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Joint Fire Science / Red Mountain Mastication Study

Study Site Description

Red Mountain is a 24-year-old ponderosa pine plantation, planted after a 2,500 acre 1970 wildfire. The study area is located at 5,200 to 6,600 feet in Greenhorn Ranger District of the Sequoia National Forest. The site is productive, with pines that are approximately 30 feet high and in some areas form a nearly continuous canopy. Oak, white fir, and incense cedar also grow in patches throughout the plantation. The mean annual precipitation in this area averaged 15 to 20 inches, falling primarily as rain, although snow can cover the upper parts for up to 4 months per year.

Site Map

Project Objectives

Objective 1. Determine the effectiveness of using mastication alone or mastication in combination with prescribed burning to meet resources objectives while modifying wildfire behavior and improving fire suppression opportunities under 80th, 90th, and 97th percentile weather conditions. Hypotheses associated with this objective fall into two groups:

  1. Fuel Conditions: How does mastication alone and with prescribed burning affect fuel conditions such as amount, size, and configuration compared to the control?
    1. Hypotheses
    2. Mastication will reduce abundance of the 1000 and 100 hour fuels and increase the 10 and 1 hour fuels.
    3. According to model prediction, mastication combined with prescribed burning will result in shorter flame lengths and lower fire intensities of shorter duration compared to predictions for unburned, masticated units and unmasticated sites.
    4. Mastication will reduce fuel bed depth.
  2. Fire Behavior: Determine if mastication alone is sufficent to significantly reduce wildfire behavior under 80th, 90th , and 97th percentile weather conditions. This question will be addressed through a series of hypotheses on fire behavior characteristics, including rate of spread, fire type, fire intensity and resistance to control:
    1. Hypotheses
    2. Mastication alone is enough to reduce fire behavior model predictions of rate of spread compared to model predictions for unmasticated sites.
    3. According to model prediction, mastication combined with prescribed burning will result in shorter flame lengths and lower fire intensities of shorter duration compared to predictions for unburned, masticated units and unmasticated sites.
    4. Mastication with follow-up underburning will provide the greatest decrease in firefighting resistance to control.

Objective 2. Tree Mortality: Through this study, AMSET will quantify effects of mastication and mastication with prescribed burn treatments on tree mortality. This issue will be addressed through the following hypotheses:

  1. Fire-related mortality will be higher than targeted resource objectives in masticated units.
  2. Pulling masticated slash away from boles will significantly decrease prescribed burn related tree mortality.

Timeline

First Year
(Summer/Fall 2005)

  1. Set up experimental plots.
  2. Collected pre-treatment data.
  3. Implemented mastication treatments on experimental plots.

Second Year
(Summer/Fall 2006—Winter 2006/2007)

  1. Collected post-mastication data on masticated plots.
  2. Gathered fuel samples to aid in masticated fuel model definition.

Third Year
(Fall 2007)

  1. Completed prescribed fire treatments.
  2. Gathered fire behavior data.

Fourth Year
(Summer 2008—Winter 2008/2009)

  1. Collected final post-treatment data on all plots.
  2. Currently analyzing data and preparing reports and presentations.

Fuels and Tree Mortality - Data Collection

Measurements characterizing fuel conditions will be used to address our hypotheses and will also be used in order to develop custom fuel models for mastication. These custom models will be used to compare predicted fire behavior under a range of weather conditions and will be provided to managers in the mastication guide.

Subplot size and location: Four subplots will be randomly located in each 5 acre treatment using ARC GIS. Subplots will not be placed near the edges of the treatment units, allowing for a 3 meter buffer from the edge to reduce effects of treatment initiation. Based on an extensive fuels treatment monitoring data set across three National Forests in the northern Sierra Nevada, this is the calculated number of plots per stand needed to obtain mean estimates of surface fuel loadings within 20% and a confidence level of 80%. Based on this sampling analysis, we concluded that six plots per stand are optimal for treated stands that are variable natural stands. Our sites are more uniform, in a plantation and therefore, we expect that four sub-plots will more than adequately capture variability within each plot, especially since they will encompass a sample of 20% of the treated areas. Subplots will be 1,000 m2, as defined by a radius extending 17.85 m from the subplot center. Fuels data will be collected three times: once before any treatments, once following all mechanical treatments, and once following controlled burns.

Crown Fuels: All living and dead trees will be tagged with sequentially numbered brass tags nailed in at dbh prior to any treatments. For all live trees >15cm dbh, the following information will be collected:

  1. tag number, species, dbh (cm)
  2. alive (y/n)
  3. height to live crown
  4. total tree height (m)

Tree damage will also be noted. For snags, information collected will be:

  1. tag number
  2. species
  3. dbh
  4. total tree height
  5. decay class ( 1 thru 5 )

Following mastication and controlled burns the following will be collected:

  1. height to live crown
  2. char height (on the bole)
  3. proportion of circumference of bole charred
  4. crown scorch height (foliage brown but not consumed)
  5. torch height (foliage consumed)
  6. tree status (dead or alive)

For smaller trees (2.5 to <15 cm dbh and > 1.37 m in height) and seedlings, a smaller circle will be sampled that is centered at a random point along the perimeter of the subplot. A circle with a 8.92 m radius will then be defined from this point. All pole size trees will be tagged with numbered brass tags and the same set of information will be collected on these trees as from the trees that are >15 cm dbh. Information on seedling and canopy cover will be collected from a 3.99 m radius circle centered at the pole-tree plot center. In this area, the following information will be recorded: seedling species, alive (y/n), height class (<15cm = 15, <30cm = 30, <60cm = 60, <100cm = 100, <200cm = 200, <300cm = 300, etc.).

