Effects of Shredding Utah Juniper on Fuel Characteristics · Effects of Mechanically Shredding Utah Juniper on Fuel Characteristics ... – Converts live fuels to dead fuels ... –

Effects of Mechanically Shredding Utah Juniper on Fuel Characteristics

Kert Young and Bruce Roundy

Outline

1. Introduce SageSTEP2. Ecological Concerns3. Experimental Design4. Fuel Measurement Methods5. Objectives6. Results7. Conclusions8. Implications

SageSTEPSagebrush Steppe Treatment Evaluation Project

A collaborative research project among:

Vegetation/Fuels

Soils

Fully Interdisciplinary Approach

Wildlife

Sociology

Economics

Hydrology

Pinyon-Juniper Encroachment

Shoshone Mountains, Nevada

Photos by R. Tausch

1973

2005

Land Management Treatments:Woodland Experiment

Prescribed fire Chainsaw Cutting

Shred(Utah only)

UntreatedControl

Wildfire

Shredded Fuels

ShredTreatment

“The Concern”

©John M. Randall / Nature Conservancy ©C. Kelley / WA Plant Materials Center

Invasive Grasses Native Grasses

+

Restoration PathwayDegradation Pathway

Juniper Mechanical Shredding Shredded Residue

Hypothesis

+

Shredded juniperfuels

Soil

IncreasedSoil Organic CSoil C:N ratio 

IncreasedDecomposition by soil microorganisms

DecreasedSoil N availability

DecreasedCheatgrass  success

Literature• Cheatgrass invasion into PJ helps to enable crown fires and convert 

many PJ woodlands into annual grasslands (Billings 1994, West 2000) 

• Cheatgrass dominance after severe wildfire leads to shorter fire return intervals excluding many perennial plant species (Billings 1994, West and Young 2000, Young 1991, Young and Evans 1973)

• High density PJ woodlands are expected to increase to 75% within the next 50 years (Johnson and Miller 2006, Miller et al. 2008)

• Canopy cover of 35% or greater is capable of supporting crown fire (Bryant et al. 1983) 

Experimental Design• 4 research locations

– Stansbury, Onaqui, Scipio,        Greenville

• 15 subplots– 30 x 33 m2

• Tree Dominance– Tree cover / perennial cover– Low: Herbs & shrubs dominant– High: Trees dominant– Covariate

• Statistics– Mixed Model Analysis of Covariance(SAS Institute Inc., version 9.2, Cary, NC)

Utah

Tree DominanceSuccession Without Natural Fire Frequency

Northern Great Basin sagebrush steppe

• Low– Dominated by grass and shrubs

• High– Dominated by trees

Succession without natural 

fire cycle

High – Tree Cover Ratio

Mechanical Shredding and Sampling DatesLocation Pretreatment Treatment Posttreatment

Onaqui 2006 Nov 2006 Summer 2007

Greenville,Scipio, 

Stansbury2006 Nov 2007 Summer 2008

Tree SpeciesUtah Juniper ‐ all locations

Two‐needle Pinyon ‐ Greenville

Diameter

Height

Base‐Canopy Height

• Tree allometry– pre‐treatment– standing trees

• tree height• base canopy height• widest diameter• perpendicular diameter

Pre‐treatment Standing Tree Fuel Measurements

Tausch, R. J. 2009. A structurally based analytic model for estimation of biomass and fuel loads of woodland trees.

Post‐treatment Surface Tree Fuel Measurements

Planar‐intersect                    vs                  Quadrat(Brown 1974, Brown et al. 1982)

• Treatments ‐‐ Untreated, Cut‐and‐drop, Burn

• Treatment‐‐ Shred

Objectives

1. Can shredded fuel depth estimate fuel loads using the quadrat method?– Save field time while maintaining accuracy?

1. Can shredded fuel depth estimate fuel loads using the quadrat method?– Save field time while maintaining accuracy?

Shredded Fuels Depth to Fuel Loads

0

10000

20000

30000

40000

Shredded Depth (cm)0 1 2 3 4

Legend Biomass by Depth Regression95% CI's

Total Shredded Fuels

(kg/ha)

Adj R2= .92y = 62 + 9082 x

Objectives

2. How much surface area is directly affected by shredded juniper?

2. How much surface area is directly affected by shredded juniper?

0

10

20

30

40

50

60

5 15 25 35 45 55 65 75 85 95

Cover (%)

Tree cover / Total perennial cover (%)

1‐yr Post‐treatment surface tree fuel cover

ShredCut‐and‐Drop

Objectives

3. What is the bulk density of shredded juniper?3. What is the bulk density of shredded juniper?

0

10

20

30

40

50

60

70

80

5 15 25 35 45 55 65 75 85 95

Bulk Density (kg/m3)

Tree Cover / Total Perennial cover (%)

