Do insect outbreaks reduce the severity of subsequent forest fires?

Transcription

1 Supplemental material for: Do insect outbreaks reduce the severity of subsequent forest fires? Garrett W Meigs*, Harold S J Zald, John L Campbell, William S Keeton, and Robert E Kennedy *Correspondence to: gmeigs@gmail.com Environmental Research Letters (2016) Contents Table S1 Figures S1-S9 1

2 Table S1 (page 1 of 3). Key attributes and sequential autoregression (SAR) model accuracy for fire events with prior mountain pine beetle (MPB) or western spruce budworm (WSB) activity. Fire name a Fire year a Fire extent (ha) a Prefire insect b SAR model R 2c Cabot Creek WSB Ryder Creek WSB Paulina MPB Canal WSB Dooley Mt WSB Little Baldy Mt WSB Monument Rock WSB Tanner Gulch WSB MPB Finley Butte MPB Sheep Mt WSB Bannon WSB Boundary WSB Four Corners MPB Fox Point WSB Indian Rock WSB Lakebeds WSB Little Malheur Complex (Ironside) WSB Reed WSB Road WSB Thunder MPB Yedlick WSB Miller Cr PNF WSB Bull Complex (Bull) WSB Bull Complex (Summit) WSB Jefferson WSB Skeleton-Evans West (Evans West) MPB Table continues on next page. 2

3 Table S1, continued (page 2 of 3). Fire name a Fire year a Fire extent (ha) a Prefire insect b SAR model R 2c Tower WSB Wheeler Point WSB Wildcat Complex (Wildcat) WSB Mile Post WSB Carrol Creek WSB Hash Rock WSB Range WSB Tamarack Creek WSB Dark Lake WSB Unnamed MPB Complex (747) WSB Cache Mt WSB Easy WSB Eyerly Complex (Eyerly) WSB Flagtail WSB Grizzly Complex (Winter) MPB Monoment-Malheur Complex (Monument) WSB B&B Complex (Booth) WSB Bull Springs WSB Davis MPB Fawn Peak Complex (Farewell) MPB Isabel MPB Link WSB Burnt Cabin WSB Mule Peak WSB Cascade Crest Complex (Black Crater) WSB Cascade Crest Complex (Puzzle) WSB Table continues on next page. 3

4 Table S1, continued (page 3 of 3). Fire name a Fire year a Fire extent (ha) a Prefire insect b SAR model R 2c Cedar Creek MPB Maxwell WSB Mt Hood Complex WSB Pollalie WSB Sharps Ridge WSB Tatoosh Complex MPB Thorn Creek WSB Tinpan WSB Tripod Complex (Spur Peak) MPB Tripod Complex (Tripod) MPB Van Peak MPB Boomer WSB Calamity Complex (Grapple) WSB Domke Lake Complex MPB GW Fire WSB Otter Creek WSB Shelton WSB Trout Meadows WSB Bridge Creek WSB Ochoco Fire Use WFU WSB Wizard WSB Big Sheep WSB Discovery MPB North Fork Complex WSB OR-MAF WSB Pyramid MPB Dollar Lake WSB a Fire name, year, and extent from b Insect type from Landsat time series atlas (Meigs et al 2015b). c SAR modeling described in detail in Methods section. 4

5 Figure S1. Relationship between cumulative prefire insect extent (% of fire perimeter) and prefire insect effect on burn severity (RdNBR spectral index) across fire events (individual points). The relationship does not vary with the proportion of fire extent affected by either mountain pine beetle (a, R 2 = 0.07, P = 0.26, n = 19) or western spruce budworm (b, R 2 = 0.04, P = 0.14, n = 62). 5

6 Figure S2. Relationship between fire extent (ha) and prefire insect effect on burn severity (RdNBR spectral index) across fire events (individual points). The relationship does not vary with fire event size for either mountain pine beetle (a, R 2 = 0.08, P = 0.25, n = 19) or western spruce budworm (b, R 2 = 0.02, P = 0.27, n = 62). Note logarithmic scale of x-axis. 6

7 Figure S3. Relationship between fire season (ignition day of year) and prefire insect effect on burn severity (RdNBR spectral index) across fire events (individual points). The relationship does not vary strongly with fire season (based on ignition date) for either mountain pine beetle (a, R 2 = 0.00, P = 0.81, n = 19) or western spruce budworm (b, R 2 = 0.07, P = 0.04, n = 62). 7

8 Figure S4. Relationship between drought condition of each fire year (Palmer Drought Severity Index; PDSI; state-level monthly values averaged for June to August) and prefire insect effect on burn severity (RdNBR spectral index) across fire events (individual points). The relationship does not vary across a range of warm-dry to cool-wet conditions (negative to positive PDSI values; Heyerdahl et al 2008) for either mountain pine beetle (a, R 2 = 0.00, P = 0.82, n = 19) or western spruce budworm (b, R 2 = 0.02, P = 0.33, n = 62). 8

9 Figure S5. Relationship between years since onset of insect outbreak and SAR model accuracy (R 2 ) across fire events (individual points). The relationship does not vary strongly with time since outbreak for either mountain pine beetle (a, R 2 = 0.16, P = 0.08, n = 19) or western spruce budworm (b, R 2 = 0.00, P = 0.65, n = 62). 9

10 Figure S6. Relationship between cumulative insect extent (% of fire perimeter) and SAR model accuracy (R 2 ) across fire events (individual points). The relationship does not vary strongly with the proportion of fire extent affected by either mountain pine beetle (a, R 2 = 0.16, P = 0.09, n = 19) or western spruce budworm (b, R 2 = 0.00, P = 0.63, n = 62). 10

11 Figure S7. Relationship between fire extent (ha) and SAR model accuracy (R 2 ) across fire events (individual points). The relationship does not vary with fire event size for either mountain pine beetle (a, R 2 = 0.11, P = 0.17, n = 19) or western spruce budworm (b, R 2 = 0.03, P = 0.18, n = 62). Note logarithmic scale of x-axis. 11

12 Figure S8. Relationship between fire season (ignition day of year) and SAR model accuracy (R 2 ) across fire events (individual points). The relationship does not vary with fire season for either mountain pine beetle (a, R 2 = 0.02, P = 0.57, n = 19) or western spruce budworm (b, R 2 = 0.04, P = 0.11, n = 62; fit statistics exclude clear outlier). 12

13 Figure S9. Relationship between drought condition of each fire year (Palmer Drought Severity Index; PDSI; state-level monthly values averaged for June to August) and SAR model accuracy (R 2 ) across fire events (individual points). The relationship does not vary across a range of warmdry to cool-wet conditions (negative to positive PDSI values; Heyerdahl et al 2008) for either mountain pine beetle (a, R 2 = 0.07, P = 0.26, n = 19) or western spruce budworm (b, R 2 = 0.02, P = 0.26, n = 62). 13