Ponderosa Pine forest with lupine
ERI
Resources

PostHeaderIcon Southwest Fire Initiative

PDF Print E-mail

After the severe wildfire season in 2000, Northern Arizona University began a wide-ranging research initiative on forest restoration. The results of two years' research were presented at the Southwest Fire Initiative Conference on April 29, 2003. These results were also replicated below, along with updated information. Information on each of the projects is available by clicking on the title. If you have further questions about the Southwest Fire Initiative, or the results of the research, please contact Pete Fulé at 928-523-1463, or by This e-mail address is being protected from spambots. You need JavaScript enabled to view it.

Assessment of Burn Severity Using Landsat 7 ETM+ Imagery and Ground Data.

Allison E. Cocke, Peter Z. Fulé, Joseph E. Crouse

Burn severity can be mapped using satellite data due to changes in forest structure and moisture content caused by fires. The 2001 Leroux fire on the Coconino National Forest, Arizona burned over 24 pre-existing permanent 0.1 hectare plots. Plots were re-measured following the fire.  Landsat 7 ETM+ imagery and the Normalized Burn Ratio were used to map the fire into four severity levels immediately following the fire (July 2001) and one year after the fire (June 2002). Ninety-two Composite Burn Index (CBI) plots were used to assess the accuracy of the fire severity maps. Pre- and post-fire plot measurements were also analyzed according to their imagery classification. Ground measurements demonstrated differences in forest structure. Areas that showed up as severely burned on the imagery were predominantly Pinus ponderosa stands. Factors including tree density and basal area, snag density, and fine fuel accumulation were associated with severity levels. Tree mortality was not greatest in severely burned areas, indicating that the Normalized Burn Ratio is comprehensive in rating burn severity by incorporating multiple forest strata. While the Normalized Burn Ratio was less accurate at mapping perimeters, the method was reliable for mapping severely burned areas that may need immediate or long-term post-fire recovery.

Keywords: Normalized Burn Ratio, ponderosa pine, mixed conifer forest, Arizona.

Back to top of page.
Reconstruction of Age Structure and Spatial Arrangement of Pinyon-Juniper Woodlands and Savannas of Anderson Mesa, northern Arizona.

A. Gascho-Landis, and J. Bailey

We examined age structure and spatial arrangement of pinyon-juniper woodlands and savannas on six plots distributed across three different soil types in northern Arizona.  These stands, as typical of many others in pinyon-juniper ecosystems, have experienced increases in tree densities since the arrival of European settlers.  The goal of this study was to reconstruct stand conditions in 1860, prior to livestock grazing, using stem-mapping to determine tree arrangement and tree-ring analysis to examine age structure and density.  Ripley’s K(t), Ripley’s K12(t), and Moran’s I were used to analyze nearest neighbor distances, spatial association, and spatial autocorrelation, respectively.  Current tree densities have more than doubled relative to densities in 1860 across all sites.  All sites have long term presence of juniper and pinyon trees, with a pulse of establishment and survival occurring between 1860 and 1880 on basalt- and sandstone-derived soils. In contrast, limestone-derived soil had no pulse of tree establishment in 1860, but rather a steady increase in tree establishment since circa 1700.  Spatial arrangement of juniper trees in 1860 showed strong clumping patterns from a minimum distance of 15 m to all spatial scales.  Pinyon pine varied in spatial arrangement from clumping at all spatial scales to random at all spatial scales.  Positive spatial autocorrelation was determined for age of juniper trees to a minimum distance of 21 m in current stand conditions, in contrast to no strong trends of spatial autocorrelation in 1860.  By comparing the age structure and spatial results for the forest reconstruction of 1860 to current conditions, we were able to show variation among soil types in nurse tree association between pinyon and juniper trees and unable to support the density dependent mortality hypothesis for these sites.  Presettlement (1860) diameter distributions and basal areas can be used to develop structure control (BDq) prescriptions unique to each soil type to restore either savanna or woodlands condition.  However, identifying one blanket prescription for tree reduction in pinyon-juniper ecosystems of the southwestern United States, or even the Anderson Mesa landscape, would reduce the range of variability present in the form of woodlands and savannas.

