Volume and Aboveground Biomass Models for Dry Miombo Woodland in Tanzania
Table 2
Volume and biomass equations for estimating total aboveground and stem (≥5 cm) volume and biomass of shrubs, trees, and woody plants in general (shrubs and trees) in Gangalamtumba Village Land Forest Reserve. A few estimates are not significantly different from zero (). These are marked “ns.”
Category
Component
Equation
Regression parameters
Dbh range (cm)
RMSE
Avg. error (%)
Shrubs (); 16 species
Total volume (df = 27)
3
−8.3287 (0.237)
2.2340 (0.099)
0.0507ns (0.206)
1.8–21.5
0.979
0.251
0.00
18.48
(df = 28)
4
−8.2844 (0.152)
2.2517 (2.252)
—
1.8–21.5
0.979
0.247
0.00
18.57
Stem volume (df = 23)
3
−13.4822 (0.673)
1.7917 (0.316)
2.8547 (0.453)
5–21.5
0.865
0.533
0.00
30.34
(df = 24)
4
−10.8001 (0.710)
2.6587 (0.299)
—
5–21.5
0.792
0.482
0.636
57.79
Total biomass (df = 27)
3
−1.8567 (0.252)
2.2145 (0.106)
0.1591ns (0.219)
1.8–21.5
0.977
0.267
0.00
21.90
(df = 28)
4
−1.7179 (0.163)
2.2697 (0.073)
—
1.8–21.5
0.977
0.265
0.00
22.43
(df = 28)
6
−8.6142 (0.427)
0.9417 (0.034)
—
1.8–21.5
0.968
0.266
0.184
18.93
Stem biomass (df = 23)
3
−6.8855 (0.639)
1.9676 (0.257)
2.6083 (0.428)
5–21.5
0.916
0.390
0.276
29.50
(df = 24)
4
−4.3236 (0.705)
2.6903 (0.296)
—
5–21.5
0.799
0.470
0.676
56.02
Trees (); 28 species
Total volume (df = 69)
3
−9.5238 (0.075)
1.8067 (0.040)
1.1940 (0.076)
1.4–62
0.997
0.129
0.00
1.66
(df = 70)
4
−8.4800 (0.099)
2.3351 (0.033)
—
1.4–62
0.986
0.219
0.179
6.46
Stem volume (df = 35)
3
−11.0643 (0.166)
1.9316 (0.079)
1.5360 (0.119)
5–62
0.994
0.162
0.00
4.55
(df = 35)
4
−10.9307 (0.273)
3.0134 (0.093)
—
5–62
0.975
0.317
0.119
13.10
Total biomass (df = 69)
3
−3.1399 (0.123)
1.7586 (0.057)
1.2934 (0.115)
1.4–62
0.992
0.118
0.278
2.47
(df = 70)
4
−2.0667 (0.124)
2.3561 (0.036)
—
1.4–62
0.979
0.213
0.392
9.96
(df = 70)
6
−9.1880 (0.101)
0.9668 (0.007)
—
1.4–62
0.996
0.131
0.052
1.32
Stem biomass (df = 37)
3
−5.6032 (0.326)
2.1420 (0.158)
1.7090 (0.269)
5–62
0.965
0.294
0.221
6.30
(df = 38)
4
−4.4622 (0.365)
2.9972 (0.120)
—
5–62
0.928
0.387
0.375
10.60
Combined (); 44 species
Total volume (df = 100)
3
−9.0339 (0.104)
1.9637 (0.053)
0.7737 (0.103)
1.4–62
0.989
0.193
0.131
6.54
(df = 101)
4
−8.4554 (0.084)
2.3236 (0.031)
—
1.4–62
0.983
0.248
0.140
9.89
Stem volume (df = 42)
3
−12.2617 (0.244)
2.1378 (0.127)
1.7695 (0.203)
5–62
0.977
0.271
0.153
18.50
(df = 43)
4
−11.1929 (0.339)
3.0514 (0.115)
—
5–62
0.935
0.413
0.327
49.22
Total biomass (df = 100)
3
−2.6896 (0.131)
1.9041 (0.064)
0.9377 (0.128)
1.4–62
0.983
0.182
0.317
8.96
(df = 101)
4
−1.9564 (0.102)
2.3260 (0.035)
—
1.4–62
0.974
0.242
0.327
12.60
(df = 101)
6
−8.8819 (0.139)
0.9497 (0.010)
—
1.4–62
0.988
0.187
0.162
6.40
Stem biomass (df = 42)
3
−5.9897 (0.279)
2.0894 (0.146)
1.9457 (0.238)
5–62
0.970
0.290
0.230
13.70
(df = 43)
4
−4.8335 (0.349)
3.0979 (0.117)
—
5–62
0.924
0.383
0.488
43.10
(df = 43)
6
−13.5156 (0.455)
1.2284 (0.032)
—
5–62
0.971
0.314
0.153
25.10
Note: numbers in brackets indicate standard errors of the estimates. Height range: shrubs 2.5–8 m; trees: 2.5–18.2 m; and combined: 2.5–18.2 m. df is degrees of freedom; RMSE is standard error of the residuals; is the standard deviation of the species random effect (between-species variation); is the likelihood ratio based coefficient of determination; and Avg. is Average. Equation (3): . Equation (4): . Equation (6): ; Y is volume (m3) or biomass (kg); Dbh is diameter at breast height (cm); ht is total height (m); and wd is wood density (kg m−3).
