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 18, 4 hectare plots Patterson Mountain, California Old growth mixed- conifer forest. 2000 m elevation.

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 (m 3 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 (m 3 ). –CASPO mean piece large- end-diameter 21% (16 cm, (p=0.0001). –Mean piece volume 44% (2.1 m 3, p=0.004). –Shelterwood mean piece large-end-diameter 19% (13.4 cm, p=0.0001). – Mean piece volume 60% (2.9 m 3, p=0.0001).

8. Results - Thin and burn treatment 1. Decrease in per hectare plot density, volume (m 3 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 (m 3 ) and mean piece large-end-diameter (cm). CASPO 60% mean piece- volume (2.2 m 3, P=.0001). 29% mean piece large-end- diameter (22.4 cm, p=.0001). Shelterwood 56% mean piece- volume (3.2 m 3, P=.007). 24% Mean piece large-end- diameter (20.5 cm, p=.0001).

10. Results – Burn only treatment Increase mean piece volume (m 3 ) and mean piece large-end- diameter (cm). –Mean piece volume by 50% (2.5 m 3, 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 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 2 Clustered Random Regular

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

14. 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.

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.