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A project funded by the Joint Fire Science Program

Thinning Experiment

Study Design

Each combination of 4 fuel treatments will be applied to 8 replicate treatment plots n=32 total. Treatment plots will be 20 acres (8.1 ha,
285 X 285 m). Treatments will be applied in the summer/fall of 2002 and 2003.

The sampling unit will consist of a 20 x 50m Modified Whittaker plot (mod-whit plot) , centered over a 5 x 30m Fire Management Handbook (FMH) brush belt transect. Each of the 32 treatment plots will have three sampling units randomly located within them, such that the edge of each sampling unit will be >30m from the plot edge.

Thinning Treatments

Cut

• Every 4 post-settlement trees encountered in the treatment plot will be treated, leaving every 5th post-settlement tree
• Treatment will be accomplished by cutting selected Class 1 (youngest) trees at ground level using lopping shears, and cutting selected Class 2 and 3 trees at ground level using a chainsaw.
• Trees will be left were they fall
  

Cut, Limb, and Scatter

• Every 4 post-settlement tree encountered in the treatment plot will be thinned, leaving every 5th post-settlement tree


• Treatment will be accomplished by cutting selected Class 1 (youngest) trees at ground level using lopping shears, and cutting selected Class 2 and 3 trees at ground level using a chainsaw


• Class 2 and 3 cut trees will be limbed to manageable lengths then scattered evenly across the site, except under the driplines of uncut trees

• A 15 foot no chemical treatment buffer will be left around old-growth trees due to concerns for chemical soil “drift” within the root zone of untreated trees. This will leave many untreated post-settlement trees that are growing within the canopy drip zone of the class 4 leave trees. We estimate that these untreated Class 1-3 trees will constitute the 20% of the target trees that are prescribed to leave


• Every post-settlement piñon and juniper tree located outside of the 15 foot buffer around old-growth trees will be treated, including seedlings and saplings growing within non-target shrubs.

15% Tordon 22K will be batch mixed at 3 gallon increments directly into SP-3 backpack sprayers at a rate of 24 ounces of 15% Tordon 22K per gallon of water with 1 ounce of Blaze-on blue dye and 1 milliliter of Kinetic non-ionic surfactant

• The herbicide mixture will be applied as a streamline basal spray, covering both the base of trees and the soil around them


• Treatment grids will include 6 sprayers spread approximately 30 to 50 feet apart (depending on tree density) along either the north or south perimeter line. The blue dye spray line from the previous application sweep will be followed by the inside applicator while the outside applicator will follow a north-south compass bearing to keep directional alignment. The remaining 4 inside applicators will intersperse between the two outside applicators

Sampling Schedule

Pre-Treatment - (2002-2003)

5 X 30 meter brush belt transects

• Density of woody perennial plants (spring-summer)
• Cover of woody perennial plants (spring-summer)
• Density of herbaceous plants (spring-summer)
• Cover of herbaceous plants (spring-summer)
  

Post-Treatment - (2004-2006)

5 X 30 meter brush belt transects

• Density of woody perennial plants (spring-summer)
• Cover of woody perennial plants (spring-summer)
• Density of herbaceous plants (spring-summer)
• Cover of herbaceous plants (spring-summer)
• Seedbank density and diversity (late summer)

20 X 50 meter mod-whit plots

• Plant diversity (spring)

• Fuel measurements (summer)

Thinning and Seeding Experiment

Study Design

Each combination of the 2 thinning and 3 seeding treatments will be applied to 6 replicate treatment plots (n=36 total). Treatment plots will be 2.7 acres (1.1 ha, 90 X 120m). Treatments will be applied in the summer/fall 2003 and 2004.

The sampling unit will consist of a 5 X 30m Fire Management Handbook (FMH) brush belt transect. Each of the 36 treatment plots will have three sampling units randomly located within them, such that the edge of each sampling unit will be 20m from the plot edge, and 10m from each other.

