Description presentación oral en el workshop REMEDIA 2012 en la temática de mitigación de GEi suelo-planta

1. Remedia workshop.
Bilbao, 8-9 Marzo 2012
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

2. Carbon stock change of Spanish forests. Remedia workshop 2012 #2
INTRODUCTION (i):
1) NPP is a major driver of
the global C balance and of
the interannual growth rate
of atmospheric CO2.
Houghton, AREPS 2007

3. Carbon stock change of Spanish forests. Remedia workshop 2012 #3
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

4. Carbon stock change of Spanish forests. Remedia workshop 2012 #4
INTRODUCTION (iii):
3) The trends in C
accumulation are less clear
(and less studied) in water
limited systems.
Zhao & Running, Science 2010
Carnicer et al. PNAS 2011

5. Carbon stock change of Spanish forests. Remedia workshop 2012 #5
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.

6. Carbon stock change of Spanish forests. Remedia workshop 2012 #6
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 RAINFALL TREND
Significant in Significant in
92% of cells < 5% of cells
Temperature trend (ºC)
Relative precipitation trend (%)
[0.00, 0.33)
[-21.0, -17.5)
[0.33, 0.67)
[-17.5, -14.0)
[0.67, 1.00) [-14.0, -10.5)
[1.00, 1.33) [-10.5, -7.0)
[1.33, 1.67) [-7.0, -3.5)
[1.67, 2.00] [-3.5, 0.0]

7. Carbon stock change of Spanish forests. Remedia workshop 2012 #7
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):

8. Carbon stock change of Spanish forests. Remedia workshop 2012 #8
METHODS:
National Forest Inventory of Spain
• 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.
Above- and belowground
(allometric equations from
Calculation of C stock change Montero et al. 2005)
(1) Increment due to tree growth and ingrowth
C stock change
(2) Decrease due to mortality
Statistical modelling
Using GLM and GLZ, as a function of climate and forest structure

9. Carbon stock change of Spanish forests. Remedia workshop 2012 #9
RESULTS. Distribution of growth and mortality (in Mg C ha-1 yr-1):
GROWTH RATE MORTALITY RATE
Growth rate Mortality rate
[0.0, 0.5) [0.0, 0.1)
[0.5, 1.0) [0.1, 0.2)
[1.0, 1.5) [0.2, 0.3)
[1.5, 2.0) [0.3, 0.4)
[2.0, 2.5) [0.4, 0.5)
[2.5, 3.0) [0.5, 0.6)
[3.0, 3.5) [0.6, 0.7)
[3.5, 4.0] [0.7, 0.8]

10. Carbon stock change of Spanish forests. Remedia workshop 2012 #10
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) Overall average:
[1.5, 2.0) ∼ 1.4 Mg C ha-1 yr-1
[2.0, 2.5)
[2.5, 3.0]

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RESULTS. Determinants of C stock change: A
-1 -1 )
g C ha yr
5
4
C stock Tree density
k change (M
3
2
)
ha -1
150
+
1
+
100
C
0
Mg
C stoc
2500 50
2000
(
1500
ck
1000
500
Tree
sto
d ensit
y
on
(tree
s ha -1
rb
)
+
Ca
Management CARBON
ACCUMULATION B
-1 -1 )
+
g C ha yr
- 3
ck change (M
2
100
Water
)
(%
1
Temperature 50
y
ilit
0
availability
0
ab
trend
C sto
-50
il
1.0
va
Tem 0.5
ra
pera -100
0.0
ate
ture
trend
W
(ºC)

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RESULTS. Effects of previous forest management:
Unmanaged
Managed
C stock change (Mg C ha-1 yr-1)
1.8 1.8
Growth rate (Mg C ha-1 yr-1)
A B
1.6 1.6
1.4 1.4
1.2 1.2
1.0 1.0
0.5 1.0 1.5 2.0 0.5 1.0 1.5 2.0
Temperature trend (ºC) Temperature trend (ºC)

13. Carbon stock change of Spanish forests. Remedia workshop 2012 #13
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.

14. Carbon stock change of Spanish forests. Remedia workshop 2012 #14
Thank you! & questions?

15. 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 ***
-1
ln(Tree density (trees ha ) 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.

16. 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 ***
Management( = true) - - - - n.s.
C stock (Mg C ha-1) 1.81E-02 ± 6.63E-04 27.288 <0.001 ***
-1
Tree density (trees ha ) 3.01E-04 ± 2.92E-05 10.286 <0.001 ***
Water availability 6.91E-03 ± 5.49E-04 12.584 <0.001 ***
Temperature trend (ºC) -1.83E-01 ± 4.74E-02 -3.854 <0.001 ***
C stock X Tree density - - - - n.s.
Water availability X Temperature trend - - - - n.s.
Management (=true) X Temperature trend - - - - n.s.
Degrees of freedom 20020
BIC 22001
AIC 21969
Deviance explained 0.102
(b)
Effects Estimate T-value Pr(>|t|) Sign.
Intercept - - - - n.s.
Management( = true) - - - - n.s.
ln(C stock (Mg C ha-1)) - - - - n.s.

17. 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)
Effects Estimate T-value Pr(>|t|) Sign.
Intercept 6.55E-01 ± 3.51E-02 18.644 <0.001 ***
Management( = true) - - - - n.s.
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 ***
Water availability 1.48E-02 ± 6.82E-04 21.781 <0.001 ***
Temperature trend (ºC) -2.91E-01 ± 2.96E-02 -9.823 <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 **
Degrees of freedom 22468
BIC 64326
Adjusted-R² 0.4062
F-value 1923
p-value <0.001
Significant. codes: ‘***’ 0.001; ‘**’ 0.01; n.s. not significant.