Disturbance & Ecology of Coastal Plain Forests

with a focus on Longleaf Pine

Dr. Steve Jack

Conservation Ecologist and Applied Forest Scientist Joseph W. Jones Ecological Research Center

Disturbance Ecology

• Develop understanding of what is “natural” for a given location and forest type

Disturbance Ecology

• Develop understanding of what is “natural” for a given location and forest type

• For disturbance should consider: – Frequency – Scale – What is left after disturbance

EXAMPLE: Natural Variation in Disturbances (based on ca. 20 studies; Seymour et al 2002)

1

Interval between Disturbances (at the same point on the landscape) - years

Con

tiguo

us A

rea

Dis

turb

ed a

nd R

egen

erat

ed -

ha

Severe Fire and Wind

100 1000 10000 0.0001

0.001

0.01

0.1

1

10

100

1000

10000

Natural Canopy Gaps

100-year return interval

Range =

.001 - .1 ha

Natural Disturbance Agents

In southeast many things can cause disturbance: – Wind – Lightning – Insects – Disease – Water – Fire

Natural Overstory Disturbance

More common sources in longleaf forest result in small scale disturbance – Lightning (more prevalent on xeric sites) – Competition (more prevalent on hydric

sites) – Wind (more prevalent on hydric sites) – Beetles/root rot – Fire

From Palik and Pederson (1996)

Suppression

DBH class (cm)

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70

Perc

enta

ge o

f tot

al p

opul

atio

n0

10

20

30

40

Unknown

0

4

8

12

16

Lightning

02468

10121416

Wind

0

4

8

12

16

Live

0

2

4

6

8

10

Mortality (trees ha-1 5 yr-1)

0 2 4 6 8 10 12

Num

ber o

f plo

ts

0

4

8

12

16

20

24

28

Mortality (m2 ha-1 5 yr-1)

0.0 0.2 0.4 0.6 0.8 1.0

Conceptual Longleaf Model

from Michener et al. 1996

Natural Disturbances

In longleaf forests result in: • Perpetual forests with multiple age classes • Continuous fuels through time and across

space – supports fire • Variable density and spacing (heterogeneity) • Advance regeneration seedling pools in

more open areas

Fire in Coastal Plain Forests

Role of Fire

• Maintain early successional state • Reduce fuel accumulations • Affects structure and function

– Reduced or absent midstory – Species rich ground cover – Nutrient cycling

Day 1 3 months

1 year

3 years

10 years

30 years

Fire and Biodiversity

Fire is the overriding feature that sustains the biodiversity of the longleaf pine ecosystem – Frequent – Continuous over

time

Diverse Ground Cover Community

Diverse Faunal Community

Longleaf Pine Prior to European Settlement

Longleaf Communities - Montane

Longleaf Communities - Sandhills

Longleaf Communities - Mesic

Longleaf Communities - Flatwoods

Longleaf – Wide Ecological Amplitude

• High water use efficiency – tolerates droughts, extensive root system

• Overstory trees can survive short-duration flooding

• Unique regeneration habit – tolerates fire, drought-tolerant once established

• Associated understory species have similar characteristics

• Resistant to pests, disease, physical damage • FIRE adapted (required?) species

Management at Ichauway

With Predicted Climate Change …

• What factors will change, and how will the changes affect the forest? – Altered precipitation patterns? – Elevated average temperatures? – More severe weather events? – More wildfires? Reduced use of Rx-fire?

• What forest types will be best adapted to the

“new” (and changing?) conditions?

Disturbance Frequency & Extent with Climate Change

from Michener et al. 1996

Catastrophic flooding

Droughts

Hurricanes & Tropical Storms

Heard from Experts

Hurricanes & Tropical Storms

Hurricanes & Tropical Storms

Hurricane Damage

Hurricane Damage

Hurricane Damage

• Southern MS Katrina Damage • Two 20 year old plantations, each with stands of

loblolly, slash and longleaf

Species Type of Hurricane Damage (%)

None Snapped Leaning Blown Over

Loblolly 16.3 75.9 5.7 2

Slash 52.4 38.1 7.8 1.7

Longleaf 64 8.9 16.9 10.2

Source: MS Forestry Commission

Flooding Events

Drought Response

• Large effects on regeneration – Seedling survival – Seed production

• Cumulative effects on overstory – Decreased vigor – Increased susceptibility to pests

• Ability to burn, mortality following fires

Changes in Fire Regimes

Changes in Fire Regimes

Forest Responses to These Changes?

• Fire-maintained longleaf forests may be in best position to continue under altered climate

• But what about other forest types that are more common on the landscape?

Mixed Pine – Hardwood Forests