Thinning Treatments

Cut, Limb, and Scatter

• Every 4 post-settlement tree encountered in the treatment plot will be thinned, leaving every 5th post-settlement tree
• Treatment will be accomplished by cutting selected Class 1 (youngest) trees at ground level using lopping shears, and cutting selected Class 2 and 3 trees at ground level using a chainsaw
• Class 2 and 3 cut trees will be limbed to manageable lengths then scattered evenly across the site, except under the driplines of uncut trees

Seeding Treatments

Hand Seeded

• Seed mix will consist of bottlebrush squirreltail (Elymus elymoides spp. elymoides) @ 3 pounds per acre and blue grama (Bouteloua gracilis) @ 2 pounds per acre, the two common perennial grasses at the study site. Seed will be biotypes local to southern Utah and northern Arizona


• Seed will be broadcast using handheld applicator equipment


• Treatment grids similar to those described for herbicide application will be followed to ensure even seed application


• No raking or other form of soil scarification will occur to prevent disturbance of cultural resources in the area. Minimizing ground disturbance may also provide less potential habitat for weed species to invade the treatment sites


• Weed seed germination and percent live seed testing will be conducted by the seed company and the Lake Mead NRA nursery from batch samples provided prior to purchasing the bulk of the seed

Sampling Schedule

Pre-Treatment - (2004)

5 X 30 meter brush belt transects

• Density of woody perennial plants (spring-summer)
• Cover of woody perennial plants (spring-summer)
• Density of herbaceous plants (spring-summer)
• Cover of herbaceous plants (spring-summer)
Seedbank Density and Diversity (late summer)

Post-Treatment - (2005-2006)

5 X 30 meter brush belt transects

• Density of woody perennial plants (spring-summer)
• Cover of woody perennial plants (spring-summer)
• Density of herbaceous plants (spring-summer)
• Cover of herbaceous plants (spring-summer)


• Seedbank density and diversity (late summer)

Sampling Methods

FMH Brush Belt Transect
Density of woody perennial plants (trees, shrubs, and cacti) will be measured in the 5x30m belt transect centered within each mod-whit plot. Each individual having >50% of its rooted base within the belt transect will be counted. Data will be recorded by species and age class. Age class of each individual will be identified as either dead, immature-seedling, resprout, or mature-adult.

Cover of woody perennial plants (trees, shrubs, and cacti), and cover of bare mineral soil, will be measured by line intercept, using the two 30m sides of the brush belt transect as subsamples. Data will be recorded by species and age class.

Density of herbaceous plants will be collected within five 1m² subplots along the two 30m sides of the brush belt transect as subsamples. Herbaceous plants will be counted by species for each frame, separating live and dead individuals.

Cover of herbaceous plants will be measured by the point-intercept method, using the two 30m sides of of the brush belt transect as subsamples. Starting at the end of each transect, a 0.25inch diameter sampling rod (a rigid plumb bob), graduated in decimeters, will be lowered gently so that the sampling rod is plumb to the ground (on slopes this will not be perpendicular to the ground), every 30 cm along the transect line. Since the transect length is 30 m, there will be 100 points from 30 to 3,000 cm. The height at which each species touches the sampling rod will be recorded, tallest to shortest. If the rod fails to intercept any vegetation, the substrate will be recorded (bare soil, rock, forest litter, etc.).

Seedbank density and diversity will be measured from a single composited soil sample for each of the five 1m² herbaceous plant subplots (described above) by pooling four sub-samples collected just outside each corner of the subplot. All soils will be collected using a 5cm diameter x 5cm deep (volume = 98cm³) core. Soil seedbanks will be assayed by growing them out in a greenhousee and counting the number of seedlings for each species. The methods are adapted from Brenchley and Warington (1939), later modified by Young and Evans (1975).

Mod-Whit Plot
Plant diversity will be calculated at multiple scales within the 20 x 50m mod-whit plot. The effects of disturbance on plant diversity can vary among spatial scales. For example, the effects on plant community diversity due to fire and grazing can vary between 1 and 1,000m² scales. It is possible that similar variation will occur among management treatment in pinon-juniper woodland, warranting the use of the spatially nested modified-Whittaker plots in this study. Plant species richness will be measured for all species recorded at 1, 10, 100, and 1,000m² scales. Species evenness will be measured among ten 1-m (0.5 x 2 m) sub-plots within each 1,000m² plot. In addition, seedbank species richness and evenness will be measured from seedbank density assays at the 1m² scale.

Fuelbed Measurements
Representative trees, shrubs, and grasses will be randomly chosen inside each mod-whit plot to calculate biomass. These data will be augmented using Taush’s allometric model to calculate piñon fuel classes and biomass. Three fuels transects parallel to the long axis of each mod-whit plot will be established to estimate downed woody debris.