2010 HFQLG Soil Monitoring Report
Prepared by:
Feb 25, 2011
David Young, R5 North Zone Soil Scientist, Redding, CA
Colin Dillingham, HFQLG Monitoring Program Coordinator, Quincy, CA
Jim Baldwin, Station Statistician, PSW Research Station, Albany, CA
This report summarizes soil monitoring data collected as part of the Herger - Feinstein Quincy Library
Group (HFQLG) Forest Recovery Act Pilot Project. The soil monitoring is required by the HFQLG EIS to
answer: Question 6) Do Activities meet Soil Quality Standards?
Soil quality standards and guidelines for the 3 HFQLG forests are found in the Land and Resource
Management Plan (Forest Plan) for each Forest, and are not repeated here. Generally, each Forest has
similar standards placing limits on soil compaction, topsoil displacement, soil cover retention, and large
woody material retention. Refer to the HFQLG monitoring plan for specifics on soil quality standards,
and monitoring protocols intended to address Question 6. The purpose of this report is to outline the
existing standards and determine compliance of HFQLG activities; validation of standards and discussion
of their application relevant to current science are beyond the scope of this report.
Soil quality standards are conventionally applied on a per-activity-unit basis, so each unit has a pass-fail
result for each of the several soil quality elements being assessed. Kinds of activities (silvicultural
methods) may be expected to have different risks and results. Some units have integrated mitigation
measures, such as subsoiling to help reduce compaction. Some units have been logged over snow, so
they may have different kinds or amount of impacts. The data set has become large enough to make
better inferences about such differences in effects with more confidence than previously.
The Data: Review of Soil Conditions Before and After Treatment, 2001-2010
2010 soil monitoring data was appended to the cumulative data set analyzed and reported on annually
to determine effects of HFQLG management activities on the soil resource. Pre-activity soil monitoring
began in 2001, and repeated post-activity monitoring began in 2004. A total of 107 units with pre + post
data have been sampled through the 2010 season. Only units with both pre- and post-treatment data
were included in the analysis, in order to separate current treatment effects from lasting prior impacts
(“legacy” impacts) – changes as a result of present activities are of primary interest.
Table 1. Silvicultural Units Included in the Data Set.
2001-2009
Thinning Units
57
Group Selection Units
26
Thin + Group (mixed sampling)
0
Mastication Units
2
Total
85
2010
9
11
2
0
22
Total
66
37
2
2
107
Detailed statistical analyses were first done in 2007 and repeated this year by Jim Baldwin of PSW
Research Station. 2007 results revealed a need to increase sample size to make better estimates of
change. Therefore sample size in the data set is mixed: all pre-activity sampling and post-activity
sampling prior to 2008 generally have 60 sample points for thinning units and 21 sample points for
group selection units; all units sampled post-activity since 2008 (56 of the 107) have 200 sample points.
1
Data variability and mixed sample size will continue to limit the ability to detect changes with statistical
accuracy or precision. Nevertheless, the data set is large, and robust for operational monitoring.
Overall Results
Of primary interest is the overall status of activity units relative to soil quality standards and guidelines:
How many of the activity units are meeting the Soil Quality Standards? Figure 1 displays results for all
units, both pre- and post-activity, regardless of silvicultural method or other operational differences.
Units Complying with Soil Quality Standards
95.3
100
90
83.2
86.0
90.7
PRE-TREATMENT
POST-TREATMENT
PERCENT OF UNITS
80
70
65.4
69.2
61.7
60
50
43.0
40
30
20
10
0
Det. Compaction
Standard: < 15% area
Det. Displacement
< 15% area
Soil Cover
> 50%
Large Woody Debris
>3 logs/acre
Figure 1 – Percentages of units meeting various soil quality conditions, pre- and post-activity.
Overall status and trend of units indicate generalized results as follows:
1. 85-90% of activity units are meeting soil quality standards for soil displacement and cover
retention, both pre- and post-activity.
2. 62% of activity units are meeting soil quality standards for compaction; compaction levels
were similar pre-activity, representing persistent legacy impacts from pre-HFQLG activities.
3. 43% of activity units are meeting soil quality standards for large wood retention; HFQLG
activities are affecting this parameter in a considerable number of units (particularly group
selection units), as reported previously.
