Equilibrium and Landscape Management Lecture 17 April 19, 2005

Equilibrium and Landscape Equilibrium and Landscape Management Management

Lecture 17Lecture 17April 19, 2005April 19, 2005

Disturbance and Landscape Disturbance and Landscape EquilibriumEquilibrium

Note: All definitions of equilibrium depend on the focal spatial/temporal scale of interest and measurement.

Regional Scale Equilibrium - Climate always changing at long time scales.Local scale Equilibrium - More affected by shorter-term, stochastic events.

RecoveryDisturbance

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Stability: The tendency of a system to move away from a stable state (i.e., a constant range of variation).

Persistence: The length of time a system remains in a defined state (or range of states).

Landscape Equilibrium: DefinitionsLandscape Equilibrium: Definitions

RecoveryDisturbance

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Resistance: The ability of a system to absorb or dissipate disturbances and prevent them from growing into larger disturbances.


RecoveryDisturbance

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Resilience: “persistence of relationships within a system and is a measure of the ability of these systems to absorb changes… and still persist” Hollings 1973.


A.H. Perera and L.J. Buse 2004Emulating Natural Forest Landscape DisturbancesColumbia University Press

Shifting mosaic steady-state: the landscape maintains a constant proportion in each patch type through time, as the random creation of patches by disturbance is balanced by the maturation of old patches through succession.

Typical of the northeastern US forests.

Very stable over long periods of time.

Landscape state

Time

Landscape Equilibrium: TypesLandscape Equilibrium: Types

Stationary process: the landscape is composed of a series of processes whose distributions do not change in time or space.

Example: river flow peaks in the spring, lowest in autumn.

Very stable of long periods of time.

Landscape state

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Bounded equilibrium: the landscape exhibits random changes over time in response to stochastic disturbance events, but remains within bounds.

Example: Vegetative carbon in a prairie is relatively low (‘bounded’) due to fire and grazing. If fire or grazing removed, it may convert to forest with high carbon.

The mean and variance are very sensitive to scale (spatial and temporal). Often very non-stationary.

Landscape state

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Managing Landscape EquilibriumManaging Landscape Equilibrium

Managing Landscape EquilibriumManaging Landscape EquilibriumWhy?Why?

Promote Stability and Resilience:

All ecosystems are adapted to a native disturbance regime.

Therefore, maintaining the composition (flora and fauna) and functioning of that ecosystem may require the maintenance of the natural landscape equilibrium or Range of Natural Variation.


Two common human alterations to landscape equilibrium:

Too much disturbancee.g., clearcutting in the Cascades

Too little disturbancee.g., lack of fire in the BWCAe.g., lack of flooding in the Colorado River


Promote Sustainability:The ability of an ecosystem to maintain ecological processes and functions, biological diversity, and productivity over time.

Sustainable vs. Non-sustainable Disturbances

a. non-sustainable frequency.

b. non-sustainable rate of recovery.

c. non-sustainable severity.

A.H. Perera and L.J. Buse 2004


Promote Conservation:

Maintain genetic variation and fitness.

Maintain viable species populations, particularly those dependent upon patch type and patch configuration (metapopulations).

Maintain species richness: dependent upon natural landscape equilibrium.

Some species may be adapted to a particular disturbance type for reproduction

e.g., fire dependent tree speciese.g., Colorado River fish species

Managing Landscape EquilibriumManaging Landscape EquilibriumWhy? Promote ConservationWhy? Promote Conservation

Example: Maintain the Minimum Dynamic Area (MDA)The smallest area with a natural disturbance regime which maintains internal recolonization sources and hence minimizes extinctions (Pickett and Thompson 1978).

i.e., what’s the smallest sized landscape that will allow enough disturbance to maintain diversity?

Dependent upon disturbance magnitude, variance, frequency, duration.

Fire in Yellowstone Ntl Park

Windthrow gapNortheastern US

versus

Managing Landscape EquilibriumManaging Landscape EquilibriumHow? Disturbance EmulationHow? Disturbance Emulation

What is Emulation?

Emulation is not duplication.

Emulation is not restoration to pre-European conditions.

Emulation is generally very goal oriented. Example, if we want to preserve species X, that requires Y amount of open space, then we need to create Y amount of open space - regardless of how that space is created.

Therefore, emulation usually means re-creating one or two dimensions of a natural disturbance regime.


