Chambers and Miller, Ch. 9
Restoration success depends on understanding:
1) the processes that structure the ecosystem
2) the appropriate temporal and spatial scales
3) the effects of historical and ongoing land use.
Livestock grazing is implicated in most disturbances
Livestock influence riparian ecosystems by:
1) removing herbage (allowing soil temp to rise and evaporation to increase)
2) damaging plants by grazing, trampling
3) altering nutrient cycling by depositing N and removing foliage
4) compacting soil, which increases runoff and decreases water availability to plants.
Other disturbances: roads, recreation
There have also been long-term climate effects (drier, warmer).
Combined climatic and anthropogenic effects:
1) many streams have become isolated from their floodplains
2) surface water/ground water interactions have been altered
3) declines in water tables have resulted in changes in plant species composition
Watersheds: drainage basins.
Riparian Corridors: integrated networks of stream channels and adjacent floodplains and terraces.
Valley Segments: have semi-uniform slopes, widths and geological materials.
Stream Reaches: have relatively uniform channel morphology, bed materials, bank conditions and woody debris.
Successful strategies for restoration are at watershed/riparian corridor scale.
Projects are at the valley segment/stream reach scale.
The most sensitive basins have the quickest and most negative response to disturbance and high-volume runoff.
Flood dominated high sensitivity
Deeply incised low to moderate sensitivity
Fan dominated low to moderate sensitivity
Pseudo-stable moderate to high sensitivity
Briggs, Riparian Ecosystem Recovery, 1996
Grazing may be less the problem than overgrazing.
One heavy grazing on sensitive land can be bad
low vegetation cover
alters plant competition
decreases soil infiltration
increases soil erosion
stream characteristics modified:
loss of bank undercuts
Livestock Management to decrease riparian impacts
decrease grazing intensity
develop upland water sources
Re-vegetating livestock-damaged areas
You must first analyze: 1) channel stability
2) water availability
Understand the potential for autogenic re-vegetation
Livestock and re-vegetation are not compatible
Plants palatable to livestock must be protected for the first two growing seasons.
Non-palatable species should be protected from trampling.
Hiking, camping, off-road vehicles
loss of vegetation
lowered organic matter
loss of macroporosity
ORV’s cause the same changes, only quicker.
adjust use levels
keep trails and campsites away from sensitive areas (easily disturbed sites, new restorations)
confine camping to a few sites
install interpretive signage
Do not install a restoration project without controlling use
live stakes may be used as firewood
seedlings may be run over by vehicles
irrigation systems may be torn up.
Southwestern invasives include salt cedar (Tamarix), Russian olive (Eleagnus) and Bermuda grass (Cynodon).
Usually they come to dominate after hydrology has been modified (salt cedar does well in artificial flow regimes).
Invasives negatively impact restoration efforts.
Salt cedar control
bulldozer (where there are no natives)
Typical control regime
Cut trees down in fall (cut 5 cm above ground)
Paint cut cambium with Garlon or Tordon within minutes of cutting
Re-cut and herbicide sprouts within a year.
Some wildlife impact restorations
Some eat vegetation:
Some will gnaw irrigation lines:
Protecting restoration from wildife:
Provide beaver with alternate food sources
Build beaver cages out of chicken wire or hardware cloth
Revegetating riparian sites characterized by groundwater decline
Low water availability occurs where groundwater levels are 3m or more below the surface.
Planting riparian plants there is difficult.
Survival rates are low.
Sources of decline:
ground water pumping
Plant material must be matched to site
Planting riparian species may no longer be practical
Flood plain spp. may be more appropriate:
mesquite, palo verde, hackberry
Riparian spp. may not have enough water:
willows, poplars, walnut, ash
Seedlings may be especially vulnerable to low water availability.
Available moisture from spring flooding dries up quickly with onset of summer.
Roots of seedlings must keep up with the retreating zone of soil saturation.
Timing of planting is critical.
Some techniques that work:
1) Large poles (poplar trees)
P. fremontii in this case.
Use where groundwater is more than 3m deep
Holes must be dug or “stinger” used.
Ground must support equipment.
Drill must go through cobble (not easy).
2) Drilling to groundwater
Drill 18 cm diameter hole.
Fill with alluvium.
Plant tree in hole.
Irrigate from top.
Often will not wet soil deeply enough to induce roots to grow to groundwater.
Must carry on for one or two seasons.
Plant more individuals in places likely to have extra available moisture:
Problem: trees planted in wetter sites may also be more flood-prone
Flood energy may disturb vegetation.
Prolonged inundation may kill trees
Even phreatophytes can be damaged under prolonged flooding.
Fine-grained soils more prone to anaerobiosis.
Channel instability can degrade associated riparian ecosystems two ways.
1) Destruction of vegetation through bank erosion.
2) Dewatering of riparian zone.
Developing restoration projects along unstable alluvial stream channels.
Time to implement recovery plans is either 1) before obvious downcutting and erosion have occurred, or 2) after the site has undergone a major erosional event and has begun to stabilize.
General categories of strategies:
2) installation of streambank stabilizing structures.
Planting closest to stream results in the greatest chance of loss due to flood disturbance.
Planting far away from stream results in the greatest chance of vegetation failure due to lack of soil water.
Best sites include:
1) just downstream of concave stream reaches (accreting areas)
2) downstream of large boulders or other obstructions (like logs).
Plant along an elevational gradient so that there is an optimum elevation range along the planting line.
Plant vegetation in the geomorphic position it does best in.
Willows go in dynamic landscapes near river channels.
Catclaw (Acacia gregii) is drought-tolerant and does well on old stream terraces.
Revegetation offers several advantages over instream structures.
It is self-maintaining.
Plants may resist a variety of environmental conditions and flood forces.
Plants are cheaper.