Following is more detailed information and discussion for each of the soil quality monitoring elements,
including differences between silvicultural methods, and recommendations as applicable. Mastication
and ‘thin + group’ units will not receive much detailed discussion because of the limited number of
units. Tabular results of detailed statistical analyses are included below in Appendix 1, including
probabilities and confidence intervals for the various metrics.
2
Soil Compaction
Soil compaction is loss of soil porosity due to the physical force of heavy equipment traffic. Forest Plan
soil quality standards define compaction as “detrimental” when more than 10% of the total porosity is
lost (severity of compaction), and further, this detrimental condition cannot occupy more than 15% of
an activity area post-activity (extent of compaction). Small amounts of detrimental compaction
commonly occur, and are not of concern unless exceeding 15% of the area.
Overall, 62% of the units meet this standard post-activity, including 55% of thinning units and 73% of
group selection units (figure 2). However, only 65% of the overall units met the standard pre-activity
(59% of thinning units and 76% of group selection units), indicating that most of the detrimental
compaction existed pre-activity, persisting from legacy activities. More pertinent to current activities,
there were 10 units (6 thinning, 4 group, 9%) that met the standard pre-treatment and exceeded it posttreatment; the rest either exceeded the standard pre-treatment or met the standard post-treatment (or
both, which is why some percentages do not appear to reconcile).
Detrimental Compaction - Units with < 15% Area
100
PRE
90
POST
75.7
PERCENTAGE OF UNITS
80
70
65.4
61.7
60
73.0
59.1
54.5
50
40
30
20
10
0
ALL UNITS
Thinning
Group Selection
Figure 2 – Percentages of units meeting compaction standards, pre- and post-activity.
Figure 3 displays detrimental compaction as an average percent of unit area (extent) across units.
Variation in the data is large, indicating that some units exceed the standard by large margins, both pre
and post. Levels of compaction in group selection units are roughly half that of thinning units, which is
unexpected but partly explained in discussion below. Figure 4 displays the full range of compaction
results post-activity; some of the numbers are quite high, and it is important to reiterate that most of
these compaction levels were very similar pre-activity.
3
Compaction - Average Percent Detrimental
50
PRE
45
POST
MEAN OF UNITS (% area)
40
35
30
25
18.5
20
14.6
15
16.6
14.0
8.4
10
9.8
5
0
ALL UNITS
Thinning
Group Selection
Figure 3 – Average extent of detrimental compaction within units (and standard deviation).
Distribution of Units by Compaction Level (Post-Activity)
50
Thinning
PERCENTAGE OF UNITS
45
Group Selection
40
35
30
25
20
15
10
5
0
DETRIMENTAL COMPACTION (% of unit area)
Figure 4 – Distribution of units by post-activity compaction level.
Compaction levels in many units were modified by subsoiling practices, used to reduce/repair the worst
areas of compaction in a given unit. A greater proportion of group selection units received subsoiling
treatments versus thinning units (73% vs. 61% respectively), because groups are expected to have
greater impacts from harvest activities. Average compaction levels in subsoiled versus not-subsoiled
units are similar (figure 5). Compaction was still found to exceed standards in 45% of thinning units and
4
30% of group selection units that were subsoiled. As stated, subsoiling is generally focused on the worst
areas in a unit (landings, primary skid trails); it is apparent in reviewing unit-level raw data that few
sample points encounter subsoiled skid trails in subsoiled units, so effects of mitigation are not often
expressed in unit averages, even if on-site results are effective where applied.
Detrimental Compaction and Subsoiling (post-activity)
50
Not Subsoiled
MEAN OF UNITS (% area)
45
Subsoiled
40
35
30
25
20
N = 26
15
10
N = 40
N = 10
5
N = 27
0
Thinning
Group Selection
Figure 5 – Post-Treatment detrimental compaction with and without subsoiling.
Discussion/Recommendations:
It is foremost important to conclude that while 38% of units are exceeding compaction standards, 35%
of them exceeded the standard pre-activity from residual legacy impacts. Overall change in compaction
levels is not large. 10 of the 107 units (9%) changed from meeting the standard pre-activity to exceeding
it post-activity, which is the most pertinent result of current activities.
