Transcript Estimating merchantable wood volume in two Puerto Rican

Estimating merchantable wood volume
in two Puerto Rican watersheds,
the San Juan Bay Estuary and
Río Grande de Arecibo
Thomas J. Brandeis,
Olaf Kuegler, and
María del Rocío Suárez Rozo
Why estimate volume?

Estimating wood volume allows the
placement of a monetary value on one of
the many commodities and services
forested watersheds provides to society.
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FIA produces resource bulletins, which
include volume estimates.
How is volume estimated?
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Volume tables
Geometric formulas
Regression equations
Few examples of regression equations that
predict tree volume for Puerto Rican forests
How was it done in the past?
Figure 1a.
DOB pole top
Figure 1b.
DOB pole top
Bole length
Bole length
DOB sawlog top
Sawlog length
DBH
DBH
DBH height (1.37 cm)
DBH height (1.37 cm)
DOB stump
DOB stump
Stump height (30 cm)
Pole timber (min DBH = 12.5 cm, min to DOB = 10.0 cm)
Stump height (30 cm)
Saw timber (min DBH = 27.5 cm, min top DOB = 22.5 cm)
How was it done in the past?

Inner bark diameters calculated
Section volume:
VSEC = [HSEC * {(DIB12) + (DIB1* DIB2) + DIB22)}*
0.00007854] / 3
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Each section summed for total stem volume
Excludes 30 cm stump and branches
How can we make it easier?
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Derive regression equations
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Based on previous inventory data’s multiple
stem measurements
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Uses only DBH and total height
measurements
Regression equations
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Equations fitted to the 1990 inventory data,
all species combined.
Mallow’s Cp, PRESS, Variance Inflation
Factor (VIF), and R2 statistics
Equations with DBH and HT, log transformed,
produced the best fit to the data.
Regression equations

DBH and total height
Vstem = exp (-12.00089+ 2.75276 (ln DBH) +
0.88961 (ln HT) – 0.02072 (DBH)
MSE = 0.041395, RMSE = 0.20346, R2 = 0.90827, N = 1,247
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DBH only
Vstem = exp(-11.37782+ 3.3595 (ln DBH) –
0.0273 (DBH)
MSE = 0.083472, RMSE = 0.28891, R2 = 0.81503, N = 1,247
Applications

San Juan Bay Estuary watershed
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–
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Inventoried in 2001
108 plots
Upper reaches of the Río Grande de
Arecibo watershed
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–
Inventoried in 2003
91 plots
Assumptions
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Palms, tree ferns, bamboo, some fruit trees, and
some other species excluded from volume
estimates.
Assumes log lengths similar to those of the 1990
Puerto Rico forest inventory.
Unsound cull trees not removed from data sets,
so merchantable volume is over-estimated.
Estimates do not take into account smaller
dimension material such as branch wood.
Example 1:
San Juan Bay Estuary Watershed
N
San Juan Bay Watershed
20
0
20
40
60
80
100
120 Kilometers
SJBE watershed volume estimate
Area (ha)
Mean Vol/ha
(m3/ha)
SE
Total Vol
(m3)
Urban
11,430
19.98
4.49
228,384.33
Forest
4,032
53.65
25.52
216,319.69
Totals
15,462
Land use
444,704 m3
Example 2: Río Grande de Arecibo
watershed
RGA watershed volume
Area (ha)
Mean Vol/ha
(m3/ha)
SE
Total Vol
(m3)
617.10
67.47
25.00
41,635.29
2,341.59
59.08
8.04
138,350.93
704.55
116.70
45.78
82,224.52
1,725.61
57.70
16.27
99,560.10
471.46
108.34
107.03
51,075.95
wf-S-Kt
7,930.23
83.03
5.88
658,472.05
wf-S-Ti
478.77
71.89
49.33
34,416.30
wf-S-Tkp
5,929.00
85.25
1.65
505,426.21
wf-S-Tks
2,972.25
88.72
1.92
263,690.91
wf-S-Ts
4,129.21
88.32
1.97
364,707.24
Totals
27,299.76
Strata
mf-S-Kt
mf-S-Tkp
mf-S-Ts
wf-Lm-Kt
wf-Lm-Tkp
2,239,559 m3
Conclusions
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These equations could be applied to other
forests in Puerto Rico, and other Caribbean
islands with similar structures and species
compositions.
Note: no attempt made to place monetary
value on this wood.
Future work
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Species-specific equations
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Taper equations; volume to a variable upper
diameter merchantability limit
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Biomass studies
Acknowledgements
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Andy Hartsell, Raymond Sheffield, James
Rosson and Larry Royer of the USDA Forest
Service Southern Research Station.
Prof. Luis R. Pérez Alegría of the Department
of Agricultural and Biosystems Engineering,
University of Puerto Rico at Mayagüez, PI of
the Atmospheric Carbon Sequestration Project
of the UPRM-NASA-URC.