Keywords: pinyon-juniper, age structure, spatial arrangement, restoration, structure control, BDq

Back to top of page.
Long-term Effects of Restoration on the Function of a Ponderosa Pine-Bunchgrass Ecosystem

Stephen C. Hart, Sarah I. Boyle, Daniel R. Guido, Jason P. Kaye, Jennifer Thomas

Fire suppression, heavy livestock grazing, and selective harvesting since Euro-American settlement have dramatically altered forest structure in ponderosa pine and other interior forests of the western U.S. Some of the presumed consequences of these changes in fire regimes and forest structure include decreases in soil water content, litter decomposition, and nutrient availability to plants; however, these hypotheses remain largely untested. In 1993 and 1994, an experiment was initiated at the Gus Pearson Natural Area (GPNA) to ecologically restore pre-settlement forest structure to a ponderosa pine-bunchgrass ecosystem and to determine whether restoration of forest structure altered ecosystem function. Short-term (1 to 2 y after treatment) measurements at GPNA showed that restoration increased soil temperatures and microbial activity, increased soil nitrogen availability (the most limiting plant nutrient in these ecosystems), slightly increased ponderosa pine litter decomposition and nutrient release, but had relatively little effect on soil water content. It is unclear, however, if these initial ecosystem responses to restoration are indicative of longer-term responses. We remeasured these same ecological processes within the GPNA experimental plots to assess the longer- term responses of this ecosystem to intensive ecological restoration treatments. By comparing shorter- and longer-term responses, we hope to provide novel information on the rate of change of these ecosystems to intensive ecological restoration treatments, and the importance of the inclusion of frequent burning on these responses. These data will be invaluable to land managers, environmental and conservation groups, and concerned citizens for designing and implementing landscape-scale restoration activities throughout the Southwest.

Keywords: ecosystem processes, litter decomposition, soil enzymes, soil microbial activity, soil microorganisms, soil microclimate, soil nutrient availability, soil water availability

Back to top of page.
Identification and Evaluation of Approaches to Public-Private Partnerships in Ecological Restoration: Final Report

Denver Hospodarsky, Martha E. Lee, and Thomas Combrink

This report is in response to instructions to Southwest Fire Initiative investigators sent on 11-11-03 from Pete Fule, School of Forestry, Northern Arizona University.  The report is divided into four sections suggested in the instructions to investigators. Topics within the four main sections of this report are presented in the following order: Whether or not proposed goals and objectives were achieved; detailed description of research results; summary of budget expenditures and departures from original, approved budget; and how research information has been and will be disseminated to relevant audiences.

Back to top of page.
A Baseline Study Characterizing Small Diameter Ponderosa Pine Logs.

Principal Investigators:  Debra Larson and Richard Mirth

Project Collaborators: Carl Cawood, Ron Wolfe and Brett KenCairn

Student Research Assistants: Jeffery Baer, Seth Teora, Nathan Wallace, Sean Cockrell, Jeff Garney, and Dennis Sobieski and Kathleen Carey.

Ninety-nine roundwood bending specimens and 250 roundwood compression specimens were tested over the course of eleven months in late 2001 and extending through the summer of 2002 at the College of Engineering and Technology at Northern Arizona University in Flagstaff, AZ.   These specimens were taken from 5.0 to 12.7-in. DBH ponderosa pine trees cut from Unit 16 of the Fort Valley Ecosystem Restoration Project located in wildland-urban interface of the Coconino National Forest.  The specimens were sorted into two groups as a function of processing:  hand-debarked logs known as tapered specimens and machine peeled logs known as uniform specimens.  Each group of tapered and uniform logs contained both butt and tip specimens.  This work provides evidence of relationships between juvenile wood and roundwood strength and stiffness for bending members. Failure mode in bending was also impacted by juvenile wood.  This work shows that processing a tapered log down to a uniform log of constant diameter reduces bending strength and stiffness, while increasing the percent juvenile wood in the cross-section.  Butt logs in bending were stronger and stiffer than tip logs.  Compression specimens did not realize the same processing, juvenile wood, and stem location results. Stress risers were a more important variable for determining specimen compression strength.  This work makes suggestions regarding design values at the working stress level for both compression and bending, and provides green-dry strength and stiffness ratios.

