MONITORING POST-TREATMENT EFFECTIVENESS FOR PONDEROSA PINE FORESTS WITHIN THE GREATER FLAGSTAFF FORESTS PARTNERSHIP WILDLAND/URBAN INTERFACE

HALL, Patricia A. [1], Anne MOTTEK LUCAS [2], Stephen E. GATEWOOD [3], Anthony DICKENS [4] and Ryan RUSSART [4]INTRODUCTIONFire management throughout the Southwest has assumed a new focus - reactive wildfire suppression gradually being replaced by proactive fuel reduction and forest restoration. Land managers are thinning stands to various prescribed tree densities followed by prescribed ground fire to obtain the specific objectives of reduced wildfire hazard and increased forest health. Unfortunately, neither time nor has funding been available to revisit treated areas to assess the results of these activities. In 2006 the Greater Flagstaff Forests Partnership’s Monitoring and Research Team (GFFP MRT) received a grant from the National Forest Foundation to monitor post- treatment fire behavior. The GFFP MRT designed a project that evaluated treatment effects on fire behavior and wildlife suitability for seven different treatments applied by land managers within the 180,00 acre GFFP designated wildland/urban interface that surrounds the city of Flagstaff.

METHODSData Collection - Physical CharacteristicsSampling Design: Sampling grid (1 per stand)

(15) 0.1 acre plots for trees with dbh ≥ 5.0 inches

• species crown ratio• dbh tree height• height to crown base

(15) 0.01 acre plots centered in 0.1 acre plots for

live or dead stems dbh between 1.0 and 5.0 inches

60 meter spacing between plots and between grid

and vegetative edgesTreatments (see Table 1):

1 control 6 treatments

• Burn only Thin YP• Burn to thin Thin BA• Hand thin Fuel reduction

Replicates: 3 replicates per treatment

Data Collection Details: 1-year post-burn May – July 2006 H & K Consulting, L.L.C. Coconino Rural Environmental Corps Data entry into Microsoft EXCEL©: Sue Rodman

Data Collection Protocol: Stand characteristics: Stand structure,

composition and fuel loading

Common Stand Exam (USDA 2005) 50 foot Brown’s transect for down woody

material Fuel model (Anderson 1982, Scott and Burgan

2005) Canopy cover with 4 spherical densiometer

readings Stand physiognomy:

Slope Aspect

RESULTSPhysical Characteristics Summary (see Table 3)Stand Characteristics: Composition: dominated by ponderosa pine (Pinus ponderosa) with

inclusions of Gambel oak (Quercus gambelii), aspen (Populus tremuloides) and a number of juniper species (Juniperus sp.). Structure:

• Basal area: 32 – 168 ft2/ac• Canopy closure: 18 – 63%• Tree density: 28 – 242 trees/ac• Tree canopy:

• Tree height: 36.5 – 56.1 ft• Depth: 23.4 – 30.1 ft• Base height: 13.0 – 29.2 ft

Data Analyses - Habitat SuitabilityForest Ecosystem Restoration Analysis Program at Northern Arizona University (ForestERA) habitat model input: Abert squirrel (Sciurus aberti) density

Basal area Pronghorn antelope (Antilocapra

Americana) suitability Slope Canopy cover

Avian species richness Slope Basal area

Habitat Suitability Summary (see Table 6)Plants: Exotic species richness (see Figure 3): 0.40 – 3.71

species Non-native species found in every stand Highest in burn only treatment Lowest in control

Animals: Avian species richness (see Figure 4): 6.8 – 10.5

species Highest in burn to thin treatment Lowest in control

Pronghorn habitat suitability: 0.05 – 1.0 Highest in fuel reduction treatment Lowest in control

Abert squirrel density: 1.35 – 7.77 squirrels/acre Highest in control Lowest in fuel reduction treatment

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Figure 3. Mean Exotic Species Richness

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Figure 4. Mean Avian Species Richness

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Figure 1. Torching Index for Each Stand Within a Treatment

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Hand Thin

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Figure 2. Crowning Index for Each Stand Within a Treatment

Data Analyses - Fire BehaviorCalculations for NEXUS© runs: Canopy biomass Crown bulk density (Fulé et al. 2001) Aggregated fuel model Average canopy base height for lowest quintile of canopy base height values for stand Other NEXUS© inputs: Environmental conditions typical in pre- monsoon June (see Table 2)

Table 2. Environmental Conditions that Define the 97 Percentile for the Month of June Pre-monsoon

Metric Value

1 hour dead material moisture content 2.2%

10 hour dead material moisture content 3.0%

100 hour dead material moisture content 4.7%

Live herbaceous material moisture content 50%

Live woody material moisture content (range 30-300%)

