Mechanical fuels reduction treatments effects on fire behavior, fuel loads, and forest ecology

Transcription

1 Mechanical fuels reduction treatments effects on fire behavior, fuel loads, and forest ecology Osceola National Forest Sept. 8 th, 11 Sponsors: Conserved Forest Ecosystems Outreach and Research (CFEOR); Southern Fire Exchange (SFE: Joint Fire Science Program; US Forest Service; University of Florida Fire Science Lab Hosts: Jesse Kreye, and David Godwin, PhD Candidates James Camp and Dawn McKinstry, Research Assistants Leda Kobziar, Asst. Professor of Fire Science School of Forest Resources and Conservation, University of Florida Contact us: lkobziar@ufl.edu; (35)

2 Table of Contents Map of treatment locations.1 Treatment effects on shrubs & litter.. Understory composition...3 Rank of variables among treatments.4 Photo guide Fire behavior and effects.9-11 Soil characteristics Synopses..14 Driving Directions Head right (east) on US Hwy-9 approx. miles Turn left (north) on Ocean Pond Rd / CR-5A at the Ocean Pond Campground sign Cross the RR tracks and continue on Ocean Pond Rd over I-1 for approx. 7 miles Turn left (south) on Gum Swamp Rd / CR-5 at stop sign Continue approx. 1 mile experimental units on left Ocean Pond Rd / CR-5A Park on the right (north) side of Gum Swamp Rd

3 Map of Treatment Locations p. 1 Walking Path through Site: Image from ~ weeks post burn

4 Duff Depth Litter Depth Duff Depth Litter Depth Litter Depth Duff Depth Duff Depth Depth (cm) Litter Depth Mass (Mg/ha) Other shrubs Othe r shrubs Palmetto Other shrubs Other shrubs Palmetto Palmetto % Cover Height (m) Palmetto Osceola NF Fuels Treatment Effects 6 months post-burn & 1 year post-mowing Compartment 69: As of Sept. 5, 11 p. 8 Percent Cover and Average Height of Shrubs Avg. Shrub Ht Burn +burn Litter and Duff Depths and Mass Duff mass Litter mass Burn +burn

5 Osceola NF Fuels Treatment Effects 6 months post-burn & 1 year post-mowing p. 3 Percent Cover of Understory, Litter, and Bare Ground <.5 m height 4 Shrub Grass 14 Burn 31 Shrub Grass 56 Herb Litter Bare Ground 5 5 Herb Litter Bare Ground +Burn Shrub Shrub Grass Grass Herb 5 Herb 49 Litter Litter Bare Ground 4 Bare Ground 6 3

6 Osceola NF Fuels Treatment Effects 6 months post-burn & 1 year post-mowing p. 4 Biomass Burn + Burn Shrubs Litter Duff Understory Rank of Values Among Treatments (1 = highest value, 4 = lowest value) Palmetto Cover Palmetto Height 1 3 Other Shrub Cover Other Shrub Height Percent Cover Shrub (<.5 m ht.) Grass Herb 1 Ranking 1=highest value 4=lowest value =actual value is zero *Underline indicates a relatively larger difference from other values

7 Rate of Spread (m/min) Flame Length (m) Osceola NF Fuels Treatment Effects Photo Guide- CONTROL p. 5 Treatment: Photo Date: May 11 Location: Osceola National Forest Columbia County, Florida 3.657, Fuel Loading Treatment N 7 mean sd 1h (Mg ha -1 ) h (Mg ha -1 ) h (Mg ha -1 ) 1h S (Mg ha -1 ) h R (Mg ha -1 ) Litter (Mg ha -1 ) Duff (Mg ha -1 ) Shrub H-A (Mg ha -1 ) 9.6 Litter Depth (cm) 8..1 Duff Depth (cm) Palmetto Cover (%) 6 4 Palmetto Height (m) 1.. BA (m ha -1 ) Rate of spread Flame length Windspeed (km/h)

8 Rate of Spread (m/min) Flame Length (m) Osceola NF Fuels Treatment Effects Photo Guide- BURN TREATMENT p. 6 Treatment: Burn Only Treatment Date: February 11 Photo Date: March 11 Location: Osceola National Forest Columbia County, Florida 3.653, Fuel Loading Treatment Burn N 11 mean sd 1h (Mg ha -1 ) h (Mg ha -1 ) h (Mg ha -1 ).7.6 1h S (Mg ha -1 ) h R (Mg ha -1 ) Litter (Mg ha -1 )..6 Duff (Mg ha -1 ) Shrub H-A (Mg ha -1 ).3 Litter Depth (cm) Duff Depth (cm) Palmetto Cover (%) Palmetto Height (m).5.1 BA (m ha -1 ) Burn Rate of spread Flame length Windspeed (km/h)

9 Rate of Spread (m/min) Flame Length (m) Osceola NF Fuels Treatment Effects Photo Guide- MOW TREATMENT p. 7 Treatment: Only Treatment Date: August 1 Photo Date: October 1 Location: Osceola National Forest Columbia County, Florida 3.64, Fuel Loading Treatment N 9 mean sd 1h (Mg ha -1 ) h (Mg ha -1 ) h (Mg ha -1 ) h S (Mg ha -1 ) h R (Mg ha -1 ) Litter (Mg ha -1 ) Duff (Mg ha -1 ) Shrub H-A (Mg ha -1 ) 1. Litter Depth (cm) Duff Depth (cm) Palmetto Cover (%) 11 8 Palmetto Height (m).7.3 BA (m ha -1 ) Rate of spread Flame length Windspeed (km/h)

