Cranbrook TSA
IDF and PP Ground Call Analysis
PREPARED FOR:
MINISTRY OF FORESTS AND RANGE
SOUTHERN INTERIOR REGION
PREPARED BY:
Jahraus & Associates Consulting Inc.
Maple Ridge BC
&
Churlish Consulting Ltd.
Victoria BC
February 2008
Cranbrook TSA: IDF and PP Ground Call Analysis
i
Table of Contents
1
2
3
4
5
6
7
8
Introduction ................................................................................................................. 1
Scope and Objectives................................................................................................... 1
Methods ....................................................................................................................... 1
3.1 Ground data and forest cover attributes ............................................................... 1
3.2 Stratification ......................................................................................................... 3
Analysis Results .......................................................................................................... 4
4.1 Comparison of ground and inventory values for basic forest cover attributes..... 4
4.2 Comparison of ground and inventory volume...................................................... 4
4.3 Coefficients of variation and sample size ............................................................ 7
Discussion and Recommendations .............................................................................. 8
APPENDIX A............................................................................................................ 11
APPENDIX B ............................................................................................................ 14
APPENDIX C ............................................................................................................ 15
February 2008
Cranbrook TSA: IDF and PP Ground Call Analysis
1
1 Introduction
This project was initiated by Ministry of Forests & Range (MFR) in the Southern Interior
region in response to MFR and Licensee concerns in the Rocky Mountain Forest District
(RMFD) regarding potential overestimation of Forest Cover Inventory volumes in the
Interior Douglas Fir and Ponderosa Pine Biogeoclimatic zones of the Cranbrook Timber
Supply Area. In the summer of 2007, 52 ground samples were randomly established in
forested polygons (>10% crown Closure and > 30 years of age) in the IDF and PP
Biogeoclimatic zones within the Cranbrook TSA portion of the RMFD. Areas in private
lands, First Nations Reserves, Parks and TFL’s were been excluded. This analysis
encompassed the compilation of this field data and comparison with Forest Cover
attributes.
2 Scope and Objectives
The terms of reference and task list for this project are provided below:
1. Compile ground data (includes: converting data from MDB format to one suitable
for input into the VRI compiler; making modifications to the VRI compiler to
accommodate the non-standard data collection)
2. Run VDYP7 and VDYP6 on sample inventory data to project attributes to year of
ground sampling
3. Compare ground attributes and Forest Cover attributes for the established samples
and compute age, height, basal area and trees/ha ratios and sampling errors (as
well as coefficients of variation), as per a standard statistical adjustment. Logical
leading species strata will be used in consultation with the contract coordinator.
4. Using the compiled volume data, estimate sample size requirements for phase 2
sampling using the strata defined in step 1 and the population as a whole.
5. Replicate these processes using both VDYP6 and VDYP7 and provide discussion
of any noted differences.
3 Methods
3.1 Ground data and forest cover attributes
Details on the project background, sample selection and data collection are provided in
Appendix A. Forest cover attributes were provided by Matt Makar. All samples were
from F-type (FIP) inventories and hence did not include second species heights or ages,
photo-interpreted basal area/ha or trees/ha.
VDYP6 v.6.6d was used to generate the VDYP6 volumes. Data was first projected to
2007. Note that this version of VDYP6 uses SINDEX version 2.3 for height projection.
For the VDYP7 portion of the analysis, VDYP7 Console was used. All samples were
first projected to 2007 (VDYP7 used SINDEX version 3.3 for height projection).
February 2008
Cranbrook TSA: IDF and PP Ground Call Analysis
2
The ground sample data was compiled using the VRI compiler with adaptations to
accommodate the data collection procedures used in this project1. Since live/dead
indicators were not collected, all trees were assumed to be live2. In addition, pathological
indicators were not collected for the ground sample trees3 hence decay could not be
estimated. As a result, all volume comparisons were done on a whole stem volume
(WSV) basis.
The analysis compared ground attributes with forest cover attributes and computed ratios
and associated sampling errors. The methodology for computing the ratios was based on
the standards and procedures for a VRI statistical adjustment. Height and age ratios were
computed based on forest cover attributes from VDYP6 and height, age, basal area/ha &
trees/ha ratios were computed based on forest cover attributes from VDYP7. These ratios
would approximate the VRI Stage 1 adjustment factors.
In this project, ages were collected for “representative” trees but heights were collected
for all trees4. The ground ages and heights used in the ratio comparisons were based on
those collected for only the “representative” trees5.
Since pathological indicators were not collected and net factoring was not applied,
ground volumes net decay were not available from the compiler. Hence, VRI-type
adjustment factors for volume (i.e. Stage 2 adjustment factors) could not be computed.
