Coyote Willow Riparian
Scenario model
Current ecosystem state
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Management practices/drivers
Select a transition or restoration pathway
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Transition T1A
Invasion of reed canarygrass
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Transition T2A
Improperly managed grazing during times of year when willow is most vulnerable to decline or most susceptible to overuse.
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Transition T2B
Alteration of hydrologic processes
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Restoration pathway R3A
Restoration of hydrologic and biotic process and function
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Transition T3A
Alteration of hydrologic processes
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Restoration pathway R4A
Restoration of hydrologic and biotic process and function
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Transition T4A
Time elapsed under sufficient sediment loads to form an entrenched floodplain
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No transition or restoration pathway between the selected states has been described
Target ecosystem state
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Description
This represents the historical Reference State in pristine conditions. This State may be uncommon due to widespread invasion of reed canarygrass into this site. Erosion and deposition processes are within a historical range of variation, variability in depth to water table and seasonal fluctuations support native vegetation and vegetated communities include all historical functional and structural groups. The historical disturbance regime is intact and driven primarily by climate which influences drought and flood cycles. The resilience and resistance of the site is bolstered by negative feedbacks between vegetation establishment and hydrologic processes that maintains a dynamic equilibrium with geomorphological processes.
Description
SAEX/PHAR3 - Coyote Willow/Reed Canarygrass
This State is similar to the reference state with the exception of invasion of reed canary grass into the site. Erosion and deposition processes are still within a historical range of variation, yet are at risk of transitioning to a less stable state. All structural and functional plant groups are still present, yet composition and richness may be reduced. The historical disturbance regime is intact and driven primarily by climate which influences drought and flood cycles. The resilience and resistance of the site is bolstered by negative feedbacks between vegetation establishment and hydrologic processes that maintains a dynamic equilibrium with geomorphological processes. This state is common due to widespread invasion of reed canary grass in the Western US.
Submodel
Description
(PHAR3/ALPR3) Reed canarygrass/Meadow foxtail
This State is characterized by a low gradient, meandering, deep and narrow stream with ready access to the floodplain. Chanel types are E and C, gradient is less than 0.2/100 ft, width to depth ratio is less than 12 and banks are moderately stable. Composition of willow and other native woody riparian vegetation has been reduced significantly, reducing mid summer shade to less than one percent and making the site vulnerable to channel widening and incision during large runoff events and transitioning to State 4. Reed canarygrass may provide bank stability of overhanging banks, yet it declines where connectivity to the water table is not available. Point bars are characterized by sand, silt and gravels supporting sedge, bulrush and narrowleaf willow. This state also includes stable analogue channels that have reformed following channel incision, widening and creating new floodplains.
Description
PHAR3 - Reed canarygrass
This State is characterized by straightened reaches with higher gradients, reduced sinuosity, unstable banks and disconnected floodplains. Chanel types are C, sinuosity is less than 1.5, gradient is greater than 0.2/100 ft and width to depth ratio is variable. Reed canarygrass has become strongly dominant where willows and other woody riparian vegetation have been reduced. This leads to bank erosion and reduced stream shading (less than one percent in mid summer). Channel widening and incision are common in this state as unstable banks and vegetation loss create a positive feedback loop that decreases resilience to runoff events. Point bars may still support narrowleaf willow and are characterized by gravels, as sand and silt has been lost. Abandoned floodplains transition into terraces and are dominated by drought adapted species that do not require a connection to the water table.
Mechanism
Improperly managed grazing during times of year when willow is most vulnerable to decline or most susceptible to overuse.
Mechanism
This transition may be the result of several disturbances that lower water tables beyond depths that support riparian woody vegetation, alter sediment supply and transport leading to scouring and channel incision, or directly increase flow velocities or flashiness. These may include: alteration of streamflow by irrigation or impoundment leading to a lowering of the water table during times of year when riparian woody vegetation is dependent; removal of beaver; direct manipulation of channel morphology (namely straightening for agricultural or development purposes); removal of large woody debris or large woody debris sources, from channels or adjacent forests and significant alterations of upland watershed vegetation altering peak discharge or sediment loads.
Mechanism
Restoration of hydrologic and biotic process and function through rehabilitation of channel and vegetation structure may be possible but will require considerable inputs, time and cost. This may require the placement of large woody debris, creation or removal of impoundments, alteration of water withdrawals, management changes to adjacent agricultural or grazing practices, or mechanical manipulation of stream channel courses among other intensive interventions. Restoration options will be highly site specific and may not be possible in many circumstances.
Mechanism
This transition may be the result of several disturbances that lower water tables beyond depths that support riparian woody vegetation, alter sediment supply and transport leading to scouring and channel incision, destabilize banks, or directly increase flow velocities or flashiness. These may include: alteration of streamflow by irrigation or impoundment leading to a lowering of the water table during times of year when riparian woody vegetation is dependent; removal of beaver; direct manipulation of channel morphology (namely straightening for agricultural or development purposes); removal of large woody debris or large woody debris sources, from channels or adjacent forests; sustained improperly managed grazing for many seasons; and significant alterations of upland watershed vegetation altering peak discharge or sediment loads. This state will be more vulnerable to these changes compared to State 2 given less stable banks and lower cover of riparian woody vegetation.
Mechanism
Restoration of hydrologic and biotic process and function through rehabilitation of channel and vegetation structure may be possible but will require considerable inputs, time and cost. This may require the placement of large woody debris, creation or removal of impoundments, alteration of water withdrawals, management changes to adjacent agricultural or grazing practices, or mechanical manipulation of stream channel courses among other intensive interventions. Restoration options will be highly site specific and may not be possible in many circumstances.
Mechanism
Given time, if natural channel evolution processes are allowed to take place, and sediment loads are sufficient, the stream will form an entrenched floodplain at a lower depth then the original. The original floodplain will become a terrace, disconnected from the water table and supporting drought adapted plant species. The resulting riparian area will be more confined and of significantly less extent than originally and the capacity of the basin to store water will be reduced considerably.
Model keys
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The Ecosystem Dynamics Interpretive Tool is an information system framework developed by the USDA-ARS Jornada Experimental Range, USDA Natural Resources Conservation Service, and New Mexico State University.