Presentation on theme: "Equilibrium and Landscape Management Lecture 17 April 19, 2005."— Presentation transcript:
Equilibrium and Landscape Management Lecture 17 April 19, 2005
Disturbance and Landscape Equilibrium 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 Time Normal multiple states operating range State variables
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: Definitions RecoveryDisturbance Time Normal multiple states operating range State variables
Resistance: The ability of a system to absorb or dissipate disturbances and prevent them from growing into larger disturbances. Landscape Equilibrium: Definitions RecoveryDisturbance Time Normal multiple states operating range State variables
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. Landscape Equilibrium: Definitions A.H. Perera and L.J. Buse 2004 Emulating Natural Forest Landscape Disturbances Columbia 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: 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 Time Landscape Equilibrium: Types
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 Time Landscape Equilibrium: Types
Managing Landscape Equilibrium 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.
Managing Landscape Equilibrium Why? Two common human alterations to landscape equilibrium: Too much disturbance e.g., clearcutting in the Cascades Too little disturbance e.g., lack of fire in the BWCA e.g., lack of flooding in the Colorado River
Managing Landscape Equilibrium Why? 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
Managing Landscape Equilibrium Why? 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 species e.g., Colorado River fish species
Managing Landscape Equilibrium Why? 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 gap Northeastern US versus
Managing Landscape Equilibrium How? 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.
Managing Landscape Equilibrium How? Disturbance Emulation Question: Emulate what dimension(s) of a disturbance? Spatial: Mean area/size Spatial distribution Temporal: Frequency Recurrence interval Return interval Rotation period Magnitude: Intensity - energy released Severity - mortality caused from A.H. Perera and L.J. Buse 2004
Managing Landscape Equilibrium How? Current Emphasis Emulate Legacies - Jerry Franklin, U Washington common in natural disturbances promote faster recovery to previous state Emulate Landscape Pattern should clearcuts be dispersed or aggregated? Emulate Temporal Patterns reintroducing spring floods into rivers through dam release West Chilcotin Forest Products Ltd.
Managing Landscape Equilibrium Emulation Tools: Experimentation Experimentation terrestrial: generally small scale larger 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 after release
Managing Landscape Equilibrium Emulation Tools: Modeling FRP = 300 Fire Rotation Period = 50 FRP = 100 No Fire Simulation Year Proportional landscape dominance Jack pine Aspen/birch Red pine White spruce/fir Black spruce Other White cedar White pine Proportional landscape dominance Simulation Year
Examples of Disturbance 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. 2000 Restoration Ecology 8: 119- 126
Examples of Disturbance 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. 2000 Restoration Ecology 8: 119- 126
Managing Landscape Equilibrium How? Disturbance Emulation 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/Measure Indicators
Managing Landscape Equilibrium Negative Consequence of Emulation Reduced resource extraction: lower forestry yield lower electrical yield resource use displacement? Negative public perceptions: large clearcut sizes lower lake levels, ‘muddy’ rivers introduced fires: ugly burns, smoke and haze Loss of recreation value less jet skiing lower game populations? May not be sensitive to rare species
Managing Landscape Equilibrium Summary 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 Equilibrium Summary 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 Equilibrium Ecological 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 Equilibrium Institutional Challenges Institutional inertia Emulation at the proper scales is impeded by multiple land owners. Overcoming public perceptions of desired goals, safety.