120%

Wind speed 25 mph

Wind direction 225˚

Fire Behavior Summary (see Table 5)Fire characteristics (see Table 4 for definitions): Fire type: surface Percent of crown burned: 0 – 0.05 Rate of spread: 0.73 – 15.44 ft/min

Highest in control Lowest in burn to thin treatment

Flame length: 0.73 – 4.60 ft Varied little between treatments

Torching index: 32.50 – 1248.63 mph (see Figure 1) Highest in thin BA treatment Lowest in thin YP treatment

Crowning index: 31.57 – 123.57 mph (see Figure 2) Highest in fuel reduction treatment Lowest in control

DISCUSSIONPhysical Characteristics SummaryControl stands Highest crown bulk density and biomass Highest crown base height

Thin to burn Lowest crown base height Second highest tree density

Fuel reduction Lowest crown bulk density and biomass Lowest basal area Lowest tree density

Generally, crown bulk density and biomass are inversely related to thinning intensity. However, this pattern did not emerge from the data. The exhibited relationship may reflect the conditions that existed in the stands before treatment.

Treatment Fire Behavior SummaryAll treatments Ignition would result in surface fire Torching and crowning indices > 30 mph (highest wind gust in June)

Hand thin Passive crown fire and torching would result from ignition in 1 of 3 replicates under sustained winds of 30 mph1

Burn only & thin YP

Torching would result from ignition in 1 of 3 replicates under sustained winds of 30 mph1

Control

Torching would result from ignition in 1 of 3 replicates under sustained winds of 30 mph1

Passive crown fire would result from ignition in 2 of 3 replicates under sustained winds of 30 mph1

1 Local wildland fires in 1996 exhibited sustained winds of 30 mph and higher gusts.

Although torching and crowning indices generally depend upon crown base height, the highest indices corresponded to the smallest crown bulk density and crown biomass values.

Treatment Habitat Suitability SummaryControl Highest Abert squirrel densities Highest canopy closure, tree density and

basal area

Burn to thin & burn only Highest avian species richness Surface fuels removed by burning No trees removed

Fuel reduction Most suitable for pronghorn Lowest canopy closure

Burn only Highest exotic species richness

Table 1. Descriptions of Treatments Evaluated by GFFP MRT in 2006

Treatment

Abbreviation

Land Manager Treatment Description

Control No treatment

Burn Only USFS1 Prescribed ground fire only No thinning

Burn to Thin

AANG2 Moderate intensity surface fire

Hand Thin FFD3 Hand thinning from below up to 10” dbh

Thin YP USFS Mechanical thin from below within and around yellow pines (YP) and Gambel oaks (GO) to reduce fire hazard and resource competition Create openings where possible

Thin BA USFS Mechanically thin to 40-100 basal area (BA) to allow for dense clumps and openings Mechanically thin from below around yellow pines to reduce resource competition Create grassy openings in 10% of the area Mechanically thin from below around Gambel oaks to reduce fire hazard and resource competition

Fuel Reduction

USFS Mechanically thin from below to leave an even-aged stand of large trees with 40-80 residual BA Retain 30-40% canopy cover Use uneven spacing Leave clumps with very little crown interlock

1 USDA Forest Service, Coconino National Forest2 Arizona Army National Guard3 Flagstaff Fire Department

ASSUMPTIONS, CONDITIONS & LIMITATIONS Pre-treatment stand environmental conditions were not equivalent, therefore,

treatments cannot be directly compared. The results and analyses are preliminary.

Fuel model selection was based on stand conditions but aggregated for presentation of data.

The data collected represents a snap-shot in time. The data was collected in spring and early summer (May – July, 2006). The data was collected early post-treatment (1-2 years post-burn).

FUTURE ANALYSES Statistical comparisons within the control, burn only, thin BA and thin YP

treatments where pre-treatment stand conditions can be assumed equivalent

Using ForestERA models to apply the results to treatments implemented on broader landscapes southwest of Flagstaff

Comparisons of pre- and post-treatment stand exam data based on availability

LITERATURE CITED

Anderson, H. E. 1982. Aids to Determining Fuel Models for Estimating Fire Behavior. USDA Forest Service General Technical Report INT-122, 22p. Intermountain Forest and Range Experiment Station, Ogden, UT.

Fulé , P. Z., C. McHugh, T. A. Heinlein and W. W. Covington. 2001. Potential fire behavior is reduced following forest restoration treatments. In: Ponderosa pine ecosystems restoration and conservation: Steps toward stewardship. comps. R.K. Vance, W.W. Covington and C.B. Edminster, 28-35. Proceedings RMRS-22. US Forest Service, Rocky Mountain Research Station.

