Agroforestry II - Riparian Buffers

Agroforestry II - Riparian Buffers

I. Riparian Buffers & Benefits

Riparian Buffers

Riparian buffers are the interface between land and water. They are adapted to undergo seasonal flooding. Healthy riparian areas provide numerous environmental and social benefits.

A. Improve Water Quality:

Studies show that riparian forests trap nutrients from runoff and retain them.

80% of nitrogen and phosphorus kept from entering stream.

B. Reduce Flood Damage:

Reduce flood damage to property.

During flood events buffers reduce flood intensity and erosion.

C. Streambank Stabilization:

Native grass, trees & shrubs provide deep & extensive root systems of anchor streambanks.

Stiff stems of native trees and shrubs deflect river flow away from streambanks.

D. Provide Wildlife & Fisheries Habitat:

Wildlife Habitat.Food, cover variety

of birds and mammals.

Fish need sustained water supply, shade, and stream-bank shelter.

II. Riparian InfluencesA. Watershed impacts

A watershed is the land area that contributes water to a system of stream channels.

(NRCS, 1998)

Stream Types Across the Landscape

Stream Balance Equation

stream flowX

slope

=sediment load

Xsediment size

Natural channel features

Floodplain

Bankfull

Baseflow

Thalweg

ChannelAxis

(J.C. Fong, 1994, reproduced with permission)

Channel Evolution Model Channel Evolution Model (Space vs. Time)(Space vs. Time)

primary nickpoint

III.II.

oversteepened reach

IV.

aggradation zonedeposits

V.VI.

(from NRCS, 1998)

B. Riparian Disturbances

Dutch Elm Disease (DED)FloodingHerbivore browsingFire

DED ImpactsDED, as an introduced

disease, has created unprecedented destruction of bottomland forests.

Impacts of excessive debris and re-infections will linger for many years.

Flooding Impacts

Flooding is most destructive to understory seedlings and saplings. Midstory pole sized trees are frequently killed with extended inundation. Altered hydrology has made destructive summer flooding more frequent and severe.

Herbivore Impacts

From pre-settlement times with elk and bison to present browsing by white-tailed deer, herbivores have always had a substantial impact to frequently flooded forests.

FireHistoric fires have shaped

the ecotone boundary between prairie and northern hardwood ecosystems.

Fires, along with flooding, have been dominant impacts shaping the seral stage and species composition of riparian forests along the Red River.

C. Riparian Response to Disturbance - Flooding

Physiological Flood Effects

Rapid depletion of oxygen in top 6” of root zone.Anaerobic conditions causing root dieback. Immediate reduction of intake of water and

nutrients by roots.Entire tree is affected by reduced photosynthetic

capacity.

Flood Severity

Timing of flood is most important. Summer floods are much more devastating because of active respiration and photosynthetic demands.

Flood extent is also important in determining the percentage of the tree’s crown submerged and the amount of lenticels covered, which prevents gaseous exchange.

Flood duration affects the extent of dieback of root and stem tissue.

Flood Response & Tolerance

A tree’s response to flooding depends on its capacity to develop adventitious roots and lenticels.

A tree’s age and vigor influence the ability to respond to flooding.

Some tree species are more tolerant and better able to respond to flood effects.

Forests are susceptible to insect and disease attack when weakened by flooding.

Flood Recovery

Trees are dependent on the roots function of providing water, nutrients and auxins for tree growth.

Because of the relationship between tree roots and the crown, recovery or decline may last up to 3-5 years.

Extent of shoot growth is a good measure of trees recovery.

III. Ecological Implications Riparian ecosystems along

the Red River have evolved with disturbances and are resilient.

Diversity is being increased with reduced fire while early successional stages dominate the more flood prone sites.

Increased flooding has allowed establishment of unwanted introduced species.

Bur oak is being replaced by more shade tolerant species that are easier to seed.

Riparian buffers are ecotonal and sensitive to environmental changes.

Ecological Considerations for Restoration

Priority should be given to restoration of original flood prone forests to improve riparian width and connectivity.

Restoration should emphasize quick to establish pioneer species to hold sensitive sites.

Plantation maintenance should allow for natural succession.

Introduced and evasive species should be controlled to allow for natural stand establishment and development.

IV. Restoring Riparian Function

•66 feet on 66 feet on each sideeach side

•Size and Size and composition composition can be can be adjusted.adjusted.

•ContinuousContinuous

Loss of Riparian Function – Upper Watershed

Loss of Riparian Function – Lower Watershed

Restoration Treatments

The current condition of the riparian area will determine the level of treatment and practices needed.

In degraded areas, cease all activities which harm the function or structure of the riparian area.

In highly deteriorated riparian areas, more active management activities may be needed.

Riparian Restoration Practices

Riparian Filter StripsPlanned Grazing Systems & Water

DevelopmentRiparian BuffersForest Stand ImprovementBio-engineering for Streambank

Stabilization Wetland Restoration

Riparian Filter Strips

Native grasses and shrubs.

Restoration on ephemeral and intermittent streams.

May be used with buffers lower in the watershed.

Planned Grazing Systems

3 fold increase in infiltration with corresponding reduction in runoff.

Most effective on the upper watershed.

Water Development

Construction of sediment ponds in upper watershed reduces flooding downstream.

Solar pumps improve riparian areas.

Riparian Buffer PlantingsRestoration buffers

stabilize soils and restores forest function

Trees planted in riparian buffers supplement natural regeneration

Planting can improve the vegetative diversity of the riparian area

Forest Stand Improvement

Thinning and Cull tree removal. FSI improves forest health, vigor and riparian function.

Thinning and Cull tree removal.

Natural Streambank Stabilization Bioengineering

Bioengineering is the use of plant materials and bank reshaping to stabilize streambanks

Bio-engineering Bio-engineering for Streambank for Streambank Protection (Park Protection (Park River Bible River Bible Camp)Camp)

Wetland Restoration

Improve function of riparian areas through restoration of wetlands.

Coordination Best Management Practices including bank stabilization, grass filter strips, riparian

forest buffers and wetland restoration.

Coordinate delivery of multiple programs

North Dakota Game and Fish

North Dakota Soil Conservation Districts

North Dakota State Water Commission

NDSU Extension Service

Red River Regional Council

Red River Resource Conservation and Development

UND Geology Department

Management of flood prone forests requires a collaborative effort with researchers and resource professionals.

Cooperative projects facilitate merging theory and practice to realize successful riparian restoration in the Red River Basin.

David Rush, Project Manager

Red River Basin Riparian Project

516 Cooper Ave.

Grafton, ND 58220

(701) 352-3550

www.health.state.nd.us/RRBRP

Coordinated Restoration Effort

Resource concerns need to be identified by local landowners, Water Resource Board and Soil Conservation District.

Reach restoration needs to be coordinated with RC&D’s, Natural Resource Conservation Service, North Dakota Forest Service and other partners with the Red River Basin Riparian Project.