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Jim Innes and Malcolm North USDA-PSW Sierra Nevada Research Center Davis, California

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.

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Jim Innes and Malcolm North USDA-PSW Sierra Nevada Research Center Davis, California

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  1. 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

  2. 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).

  3. Study Site – Teakettle Experimental Forest • Patterson Mountain, California • Old growth mixed- conifer forest. • 2000 m elevation. 18, 4 hectare plots

  4. 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

  5. Hypotheses Thin 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.

  6. 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 % .

  7. 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).

  8. Results - Thin and burn treatment 1. 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%.

  9. Results - Thin and burn treatment • 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).

  10. 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).

  11. 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.

  12. Spatial Patterns – Control plots Clustered Control 1 Control 2 Random Regular • 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 3

  13. Spatial Patterns – Treated plots Shelterwood CASPO Pretreatment Unburned shelterwood Pretreatment Unburned CASPO Clustered Random Regular Pretreatment Burned shelterwood Pretreatment Burned CASPO Burn only pretreatment Burn only post-treatment • No trend in spatial patterns with treatments. • or in significance of clustering with treatment.

  14. Summary • Cut and cut and burn treatments – • Change in quality of CWD from fewer larger pieces to a greater number of smaller pieces. • Average diameter 16 cm in cut only. • Average diameter 21 cm in cut and burn plots. • 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.

  15. Recommendations for Managers • Contact • Jim Innes – jinnes@fs.fed.us • 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.

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