Article Figures & Data
Figures
- Figure 1.
Illustration of dendrometric and habitat factors measured in this study. Except for open soil area which was measured in square metres, all dimensional variables were measured in metres.
- Figure 2.
Presence of (a) protruding root and (b) protruding flare indicated by yellow arrows. The protruding parts were visually detectable by woody tissues reaching the border between the open soil area and paving materials.
Tables
- Table 1.
Descriptive statistics of (a) dendrometric variables and (b) habitat variables of 14 tree species. Diameter at breast height, trunk flare diameter, and tree height were abbreviated as DBH, TFD, and H.
DBH (m) TFD (m) H (m) Lean (degree) Mean Median SD Mean Median SD Mean Median SD Mean Median SD (a) Aleurites moluccanus 0.285def 0.270 0.089 0.632c 0.486 0.430 10.33cde 9.94 2.82 6.2abcd 5.4 3.8 Archontophoenix alexandrae 0.124ab 0.116 0.033 0.254ab 0.227 0.074 5.15a 4.01 2.70 3.0a 2.2 2.3 Bombax ceiba 0.329ef 0.314 0.111 0.653c 0.548 0.336 10.06bcd 9.49 3.09 4.3ab 4.0 3.2 Casuarina equisetifolia 0.254de 0.261 0.108 0.636c 0.602 0.338 13.45f 13.13 4.94 9.0def 7.8 6.2 Cinnamomum burmannii 0.218cd 0.225 0.074 0.648c 0.601 0.340 8.39b 8.24 2.55 10.2ef 9.7 5.9 Delonix regia 0.337f 0.339 0.104 0.956d 0.881 0.573 9.75bcd 9.34 2.93 7.7cde 6.3 5.8 Ficus altissima 0.754h 0.665 0.436 2.504f 2.468 0.741 10.83de 10.28 2.47 6.5bcd 5.0 5.8 Ficus microcarpa 0.467g 0.434 0.182 1.797e 1.718 0.523 11.94ef 11.50 3.62 10.8ef 8.4 8.7 Lagerstroemia speciosa 0.129ab 0.130 0.051 0.224a 0.209 0.111 5.34a 5.26 1.46 6.1abcd 4.9 4.8 Melaleuca cajuputi 0.205bcd 0.211 0.110 0.449bc 0.389 0.353 8.91bc 8.73 3.19 6.3abcd 5.2 4.8 Michelia × alba 0.163bc 0.170 0.080 0.223a 0.217 0.097 8.31b 8.22 3.48 12.1f 9.5 10.8 Photinia serratifolia 0.073a 0.064 0.037 0.128a 0.100 0.087 5.02a 4.43 1.62 4.5abc 3.3 4.5 Spathodea campanulata 0.250de 0.229 0.108 0.501c 0.413 0.301 8.95bc 8.58 3.25 7.6cde 6.5 5.8 Xanthostemon chrysanthus 0.068a 0.062 0.024 0.124a 0.111 0.049 4.81a 4.75 0.82 4.0ab 3.3 3.1 Pavement widtd (m) Open soil area (m2) Setback (m) Pavement material Mean Median SD Mean Median SD Mean Median SD Brick Concrete Total (b) Aleurites moluccanus 3.467ab 3.300 1.286 1.312cde 1.030 1.056 0.376a 0.240 0.324 50 29 79 Archontophoenix alexandrae 5.967d 3.680 3.770 0.601ab 0.520 0.311 1.100abc 0.885 1.014 54 4 58 Bombax ceiba 4.007abc 2.970 2.140 1.323cde 1.382 0.670 1.047abc 0.505 1.794 71 1 72 Casuarina equisetifolia 9.168f 9.555 2.012 1.590de 1.563 0.297 2.864e 2.135 1.741 118 0 118 Cinnamomum burmannii 5.090cd 5.245 2.010 1.120bcd 1.081 0.552 1.998d 1.293 1.627 58 10 68 Delonix regia 5.082cd 4.010 1.985 1.689e 1.160 1.290 1.907d 1.920 1.196 61 13 74 Ficus altissima 7.277e 7.110 1.373 5.859g 5.937 2.638 3.894f 4.170 1.277 58 1 59 Ficus microcarpa 4.516bc 3.535 2.571 3.042f 2.781 1.522 1.487bcd 0.533 2.099 74 52 126 Lagerstroemia speciosa 5.115cd 4.260 2.182 