Betula occidentalis) Plant Association .....................................................................................102 Narrowleaf cottonwood/common choke cherry (Populus angustifolia/Prunus virginiana) Plant Association ..................................................................106 Narrowleaf cottonwood/coyote willow (Populus angustifolia/Salix exigua) Plant Association...............................................................................................109 Narrowleaf cottonwood/bluestem willow (Populus angustifolia/Salix irrorata) Plant Association .....................................................................................114 Populus balsamifera Alliance..........................................................................................118 Balsam poplar (Populus balsamifera) Plant Association ....................................118 Populus deltoides ssp. monilifera Alliance......................................................................122 Plains cottonwood/smooth brome (Populus deltoides spp. monilifera/Bromus inermis) Plant Association.......................................................................122 Plains cottonwood/woolly sedge (Populus deltoides ssp. monilifera/Carex lanuginosa) Plant Association .................................................................125 Plains cottonwood/switch grass (Populus deltoides spp. monilifera/Panicum virgatum) Plant Association.....................................................................129 Plains cottonwood/choke cherry (Populus deltoides spp. monilifera/Prunus virginiana) Plant Association .................................................................133 Plains cottonwood/western snowberry (Populus deltoides ssp. monilifera/Symphoricarpos occidentalis) Plant Association...................137 Plains cottonwood-(peach-leaved willow)/coyote willow (Populus deltoides ssp. monilifera-(Salix amygdaloides)/Salix exigua) Plant Association ..........142 Plains cottonwood-(Peach-leaved willow)/Prairie slough