Back to top of page.
Quantifying Forest Reference Conditions for Ecological Restoration: The Woolsey Plots.

Margaret M. Moore, David W. Huffman, Jonathan D. Bakker, Andrew J. Sánchez-Meador, David M. Bell, Peter Z. Fulé, Pablo F. Parysow, W. Wallace Covington

We compared historical (1909-1913) and contemporary (1997-1999) forest structure and composition on 15 permanent plots in ponderosa pine (Pinus ponderosa Dougl. ex Laws.) forests of Arizona and New Mexico.  We used the same sampling methods as in the early 1900s and compared stand density, diameter distributions, species composition, and broad age-classes from the two periods.  Stand density (trees ³ 9.14 cm DBH) significantly (p < 0.001) increased on plots from an average of 77.4 trees per plot (s = 49.9) at plot establishment in 1909-1913 to 519.1 trees per plot (s = 252.3) at remeasurement in 1997-1999.  Basal area significantly (p < 0.001) increased from 8.0 m2 per plot (s = 3.5) to 28.5 m2 per plot (s = 10.1).  Contemporary tree diameter distribution shifted towards smaller size classes as demonstrated by a significant (p = 0.001) decrease in quadratic mean diameter from 38.5 cm (s = 7.5) in 1909-1913 to 28.6 cm (s = 7.1) in 1997-1999.  Broad age-classes yielded an average of 61.5 (s = 49.5) residual live trees classified as “blackjack” ponderosa pine (P. ponderosa < 150 yrs) and 13.3 (s = 11.9) “yellow pine” (P. ponderosa ³ 150 yrs) in 1909-1913.  In 1997-1999, 416 live trees (s = 229.6) were “blackjack” and 57.2 (s = 28.5) trees on average were “yellow pine”.  Twelve of the 15 plots were not invaded by other tree species (remained pure ponderosa pine type), while composition shifted slightly on three plots towards more shade-tolerant and fire-intolerant species.  Ninety-one percent of the historically (1909-1913 or older) mapped tree structures (live trees, snags, logs, stumps, etc.) were relocated, which suggested that the forest reconstruction field techniques are reliable within 10%.  Dramatic increases in tree densities may represent an increased potential for bark beetle epidemics and stand replacing wildfire over large areas in the Southwest.

Keywords:  Pinus ponderosa, forest structural changes, residual stands, early 1900s, reference conditions, T. S. Woolsey, Jr., G. A. Pearson, Arizona, New Mexico.

Back to top of page.
Documenting and incorporating Navajo Traditional Land Management and Ecological Restoration Practices in Pine and Fir Uplands and Assaayi Watershed of the Chuska Mountains.

Gary Nabhan, Laura Monti, Tony Joe, Patrick Pynes, David Seibert and Lisa Classen

The goals of this project were to document and incorporate traditional Navajo land management practices in a field cultivation and watershed restoration demonstration site that increase habitat for biodiversity and reduce fire hazards in the Bowl Canyon/Asaayi Lake of the Chuska Mountain Forest in the Navajo Nation. Our research objectives were to examine how traditional Navajo forest and land values and practices relate to land health and wildfire prevention.  Interviews and meetings were held with individuals, community groups and natural resource management leaders over a two year period. We established a study site in the Asaayi Lake Watershed. Navajo elders and adult teachers and elders guided youth from the area to implement erosion control techniques and traditional field cultivation practices. This intergenerational interaction around ecological restoration activities fostered Navajo youth consciousness of traditional Navajo land ethics and stewardship while facilitating capacity building for adults and youth in ecological restoration principles and practice for wildfire prevention.  We identified the following Navajo land use and agro-forestry management practices that can contribute to ecological restoration and wildfire prevention: 1) field cultivation for biodiversity; 2) seasonal burning followed by fallow periods; 3) the use of tree windbreaks and fire retardant hedgerows; 4) maintenance of traditional water diversion canals or ditches, and 5) the use of small diameter timber for erosion control structures, fence posts and shelter. This case study indicates that inter-agency partnerships, combined with a community-based intergenerational approach is an effective way to  develop the local leadership and technical expertise required to implement long-term, community-based forest restoration initiatives.

