Southwestern Ecological Restoration Project
Mt Trumbull, Arizona

Summary of 1996 annual report
(complete text available at http://www.for.nau.edu/-pzf)

Research Design: Restoration of Long-Needled Pine Ecosystems

The southwestern adaptive ecosystem restoration project is the first large-scale ecological restoration attempt in western forests. Here we outline the background of the project, the key ecological components studied, and the specific research studies initiated.

 What is ecological restoration?
· To conserve ecosystem integrity, the coevolved diversity of life, "the first step is to reconstruct a sample of what we had to begin with"--Aldo Leopold.

 · "Ecological restoration is the process of reestablishing to the extent possible the structure, function, and integrity of indigenous ecosystems and the sustaining habitats that they provide (SER 1993).

 Why is restoration of some long-needled pine ecosystems necessary?

 · Western long-needled pine forests, especially ponderosa and Jeffrey pine ecosystems, have declined in diversity and productivity following exclusion of the natural low-intensity fires with which they evolved. Livestock grazing, logging, and wildfire suppression, initiated by Euro-American settlers in the late 19th century, have led to increased density of young trees at the expense of old trees, grasses, wildflowers, and shrubs. Food webs have been altered as insects, birds, and other animals adapted to open forests with a diversity of plants have encountered a new habitat of dense trees.

 · Dense contemporary forests with accumulated fuels are not sustainable. Today wildfires often bum with high intensity, killing plants over thousands of acres, destroying habitat for animals, birds, and insects, and exacting a high social and economic cost.

 · The window of opportunity for intervention may be as short as 15-30 years because of the precarious condition of many ponderosa pine forests and the current high mortality of the slowest organismic variables in the ecosystem (presettlement-era pine, oak, and juniper trees, from 120 to 600+ years old). Since immediate action is needed, ecological restoration occurs in an atmosphere of urgency where "one must act before knowing all the facts; crisis disciplines are thus a mixture of science and art, and their pursuit requires intuition as well as information" (Soule 1985)-- and accepting uncertainty.

 · Restoration to the ecological conditions characteristic of the evolutionary environment is not necessarily a universal goal for all ecosystems. However, at least some natural landscapes are crucial to serve as benchmarks for comparison with altered systems and as a frame of reference for selecting management alternatives.

 · A landscape/ecosystem-scale approach is essential to replicate the natural self-regulating patterns of forest structure and function, including plant and wildlife habitats, cycles of nutrients, seasons and spatial patterns of fire, and to test hypotheses regarding mobile populations and landscape dynamics.

Research Design


The adaptive ecological restoration experiment will test the general hypothesis that ecosystem restoration in ponderosa pine can restore ecosystem health, reduce crown fire risk, and enhance indigenous biodiversity, while improving human habitats.

Hierarchical scaling in space, time, and trophic levels
· Hierarchical ecological structures have often been ignored in research and management but must be addressed in landscape-scale restoration.

 · Spatial scale: Ponderosa and related long-needled pines range from southwestern Canada to northern Mexico. The ponderosa pine landscape at Mt Trumbull covers about 17,000 acres. Inside the overall boundaries of the ponderosa pine-dominated area are meadows, sagebrush communities, "stringers" of pinyon and juniper woodland, and stands of Gambel oak and New Mexican locust. Forest stands are clumpy with varying species, densities, and sizes of trees. Individual plants may range in size from 90feet-tall dominants to seedlings. Sub-plant scales include leaves, stems, and roots, with the finest definable spatial scales probably occurring at the level of sod biochemistry. Disturbance patterns vary in scale from fires that may cover the entire forest, to small patchy fires or clumps of bark beetle mortality, down to individual mortality of plants or plant parts (defoliation).

 · Temporal scale: The evolutionary context is set within the Holocene period (past 10,000 years), characterized by glacial retreat and northward and upward colonization of long-needled pines. Human presence on the Arizona Strip is documented beginning approximately 6,000 years before present. Time periods associated with biological activities range from several thousand years (soil development), to 600+ years (tree lifespans), to 20-40 year pulses of tree establishment, to one to several year lifespans of understory plants and dominant animals. Organisms are affected by seasonal and daily change, with the finest definable scales ranging down to the rates of chemical processes (photosynthesis, combustion). Disturbance patterns also have varying cycles in a hierarchy of time, ranging from daily and seasonal changes (fire behavior, fire season), to annual or multi-year occurrence (fire frequency), extending to long-term changes wish climatic fluctuation.

