The goal of Grand Canyon Monitoring and Research Center’s (part of the Southwest Biological Science Center) riparian vegetation monitoring program is to assess changes and trends in plant species composition and cover and relate those changes to Glen Canyon Dam operations, river hydrology, climate, and geomorphology. Monitoring is done by annual field-data collection on plant cover and diversity in concert with semi-decadal remote sensing to distinguish the effects of dam operations from other environmental and human-caused changes to riparian vegetation. Between 2012 and 2017, the GCMRC vegetation program sampled 392 sites (43 of them repeated every year and only counted once in that total), and has sampled approximately 16,524 unique 1m2 (about 3.3’ x 3.3’) plots. Remote sensing analyses are synoptic image classification and change detection assessments of the entire 475 km (295 miles) river corridor between Glen Canyon Dam and Lake Mead or shorter reaches within the corridor. These robust data sets can tell the story of a changing riparian landscape.
General Methods:
Each year, the Grand Canyon Monitoring and Research Center (GCMRC) terrestrial vegetation program monitors vegetation between the Glen Canyon Dam and Spencer Canyon at river mile 245—the location that the hydrology and botanical communities begin to be impacted by the Hoover Dam and Lake Mead’s sediment deposition. Each year, the vegetation program monitors up to 90 randomly selected sites that are divided between three predominant geomorphic features—sandbars, debris fans, and channel margins—as well as 43 sites that are at fixed (repeated) sandbars. Sites are stratified at three nested scales—river segment, geomorphic feature, and hydrologic zone. The samples encompass differences in vegetation due to geography, geomorphology, and the frequency of inundation.At each monitoring site, nine 1 meter-squared (1m2 or 3.3’ x 3.3’) vegetation plots are sampled along three transects that are oriented perpendicular to the river, totaling 27 one meter square plots per site. The vegetation plots are arranged on each transect to cover the three hydrologic zones and captures the vegetation variability of the site.
The GCMRC vegetation program collaborates with the National Park Service (NPS) Northern Colorado Plateau Inventorying and Monitoring Network’s big-river program that monitors large rivers upstream of the Glen Canyon Dam—the Upper Colorado, Green, and Yampa Rivers. These collaborations link processes occurring in the rivers upstream to the Colorado River in Glen and Grand Canyons. For information on the NPS Northern Colorado Plateau Inventorying and Monitoring Network, please visit their website: https://science.nature.nps.gov/im/units/ncpn/.
For more detailed sampling methods, reference:
Palmquist, E.C., Ralston, B.E., Sarr, D.A., and Johnson, T.C., 2018, Monitoring riparian-vegetation composition and cover along the Colorado River downstream of Glen Canyon Dam, Arizona: U.S. Geological Survey Techniques and Methods, book 2, chap. A14, 65 p., https://doi.org/10.3133/tm2A14.
Important Results:
Floristic Community Changes in Grand Canyon (published in Palmquist et al. (2018)):
Floristic communities change and species richness declines between the Glen Canyon Dam and river mile 245. Riparian vegetation sampling along the Colorado River through Grand Canyon by GCMRC’s vegetation program identified how richness and functional diversity vary, and described the implications of our results for river management (Palmquist et al. 2018, see "Publications" tab near top of this page). Cluster analysis identified three divergent floristic groups that are distributed longitudinally along the river. These groups were distributed along gradients of elevation, temperature and seasonal precipitation, but were not associated with annual precipitation or local-scale factors. Species richness and functional diversity decreased as a function of distance downstream showing that changing landscape-scale factors result in changes to ecosystem characteristics. Species composition and distribution remain closely linked to seasonal precipitation and temperature. River segments were delineated by floristic groups, and are bound by three large tributaries—the Paria River at river mile 0, the Little Colorado River at river mile 60, and National Canyon at river mile 160. The table below illustrates the floristic groups by river segment.
These patterns in floristic composition in a semiarid system inform management and provide insight into potential future changes as a result of shifts in climate and changes in flow management.
Below are other science projects associated with this project.
Overview of Riparian Vegetation in Grand Canyon
Riparian Remote Sensing in the Colorado River and Grand Canyon Region
Riparian vegetation data downstream of Glen Canyon Dam in Glen Canyon National Recreation Area and Grand Canyon National Park, AZ from 2014 to 2019
Below are publications associated with this project.
