Presentation on theme: "A Southwest Ponderosa Pine Perspective. Term Ecological Restoration: “the process of reestablishing to the extent possible the structure, function, and."— Presentation transcript:
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: 1. develop a deeper understanding of ecosystem structure and function 2. bring about conditions as close as possible to reference condition so that natural processes can continue 3. 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 procedures However, 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?
Term Evolutionary Environment: The environment in which a species or group of species evolved The environment of speciation
Evolutionary environment for ponderosa pine (pinus ponderosa) Most widespread member of subsection Ponderosae First appears in fossil record in Miocene in Western Nevada Mobile in evolutionary time Environment includes many short term disturbances
Native American Role Inhabited ponderosa pine habitat for millennia prior to the late 1800s Influenced habitat through cultural, hunting, agriculture, and burning practices Natural frequency of fires gave human caused ignitions to have a relatively minor impact
Anglo-American and Hispanic Settlement Introduced species, disruption of natural processes, and land use practices changed evolutionary trajectories Hispanic settlement began in 16 th century, however, impact was localized Anglo-American settlement of Northern Arizona began in the 1860s Around the 1870’s industrial scale resource exploitation, domestic livestock grazing, fire controls
Term Reference Conditions: 1. A spectrum and variability of natural conditions in ecosystem composition, structure, and function 2. 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 Conditions In theory reference conditions should take into account all ecosystem components: Organisms Structures Biogeochemical cycles Disturbance processes Abiotic factors Etc. Is it possible to put this theory into action? Why or why not?
Reference Conditions Some 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 Conditions
Baseline/Reference Conditions 1) Determine key variables 2) Quantify key disturbance regimes 3) Use dendroecological techniques 4) Use other lines of evidence 5) Determine current and historical understory herbaceous and shrub composition
Select Key Variables Small Evolutionary environment of ponderosa pine Practical to quantify
Key Disturbance Regimes High frequency, low intensity Low frequency, High intensity Fire frequency flucuated Cessation of frequent fire after settlement
Quantify Forest Structure/ Pattern Before and after Anglo-American settlement Current structure provides past vegetative structure 1-4 trees per hectare before Hundreds to thousands of trees per hectare after
Structure/Pattern cont. Density and pattern varies from place to place Picking particular date is important for site restoration
Multiple Line of Evidence Historical photographs Early Historical Accounts Results from other researchers Early Forest or Land Surveys
Understory Herbaceous and Shrub Composition Rapid nutrient turnover Provide fuel Plant biodiversity
Understory cont. Dendroecological reconstruction techniques are limited Use separate study sites
Based on Reference Conditions Develop 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 1 Leave All Pre-settlement Trees Trees predate the fire regime disruption date (~ ). 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 conditions Counter Argument: Logging has removed most of the pre-settlement trees Unharvested 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 2 2. 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 place Buffer of 150%-300% of the pre-settlement tree density to compensate for post-treatment mortality.
Restoration Treatment 3 3. 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 4 4. 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 5 5. 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 & 7 6. 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 General Two pronged rationale behind these ecological restoration treatments 1. 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 Function Debate whether restoration of frequent-fire ecosystems must include “intentional structural restoration” (thinning) or if fire alone could do the job. Depends upon: Specific species compositions Soils Fuels
Fire Alone Accomplished 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 century now fire would burn canopy fire 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 Problem Project 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 Pitfalls History 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 over smoke from fires slash disposal short-term aesthetic degradation from thinning and prescribed fires
National Parks and Designated Wilderness Areas Land 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 Park Developing 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.
Conclusion Goal 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 Restoration Broadly consistent with management goals for parks, wilderness, and natural areas Restoration practices may not be easily implemented Liberal 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.