the role of woody debris in riparian zones jon m. flinders
DESCRIPTION
Trees growing in riparian areas may enter river channel through natural and human processes Production of dead wood is often called “woody debris” or WD The significance of WD has been realized in last couple of decades Importance of treesTRANSCRIPT
The role of woody debris in riparian zones
Jon M. Flinders
• Wildlife nesting and rearing sites
• Mediation of stream temperatures
• Habitat for rare plants
• Growth of trees
Riparian areas are important for forested landscapes
• Trees growing in riparian areas may enter river channel through natural and human processes
• Production of dead wood is often called “woody debris” or WD
• The significance of WD has been realized in last couple of decades
Importance of trees
Historical Perspective • 1800’s to early 1900’s rivers &
streams used to transport logs
• Rivers cleared to prevent log jams • Splash dams were used in streams
Post-World War II
• Fisheries Mangers thought woody debris obstructed migration of anadromous fish
• Removed logjams with the intention of opening new reaches of streams & rivers
• Thus, many rivers and streams have not recovered to pristine undisturbed conditions
The Role of Woody Debris
1. Creates Pools & Stream Complexity
• Salmonids need pools for feeding locations
• Logs extending across streams deflect the current
The Role of Woody Debris
2. Traps sediments
• Moderates sediment transport rates
• Protects salmonid spawning areas & invertebrate pop. from sediment deposition
The Role of Woody Debris
3. Stores organic material
• Most organic material stored is allocthonous material
• Organic material is an important energy source for invertebrates
The Role of Woody Debris
4. Provides habitat for salmonids
• Fry utilize WD for refuge from predators
• Pools created allow over wintering areas
Input of Debris in Stream Channels
NATURAL PROCESSES:• Bank failure
• Blow down
• Avalanches
• Collapse due to ice or snow
Input of Debris in Stream Channels
HUMAN CAUSED:• Logging major source of woody
debris and major loss
• Usually small debris entering channel- Less stable- More prone to movement
Debris Management
MANAGEMENT IDEAS:• Buffer strip • Predetermined fraction of
timber• Double rotation basis
- 150 yrs instead of 75 yrs• Substitute structures
- Large boulder- Rock-filled gabions
Debris Management
CONCLUSION:• Removal of large, stable debris causes
loss of important habitat and decline in fish populations
• Thus, need to have a management goal of conserving large, stable debris prior to logging