Impact of a severe microburst on the structure of a mixed

deciduous forest on the Maryland coastal plain

Geoffrey ParkerSmithsonian Environmental Research Center

overview

• introduce a large-scale forest study• describe the onset of a severe weather event• approaches for evaluating the damage• summarize the various effects• ecological context of the event• next steps

Big Tree stem project

• 9528 Trees (DBH of 20 cm or greater)• 46.4 hectares (square)

– 106.5 football fields– 2840 volleyball courts

• 34 species of woody plants• other information

– location– mapping stage– crown class– condition– diameter at breast height (DBH)– elevation

2.5 12.5 22.5 32.5 42.5 52.5 62.5 72.5 82.5 92.5 102.5 112.5 122.5 132.5 142.50.01

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stem diameter class midpoint, cm

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minimum stem diameter, cm

…between 1900-1930 on the evening of June 5th 2002…

…the victim of an episodic and unpredicted disturbance event!!

Beech rootball

Beech uproot fall

Indirect damage – low snap

branch speared into ground

Topped fallen

Uprooted Tree in the Floodplain

ecological disturbance

• a disturbance is defined as a relatively discrete event that disrupts the structure of an ecosystem, community, or population, and changes resource availability or the physical environment (White and Pickett 1985).

• disturbance causes, patterns, dynamics and consequences are major research topics in ecology (Romme and Knight 1982; Risser et al. 1984; Turner 1987b, 1989; Baker 1989a, 1989c; Turner and Dale 1998).

disturbances in forest ecology

• disturbances play an important role in forest ecosystems and communities

• trees are sessile organisms and they care about where they live and who their neighbors are

• trees must adjust to the new conditions produced by the disturbance

• forest community structure• forest development • biomass production

why bother with tree elevation?

• drought and flood tolerance• elevation ranges from about

sea level (floodplain) to 87ft above sea level

• how can one get elevation information for each tree?

• county contour maps are insufficient resolution for tree-level elevations

contour map of the Big Tree Plot

5 ft contours

LIght Detecting and Ranging (LIDAR)March 2002

• Leaf-off• High

accuracy

Elevation

33.628 - 37.880

29.376 - 33.628

25.123 - 29.376

20.871 - 25.123

16.619 - 20.871

12.367 - 16.619

8.114 - 12.367

3.862 - 8.114

-0.390 - 3.862

crown class determination

D = Dominant CD = Co-dominant I = Intermediate S = Suppressed

objectives and hypotheses

• objectives:– survey the damage in the Big Tree Plot– incorporate the damage data into the existing database– determine disturbance trends and potential consequences

• hypotheses:– Damage distribution was not random:

• species• crown class• DBH• elevation

– tree fall direction was not random– forest biomass production was dramatically affected

methods

• storm damage survey– a categorical classification – compass readings of tree fall direction– causal agent

• storm (direct damage)• tree (indirect damage)

• Geographic Information Systems (GIS) – spatial representation of the Big Tree Plot and

storm damage

• statistical analyses

damage classificationDIRECT INDIRECT

DEAD LIVE DEAD LIVE

MAJOR MINOR

TOPPED

SNAPPED

UPROOTED

CROWN DAMAGE

BENT BY WIND

BENT BY FALLING TREE

BARK SCRAPED OFF

MINORMAJOR

TOPPED

SNAPPED

UPROOTED

CROWN DAMAGE

BENT BY WIND

example of direct and indirect damage

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Snapped Sycamore

Topped Dead Sweetgum

Snapped White Oak

White Oak – Minor Crown Damage

Snapped Mockernut

Snapped Sweetgum

BackRoad

15ft20ft

25ft

stem-snapped sycamore and

white oak

Northern Red Oak Uprooted

Major Crown Damage

Tulip branch fishhook break

Snapped Tree

snapped standing remnant

topped tree forming a canopy

gap

preliminary damage survey

• 21 different species affected• 22 different categories of damage• 408/9528 trees = 4.28%• generally fell in an easterly direction (40-90°)