However, volume comparison ratios (similar to what are referred to as volume “impact”
ratios in a VRI adjustment analysis) were developed for whole stem volumes. These
volume comparison ratios were estimated by comparing the ground compiled mean
whole stem volumes (WSV) with the unadjusted6 inventory mean volumes from VDYP6
and VDYP7. Although VDYP7 generates estimates of WSV at various utilization levels,
VDYP6 only produces WSV at the 7.5cm+ dbh utilization level. Therefore a comparison
at the 7.5cm+ dbh utilization was computed for both VDYP6 and VDYP7 and a
comparison at 12.5cm+ dbh was computed for VDYP7 only.
1
Data collection followed Phase 1 ground call methodology rather than VRI Phase 2 ground sample
methodology.
2
Sample #2 included a comment “all trees except 1 dead from fire approx 2yrs.” but the tree number for
the single live tree was not indicated. Similarly, sample #78 indicated “dead ibm pl in plot” but the tree
number for the dead tree was not specified. Since the dead trees could not be identified, all trees were
assumed to be live. Broken top trees were identified, but neither broken top diameter nor projected heights
were provided so the height listed became the height used for compilation.
3
The standard VRI net factoring procedure was not applied in this project.
4
The methodology was similar to that used for Phase 1 ground calls, as opposed to the VRI top height
methods.
5
The heights that were collected on all trees were used in the compilation of ground volume. However, for
the height ratio comparison, only trees that had ages were used to compute the average height for a sample.
6
Unadjusted volumes refer to those based on unadjusted forest cover attributes e.g. heights and ages that
have not been ratio-adjusted based on ground sample information.
February 2008
Cranbrook TSA: IDF and PP Ground Call Analysis
3
3.2 Stratification
The distribution of the samples, by biogeoclimatic zone and leading species, is shown in
Table 1. More than 60% of the samples were fir leading, based on the inventory species
composition7.
Table 1: Distribution of samples.
Inventory leading species
Biogeoclimatic Zone
IDF
PP
Total
AC
EP
FD
LW
PL
PY
SE
1
1
25
6
6
2
0
0
0
7
2
0
1
1
1
1
32
8
6
3
1
Total
41
11
52
Various leading species and biogeoclimatic zone-based strata were considered. However,
given the distribution of samples (almost half of the samples being fir leading in IDF), the
options were somewhat limited. When the number of samples within a stratum is small
(as we see here for most non-fir leading species), there was a risk that any trends seen in
these minor strata may be spurious.
With the relatively large number of samples in the fir leading stratum, there was potential
for stratification within this leading species group (by age or leading species % within the
fir leading stratum). However, this more detailed level of stratification within the fir
leading samples was not pursued in this analysis. It was suggested that larch leading may
be a stratum of interest; this was included in one of the stratification alternatives
described below.
For this project, 3 stratification alternatives (referred to as “runs”) were considered:
1) No stratification (analysis based on all 52 samples as a whole)
2) Two strata: fir leading & non-fir leading
3) Three strata: fir leading, larch leading & non-fir/non-larch leading.
Results for each of these three runs are provided in section 4 that follows. In addition,
summary results based on a biogeoclimatic (BEC) zone stratification are provided in
Appendix B. Since trends by leading species were stronger than trends by BEC, the BECbased stratification was not pursued further.
7
One sample was pine leading in the FIP file (volume-based species composition) but when the file was
“completed” (run through VDYP7 where species composition is converted to a basal area basis), the
leading species changed to fir. The VDYP7 leading species (i.e. Fd) was used for stratum assignment in
this analysis.
February 2008
Cranbrook TSA: IDF and PP Ground Call Analysis
4
4 Analysis Results
4.1 Comparison of ground and inventory values for basic forest cover
attributes
Ratio-of-means comparisons were computed for several VDYP6 (height and age) and
VDYP7 (height, age, basal area/ha, trees/ha) forest cover attributes. Since this was a FIPbased inventory, the basal area/ha and trees/ha attributes were generated by VDYP7 (i.e.
they were not available as photo-interpreted values). These comparison ratios, and their
associated sampling errors, are shown in Table 2 for VDYP6 and in Tables 3, 4 & 5 for
VDYP7. Note that although a standard Stage 1 VRI statistical adjustment using VDYP7
would be based on basal area/ha and tree/ha at the 7.5cm+ dbh utilization level (as in
Table 4), ratio comparisons for a 12.5cm+ dbh utilization are also provided (Table 5).
This sample indicates that the forest cover attributes generally overestimate8 age by about
15%. Overall, height is overestimated by about 7% or about 1.5m, on average9. Larch
leading polygons show the highest degree of age and height overestimation, based on this
small sample of such polygons.
