Fire effects monitoring on the George Washington/Jefferson ... · Fire effects monitoring on the...

Jean LorberThe Nature Conservancy

May 2016

Fire effects monitoring on the George Washington/Jefferson National Forest

and

Strategies for analyzing monitoring data

GW Plan ‘Creating diverse conditions’ is a recurring theme

Fire management strategies support a variety of desired conditions and objectives across the GWNF (e.g., to establish, maintain, control or restore forest vegetation, wildlife openings, open woodlands).

Forest and woodland ecological systems support a diversity of tree ages, from regeneration to old growth, providing a relatively stable mix of ecological conditions across the landscape over time.

Re-establish the Natural Range of Variation (NRV) of forest age and structure, at a landscape level

OAK Forest types Early Mid-CLOSED

Mid-OPEN

Late-OPEN

Late-CLOSED

Total

Desired % on landscape 100%



Mid-OPEN

Late-OPEN

Late-CLOSED

Total

Desired % on landscape 12% 7% 10% 57% 14% 100%

Photos of an OPEN gap – canopy cover 30-50%

Photos of an EARLY gap – canopy cover <30%

Photo of a weasel riding a woodpecker

GW-Jeff Plan ‘Creating diverse conditions’ is a recurring theme

Burn Plan objectives:

- Where it occurs, maintain canopy cover of 40%-70%.

- In closed canopy forest, create canopy gaps and cavity trees by non-uniformly killing 10-30% of overstory hardwoods.

- Top kill 30-80% of all small trees and shrubs less than 1”’ DBH

Vegetation Monitoring Program

Started in 2008, consists of 370 plots today• Program designed by TNC, USFS as an FLN project• Program implemented by USFS, with some support

from TNC• Currently drafting report of results

Sampling intensity

• Most units sampled twice: a “baseline” and a “post-burn” sample

• 220 plots

• A few units sampled three times, covering two burn events

• 60 plots

Vegetation Monitoring Dataset issues

Lots of variability in burn unit history, prior to sampling

• Is “baseline” a useful category?

• Recently re-categorized burn units based on burn history:

“baseline” sample event is re-named • Number of burns prior to sampling• Time since last burn

Burn01 Year01

Trade-off: loss of sample size vs better sense of veg response

Vegetation Monitoring Dataset

The effects of a 2nd burn 35 plots in 3 units*

(Burn1 Year5 vs Burn2 Year1)

*includes a unit that burned REALLY hot

The effects of a 1st burn 85 plots in 8 units

(Burn0 Year0 vs Burn1 Year1)

Sampling strata Pre-burn Post 1st burn, year 1

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ORY Live basal area (ft2/acre) 84 72 SS

Canopy cover >5ft tall (%) 83% 77% SS

The effects of a 1st burn (n=80)M

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RY Live woody stems/acre (1-4” dbh)shrub species only 125 43 SS

Tree species only 342 126 SS

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Live woody stems/acre (<1”dbh and>3.3ft tall) shrub species 1,121 302 SS

tree species 487 986 SS

oaks 108 164maples 138 308 SS

Live woody stems/acre (0.5-3.3 ft. tall)

shrub species only 28,568 63,165 SS

tree species only 7,238 13,340 SS

oak species only 2,419 3,462 SS

maple species only 1,283 2,722Vegetative cover (<3.3ft)

Forbs, grass, vines 6% 13% SS


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Mid-OPEN

Late-OPEN

Late-CLOSED

Total

Desired % on landscape


There are multiple goals for burning AND multiple conditions arising from burning

Vegetation Monitoring Analysis

Stratification of dataset can address heterogeneity

Stratify based on post-burn condition, using:

• Plot data itself

• Other methodology that categorizes burn unit condition

Represent results using a single average?***

Not the best way to capture and quantify fire’s variable effects

Vegetation Monitoring Analysis

Stratify by plot-level data

• Group all plots according to an important indicator of condition (e.g. basal area)1. All plots with post-burn BA of <30ftsq = EARLY2. All plots with post-burn BA of 30-60 ftsq = OPEN (woodlands)3. All plots with post-burn BA of >60 ftsq = CLOSED

• For any summary, calculate separate average for each category

Drawback: lots of variability in data at plot level, is it a true reflection of the category?