Back to top of page.
Chemical Speciation of PM 2.5 Collected During Prescribed Fires of the Coconino National Forest near Flagstaff, Arizona.

Marin S. Robinson, Jesus Chavez, Sergio Velazquez and R.K.M. Jayanty

The use of prescribed fire is expected to increase in an effort to reduce the risk of catastrophic fire, particularly at urban/forest interfaces. Fire is a well-known source of PM2.5, small diameter particulate matter known to affect climate, visibility, and human health. In this work, PM2.5 was collected during seven first-entry burns (flaming and smoldering stages) and one maintenance burn of the Coconino National Forest. Samples were analyzed for organic and elemental carbon (OC/EC), cations (sodium, potassium, ammonium), anions (nitrate and sulfate), and 48 elements (with atomic weights between sodium and lead). The PM2.5 contained high OC levels (typically> 90% by mass), commonly observed ions (potassium, ammonium, and nitrate) and elements (potassium, chlorine, sulfur, and silicon), as well as titanium and chromium. Flaming produced higher potassium and ammonium levels than smoldering, and the elemental signature was more complex (20 vs. 7 elements). Average OC x 1.4 mass fractions (± std dev) were lower during flaming (92 ± 14%) than smoldering (124 ± 24%). The maintenance (grassland) burn produced lower particle concentrations, lower ammonium and nitrate levels, and higher potassium and chlorine levels than the first-entry fires.

Back to top of page.
How Resilient Are Southwestern Ponderosa Pine Forests After Crown Fires?

Melissa Savage and Joy Nystrom Mast

The exclusion of low-severity surface fire from the ponderosa pine forests of the Southwest has changed ecosystem structure and function such that severe crown fires are increasingly causing extensive stand mortality.  This altered fire regime has resulted from the intersection of natural drought cycles with human activities that have suppressed natural fires for over a century.  What is the trajectory of forest recovery after such fires?  This study explores the regeneration response of ponderosa pine and other woody species to crown fires that occurred in the region from the late 1940s to the mid-1970s.  We address two main questions: 1) what is the success of natural regeneration and the survival rate of planted ponderosa pine seedlings, and 2) can these sites burned in fire severity outside the natural range of variation be "captured" by other woody species on the scale of decades.  This set of burns offers an opportunity to investigate whether anomalous crown fires may be driving ponderosa pine forests past a critical threshold into new domains at the temporal meso-scale (Moir and Mowrer 1995).  A range of recovery states were found, including sites captured by grasses or shrubs and unnaturally dense ponderosa pine stands vulnerable to further crown fire.

Keywords:  disturbance, fire, regeneration, ponderosa pine forest, anthropogenic change, resilience, alternative states, Southwest

Back to top of page.
Restoration thinning and whole tree water relations: An unexpected relationship in ponderosa pine leaf area to sapwood area ratio.