Associations between riparian plant morphological guilds and fluvial sediment dynamics along the regulated Colorado River in Grand Canyon
A comparison of riparian vegetation sampling methods along a large, regulated river
Hydrological regime and climate interactively shape riparian vegetation composition along the Colorado River, Grand Canyon
Monitoring riparian-vegetation composition and cover along the Colorado River downstream of Glen Canyon Dam, Arizona
Landscape-scale processes influence riparian plant composition along a regulated river
Case studies of riparian and watershed restoration in the southwestern United States—Principles, challenges, and successes
Variation in species-level plant functional traits over wetland indicator status categories
Changes in community-level riparian plant traits over inundation gradients, Colorado River, Grand Canyon
Functional traits and ecological affinities of riparian plants along the Colorado River in Grand Canyon
Riparian vegetation response to the March 2008 short-duration, High-Flow Experiment— Implications of timing and frequency of flood disturbance on nonnative plant establishment along the Colorado River below Glen Canyon Dam
A Vegetation Database for the Colorado River Ecosystem from Glen Canyon Dam to the Western Boundary of Grand Canyon National Park, Arizona
Do beavers promote the invasion of non-native Tamarix in the Grand Canyon riparian zone
Below are partners associated with this project.
- Overview
The goal of Grand Canyon Monitoring and Research Center’s (part of the Southwest Biological Science Center) riparian vegetation monitoring program is to assess changes and trends in plant species composition and cover and relate those changes to Glen Canyon Dam operations, river hydrology, climate, and geomorphology. Monitoring is done by annual field-data collection on plant cover and diversity in concert with semi-decadal remote sensing to distinguish the effects of dam operations from other environmental and human-caused changes to riparian vegetation. Between 2012 and 2017, the GCMRC vegetation program sampled 392 sites (43 of them repeated every year and only counted once in that total), and has sampled approximately 16,524 unique 1m2 (about 3.3’ x 3.3’) plots. Remote sensing analyses are synoptic image classification and change detection assessments of the entire 475 km (295 miles) river corridor between Glen Canyon Dam and Lake Mead or shorter reaches within the corridor. These robust data sets can tell the story of a changing riparian landscape.
Image depicting the vegetation program’s field methods and data collection. These techniques can show patterns, trends, and changes throughout the Colorado River corridor downstream of the Glen Canyon Dam. Click image to enlarge it. (Credit: Sarah Sterner, USGS. Public domain.) General Methods:
Monitoring riparian vegetation along the Colorado River downstream of Glen Canyon Dam. (Credit: Amy Washuta, NPS/USGS. Public domain.) Each year, the Grand Canyon Monitoring and Research Center (GCMRC) terrestrial vegetation program monitors vegetation between the Glen Canyon Dam and Spencer Canyon at river mile 245—the location that the hydrology and botanical communities begin to be impacted by the Hoover Dam and Lake Mead’s sediment deposition. Each year, the vegetation program monitors up to 90 randomly selected sites that are divided between three predominant geomorphic features—sandbars, debris fans, and channel margins—as well as 43 sites that are at fixed (repeated) sandbars. Sites are stratified at three nested scales—river segment, geomorphic feature, and hydrologic zone. The samples encompass differences in vegetation due to geography, geomorphology, and the frequency of inundation.At each monitoring site, nine 1 meter-squared (1m2 or 3.3’ x 3.3’) vegetation plots are sampled along three transects that are oriented perpendicular to the river, totaling 27 one meter square plots per site. The vegetation plots are arranged on each transect to cover the three hydrologic zones and captures the vegetation variability of the site.
The GCMRC vegetation program collaborates with the National Park Service (NPS) Northern Colorado Plateau Inventorying and Monitoring Network’s big-river program that monitors large rivers upstream of the Glen Canyon Dam—the Upper Colorado, Green, and Yampa Rivers. These collaborations link processes occurring in the rivers upstream to the Colorado River in Glen and Grand Canyons. For information on the NPS Northern Colorado Plateau Inventorying and Monitoring Network, please visit their website: https://science.nature.nps.gov/im/units/ncpn/.
For more detailed sampling methods, reference:
Palmquist, E.C., Ralston, B.E., Sarr, D.A., and Johnson, T.C., 2018, Monitoring riparian-vegetation composition and cover along the Colorado River downstream of Glen Canyon Dam, Arizona: U.S. Geological Survey Techniques and Methods, book 2, chap. A14, 65 p., https://doi.org/10.3133/tm2A14.
