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Reference Conditions and Ecological Restoration: A Southwest Ponderosa Pine Perspective

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Reference Conditions and Ecological Restoration:. A Southwest Ponderosa Pine Perspective. Term. Ecological Restoration: “the process of reestablishing to the extent possible the structure, function, and integrity of indigenous ecosystems”. Used in this research to: - PowerPoint PPT Presentation

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Reference Conditions and Ecological Restoration:

Reference Conditions and Ecological Restoration: A Southwest Ponderosa Pine PerspectiveTermEcological Restoration:the process of reestablishing to the extent possible the structure, function, and integrity of indigenous ecosystemsUsed in this research to: 1. develop a deeper understanding of ecosystem structure and function2. bring about conditions as close as possible to reference condition so that natural processes can continue3. communicate with land managers and the public about ecosystem change and factors to be considered in setting management objectives

Ecological restoration is not a fixed set of proceduresHowever, a consistent set of questions and concerns are raised:1. what constitutes natural state and processes for these ecosystems?2. What was the role of humans before and after settlement?3. What are appropriate reference conditions and variables to measure?4. What is ecological restoration?5. What treatments are best for restoration?

TermEvolutionary Environment:

The environment in which a species or group of species evolvedThe environment of speciation

Evolutionary environment for ponderosa pine (pinus ponderosa)Most widespread member of subsection PonderosaeFirst appears in fossil record in Miocene in Western NevadaMobile in evolutionary timeEnvironment includes many short term disturbancesNative American RoleInhabited ponderosa pine habitat for millennia prior to the late 1800sInfluenced habitat through cultural, hunting, agriculture, and burning practicesNatural frequency of fires gave human caused ignitions to have a relatively minor impact

Anglo-American and Hispanic SettlementIntroduced species, disruption of natural processes, and land use practices changed evolutionary trajectories

Hispanic settlement began in 16th century, however, impact was localizedAnglo-American settlement of Northern Arizona began in the 1860sAround the 1870s industrial scale resource exploitation, domestic livestock grazing, fire controls

TermReference Conditions:1. A spectrum and variability of natural conditions in ecosystem composition, structure, and function2. a point of reference against which to evaluate changes in ecosystems 3. A criterion for measuring the success of ecological restoration treatments and ecosystems management experiments

Reference ConditionsIn theory reference conditions should take into account all ecosystem components: OrganismsStructuresBiogeochemical cyclesDisturbance processesAbiotic factorsEtc.Is it possible to put this theory into action? Why or why not?

Reference ConditionsSome suggest working with only a small set of keystone species or highly interactive organisms. Is this methodology better or worse in terms on restoring the ecosystem?

Establishing Reference ConditionsBaseline/Reference Conditions1) Determine key variables2) Quantify key disturbance regimes3) Use dendroecological techniques4) Use other lines of evidence5) Determine current and historical understory herbaceous and shrub composition

Select Key VariablesSmall

Evolutionary environment of ponderosa pine

Practical to quantifyKey Disturbance RegimesHigh frequency, low intensity

Low frequency, High intensity

Fire frequency flucuated

Cessation of frequent fire after settlementQuantify Forest Structure/ PatternBefore and after Anglo-American settlement

Current structure provides past vegetative structure

1-4 trees per hectare before

Hundreds to thousands of trees per hectare afterStructure/Pattern cont.Density and pattern varies from place to place

Picking particular date is important for site restorationMultiple Line of EvidenceHistorical photographs

Early Historical Accounts

Results from other researchers

Early Forest or Land Surveys

Understory Herbaceous and Shrub CompositionRapid nutrient turnover

Provide fuel

Plant biodiversityUnderstory cont.Dendroecological reconstruction techniques are limited

Use separate study sites

Ecological restoration treatments suggested for southwestern ponderosa pineBased on Reference ConditionsDevelop an ecological restoration plan tailored to specific ecological & management concerns at each project site.

Specific Example:Gus Pearson Natural Area (GPNA)General Framework provided

Restoration Treatment 1Leave All Pre-settlement TreesTrees predate the fire regime disruption date (~1870-1880).Argument against: some pre-settlement trees (>120yrs) would have been thinned by surface fires.Basal area (and density) of pre-settlement trees today may be on the high end of the pre-1870 reference conditionsCounter Argument: Logging has removed most of the pre-settlement treesUnharvested areas, low natural mortality rates that existed prior to fire regime disruption, have increased under the competitive stress of dense post-settlement forests.Restoration Treatment 22. Retain post-settlement trees to replace dead pre-settlement trees; while restoring the species composition, density, age, biomass distribution and tree pattern present around the time of fire regime disruption.Other post-settlement trees are thinned and removed off site or burned in placeBuffer of 150%-300% of the pre-settlement tree density to compensate for post-treatment mortality.

