Vayreda

Recent climate changes interact

with stand structure and management

to determine changes in tree carbon stocks

in Spanish forests

Javier Retana, Jordi Vayreda,

Jordi Martínez-Vilalta & Marc Gracia

Remedia workshop. Bilbao, 8-9 Marzo 2012

Carbon stock change of Spanish forests. . Remedia workshop 2012Remedia workshop 2012 # #22

Houghton, AREPS 2007

INTRODUCTION (i):

1) NPP is a major driver of

the global C balance and of

the interannual growth rate

of atmospheric CO2.


INTRODUCTION (ii):

2a) Most temperate forests are accumulating C;

2b) And are expected to continue doing so.

Carbon sink and sources (Pg C yr-1) in the word’s forests. Pan et al 2011


Zhao & Running, Science 2010

Carnicer et al. PNAS 2011

INTRODUCTION (iii):

3) The trends in C

accumulation are less clear

(and less studied) in water

limited systems.


OBJECTIVES of the study:

(1) to analyze the factors determining the spatial patterns

of tree C stock change of forests and its components

(i.e., growth and mortality) in Spanish forests;

(2) to evaluate how the recent trends in climate have

affected C stock changes along a water availability

gradient; and

(3) to determine whether or not forest management has

contributed to mitigate the effects of recent warming.


Advantages of the study system:

• Spain has a wide range of climatic conditions.• Most forests in Spain are Mediterranean (and limited by water).• The climate is getting warmer (and drier) [over a 30 yr period]:

Temperature trend (ºC)

[0.00, 0.33)

[0.33, 0.67)

[0.67, 1.00)

[1.00, 1.33)

[1.33, 1.67)

[1.67, 2.00]

Relative precipitation trend (%)

[-21.0, -17.5)

[-17.5, -14.0)

[-14.0, -10.5)

[-10.5, -7.0)

[-7.0, -3.5)

[-3.5, 0.0]

TEMPERATURE TREND RAINFALL TREND

Significant in < 5% of cells

Significant in 92% of cells


DATA SOURCES:

• Climate. Digital Climatic Atlas of the Iberian Peninsula (Ninyerola et al. 2005).

• Climate trends. Center for Climatic Research, University of Delaware

(Matsuura & Willmott 2009).

• Forest structure and C stock change. National Forest Inventory of Spain

(IFN2 & IFN3; Villaescusa & Díaz, 1998; Villanueva 2005):


METHODS:

• Scheme including ~ 90,000 circular plots (ca. 1 plot/km2 of forest).

• Plots surveyed in 1986-1996 (IFN2) and resurveyed 1997-2008 (IFN3).

• Not included: - Crops and species used exclusively for wood production

- Plots with signs of disturbances (e.g., fire) or management

• Final dataset included 22,477 resampled plots.

Using GLM and GLZ, as a function of climate and forest structure

(1) Increment due to tree growth and ingrowth

(2) Decrease due to mortality C stock change

Above- and belowground(allometric equations from

Montero et al. 2005)

Statistical modelling

Calculation of C stock change

National Forest Inventory of Spain


RESULTS. Distribution of growth and mortality (in Mg C ha-1 yr-1):

Growth rate

[0.0, 0.5)

[0.5, 1.0)

[1.0, 1.5)

[1.5, 2.0)

[2.0, 2.5)

[2.5, 3.0)

[3.0, 3.5)

[3.5, 4.0]

Mortality rate

[0.0, 0.1)

[0.1, 0.2)

[0.2, 0.3)

[0.3, 0.4)

[0.4, 0.5)

[0.5, 0.6)

[0.6, 0.7)

[0.7, 0.8]

GROWTH RATE MORTALITY RATE


RESULTS. Distribution of tree C stock change (in Mg C ha-1 yr-1):

Carbon stock change

[-1.0, -0.5)

[-0.5, 0.0)

[0.0, 0.5)

[0.5, 1.0)

[1.0, 1.5)

[1.5, 2.0)

[2.0, 2.5)

[2.5, 3.0]

Overall average: Overall average: 1.4 Mg C ha1.4 Mg C ha-1-1 yr yr-1-1


RESULTS. Determinants of C stock change:

0

1

2

3

4

5

50

100

150

5001000

15002000

2500

C s

tock

cha

nge

(Mg

C h

a-1 y

r-1)

Car

bon

stoc

k (M

g C

ha

-1 )

Tree density (trees ha-1)

A

0

1

2

3

-100

-50

0

50

100

0.0

0.51.0

C s

tock

cha

nge

(Mg

C h

a-1 y

r-1)