Important Results:
Floristic Community Changes in Grand Canyon (published in Palmquist et al. (2018)):
Table of common species found in the riparian area along Colorado River downstream of Glen Canyon Dam. See paragraph above for more infomation. Click on table to enlarge. (Credit: Emily Palmquist, USGS. Public domain.) Floristic communities change and species richness declines between the Glen Canyon Dam and river mile 245. Riparian vegetation sampling along the Colorado River through Grand Canyon by GCMRC’s vegetation program identified how richness and functional diversity vary, and described the implications of our results for river management (Palmquist et al. 2018, see "Publications" tab near top of this page). Cluster analysis identified three divergent floristic groups that are distributed longitudinally along the river. These groups were distributed along gradients of elevation, temperature and seasonal precipitation, but were not associated with annual precipitation or local-scale factors. Species richness and functional diversity decreased as a function of distance downstream showing that changing landscape-scale factors result in changes to ecosystem characteristics. Species composition and distribution remain closely linked to seasonal precipitation and temperature. River segments were delineated by floristic groups, and are bound by three large tributaries—the Paria River at river mile 0, the Little Colorado River at river mile 60, and National Canyon at river mile 160. The table below illustrates the floristic groups by river segment.
These patterns in floristic composition in a semiarid system inform management and provide insight into potential future changes as a result of shifts in climate and changes in flow management.
Graph of three common species along the Colorado River downstream of Glen Canyon Dam illustrating species turnover. Baccharis emoryi, Baccharis salicifolia, and Baccharis sarothroides relative cover distribution between river mile 0 to river mile 245. Vertical dotted lines on each graph delineate Marble Canyon, Eastern Grand Canyon, and Western Grand Canyon. Graph modified from Palmquist et al. (2018). Photos of each species are located to the right of their distribution. Click on graph to enlarge. (Credit: Emily Palmquist & Sarah Sterner, USGS. Public domain.) - Science
Below are other science projects associated with this project.
Overview of Riparian Vegetation in Grand Canyon
Riparian areas are conspicuous belts of dense, green vegetation along streams and rivers, and can be considered “ribbons of life”. Despite covering less than 2 percent of the land area in the southwestern U.S., riparian areas tend to have high species diversity and population density, making them valuable to managers, scientists, and the public. These unique ecosystems act as a link between dry...Riparian Remote Sensing in the Colorado River and Grand Canyon Region
Riparian vegetation has increased dramatically along the Colorado River downstream of Glen Canyon Dam since the closure of the dam in 1963. The spatial patterns and temporal rates of vegetation increase occur due to changes in river hydrology, dam operations, and climate. The increase in vegetation, particularly onto otherwise bare sandbars, has impacted recreational, geomorphological, biological... - Data
Riparian vegetation data downstream of Glen Canyon Dam in Glen Canyon National Recreation Area and Grand Canyon National Park, AZ from 2014 to 2019
These data were collected by the Grand Canyon Monitoring and Research Center (GCMRC) to support riparian vegetation monitoring along the Colorado River between Glen Canyon Dam and the full pool level of Lake Mead. The objectives of the GCMRC riparian vegetation monitoring program are to annually measure and summarize the status (composition and cover) of native and non-native vascular plant specie - Publications
Below are publications associated with this project.
Associations between riparian plant morphological guilds and fluvial sediment dynamics along the regulated Colorado River in Grand Canyon
Effects of riparian vegetation on fluvial sediment dynamics depend on morphological traits of the constituent species. Determining the effects of different morphological guilds on sedimentation rates, as influenced by multiple aspects of dam operations, can help identify viable strategies for streamflow and vegetation management to achieve riparian resource goals. Plants of increasing size and braAuthorsBradley J. Butterfield, Paul Grams, Laura E. Durning, Joseph Hazel, Emily C. Palmquist, Barbara Ralston, Joel B. SankeyA comparison of riparian vegetation sampling methods along a large, regulated river
Monitoring riparian vegetation cover and species richness is an important component of assessing change and understanding ecosystem processes. Vegetation sampling methods determined to be the best option in other ecosystems (e.g., desert grasslands and arctic tundra) may not be the best option in multilayered, species rich, heterogeneous riparian vegetation. This study examines the strengths and wAuthorsEmily C. Palmquist, Sarah Sterner, Barbara RalstonHydrological regime and climate interactively shape riparian vegetation composition along the Colorado River, Grand Canyon
QuestionHow closely do riparian plant communities track hydrological and climatic variation in space, and how do interactions among hydrological and climatic filters influence success of flow management strategies?LocationGrand Canyon, Arizona, USA.MethodsMulti‐year vegetation surveys were conducted across three hydrological zones – active channel, active floodplain and inactive floodplain – withiAuthorsBradley J. Butterfield, Emily C. Palmquist, Barbara RalstonMonitoring riparian-vegetation composition and cover along the Colorado River downstream of Glen Canyon Dam, Arizona
