Riparian 

Vegetation 

Monitoring & 

Modeling

Brad Butterfield1 and Emily Palmquist2

1 Department of Biological Sciences, Northern Arizona University

2 Grand Canyon Monitoring and Research Center, Southwest Biological 

Science Center, USGS, Flagstaff
Project C

• LTEMP Goal: Riparian vegetation that is “diverse, healthy, productive, 

self-sustaining, and ecologically appropriate” 

• Research Elements

• C1 – Ground-based Riparian Vegetation Monitoring

• C2 – Determining Hydrological Tolerances and Management Tools for Plant 

Species of Interest

• C3 – Predictive Models and Synthesis

• C4 – Vegetation Management Decision Support

• FY21 Budget: $254,985
C1. Ground-Based Monitoring
C1. Ground-Based 

Monitoring

• 84 randomly selected sites sampled in Aug-Sep 

2021

• Channel margins, debris fans and sandbars

• 45 annually sampled, long-term sandbar sites

• Same locations as Project B
C1. Ground-Based 

Monitoring

• Status and Trends OFR for 2014-2019 

in review

• Temporal variation in vegetation 

resource metrics by year, hydrological 

zone and geomorphic setting

• Individual species of interest, e.g. 

• Interpretation of dynamics in relation 

to management and climate variability

Palmquist, Ralston and Butterfield. In review.
C2. Hydrological Tolerance 

Experiments

• How do hydrological adaptations of the 

dominant species in the Colorado River 

Ecosystem (CRe) influence their responses 

to current and future dam operations?

• What are the hydrological drivers of recent 

expansions of certain species, and low 

success of others? How can the answer to 

this question inform management?
C2. Hydrological Tolerance 

Experiments

• Manuscript from 2020 experiment on 

arrowweed nearing submission*

• Developed techniques for manipulating 

water tables and monitoring physiological 

responses of multiple populations of a single 

species

*Palmquist, E.C., Ogle, K., Whitham, T.G., Shafroth, 

P.B., Allan, G.J. and Butterfield, B.J. In prep. 

Provenance and genotype of a clonal, riparian shrub 

change phenotypes but not flood response under a 

common climatic setting.
C2. Hydrological Tolerance 

Experiments

• Multi-species pilot experiment conducted 

in 2021

• Included CRe species Salix exigua, S. 

gooddingii, S. laevigata

• Manipulated humidity and drought 

outdoors

• Tested new physiological measurements

• Results pending
C2. Hydrological Tolerance 

Experiments

• Phase 1 of TWP experiments coming in 

summer 2022

• Flood and drought

• Physiological responses

• Plants propagated in 2021

• Mesquite, catclaw acacia, hackberry (from 

seed)

• Cottonwood, coyote willow, Goodding’s 

willow, Emory’s baccharis, seepwillow, 

desert broom, arrowweed, tamarisk, 

common reed, horsetail (from cuttings)
C3. Predictive Models and Synthesis

• What are the knowledge gaps in CRe plant ecology, and how can we 

fill them with existing data sources?

• What are the predicted changes to CRe vegetation status in the future 

under current and alternative LTEMP dam operations?
Arrowweed expansion under burned tamarisk along lower 

Colorado River, Needles, CA

C3. Predictive Models and 

Synthesis

• Initiated discussions to integrate with NCPN 

datasets for regional synthesis

• Collaborations with Pat Shafroth and 

Eduardo González (USGS Fort Collins)

• Trait measurements for regionallycommon species

• Synthesis of regional arrowweed 

expansion
C3. Predictive Models and Synthesis

• How does the seasonal 

timing of base flow variation 

impact vegetation?

• We’re using “hydroclimatic” 

variables to model species 

niches to see if the 

seasonality of flows can 

explain who is thriving, and 

who is not, in the CRe

R2 = 0.25

Temperature of Hottest Month (°C)

Temperature of Month with Highest Streamflow (°C)

Preliminary Data, Do Not Cite
C3. Predictive Models 

and Synthesis

• Example: Goodding’s willow 

can be difficult to establish in 

the CRe. Is this because they 

require a more natural flow 

regime?

Mean Monthly Temperature (°C) 

Preliminary data, do not cite

Hydroclimatic responses of Goodding’s willow

Scaled Predicted Habitat Suitability

High Flow

Low Flow
C4. Vegetation Management Decision 

Support

• GCMRC scientists from Projects C, B and D participated in planning 

meetings for NPS non-flow experimental veg treatments

• Potential sites to leverage existing data and meet camping and archeological 

resource goals

• Three sites overlap with long-term monitoring sandbar sites

• Developed shared file system for data exchange
C4. Vegetation Management Decision 

Support

• Paper on population genetic structure of 

several important CRe species published in 

Restoration Ecology

• Implications for plant materials sourcing in 

revegetation efforts

• Results are being incorporated into NPS 

Riparian Vegetation Project Plan

Palmquist and others. 2021. Restoration Ecology