Wat

er a

vaila

bilit

y (%

)


B

CARBONACCUMULATION

C stock Tree density

Management

Wateravailability

Temperaturetrend

+ +

+

+

-


RESULTS. Effects of previous forest management:

A


0.5 1.0 1.5 2.0

Gro

wth

rat

e (M

g C

ha-1

yr-1

)

1.0

1.2

1.4

1.6

1.8

UnmanagedManaged

B


0.5 1.0 1.5 2.0C s

tock

cha

nge

(Mg

C h

a-1 y

r-1)

1.0

1.2

1.4

1.6

1.8


CONCLUSIONS:

(1) Spanish forests are accumulating C at a rate of 1.4 Mg C ha-1 yr-1.

(2) Forest structural variables are the main determinants of forest

growth and tree C stock change.

(3) Spatial variation in mortality (in terms of C loss) was mostly driven by

differences in growth rate, and was consistent with self-thinning

dynamics related to the recent abandonment of forest management.

(4) Water availability was positively related to growth and C

accumulation.

(5) Recent warming has reduced growth rate and C accumulation,

especially in wet areas.

(6) The negative effect of warming on forest C accumulation disappears if

only managed stands are considered, emphasizing the potential of

forest management to mitigate the effects of climate change.


Thank you! & questions?Thank you! & questions?

Table 1. Summary of the best model (in terms of BIC) of growth rate (Mg C ha-1 yr-1; log transformed) as a function of plot variables (all forest types combined)

Effects Estimate T-value Pr(>|t|) Sign.

Intercept -6.29E+00 ± 1.26E-01 -49.840 <0.001 ***

Management( = true) - - - - n.s.

ln(C stock (Mg C ha-1)) 1.07E+00 ± 3.68E-02 28.956 <0.001 ***

ln(Tree density (trees ha-1) 8.80E-01 ± 2.06E-02 42.655 <0.001 ***

Water availability 1.00E-02 ± 3.80E-04 26.354 <0.001 ***

Temperature trend (ºC) -1.90E-01 ± 1.64E-02 -11.575 <0.001 ***

ln(C stock) X ln(Tree density) -1.12E-01 ± 5.90E-03 -19.004 <0.001 ***

Water availability X Temperature trend -5.21E-03 ± 3.64E-04 -14.329 <0.001 ***

Management (=true) X Temperature trend 9.88E-02 ± 2.29E-02 4.314 <0.001 ***

Degrees of freedom 22468

BIC 37794

Adjusted-R² 0.622

F-value 4627

p-value <0.001

Significant. codes: ‘***’ 0.001; ‘**’ 0.01; n.s. not significant.

Table 2. Summary of the best models (in terms of BIC) of (a) mortality occurrence (dichotomic) and (b) mortality rate (Mg C ha-1 yr-1; log transformed) as a

function of plot variables (all forest types combined).

(a)

Effects Estimate Z-value Pr(>|t|)

Sign.

Intercept -1.44E+00 ± 5.99E-02 -24.088 <0.001 ***


C stock (Mg C ha-1) 1.81E-02 ± 6.63E-04 27.288 <0.001 ***

Tree density (trees ha-1) 3.01E-04 ± 2.92E-05 10.286 <0.001 ***



C stock X Tree density - - - - n.s.

Water availability X Temperature trend - - - - n.s.

Management (=true) X Temperature trend - - - - n.s.


BIC 22001

AIC 21969

Deviance explained 0.102

(b)


Intercept - - - - n.s.


ln(C stock (Mg C ha-1)) - - - - n.s.

Table 3. Summary of the best model (in terms of BIC) of C stock change (Mg C ha-1 yr-1) as a

function of plot variables (all forest types combined)


Intercept 6.55E-01 ± 3.51E-02 18.644 <0.001 ***


C stock (Mg C ha-1) 1.15E-02 ± 3.78E-04 30.499 <0.001 ***

Tree density (trees ha-1) 1.39E-03 ± 2.24E-05 61.920 <0.001 ***



C stock X Tree density -6.18E-06 ± 3.41E-07 -18.146 <0.001 ***

Water availability X Temperature trend -7.59E-03 ± 6.54E-04 -11.600 <0.001 ***

Management (=true) X Temperature trend 1.18E-01 ± 4.13E-02 2.847 <0.01 **


BIC 64326

Adjusted-R² 0.4062

F-value 1923

p-value <0.001

Significant. codes: ‘***’ 0.001; ‘**’ 0.01; n.s. not significant.

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