Basal area/ha appears to be generally underestimated by VDYP7. However, poststratification of the sample indicates that this basal area/ha underestimation may be
confined primarily to fir or larch leading stands. The sample indicates that trees/ha is, on
average, relatively unbiased at the 7.5cm+ dbh utilization level and slightly overestimated
at the 12.5cm+ dbh utilization level.
The graphical relationships between the ground values and the inventory values of these
forest cover attributes are provided in Appendix C.
4.2 Comparison of ground and inventory volume
The potential bias associated with VDYP6 and VDYP7 whole stem volume estimation,
was also estimated from the sample by computing a ratio of mean ground volume to
mean inventory volume. Sampling errors and coefficients of variation (CVs) were
reported for these estimated volume ratios-of-means. These results are provided in Table
6.
Overall, this sample suggests that VDYP6 whole stem volumes (at 7.5cm+ dbh
utilization) are slightly overestimated (by about 2%) for this population. For a VDYP7
inventory, the sample suggests that whole stem volumes are underestimated by about
10% on average. When the sample is post-stratified by inventory leading species, the
sample would suggest that both VDYP6 and VDYP7 underestimate volume in fir and
larch leading stands but both yield models overestimate volume for other leading species.
8
A ratio larger than 1.0 indicates potential underestimation whereas a ratio less than 1.0 indicates potential
overestimation.
9
Slight differences between inventory heights from VDYP6 and VDYP7 occur due to the fact that VDYP6
and VDYP7 use different versions of the site index function SINDEX.
February 2008
Cranbrook TSA: IDF and PP Ground Call Analysis
5
Table 2: Ground and VDYP6 height and age means and ratios (with 95% sampling error %), for three alternative strata
Mean age (yrs)
Mean height (m)
VDYP6 Age
Run
Stratum
ratio of means
n
Ground
Inventory
n
Ground
Inventory
1
2
3
all samples
FD leading
non-FD leading
FD leading
LW leading
non-FD/ non-LW
51
32
19
32
8
11
90
94
84
94
88
81
109
110
107
110
127
92
0.832 ±10.5%
0.858 ±12.0%
0.787 ±21.1%
0.858 ±12.0%
0.688 ±42.4%
0.888 ±17.2%
51
32
19
32
8
11
20.2
19.6
21.2
19.6
21.3
21.2
21.7
21.2
22.5
21.2
24.4
21.1
Table 3: Ground and VDYP7 height and age means and ratios (with 95% sampling error %), for three alternative strata
Mean age (yrs)
Mean height (m)
VDYP7 Age
Run
Stratum
ratio of means
n
Ground
Inventory
n
Ground
Inventory
1
2
3
all samples
FD leading
non-FD leading
FD leading
LW leading
non-FD/ non-LW
51
32
19
32
8
11
90
94
84
94
88
81
109
110
107
110
127
92
0.832 ±10.5%
0.858 ±12.0%
0.787 ±21.1%
0.858 ±12.0%
0.688 ±42.3%
0.888 ±17.2%
51
32
19
32
8
11
20.2
19.6
21.2
19.6
21.3
21.2
21.6
21.2
22.3
21.2
23.9
21.2
VDYP6 Height
ratio of means
0.932 ±5.7%
0.925 ±6.6%
0.943 ±11.2%
0.925 ±6.6%
0.870 ±16.2%
1.004 ±16.7%
VDYP7 Height
ratio of means
0.935 ±5.7%
0.926 ±6.6%
0.950 ±11.0%
0.926 ±6.6%
0.888 ±15.6%
1.000 ±17.0%
Table 4: Ground and VDYP7 basal area/ha and trees/ha at 7.5cm+dbh utilization means and ratios (with 95% sampling error %), for three
alternative strata
Mean basal area/ha @7.5cm+ (BA)
Mean trees/ha @7.5cm+ (TPH)
VDYP7 BA
VDYP7 TPH
Run
Stratum
ratio of means
ratio of means
n
Ground
Inventory
n
Ground
Inventory
1
2
3
all samples
FD leading
non-FD leading
FD leading
LW leading
non-FD/ non-LW
52
32
20
32
8
12
26.1
26.9
24.7
26.9
34.0
18.4
22.6
22.0
23.4
22.0
25.5
22.1
1.154 ±12.5%
1.223 ±14.9%
1.052 ±23.7%
1.223 ±14.9%
1.333 ±30.2%
0.835 ±33.8%
52
32
20
32
8
12
758
786
712
786
942
559
758
738
792
738
842
758
0.999 ±20.8%
1.065 ±28.3%
0.900 ±31.7%
1.065 ±28.3%
1.119 ±39.9%
0.738 ±56.0%
February 2008
