Soil heating during burning of forest slash piles Matt Busse, Ken - - PowerPoint PPT Presentation

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Soil heating during burning of forest slash piles Matt Busse, Ken - - PowerPoint PPT Presentation

Mar 21, 2023 223 likes •531 views

Soil heating during burning of forest slash piles Matt Busse, Ken Hubbert, Steve Overby, Carol Shestak U.S. Department of Agriculture Pacific Southwest Research Station Science that makes a difference What conditions might lead to detrimental

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U.S. Department of Agriculture

Pacific Southwest Research Station

Science that makes a difference

Soil heating during burning of forest slash piles

Matt Busse, Ken Hubbert, Steve Overby, Carol Shestak

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What conditions might lead to detrimental changes in soils?

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Do pile burns act as short-term “hotspots” for nutrient release?

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Soil heating Post-burn soil quality Tahoe Basin inventory

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Step 1: Assess the range of pile conditions in the Tahoe Basin

75 inventory plots Pile size Fuel composition Pile density (#/acre) Ground cover Thinning intensity

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Pile size

Diameter (m)

1-2 2-3 3-4 4-5 5-6 6-7 >7

Number of piles

50 100 150 200 250 300

Inventory of current conditions

  • Wide variety of pile sizes and densities
  • Average diameter = 10 ft
  • Large piles not uncommon
  • Everything from small slash to large wood piles

Pile density

Piles ha-1

> 5 5

  • 9

9

  • 1

3 1 3

  • 1

7 1 7

  • 2

1 2 1

  • 2

5 2 5

  • 2

9

Number of plots

5 10 15 20 25

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3% cover 10% cover 20% cover 30% cover

How much ground is covered by piles within a unit?

Percent of land surface

  • 5

5

  • 1

1

  • 1

5 1 5

  • 2

2

  • 2

5 2 5

  • 3

3

  • 3

5

Number of plots

5 10 15 20 25

  • Average cover = 11%
  • One-fifth of the plots exceeded 15% cover
  • Ground cover = 3.75 + 0.223(stump BA)
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Intensive plots (29 piles)

Soil heating Soil and water chemistry Water repellency Soil physical properties Riparian and upland soils

Soil Quality Study

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Each pile was measured for

  • pile size
  • fuel mass by size class
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Measure heat pulse at 0, 5, 10, 30, 50 cm soil depths beneath pile center

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0 100 200 300 400 500 600 700 800 900

Temperature (oC)

Root and seed mortality Bacteria & Fungi death Release of inorganic N and P Soil C and N loss

What’s the big deal about soil heating?

Mineralogy changes Loss of hydrophobic compounds

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So how hot does the soil get?

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100 200 300 400 500 600 700 6 12 18 24 30 36 42 48 54 60 66 72 78

Temperature (oC) Time (hours)

Soil temperature profile at North Canyon, NV

(20 ft diam. pile)

0cm 5cm 10cm 30cm

Pile type I

  • Dominated by bolewood
  • Upper North Canyon
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100 200 300 400 500 600 700 6 12 18 24 30 36 42 48 54 60 66 72 78

Temperture (oC)

Time (hours)

Soil temperature profile at Sugar Pine SP

(20-ft diam. pile)

0cm 5cm 10cm 30cm

Pile type 2

  • Mix of all fuel sizes
  • Bliss SP; Sugar Pine SP
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100 200 300 400 500 600 700 6 12 18 24 30 36 42 48 Temperature (oC)

Time (hours)

Soil temperature profile at Old Mill

(10-ft diam. pile)

0cm 5cm 10cm 30cm

Pile type 3

  • Small diameter slash
  • Old Mill
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Pile diameter (ft) 6 8 10 12 14 16 18 20 22 24 Temperature (oC) 100 200 300 400 500 600 10 cm soil depth

Pile diameter (ft) 6 8 10 12 14 16 18 20 22 24 Temperature (oC) 100 200 300 400 500 600

Pile type 1 (wood) Pile type 2 Pile type 3

5 cm soil depth Pile Diameter (ft) 6 8 10 12 14 16 18 20 22 24 Temperature (oC) 100 200 300 400 500 600 30 cm soil depth

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How much spatial variability in heating is found beneath piles?

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0 30 60

Temperature (oC)

100 200 300 400 0 30 60 0 30 60 0 30 60

Time after ignition (hours)

0 30 60 0 30 60 0 30 60 0 30 60 0 30 60 Pile center Pile edge Pile edge 0.6 m

  • utside

0.6 m

  • utside

How much spatial variability in heating is found beneath piles?

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What about mopping up?