Alternative: stratify by other methodology

• included ~40 large burn units, each burned in late winter/early spring, in 1 day.• Most burns from 1999-2015• Looked a multiple years of leaf-on imagery

Methodology for delineating canopy “gaps”

Part 1. Quantify the extent of canopy mortality resulting from a prescribed fire

• delineated areas where canopy cover had been impacted by burning (aka “gaps”)

from GWNF Plan: EARLY <30% canopy cover OPEN 30-50% canopy cover

Minimum mapping size of ~ 1/4 acreConstant 1:5,000 scale

Two classes of canopy cover (CC) from GWNF PlanOPEN 30-50% CC

EARLY <30% CC

Methodology for delineating canopy “gaps”

17 acres

Canopy gaps after 1 burn

Sampling strata EARLY (n=10)

OPEN (n=10)

CLOSED (n=60)

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ORY Live basal area (ft2/acre) 18 a 56 b 83 c

Canopy cover >5ft tall (%) 26 a 68 b 87 c

MID

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ORY Live woody stems/acre (1-4” dbh)

shrub species only 0 0 A 64 ATree species only 11 AB 0 B 214 A

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Live woody stems/acre (<1”dbh and>3.3ft tall) shrub species 0 a 0 a 474 a

tree species 1,800 a 2,180 a 648 boaks 1,056 a 270 b 53 b

maples 155 a 890 b 291 aLive woody stems/acre (0.5-3.3 ft. tall) ---Nearest thousand---

shrub species only 143,000 a 129,000 a 38,000 btree species only 26,000 a 21,000 a 9,000 boak species only 13,000 a 4,000 b 2,000 b

maple species only 1,000 a 5,000 a 2,000 bVegetative cover (<3.3ft)

Forbs, grass, vines 9 A 7 A 1 a

The effects of a 1st burn (n=85) P O S T- b u r n s t a t u s


OPEN (n=10)

CLOSED (n=60)

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ORY Live basal area (ft2/acre) 18 A 56 B 83 C

Canopy cover >5ft tall (%) 26 A 68 B 87 C

MID

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shrub species only 0 a 0 a 64 aTree species only 11 ab 0 a 214 b

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CLOSED (n=60)

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tree species 1,800 b 2,180 b 648 aoaks 1,056 b 270 a 53 a







OPEN (n=10)

CLOSED (n=60)

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maples 155 a 890 b 291 aLive woody stems/acre (0.5-3.3 ft. tall) ---Nearest thousand/acre---





SUMMARY

Re-examining how we’re thinking about and analyzing monitoring data

• More attention paid to burn unit history prior to monitoring

• Report out results that address multiple fire and restoration targets

• Use other methodologies to cross-reference/stratify monitoring dataset

Relate results to new GWNF goals:


Oak Forest types EARLY Mid-CLOSED

Mid-OPEN

Late-OPEN

Late-CLOSED

Total

Desired % on landscape 12% 7% 10% 57% 14% 100%

EARLY successional forest

OPEN forest, all ages

12% of acreage67% of acreage

Part 1. Quantify the extent of canopy mortality resulting from prescribed fire

EARLY successional forest (% of acreage)

OPEN forest, all ages (% of acreage)

12%67%

Actual result (1 burn)

4%5%

GW target (oak system)

20%11%

Actual result (3+ burns)

Relate results to new GWNF goals:

Part 1. Quantify the extent of canopy mortality resulting from prescribed fire

Canopy Gaps within Burn Units, after 1 burn

N=28 % OPEN acres % EARLY acres % all gapsAverage 6.2% 6.5% 13%95% C.I. ± 2% ± 3% ± 4%

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Questions?CENTRAL APPALACHIANS

Thanks to GWNF staff Lindsay Curtin, Steve Croy, John Moncure and many others


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ORY Live basal area (ft2/acre) 85 84

Canopy cover >5ft tall (%) 74% 71%

The effects of a 2nd burn (n=30)M

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RY Live woody stems/acre (1-4” dbh)shrub species only 45 12

Tree species only 121 50

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tree species 596 403oaks 206 190

maples 118 115Live woody stems/acre (0.5-3.3 ft. tall)






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