Cranbrook TSA: IDF and PP Ground Call Analysis
6
Table 5: Ground and VDYP7 basal area/ha and trees/ha at 12.5cm+dbh utilization means and ratios (with 95% sampling error %), for three
alternative strata
Mean basal area/ha @12.5cm+ (BA)
Mean trees/ha @12.5cm+ (TPH)
VDYP7 BA
VDYP7 TPH
Run
Stratum
ratio of means
ratio of means
n
Ground
Inventory
n
Ground
Inventory
1
2
3
all samples
FD leading
non-FD leading
FD leading
LW leading
non-FD/ non-LW
52
32
20
32
8
12
24.5
25.3
23.2
25.3
32.3
17.2
20.7
20.0
21.7
20.0
23.8
20.3
1.186 ±12.9%
1.264±14.1%
1.070 ± 26.2%
1.264±14.1%
1.356 ± 33.8%
0.738 ± 56.0%
52
32
20
32
8
12
549
565
524
565
722
393
519
481
578
481
638
539
1.059 ± 18.8%
1.173 ± 23.0%
0.907 ± 33.2%
1.173 ± 23.0%
1.131 ± 41.9%
0.729 ± 57.4%
Table 6: Ground, VDYP6 & VDYP7 whole stem volume at 7.5cm+ dbh utilization means and ratios (with 95% sampling error %), for three
alternative strata (“volume impact”)
Mean vol/ha (WSV @7.5cm+ dbh)
VDYP6 WSV @7.5cm+ volume VDYP7 WSV @7.5cm+ volume
(inventory
volumes
based
on
unadjusted
attributes)
ratio of means
ratio of means
Run
Stratum
n
Ground
VDYP6
VDYP7
Ratio & SE%
CV of ratio
Ratio & SE%
CV of ratio
1
2
3
all samples
FD leading
non-FD leading
FD leading
LW leading
non-FD/ non-LW
52
32
20
32
8
12
185.6
184.7
187.1
184.7
249.5
145.5
189.5
172.6
216.5
172.6
229.0
208.2
168.4
153.5
192.3
153.5
196.8
189.3
0.980 ± 13.1%
1.070 ± 15.9%
0.864 ± 22.9%
1.070 ± 15.9%
1.090 ± 32.5%
0.699 ± 29.6%
47%
44%
49%
44%
39%
47%
51%
47%
54%
47%
39%
53%
1.102 ± 14.1%
1.203 ± 17.1%
0.973 ± 25.1%
1.203 ± 17.1%
1.268 ± 32.7%
0.769 ± 33.7%
Table 7: Ground & VDYP7 whole stem volume at 12.5cm+ dbh utilization means and ratios (with 95% sampling error %), for three alternative
strata (“volume impact”)
Mean vol/ha (WSV @12.5cm+ dbh)
VDYP7 WSV @12.5cm+ volume ratio of means
Run
Stratum
n
Ground
Unadjusted Inventory (VDYP7)
Ratio & SE %
CV of ratio
1
2
3
all samples
FD leading
non-FD leading
FD leading
LW leading
non-FD/ non-LW leading
52
32
20
32
8
12
177.9
177.0
179.3
177.0
241.2
138.0
160.3
145.7
183.7
145.7
188.9
180.2
1.110 ± 14.5%
1.215 ± 16.7%
0.976 ± 26.9%
1.215 ± 16.7%
1.277 ± 35.2%
0.765 ± 36.0%
52%
46%
57%
46%
42%
57%
February 2008
Cranbrook TSA: IDF and PP Ground Call Analysis
7
Note that VDYP7 whole stem volumes were consistently less than VDYP6 volumes, by
roughly 10% on average. The consistency of this trend is illustrated in Figure 1 below.
VDYP7 WSV @7.5cm+ dbh
400
300
200
100
0
0
100
200
300
400
VDYP6 WSV @7.5cm+ dbh
Figure 1: Comparison of VDYP6 and VDYP7 volumes (whole stem at 7.5 cm+ dbh utilization).
The diagonal line represents a 1:1 correspondence.
4.3 Coefficients of variation and sample size
The sampling error for the overall estimated ratio of ground to VDYP7 whole stem
volume at 12.5cm+ dbh utilization is about 14.5% at a 95% confidence level. This is
based on the current sample size of 52. Using the CV of the ratio, the estimated sample
size required to achieve a desired precision can be calculated.
The CV of the ratio R is computed as:
where
is the variance of the ratio.
The sample size, for a given CV and target percentage error (PE) is then computed as:
where t is the value from the Student t distribution for a given significance level (α) and
degrees of freedom (n-1).
Note that since n appears on both sides of the equation (it is required for the t value on
the right side of the equation), the result must be found through iteration.
February 2008
Cranbrook TSA: IDF and PP Ground Call Analysis
8
The CVs for the volume ratios in Table 7 were used to estimate the sample size required
to achieve a 10% and a 15% sampling error for total adjusted volume. These results are
shown in Table 8 below.