Group selection units are expected to have more concentrated impacts and more resulting compaction
than thinning units, at least in the absence of subsoiling. Results are counter to expectations: a smaller
proportion of thinning units are compliant with the compaction standard (fig. 2), and group selection
units appear to have less extent of compaction on average (fig. 3). A few factors partly explain these
results.
Sample size was much smaller in group selection units for all pre-treatment data and post-treatment
data prior to 2008, and was previously determined to be inadequate for statistical accuracy or precision.
Problems with sampling methodology have been discussed in previous reports, and revised to address
the problems, but the ‘small-sample’ data still comprises a large part of the data set. It is possible that
compaction in groups was simply under-sampled and underestimated.
There are also 6 thinning units with very high levels of compaction inflating the means (fig. 4). Five of
the six had similarly high levels of compaction pre-activity, and four of them occur in a single sale area
5
(Pittville, Hat Creek RD) noted to have extensive legacy skid trails. If these are taken out, thinning units
average less than 15% compaction also, but the data is retained as real (i.e. not sampling error).
It is also possible that subsoiling is more effective in reducing means of group selection units, because
more of them were subsoiled, and more of the unit (being small) is generally subsoiled when conducted.
However, there are several uncertainties from the data regarding subsoiling effectiveness, primarily
because very little actual subsoiled ground is represented in the data at the unit level. It is therefore
unclear whether not enough mitigation is being done, treatment is ineffective, or legacy compaction is
causing misleading results. A more detailed review and analysis is necessary to make inferences on this.
Given the cost and logistics involved with subsoiling, its effectiveness in repairing compaction should be
evaluated, versus cost and logistics of preventing/limiting compaction in the form of limitations imposed
on equipment use during harvest.
Soil Displacement
Forest Plan soil quality standards and guidelines for displacement do not have a minimum contiguous
area considered significant, or a permissible extent within units, but minimizing soil displacement is an
explicit management objective. For HFQLG projects, soil displacement is considered “detrimental” when
either 2 inches or 1/2 the total thickness (whichever is less) of the humus-enriched topsoil (A horizon) is
removed from an area of 1 square meter or larger. Figure 6 and figure 7 display statistics for
displacement across units, including pre- and post-treatment. Overall, units average 7% detrimental
displacement, with 86% of units having less than 15%.
Displacement - Units with < 15% Area
95.5
100
90
83.2
86.0
78.4
80
PERCENTAGE OF UNITS
PRE
86.4
POST
73.0
70
60
50
40
30
20
10
0
ALL UNITS
Thinning
Group Selection
Figure 6 – Percentages of units with less than 15% detrimental displacement, pre- and post-activity.
Thinning units average 5% displacement, with 3 units (5%) exceeding 15%. Group selection units
average 10% displacement, with 10 units (27%) exceeding 15% and 2 of them exceeding 25%.
Detrimental displacement exceeded 15% in one of the two ‘thin + group’ units (18% area), and one of
6
the two mastication units (35% area). Displacement averages overall were quite similar pre-activity, but
individual unit results varied greatly.
Displacement - Averages Across Units
50
PRE
45
POST
MEAN OF UNITS (% area)
40
35
30
25
20
15
10
7.0
7.3
9.2
5.8
9.6
5.4
5
0
ALL UNITS
Thinning
Group Selection
Figure 7 – Detrimental displacement by silvicultural method (with standard deviations).
Discussion/Recommendations:
Although Forest Plans have no explicit quantifiable “standard” for displacement, criteria are defined for
HFQLG projects for what constitutes an occurrence of “detrimental displacement,” and conventionally
use a 15% area extent as a warning threshold, similar to compaction. Displacement criteria are difficult
to apply on the ground, meaning it is difficult to determine with certainty if 2 inches or half of the
topsoil has been removed, because of natural variation in micro-topography and A horizon thickness.
Given these uncertainties, it is nevertheless desirable to report on status & trend of units for this
parameter, as Regional soil quality standards have historically regarded displacement as a degrading
type of soil disturbance.