K. Simonin, T. E. Kolb, M. Montes-Helu and G. W. Koch

To understand the effect of intraspecific competition and tree size on water relations we compared whole-tree hydraulic conductance (KH) and leaf specific transpiration (EL) of ponderosa pines (Pinus ponderosa) in an unthinned plot to trees in a thinned plot in the first and second years after thinning in a dense Arizona forest.  KH and EL were calculated using whole-tree sap flux measured with heat dissipation sensors.  KH and EL were negatively correlated with leaf area to sapwood area ratio (AL:AS) in both the thinned and unthinned plots. Contrary to previous studies of ponderosa pine, AL:AS was positively correlated with tree DBH.  Thinning increased tree predawn water potential within two weeks of treatment.  Effects of thinning on EL and KH depended on tree size and drought severity.  During severe drought in the first growing season after thinning, EL and KH of small trees (16-25 cm DBH; low AL:AS) were lower in the thinned plot than the unthinned plot, suggesting a reduction in stomatal conductance in response to thinning.  In contrast, EL and KH were similar in the thinned plot and unthinned plot for larger trees (26-36 cm DBH) during the drought.  During non-drought periods, EL and KH were generally greater in the thinned than the unthinned plot for all tree sizes.  Our results stress the importance of stand competitive environment as an influence on tree-size related variation in AL:As,and the role of AL:As and drought on whole-tree water relations response to thinning.

Keywords: Arizona, carbon allocation, competition, hydraulic conductivity, leaf area to sapwood area ratio, ontogeny, Pinus ponderosa, thinning, water relations.

Back to top of page.
Fire and grazing effects on semi-arid grasslands associated with Southwestern ponderosa pine forests—Landscape analysis.

T. Sisk, M. Loeser, and T. Muñoz Erickson.

Objectives were (1) address the feasibility of restoration-based fuels treatments in the grasslands of ponderosa pine forests with 2 primary emphases: a) measure responses of plant biodiversity to various treatments of fire and grazing, and link these responses to measures of ecosystem function; and b) conduct a thorough analysis of collaborative land management teams as a means to accomplishing ecosystem restoration and management.  (2) Analyze biodiversity and productivity in the grasslands associated with ponderosa pine forests.  We focused our efforts on measuring plant diversity and productivity along disturbance gradients at plot and landscape-scales.  (3) Study a range of restoration options through which fire and grazing treatments may help achieve diverse objectives including, but not limited to, wildlife enhancement, soil and water conservation, beef production, cultural preservation, and aesthetic value. (4) Transfer the knowledge generated from this work to both scientific and public audiences via publications in a wide range of outlets, and through diverse educational activities, including workshops and on-the-ground training.

Understanding grass productivity and range condition in ponderosa pine forests are critical to future management and introduction of natural fire.  This work contributes important information for utilization of forest resources.

Back to top of page.
Fire effects on soil-water content in a high-elevation riparian meadow at Hart Prairie, AZ.

Abraham E. Springer, Thomas E. Kolb, Regina M. Mullen

One of the largest Bebb willow communities in the U.S. is found at Hart Prairie, AZ.  However, negligible recruitment has been occurring over the past several decades.  The decline of this community can likely be explained by inadequate soil-water content for seed germination.  It was hypothesized that a prescribed burn would reduce biomass, thereby increasing soil-water content.  To test this hypothesis, three treatments were randomly applied to replicated circular plots (2m radius) in herbaceous communities dominated by bracken fern or grasses 1) unburned control, 2) early-growing season burn (7/5/01), and 3) late-growing season burn (9/22/01).  Soil-water content (0-30 cm) was measured on a weekly basis from the center of each plot during the 2001, 2002 and 2003 growing seasons.  Soil-water content was increased for approximately four weeks following the early-season prescribed burn, with an average increase of 2.7% in the fern-dominated community and 8.5% in the grass-dominated community.  However, early-season and late-season burn treatments resulted in lower soil-water content in the 2002 and 2003 growing seasons.  Results indicate that a prescribed burn has the potential to increase or decrease soil-water content, depending on the length of time since the burn.

Keywords: Prescribed burn; Fire; Soil-water content; Soil moisture; Riparian; Grassland.

Back to top of page.
Functional Groups as Bioindicators of Forest Health in Northern Arizona Ponderosa Pine Forests.