 · Trophic hierarchies: A broad general view (autotroph-herbivore-predator-detritivore) can be split into an extremely fine separation of subspecies and races. At the finest level of detail there are likely to be organisms which have never been identified (fungi, microorganisms). An intermediate trophic categorization may be based on functional attributes, for example aggregating insects into guilds based on their feeding behavior.

 Key variables
· How can appropriate studies be designed given the tremendous diversity and huge changes of scale inherent in nature?

 · Keystone hypothesis: Certain scales and ecological thresholds are controlled by a small group of keystone organisms and abiotic processes. This structuring set, in turn, strongly affects its own environment and that of the other members of the community. Dominant species and predominant contagious disturbance regimes maintain this self-reinforcing hierarchical pattern of ecosystem structure and function across the landscape (Holling 1992, Perry 1995).

 · Key structuring organisms in the ponderosa pine ecosystem include the trees, herbaceous plants, and animals (mammals, birds, insects) which range within the spatial extent of the forest. Key disturbance forces include fire and human activity. Scales of study should be related to the relevant spatial scales of the key variables (e.g., ponderosa pine distribution, presettlement fire size) as well as the temporal scales (slowest living variable in the system, e.g., 600+ year age of oldest trees).

 Landscape-scale research design
· Success in determining the effects of the Mt Trumbull restoration treatments and ability to apply knowledge to other settings depends on our ability to evaluate the treatments. However, traditional experimental methodologies based on small-plot studies and 'agricultural' experimental models are not well suited to landscape-level research.

Summaries of Research Studies

Permanent ecosystem monitoring plots for long-term monitoring
Long-term monitoring is essential to assess current conditions, reconstruct presettlement ecosystem structure, and evaluate the effects of restoration treatments. Permanent monitoring plots are being established on a 300 X 300 meter grid across the Mt Trumbull landscape (as of September 1996, 167 plots have been installed; see field map on page 15). We have adapted an ecosystem monitoring procedure originally developed by the National Park Service to collect data on contemporary forest structure (trees, shrubs, herbaceous plants, forest floor fuels, canopy closure, and photographic records) as well as dendroecological (tree-ring) sampling from living trees as well as dead presettlement trees to determine tree age distribution and presettlement forest structure. Details on the monitoring plot procedure are given on pages 16-19. Each 50 X 20 meter plot is marked with metal stakes, rock cairns, and tagged reference trees to facilitate re-measurement over many decades. Spatial attributes of the plot grid are recorded in a geographic information system, while basic ecological data is archived in custom-designed software easily accessible for both management and research questions. The presettlement dendroecological reconstruction technique is illustrated on demonstration plots described on pages 28-34.

 Status: 167 plots (3714 acres) sampled. Data currently being analyzed.
Year 2: continue sampling, data analysis.
Completion: multi-year.

 Passerine bird habitat and population responses to ecological restoration
Communities of passerine birds are sensitive to changes in forest structure. Ile diversity and abundance of passerine birds is being quantified with point counts over approximately 2,000 acres at Mt Trumbull using a before-after-control-impact-pairs design. This experimental approach is appropriate for the landscape-scale study of mobile animal populations. Habitat characteristics, assessed on the permanent monitoring plot grid, are correlated with bird counts. Within the control and treatment areas, reproductive parameters are sampled within nest search grids. The Mt Trumbull, study is replicated with another landscape-scale ecological restoration project at Camp Navajo in northern Arizona. Baseline data collected at both sites over three breeding seasons (1996-98) will be compared with post-treatment data to be collected beginning in the year 2000. A detailed explanation and preliminary results are given on pages 19-27.