Vegetation in the riparian zone (the area immediately adjacent to streams, such as stream banks) along the Colorado River downstream of Glen Canyon Dam, Arizona, supports many ecosystem and societal functions. In both Glen Canyon and Grand Canyon, this ecosystem has changed over time in response to flow alterations, invasive species, and recreational use. Riparian-vegetation cover and compositionAuthorsEmily C. Palmquist, Barbara E. Ralston, Daniel A. Sarr, Taylor C. JohnsonLandscape-scale processes influence riparian plant composition along a regulated river
Hierarchical frameworks are useful constructs when exploring landscape- and local-scale factors affecting patterns of vegetation in riparian areas. In drylands, which have steep environmental gradients and high habitat heterogeneity, landscape-scale variables, such as climate, can change rapidly along a river's course, affecting the relative influence of environmental variables at different scalesAuthorsEmily C. Palmquist, Barbara Ralston, David M. Merritt, Patrick B. ShafrothCase studies of riparian and watershed restoration in the southwestern United States—Principles, challenges, and successes
Globally, rivers and streams are highly altered by impoundments, diversions, and stream channelization associated with agricultural and water delivery needs. Climate change imposes additional challenges by further reducing discharge, introducing variability in seasonal precipitation patterns, and increasing temperatures. Collectively, these changes in a river or stream’s annual hydrology affects sAuthorsBarbara E. Ralston, Daniel A. SarrVariation in species-level plant functional traits over wetland indicator status categories
Wetland indicator status (WIS) describes the habitat affinity of plant species and is used in wetland delineations and resource inventories. Understanding how species-level functional traits vary across WIS categories may improve designations, elucidate mechanisms of adaptation, and explain habitat optima and niche. We investigated differences in species-level traits of riparian flora across WIS cAuthorsMiles E. McCoy-Sulentic, Thomas E. Kolb, David M. Merritt, Emily C. Palmquist, Barbara E. Ralston, Daniel A. SarrChanges in community-level riparian plant traits over inundation gradients, Colorado River, Grand Canyon
Comparisons of community-level functional traits across environmental gradients have potential for identifying links among plant characteristics, adaptations to stress and disturbance, and community assembly. We investigated community-level variation in specific leaf area (SLA), plant mature height, seed mass, stem specific gravity (SSG), relative cover of C4 species, and total plant cover over hyAuthorsMiles McCoy-Sulentic, Thomas Kolb, David Merritt, Emily C. Palmquist, Barbara E. Ralston, Daniel Sarr, Patrick B. ShafrothFunctional traits and ecological affinities of riparian plants along the Colorado River in Grand Canyon
Trait-based approaches to vegetation analyses are becoming more prevalent in studies of riparian vegetation dynamics, including responses to flow regulation, groundwater pumping, and climate change. These analyses require species trait data compiled from the literature and floras or original field measurements. Gathering such data makes trait-based research time intensive at best and impracticableAuthorsEmily C. Palmquist, Barbara E. Ralston, Sarr. Daniel, David Merritt, Patrick B Shafroth, Julian ScottRiparian vegetation response to the March 2008 short-duration, High-Flow Experiment— Implications of timing and frequency of flood disturbance on nonnative plant establishment along the Colorado River below Glen Canyon Dam
Riparian plant communities exhibit various levels of diversity and richness. These communities are affected by flooding and are vulnerable to colonization by nonnative species. Since 1996, a series of three high-flow experiments (HFE), or water releases designed to mimic natural seasonal flooding, have been conducted at Glen Canyon Dam, Ariz., primarily to determine the effectiveness of using highAuthorsBarbara E. RalstonA Vegetation Database for the Colorado River Ecosystem from Glen Canyon Dam to the Western Boundary of Grand Canyon National Park, Arizona
A vegetation database of the riparian vegetation located within the Colorado River ecosystem (CRE), a subsection of the Colorado River between Glen Canyon Dam and the western boundary of Grand Canyon National Park, was constructed using four-band image mosaics acquired in May 2002. A digital line scanner was flown over the Colorado River corridor in Arizona by ISTAR Americas, using a Leica ADS-40AuthorsBarbara E. Ralston, Philip A. Davis, Robert M. Weber, Jill M. RundallDo beavers promote the invasion of non-native Tamarix in the Grand Canyon riparian zone
Beavers (Castor canadensis Kuhl) can influence the competitive dynamics of plant species through selective foraging, collection of materials for dam creation, and alteration of hydrologic conditions. In the Grand Canyon National Park, the native Salix gooddingii C.R.Ball (Goodding's willow) and Salix exigua Nutt. (coyote willow) are a staple food of beavers. Because Salix competes with the invasivAuthorsS.G. Mortenson, P.J. Weisberg, B.E. Ralston - Partners
Below are partners associated with this project.