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TRANSCRIPT
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
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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