1‐yr post‐treatment shredded juniper bulk density

Shred

Objectives

4. How does treatment alter fuel loads by size class?4. How does treatment alter fuel loads by size class?

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

18,000

5 15 25 35 45 55 65 75 85 95

Fuels(kg/ha)

Tree cover / Total perennial cover

Burn 1‐hr Untreat 1‐hr Shred 1‐hr Cut 1‐hrBurn 10‐hr Untreat 10‐hr Shred 10‐hr Cut 10‐hrBurn 100‐hr Untreat 100‐hr Shred 100‐hr Cut 100‐hrBurn 1000‐hr Untreat 1000‐hr Shred 1000‐hr Cut 1000‐hr

Pre‐treatment standing and surface juniper fuelsComparing size classes within treatment

1 and 1000‐hr size classes

100‐hr size class

10‐hr size class

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

18,000

5 15 25 35 45 55 65 75 85 95

Fuels(kg/ha)

Tree cover / Total perennial cover

Burn 1‐hr Untreat 1‐hr Shred 1‐hr Cut 1‐hrBurn 10‐hr Untreat 10‐hr Shred 10‐hr Cut 10‐hrBurn 100‐hr Untreat 100‐hr Shred 100‐hr Cut 100‐hrBurn 1000‐hr Untreat 1000‐hr Shred 1000‐hr Cut 1000‐hr

1 and 1000‐hr size classes

10 and 100‐hr size classes

Pre‐treatment standing and surface juniperComparing size classes across treatments

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

5 15 25 35 45 55 65 75 85 95

Fuels(kg/ha)

Tree cover / Total perennial cover (%)

Cut 1‐hr Cut 10‐hr Cut 100‐hr Cut 1000‐hrUntreat 10‐hr Untreat 100‐hr Burn 10‐hr Burn 100‐hrShred 1‐hr Shred 10‐hr Shred 100‐hr

Post‐treatment surface juniper fuels by treatment and size class

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

5 15 25 35 45 55 65 75 85 95

Fuels(kg/ha)

Tree Cover / Total perennial cover (%)

Pre‐Treat 1‐hr 1‐yr Post‐Treat 1‐hrPre‐Treat 10‐hr 1‐yr Post‐Treat 10‐hrPre‐Treat 100‐hr 1‐yr Post‐Treat 100‐hrPre‐Treat 1000‐hr

Pre‐ vs Post‐shredded juniper fuels by size class

Objectives

5. Effect of shredded fuels on soil N availability?5. Effect of shredded fuels on soil N availability?

0

100

200

300

400

500

600

N Supply Rate (µg/ 10 cm2/4 months)

Microsite‐Plots

Preliminary ‐ Soil N Supply Rate ‐ PRS ResinsUntreated versus Shredded Juniper

Untreated Control Mechanically Shredded

Objectives

6. Effect of shredded fuels on cheatgrass versus bluebunch wheatgrass emergence?

6. Effect of shredded fuels on cheatgrass versus bluebunch wheatgrass emergence?

Response to “The Concern”

0

10

20

30

40

50

60

Interspace Litter No Litter orResidue

Interspace Litter No Litter orResidue

Residue

Microsite‐plots

Blueblunch Cheatgrass

Untreated Control Mechanically Shredded

Preliminary ‐ Percent Emergence between Species

No Litter No Litter Shreds

• Will invasive or native grasses dominate following mechanical shredding of juniper?

Emergence%

Response to Hypothesis

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Shredded juniperfuels

Soil

IncreasedSoil Organic CSoil C:N ratio 

IncreasedDecomposition by soil microorganisms

DecreasedSoil N availabilityCheatgrass success

Conclusions• Shredded juniper depth versus fuel load

– Shredded fuel depth can estimate fuel loads

• Shredding juniper – Converts canopy fuels to surface fuels

– Reduces fuel size

– Fuels remain on site

• Cut‐and‐drop – Converts live fuels to dead fuels 

– No change in fuel loads or size classes

– Fuels remain on site

• Burning – reduces fuel loads

Conclusions• Soil and plant responses to shredding juniper (preliminary)– Interspace soil and soil under canopy litter 

• Increased soil N availability

– Under shredded juniper alone• No significant reduction in soil N availability

– Overall• Bluebunch (Anatone) had ~30% greater emergence than cheatgrass

©John M. Randall / Nature Conservancy ©C. Kelley / WA Plant Materials Center

Invasive Grasses Native Grasses

+

Restoration PathwayDegradation Pathway

Vegetation Implications

Juniper Mechanical Shredding Shredded Residue

Shredding Juniper Implications• Proactive juniper control is better than reactive fire suppression• Control invasive species early before desired plants are 

weakened or lost• Shredding juniper treatment

– Hope for bluebunch– Surface fire is easier to control than crown fire– Optional – post‐shredding, follow‐up with cool season prescribed fire– Not enough reduction in soil N availability to stop cheatgrass

• Next step– Develop shredded juniper fire behavior models

For more information…

www.sagestep.org