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The effects of fire suppression on ecosystem processes: Evidence from the Teakettle Experimental Forest

The effects of fire suppression on ecosystem processes: Evidence from the Teakettle Experimental Forest. Malcolm North, USFS Sierra Nevada Research Center, Davis, CA. mnorth@ucdavis.edu. Fire suppression has increased stem density, canopy cover and shade tolerant YADA, YADA, YADA…….

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The effects of fire suppression on ecosystem processes: Evidence from the Teakettle Experimental Forest

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  1. The effects of fire suppression on ecosystem processes: Evidence from the Teakettle Experimental Forest Malcolm North, USFS Sierra Nevada Research Center, Davis, CA. mnorth@ucdavis.edu

  2. Fire suppression has increased stem density, canopy cover and shade tolerant YADA, YADA, YADA……. What about ecosystem processes? How do forest structural and compositional changes affect ecological functions? Following processes often requires a study to ‘drill’ down in one or a few locations with an interdisciplinary team

  3. Teakettle Experiment’s location, design, and integrated sampling scheme Each plot is 200 by 200 m Total plots = 18 How representative is one 200 ha area for Sierra Nevada forests?

  4. Processes discussed Conceptual model used in the Teakettle Experiment

  5. Mortality has significantly changed Compare live and dead tree distributions (n=43,518) *Significant Difference Spatial Pattern Species Composition Size * * * * Greater than expected mortality in largest size class No significant differences by species Significantly higher than expected mortality for ‘crowded’ trees Mortality Patterns Historical fire—broad scale killing of small trees, selection by species Current pest/pathogen—clustered killing of high-density trees, disproportionate large tree mortality, no species selection Consequences: Retain current species composition, reduce large trees and create gaps

  6. Carbon Dynamics: Less carbon in modern fire-suppressed forests than active-fire (1865) forests due to loss of large trees1 (The plus is forests have potential to sequester a lot more carbon) Additionally, making forests more fire resilient incurs a substantial carbon emission penalty2 Total Live Tree Carbon Stocks: 1865: 346 Mg C/ha Current Forest: 249 Mg C/ha 1) North, M., et al. In review. Ecol. Apps. 2) Hurteau, M. and M. North. 2009. Frontiers in Eco. And Environ. doi:10.1890/080049

  7. Regeneration: Standardizing production by basal area, white fir and incense cedar produce 5-40 times more seed than pines NB-NT: No burn/no thin NB-UT: No burn/understory thin NB-OT: No burn/overstory thin B-NT: Burn/no thin B-UT: Burn/understory thin B-OT: Burn/overstory thin More pine establishment & better survival in burned plots Cannot overcome inertia of current composition unless seed source is removed (cut large fir and cedar seed ‘polluters’), pine is planted or sites are repeatedly burned

  8. Microclimate and Decomposition Variation in soil surface temperature by time of day (x axis) and day of year (y axis) between 3% and 76% canopy cover Closed canopy (cc) has slower decomp rate than open canopy Foliage volume distribution by tree height and species: Note white fir (abco) dominates foliage profile Decomposition Rate Faster Slower Soil Depth (cm) Decomposition shuts down earlier with less snow on the ground,

  9. Soil Environment Fire Suppressed Forests: more litter and CWD, canopy cover Less: bare ground, understory light, and soil moisture

  10. Reduction in plant diversity and cover: limited by soil moisture availability

  11. Canopy Openness Effects on Understory Vegetation Cover High shrub cover in open canopy conditions Stanislaus-Tuolumne Experimental Forest Methods of Cutting Plot 1929 Herb Canopy Openness PercentCover Loss of Shrubs: Habitat for some birds and small mammals ‘Hotspots’ of available N 80 Canopy Cover 40

  12. Patch type strongly affects ecological conditions Patch Type

  13. Forest Canopy Gaps PAR Spatial Variability of Select Processes Ceanothus Cover Available Nitrogen Vegetation Structure: Soil Moisture Litter Depth Ecosystem Process: Did Fire Re-Mix These Conditions?

  14. After treatments, many ecosystem processes were still strongly influenced by patch type Closed Canopy Shrub (Ceanothus cordulata) Open Gap Importance of Patch Legacy Pre-treatment patches interact with thin and burn to determined fine-scale functional heterogeneity

  15. Plants sensitive to disturbance Pyrola picta White-flowered hawkweed Pterospora andromedea ‘Pinedrops’ Corallorhiza maculata

  16. How do thinning and prescribed affect ecosystem processes?

  17. How does fire-suppressed forest structure affect ecosystem processes? • High stem density: Change in mortality. Limits soil moisture affecting and in some cases ‘stalling’ most of the ecosystem processes followed. • High canopy cover: reduces microclimate spatial and temporal variability, and surface snowpack depth slowing decomposition. • Fuels accumulations: Heavy litter and coarse woody debris homogenizes the forest floor substrate reducing understory diversity and cover, habitat variability.

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