 Status: approximately 2000 acres sampled.
Year 2: continue sampling for second year of baseline data.
Completion: multi-year

 Restoration of grasses, wildflowers, and shrubs
The herbaceous and shrub understory of southwestern ponderosa pine forests is important for many ecological reasons, including food and habitat for herbivores, nutrient cycling, soil formation and stabilization, and its contribution to biological diversity and aesthetic appeal. Understory species composition and cover have been adversely modified since Euro-American settlement and understory production has declined with increasing tree density. The objective of this study is to develop practical methods for restoring native understory diversity and productivity. Key to restoring the understory is an understanding of the on-site plant material, including aboveground vegetation as well as viable seeds in the soil seed bank. Germination trials will be conducted with soil samples obtained from the 96-1 treatment unit and placed under greenhouse conditions. These soil samples will first be subjected to cold and heat treatments to simulate winter and fire conditions. Upon germination, seedlings will be identified and counted to obtain a preliminary estimate of the plants which may emerge during restoration. In addition, seed traps will be placed in the first treatment unit in 1997 to measure seed rain, which is seed entering the site from the surrounding area. Together, the studies of seed rain and soil seed bank will give an indication

 

oak clumps that have not been thinned, a relationship between oak thinning and growth rate may be established. Old-growth Gambel oak trees are also found in a range of densities: growing in isolation or surrounded by numerous sprouts. Evaluating the growth rate for oaks found in isolation versus those surrounded by sprouts will indicate whether sprouting has an effect on growth rate and survival. In each case growth rates will be measured with dendroecological (tree-ring) methods.
Status: sampling complete at Mt Trumbull.
Year 2: sampling at other sites and analysis.
Completion: 1997.

 Wilderness restoration methods
Ecological restoration is especially important in wilderness areas and parks, places which have been deliberately set aside to preserve natural ecosystems. Simple reintroduction of prescribed fire into altered ponderosa ecosystems is not sufficient to restore the functioning natural ecosystem. However, application of restoration methods such as removal of dense trees, propagation of native understory plants, and treatment of accumulated fuels to protect old trees, may conflict at times with traditional perceptions of appropriate management techniques for these protected areas. The objective of this study is twofold: first, to develop and test 'minimal impact' restoration techniques. Examples may include hand felling of trees, the use of animal power to remove debris, and firing techniques designed to thin trees and consume fuels. The second objective is to explore the social and political context of wilderness and park management in order to seek a consensus on suitable ecological restoration goals and methods in these areas.

 Status: initial study design and literature review.
Year 2: complete design and initiate small-scale (I acre) test treatments.
Completion: 1998.

 Dendroclimatic reconstruction
Climate history over the past several hundred years is recorded in the varying widths of tree rings. Climate has an important influence both on vegetation (species composition, establishment, growth, and mortality) and on the patterns of disturbances such as fire. Increment cores were collected in 1996 from old ponderosa. pine trees growing on sites highly sensitive to climatic fluctuations, such as high, rocky ridges. After these cores are crossdated and measured to develop a long tree-ring width chronology for the Mt Trumbull area, the chronology will be correlated with weather data. 'Me model will reconstruct past climatic trends and will be compared with tree age data and fire history results to search for past climateplant-disturbance connections and to suggest potential future changes.

 Status: sampling complete.
Year 2: dendrochronological analysis and climatic reconstruction.
Completion: 1997.

 Fire history
Frequent, low-intensity fire regimes are characteristic of ponderosa pine throughout its range, but specific knowledge of the characteristics of presettlement fire patterns at Mt Trumbull is important to guide the re-introduction of fire and to permit future evaluation of the restored fire disturbance regime. Fire history reconstruction based on dendrochronological measurement of fire-scarred trees, stumps, and logs is being undertaken at Mt Trumbull to estimate the frequency and seasonality of presettlement fire as wen as determining the date of fire exclusion and developing a record of any postsettlement fires. A key feature of the project is the landscape scale of sampling across the entire ponderosa pine forest, allowing us to explore questions of fire size, intensity, and variability within the ecosystem, issues which have exceeded the scope of many previous studies. Preliminary results are presented on pages 35-36.

 

other factors of soil formation relatively similar (climate, topography, parent material and time), soils that develop underneath ponderosa pine trees can be quite different than soils that develop underneath grass. Phytolith and soil characteristics are presently being examined at 6 study sites in the Gus Pearson Natural Area near Flagstaff and sampling will be extended to Mt Trumbull and other sites in 1997.
Status: testing of method.
Year 2: sampling at Mt Trumbull.
Completion: multi-year.

 With increased funding available at the end of year 1, the following selected studies will be designed to complement the ecosystem restoration research in year 2:

 Physiological response of presettlement trees: to be developed in year 2.

 Changes in soil chemistry and nutrient cycling: to be developed in year 2.

 Small mammal habitat changes: to be developed in year 2.

 Native American ecosystem management practices: to be developed in year 2.