Surface Fuels: Brown’s planer intercept method will be used to measure surface fuels (Brown 1974). From the subplot center, one 50 foot transect will be placed along a randomly selected bearing. Beginning and ending of transects will be marked with rebar to ensure exact placement pre- and post-treatment. Transects will be photographed, and the slope and bearing recorded.

Masticated Material, Litter and Duff Samples: No generalized fuel models for masticated materials are currently available. In order to aid in estimating fuel loadings from mastication bulk density samples will be taken. Two randomly located 30x30cm quadrats within each treatment block will be collected. Litter, masticated material and duff layers will be separately measured and collected. Samples will be floated to remove dirt and rock, placed in bags, air dried, then oven-dried at 70oC for 48 hours and weighed. Equations will be derived to calculate masticated material fuel loading based on depth.

Live Understory Fuels: Biomass of live understory fuels, including shrubs, forbs and graminoids, will be estimated using Behave Fuel Subsystem NEWMDL program v 2.0 (Burgan and Rothermel 1984). Life form, density class, depth and cover are required inputs. A belt transect will be established along the Brown’s planar intercept that is 50 feet long (same as intercept) and 1 meter wide. Within that belt transect we will classify and record shrub, herb, and grass cover using cover classes (1=0-5%, 2=6-25%, 3 =26-50%, 4= 51-75%, 5 = 76-95%, 6 = 96-100%), percent dead, and average height (cm), and dominant species. The Burgan and Rothermel (1984) lifeform and density class will be assigned to each understory component and fuel loading calculated according to their algorithms.

Tree Mortality: Post-burn mortality, and crown condition will be assessed by measuring tree survival and crown condition in the subplots, at one year and two years following the prescribed fire treatment. We will compare mortality and crown condition between masticated plots burned with and without the mitigation treatment of pulling material away from the boles and root zone. In addition, we will gather fire behavior data soil surface temperature maximums and duration near trees, as described in the Fire Behavior section.

Prescribed Burn Treatment

Red Mountain Prescribed Burn 2007

Weather, fire operations and research efforts came together on December 5th and 6th, 2007 to accomplish the prescribed burn treatments on the Red Mountain Mastication Study units. Scott Williams, the Burn Boss, along with the Fulton Hotshots, the Cobra 5 handcrew, Engines 42, 43, 44 and 47 and other fire personnel completed prescribed burns on four research units in two days. Due to the expertise of the firing and holding operations, four disjunct burns in timber and masticated fuels were completed safely within a short window before season-ending precipitation.

Fire operations worked seamlessly with the research crew from AMSET, who set up fire behavior equipment on plots days to hours before each burn. The Breckenridge handcrew lead burn unit preparation efforts during the last two fire seasons and participated in leadership and burner roles. Due to the technical nature of the fire behavior equipment, setup requires careful preparation and organized logistics. The AMSET Fire Behavior Assessment Team (FBAT) installed 16 sets of fire behavior equipment the day before the first burns, and 12 sets before the second day of burning, surpassing previous rates of equipment installation.

Weather

The Red Mountain burn was accomplished during a narrow window of favorable weather between Dec 5th and 6th, 2007, before the passage of a front. Two of the research units were burned the first day and two were burned the second day. On the first day, winds were 1-5 miles per hour and variable in direction. Temperatures ranged from 47 to 58 F and relative humidities were in the lower 30’s in the morning to upper 50’s by the end of the day. The first day there was little to no cloud cover

The second day, a front moved through, bringing wind changes and precipitation. Mid-morning temperatures were in the 50's and dropped to the lower 40's by the afternoon. Winds directions were variable in the morning and from the SW in the afternoon. Windspeeds were 3-8 during the day, with gusts as high as 13 in the afternoon. Relative humidities were in the 40's in the morning, then rose in the afternoon as precipitation began. The last burn was completed during a wetting rain which turned to snow over night.

Fire Behavior

Backing fires were generally used, meaning that fires were lit so that they would spread downhill and/or against the wind, keeping the flame heights and rates of spread lower. The technique of "spot-firing" was often used to maintain less intense fire behavior. By initiating fire in small dots across strip of a burn unit, the dots slowly spread and merge together, without picking up a head of steam as a strip of fire might. Isolated torching did occur occasionally, but generally flame heights were 1-4 feet. Smoldering lasted from several hours in lighter fuels such as grass and pine litter to about 24 hours in heavier masticated fuels.

What's Next?

Fire behavior gear was retrieved after prescribed burns were completed and data was downloaded from equipment. Due to heavy snowfall immediately after the prescribed burn, post-burn data will be collected in the spring. Fire behavior data will be analyzed alongside pre and post-burn fuel measurements and tree mortality to aid in resource management decisions regarding future use of combined mastication and prescribed fire treatments in this fuel type.

Acknowledgements

Thanks to all fire resources who helped accomplish the burn despite long hours, chilling rain and snow. Thanks also go to the Sequoia National Forest personnel who supported the burn and research operations. Thanks go to AMSET employees and short-term detailers who helped with the fire behavior research.