Overall 86% of units have less than 15% detrimental displacement. Group selection units clearly have a
higher incidence of displacement, which is expected operationally. In the two groups exceeding 25%,
displacement was noted as due to post-harvest pulling and piling of Manzanita for follow-up fuel
reduction treatment; this was also the case in some of the other units exceeding 15%. It is a general
recommendation for contract administration staff to work with operators to minimize displacement, by
trying to streamline movement of harvest equipment (i.e. less turning, blading, etc.), and attention to
excavator brush removal operations.
Soil Cover
Forest Plan soil quality standards generally require 50% effective soil cover to prevent soil erosion. This
standard is met overall in 95% of units pre-activity and 91% of units post-activity (fig. 1). Effective cover
7
can be duff & litter, large wood, vegetation or rock, all of which help protect otherwise bare soil from
eroding; cover physically protects the soil from rain-splash and dissipates runoff energy. Cover is
calculated as everything not “bare” at the “toepoint” sample spot (several square inches in size).
Average soil cover was quite similar between silvicultural methods pre-activity, with 70-75% duff cover
and 10-15% bare. Differences between methods are apparent post-activity (figure 8).
Thinning units average 90% effective soil cover pre-activity and 82% post-activity; only 1 unit had less
than 50% cover post-activity. Group Selection units averaged 83% cover pre-activity and 64% postactivity; 9 of the 37 units (24%) resulted with less than 50% cover. Duff is the most effective cover in
preventing erosion, which is much more reduced in group selection units. Mastication and ‘thin +
group’ units all exceeded 80% cover post-activity (not shown).
Post-Treatment Soil Cover
90
AVERAGE PERCENT COVER
80
Thinning
77.0
Group Selection
70
60
52.6
50
36.2
40
30
17.8
20
8.6
10
1.1 1.4
3.2
0.9 1.2
0
duff
rock
veg
lwd
bare
SOIL COVER COMPONENT
Figure 8 – Grand-average post-treatment soil cover by component (and standard deviation).
Discussion/Recommendations:
Thinning units nearly all have at least 50% soil cover post-activity; only a single unit was found lacking in
cover, due to duff consumption associated with follow-up prescribed burning. Group selection units
appear at first glance to have higher risks: 9 of 37 units were found with <50% cover. Two of these
(Claw project) were also lacking cover pre-activity, noted to have shallow rocky soils with sparse
vegetative productivity and little duff. Six other units (PEG21 project) were noted as lacking cover due
to extensive subsoiling activity to reduce compaction – representing a management trade-off to reduce
one kind of disturbance and increase another. Presumably soil cover will naturally recover more quickly
than compaction, as inferred from compaction persisting long-term from prior activities (fig. 2). The last
group unit lacking cover (Red Clover 2-20) had no notes to explain a reason for only 38% cover.
8
It therefore appears that most all of the units found lacking cover had legitimate reasons for this result,
and were not due to lack of operational controls or sampling error. While group selection units are
expected to have more concentrated impacts, 28 of 37 units (76%) are meeting the soil cover standard.
While the 50% soil cover standard is a good warning signal of a potential erosion hazard, size and
distribution of bare areas are more important than percentage of a unit, especially when percentage is
measured from just “toepoints.” Erosion hazard of bare areas varies by site-specific factors such as soil
type (erodibility), slope gradient, and topography, as well as unit configuration and proximity to streams.
Group selection units not meeting the standard do not necessarily pose high risks for erosion or
sediment delivery, as they are generally quite small and well buffered from streams in the landscape.
Any units where bare areas are concentrated in sizeable, contiguous portions of the unit have higher
erosion potential. It is recommended that size and distribution of bare areas continue to be
qualitatively evaluated and described in notes during post-activity sampling efforts to identify problem
areas needing attention and follow-up mitigation.
Large Woody Debris
Large woody debris is described as downed large logs in decay classes 1-5, with “large” meaning at least
10’ long and 20” diameter. Forest Plan soil quality standards generally require 3 or more such logs per
acre to be left on site post-treatment. Figure 9 displays percentage of units either meeting the standard
or having no down woody debris at all, and figure 10 displays average logs per acre across units. Overall,
units average 3.4 logs/acre, but only 43% of units actually meet the standard post-activity; 69% of the
units met the standard pre-activity, and 20% had no down wood at all pre-activity. From pre- to postactivity, both the average logs/acre and the number of units complying with the standard are
decreasing, particularly for group selection units, as reported previously.