0.486a 0.372 0.439 1.951d 1.250 1.618 32 43 75 Melaleuca cajuputi 4.057abc 3.465 2.158 0.859abc 0.665 0.622 0.845abc 0.628 0.938 72 50 122 Michelia × alba 3.530ab 3.480 0.183 0.854abc 0.874 0.160 2.127de 2.190 0.279 0 31 31 Photinia serratifolia 4.524bc 3.640 2.019 0.834abc 0.791 0.308 1.610cd 1.068 1.404 41 15 56 Spathodea campanulata 3.177a 2.780 1.305 0.649ab 0.464 0.409 0.709ab 0.565 0.539 60 38 98 Xanthostemon chrysanthus 4.589bc 4.155 1.482 0.842abc 0.814 0.326 1.353bcd 0.963 1.164 52 12 64 Lower-case letters indicate results of Games-Howell comparisons using species as a fixed factor. Mean values were ranked in ascending alphabetical order. Values with the same letter indicate statistical homogeneity in their distributions.
- Table 2.
Species-specific prediction models of trunk flare diameter (TFD) using diameter at breast height (DBH) with (a) all trees under each individual species and (b) only trees with protruding roots and/or flares.
Intercept Regression coefficient of DBH R2 b0 SE b1 SE CILOW CIup (a) All trees under each individual species A. moluccanus 0.563 −0.406 0.108 3.645 0.361 2.925 4.365 A. alexandrae 0.804 0.005 0.017 2.004 0.131 1.742 2.266 B. ceiba 0.626 −0.136 0.076 2.399 0.219 1.962 2.836 C. equisetifolia 0.781 −0.066 0.037 2.766 0.135 2.498 3.304 C. burmannii 0.644 −0.160 0.077 3.715 0.336 3.044 4.386 D. regia 0.655 −0.559 0.134 4.495 0.381 3.736 5.254 F. altissima 0.366 1.717 0.155 1.044 0.178 0.687 1.400 F. micro carpa 0.518 0.829 0.089 2.076 0.178 1.723 2.429 L. speciosa 0.590 0.009 0.022 1.662 0.160 1.343 1.982 M. cajuputi 0.667 −0.090 0.039 2.632 0.169 2.298 2.966 M. × alba 0.792 0.048 0.018 1.076 0.100 0.871 1.282 P. serratifolia 0.686 −0.150 0.014 1.944 0.177 1.589 2.298 S. campanulata 0.738 −0.100 0.039 2.405 0.145 2.117 2.693 X. chrysanthus 0.333 0.043 0.015 1.193 0.209 0.775 1.611 (b) Only trees with protruding roots and/or flares A. moluccanus 0.422 −0.078 0.246 3.251 0.703 1.809 4.693 B. ceiba 0.550 −0.099 0.138 2.508 0.364 1.771 3.245 C. equisetifolia 0.684 0.224 0.097 2.222 0.274 1.662 2.782 C. burmannii 0.510 −0.085 0.133 3.565 0.533 2.489 4.642 D. regia 0.655 −0.442 0.182 4.464 0.486 3.484 5.444 F. altissima 0.348 1.792 0.153 0.968 0.174 0.619 1.317 F. microcarpa 0.516 0.846 0.090 2.053 0.721 1.699 2.408 M. cajuputi 0.399 0.031 0.141 2.601 0.479 1.635 3.567 S. campanulata 0.441 0.028 0.185 2.305 0.506 1.260 3.351 The proportion of explained variance (R2) of simple linear regression, intercept (b0) and regression coefficient of DBH (b1), and its standard errors (SE) were provided. The lower and upper boundary values of confidence intervals (CILOW, CIUP) were computed for more conservative estimation. Significant values of R2 and b1 with P < 0.05 were italicised and underlined for easier comparison. Five species, namely A. alexandrae, L. speciosa, M. × alba, P. serratifolia, and X. chrysanthus, were excluded in (b) due to insufficient sample size.
