Ecological Archives A025-143-A3
Iain M. McNicol, Casey M. Ryan, and Mathew Williams. 2015. How resilient are African woodlands to disturbance from shifting cultivation? Ecological Applications 25:2320–2336. http://dx.doi.org/10.1890/14-2165.1
Appendix C. Summary and comparisons of all the statistical models fit to the data.
Table C1. Goodness of fit statistics for each of the statistcal models fit to each data set. Model selection was based on ANOVA tests where models were nested (linear vs. quadratic), or the minimisation of the Akaike Information Critetion (AICc), corrected for small sample sizes, and the residual standard error (RSE) when comparing models fit using linear (‘lm’ function in R) and non-linear (‘nls’) methods. R-sqaured values are provided where it is an acceptable goodness of fit measure. Model forms followed by the letters ‘n.s’ are those which had insignificant parameter estimates and so were excluded from consideration.
Ecosystem component |
Soil type |
Remant trees |
Fitting method (R command) |
Model form |
n |
df |
ANOVA (F, p value) |
AICc |
Residual sum of squares (*104 ) |
RSE |
r² |
Aboveground carbon stocks |
|||||||||||
Sand |
Yes |
OLS (lm) |
Linear |
31 |
29 |
0.19; 0.74 |
238 |
n/a |
10.4 |
0.5 |
|
Yes |
OLS (lm) |
Polynomial |
31 |
28 |
240.53 |
n/a |
10.57 |
0.48 |
|||
Yes |
Robust (rlm) |
Linear |
31 |
29 |
… |
239.2 |
n/a |
10.31 |
… |
||
Clay |
Yes |
OLS (lm) |
Linear |
21 |
19 |
2.64; 0.12 |
151.99 |
n/a |
7.95 |
0.66 |
|
Yes |
OLS (lm) |
Polynomial |
21 |
18 |
152.2 |
n/a |
7.63 |
0.68 |
|||
Yes |
Robust (rlm) |
Linear |
21 |
15 |
… |
152.019 |
n/a |
5.836 |
… |
||
Sand |
No |
OLS (lm) |
Linear |
31 |
29 |
… |
185.19 |
n/a |
4.44 |
0.84 |
|
Clay |
No |
OLS (lm) |
Linear |
21 |
19 |
… |
129.95 |
n/a |
4.706 |
0.74 |
|
Soil carbon stocks |
|||||||||||
-> Topsoil (0 - 5cm) |
Sand |
… |
OLS (lm) |
Linear (n.s) |
31 |
29 |
… |
144.64 |
n/a |
2.308 |
0 |
Clay |
… |
OLS (lm) |
Linear (n.s) |
20 |
18 |
… |
109.48 |
n/a |
3.266 |
0.13 |
|
… |
NLR (nls) |
Negative exponential (n.s) |
20 |
18 |
… |
109.73 |
n/a |
3.286 |
… |
||
-> Subsoil (5 - 30cm) |
Sand |
… |
OLS (lm) |
Linear (n.s) |
31 |
29 |
… |
224.85 |
n/a |
8.415 |
0 |
Clay |
… |
OLS (lm) |
Linear (n.s) |
20 |
18 |
… |
190.39 |
n/a |
24.68 |
0.01 |
|
… |
NLR (nls) |
Negative exponential (n.s) |
20 |
18 |
… |
190.39 |
n/a |
24.68 |
… |
||
Tree species diversity |
|||||||||||
-> Species richness |
Sand |
Yes |
OLS (lm) |
Polynomial |
24 |
21 |
… |
170.12 |
28.52 |
7.25 |
0.46 |
Yes |
NLR (nls) |
Saturation |
24 |
22 |
… |
168.57 |
29.34 |
7.29 |
… |
||
Yes |
NLR (nls) |
Unimodal (ricker) |
24 |
22 |
… |
166.79 |
28.32 |
7.02 |
… |
||
Clay |
Yes |
OLS (lm) |
Polynomial |
17 |
14 |
… |
137.68 |
12.74 |
10.96 |
0.30 |
|
Yes |
NLR (nls) |
Saturation |
17 |
15 |
… |
138.93 |
13.16 |
12.17 |
… |
||
Yes |
NLR (nls) |
Unimodal (ricker) |
17 |
15 |
… |
134.49 |
13.66 |
10.68 |
… |
||
-> Fisher's alpha |
Sand |
Yes |
OLS (lm) |
Polynomial |
24 |
21 |
… |
128.69 |
3.53 |
3.06 |
0.16 |
Yes |
NLR (nls) |
Saturation |
24 |
22 |
… |
125.53 |
3.53 |
2.97 |
… |
||
Yes |
NLR (nls) |
Unimodal (ricker) |
24 |
22 |
… |
128.06 |
3.09 |
3.13 |
… |
||
Clay |
Yes |
OLS (lm) |
Polynomial |
17 |
14 |
… |
107.39 |
1.66 |
4.50 |
0.23 |
|
Yes |
NLR (nls) |
Saturation |
17 |
15 |
… |
108.20 |
1.69 |
4.93 |
… |
||
Yes |
NLR (nls) |
Unimodal (ricker) |
17 |
15 |
… |
104.66 |
1.74 |
4.44 |
… |
||
Tree species composition |
|||||||||||
Sand |
Yes |
OLS (lm) |
Linear |
62 |
60 |
1.01; 0.316 |
-109.02 |
108.37 |
0.096 |
0.29 |
|
Yes |
OLS (lm) |
Polynomial |
62 |
59 |
-107.79 |
108.37 |
0.096 |
0.29 |
|||
Yes |
NLR (nls) |
Logarithmic |
62 |
60 |
… |
-111.48 |
110.39 |
0.095 |
… |
||
Clay |
Yes |
OLS (lm) |
Linear |
26 |
24 |
0.49; 0.486 |
-22.71 |
24.485 |
0.142 |
0.16 |
|
Yes |
OLS (lm) |
Polynomial |
26 |
23 |
-20.46 |
24.485 |
0.143 |
0.15 |
|||
Yes |
NLR (nls) |
Logarithmic (n.s) |
26 |
24 |
… |
-21.26 |
22.81 |
0.146 |
… |
||
Sand |
No |
OLS (lm) |
Linear |
56 |
54 |
0.13; 0.71 |
-94.73 |
100.87 |
0.099 |
0.21 |
|
No |
OLS (lm) |
Polynomial |
56 |
53 |
-92.54 |
100.87 |
0.1 |
0.19 |
|||
No |
NLR (nls) |
Logarithmic |
56 |
54 |
… |
-95.29 |
101.26 |
0.093 |
… |
||
Clay |
No |
OLS (lm) |
Linear |
26 |
24 |
0.24; 0.62 |
-23.35 |
23.33 |
0.14 |
0.19 |
|
No |
OLS (lm) |
Polynomial |
26 |
23 |
-20.81 |
23.33 |
0.142 |
0.16 |
|||
|
|
No |
NLR (nls) |
Logarithmic (n.s) |
26 |
24 |
… |
-22.29 |
21.76 |
0.143 |
… |