Title:Nitrogen and phosphorus addition impact soil N2O emission in a secondary tropical forest of South China

Authors: Faming Wang1§, Jian Li1§, Xiaoli Wang1, Wei Zhang1, Bi Zou1, Deborah A. Neher2, Zhian Li1*.

Affiliations:

1 Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510160, PR China.

2 Department of Plant and Soil Science, University of Vermont, Burlington, VT 05405, U.S.A.

§ The authors have the same contribution to this paper

*Address correspondence to Prof. Zhian Li, Email: ; Phone: 0086-20-37252631; Fax: 0086-20-37252615,

Running title: Interactions of N and P addition on soil N2O emission

Mailing address: Xingke Road 723, Tianhe District, Guangzhou, China. 510650

Number of tables: 2

Number of figures: 5

Number of reference: 55

Figure S1Illustration of all plausible interaction pathways linkage to N2O emission.

Table S1 Results of structural equation modeling of N and P addition effects on soil variablesas illustrated in Fig. 5 A&B. Given are the unstandardized path coefficients (estimates), standard error of regression weight (S.E.), the critical value for the regression weight (C.R.) and the level of significance for the regression weight (P). For more information on the exogenous and endogenous variables and on the model fit, see main text. *** = P< 0.001

Wet seasons SEM:

Estimate / S.E. / C.R. / P
Available P / <--- / Paddition / 13.143 / 2.151 / 6.110 / ***
NO3- / <--- / Naddition / 3.858 / .449 / 8.601 / ***
NH4+ / <--- / Naddition / 1.750 / .313 / 5.592 / ***
NH4+ / <--- / Paddition / .477 / .313 / 1.524 / .128
MBC / <--- / Available P / 5.981 / 3.257 / 1.836 / .066
Nitrification / <--- / NH4+ / -.878 / .448 / -1.960 / .050
N2O / <--- / NO3- / .013 / .002 / 6.633 / ***
N2O / <--- / MBC / .000 / .000 / 2.071 / .038
Nitrification / <--- / NO3 / .181 / .235 / .769 / .442

Dry seasons SEM

Estimate / S.E. / C.R. / P
NO3- / <--- / N addition / 3.326 / .697 / 4.769 / ***
NH4+ / <--- / N addition / 2.357 / .590 / 3.996 / ***
MBC / <--- / NO3- / 7.615 / 4.030 / 1.889 / .059
NH4+ / <--- / P addition / .787 / .525 / 1.500 / .134
Nitrification / <--- / NH4+ / .306 / .245 / 1.251 / .211
Nitrification / <--- / MBC / .013 / .007 / 1.757 / .079
Nitrification / <--- / NO3- / -.619 / .207 / -2.985 / .003
Available P / <--- / P addition / 16.497 / 1.911 / 8.633 / ***
N2O / <--- / MBC / .000 / .000 / .505 / .614
N2O / <--- / NH4+ / .001 / .003 / .362 / .717
N2O / <--- / NO3- / .001 / .002 / .283 / .778
N2O / <--- / Nitrification / .001 / .002 / .297 / .767

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