Protruding roots Protruding flares Protruding roots and/or flares Mean Median SD Brick Concrete Total Mean Median SD Brick Concrete Total Mean Median SD Brick Concrete Total A. moluccanus 0.521 0.489 0.153 5 15 20 0.736 0.723 0.289 6 8 14 0.626 0.555 0.249 10 19 29 A. alexandrae 0.144 0.144 N/A 1 0 1 0.178 0.178 0.018 2 0 2 0.167 0.165 0.024 3 0 3 B. ceiba 0.630 0.574 0.236 28 0 28 0.589 0.626 0.208 21 1 22 0.628 0.584 0.237 38 1 39 C. equisetifolia 0.586 0.578 0.148 8 0 8 0.530 0.490 0.199 16 0 16 0.564 0.536 0.192 19 0 19 C. burmannii 0.616 0.623 0.232 28 3 31 0.537 0.548 0.147 20 3 23 0.627 0.628 0.196 38 5 43 D. regia 0.867 0.708 0.495 24 3 27 0.794 0.613 0.471 29 8 37 0.870 0.689 0.500 37 8 45 F. altissima 1.334 1.227 0.522 47 1 48 1.290 1.207 0.425 50 1 51 1.419 1.306 0.472 56 1 57 F. microcarpa 1.137 0.989 1.102 42 26 68 1.060 1.042 0.387 41 19 60 1.225 1.099 0.999 48 29 77 L. speciosa 0.614 0.495 0.342 0 5 5 0.369 0.292 0.252 3 4 7 0.468 0.414 0.337 3 7 10 M. cajuputi 0.667 0.590 0.325 12 6 18 0.607 0.572 0.297 6 5 11 0.666 0.603 0.304 14 10 24 M. × alba N/A N/A N/A 0 0 0 N/A N/A N/A 0 0 0 N/A N/A N/A 0 0 0 P. serratifolia 0.658 0.658 0.042 1 1 2 0.350 0.350 N/A 1 0 1 0.555 0.628 0.180 2 1 3 S. campanulata 0.484 0.406 0.173 5 4 9 0.519 0.469 0.317 5 9 14 0.527 0.456 0.297 7 10 17 X. chrysanthus 0.631 0.631 N/A 1 0 1 N/A N/A N/A 0 0 0 0.631 0.631 N/A 1 0 1 Total 0.896 0.725 0.739 202 64 266 0.854 0.748 0.454 200 58 258 0.899 0.737 0.680 276 91 367 The 3 scenarios were namely protruding roots, protruding flares, and protruding roots and/or flares. The statistics were computed using only trees with protruding parts. For each scenario, if more than 1 protruding part was present on a tree, the length of the longest protrusion was considered. The count of pavement materials around the tree pits with protrusion was provided. Due to the lack of protrusion or small sample size, incomputable statistics were denoted by “N/A” for A. alexandrae, M. × alba, P. serratifolia, and X. chrysanthus.
- Table 4.
Binary logistic regression results predicting the occurrence of (a) protruding roots, (b) protruding flares, and (c) protruding roots and/or flares. Diameter at breast height and tree height were abbreviated as DBH and H.
