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Site ConditioningSite Modification

ESRM 479Restoration Design

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Site AssessmentPlant Materials

Site ConditioningSite Modification

InstallationManagement

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• What differentiates site modification from site conditioning?

– Site modification usually entails a structural solution to providing a desired condition, service, etc.

– Site conditioning depends more on the autogenic capabilities of a biological community.

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Site conditioning can include

• Preparatory crops/stubble• Mulch• Creation of shade• Addition of topsoil on stripped sites• Building of soil OM by growing vegetation

that can tolerate a degraded site

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• Techniques to ameliorate salinity problems• Bioremediation• Flooding/draining

– To add biomass– To accommodate wildlife– To decrease targeted species

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Preparatory crops, nurse crops

• Conditioning result:– Organic material in soil– Soil biota active– Soil moisture conserved– Erosion decreased– Less disturbance, fewer weeds– Endophytic mycorrhizae survive

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• Grown before restoration (prep)or

• Concurrent with restoration (nurse)

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Standing sorghum

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Planting into wheat stubble

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Cutting a cover crop for green manure

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No-till planting

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Plants drilled into last fall’s crop of green manure

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Live-staked willows

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Live-staked willows, one year old

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• Nurse crop examples– Annual legumes, shading trees, nitrogen-

fixing trees, non-native plantations• Preparatory crop examples

– Sorghum, millet, corn, alfalfa

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Nurse trees: Saguaro emerging from patches of Olneya tesota (Ironwood)

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Nurse trees: Red alder

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Western red cedar seedlings in sunny sites may benefit from nurse trees.

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Mulch

• Mulch– Mulches are placed on top of mineral soils– Most function to condition soils in a number of

ways:• Vapor barrier• Weed barrier• Soil conditioner supporting biological activity in the

soil below (soil becomes more friable)• Add OM

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Wood chip mulch

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• At sites where there will be no care after installation

– mulches keep more moisture in soil• They hold some water• They act as vapor barrier• They temporarily suppress weed growth

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• Mulches can include:– Organic materials

• Straw, hay, wood chips, shredded bark, peat moss, sewage sludge, manure, corncobs, sugarcane trash, shredded paper

– Plastic films– Sprayed petroleum products– Rock, gravel, stones

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Straw mulch

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Rock mulch

26Paper or plastic film mulch

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27Spray mulch

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Shade

• Shade– Modifies a site to the disadvantage of sun-

requiring plants– Creates a micro-climate that can

accommodate sub-canopy species, forest floor species.

– Re-creates the historically most common environment in PNW

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• Shade can be created by structures – Shade cloth– Tree shelters

• Quick-growing trees– Live staking (willows, poplars)– Deciduous species

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Hybrid poplars

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• Shade can exclude some invasive plant species– Reed canarygrass

• May inhibit growth of others– Himalayan blackberry

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Topsoil

• Addition of topsoil– Topsoil should not be added to a restoration

project unless erosion has resulted in a site with inadequate soil or no soil.

– Topsoil contains weed seeds, either from the site where it was collected or the site where it was stored.

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35Post strip-mining

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• Topsoil– Where it has to be imported, precautions

should be taken:• Sterilization• Burial under a local soil• Provision for management practices to exhaust

weed seedbank (normally, repeated cultivation or burning)

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Tolerant vegetation

• Plant vegetation that will tolerate a degraded site

– Tolerant vegetation that will improve the site should be planted.

– Examples: spikerush, clover, grasses, snowberry

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Phytoremediation

• Phytoremediation/Bioremediation– Phytoremediation is the process of removing

pollutants from a site using plants.– Or, depending upon microbial activity to make

the toxin or pollutant become less active.– There are tolerant plants and bio-

accumulators. • Accumulators often need to be harvested to

remove the element in question (e.g., selenium)

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39TCE Removal

Phytoremediation trials

Vegetating brownfield site in midwest

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Salinity

• Salinity-damaged sites– Sites that are damaged by a high brackish

water table may be improved by planting salt-tolerant trees to draw down the water table.