Units With and Without Large Woody Debris
100
PRE
90
POST
74.2
PERCENT OF UNITS
80
69.2
70
59.5
57.6
60
50
43.0
59.5
40.5
40
30
27.1
19.6
20
13.5
7.6 9.1
10
0
No Down
Wood
3 or More
Logs per Acre
ALL UNITS
No Down
Wood
3 or More
Logs per Acre
Thinning
No Down
Wood
3 or More
Logs per Acre
Group Selection
Figure 9 – Percentages of units with large woody debris condition post-activity.
9
Thinning units as a group meet the standard with 4 logs per acre post-activity. More specifically, 38
units (58%) have at least 3 logs/acre, 22 units (33%) have 1-2 logs/acre, and 6 units (9%) have no large
wood. Both of the ‘thin + group’ units met the standard post-treatment, and 1 of the 2 mastication
units did not meet the standard, both pre- and post-activity.
Aggregated group selection units do not meet the standard, averaging 1.4 logs per acre post-activity.
Only 5 units (14%) have at least 3 logs/acre, 10 units (27%) have 1-2 logs/acre, and 22 units (60%) have
no large wood. However, 40% of the group selection units had no large wood prior to treatment.
Large Woody Debris - Averages Across Units
24
PRE
21
MEAN OF UNITS (% area)
POST
18
15
12
9.8
9.0
9
7.6
6
3.4
4.3
3
1.4
0
ALL UNITS
Thinning
Group Selection
Figure 10 – Large woody debris by silvicultural treatment (with standard deviations).
Individual unit results are highly variable, particularly pre-activity but also post-activity (fig. 10). Some
units had no wood, some had copious amounts of large wood: as much as 35-45 logs/acre pre-activity
and 15-20 logs/acre post-activity; both of these conditions affect overall means substantially.
Discussion/Recommendations:
Soil quality standards are intended to be evaluated and applied on an individual unit basis. However,
large down woody debris is a highly variable metric: large down logs are distributed unevenly across the
landscape and commonly occur in clumps, in both natural and managed stands. If a unit has little or no
wood prior to treatment, it cannot be expected to meet the standard post-treatment. Therefore a
portion of units (at least 20%, fig. 9) are simply unable to meet the standard, as evaluated on a per-unit
basis, even in the absence of management activities.
Fire history, stand history, and stand age all have pronounced influences on occurrence of large down
wood. Because of high variability across the landscape, it may be most appropriate to analyze this
standard based on groups of units, aggregated by sale area, watershed, or aspect within larger HUC
watersheds. Results reported above as groups of like silvicultural treatments should present a clearer
10
picture on general effects of management activities. By whatever grouping, it is apparent that HFQLG
activities are causing overall declines in large woody debris, with less than half of units meeting the
standard. Recommendations have already been made to management to help keep future operations in
better compliance with large woody debris retention standards.
Operations were conducted in part for fuel reduction objectives, so managers would have aimed to
remove most “extra” down wood, retaining just above 3 logs/acre when present to begin with.
Managers do not typically retain “extra” large wood in some units to compensate for other units
without wood pre-activity, but evaluate and manage on a per-unit basis.
Large woody debris is conventionally presumed to be important for soils in holding moisture and
providing habitat for wildlife, arthropods, and microbes, which in turn contribute to nutrient cycling and
long-term soil productivity. Large woody debris also comprises 1000-hour fuels, which can severely
impact soils underneath when they burn. Large wood can therefore be a benefit or detriment to soils,
and objectives for managing this ecological component need to be balanced accordingly.
11
APPENDIX 1.
Contained in Appendix 1 are tabular results of detailed statistical analyses performed by Jim Baldwin,
Station Statistician with PSW Research Station, Albany, CA. There are minute differences in some of the
reporting statistics from the body of the report above and the appendix below, because of slightly
different calculation methods. Differences are very minor, and numbers above and below are closely
alike and reliable for overall reporting of status and trend.
