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Alan Tepley and Jane Kertis May 28, 2009 Fire Regimes and Successional Pathways in the Western Cascades of Oregon.

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Presentation on theme: "Alan Tepley and Jane Kertis May 28, 2009 Fire Regimes and Successional Pathways in the Western Cascades of Oregon."— Presentation transcript:

1 Alan Tepley and Jane Kertis May 28, 2009 Fire Regimes and Successional Pathways in the Western Cascades of Oregon

2 Fire-regime gradients in the Western Cascades – Gradients of driving factors – Location and severity of recent fires Fire effects and successional trajectories – Warner Creek post-fire stand structure – Age structure in the central western Cascades Topographic influences on fine-scale variability Influence of fire-severity mosaics on subsequent burn patterns – 2008 Rattle Fire reburn of the 1996 Spring Fire Fire Regimes in the Western Cascades as a Context for Restoration

3 Fire Regimes Based on Kuchlers Potential Natural Vegetation Types Stand-Replacement Fires 500+ yrs Stand-Replacement Fires 201–500 yrs Understory Fires 0–34 yrs Mixed-Severity Fires 0–34 yrs Brown et al Wildland Fire in Ecosystems: Effects of Fire on Flora

4 Data from NIFMID and ODF, Compiled by Ray Davis Not Modeled High Low Density of Lightning Ignitions (1970–2002) Mean Annual Precipitation (1961–1990) Gradients of Fire Regime Drivers Oregon Climate Service PRISM Project < > 390 Annual Precipitation (cm)

5 Frequency of Large Fires (1,000 acres) ( ) 1 burn 2 burns 3 burns Ray Davis, Unpublished

6 Dry Fire-Prone Provinces Frequency of Large Fires (1,000 acres) ( ) 1 burn 2 burns 3 burns Ray Davis, Unpublished

7 Low Moderate High Fire Severity Severity of Recent Fires in the Western Cascades 012 km Clark ,905 acres km Warner Creek ,960 acres km Spring ,960 acres km Apple ,139 acres 036 km Boulder ,505 acres km Shady Beach ,174 acres Clark Warner Creek Shady Beach Spring Apple Boulder Kilometers 60 N

8 Morrison & Swanson km Cook-Quentin Study Area Cumulative Effects of 19 th -Century Fires Low severity (< 30% mortality) High severity (> 70% mortality) Moderate severity (30–70% mortality) Comparison to Historical Fire Severity Kilometers 90 N Cook- Quentin Clark Warner Creek Shady Beach Spring Apple Boulder

9 Comparison of Two Recent Fires Seral Stage Distribution Pre-Fire Post-Fire (%) (%) Early 5 30 Mid 5 5 Late Fire Severity Low 61% Moderate 13% High 25% Kertis 2000 Spring Fire ,960 acres 036 Kilometers 9 N Kushla and Ripple 1998 Fire Severity Low 48% Moderate 12% High 40% Warner Creek Fire ,960 acres 024 Kilometers 6 N Seral Stage Distribution Pre-Fire Post-Fire (%) (%) Early Seral/Rock Sapling/Pole 9 4 Open Mature/Old 0 18 Closed Mature/Old 77 32

10 Pre-fire Density of Small Trees (5–30 cm dbh) Pre-fire Density of Small & Medium Trees (5–60 cm dbh) Pre-fire Density of Large Trees (> 100 cm dbh) R 2 = p = R 2 = p = R 2 = p = Basal Area Mortality (%) Density (stems/ha) Summarized from data of Larson and Franklin (2005) Warner Creek Fire Severity was Weakly Related to Stand Structure at a Plot Scale Density (stems/ha)

11 Low Severity < 30% BA Mortality (n = 31) Density (trees/ha) Survival Mortality Shade-Intolerant Shade-Tolerant DBH (cm) Survival Mortality Density (trees/ha) Moderate Severity 30–70% BA Mortality (n = 23) Density (trees/ha) Survival Mortality Shade-Intolerant DBH (cm) Density (trees/ha) Survival Mortality Shade-Tolerant High Severity > 70% BA Mortality (n = 14) DBH (cm) Survival Mortality Density (trees/ha) Shade-Tolerant Density (trees/ha) Survival Mortality Shade-Intolerant

12 Data from Jane Kertis, Prepared by Stuart Johnston Plot Burned at Low Severity

13 Data from Jane Kertis, Prepared by Stuart Johnston Plot Burned at Moderate Severity

14 Data from Jane Kertis, Prepared by Stuart Johnston Plot Burned at High Severity

15 Elevation (m) High: 3,196 Low: 45 Transect Location Willamette National Forest Study Area N Kilometers 2040 Oregon Eugene Bend Fall Creek Blue River Crest of the Cascades Warner Creek Fire

16 DBH (cm) Density (trees/ha) Survival Mortality Low Severity < 30% BA Mortality Density (trees/ha) Survival Mortality DBH (cm) Moderate Severity 30–70% BA Mortality Density (trees/ha) Survival Mortality DBH (cm) High Severity > 70% BA Mortality Density (trees/ha) No Evidence of Fire (n = 18) Low Severity (n = 19) Moderate Severity (n = 33) High Severity (n = 15) Before 1800 After 1800 Establishment Date Using the Past to Infer Successional Trajectories Comparing Warner Creek to Sites Burned in the 19 th Century Warner Creek post-fire data (shade-intolerant only) Sites burned in the 19 th Century (shade-intolerant only)

