Volume and Aboveground Biomass Models for Dry Miombo Woodland in Tanzania
Table 1
Volume and biomass equations† for estimating total aboveground and stem (≥5 cm) volume and biomass of three dominant species in the Gangalamtumba Village Land Forest Reserve. All parameter estimates are significantly different from zero ().
Species
Component
Equation
Regression parameters
Dbh range (cm)
Adj.
RMSE
Avg. error (%)
Brachystegia spiciformis ()
Total volume (df = 37)
3
−9.3188 (0.166)
1.9663 (0.088)
0.9118 (0.174)
1.2–54.3
0.997
0.142
1.99
(df = 38)
4
−8.5018 (0.077)
2.4142 (0.027)
—
1.2–54.3
0.995
0.185
3.49
Stem volume (df = 31)
3
−11.7673 (0.379)
2.0335 (0.141)
1.6858 (0.314)
5–54.3
0.990
0.209
−0.02
(df = 32)
4
−9.8909 (0.203)
2.7460 (0.066)
—
5–54.3
0.981
0.286
2.14
Total biomass (df = 37)
3
−2.6071 (0.149)
2.0638 (0.078)
0.7847 (0.155)
1.2–54.3
0.998
0.127
1.60
(df = 38)
4
−1.9040 (0.068)
2.4492 (0.024)
—
1.2–54.3
0.996
0.162
2.67
(df = 38)
6
−9.3309 (0.108)
0.9827 (0.008)
—
1.2–54.3
0.998
0.127
1.66
Stem biomass (df = 31)
3
−5.0668 (0.343)
2.1424 (0.128)
1.5563 (0.284)
5–54.3
0.992
0.189
−0.57
(df = 32)
4
−3.3345 (0.185)
2.8002 (0.061)
—
5–54.3
0.985
0.262
1.17
Combretum molle
()
Total volume (df = 38)
3
−9.0504 (0.165)
1.9212 (0.099)
0.7712 (0.183)
2.2–26.5
0.987
0.171
2.90
(df = 39)
4
−8.5247 (0.130)
2.2972 (0.051)
—
2.2–26.5
0.981
0.204
4.24
Stem volume (df = 30)
3
−10.3990 (0.223)
2.0420 (0.126)
1.0908 (0.193)
5–26.5
0.977
0.146
4.64
(df = 31)
4
−9.8028 (0.277)
2.6237 (0.102)
—
5–26.5
0.954
0.206
4.98
Total biomass (df = 38)
3
−2.4539 (0.165)
1.9685 (0.099)
0.7545 (0.183)
2.2–26.5
0.987
0.170
2.88
(df = 39)
4
−1.9395 (0.129)
2.3364 (0.050)
—
2.2–26.5
0.982
0.203
4.20
(df = 39)
6
−8.8347 (0.230)
0.9371 (0.168)
—
2.2–26.5
0.987
0.170
2.98
Stem biomass (df = 30)
3
−3.7737 (0.230)
2.1112 (0.130)
1.0410 (0.199)
5–26.5
0.976
0.151
4.41
(df = 31)
4
−3.2047 (0.275)
2.6663 (0.101)
—
5–26.5
0.956
0.205
4.66
Dalbergia arbutifolia ()
Total volume (df = 34)
3
−9.3147 (0.191)
1.9701 (0.059)
0.8854 (0.152)
1.8–21.5
0.991
0.144
2.04
(df = 35)
4
−8.3253 (0.120)
2.2413 (0.051)
—
1.8–21.5
0.982
0.200
3.90
Stem volume (df = 29)
3
−13.8803 (0.761)
2.0113 (0.246)
2.7732 (0.455)
5–21.5
0.871
0.355
12.97
(df = 30)
4
−10.5743 (0.793)
2.7785 (0.313)
—
5–21.5
0.715
0.528
32.87
Total biomass (df = 34)
3
−2.7097 (0.199)
1.9900 (0.062)
0.9035 (0.159)
1.8–21.5
0.990
0.150
1.22
(df = 35)
4
−1.7001 (0.124)
2.2667 (0.052)
—
1.8–21.5
0.981
0.206
3.00
(df = 35)
6
−9.3782 (0.213)
0.9823 (0.016)
—
1.8–21.5
0.990
0.148
1.37
Stem biomass (df = 29)
3
−7.3073 (0.776)
2.0138 (0.250)
2.8503 (0.464)
5–21.5
0.869
0.362
11.53
(df = 30)
4
−3.9094 (0.812)
2.8023 (0.321)
—
5–21.5
0.708
0.541
30.54
(df = 30)
6
−14.5150 (1.467)
1.2961 (0.108)
—
5–21.5
0.823
0.421
17.00
Note: numbers in brackets indicate standard errors of the parameter estimates. Height (range): B. spiciformis: 2–17.2 m; C. molle: 2.6–9.4 m; and D. arbutifolia: 2.6–8.8 m. df is degrees of freedom; RMSE is the standard error of the residuals; Adj. is the adjusted coefficient of determination; Avg. is Average. Equation (3): . Equation (4): . Equation (6): ; 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).