Soil Compaction
The percent of samples from each unit for both the pre and post-treatment periods with detrimental
compaction were determined. Table A-1 displays summaries for each treatment, time period (pre and
post), and harvested over snow status. In addition, statistical test of the hypothesis that the mean
detrimental compaction percentage was 15% was performed. Only group selection units were found
significantly lower than the standard of 15% at the 95% confidence level.
Table A-1. Mean percentages of tile-spade determinations exhibiting soil compaction, along with 95%
confidence and prediction intervals, the number of units (N), and standard error of the mean.
Type
Harvested
over
Snow?
No
All
Yes
No
Thin
Yes
No
Group
Select
Yes
No
GS
MT
Yes
No
Mast
Yes
Time
Period
Pre
Post
Pre
Post
Pre
Post
Pre
Post
Pre
Post
Pre
Post
Pre
Post
Pre
Post
Pre
Post
Pre
Post
95%
Confidence
Interval for
Mean
N
99
8
62
4
33
4
2
0
2
0
Upper
Std.
Err.
11.4
18.9
1.9
14.7
11.7
17.6
7.9
0.0
9.8
Mean
Lower
15.2
P-value
For
H0:
Mean=15%
95% Prediction
Interval for
Individual Units
Lower
Upper
0.924
0.0
52.5
1.5
0.823
0.0
44.4
18.8
4.6
0.167
0.0
38.6
0.0
22.4
5.3
0.362
0.0
45.4
13.2
24.1
0.185
0.0
61.7
17.0
12.7
21.2
2.1
0.363
0.0
50.7
15.8
0.0
39.8
7.5
0.919
0.0
63.8
19.3
0.0
46.4
8.5
0.648
0.0
73.4
5.4
13.3
0.006
0.0
32.1
10.8
7.1
14.4
1.8
0.025
0.0
31.8
0.0
0.0
0.0
0.0
-
-
-
0.3
0.0
1.3
0.3
0.000
0.0
2.3
6.7
0.0
91.4
6.7
0.430
0.0
100.0
4.7
0.0
15.2
0.8
0.051
0.0
19.6
-
-
-
-
-
-
-
-
-
-
-
-
-
-
12.5
0.0
100.0
12.5
0.874
0.0
100.0
17.5
0.0
100.0
9.2
0.830
0.0
100.0
-
-
-
-
-
-
-
-
-
-
-
-
-
-
18.7
9.3
2.7
1.9
12
From the above values the mean change across all units is calculated which characterizes the effect of
the treatment. A paired t-test was performed to test the hypothesis of no change separately for units
harvested over snow and those not harvested over snow and for the applied treatments. Table A-2
displays the results of those tests. None of the tests were statistically significant at the 5% level of
significance.
Table A-2. Summary of change in mean percentages of tile-spade assessments of soil compaction along with
95% confidence intervals, the number of units (N), and the standard error of the mean difference for various
types of treatment and harvested-over-snow status.
95% Confidence
Harvested
Mean
Interval for Difference
Over
Difference
Type
Snow?
N (Post – Pre)
Lower
Upper
t-value P-value
No
99
-0.5
-3.1
2.1
-0.39
0.695
All
Yes
8
1.9
-0.8
4.6
1.63
0.146
No
62
-1.7
-5.2
1.7
-0.99
0.327
Thin
Yes
4
3.5
-3.3
10.2
1.64
0.200
No
33
1.5
-3.1
6.0
0.65
0.520
Group Select
Yes
4
0.3
-0.7
1.3
1.00
0.391
No
2
-1.9
-76.1
72.3
-0.33
0.796
GS MT
Yes
0
No
2
5.0
-37.4
47.4
1.50
0.374
Mast
Yes
0
-
Std.
Err.
1.32
1.16
1.73
2.12
2.24
0.31
5.84
3.33
-
Soil Cover and Soil Displacement
Mean soil cover for all post-treatment units is summarized below in Table 4:
Table A-3. Mean percent soil cover for various treatments along with 95% confidence limits for the mean, the
number of units (N), and the standard error of the mean.
95% Confidence
Interval for
Mean
N
Mean
Soil Cover
(%)
Lower
Upper
Std.
Err.