Question: Emulate what dimension(s) of a disturbance?

Spatial:Mean area/sizeSpatial distribution

Temporal:FrequencyRecurrence intervalReturn intervalRotation period

Magnitude:Intensity - energy releasedSeverity - mortality caused

from A.H. Perera and L.J. Buse 2004

Managing Landscape EquilibriumManaging Landscape EquilibriumHow? Current EmphasisHow? Current Emphasis

Emulate Legacies - Jerry Franklin, U Washington

common in natural disturbancespromote faster recovery to previous state

Emulate Landscape Patternshould clearcuts be dispersed or aggregated?

Emulate Temporal Patternsreintroducing spring floods into rivers through dam release

West Chilcotin Forest Products Ltd.

Managing Landscape EquilibriumManaging Landscape EquilibriumEmulation Tools: ExperimentationEmulation Tools: Experimentation

Experimentationterrestrial: generally small scalelarger scale on rivers

Example: Goal = rebuild sand bars and breeding habitat for Humpback Chubs on Colorado River

Results: Number of chubs declined!

Colorado River during release

Colorado River afterrelease

Managing Landscape EquilibriumManaging Landscape EquilibriumEmulation Tools: ModelingEmulation Tools: Modeling

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FRP = 300

Fire Rotation Period = 50

FRP = 100

No Fire

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Jack pine

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Examples of Examples of Disturbance EmulationDisturbance Emulation

Question: how to emulate fire patterns in the NW-Wisconsin Pine Barrens?

Large open patches are crucial for grassland birds (e.g. sharp-tail grouse). Extensive crown fires provided large open patches at pre-settlement times

Radeloff et al. 2000Restoration Ecology 8: 119-126

Examples of Examples of Disturbance EmulationDisturbance Emulation

Small restoration areas not sufficient to maintain open-habitat species.

Aggregated clear-cuts appear to be suitable to provide the habitat structure necessary for open habitat species.

Simulation modeling used to test alternatives.

Radeloff et al. 2000Restoration Ecology 8: 119-

126


However, managers must often work with incomplete or imprecise information.

Adaptive Management:

Why? Emulation requires more resources than not emulating.

A system for testing effectiveness of disturbance emulation

Requires that meaningful indicators are monitored.

But! Adaptive Mgmt = $

Adaptive Mgmt

Mgmt System(treatment)

Response/Outcome

Monitor/MeasureIndicators

Managing Landscape EquilibriumManaging Landscape EquilibriumNegative Consequence of EmulationNegative Consequence of Emulation

Reduced resource extraction: lower forestry yieldlower electrical yieldresource use displacement?

Negative public perceptions:large clearcut sizes lower lake levels, ‘muddy’ rivers introduced fires: ugly burns, smoke and haze

Loss of recreation valueless jet skiinglower game populations?

May not be sensitive to rare species

Managing Landscape EquilibriumManaging Landscape EquilibriumSummarySummary

Assumptions: Disturbance history is an appropriate model for ecosystem mgmt.

Disturbance is integral to maintaining biodiversity.

We understand all the requisite processes. We don’t.

An emulated disturbance approximates a real disturbance.

There is excess capacity for disturbance emulation.

Managing Landscape EquilibriumManaging Landscape EquilibriumSummarySummary

The emulation of the natural landscape equilibrium or ROV is currently very popular with management and conservation groups. A significant shift from resource extraction first!

However, it is still a new and somewhat unproven concept. Landscape equilibrium happens at long time scales!

Assumption: we know what the natural disturbance regime was and that it was constant!

Assumption: the natural disturbance regime is appropriate for future conditions.

Past disturbance regimes may not be compatible with future climates, species, nutrient deposition, etc.

Managing Landscape EquilibriumManaging Landscape EquilibriumEcological ChallengesEcological Challenges

Lack of knowledge about disturbances across scales and disturbance interactions -> Disturbance Complexity

Terrestrial: Emulating disturbance severity, nutrient releases

Rivers: Emulating water flows at the appropriate water temperatures

Managing Landscape EquilibriumManaging Landscape EquilibriumInstitutional ChallengesInstitutional Challenges

Institutional inertia

Emulation at the proper scales is impeded by multiple land owners.

Overcoming public perceptions of desired goals, safety.

Documents

Equilibrium and Landscape Management Lecture 17 April 19, 2005