Table 8: Estimated sample sizes to achieve ±10% and ±15% percentage error for total
adjusted volume, at a 5% significance level (95% confidence level), based on whole stem
volume ratio CVs from the current sample.
Run
1
2
3
Stratum
all samples
FD leading
non-FD leading
FD leading
LW leading
non-FD/ non-LW
leading
Sample size at 5% significance level
10% PE
15% PE
n
Ratio
CV
52
32
20
32
8
1.110
1.215
0.976
1.215
1.277
52%
46%
57%
46%
42%
106
84
127
84
70
49
39
58
39
33
12
0.765
57%
127
58
These sample size estimates are based on whole stem volume ratios. In a Phase 2 VRI
ground sampling project implementation plan, sampling error targets are generally
specified in terms of volume estimates at a standard utilization (typically 12.5cm+ dbh)
net decay, waste & breakage (dwb). It is not known how CVs for a volume ratio net dwb
would compare with the whole stem volume ratio CVs shown in Table 7. However it is
suspected that the CVs for volumes net dwb would be higher. If the CVs shown in Table
8 are inflated (by adding 5 percentage points), the following sample sizes would result:
Table 9: Estimated sample sizes to achieve ±10% and ±15% percentage error for total
adjusted volume, at a 5% significance level10, based on inflated whole stem volume ratio
CVs from the current sample (inflated CV% = original CV% + 5%).
Run
1
2
3
Stratum
all samples
FD leading
non-FD leading
FD leading
LW leading
non-FD/ non-LW
leading
Sample size at 5% significance level
10% PE
15% PE
n
Ratio
Inflated
CV
52
32
20
32
8
1.110
1.215
0.976
1.215
1.277
57%
51%
62%
51%
47%
127
102
150
102
87
58
47
68
47
40
12
0.765
62%
150
68
5 Discussion and Recommendations
The forest cover attributes used in this analysis were from a FIP-based inventory. As a
result, there were no photo-interpreted basal areas/ha or trees/ha and hence these
attributes had to be generated by VDYP7. The analysis of the sample data indicates that
10
Or 95% confidence level
February 2008
Cranbrook TSA: IDF and PP Ground Call Analysis
9
inventory ages and, to a lesser degree, inventory heights are generally overestimated in
this population. Basal area/ha appears to be generally underestimated by VDYP7.
However, stratification by leading species suggests that the basal area underestimation is
more closely related to Fd and Lw leading polygons. Although there is little overall
average bias associated with the VDYP7-generated trees/ha attribute, the scatterplots for
the trees/ha attribute show poor correlation with the ground compiled trees/ha.
The ground compiled volume estimates from this sample suggest that VDYP7
underestimates volume in Fd and Lw leading polygons, following the trend observed for
basal area/ha. For non-FD and non-Lw leading polygons, VDYP7 volume appears to be
overestimated. Note that these results are based on whole stem volumes, since decay
information for the ground sample was not available. Once net factoring and a net
volume adjustment factor (NVAF) are applied to the ground volumes, as in a VRI Phase
2 sample, the ratio of ground volume to VDYP7 inventory volume may change.
Although VDYP6 volume bias trends by leading species followed a pattern similar to that
observed for VDYP7 (i.e. volumes underestimated for Fd and Lw leading polygons
whereas volumes were overestimated for non-FD and non-Lw polygons), the magnitude
of the bias differed considerably. For this sample, the volumes estimated by VDYP6 were
consistently larger than the volumes estimated by VDYP7. The overall ratio of mean
VDYP6 to mean VDYP7 whole stem volume was 1.12, indicating that on average
VDYP6 volume was 12% higher than VDYP7 volume.
Volumes net dwb could not be compiled for the ground sample but the two yield models
could still be compared at this utilization. Average volumes from VDYP6 were about
16% higher than average volumes from VDYP7 at 12.5cm+ utilization net dwb. In the
absence of a VRI Phase 2 statistical adjustment, this analysis suggests that moving from
VDYP6 to VDYP7 will lower the overall inventory volume.
As part of this analysis, coefficients of variation (CVs) were computed so that potential
sample size for VRI Phase 2 ground sampling could be estimated. Since the plot
configuration in this project (3 point plots) differed from a standard VRI ground sample
(5 point plots), the observed variability reflected by the CV may not be the same as what
would be observed in a VRI Phase 2. In addition, the CV in this analysis was based on
ratios of whole stem volumes, not ratios of volumes net dwb (VRI Phase 2 project
implementation plans typically specify sampling error targets based on volumes net dwb).
For the purpose of VRI Phase 2 sample size estimation, it is suggested that the CVs from
this sample data be inflated to account for these differences.