– Planting of salt-tolerant species that increase the soil OM and litter can decrease the toxicity of the salts.

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41Greasewood (native)

Australian pine (introduced)

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• Salinity-damaged sites– Even when planting halophytes, sites may be

too salty.– In such sites, plants may be more successful

if planted in less stressful microsites (shade).– They may be easier to establish by planting

them within the time window after a rain when soil salinity is depressed.

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• Site Assessment• Plant Materials

• Site Conditioning• Site Modification

• Installation• Management

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Site Modification can include a number of different treatments

• Invasive plant removal• Grading• Removal of unacceptable materials

– Weed seedbanks, toxic substances, non-soil• Seedbed preparation• Placement of aboveground obstructions

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• Creation of wildlife habitat structures• Engineered elements

– Weirs, dams, dikes, infiltratration systems, swales

• Plugging ditches and removing tiles• Installing liners• Structurally repairing eroded areas

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• Invasive plant removal– Mechanical removal– Hand removal– Herbicides– Fire– Grazing– Flooding

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• Grading– Contours– Proper hydrology– Landforms (pits, mounds, islands)– Good drainage to prevent erosion

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• Removal of materials– Seedbanks of weedy species– Toxic fill– Non-soil (concrete, building materials)– Fill – Levees or dikes– Excessive deposited sediment– Wood waste– Refuse or garbage– Liners or landscape fabric

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• Seedbed preparation– Mechanical– Chemical– Burning– Biological– Special water harvesting techniques– Special approaches for saline soil or active

sand dunes

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• Seedbed roughening– Provides seed safe sites– Decreases wind erosion– Decreases fluvial erosion and collects water– Increases accumulation of other resources

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• Aboveground obstructions– Provide safe sites– Create shade and block wind– Accumulate resources– Act as obstacles to fluvial flow– Can remove water along contours– Increase soil stability

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• Materials used as aboveground obstructions– Live plants– Stubble– Logs– Rocks– Brush bundles– Fascines– Crimped organic substances (straw, cotton trash,

paper)

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• Creation of wildlife habitat structures– Bird boxes (bat, bee)– Perches, snags– Rubble or rockpiles (reptiles)– Medium-sized woody debris– Buried clay pots, pipes, utensils– Amphibian egg-mass vegetation (spikerush)– On-site placement of brush or wood piles– Feeding stations, watering stations, shade

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• Creation of landscape features that improve wildlife habitat:– Insectaries– Food plots, forage fields– Hedgerows– Conservation tillage– Vegetated corridors– Vegetated ditches– Tailwater ponds– Rock and log weirs

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69Tailwater pond

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• Engineered elements– Weirs– Spillways– Valves– Dams, dikes– Infiltration systems– Leaky berms– Conveyances– Wells– Temporary irrigation– Temporary nurseries– Sediment control– Log jams

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71Narbeck Wetland (Leaky Berms)

72Weirs

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• Plugging ditches and removing tiles– Plug or remove drain tiles– Fill ditches– Remove fill material

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Tile Installation,1909.

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• Installing liners– Rubberized membrane or clay– Many Northwest wetlands sit on a thin layer of

till or clay; moderate excavation could cause leakage into gravelly or sandy layers.

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• Structurally repairing eroded areas– Cribbing– Half-moon dams– Rock walls– Water bars– Structures or obstructions to encourage

deposition– Cottonwood plantings– Picket fences

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Example: Site conditioning, micro-climate modification

• Functional Requirements– Eliminate reed canarygrass

• DP– Create shade using trees

• FR2– Use trees that will be

effective first season

• DP– Plant willow

• Constraints– Reed canarygrass is

resistant to herbicide, mowing, fire

• C2– Trees must be native

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Example: Site modification, invasive plant removal

• Functional Requirements– Spp Z must be removed

• DP– Use herbicide

• FR2– Herbicide must be effective

• DP– Use paint-on application

• FR3– All leaf area must be

wetted

• Constraints– Removal must cause

minimal disturbance

• C2– Herbicide must not drift

• C3– Application must be

finished in three days