Model statistics Effects on odds ratio X2 R2 Yes% No% Intercept DBH H Lean Pavement width Open soil area Setback Pavemen material (brick) (a) Protruding roots only A. moluccanus 22.43 0.365 55.0 89.8 0.336 1.081 1.056 0.904 1.101 0.319 2.083 0.064 B. ceiba 15.58 0.264 39.3 86.4 0 1.006 1.022 0.979 0.374 3.749 7.102 ∞ C. equisetifolia 15.53 0.247 15.4 99.0 ∞ 1.146 0.973 0.917 0.923 0 1.242 N/A C. burmannii 33.44 0.519 74.2 83.8 0 0.963 1.471 1.277 1.435 10.700 0.850 0.534 D. regia 14.98 0.251 40.7 87.2 0.105 1.048 0.828 1.105 0.747 1.707 1.046 7.128 F. altissima 11.88 0.295 93.8 27.3 ∞ 1.011 1.163 1.169 0.423 0.777 2.007 0 F. microcarpa 5.01 0.061 100.0 0 3.401 0.998 0.936 1.014 1.144 1.162 1.058 0.724 M. cajuputi 26.83 0.287 39.4 94.4 0.011 1.086 1.049 0.984 1.095 1.486 1.352 1.840 S. campanulata 42.85 0.616 73.3 96.4 0 1.241 1.006 0.924 1.424 2.959 0.997 0.089 All trees 273.84 0.314 38.3 94.2 0.064 1.049 1.014 1.028 0.934 1.269 1.110 0.958 (b) Protruding flares only A. moluccanus 38.63 0.637 64.3 96.9 0 1.158 0.948 1.112 0.278 32.930 165.600 5.516 B. ceiba 16.53 0.290 31.8 88.0 ∞ 1.086 0.921 0.896 0.598 2.170 1.456 0 C. equisetifolia 35.55 0.409 41.7 94.7 0 1.262 0.927 0.960 1.001 39.110 0.966 N/A C. burmannii 12.88 0.239 52.2 86.7 0.196 1.130 1.018 0.942 0.766 0.357 1.475 1.471 D. regia 17.71 0.284 64.9 64.9 0.047 1.078 1.067 0.990 0.721 1.345 1.174 2.901 F. altissima 10.68 0.302 100.0 37.5 ∞ 1.020 1.464 0.950 1.326 0.949 0.708 0 F. microcarpa 27.65 0.312 95.0 28.0 0.032 1.051 1.083 0.980 1.031 1.524 0.926 7.659 M. cajuputi 25.11 0.296 12.5 95.9 0.007 1.137 0.988 1.018 1.101 0.713 0.952 2.061 S. campanulata 39.96 0.518 52.4 94.8 0.002 1.075 1.177 1.080 1.001 12.800 0.901 0.111 All trees 468.80 0.493 53.8 94.0 0.015 1.102 1.000 1.008 0.972 1287 1.056 1.222 (c) Protruding roots and/or flares A. molp6uccanus 36.93 0.511 69.0 90.0 0.013 1.120 1.019 0.999 0.858 1.646 12.130 0.227 B. ceiba 24.74 0.389 66.7 72.7 ∞ 1.008 1.119 0.899 0.188 7.540 23.080 0 C. equisetifolia 36.11 0.385 41.9 95.4 0 1224 0.938 0.935 0.910 44.020 1.074 N/A C. burmannii 24.53 0.414 81.4 64.0 0.006 1.053 1.387 1.071 0.602 6.987 1.891 1.876 D. regia 12.73 0.214 77.8 31.0 0.291 1.030 0.987 1.009 0.642 1.954 1.311 5.918 F. altissima 17.47 1.000 100.0 100.0 ∞ 1.829 ∞ 0.565 0 0.008 0 ∞ F. microcarpa 15.37 0.570 100.0 33.3 ∞ 0.988 0.796 0.742 0 51.100 ∞ ∞ M. cajuputi 42.88 0.406 59.1 83.3 0.007 1.111 1.107 0.981 1.033 1.488 1.283 2.457 S. campanulata 55.91 0.634 69.2 93.1 0 1.088 1.346 1.072 1.118 20.480 1.036 0.056 All trees 540.1 0.523 69.8 87.9 0.034 1.114 0.980 1.003 0.916 1.758 1.132 0.956 The rates of correct prediction of the presence (Yes%) and absence (No%) of protrusion were provided. Species-specific effects of DBH in centimetres, H, lean angle, pavement width, open soil area, setback, and pavement material on the odds ratio of the occurrence of the 3 scenarios were reported. “N/A” indicated a lack of variation. Significant model statistics and predictors with P < 0.05 were italicised and underlined. For comparison, the pseudo-R2 values were supplied. A. alexandrae, L. speciosa, M. × alba, P. serratifolia, and X. chrysanthus were excluded due to small sample size.
- Table 5.
Multiple regression results for predicting the length of (a) protruding roots, (b) protruding flares, and (c) protruding roots and/or flares. Diameter at breast height and tree height were abbreviated as DBH and H.