10 Rate of Spread (m/min) Flame Length (m) Osceola NF Fuels Treatment Effects Photo Guide- MOW + BURN TREATMENT p. 8 Treatment: & Burn Date: : August 1 Burn: February 11 Photo Date: March 11 Location: Osceola National Forest Columbia County, Florida 3.66, Fuel Loading Treatment +burn N 9 mean sd 1h (Mg ha -1 ) h (Mg ha -1 ) h (Mg ha -1 ) h S (Mg ha -1 ) h R (Mg ha -1 ).6.18 Litter (Mg ha -1 ) Duff (Mg ha -1 ) Shrub H-A (Mg ha -1 ). Litter Depth (cm) Duff Depth (cm) Palmetto Cover (%) 4 3 Palmetto Height (m).3. BA (m ha -1 ) Burn Rate of spread Flame length Windspeed (km/h)

11 Flame Length (m) Meters/ minute Fuels Treatment Effects on Fire Behavior *Immediate Post-Treatment Conditions p. 9 Potential Fire Behavior Immediate Post Treatment (Behave: customized FM9 for post-burned, Hough-Albini for others; actual Rx fire conditions) Burn and + Burn Predicted Rate of Spread 1 X observed (Burned ) 5 X observed () 3 Wind speed 6 (km/h) Burn Burn X Predicted Flame Length observed (Burned ) X observed () Wind speed (km/h)

12 Flame Length (m) Meters/ minute Fuels Treatment Effects on Fire Behavior *6 months post-burn & 1 mo. post-mowing p. 1 Potential Fire Behavior Present Day (Behave H-A model; 9 th % wildfire conditions) 45 Predicted Rate of Spread Burn Burn Wind speed (km/h) Predicted Flame Length Burn Burn Wind speed (km/h)

13 Number of Trees Percent Damage (% of crown) Percent Damage (% of crown) Actual Fire Effects on Trees Burn Only and + Burn (burned Feb. 6, 11) p Burn Only: Total Crown Damage (%) y = x R² = DBH (cm) 1 + Burn: Total Crown Damage (%) y = x R² = DBH (cm) 1 1 No. Trees with % Crown Scorch Burn Only + Burn Percent of Crown Volume Scorched

14 Est. Soil Volumetric Moisture Content (m 3 /m 3 ) Fuels Treatment Effects on Soil T & MC% p. 1 Soil Temperature Burning increased soil T throughout the study period. ing reduced soil T in the winter months and increased soil T during the growing season. Soil Moisture.5 Plots Burned Burn. BC C AB A C D B A A B A A +Burn.15 B B A A.1 AB B B A.5. Dec Jan Mar Apr May Jun Jul Aug Soil MC% was increased in the mowed plots, but less so in the droughty summer season. Increases are likely due to decreased evapotranspiration (ET) and interception, & increased litter cover. Burning initially increased soil MC% in the Burn Only units. Burning in the mowed plots did not have a clear treatment effect relative to the units.

15 7. Fuels Treatment Effects on Soil Carbon p. 13 Burn Soil Carbon Respiration Rates Soil C Respiration Rate μmol CO m sec Burn Plots Burned B A A AB C BC A AB B B A B. A A B AB 1. DEC JAN MAR APR MAY JUN Jul Aug 1-11 Soil Carbon Soil carbon and soil organic matter did not differ among treatments Soil carbon respiration (SCR) increased from January through July with a decline in August. This trend follows seasonal variations in soil T rather than soil moisture content. Burning in unmowed plots reduced SCR for months. ing followed by burning also showed a trend of reducing SCR. ing did not show an obvious effect on SCR.

16 Synopses & Take Home Messages After 6 mo. Post Burn and 1 mo. Post : Predictions of fire behavior suggest little difference among treatments for rate of spread Predictions suggest greater flame lengths in, and slightly greater FL in units. Burn and + Burn have virtually indistinguishable fire behavior, suggesting it is similarly mitigated by both treatment scenarios. Observed Fire Behavior & Effects on Trees: After 6 mo. regrowth, units had lower flame lengths and rates of spread than Burn Only Behave underpredicted actual fire behavior in Burn Only units. ing prior to burning effectively reduced percent crown volume scorch and TCD. Bark beetles and tree mortality are present in the Burn Only, but not the + Burn units. Vegetation and Ground Cover: 6 and 1 mo. post treatments, litter cover was near 5% in all treatments Burned units had more bare ground and grass than control units Only units had the highest grass and herbaceous component Palmetto and other shrub height, cover, and biomass were reduced by all treatments. Take-Home Messages p Although burning, (either following mowing or alone), mitigates potential fire behavior immediately post treatment, at six months post-burn fuels and vegetation recovered so that potential rate of spread would was no longer affected by treatment. However, flame lengths appear to be greatly reduced by all treatments when compared with controls, even after this recovery time period.. ing increases percent cover of herbaceous and grassy species, increasing functional diversity and potentially improving wildlife habitat. Mechanical disturbance to soils may be responsible for these effects. 3. Burning during the dormant season after ing decreases herbaceous and grass components of the understory, when compared with alone. 4. ing long-unburned sites prior to reintroduction of fire reduces fire behavior, decreases crown scorch and tree mortality, and results in low fire risk. We found no evidence of increased bole or fine root damage in + Burn sites. 5. Soil carbon and soil organic matter are not affected in the short-term by treatments; however, burning appears to decrease soil carbon loss and increase soil temperatures. Caveat: Although we have 113 plots across the forest, the data presented herein were generated from the demonstration site in compartment 69 for the purpose of this workshop. Our data collection is continuing, and our ultimate analyses will include data from all of the sampled areas, reflecting trends across the greater landscape. Conclusions may, therefore, change as the additional data are tested.