Storm Damage Summary Table

TOTAL %TOTALINDIVIDUALS INDIVIDUALS TOTAL

SPECIES MAJOR MINOR MAJOR MINOR MAJOR MINOR MAJOR MINOR DAMAGED (BY SPECIES)TULIP POPLAR 2 . 36 80 2 . 6 15 141 5.02% 2949SWEET GUM 4 . 9 12 2 . 9 17 53 3.60% 1526BEECH 2 1 10 16 1 . 3 16 49 3.77% 1348RED MAPLE 2 . 7 8 1 . 4 7 29 5.94% 517MOCKERNUT HICKORY 4 . 4 4 1 . 2 3 18 3.79% 493PIGNUT HICKORY 1 . 4 2 . . 1 3 11 3.12% 364WHITE OAK 2 . 3 5 . . 1 3 14 4.06% 359SOUTHERN RED OAK . . 6 14 . . 1 4 25 7.84% 344ASH SP. 1 . 4 3 2 . . . 10 3.41% 303VIRGINIA PINE 7 . 2 . 2 . . . 11 4.68% 246BLACK OAK 1 . 4 4 . . 1 1 11 5.58% 208NORTHERN RED OAK . . 2 3 . . . . 5 3.11% 166BLACK GUM . . 1 . . . 2 1 4 3.08% 134OTHER OAK SP. 5 . 3 . . 1 . 1 10 6.80% 157OTHER UNCOMMON SP. 5 . 3 7 . . 1 1 17 4.28% 414CATEGORY TOTALS 36 1 98 158 11 1 31 72 408 4.28% 9528

DIRECT INDIRECTDEAD LIVE DEAD LIVE

map of June 2003 storm damage

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statistical analyses

• the distribution of the damage was not random among different tree species, crown classes, DBH or elevation

• contingency table comparing damaged and undamaged trees• Chi-square test to determine expected damage, which will be

compared to the actual

• tree fall direction was not random• circular statistics to determine angular distribution

• the forest biomass production was dramatically reduced

• estimations of biomass production and predicted loss, which is heavily dependant on crown class

distribution of damage by species

%TOTALSPECIES MAJOR MINOR (BY SPECIES)TULIP POPLAR 46 95 5.0%SWEET GUM 24 29 3.6%BEECH 16 33 3.8%RED MAPLE 14 15 5.9%MOCKERNUT HICKORY 11 7 3.8%PIGNUT HICKORY 6 5 3.1%WHITE OAK 6 8 4.1%SOUTHERN RED OAK 7 18 7.8%ASH SP. 7 3 3.4%VIRGINIA PINE 11 0 4.7%BLACK OAK 6 5 5.6%NORTHERN RED OAK 2 3 3.1%BLACK GUM 3 1 3.1%OTHER OAK SP. 8 2 6.8%OTHER UNCOMMON SP. 9 8 4.3%CATEGORY TOTALS 176 232 4.3%

DAMAGE

6% of total trees damaged

35% of total trees damaged

damage by crown class

crown classes

D = dominant

CD = co-dominant

I = intermediate

S = suppressed

MAJOR VS MINOR DAMAGE

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D CD I S

CROWN CLASS

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MAJOR ACTUAL MINOR ACTUAL

distribution of damage by DBH

MAJOR VS MINOR DAMAGE

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DBH RANGE (cm)

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damaged pasture trees

PASTURE TREE STORM DAMAGE

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DAMAGE CATEGORY

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DIRECT INDIRECT MAJOR MINOR TOTAL

•all damage was significantly higher than expected

•13 of the 54 known pasture trees were damaged

distribution of damage by elevation

MAJOR VS MINOR DAMAGE

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ELEVATION (m)

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MAJOR ACTUAL MINOR ACTUAL

elevation range:

0 = 0 – 5m

5 = 5 – 10m

10 = 10 – 15m

15 = 15 – 20m

20 = 20 – 25m

25 = 25 – 30m

tree fall direction

• only considered in cases of major damage

• mean fall direction was 65°, with a mean angular deviation of 49°

• live trees had comparable fall directions to the mean

• dead trees varied dramatically from the mean

tree fall direction

• indicative of potential wind pattern

• landscape features may have affected tree fall direction

• variation in fall direction can be explained by tree condition and damage classification

direct, major (live and dead) damage

tree fall direction – classification differences

Direct,Major, Live

Indirect,Major,

Dead

Indirect,Major,

Live

Direct,Major,

Dead

Ecosystem Consequences: Biomass Production

annual above-ground biomass production:annual wood production = 4.3 Mg ha-1

annual foliage production = 3.9 Mg ha-1

Total Production = +8.2 Mg ha-1

existing above-ground biomass:prior to the storm = 235.4 Mg ha-1

after the storm = 229.1 Mg h1

Biomass Change = -6.3 Mg ha-1

Almost one year’s worth of growth was destroyed.

conclusions

– distribution of the damage was non-random:• tulip poplars had the most number of trees damaged, but

southern red oaks had the highest percentage of damage by species

• dominant and co-dominant trees experienced more damage than expected, while intermediate and suppressed trees experienced less damage than expected

• In terms of DBH, even though most major damage was experienced by smaller trees the damage was less than expected, while larger trees had higher than expected damage

• pasture trees damage was higher than expected• higher than expected damage in low elevation ranges for

both major and minor damage categories

more conclusions

• tree fall direction was not random, but mostly between 40 and 90°, which may be indicative of an easterly wind direction

• biomass production of the forest was set back almost a year in this one event that only affected about 4% of the trees in the Big Tree Plot

future directions

• drought effect on root stability• windward vs. leeward location effect on damage

severity/occurrence• lack of objective data on the strength of the

storm … need to obtain meteorological information for the event

• explore the effect of the storm on the canopy structure and the production of gaps and increased understory light

many thanks

• Brianna Miles• Canopy Lab

– Michelle Berger– Rehanna Chaudhri– George Rasberry

• Nancy Lee• UMCP – Geography

Department– Steve Prince– Marcia Snyder

• Volunteers:– Dawn Miller– Joyce Schick– Melissa Parker– David Miles– Karen Yee– Kate Levendosky– Naomi Hosaka– Mandy Clancy– April Chiriboga– Jackie Allen– Chaquettea Felton

additional thanksLarry Atkinson, Elsa Barney, Bob Bless, Dan Boone, Martin Brown,

David Bowers, Donn Burkness, Jennifer Bush, Sarita Cargas, Brenda Chapin, Charles Chapin, Nina Chapotin, Saharah Moon Chapotin, Carol Chernega, Cliff Coryell, Richard Davenport, Marty Dobbs, Sarah Dunbar, Donna Dwiggins, Allison EddyBlouin, Nancy Fallin, Maiton Fernandez, Clay Fink, Jeanne Flight, Sheila Gallagher, Cameron Gerarden, Ned Hall, David Harding, Andreas Held, Daniel Higman, Yvon Kirkpatrick-Howatt, Alexandra Hui, Steven Kun, Bruce Lasala, Margaret Lasala, Michael Lefsky, Shannon Loux, Curtis McCarthy, Dawn Miller, Maureen Miller, Rob Mrowka, Sally Murray, Ajjani Nikkolai, Ian Parker, Melissa Parker, Corrie Miles, Jay O'Neill, Bobby Paintner, Wayne Paintner, Barbara Patoka, Dawn Pattarini, Bob Peel, Patricia Peters, Alec Poore, Francisca Saavedra, Ron Smithburger, Chase Posner, George Rasberry, Andrea Schindler, Ed Schmitt, Gretchen Seilstad, Elizabeth Stone, Peter Stone, Donna Tibbs, Kiernen Tinning, Don Weller, John Wiley, Robert Willard, Tom Willmon, and Tom Yanosky.