Effects of Forest Management Practices on Carbon Storage

Coeli M. HooverUSDA Forest Service, Northern Research Station

Forest PLUS, Washington DCDecember 6, 2013

Trail Map

• Management effects on aboveground C stocks– Long-term thinning studies

• Management treatment effects on forest floor and soil C stocks– State of knowledge– Results from field study

• Questions

Management Effects on Aboveground Carbon Stocks

Long-term Thinning Studies

• Thinning studies with long measurement records can be used to investigate the carbon consequences of different management practices

• Studies are usually of similar design, and apply a variety of thinning levels

• Structure study at Kane EF was designed specifically to look at effect of method, using a single density

• Challenges – lack of documentation, control plots, irregular measurement intervals, etc.

Aboveground Live Tree Carbon

1975 1980 1985 1990 1995 2000 20050

20

40

60

80

100

120BelowAboveControl

Indicates when a thinning treatment occurred

Year

mtC

/ha

Structure Study - KEF

Structure Study - KEFAverage Annual Change - AGL Carbon

Below Above Control-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.01975-19891975-2005

Treatment

mtC

/ha/

yr

Crop Tree Thinning - BEFAboveground Live Tree Carbon

1958 1969 1975 19900

20

40

60

80

100

Heavy

ControlLight

Year

mtC

/ha

Crop Tree Thinning - BEF

Average Annual Change - AGL Carbon

Heavy Light Control0.0

0.5

1.0

1.5

2.0

2.5

3.01964-19751958-1990

Treatment

mtC

/ha/

yr

Mixed Oak Stocking- Vinton Furnace EF

1962 1976 1984 1996 20060

20

40

60

80

100

120

Aboveground Live Biomass Carbon

40%50%70%100%

tC/h

a

Mixed Oak Stocking

Average Annual Change - AGL Carbon

40% 50% 60% 70% Control0.0

0.5

1.0

1.5

2.01966-19841962-2006

Treatment

mtC

/ha/

yr

Summary• Over the long term, plots

will often end up with about the same amount of live biomass carbon across treatments

• However, the rate of accumulation may be quite different, especially in the period following treatment

Are your goals short- or long-term?

Management Impacts on Forest Floor and Soil C Stocks

Mini literature review – mineral soil

• Overall, significant effects of harvesting on soil C have not been detected– Some evidence that boreal soils may respond

• Some cases of short-term increases in C in surface soils

• A few cases of short-term decrease in C in either the surface or deeper soils

• Some evidence that changes may occur at depth over longer time frames, but few studies have addressed this topic

Mini literature review - forest floor

• Literature includes chronosequences and control/treatment studies

• Problem of mixing of forest floor and mineral soil often complicates interpretation of results

• Good evidence that forest floor carbon stocks often decline after harvest– Recovery may take several decades

Most recent meta-analysisNave et al. 2010 (Forest Ecology and Management)

• Analyzed C content (t/ha) and concentration (% C)

• 75 publications met criteria– Control and harvest– Temperate forest

• Analyzed 432 response ratios from papers published between 1979-2008

• Largest analysis to date

Overall results from Nave et al. 2010

• Forest floor– C storage declined by 30±6% after harvest– Significantly different between hardwoods and

softwoods• Conifer/mixed stand: -20%• Hardwood stand: -36%

• Mineral soil– No significant overall effect– Variation best explained by soil taxonomy

Overall results…

Nave et al. 2010

Digging deeper…

Nave et al. 2010

Results from regional work

• Investigated surface soil and forest floor C stocks in long-term thinning studies

• Variety of treatments: clearcutting, thinning to different densities– e.g., 90 ft2, 60 ft2, 30 ft2, 70% RD, 40% RD

• All sites northern hardwood• States included WV, NY, PA, WI, NH• Some sites treated once, others twice• Results in Carbon Balance and Management

2011(C. M. Hoover)

Forest Management Effects Study Sites

Argonne

Bartlett

SUNY Heiberg

Kane

Fernow

Middle Mountain

Results Summary• Forest floor stocks were variable, ranging from

2.4-18 mtC/ha– General trend of increasing S to N– No significant effects related to treatment

• Surface (0-20 cm) soil stocks range from a low of 32 to a high of 78 mtC/ha– Most sites fall between 55-65 mtC/ha– Overall, no treatment effects on C stocks or C

concentrations – Similar patterns for 0-5 cm depth as 0-20 cm

Kane Experimental Forest (PA)

0 2 4 6 8 10 12 14 16 18 2002468

101214161820

Light thinHeavy thin

tC/ha control

tC/h

a tr

eate

d

Forest Floor C Stocks –Thinned and Control

0 2 4 6 8 10 12 14 16 18 2002468

101214161820

1970

1952

1981

1996

tC/ha control

tC/h

a cl

earc

ut

Forest Floor C Stocks – Clearcut and Control

Fernow Experimental Forest (WV) Whole tree harvest

0 20 40 60 80 1000

20

40

60

80

100

Lightthin

Heavythin

tC/ha control

tC/h

a tr

eate

d

Soil C Stocks (0-20 cm)-Thinned and Control

0 20 40 60 80 1000

20

40

60

80

100

1981

1952

1970

1996

tC/ha control

tC/h

a cl

earc

ut

Soil C Stocks (0-20 cm)-Clearcut and Control

In summary...

• Thinning treatments may not change the standing C stock over time, but can strongly affect the rate of C accumulation– Thinning method matters!

• Common management treatments may cause a reduction in forest floor C stocks

• Strong evidence that common management treatments do not result in meaningful reductions in SOC stocks or concentrations

Points to ponder• Short-and long-term responses often differ

– This is true both above and below ground• Surface and deep soil layers may respond

differently• Site specific factors may come into play

– Hardwood/softwood types– Soil order

• Existing studies covered “standard” rotation lengths – not biomass harvests or industrial plantations

• Your mileage may vary!

Questions?