R2 Intercept DBH H Lean angle Pavement width Open soil area Setback Pavement material (a) Protruding roots only A. moluccanus 0.203 0.711 −0.038 −0.002 0.004 −0.022 0.091 −0.454 −0.003 B. ceiba 0.285 −0.039 −0.782 0.060 0.041 0.043 0.018 −0.050 0 C. equisetifolia 0.192 0.451 −0.882 0.026 0.006 0.013 −0.048 0 N/A C. burmannii 0.668 0.519 0.684 −0.017 0.002 −0.095 0.292 0.102 −0.018 D. regia 0.639 −0.012 0.422 −0.018 −0.020 −0.043 0.168 0.086 0.713 F. altissima 0.338 1.069 −0.084 0.017 −0.004 −0.166 0.099 0.267 −0.223 F. microcarpa 0.017 −0.032 0.730 0 −0.005 0.032 0.119 −0.053 0.321 M. cajuputi 0.624 0.132 0.373 0.008 0.007 0.010 0.246 0.069 −0.076 S. campanulata 0.502 0.849 −0.750 −0.010 −0.003 −0.020 0.428 −0.054 −0.206 All trees 0.207 0.219 0.024 0.007 0 −0.009 0.165 0.006 0.158 (b) Protruding flares only A. moluccanus 0.127 0.239 −1.425 −0.009 −0.004 0.306 0.157 −0.623 0.006 B. ceiba 0.124 0.627 −0.602 0.002 0.002 −0.066 0.276 0.116 −0.116 C. equisetifolia 0.449 0.405 0.516 −0.029 0.015 −0.024 0.195 0.076 N/A C. burmannii 0.164 0.386 0.675 0.002 0.004 0.043 −0.224 −0.081 0.111 D. regia 0.590 0.347 0.026 −0.016 0.003 −0.046 0.234 0.034 0.205 F. altissima 0.294 2.290 −0.005 0.001 −0.009 −0.115 0.078 0.101 −0.952 F. microcarpa 0.479 0.320 0.511 −0.008 0.004 0.007 0.142 −0.027 0.080 M. cajuputi 0.759 0.014 −1.193 −0.013 0.016 −0.007 0.492 0.095 0.292 S. campanulata 0.756 −0.595 −0.835 0.030 0.019 0.037 0.416 −0.020 0.222 All trees 0.577 0.306 0.051 0 0.007 −0.014 0.154 0.001 0.092 (c) Protruding roots and/or flares A. moluccanus 0.398 0.660 −0.745 0.006 0.004 0.016 0.169 −0.427 −0.013 B. ceiba 0.167 0.428 −0.010 0.009 0.028 −0.062 0.158 0.063 −0.053 C. equisetifolia 0.196 0.134 0.312 −0.008 0.013 −0.002 0.148 0.050 N/A C. burmannii 0.475 0.237 0.536 0.001 0.003 −0.007 0.207 −0.016 0.024 D. regia 0.633 0.397 1.072 −0.053 0.007 −0.066 0.220 0.068 0.286 F. altissima 0.359 1.509 −0.051 0.008 −0.010 −0.158 0.103 0.208 −0.311 F. microcarpa 0.098 −0.207 1.110 −0.001 0.001 0.035 0.130 −0.064 0.327 M. cajuputi 0.662 0.126 0.432 −0.002 0.009 0.010 0.266 0.071 −0.019 S. campanulata 0.630 −0.319 −0.364 0.013 0.015 0.012 0.446 −0.015 0.127 All trees 0.311 0.185 0.164 0.003 0.008 −0.014 0.172 0.002 0.159 In each scenario, if more than 1 protrusion was detected on a tree, only the longest protruding parts were considered. Species-specific regression coefficients of the predictors, namely DBH, H, lean angle, pavement width, open soil area, setback, and pavement material, were presented. If significant, the adjusted R2 and regression coefficient values were italicised and underlined. “N/A” indicated a lack of variation. A. alexandrae, L. speciosa, M. × alba, P. serratifolia, and X. chrysanthus were excluded due to small sample size.
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