17 Low Severity < 30% BA Mortality Density (trees/ha) Survival Mortality Shade-Intolerant Shade-Tolerant DBH (cm) Survival Mortality Density (trees/ha) Succession Following Low-Severity Fire % of Sampled Trees Shade Tolerants (n = 340 trees) Shade Intolerants (n = 103 trees) Composite for 19 Sites 2 Representative Transects Establishment Date % of Sampled Trees Shade-TolerantShade-Intolerant with charred barkHardwood

18 % of Sampled Trees Shade Tolerants (n = 304 trees) Shade Intolerants (n = 106 trees) Establishment Date No Evidence of 19 th -Century Fire (composite of 18 transects) % of Sampled Trees Shade Tolerants (n = 340 trees) Shade Intolerants (n = 103 trees) Establishment Date 19 th -Century Low-Severity Fire (composite of 19 transects) Effects of Low-Severity Fire Shade- Tolerant Shade Intolerant Shade- Intolerant with charred bark

19 Moderate Severity 30–70% BA Mortality (n = 23) Density (trees/ha) Survival Mortality Shade-Intolerant DBH (cm) Density (trees/ha) Survival Mortality Shade-Tolerant Succession Following Moderate-Severity Fire Establishment Date % of Sampled Trees 2 Representative Transects % of Sampled Trees Shade Tolerants (n = 528 trees) Shade Intolerants (n = 350 trees) Composite of 33 Transects Shade-TolerantShade-Intolerant with charred barkHardwood

20 High Severity > 70% BA Mortality (n = 14) DBH (cm) Survival Mortality Density (trees/ha) Shade-Tolerant Density (trees/ha) Survival Mortality Shade-Intolerant Shade-TolerantShade-Intolerant with charred barkHardwood Establishment Date % of Sampled Trees 2 Representative Transects Succession Following High-Severity Fire

21 High-Severity Fire Low- Severity Fire Moderate- Severity Fire Stand Development Douglas-fir (> 200 yrs old) Western hemlock Western redcedar Douglas-fir (< 200 yrs old) Successional in Douglas-fir Forests

22 1-4 Decades Since Fire 100–200 Years Since Fire 300–500 Years Since Fire Stand Development Underburn Low-severity fire Moderate-severity fire Douglas-fir (> 200 yrs old) Western hemlock Western redcedar Douglas-fir (< 200 yrs old) Successional Pathways in Douglas-fir Forests

23 % of Sampled Trees Shade Tolerants (n = 104 trees) Shade Intolerants (n = 202 trees) Composite of 13 Transects Shade-TolerantShade-Intolerant with charred barkHardwood Establishment Date Representative Transects % of Sampled Trees Age Structure of Fire-Prone Stands with at least 3 Douglas-fir Cohorts

24 % of Sampled Trees Shade Tolerants (n = 304 trees) Shade Intolerants (n = 106 trees) Establishment Date No evidence of fire for > 350 yrs (composite of 18 transects) % of Sampled Trees Establishment Date Shade Tolerants (n = 104 trees) Shade Intolerants (n = 202 trees) At least 3 fires in the last 400 yrs (composite of 13 transects) Shade- Tolerant Shade Intolerant Shade- Intolerant with charred bark Comparison of Stand and Age Structure in the Most and Least Fire-Prone Sites

25 1,600 1,500 1,400 1,300 1,200 1,100 1, Ridgetop Elevation (m) Terrain Shape Probability of Occurrence ConcaveConvex Topographic Context for Stands with no Evidence of Fire for at Least 350 yrs Shade-Tolerant Shade-Intolerant

26 Probability of Occurrence for the Least Fire-Prone Stands < – – – – – – – – –0.50 Probability of Occurrence Present All Other Transects Transect Location Kilometers N Blue River Fall Creek Kilometers N Kilometers N

27 Insolation Probability of Occurrence Slope Gradient (%) Insolation Probability of Occurrence 1,600 1,500 1,400 1,300 1,200 1,100 1, Ridgetop Elevation (m) Topographic Context for the Most Fire- Prone Stands

28 Probability of Occurrence < – – – – – – – – –0.60 Present All Other Transects Transect Location Probability of Occurrence for the most Fire-Prone Stands Kilometers N Blue River Fall Creek Kilometers N Kilometers N

29 Clearcut High Severity Low Severity Moderate Severity Natural Opening Road Spring Fire Severity Spring Fire ,960 acres

30 Rattle Fire ,771 acres Clearcut High Severity Low Severity Moderate Severity Natural Opening Road Spring Fire Severity Rattle Fire Perimeter

31 September 14 September 15 2,202 acres burned September 16 4,182 acres burned September 17 3,069 acres burned The Biggest Fire Days 48% of the Rattle Fire (9,453 acres) burned from 9/14 to 9/17 Clearcut High Severity Low Severity Moderate Severity Natural Opening Road Spring Fire Severity

32 Increasing annual precipitation mean fire intervals proportion of fire covered by large high-severity patches influence of fuel moisture on fire extent and severity Increasing proportion of landscape covered by multi-cohort stands average number of cohorts per stand proportion of fire covered by large low-severity patches influence of fuel amount and continuity on fire extent and severity Summary and Conclusions An understanding of fire-regime gradients is useful in guiding restoration

33 Questions?


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