Patterns of CO 2 Efflux from Woody Stems in a Red Oak (Quercus rubra) Chronosequence Will Bowman 1...
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Transcript of Patterns of CO 2 Efflux from Woody Stems in a Red Oak (Quercus rubra) Chronosequence Will Bowman 1...
Patterns of CO2 Efflux from Woody Stems in a Red Oak (Quercus rubra) Chronosequence
Will Bowman1 Rob Carson1, Bill Schuster2, and Kevin Griffin1
1Columbia University (New York, NY), 2 Black Rock Forest Consortium (Cornwall, NY)
Respiration in stems and branches is an important, but poorly understood, component of forest carbon budgets.
.
Photosynthesis
Foliar Respiration
Microbial Respiration
Woody Tissue Respiration
Root Respiration
•50-70% of carbon assimilated by photosynthesis is released back to atmosphere by plant respiration
CO2 Fluxes in Forest Ecosystems
Woody Tissue Respiration Background:Sources of Respiratory CO2 Within Stems
Inner Bark
Sapwood Parenchyma
Sapwood-Heartwood Boundary
Woody Tissue Respiration Background: CO2 Efflux-Temperature Response
Equations to describe CO2 Efflux-Temperature plots are typically similar to:
a) R=Ro*e (Eo/Rg)*(1/To-1/Ta) or
b) R=Ro*Q10((T-To)/10)
•Equations to describe CO2 Efflux-Temperature plots are typically similar to:
R=Ro*e (Eo/Rg)*(1/To-1/Ta) or
R=Ro*Q10((T-To)/10)
Woody Tissue Respiration Background:Recent evidence suggests that sap flow in tree stems strongly influences the rate of CO2 efflux to the atmosphere (McGuire and Teskey 2002; Teskey and McGuire, 2004; Bowman et al, in prep).
Woody Tissue Respiration Background:Recent evidence suggests that sap flow in tree stems strongly influences the rate of CO2 efflux to the atmosphere (McGuire and Teskey 2002; Teskey and McGuire, 2004; Bowman et al, in prep).
•Residuals tended to become more negative, i.e. there was less CO2 efflux
than would be predicted from sapwood temperature alone, in the late morning. This decline in the magnitude of residuals corresponded to the onset of sap flow.
•This study aims find consistent linkages between amount of respiratory CO2 within stems, the
transpirational and anatomical barriers to CO2 diffusion
to the atmosphere, and the actual CO2 diffusing from
tree stems.
Study Site: A chronosequence of Q. rubra stands located in Black Rock Forest (Cornwall, NY)
Black Rock Forest:
•Q. rubra and Q. prinus account for ~60% of forest basal area. Acer rubrum comprises 8% of basal area
•1,500 ha scientific preserve
•located in Hudson Highlands province
•41° 24´ N 74° 01 ´ W
•Elevation 110 – 450 above sea level
Study Site: A chronosequence of Q. rubra stands located in Black Rock Forest (Cornwall, NY)
•Detailed records of logging at BRF enabled identification of four stands ranging in age from 35-130 yrs.
Study Site: A chronosequence of Q. rubra stands located in Black Rock Forest (Cornwall, NY)
•Data was collected in two of these stands between mid June and late July 2004.
Age (Yrs)
DBH
(cm ± SD)
Height (m ± SD)
Stand LAI (m2/m2)
37 14.84 (± 0.97)
14.01 (± 0.67 )
2.15
91 38.28 (± 1.71 )
19.92 (± 0.73 )
2.67
Study Methods:
•Continuous measurements of CO2 efflux were made in 8 Q. rubra trees from each stand for 7-10 days.
Study Methods:
•Continuous measurements of CO2 efflux were made in 8 Q. rubra trees from each stand for 7-10 days.
•Physiological and anatomical characteristics that 1) represent the amount of CO2 within the stem or 2) may influence diffusion of CO2 from the stem were also measured:
•Sap Velocity
•CO2 concentration within the xylem
Study Methods:
•Continuous measurements of CO2 efflux were made in 8 Q. rubra trees from each stand for 7-10 days.
•Physiological and anatomical characteristics that 1) represent the amount of CO2 within the stem or 2) may influence diffusion of CO2 from the stem were also measured:
•Sap Velocity
•CO2 concentration within the xylem
•Respiratory potential of excised inner bark and sapwood tissues
Study Methods:
•Continuous measurements of CO2 efflux were made in 8 Q. rubra trees from each stand for 7-10 days.
•Physiological and anatomical characteristics that 1) represent the amount of CO2 within the stem or 2) may influence diffusion of CO2 from the stem were also measured:
•Sap Velocity
•CO2 concentration within the xylem
•Respiratory potential of excised inner bark and sapwood tissues
•Diameter Growth Rate
•Bark Thickness and Sapwood Density
Study Methods:
•Continuous measurements of CO2 efflux were made in 8 Q. rubra trees from each stand for 7-10 days.
•Physiological and anatomical characteristics that 1) represent the amount of CO2 within the stem or 2) may influence diffusion of CO2 from the stem were also measured.
•‘Concentration Gradient’ framework for stem CO2 efflux involving processes that influence either 1) the magnitude of the concentration gradient between the stem interior and the atmosphere or 2) the resistance to CO2 diffusion across this gradient
Results:
•CO2 efflux was strongly related to temperature in all sampled trees.
•CO2 efflux rates were not significantly different between 30- and 90-yr old stands.
0
2
4
6
8
10 15 20 25 30
Sapwood Temperature (oC)
Ste
m C
O2 E
fflu
x
(
mo
les
CO
2 m
-2 s
-1)
Results:
•A diel hysteresis in the CO2 efflux data was commonly observed in both stands.