The most appropriate magnitude of the CV inflation needs to be determined but a
minimum increment of 5% is suggested. It is recommended that the level of CV inflation
be discussed with MFR Forest Analysis and Inventory Branch (FAIB) staff prior to any
final decisions on sample size. Risk and budgetary factors will also come into play in the
final decision, however, a minimum sample size of 130 is recommended for this
population in order to meet a 10% sampling error target.
February 2008
Cranbrook TSA: IDF and PP Ground Call Analysis
10
Key points from the analysis of the sample data in this project are summarized below:
 VDYP6 volumes are consistently higher than VDYP7 volumes.
 Volume trends in fir and larch leading polygons differ from volume trends in
other species (i.e. non-fir and non-larch) leading polygons. For fir and larch
leading polygons both yield models underestimate whole stem volume, on
average; for non-fir & non-larch leading polygons both yield models overestimate
whole stem volume.
 Based on attribute bias differences observed among the leading species strata, it is
suggested that non-fir and non-larch leading polygons be kept in a separate
stratum.
 Prior to any VRI Phase 2 sample selection, the FIP-based inventory should be
“completed” (i.e. the data should have its initial run through VDYP7), since
leading species (and hence stratum assignment) may change after “completion”.
 The CVs estimated from this project may need to be inflated prior to sample size
estimation to account for differences in plot design and volume utilization. This
should be discussed with FAIB staff.
 Based on the project CV% plus 5% to account for the differences above, it is
estimated that a VRI Phase 2 ground sample of 130 can achieve a 10% sampling
error target for total volume at a 95% confidence level.
 This data should be considered for further exploration in the upcoming VDYP7
sensitivity analysis.
February 2008
Cranbrook TSA: IDF and PP Ground Call Analysis
11
6 APPENDIX A
Project Background and Ministry Support
Cranbrook TSA Ground Call Analysis
A.1
Project Overview
Ministry of Forests Staff and Licensees in the Rocky Mountain Forest District are
concerned that the Forest Cover Inventory volumes in the Interior Douglas Fir and
Ponderosa Pine Biogeoclimatic zones of the Cranbrook Timber Supply Area are
overestimated. This project will undertake the volume compilation 52 ground samples
established in the summer of 2007 and analysis and comparison of field data and Forest
Cover attributes, as described in the contract Schedule A.
A.2
Project Background
Problem statement
Licensee and Ministry of Forests personnel in the Rocky Mountain Forest District
(RMFD) have expressed concern that forest inventory volumes in the Interior Douglas Fir
(IDF) and Ponderosa Pine (PP) Biogeoclimatic zones are overestimated. The issue was
raised in the VRI Strategic Inventory Plan (VSIP) meeting that recently took place for the
Cranbrook TSA.
VRI ground sampling is proposed in the VSIP, and inventory adjustment will correct the
inventory volumes that are found during sampling.
In order to determine the existence and extent of the problem an Inventory Assessment of
the volumes in these zones is proposed. This will allow the more costly phase 2 and
NVAF sampling to be more efficiently applied. The assessment will allow the phase 2
sampling to target strata where problems are actually observed, and provide baseline
coefficients of variation to help accurately define phase 2 sample sizes, thus reducing
phase 2 sampling costs.
A preliminary analysis of data collected on a different small project in the Wasa area
seems to suggest that overestimation of heights in the inventory may be a potential cause
of volume overestimation in these Biogeoclimatic zones.
Sample Selection Methodology
All forested polygons (>10% crown Closure and > 30 years of age) in the IDF and PP
Biogeoclimatic zones within the RMFD were extracted from the provincial forest cover
February 2008
Cranbrook TSA: IDF and PP Ground Call Analysis
12
inventory. From this overall population, areas that are in private lands, First Nations
Reserves, Parks and TFL’s have been excluded.
A 500m buffer was applied to the TRIM roads coverage and this was overlaid with the
target population described above. Any polygons that have a portion that falls within the
buffer were considered for sampling. Proximity to roads was used primarily to reduce
access costs (helicopter will not be required). There will be an unknown bias with this
method as some polygons within the larger population will not have a chance of being
sampled, but due to extensive road networks in the area, the risk of obtaining results that
do not reflect the population will be low. As the results of the project will be used to
refine further unbiased sampling (phase 2), and will not be used to adjust the inventory
itself, the risks posed are minimal.
Samples were selected using a process similar to the VRI Probability Proportional to Size
With Replacement (PPSWR) process. The total area of all polygons in the resultant
database was totalled and random numbers were generated between 0 and the total area
of all polygons. A polygon was selected if a generated random number was larger than
the accumulated total area corresponding to the polygon immediately preceding it, and
the random number was smaller than or equal to its accumulated area.
