#4 Green-tree reservoir

What are 2 types of alluvial, floodplain and depressional wetland systems?

• Central Valley moist soil

• Southern Bottomland Hardwoods

What is the management approach for the Central Valley?

some vegetation management at the individual wetland level (moist-soil management)

How are Southern Bottomland Hardwood wetlands managed?

• Green-tree reservoir management at individual wetland level

• Intensive hydrological and vegetation management

Does the Prairie Pothole Region get actively managed?

Not really

• Minimal to no active management of individual wetlands - passive

• Protection of adjacent landscape

What hydrological conditions define bottomland hardwood swamps?

• depend on seasonal river flooding

  • variable inundation periods

• hydrology driven by precipitation

Where do bottomland hardwood swamps typically occur in the U.S.?

mainly on river floodplains of the southeastern United States

What are the three types of bottomland hydrological pathways?

• Local puddling

• Slow backwater flooding

• Fast headwater flooding

local puddling

• Topography = next to river channel

• water collects in small depressions

Slow backwater flooding

When water slowly inundates areas near the main river channel

Fast headwater flooding

Flash floods reach areas that typically wouldn’t get backflow from river

What major vegetation groups exist in lowland forest wetlands?

• Herbaceous plants

• Woody vegetation

• Forest litter

What do Herbaceous plants in lowland forest wetlands provide?

cover, nutrients, seeds, macroinvertebrates for wildlife

What do Woody vegetation in lowland forest wetlands provide?

trees, shrubs, vines that provide mast (acorns, fruits)

What do Forest litter in lowland forest wetlands provide?

organic matter supporting invertebrates and productivity

What landscape factor heavily influences bottomland forest patterns?

Local topography

• flooding extent

• duration

• vegetation patterns

How has the extent of the Mississippi Alluvial Valley (MAV) changed over time?

Historically >25 million acres; today <4 million acres remain

What are some current major threats?

• Agricultural runoff

• Riverbed incision

• Climate change

• Invasive species and diseases

What major factor caused loss of MAV wetlands in the 20th century?

Agricultural expansion

• supported by river levees that blocked seasonal flooding

Riverbed incision

occurs when the channel deepens due to restricted flooding

• reduces the river’s ability to flood adjacent wetlands and further degrade habitat

What was one act we went over that was really helpful for bringing back wetlands?

Swampbuster Act

• discourages agricultural conversion of wetlands and support wetland conservation

What is the purpose of a green-tree reservoir?

To mimic historical forested wetlands by flooding hardwood stands during the dormant season to provide mast and habitat for waterfowl

When should GTRs be flooded and why?

• when trees are dormant

• less vulnerable to flood-induced damage

  • flooding during active growth can kill them

What is the typical maturation time for a new GTR?

20–30 years to develop, with peak productivity at 50–75 years

What are key site requirements for constructing a GTR?

• Flat/slight slope (<5%)

• Clay soils for water retention

• Reliable water source

• Ability to flood and drain efficiently

What is the typical size of a GTR impoundment?

100–500 acres per unit

Why are low levees (≈1 m) preferred in GTR design?

They minimize flood damage and still provide enough water retention

What common water control structures are used in GTRs?

• Screw gates (pull bottom water)

• Drop-log structures (pull top water via removable boards)

• Flash-board risers (top-withdrawal control)

Describe the typical GTR hydrological schedule

• Flood-up: October (after tree dormancy; for waterfowl arrival and hunting)

• Drawdown: February

What is “mast” in the context of GTRs?

The collective term for tree-produced nuts and fruits, especially acorns

Which tree species are most important for mast in GTRs?

• Oaks, especially pin oak (best acorn producer)

  • Bald cypress (flood-tolerant)

  • Some shrubs (e.g., buttonbush)

• Elms, ash, maple (late-season fruit but low mast)

Why is species diversity important in GTR design?

Different species vary in hydrology tolerance, mast production timing, and value to wildlife, providing year-round resources

How does tree age affect mast production?

Mast production declines in very old trees, so mixed age stands are ideal

What methods are used to create forest disturbances in GTRs?

• Selective timber harvest

• Herbicide treatments

• Girdling

• Firewood cutting

What are some animal spp that are supported by GTRs (other than waterfowl)?

Fish (~15 spp.), mammals (~16 spp.), herps (~25 spp.), invertebrates

Which endangered species may be found in or near GTRs?

• Wood Stork

• American Alligator

• Red-cockaded Woodpecker

• Eastern Indigo Snake

What historic species’ decline is linked to loss of bottomland hardwood forests?

Ivory-billed Woodpecker, which nested heavily in cypress

How does GTR flooding differ from natural hydrology?

GTR hydrology is blocky and predictable

• unlike natural, highly variable flooding cycles. This disrupts natural communities

What are some ecological shifts that can occur in poorly managed GTRs?

• Reduced acorn production

• Altered tree growth

• Loss of midstory trees

• Dominance of large acorn producers

How can beavers become a management problem in GTRs?

blocking water control structures

• prevents proper drawdowns