Transcript Slide 1
The effects of fire suppression on ecosystem processes: Evidence from the Teakettle Experimental Forest Malcolm North, USFS Sierra Nevada Research Center, Davis, CA. [email protected] 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 Teakettle Experiment’s location, design, and integrated sampling scheme bc3 bs3 bc2 us3 un 3 us1 us2 uc2 uc3 Each plot is 200 by 200 m Total plots = 18 uc1 un2 bc1 bn3 bn2 un1 bs2 bs1 bn1 Thinning Level: Unburned Burn None Control (UN) Burn Only (BN) Understory CASPO thin (25 cm < thin <76 cm) Unburned/Thin from below (UC) Burn/Thin from below (BC) Shelterwood thin (25 cm < thin & leave 22 large t/ha) Unburned/Overstory thin (US) Burn/Overstory thin (BS) How representative is one 200 ha area for Sierra Nevada forests? STUDY PRINCIPAL INVESTIGATOR INSTITUTION Microclimate, Soil Respiration Jiquan Chen, Siyan Ma & Suong Rhu Univ. of Toledo, OH Soil Nutrients Heather Erickson Univ. Metropolitan, San Juan, PR Decomposition Marty Jurgenson Michigan Technology University, Houghton, MI Fire History Michael Barbour, Rob Fiegener, Univ. of California, Davis, CA Tree Regeneration & Soil Moisture Andrew Gray & Harold Zald Pacific Northwest, Forest Inventory Analysis, Corvallis, OR Canopy Invertebrates Tim Schowalter Louisiana State Univ, Baton Rouge, LA Tree Pest & Pathogens David Rizzo, Tom Smith, Tricia Maloney Univ. of California, Davis, CA Flying Squirrels, Chipmunks & Truffles Marc Meyer, Doug Kelt & Malcolm North Univ. of California, Davis, CA Soil & CWD Invertebrates Jim Marra & Bob Edmonds Univ. of Washington, Seattle, WA Lichen Growth & Dispersal Tom Rambo Univ. of California, Davis, CA Nitrogen Dynamics, Frankia Diversity & Response to Fire Brian Oakley, Jerry Franklin & Malcolm North Univ. of Washington, Seattle, WA Understory Herb & Shrub Diversity Rebecca Wayman & Malcolm North Univ. of California, Davis, CA Global Climate Change & Tree Demography Matthew Hurteau & Malcolm North Univ. of California, Davis, CA Mycorrhizal Diversity/Water Movement using Stable Isotopes Tom Bruns, Antonio Izzo, Agneta Plamboeack, Todd Dawson Univ. of California, Berkeley, CA Seed Dispersal Ruth Kern Calif. State Univ. Fresno, CA Tree/Shrub Mortality & Growth, Truffles, Cones, Coarse Woody Debris, and Diameter Growth Malcolm North, Jim Innes Pacific Southwest Research, Davis, CA Processes discussed Conceptual model used in the Teakettle Experiment COMPONENT STUDIES MANIPULATIONS STRUCTURE FUNCTION AND COMPOSITION OF FUEL-LOADED FOREST DIRECT EFFECTS OF TREATMENTS (FIRE/THINNING) ALTER LITTER REDUCE BUFFERING REDUCE DENSITY SOILS MICROCLIMATE FOREST STRUCTURE HERBIVORY FUNGI RESILIENCE EVAPOTRANSPIRATION CORE PROCESSES NUTRIENT CYCLING INVERTEBRATES ECOSYSTEM RESPONSE DECOMPOSITION MORTALITY RESPIRATION REGENERATION EPIPHYTES FOREST PRODUCTIVITY & DIVERSITY GROWTH PATHOGENS WATER USE PLANTS DECLINE *Significant Mortality has significantly changed Compare live and dead tree distributions (n=43,518) Difference Spatial Pattern 80 * 60 70 50 60 30 50 High Class II Class III Density Classes Class !V Low Significantly higher than expected mortality for ‘crowded’ trees * 10 0 20 10 Class I * 30 5 0 All Dead T rees 0 ABCO ABMA CADE PIJE PILA OTHER No significant differences by species >100.1cm * 10 % of Dead 20 80.1 - 100.0 cm 15 40 All T rees 30 60.1 - 80.0 cm DEAD 20 % of Stand 40 5.0 - 20.0 cm ALL 25 Percentage 35 Percentage Percentage 40 40.1 - 60.0 cm 45 Size 20.1 - 40.0 cm 50 Species Composition Greater than expected mortality in largest size class 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 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 abco abm a cade pila pije other/unk(1865) snags C arbon 1865 C arbon D ensity (# stem s/ha) 