Appendix C. Parameter estimates and two-unit support intervals (in brackets) for the most likely models for the 18 soil properties in Ailanthus altissima sites. The “maximum impact” is also given, and represents the predicted maximum increase/decrease over the site mean (a) caused by the presence of Ailanthus altissima trees in a 25-m radius neighborhood.
Parameter |
a [Site 4] |
a [Site 5] |
a [Site 6] |
α |
β |
γ |
b |
c |
Maximum impact |
Bulk density |
0.94 |
0.89 |
0.96 |
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Litter depth |
14.41 |
17.58 |
11.51 |
||||||
Forest floor depth |
17.11 |
18.43 |
15.59 |
||||||
pH |
5.43 |
4.66 |
5.32 |
2 |
1.16 |
0.14 |
-22.52 |
4.91 |
0.72 |
Exchangeable Ca |
171.33 |
69.10 |
120.98 |
1 |
1.08 |
0.18 |
-48.36 |
0.92 |
132.24 |
Exchangeable Mg |
30.31 |
7.54 |
15.45 |
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Exchangeable K |
6.30 |
5.27 |
7.70 |
2 |
1.07 |
0.29 |
-84.56 |
15.84 |
5.71 |
Mass C |
6.80 |
5.92 |
5.61 |
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Mass N |
544.45 |
531.98 |
486.11 |
1 |
2.99 |
0.0009 |
-1258.83 |
2.82 |
555.55 |
C:N |
14.10 |
11.13 |
11.53 |
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NH4+ (µg/g) |
1.68 |
2.51 |
2.13 |
||||||
NO3- (µg/g) |
3.29 |
2.00 |
2.15 |
1 |
2.97 |
0.07 |
2.12 |
1.04 |
|
Microbial biomass C |
649.82 |
700.06 |
929.53 |
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Microbial biomass N |
49.73 |
59.13 |
58.65 |
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Respiration |
11.84 |
15.19 |
18.35 |
||||||
Net N mineralization |
0.85 |
1.04 |
0.97 |
||||||
Net nitrification |
0.87 |
1.09 |
0.98 |
2 |
1.12 |
0.80 |
3.01 |
0.56 |
|
Ca mineralization |
0.009 |
0.002 |
0.006 |
Notes: Maximum impact occurred at Site 4 for pH, exchangeable Ca, Mass N, NO3-, and net nitrification; and at Site 6 for exchangeable K.