Initially the Cranbrook TSA portion of the district was sampled. A total of 52 samples
were established in the Cranbrook TSA.
In order to provide an unbiased sample location within the polygon, a random coordinate
start point within the buffer zone was selected at the sample selection stage. This may
result in high variability between the photo interpreted inventory and the ground data on a
polygon basis, but when summarized for the project will produce an unbiased and
statistically valid result.
Sample Establishment Methodology
The field sample design consisted of 3 point variable radius plots in each sample location
where the following data was collected:
 Sample, plot number
 Basal Area Factor
 Plot Type (Full/Half/Quarter)
 Tree number
 Species
 Beetle codes
 Diameter (on live trees only)
 Heights (on live trees only)
 Random Bearing
 1 Representative age of the leading and second species from the cluster
The field crew navigated to the coordinate given using GPS and establish the 3 point
transect on a random bearing determined from the VRI random number table.
February 2008
Cranbrook TSA: IDF and PP Ground Call Analysis
A.3
13
Ministry Support
The Ministry will provide ground call data, Forest Cover population data, and forest
cover data for the established samples in a MS Access database. A description of the
fields and tables included in the access database follows.
IDFPP3 is the ground call database. Below are the column headings.











“Sample” is the sample number. It will correspond with the "sample number"
column in the "sample list" database.
“BRG” is the bearing from the first plot in the sample to the next plot
“PLT” is the plot number. Note that there may not always be three plots.
“FHQ” is full, half or quarter plot. Quite often only one tree in each plot is
labelled with a F, H, or Q. The value applies to all trees in the plot. In plots where
none of the trees has been labelled as F, H, or Q, it is to be considered a full plot.
“BAF” is the basal area factor. Again there may be only one tree in each plot that
has a BAF.
“Bands” shows the number of relascope bands used in the plot. The number of
bands has been converted into a BAF where a relascope was used, so the Bands
column can be ignored.
“Tree” is the tree number. If the value here is "0" then there was no trees in the
plot, so make sure these trees are not included in the basal area calc.. There is one
tree 99 in the database, which would also not be included in the basal area.
“DBH”, and Height contain the diameter at breast height and .tree height
respectively.
“Age” is the age at breast height of the representative tree. The presence of an age
can be used as a flag for a representative tree. For almost all samples there will be
a leading and second species, but occasionally there may only be a leading.
“LEN” is the length in CM for age prorate. There is only one prorate length in the
database, the age is the counted age only, and does not take into account the
prorate, so an age corrected for breast height and prorate where applicable needs
to be calculated.
“Beetle” is the MPB codes.
The “Sample List” table is the PPSWR sample list that was selected for the project. The
"sample number" is the last column. This sample list includes a lot of extras, and covers
the entire Rocky Mountain Forest District. Only samples in the Cranbrook TSA portion
have been established. The "orgunit_cd" field can be used to tell which polygons are in
which TSA (DIN is Invermere, and DCB is Cranbrook). This field actually is the old
Forest District codes, but in the case of Cranbrook it corresponds with the TSA boundary
as well. The first 52 samples in Cranbrook that could be accessed were established, so
there will be some skipped samples.
The veg_Clip_cc10_age30 table is the entire population for the project, again the
Cranbrook TSA portion will have to be extracted.
February 2008
Cranbrook TSA: IDF and PP Ground Call Analysis
14
7 APPENDIX B
Ground and forest cover attribute ratios, for biogeoclimatic zone stratification
Table B-1: Ground and VDYP7 height and age means and ratios, overall and for biogeoclimatic zone strata
Mean age (yrs)
Mean height (m)
VDYP7 Age
Run
Stratum
ratio of means
n
Ground
Inventory
n
Ground
Inventory
1
4
all samples
IDF
PP
51
40
11
90
90
92
109
110
103
0.832 ±10.5%
0.816 ± 11.8%
0.894 ± 25.8%
51
40
11
20.2
20.0
20.8
21.6
21.6
21.7
VDYP7 Height
ratio of means
0.935 ±5.7%
0.929 ± 6.5%
0.958 ± 13.9%
Table B-2: Ground and VDYP7 basal area/ha and trees/ha at 7.5cm+dbh utilization means and ratios, overall and for biogeoclimatic zone strata
Mean basal area/ha @7.5cm+ (BA)
Mean trees/ha @7.5cm+ (TPH)
VDYP7 BA
VDYP7 TPH
Run
Stratum
ratio of means
ratio of means
n
Ground
Inventory
n
Ground
Inventory
1
4
all samples
IDF
PP
52
41
11
26.1
25.5
28.1
22.6
22.3
23.5
1.154 ±12.5%
1.143 ± 14.5%
1.196 ± 29.3%
52
41
11
758
755
767
758
751
789
0.999 ±20.8%
1.006 ± 23.2%
0.972 ± 55.5%
Table B-3: Ground & VDYP7 whole stem volume at 12.5cm+ dbh utilization means and ratios, overall and for biogeoclimatic zone strata
Mean vol/ha (WSV @12.5cm+ dbh)
VDYP7 WSV @12.5cm+ volume impact
ratio of means
Run
Stratum
Unadjusted
Ratio & sampling error
n
Ground
CV of ratio
Inventory (VDYP7)
% at 95% confidence
1
2
all samples
IDF
PP
52
41
11
177.9
173.1
195.7
160.3
160.2
160.6
1.110 ± 14.5%
1.080 ± 17.5%
1.218 ± 27.0%
52%
56%
40%
February 2008
Cranbrook TSA: IDF and PP Ground Call Analysis
15
8 APPENDIX C
Graphs of ground vs. VDYP7 forest cover attributes (diagonal line represents perfect correlation).
