1. Different effects of thinning and burning on Sierran mixed-conifer ecosystems Malcolm North, USFS, Sierra Nevada Research Center, Davis, CA

2. STUDY SCALE FUNCTION / PROCESS TEAKETTLE EXPERIMENT ECOSYSTEM (10 ac) WATERSHED (3000-5000 ac) FIRE SURROGATE STUDY STAND (50-100 ac) LANDSCAPE (up to 500,000 ac) KINGS RIVER PROJECT Large-scale fire movement & behavior, spotted owls Water flow & nutrients; forest carnivores; birds; uneven-aged mgt. PLUMAS / LASSEN STUDY Stand dynamics, regene., management options; animals w/small home ranges Soils; microclimate; respiration; succession; food webs Focus and Scale of Some of the Fuel Reduction Experiments in California

3. Thinning Level:No BurnUnderstory Burn NoneControlBurn Only 25 cm < thin <76 cm Thin from below/No Burn Thin from below/Burn 25 cm < thin & leave 22 large t/ha Overstory thin/No Burn Overstory thin/Burn 18 plots, 4 ha each, 3 reps of each of the 6 treatments Teakettle Location, Design, Plot Layout and Timeline Burned November 2001, ‘off season’, for containment & air quality Pretreatment data (2-3 yrs for all studies) Treatments Post-treatment data (2-3 yrs for all studies) 1998 1999 2000 2001 2002 2003 2004  Monitoring (5-20 yrs)

4. Thinning Effects (using all trees in a 4 ha plot) Understory: 25 cm< thin < 76 cm Overstory (shelterwood): Thin > 25 cm & leave 22 large tree/ha

5. Teakettle’s Focus: Ecosystem Structure, Composition and Function

6. Collaborators

7. 1.What effect do shrubs have on forest succession and water dynamics? 2.Why is mixed conifer so strongly clustered? Are trees grouped by age cohorts? 3.Do significant reductions in canopy cover reduce regeneration survival and understory herb cover? 4.Did the fire and thinning treatments produce a desired diameter distribution? Teakettle Results: Focus on 4 Vegetation Questions Relevant to Developing Thinning and Burning Prescriptions

8. Saplings and shrubs compete for shallow water in early summer Trees rely on deep water through summer drought 0 20 40 60 80 100 MayJuneJulyAugust Percent of deep water used Tree saplings Overstory trees Shrub (Arctostaphylos spp.) (using isotope signatures of soil and plant water) Forest 20 30 40 50 60 70 80 90 May-02 Jun-02 Jul-02 Aug-02 Sep-02 Oct-02 Nov-02 Mycorrhizae Exclosure Root Exclosure Control 1. What effect do shrubs have on forest succession and water dynamics? From A. Plaemboeck Low tree seedling survival in shrubs and without root exclosure Shrubs become islands that can ‘lock’ a site against seedlings and herbs

9. 2. Why is mixed conifer so strongly clustered? Are trees grouped by age cohorts? Bonnicksen and Stone (1982) suggested pattern is due to grouped cohort age structure clustered

10. Are trees grouped by age cohorts? No: ages were not spatially autocorrelated (variogram not shown)

11. Krigged distribution of tree basal area in a 4 ha area Depth to bedrock for the a 4 ha area, where deeper soils are in red. (Determined by seismic survey) Why is mixed conifer so strongly clustered? One influence may be that tree groups reflect the geomorphic template (depth to bedrock) Note correlation between the grouping of tree basal area, mostly driven by clusters of large trees and the depth to bedrock

12. Mortality episodic: associated with La Nina droughts Most mortality in areas of high density Significantly higher than expected mortality for large trees Are small/intermediate trees depleting deep soil water pockets? 0 5 10 15 20 25 30 35 40 45 50 0 - 100100 - 500500 - 2000>2000 High Density Classes Low Percentage ALL DEAD 0 5 10 15 20 25 30 35 40 45 50 0 - 100100 - 500500 - 2000>2000 High Density Classes Low Percentage ALL DEAD * * * * How Might This Explain Current Mortality Patterns? * Significantly different than expected (Chi-square)

13. 3. Do significant reductions in canopy cover reduce regeneration survival and understory herb cover? Persistent gaps in mixed-conifer without regeneration and having few herbs Surface temperature by Julian date (y axis) and hour (x axis) for 3% and 76% canopy cover

14. Post-treatment: Germinant Survivorship Burned treatments had higher pine germinant survival Burn and thin treatments (BC and BS) also had the lowest white fir and incense-cedar survivorship Herb cover and richness (not shown) significantly greater in all burned vs. thinned treatments, regardless of canopy cover reduction

15. Axis 2 Increased separation of sugar pine and white fir based on light level and soil moisture Increased Micro-site Heterogeneity Pre-Treatment Post-Treatment Data and slide from Harold Zald and Andy Gray, PNW Research Light Soil H2O

16. Before fire suppression (1865) recruitment and mortality was ‘pulsed’ by fire and El Nino events Current diameter distribution 4. Did the fire and thinning treatments produce a desired diameter distribution?

17. 10-3031-6061-90>90 Size Class (cm) 0.0 0.2 0.4 0.6 Proportion VTM* (‘desired’ dist.) Control Burn.only Understory.only Understory...Burn Overstory.only Overstory...Burn 4.Did the fire and thinning treatments produce a desired diameter distribution? No: Not enough small and too many intermediate size trees taken * VTM is >2400 vegetation type mapping plots collected in the early ’30’s

18. Thinning alone ‘stalls’ herb development and does not favor shade-intolerant regeneration Fire’s important for reducing shrubs which are strong competitors with trees and herbs Group selection doesn’t appear to be needed Thinning treatments may need to target small trees in high density areas, particularly around large, old trees If prescribed fire is applied ‘off season’, thinning must be aggressive about cutting small trees Observation: Thinning prescriptions should stay focused on trees as fuels rather diameters or board feet What did we learn at Teakettle?