Riparian vegetation restoration in the context of

1
Riparian vegetation restoration in the context of
Tamarix control along southwestern U.S. rivers
Patrick B. Shafroth U.S. Geological Survey, Fort
Collins Science Center
2
Tamarix control
Replacement vegetation
Water salvage
Wildlife habitat
3
What will replace Tamarix after control efforts??

• gt Factors controlling riparian vegetation
  dynamics in arid/semi-arid western North America
• gt Restoration/revegetation post- Tamarix control
• gt USGS capabilities

4

• Tamarix has a broad
• distribution throughout
• western N. America.

5
Tamarix abundance is variable
6
Historical natural riparian vegetation (DYNAMIC)
Streamflow regulation
Land use
Tamarix
Groundwater impacts
Climate
Riparian vegetation with Tamarix (DYNAMIC)
Salinity
Extreme events
Fire
Other species
Tamarix control
Channel modifications
Active management
Novel state(s) (DYNAMIC)
7

• Factors influencing SW woody riparian spp.
• Floods and associated fluvial processes
• Low flows and alluvial groundwater levels
• Salinity
• Fire
• Climate

8

• Floods
• Drive fluvial processes
• gt meandering
• gt narrowing
• gt flood deposition
• create physical disturbance

• moisten sediments
• flush salts
• remove vegetation
• Tamarix has thrived where
• natural flood regimes have
• been modified.

9

• Low flows
• influence alluvial
• groundwater dynamics
• influence water
• availability

Tamarix is relatively tolerant of drought
10

• Soil and water salinity
• species differ in their tolerances
• Tamarix is very salt-tolerant

11

• Fire
• Tamarix stands carry fire well
• Tamarix is fire-tolerant

12
Some common characteristics of successful and
sustainable riparian restoration programs 1)
Causes of ecological degradation identified gt
What has allowed Tamarix to thrive? 2)
Understanding of current and future site
conditions gt Are the conditions that have
allowed Tamarix to thrive changed? Are they
likely to change? gt What species are likely to
thrive under future conditions? 3) Clear,
specific, and realistic objectives.
Prioritization. gt Complete eradication is
usually unrealistic. 4) Monitoring ? Adaptive
management
13
Restoration and revegetation approaches

• natural revegetation
• active restoration

• passive restoration, process restoration
• hybrid approaches

14
Natural revegetation

• Tamarix recolonizes
• annual weeds
• (e.g., Lepidium, Kochia)
• sometimes, natives

• e.g., Pecos R., springs,
• mesquite bosques
• climate/flow dependant

15

• Active approaches
• seeding, planting
• site preparation
• irrigation, weed control
• site specific, expensive

16

• Passive approaches
• remove stressors, restore natural processes,
• allow biotic communities to recover on their
  own
• gt natural streamflow and sediment regimes
• gt cessation of grazing
• gt exotic species removal
• Most successful restoration programs have a
  passive component.

17

• Streamflow management downstream of dams
• Bill Williams R.
• Truckee R.

• managed flooding
• managed base flows

18

• Hybrid approaches
• mimic missing natural processes
• exotic species removal, plus active and/or
• passive measures

19
Assisted regeneration of cottonwood and willow
Seed source Bare surface Moist surface Gradual
drawdown Shallow water table Safe from future
floods Safe from herbivores
Rio Grande Bosque del Apache, NM
20
Assisted regeneration of cottonwood and willow
Seed source Bare surface Moist surface Gradual
drawdown Shallow water table Safe from future
floods Safe from herbivores
Former gravel pit Fort Collins, CO
21
Assisted regeneration of cottonwood and willow
Seed source Bare surface Moist surface Gradual
drawdown Shallow water table Safe from future
floods Safe from herbivores
Boulder Cr., Colorado
22

• USGS capabilitiesriparian restoration
• ecology and dynamics of western riparian
  vegetation
• site evaluation, restoration potential
• cottonwood/willow restoration
• streamflow management
• pre- and post- project monitoring data analysis

23

• Conclusions
• Tamarix occupies a very broad range of riparian
  sites throughout western North America
• the restoration potential of these sites is
  similarly variable, and warrants prioritization
  and consideration of a variety of approaches
• the introduction and spread of Tamarix is
  usually not the primary cause of riparian
  ecosystem degradation
• successful restoration efforts usually require
  addressing primary causes of degradation (which
  tend to favor native species), and do not simply
  focus on removing Tamarix

24
Site evaluation What is likely to replace Tamarix?
Site prioritization, selection Costs/benefits of
vegetation change for water yield, wildlife.
Revegetation/restoration plan
Pre-project monitoring
Tamarix control
Restoration/revegetation
Post-project monitoring
Adaptive management
25
(No Transcript)