200
100
0
0
100
200
200
100
0
300
300
Ground age (yrs
300
Ground age (yrs
Ground age (yrs
300
0
100
VDYP7 inventory age (yrs)
100
0
300
Fig C-2: Lw leading age relationship
30
30
20
15
10
5
Ground height (m)
30
Ground height (m)
35
25
25
20
15
10
10
15
20
25
30
VDYP7 inventory height (m)
Fig C-4: Fd leading height relationship.
35
0
300
25
20
15
10
5
5
5
200
Fig C-3: Non-Fd, non-Lw leading age relationship
35
0
100
VDYP7 inventory age (yrs)
35
0
0
VDYP7 inventory age (yrs)
Fig C-1: Fd leading age relationship.
Ground height (m)
200
200
0
5
10
15
20
25
30
VDYP7 inventory height (m)
Fig C-5: Lw leading height relationship
35
0
0
5
10
15
20
25
30
35
VDYP7 inventory height (m)
Fig C-6: Non-Fd, non-Lw leading height relationship
February 2008
40
20
0
20
40
60
VDYP7 basal area/ha @7.5cm+ dbh
0
0
20
40
60
Ground trees/ha @7.5cm+ dbh
1,500
1,000
500
0
500
1,000
1,500
2,000
VDYP7 trees/ha @7.5cm+ dbh
Fig C-10: Fd leading trees/ha at 7.5cm+ dbh
relationship.
2,500
20
0
0
20
40
60
2,500
2,000
1,500
1,000
500
0
40
Fig C-9: Non-Fd, non-Lw leading basal area/ha at
7.5cm+ dbh relationship
2,500
2,000
60
VDYP7 basal area/ha @7.5cm+ dbh
Fig C-8: Lw leading basal area/ha at 7.5cm+ dbh
relationship
2,500
Ground trees/ha @7.5cm+ dbh
20
VDYP7 basal area/ha @7.5cm+ dbh
Fig C-7: Fd leading basal area/ha at 7.5cm+ dbh
relationship.
0
40
Ground trees/ha @7.5cm+ dbh
0
60
Ground basal area/ha @7.5cm+ dbh
60
16
Ground basal area/ha @7.5cm+ dbh
Ground basal area/ha @7.5cm+ dbh
Cranbrook TSA: IDF and PP Ground Call Analysis
0
500
1,000
1,500
2,000
VDYP7 trees/ha @7.5cm+ dbh
Fig C-11: Lw leading trees/ha at 7.5cm+ dbh
relationship
2,500
2,000
1,500
1,000
500
0
0
500
1,000
1,500
2,000
2,500
VDYP7 trees/ha @7.5cm+ dbh
Fig C-12: Non-Fd, non-Lw leading trees/ha at 7.5cm+
dbh relationship
February 2008
Cranbrook TSA: IDF and PP Ground Call Analysis
17
400
300
200
100
0
0
100
200
300
400
500
VDYP7 WSV @12.5cm+ dbh
Fig C-13: Fd leading whole stem volume at 12.5cm+
dbh relationship.
500
Ground WSV @12.5cm+ dbh
500
Ground WSV @12.5cm+ dbh
Ground WSV @12.5cm+ dbh
500
400
300
200
100
0
0
100
200
300
400
500
VDYP7 WSV @12.5cm+ dbh
Fig C-14: Lw leading whole stem volume at 12.5cm+
dbh relationship
400
300
200
100
0
0
100
200
300
400
500
VDYP7 WSV @12.5cm+ dbh
Fig C-15: Non-Fd, non-Lw leading whole stem volume
at 12.5cm+ dbh relationship
February 2008
Cranbrook TSA: IDF and PP Ground Call Analysis
18
February 2008