Time after ignition (hours)

10 20 30 40 50 60

Termperature (oC)

100 200 300 400 500 0 cm 5 cm 10 cm

Soil depth Mop up

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Soil Heating Summary

  • Moderate to severe heating was found in the surface 10 cm beneath piles
  • Fuel composition was the driving force
  • Pile size was important only for wood-dominated piles
  • Spatial variability was high - about one-half of the pile area reaches

maximum heating

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Post-burn soil quality

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Soil effects Nitrate Ammonium Total C, N, P N mineralization Nitrification Nutrients pH Fungi, bacteria Microbial biomass Respiration PLFA community structure Water infiltration Water repellency Bulk density Plant recovery Repeated sampling Water quality NO3, PO4 Surface and subsurface Downslope

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Fire Severity

Old Mill Bliss Sugar Pine Spooner1 Spooner2

% C 2 4 6 8

Pile burn Control

Post-burn soil quality (0-5 cm)

Soil C (24 months)

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Fire Severity

Old Mill Bliss Sugar Pine Spooner1 Spooner2

% N 0.0 0.1 0.2 0.3 0.4

Pile burn Control

Post-burn soil quality (0-5 cm)

Soil N (24 months)

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Fire Severity

Old Mill Bliss Sugar Pine Spooner1 Spooner2

m/g 200 400 600 800

Pile burn Control

Post-burn soil quality (0-5 cm)

Fungal hyphae (24 months)

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Fire Severity

Old Mill Bliss Sugar Pine Spooner1 Spooner2

mg/kg 1 2 3 4

Pile burn Control

Post-burn soil quality (0-5 cm)

Soil solution NO3 (24 months)

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SLIDE 27 Fire Severity Old Mill Bliss Sugar Pine Spooner1 Spooner2 % N 0.0 0.1 0.2 0.3 0.4 Pile burn Control

Post-burn soil quality (0-5 cm)

Fire Severity Old Mill Bliss Sugar Pine Spooner1 Spooner2 % N 0.0 0.1 0.2 0.3 0.4 Pile burn Control Fire Severity Old Mill Bliss Sugar Pine Spooner1 Spooner2 % N 0.0 0.1 0.2 0.3 0.4 Pile burn Control Fire Severity Old Mill Bliss Sugar Pine Spooner1 Spooner2 % N 0.0 0.1 0.2 0.3 0.4 Pile burn Control Fire Severity Old Mill Bliss Sugar Pine Spooner1 Spooner2 % N 0.0 0.1 0.2 0.3 0.4 Pile burn Control Fire Severity Old Mill Bliss Sugar Pine Spooner1 Spooner2 % N 0.0 0.1 0.2 0.3 0.4 Pile burn Control Fire Severity Old Mill Bliss Sugar Pine Spooner1 Spooner2 % N 0.0 0.1 0.2 0.3 0.4 Pile burn Control Fire Severity Old Mill Bliss Sugar Pine Spooner1 Spooner2 % N 0.0 0.1 0.2 0.3 0.4 Pile burn Control Fire Severity Old Mill Bliss Sugar Pine Spooner1 Spooner2 % N 0.0 0.1 0.2 0.3 0.4 Pile burn Control Fire Severity Old Mill Bliss Sugar Pine Spooner1 Spooner2 % N 0.0 0.1 0.2 0.3 0.4 Pile burn Control Fire Severity Old Mill Bliss Sugar Pine Spooner1 Spooner2 % N 0.0 0.1 0.2 0.3 0.4 Pile burn Control Fire Severity Old Mill Bliss Sugar Pine Spooner1 Spooner2 % N 0.0 0.1 0.2 0.3 0.4 Pile burn Control Fire Severity Old Mill Bliss Sugar Pine Spooner1 Spooner2 % N 0.0 0.1 0.2 0.3 0.4 Pile burn Control Fire Severity Old Mill Bliss Sugar Pine Spooner1 Spooner2 % N 0.0 0.1 0.2 0.3 0.4 Pile burn Control Fire Severity Old Mill Bliss Sugar Pine Spooner1 Spooner2 % N 0.0 0.1 0.2 0.3 0.4 Pile burn Control Fire Severity Old Mill Bliss Sugar Pine Spooner1 Spooner2 % N 0.0 0.1 0.2 0.3 0.4 Pile burn Control Fire Severity Old Mill Bliss Sugar Pine Spooner1 Spooner2 % N 0.0 0.1 0.2 0.3 0.4 Pile burn Control Fire Severity Old Mill Bliss Sugar Pine Spooner1 Spooner2 % N 0.0 0.1 0.2 0.3 0.4 Pile burn Control Fire Severity Old Mill Bliss Sugar Pine Spooner1 Spooner2 % N 0.0 0.1 0.2 0.3 0.4 Pile burn Control Fire Severity Old Mill Bliss Sugar Pine Spooner1 Spooner2 % N 0.0 0.1 0.2 0.3 0.4 Pile burn Control Fire Severity Old Mill Bliss Sugar Pine Spooner1 Spooner2 % N 0.0 0.1 0.2 0.3 0.4 Pile burn Control Fire Severity Old Mill Bliss Sugar Pine Spooner1 Spooner2 % N 0.0 0.1 0.2 0.3 0.4 Pile burn Control Fire Severity Old Mill Bliss Sugar Pine Spooner1 Spooner2 % N 0.0 0.1 0.2 0.3 0.4 Pile burn Control

Multivariate analyses

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Post-burn soil quality (0-5 cm)

515% 190% 90% 97% 92% 98% 114% 103% 42% 35% 87% 109% 20% 200% 107% Soil effects Nitrate Nitrification Ammonium N mineralization Total C Total N Total P pH Fungi hyphae Bacteria biomass Microbial biomass (SIR) Respiration PLFA community structure Water infiltration Water repellency Bulk density Percent of unburned control

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U.S. Department of Agriculture

Pacific Southwest Research Station

Science that makes a difference

Burning of hand piles will not result in extreme or extensive soil heating except when:

  • piles are dominated by large wood
  • piles occupy a high percentage of the ground surface

Expect short-term changes in certain soil properties. Are they a problem?