S. Skye Stephens and Michael R. Wagner

Reintroduction of fire and thinning have been suggested as the main practices to regain forest health in northern Arizona ponderosa pine forests.   Recent silvicultural programs and the occurrence of catastrophic wildfires have created a range of disturbance severities and a mosaic of forest conditions including 1) unmanaged, 2) thinned, 3) thinned and burned, and 4) wildfire.  We assessed changes occurring in ground foraging ant functional groups at the stand scale as related to these treatments.  A pitfall trapping scheme was implemented during the summer months of 2002 and 2003. A total of 18,009 specimens were collected representing 20 species from ten genera.  We found that traditional biodiversity measures, such as species richness, diversity and dominance were a less satisfactory measure than functional group analysis which allowed us to consider the ecosystem role of each species.  We found that different functional groups were dominant under different levels of disturbance severity and suppressed or excluded other functional groups that were less suited to the disturbance intensity.

Keywords: Pinus ponderosa, Formicidae, forest health, functional groups, bioindicators

Back to top of page.
Impacts of forest thinning to reduce fire hazard on watershed hydrologic functions.

Aregai Tecle

Research Question: How does vegetation management to reduce fire hazard influence the hydrology and water resources of the Rio de Flag watershed?

Project accomplishments to date:  to answer the research question, the project included a number of tasks performed.  The results include (1) water balance modeling of the hydrology of the Rio de Flag watershed to determine amount of monthly average flows, (2) studying the impacts of slash burning on soil water content, chemical, physical and vegetation characteristics, (3) estimating the impacts of forest treatment to minimize catastrophic fire hazards on peak flows in the Rio de Flag, and (4) many other relevant information.  The results are being disseminated to potential users in the form of seven published papers, one paper in print, four papers submitted for publication, one completed master’s thesis and another one in the process, fourteen presentations at national and regional meetings (see the list of abstracts of papers, theses titles and presentation topics in Attachment 1). The research activities leading to these products included measurement of physical watershed characteristics such as soil moisture content using TDR, soil infiltration capacity using a Merriotte double ring infiltrometer, and watershed spatial features using GPS, and gathering available climatic, topographic and vegetation data, and analyzing the various pieces of information using GIS and the U.S. Army Corps of Engineers Hydrologic Engineering Center’s Watershed Hydrological Modeling (HEC WHM) system. To our knowledge, this is the first time, a comprehensive water balance modeling of the Hydrology of the Rio de Flag watershed has been attempted and we hope that with further funding and future efforts, we will develop a more accurate and highly reliable model. That will involve relatively costly field measurements such as stream flows, groundwater recharge, and plant water consumption. Our goal is to use the Rio de Flag watershed as a permanent research and demonstration site for evaluating the impacts of forest fuel reducing treatments such as thinning and prescribed fire on the hydrology and water quality of the area and other similar watersheds elsewhere.

Back to top of page.
Forest Restoration at Centennial Forest: Projects on the NAU Centennial Forest.

Michael R. Wagner

The proposed activity was to identify and inventory “old growth” areas on the Centennial Forest and implement forest restoration treatments on at least 4 replicated 100-acre experimental sites.  These treatments were designed so as to be an appropriate experimental extension of the Stand Treatment Impacts on Forest Health (STIFH) experimental protocol (see Appendix A for example of full prescription).  Experimental treatment sites have been made available for research by all appropriate and interested research groups within established Centennial research and activity policies.

In addition to the 4 old growth restoration areas, we have conducted fuels reduction treatments on an additional 200 acres in the Arboretum and West project treatment areas on the Centennial Forest.  These treatments were high priority fuels reduction activities designed to significantly reduce fire risk to the Arboretum at Flagstaff and the new West Wood Estates Development.  These fuels reduction projects have created research opportunities for the Centennial Forest, ERI and many others across the NAU campus and northern Arizona.

Proposal activities have addressed the “research, develop, monitor and conduct fuels treatments” objectives established by the Bureau of Land Management in funding of ERI.  To date, we have completed 400 out of 600 acres of actual treatment and the perquisite inventory, analysis, and federal and state compliance-related activities.

Back to top of page.
 

Copyright © 2009 All Rights Reserved.
webmaster-eri@nau.edu

Ecological Restoration Institute
P.O. Box 15017, Flagstaff, AZ 86011
Phone: (928)523-7182, Fax: (928)523-0296