jim innes and malcolm north usda-psw sierra nevada research center davis, california
DESCRIPTION
Effect of silvicultural and prescribed fire treatments on coarse woody debris dynamics in a sierran old growth mixed-conifer forest. Jim Innes and Malcolm North USDA-PSW Sierra Nevada Research Center Davis, California. Coarse Woody Debris (CWD) in the Sierra Nevada. - PowerPoint PPT PresentationTRANSCRIPT
Effect of silvicultural and Effect of silvicultural and prescribed fire treatments on prescribed fire treatments on
coarse woody debris dynamics in coarse woody debris dynamics in a sierran old growth mixed-conifer a sierran old growth mixed-conifer
forest.forest.
Jim Innes and Malcolm NorthUSDA-PSW Sierra Nevada Research
Center Davis, California
Coarse Woody Debris (CWD) in the Sierra Nevada
• Important habitat for small to mid-sized mammals particularly during snow cover.
• Long duration fire fuels.• Knowledge gap concerning
management/restoration guidelines for CWD in Sierra Nevada.– Guidelines are based on fire
suppressed forest structures (for example, The CASPO Report).
Study Site – Teakettle Experimental Forest
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18, 4 hectare plots
• Patterson Mountain, California
• Old growth mixed- conifer forest.
• 2000 m elevation.
Methods• Full Factorial Experiment with 3 replicates:
– Prescribed fire and 2 levels of cutting:• Shelterwood (Low thinning) > 25 cm leaving 22 trees per hectare.
• California spotted owl cut (CASPO) harvest from 25 cm to 76 cm.
• Here we are using a plot from each treatment and 3 controls.
• Mapped all logs > 30 cm small-end-diameter within each 4 ha plot.
• Decay classes 1 – 4. • Analysis: t-test and Ripley’s K function, alpha = .05
HypothesesThin no burn treatment:
– Increase the per hectare plot density, volume and mass of CWD.
– Decrease mean piece large-end-diameter and volume.
Burning in combination with thinning:
– Decrease per hectare plot density, volume and mass of CWD.
– Decrease mean piece-volume and mean piece large-end-diameter.
Burning alone.
– Increase mean piece-volume and mean piece large-end-diameter.
Results - Thin no burn treatment
1. Will increase the per hectare plot density,
– Yes, density 39% in the CASPO and 48 % in the shelterwood.
volume (m3 ha-1) and mass (Mt ha-1) of CWD.
– No, CASPO volume 10% and Mass 4%.
– Shelterwood volume 25% and mass 9 % .
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Densityha
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Density ha Vol m3/ ha Mass Mt/ha
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Results - Thin no burn treatment
2. Thinning alone will decrease mean piece large-end-diameter (cm) and volume (m3) .
– CASPO mean piece large-end-diameter 21% (16 cm, (p=0.0001).
– Mean piece volume 44% (2.1 m3, p=0.004).
– Shelterwood mean piece large-end-diameter 19% (13.4 cm, p=0.0001).
– Mean piece volume 60% (2.9 m3, p=0.0001).
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Mean large-end-diameter cm
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Results - Thin and burn treatment1. Decrease in per hectare plot
density, volume (m3 ha-1) and mass (Mt ha-1).
– CASPO Density 38%, volume 70% and mass 69%.
– Shelterwood by 26%, volume 39% and mass 19%.
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Results - Thin and burn treatment
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Mean large-end-diameter cm
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2. Decrease mean piece-volume (m3) and mean piece large-end-diameter (cm).
•CASPO 60% mean piece-volume (2.2 m3, P=.0001).• 29% mean piece large-end-diameter (22.4 cm, p=.0001).
•Shelterwood 56% mean piece-volume (3.2 m3, P=.007). • 24% Mean piece large-end-diameter (20.5 cm, p=.0001).
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Results – Burn only treatment
• Increase mean piece volume (m3) and mean piece large-end-diameter (cm).– Mean piece volume by
50% (2.5 m3, p=0.003) and mean piece large-end-diameter 12% (8 cm, p=.03).
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Decay Dynamics
• Cut only• in lower decay classes
due to logging slash.
• Cut and burn• in lower decay classes
from slash and in higher decay class due to removal by fire.
• Burn plots - higher decay
classes due to removal by fire.
Spatial Patterns – Control plots
• Variability among plots.
• Control plot 2 random clustering possibly due to a spot fire in 1917.
- Suggests past fires may produce long lasting legacy patterns.
Control 1
Control 3
Control 2Clustered
Random
Regular
Spatial Patterns – Treated plots Shelterwood
Unburned shelterwood
Burn only pretreatment Burn only post-treatment
Pretreatment
Burned shelterwoodPretreatment
CASPO
Pretreatment Unburned CASPO
Burned CASPOPretreatment
Clustered
Random
Regular
• No trend in spatial patterns with treatments.• or in significance of clustering with treatment.
Summary• Cut and cut and burn treatments –
1. Change in quality of CWD from fewer larger pieces to a greater number of smaller pieces.
2. Average diameter 16 cm in cut only.3. Average diameter 21 cm in cut and burn plots.4. Shift in decay to the lower decay classes.
• Burn only – 1. Less of a diameter reduction relative to the cut, cut and burn plots
(8 cm) due to no inputs of smaller diameter logs.
• Variation in topography, aspect and past fire history likely plays a large role in CWD dynamics.
• Spatial patterns do not show a trend with cutting and or burning treatments and fall within pretreatment spatial variability.
Recommendations for Managers
• Contact– Jim Innes – [email protected]
– http://teakettle.ucdavis.edu
• Cutting and cutting and burning alter the structure of CWD more so than fire alone.
• Reductions in log diameters may impact habitat availability for some species. Leaving some larger logs may mitigate diameter decreases after cutting and burning.
• Spatial patterns do not appear to be altered by the treatments beyond the pretreatment range of variability at the studied scale.