0
1
2
3
4
8 12 16 20 24
Sapwood Temperature (oC)
Ste
m C
O2 E
fflu
x
(
mo
les
CO
2 m
-2 s
-1)
Results:
•A diel hysteresis in the CO2 efflux data was commonly observed in
both stands.
0
1
2
3
4
8 12 16 20 24
Sapwood Temperature (oC)
Ste
m C
O2 E
fflu
x
(
mo
les
CO
2 m
-2 s
-1)
Late afternoon
Early morning
0
0.02
0.04
0.06
0.08
0.1
0.12
1500 1100 700 300
Time
0
5
10
15
20
25
Sap VelocitySapw ood TemperatureXylem CO2 [ ]
Xyl
em C
O2 [
] (
%)
Sap
woo
d T
emp
(o C
)
Sap
Vel
ocit
y (m
m s
-1)
Results:
•The internal CO2 [ ] in the xylem exhibited a diel pattern caused by sap flow. This pattern indicates that dissolved respiratory CO2 is transported to upper portions of the tree in the transpiration stream.
•Avg. maximum sap velocity and avg. internal CO2 [ ] were calculated for comparisons with stem CO2 efflux
Xyl
em C
O2 [
] (
%)
Sap
woo
d T
emp
(o C
)
Sap
Vel
ocit
y (m
m s
-1)
0
0.01
0.02
0.03
0.04
0.05
0.06
1 121 241 361
Time
0
5
10
15
20
25
30
Sap VelocitySapw ood TemperatureXylem CO2 [ ]
Sap
Vel
ocit
y (m
m s
-1)
Xyl
em C
O2 [
] (
%)
Sap
woo
d T
emp
(o C
)
Results:
•Occasionally, the internal CO2 [ ] in the xylem more closely followed stem sapwood temperature. This was only seen in the younger trees.
Results:
•CO2 efflux rates were negatively correlated to average maximum sap flow rates. This is also consistent with the transport of respiratory CO2 in the
transpiration stream.
y = -6.243x + 4.958R2 = 0.42
0
1
2
3
4
5
6
0 0.1 0.2 0.3 0.4 0.5
Avg. Maximum Sap Velocity (mm s-1)
CO
2 E
fflu
x at
20
oC
( m
oles
CO
2 m
-2 s
-1)
Results:
•This trend was observed in both 35- and 90-yr old tree stands.
y = -8.4282x + 4.9824R2 = 0.5421
y = -6.4995x + 5.2829R2 = 0.5229
0
1
2
3
4
5
6
0 0.1 0.2 0.3 0.4 0.5
Avg. Maximum Sap Velocity (mm s-1)
CO
2 E
fflu
x at
20
oC
( m
oles
CO
2 m
-2 s
-1)
35 yr old Stand90 yr old Stand
Results:
•CO2 efflux was positively correlated to the xylem CO2 [ ] in the 35 yr old stand.
y = 0.1405x + 2.3016R2 = 0.5758
0
1
2
3
4
5
6
0 5 10 15 20
Avg. Xylem CO2 [ ] (%)
CO
2 E
fflu
x at
20
oC
(
mo
les
CO
2 m
-2 s
-1)
35 yr old Stand
Results:
•As hypothesized, CO2 efflux was positively correlated to the xylem CO2 [ ] in the 35 yr old stand.
…but not in the 90 yr old stand.
y = 0.1405x + 2.3016R2 = 0.5758
0
1
2
3
4
5
6
0 5 10 15 20
Avg. Xylem CO2 [ ] (%)
CO
2 E
fflu
x at
20
oC
(
mo
les
CO
2 m
-2 s
-1)
35 yr old Stand90 yr old Stand
Results:
•Respiratory potential of extracted wood was significantly (p < .05) higher in inner bark compared to sapwood. No differences were observed between the stands and no correlations were found with stem CO2 efflux or internal CO2 [ ].
a
a
bb
a
a
bb
0
0.4
0.8
1.2
1.6
2
35 yr Stand 90 yr Stand
Res
pir
ato
ry P
ote
nti
al (
nm
ole
s O
2 g
-1 s
-1)
Inner Bark
Sapwood
a
a
bb
Results:
•Respiratory potential of extracted wood was significantly (p < .05) higher in inner bark compared to sapwood. No differences were observed between the stands and no correlations were found with stem CO2 efflux or internal CO2 [ ].
•Also, no correlations were observed between stem CO2 efflux rate and diameter growth or the anatomical traits of wood (bark thickness, wood density).
a
a
bb
0
0.4
0.8
1.2
1.6
2
35 yr Stand 90 yr Stand
Res
pir
ato
ry P
ote
nti
al (
nm
ole
s O
2 g
-1 s
-1)
Inner Bark
Sapwood
a
a
bb
General Conclusions:
•Stem CO2 efflux was negatively correlated with sap velocity in both stands. This finding, along with other recent studies, suggests that interactions between CO2 efflux and stem hydraulics are commonplace in forest trees.
•The internal CO2 [ ] of xylem was also predictive of CO2 efflux in the younger tree stand, but not in the older stand. Perhaps, this indicates that CO2 efflux in young (with thin bark) trees is driven by the magnitude of the concentration gradient between the tree’s interior and the atmosphere. While in older trees (with thick bark), CO2 efflux may also be heavily influenced by factors that dictate the permeability of wood to CO2 diffusion.
•These interactions between CO2 efflux and sap velocity create great uncertainty about the sources and destinations of respiratory CO2 with unknown ramifications for whole-tree carbon budgets.
Acknowledgements:
•John Brady
•Vic Engel
•Howard Fung
•Matt Munson
•Margaret Barbour
•Funding provided from the Black Rock Forest Consortium and a National Science Foundation GK12 graduate fellowship.