Transcript
Page 1: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes

Dan KashianDepartment of Forest, Rangeland, and Watershed Stewardship

Colorado State University

Page 2: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

Defining landscape ecology

YellowstoneNational

Park

TargheeNationalForest

1. Broad spatial scales

2. Spatial heterogeneity

3. Pattern and process

4. The human role/impact

Page 3: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

Outline

• Climate change and carbon cycling on the Yellowstone landscape

• Future directions

• Variability and convergence in forest structure

• Post-fire heterogeneity in forest regeneration• The 1988 fires in Yellowstone

Page 4: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

Yellowstone: an exciting place!

Page 5: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

The Yellowstone landscape

• Stand-replacing fires

• 100-300 year fire interval

• Large,“natural”landscape

Page 6: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

Light/Severe Surface Fire

Severe Surface/Crown Fire

Variation in burn severity

Yellowstone Burn Mosaic, 10/88

Page 7: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

Serotiny in lodgepole pine

Page 8: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

Variation in lodgepole pine serotiny

Page 9: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

Variation in regeneration density

>50,000 stems/ha

1,000 stems/ha

0 stems/ha

Page 10: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

Mapping regeneration density

Orthorectification Supervised classification

GIS map

Page 11: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department
Page 12: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

Do initially dissimilar stand structures eventually converge?

???

???

Page 13: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

Stand structure: Methods

• Chronosequential measurements of unburned standsacross the landscape.

• Analyses of size and age structures and spatial patterns

• Regression analyses to reconstruct past density of stands using tree ring widths.

Page 14: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

Variation in Stand Density

11,000 stems/ha

3,000 stems/ha

1,100 stems/ha

Stands shown arein the 50-100 year

age class

Page 15: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

Den

sity

(ste

ms/

ha)

0

2000

4000

6000

69000

71000

73000

75000 a

b

cd d

250

0

50

100

150

200

12 50-100 125-175 200-250 300-350

Age class (years)

Coe

ffici

ent o

f var

iatio

n (%

)

bb

c c

a

Variation and change in stand density with age

Page 16: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

0

5

10

15

20

25

30

35

40

45

50

0 2 4 6 8 10

Stand A: Initially dense

Age: 130 yearsDensity: 5,400 stems/ha

Page 17: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

Stand B: Initially sparse

Age: 130 yearsDensity: 1,020 stems/ha

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

0.0 2.0 4.0 6.0 8.0 10.0

Page 18: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

0

40

80

120

160

200

4 8 12 16 20 24 28 32 36

DBH Class (cm)

02

6

10

14

18

60 70 80 90 100 110 120 130Age (years)

Num

ber

of T

r ees

Initially densestand

• Unimodal, steepdistributions

• Dead trees common and small

Dead treesLive trees

Page 19: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

0

2

4

6

4 8 12 16 20 24 28 32 36

10

15

0

5

55 65 75 85 95 105 115 125

DBH Class (cm)

Age (years)

Num

ber

of T

r ees

Initially sparsestand

• Bimodal or widedistributions

• Dead trees muchless common

Dead treesLive trees

Page 20: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

-0.15

-0.05

0

0.05

0.15

1 2 3 4 5

-0.1

0

0.1

0.3

0.5

1 2 3 4 5L(t)

Reg

ular

C

lust

ered

Distance (m)

Initially dense stand: Spatial patterns

Pre-mortality(live + dead):stems clumped at all scales.

Post-mortality:stems random at most scales

Page 21: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

Initially sparse stand: Spatial patterns

Stems random at all scales

Distance (m)

L(t)

Reg

ular

Clu

ster

ed

-0.6

-0.2

0

0.2

0.6

1 2 3 4 5

Page 22: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

70-year-old stand

120-year-old stand

220-year-old stand

300-year-oldstand

70

70120

70120220

70120220

Page 23: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

0

5000

10000

15000

20000

25000

30000

12 70 120

DenseSparse

Stand Age (years)

Stan

d Den

sity

(st

ems/

ha)

Stand Density Trajectory Reconstruction

64248

13048

683 931

5400

1020

Page 24: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

Stand Density Trajectory Reconstructions

0

20000

60000

100000

12 70 125

Modeling age (years)

Den

sity

(ste

ms/

ha)

0

20000

60000

100000

12 70Modeling age (years)

Den

sity

(ste

ms/

ha)

12 70 125 220 300Modeling age (years)

12 70 125 220Modeling age (years)

Page 25: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

• Rule-based simulation model in Arc based on empirical data.

• Model run on a decadal time step with resolution of 50 meters (0.25 ha).

• Subroutines simulate self-thinning, infilling in young stands, infilling in older stands.

How do stand-level processesaffect landscape pattern?