Scott, J. H. and R. E. Burgan. 2005. Standard Fire Behavior Fuel Models: A Comprehensive Set for Use with Rothermel’s Surface Fire Spread Model. USDA Forest Service General Technical Report RMRS-153, 80p. Rocky Mountain Research Station, Fort Collins, CO.

USFS. 2005. Common Field Exam Field guide Region 3, Version 1.7. USDA Forest Service Natural Resource Information System: Field Sampled Vegetation. 166p.

[1] H & K Consulting, L.L.C., 5937 E. Abbey Rd., Flagstaff, Arizona 86004; hkconsultingllc@yahoo.com[2] Social Research Laboratory, Northern Arizona University, P.O. Box 15301, Flagstaff, Arizona 86011; anne.mottek-lucas@nau.edu[3] Greater Flagstaff Forests Partnership, Inc., 1300 S. Milton Rd., Suite 218, Flagstaff, Arizona 86001; steveg@gffp.org[4] Coconino Rural Environmental Corps, 2625 E. King St., Flagstaff, Arizona 86004

Table 4. Definitions of Fire Behavior Metrics

Metric Units Definition

Fire type Type of fire – surface, passive, active

Percent crown burned

% The fraction of the crown that would be burned by the type of fire given above

Rate of spread Ft/min

The rate at which the given fire would spread through the stand

Flame length Ft The length of the flames produced in the fire

Torching index Mi/hr The wind speed required to initiate tree torching or passive crown fire behavior

Crowning index Mi/hr The wind speed required to support a crown fire spreading through the crown or active crown fire behavior

Table 5. Treatment Fire Behavior under June 97% Pre-monsoon Weather Conditions

Treatment FireType

% Crown burned

Rate of Spread(ft/min)

Flame Length

(ft)

TorchingIndex (mph)

CrowningIndex (mph)

Control Surface

0 15.44 4.60 40.67 31.57

Burn only Surface

0 13.51 4.07 63.30 50.07

Burn to thin Surface

0 0.73 0.77 593.10 42.60

Hand thin Surface

0 10.97 3.73 38.53 63.93

Thin YP Surface

0 14.53 4.47 32.50 51.70

Thin BA Surface

0 0.76 0.77 1248.63 62.57

Fuel reduction

Surface

0 2.08 1.63 432.13 123.57

Table 6. Treatment Habitat Suitability

Slope Canopy Avian Richness

Pronghorn Abert Squirrel

Exotic Richness

Treatment (%) Closure (%)

(# species) Suitability Density (#/ac)

(# species)

Control 16.6 62.5 6.8 0.05 7.77 0.40

Burn only 4.1 37.4 9.5 0.78 4.64 3.71

Burn to thin 5.0 41.2 10.5 0.73 4.53 0.49

Hand thin 8.7 40.3 8.5 0.60 3.53 1.64

Thin YP 10.6 47.5 8.9 0.52 4.66 1.53

Thin BA 6.7 38.0 8.5 0.78 4.21 2.42

Fuel reduction

4.9 17.9 8.5 1 1.35 2.84

Table 3. Treatment Physical Characteristics

Treatment FuelModels

BasalArea

(ft2/ac)

TreeDensity(trees/

ac)

CrownBase

Height

(ft)

TreeHeight

(ft)

Crown BulkDensity(kg/m3)

CrownBiomass(tons/ac)

Control 2/TU1 168.0 242.2 29.2 52.6 0.0842 5.53

Burn only 2/TU1 101.8 100.4 25.4 53.9 0.0366 2.85

Burn to thin 9/TL1 99.6 160.2 13.0 36.5 0.0314 2.55

Hand thin 2/TU1 78.3 81.6 17.5 44.2 0.0530 2.64

Thin YP 2/TU1 102.2 100.7 24.5 52.1 0.0421 2.28

Thin BA 9/TU1 92.9 85.6 26.0 56.1 0.0425 3.47

Fuel reduction

8/NB9 32.4 28.2 19.0 46.6 0.0119 1.04

Calculations for NEXUS© runs: Canopy biomass: 1.04 – 5.53

tons/acre Crown bulk density: 0.0119 – 0.0842

kg/m3 Aggregated fuel model:

Anderson 1982: 2, 8 & 9 Scott and Burgan 2005: TU1, TL1

& NB9 Average canopy base height for

lowest quintile: 13.0 – 29.2 ft

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RESULTS (cont’d)

Control

Fuel Reduction

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