120 150 100 M gC /ha 170 50 50 0 0 0 20 40 60 80 100 120 140 20 cm diam eter classes 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 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 Variation in soil surface Microclimate and Decomposition temperature by time of day (x axis) and day of Foliage volume distribution year (y axis) between 3% by tree height and species: and 76% canopy cover Note white fir (abco) dominates foliage profile a Wind River b 60 30 abco abma cade pije pila 50 40 2 Soil Depth (cm) abam psme tabr tshe 40 Height (m) 75.0 0 Teakettle 60 50 Closed canopy (cc) has slower decomp rate than open canopy Decomposition Rate Faster Slower 4 80.0 85.0 90.0 CC CECO OC ARPA 6 8 30 10 20 20 10 10 0 5000 10000 15000 Foliage Volume (m3/ha) 20000 0 12 Decomposition shuts down earlier with less snow on 14 the ground, 16 1000 2000 3000 Foliage Volume (m3/ha) Soil Environment Fire Suppressed Forests: more litter and CWD, canopy cover Less: bare ground, understory light, and soil moisture Reduction in plant diversity and cover: limited by soil moisture availability Canopy Openness Effects on Understory Vegetation Cover High shrub cover in open canopy conditions Stanislaus-Tuolumne Experimental Forest Methods of Cutting Plot 1929 Percent Cover Herb 80 Canopy Openness Canopy Cover Loss of Shrubs: Habitat for some birds and small mammals ‘Hotspots’ of available N 40 Patch type strongly affects ecological conditions Patch Type Closed Canopy Open Gap Shrub Moderate, low light Most extreme Hot, dry Intermediate Highest Lowest Invertebrate Div. Very High Very Low Fewer, but endemic Soil Respiration High Low Very high Decomposition Rate Low High Moderate Regene Growth/Mortality Intermediate/Low High/High Very slow/High Food Chain ‘Importance’ High Low Intermediate Locked up Very Low Very High Low Highest Very Low Microclimate Plant Diversity Available Nitrogen Soil Moisture Ecosystem Process: Vegetation Structure: Spatial Variability of Select Processes PAR Forest Canopy Gaps Ceanothus Cover Available Nitrogen Litter Depth Soil Moisture Did Fire Re-Mix These Conditions? After treatments, many ecosystem processes were still strongly influenced by patch type Importance of Patch Legacy Closed Canopy Open Gap Shrub (Ceanothus cordulata) Pre-treatment patches interact with thin and burn to determined finescale functional heterogeneity Plants sensitive to disturbance Pyrola picta White-flowered hawkweed Corallorhiza maculata Pterospora andromedea ‘Pinedrops’ How do thinning and prescribed affect ecosystem processes? Effect Possible Reason Increase small scale variability Increased habitat heterogeneity Plant Diversity Large increase Significant reduction in litter and slash Invertebrate Div. Large increase Increased habitat heterogeneity Immediate decrease than building Bole removal and combustion than tree growth Decomposition Rate Increase Increase in moisture Tree Growth/Mortality Large increase after 2 yrs/ Increase Nutrient flush, increase moisture/ Burn Generalist—no change Specialist--decrease No change in seed abundance/truffles reduced Available Nitrogen Large Increase Burned shrubs Soil Moisture Large Increase Reduced tree density Microclimate Carbon Store Food Chain Importance How does fire-suppressed forest structure affect ecosystem processes? 1) High stem density: Change in mortality. Limits soil moisture affecting and in some cases ‘stalling’ most of the ecosystem processes followed. 2) High canopy cover: reduces microclimate spatial and temporal variability, and surface snowpack depth slowing decomposition. 3) Fuels accumulations: Heavy litter and coarse woody debris homogenizes the forest floor substrate reducing understory diversity and cover, habitat variability.