Page 26: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

Landscape patternat 12 years following fire

Relative deviation from median density[(density-median)/median)]

-1 – -0.25-0.25 – 0.250.25 – 11 - 33 - 5>5

Median density = 2.967 stems/ha

Page 27: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

Landscape patternat 50 years following fire

Relative deviation from median density

-1 – -0.25-0.25 – 0.250.25 – 11 - 33 - 5>5

Median density = 1,091 stems/ha

12 70 125 220 300

Page 28: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

Landscape patternat 100 years following fire

Relative deviation from median density

-1 – -0.25-0.25 – 0.250.25 – 11 - 33 - 5>5

Median density = 866 stems/ha

12 70 125 220 300

Page 29: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

Landscape patternat 200 years following fire

Relative deviation from median density

-1 – -0.25-0.25 – 0.250.25 – 11 - 33 - 5>5

Median density = 619 stems/ha

12 70 125 220 300

Page 30: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

Landscape patternat 300 years following fire

Relative deviation from median density

-1 – -0.25-0.25 – 0.250.25 – 11 - 33 - 5>5

Median density = 627 stems/ha

12 70 125 220 300

Page 31: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

Landscape patternat 300 years following fire

(with small fires)

Relative deviation from median density

-1 – -0.25-0.25 – 0.250.25 – 11 - 33 - 5>5

Median density = 700 stems/ha

Page 32: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

Structure Conclusions

• Structural variability is likely related to initial variation in postfire density.

• Variation in stand structure across the landscape decreases with time and converges near 200 years.

• Large, infrequent disturbances leave an imprint on the landscape that may endure for two centuries.

Page 33: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

What are the implications of dissimilar stand structures for

landscape carbon storage?

• How do large fires affect landscape carbon storage?

• How sensitive is carbon storage of a landscape to changes in climate and/or disturbance regimes?

Page 34: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

Landscape carbon storage is affected by:• Balance between carbon accumulating in vegetation/forest floor and carbon lost through decomposition of dead wood.

• Changes in the stand density distribution across the landscape following fires.

• Changes in the standage distribution across the landscape followingfires.

Page 35: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

∆C

(g C

/ yr

)

Years Since Stand-Replacing Fire

0

∆C Vegetation

∆C Dead Wood

Total NEP

NEP = C gained (NPP) – C lost (decomposition)

Page 36: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

∆C Vegetation(g C/m2/yr)

Total NEP

(g C/m2/yr)

Cumulative NEP

(g C/m2)

0

50

100

Sparse

Dense

-500

50

Age Since Fire0 50 100 150 200 250

-6000

-4000

-2000

0

Page 37: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

Do stand structures “replace themselves”?

Sparse pre-fire Sparse post-fire

Dense pre-fire Dense post-fire

Little changein C stored

over fire cycle

Little changein C stored

over fire cycle

=

=

Page 38: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

Do stand structures “replace themselves”?

Sparse pre-fire Sparse post-fire

Dense pre-fire Dense post-fire

C lost over

fire cycle

C gainedover

fire cycle

=

=

Page 39: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

Stand age distributions affect landscape NEP

50 years

300 years150 years

10 years

Page 40: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

Modeling stand age and density effects on landscape C storage

Climate changemodel predicts fire frequency

(EMBYR)

Modeledcomponentsof C stocks

C stocks forage classes

Age distribution (ha)under wet or dry climate

Landscapeestimate of

C stocks

C stocks fordense & sparse

stands

Page 41: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

∆C

Stor

ed(g

C/m

2x

103 )

Current climate,50% dense

Wet,50% dense

Dry,50% dense

9

11

13

15Stocks

Wet,90% dense

Dry,90% dense

Wet,10% dense

Dry,10% dense

C St

ocks

(g

C/m

2 x

103 )

Stand age and density effects on C storage

-101

2 Change from current

-2

Page 42: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

Modeling future landscape C storage for Yellowstone

NEP forage classes

Age distributions (ha)

Modeledcomponentsof NEP

Pre-fire andpost-fire

vegetation mapsof Yellowstone

Landscapeestimates of NEP

Page 43: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

-120

-100

-80

-60

-40

-20

0

20

40

1989 2029 2069 2109 2149 2189 2229

Prefire NEP

Total Landscape NEP

Tota

l Lan

dsca

pe N

EP (g

C/m

2 /yr

- )

-30

-25

-20

-15

-10

-5

0

5

10

Cumulative C Storage

Cumulative C Storage (g/m

2x 100)Long-term changes in C storage for Yellowstone

Page 44: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

“Function” Conclusions:

• Equilibrium C storage is resistant to changes in disturbance regimes at landscape scales.

• Large changes in the distribution of stand densities on the landscape are necessary to shift its ability to store carbon.

• The post-1988 Yellowstone landscape will recover all carbon lost within the fire cycle (~230 years), but it is currently a large source of C to the atmosphere.

Page 45: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department
Page 46: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

Current Projects:

• Carbon budgets along replicated age and density chronsequences

• Landscape carbon budget of Yellowstone using Century, EMBYR and Landsat

• Changes in productivity with tree age usingstable carbon isotopes (∆13C/ ∆12C )

• Changes and variability in foliar nitrogen with stand age and denisty.

Page 47: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

Future research directions

How have disturbance regimes affected human land use, and how is this linked to climate change?

How do exotic disturbances affect forest structureand function compared to native disturbances?

What are the critical links between terrestrial systems(landscapes) and aquatic systems?

Page 48: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department

Defining Landscape Ecology

YellowstoneNational

Park

TargheeNationalForest

1. Broad spatial scales

2. Spatial heterogeneity

3. Pattern and process

4. The human role/impact

5. Collaboration

Page 49: Heterogeneity, legacies, and convergence: forest structure ......Heterogeneity, legacies, and convergence: forest structure and function on Rocky Mountain landscapes Dan Kashian Department