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Finzi et al. 10.1073/pnas.0706518104. |
Table 2. The mean (±1 SE) response of stem growth to N fertilization under present-day
concentrations of atmospheric CO2
|
Site |
Species |
Application rate, kg•ha-1•yr-1 |
Control |
% +N Fertilizer |
Stimulation, % |
Ref. |
|
DUKE |
P. taeda |
110 |
2.25 (0.08) |
2.86 (0.11)** |
27 |
1 |
|
ORNL |
L. styraciflua |
200 |
1.46 (0.11) |
2.00 (0.14)** |
38 |
* |
|
EURO |
P. alba |
251 |
0.49 (0.05) |
0.50 (0.02)ns |
+2 |
2 |
|
P. nigra |
251 |
0.55 (0.07) |
0.56 (0.04)ns |
+3 |
||
|
P. x euramericana |
251 |
0.79 (0.07) |
0.78 (0.06)ns |
-1 |
Data show that tree growth at the ORNL and Duke sites is N-limited, whereas tree growth at the POP-EUROFACE (EURO) site is not N-limited. The units for tree growth at the Duke and ORNL sites are cm2•m-2•yr-1 (basal area increment) and at the POP-EUROFACE site, g•g-1•yr-1 (relative growth rate). Data from the Duke forest are average growth rates for the 1999 and 2000 growing seasons. Data from for the ORNL site are average growth rates for the 2004 and 2005 growing seasons. Data from the POP-EUROFACE site are average growth rates for the 2002-2004 growing seasons. Significant differences in the growth rate of trees in control and fertilized plots are indicated by **, P < 0.01. NS, not significant.
*C.M.I. and R.J.N., unpublished data.
1. Oren R, Ellsworth DS, Johnsen KH, Phillips N, Ewers BE, Maier C, Schafer KVR, McCarthy H, Hendrey G, McNulty SG, Katul GG (2001) Nature 411:469-472.
2. Liberloo M, Calfapietra C, Lukac M, Godbold D, Luos ZB, Polle A, Hoosbeek MR, Kull O, Marek M, Raines C, et al. (2006) Global Change Biol 12:1094-1106.
Table 3. Uptake (g•m-2•yr-1) and distribution of N (%) into wood, foliage, and fine roots at the four forest FACE research sites
|
Rhinelander |
Duke |
ORNL |
EURO-FACE |
|||||
|
Component |
Amb. |
Elev. |
Amb. |
Elev. |
Amb. |
Elev. |
Amb. |
Elev. |
|
Uptake |
||||||||
|
Wood |
1.01 |
1.28 |
0.94 |
1.26 |
2.38 |
2.70 |
17.08 |
17.33 |
|
(0.07) |
(0.09) |
(0.06) |
(0.08) |
(0.08) |
(0.10) |
(1.23) |
(1.11) |
|
|
Foliage |
3.54 |
5.63*** |
3.07 |
3.38 |
3.60 |
3.39 |
8.64 |
7.43 |
|
(0.21) |
(0.27) |
(0.27) |
(0.31) |
(0.24) |
(0.17) |
(0.70) |
(0.68) |
|
|
Fine root |
0.76 |
1.26*** |
0.86 |
1.15 |
3.14 |
5.95* |
1.76 |
2.46* |
|
(0.04) |
(0.07) |
(0.04) |
(0.03) |
(0.49) |
(0.70) |
(0.22) |
(0.29) |
|
|
Total |
5.31 |
8.17*** |
4.86 |
5.79* |
9.12 |
12.04** |
27.48 |
27.22 |
|
(0.29) |
(0.36) |
(0.49) |
(0.43) |
(0.49) |
(0.63) |
(1.84) |
(1.81) |
|
|
Distribution |
||||||||
|
Wood |
18.7 |
15.7 |
20.2 |
22.6 |
27.6 |
23.3 |
62.4 |
64.2 |
|
(0.7) |
(0.9) |
(2.7) |
(5.5) |
(4.3) |
(4.1) |
(1.7) |
(1.6) |
|
|
Foliage |
66.6 |
68.8 |
62.4 |
58.1* |
40.4 |
29.1* |
31.5 |
26.8 |
|
(1.0) |
(0.8) |
(5.1) |
(6.1) |
(6.4) |
(5.4) |
(1.6) |
(1.2) |
|
|
Fine root |
14.7 |
15.5 |
17.4 |
19.3* |
32.0 |
47.6* |
6.1 |
9.0* |
|
(0.8) |
(0.7) |
(4.5) |
(6.0) |
(8.7) |
(8.8) |
(0.6) |
(0.7) |
|
Values derived from forest plots exposed to present-day concentrations of atmospheric CO2 are indicated by the abbreviation "Amb." (i.e., ambient levels of CO2 in the earth's atmosphere). Values derived from forest plots exposed to elevated concentrations of atmospheric CO2 are indicated by the abbreviation "Elev." (i.e., elevated levels of CO2). Within a component and research site, levels of significance are given as *, P < 0.05; **, P < 0.01; and ***, P < 0.001.
Table 4. A summary of the statistical analysis for the five response variables presented in this data synthesis
|
Dependent variable |
Independent variable |
Research site |
|||||||
|
Rhinelander |
Duke |
ORNL |
POP-EUROFACE |
||||||
|
F |
P |
F |
P |
F |
P |
F |
P |
||
|
N uptake |
CO2 |
71.2 |
<0.001 |
6.1 |
<0.05 |
9.73 |
<0.01 |
0.02 |
0.879 |
|
Year |
14.8 |
<0.001 |
9.8 |
<0.001 |
0.66 |
0.683 |
47.92 |
<0.01 |
|
|
CO2 ´ Year |
1.5 |
0.24 |
0.22 |
0.96 |
0.24 |
0.959 |
0.11 |
0.746 |
|
|
NUE |
CO2 |
0.28 |
0.59 |
1.39 |
0.25 |
1.24 |
0.28 |
38.9 |
<0.001 |
|
Year |
1.93 |
0.16 |
5.05 |
<0.01 |
0.56 |
0.76 |
10.1 |
<0.01 |
|
|
CO2 ´ Year |
0.70 |
0.50 |
0.46 |
0.83 |
0.23 |
0.96 |
0.09 |
0.77 |
|
|
N content |
CO2 |
34.0 |
<0.001 |
5.15 |
<0.05 |
13.8 |
<0.01 |
0.09 |
0.77 |
|
Year |
23.5 |
<0.001 |
1.61 |
0.18 |
51.6 |
<0.001 |
117.0 |
<0.001 |
|
|
CO2 ´ Year |
0.56 |
0.58 |
0.09 |
0.99 |
0.75 |
0.61 |
0.02 |
0.90 |
|
|
N productivity |
CO2 |
13.7 |
<0.001 |
21.7 |
<0.001 |
34.2 |
<0.001 |
25.3 |
<0.001 |
|
Year |
3.3 |
0.06 |
28.4 |
<0.001 |
11.78 |
<0.001 |
99.2 |
<0.001 |
|
|
CO2 ´ Year |
0.9 |
0.41 |
0.64 |
0.70 |
0.71 |
0.64 |
0.24 |
0.63 |
|
|
MRT |
CO2 |
16.1 |
<0.001 |
1.4 |
0.25 |
7.64 |
<0.05 |
0.52 |
0.48 |
|
Year |
2.7 |
0.08 |
28.9 |
<0.001 |
1.69 |
0.17 |
46.9 |
<0.001 |
|
|
CO2 ´ Year |
6.59 |
<0.01 |
0.50 |
0.80 |
0.14 |
0.99 |
0.19 |
0.67 |
|
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