Restoration Treatment 33. Protect the pre-settlement and large post-settlement trees from cambial girdling and root mortality by raking forest floor fuels from tree base.In many cases more than 100yrs of accumulated fuels

Restoration Treatment 44. Burn under prescription with repeated surface fires to approximate the natural fire cycle.Fire prescriptions are designed to consume thinning residues and forest floor fuels with minimal impact on retained trees.

Restoration Treatment 55. If natural regeneration of the herbaceous and shrub communities is inadequate, then reseed/transplant the treated area with a native species mix as needed.

Restoration Treatment 6 & 76. Control exotic plant species.

7. Regulate grazing of ungulates so that the treated area can recover and so herbaceous fuels will be adequate for repeated burning at natural intervals.

In GeneralTwo pronged rationale behind these ecological restoration treatments1. Facilitating partial recovery of ecosystem structure and function can lead to reestablishment of natural self-regulatory processes. Eventually leading to restoration of at least part of the original ecosystem dynamics.2. Both restoration of ecosystem structure and reintroduction of fire are necessary for restoring rates of decomposition, nutrient cycling, and net primary production to more natural, pre-disruptive dates.

Structure and FunctionDebate whether restoration of frequent-fire ecosystems must include intentional structural restoration (thinning) or if fire alone could do the job.Depends upon:Specific species compositionsSoilsFuels

Fire AloneAccomplished with low-intensity surface fires every 2-10yrs on large area with no structural manipulation.BUT: Southwestern Ponderosa Pine and lower elevation mixed conifer forests have had an increase in tree densities and fuel accumulations over past centurynow fire would burn canopyfire no longer functions as it did pre-settlement forests

Early Experiments:Simple fire reintroduction often had detrimental effects from a restoration perspective.In 1976: Post-burn, Old-growth pine trees were killed by cambial girdling and root mortality.Post-settlement poles and saplings were not adequately thinned by fire.GPNA: Post-settlement trees were removed and litter raked prior to burning.Restored area had signs of higher microbial activity and positive responses from old growth trees.Limitations of our ecological restoration approach-Limitations associated with almost any land management activity, especially involving tree thinning and prescribed burns

Common ProblemProject implementation is often derailed by disagreements over treatment details and by insufficient funding.Even when groups appear to advocate identical tree thinning and prescribed burning treatments, arguments over tree diameter limits, single vs. multiple entries, and residual forest density have slowed progress.Other PitfallsHistory between agencies or people involved could inhibit restoration plan.Low value of small-diameter trees from thinning contribute to low funds.Many times no funds available for land management agencies and fall short of adaptive management ideals.

Even when things look good-Once projects are operationally implemented, limitations still arise from concerns oversmoke from firesslash disposalshort-term aesthetic degradation from thinning and prescribed firesNational Parks and Designated Wilderness AreasLand is mandated to be managed in its natural condition. Arguments arise because of the initial damage done from thinning can be seen as incompatible with park regulations.Grand Canyon National ParkDeveloping small-scale tests of thinning treatments in areas where fire-only no longer works from too much fuel.Wilderness-sensitive restoration work may rely heavily on humans and animal-powered operations, trading higher costs for decreased mechanical impacts.

ConclusionGoal is not to create a copy of pre-settlement forest,Forest is reasonably close match to the pre-settlement forest, conserving the structure and pattern of the slowest developing organismic variables (old trees) and providing resources for native herbaceous plants and shrubs to return their natural, more productive state.

Strict RestorationBroadly consistent with management goals for parks, wilderness, and natural areasRestoration practices may not be easily implementedLiberal Restoration approach is central for ecosystem management approaches on public lands

Neither pre-settlement ecosystem nor any other ecosystem is ideal for providing habitats for each species or for all the commodity and amenity needs of humans; nor is a relatively open forest best to maximize wood production, or provide dense cover for animals.Real ecosystems cannot simultaneously meet all of these objectives either.Hope of restored ecosystems is to reduce and perhaps reverse human-caused degradation, conserve the most fragile links of natural systems and reduce the potential for catastrophic ecosystem change.