107
75.8
72.8
78.8
1.5
Thin
66
82.1
79.5
84.7
1.3
Group Select
37
63.8
58.2
69.4
2.8
GS MT
2
80.9
63.0
98.8
1.4
Mast
2
86.7
65.5
107.8
1.7
Type
All
13
Post-treatment units with more than 15% of the samples having soil displacement were summarized as
to the associated mean amount of soil cover. The standard errors and 95% confidence intervals for the
mean soil cover are also displayed in Table A-4.
Table A-4. Mean soil cover for units with more than 15% detrimental displacement. Included are the number of
units involved, 95% confidence limits for the mean, and the standard error of the mean.
Type
N
All
95% Confidence
Interval for
Mean
Mean
Soil Cover
(%)
Lower
Upper
Std.
Err.
12
68.4
59.2
77.7
4.2
Thin
1
87.8
-
-
-
Group Select
9
63.2
53.4
73.0
4.3
GS MT
1
79.5
-
-
-
Mast
1
85.0
-
-
-
Another display showing differences between pre and post-treatment detrimental displacement is
shown below.
100
90
Group Select
Thinning Units
80
72.7%
Percent
70
60
50
40.5%
40
30
35.1%
24.3%
20
15.2%
12.1%
10
0
None
1-10%
>10%
Figure A-1. Percentage of post-treatment units with specified amounts of detrimental displacement.
14
Large Woody Material
The number of logs for each sample of a quarter acre plot was recorded. Below are summary tables
displaying the mean number of logs per acre across all units along with the associated standard error and
95% confidence limits for large woody material in classes 1 to 3, 4 and 5, and then all classes combined.
Table A-5. Summary of post treatment plots and average number of logs/acre from decomposition classes 1 to
3 along with 95% confidence intervals, the number of units (N), and the standard error of the mean for various
types of treatment.
95% Confidence
Interval for Mean
N
Average
Logs/acre
Lower
Upper
Std.
Err.
107
1.6
1.2
2.0
0.2
Thin
66
1.9
1.4
2.3
0.2
Group Select
37
2.6
0.9
4.3
0.8
GS MT
2
49.0
0.0
315.8
21.0
Mast
2
1.7
0.0
22.8
1.7
Type
All
Table A-6. Summary of post treatment plots and average number of logs/acre from decomposition classes 4 and
5 along with 95% confidence intervals, the number of units (N), and the standard error of the mean for various
types of treatment.
95% Confidence
Interval for Mean
N
Average
Logs/acre
Lower
Upper
Std.
Err.
107
1.9
1.4
2.4
0.3
Thin
66
2.7
1.9
3.4
0.4
Group Select
37
0.4
0.0
0.9
0.2
GS MT
2
3.8
0.0
12.9
0.7
Mast
2
1.7
0.0
22.8
1.7
Type
All
15
For the assessment of all classes of woody debris (decomposition classes 1 through 5), a test was
performed to determine if the threshold of at least 3 logs per acre were met.
Table A-7. Summary of post-treatment units and average number of logs/acre from decomposition classes 1
through 5 along with 95% confidence intervals, the number of units (N), and the standard error of the mean for
various types of treatment.
95% Confidence
Interval for Mean
P-value for test of
H0: mean = 3 logs/acre
N
Average
Logs/acre
Lower
Upper
P-value
Std.
Err.
107
3.5
2.7
4.3
0.211
0.4
Thin
66
4.5
3.5
5.5
0.003
0.5
Group Select
37
1.4
0.4
2.5
0.006
0.5
GS MT
2
8.7
0.0
23.0
0.125
1.1
Mast
2
2.1
0.0
28.6
0.736
2.1
Type
All
For post-treatment units the percentage of units with a mean of 3 or more logs per acre and the
proportion of sites with no down wood are summarized in the table below. Following that is a figure
showing the same information.
Table A-8. Summary of post-treatment units with respect to the percentage of units with 3 or more logs per
acre and no down wood using along with the associated 95% confidence intervals, the number of units (N), and
the standard error of the mean percentage for various types of treatment.
95% Confidence
Interval for Mean
N
Percentage
Lower
Upper
Std.
Err.
107
43.9
34.4
53.5
4.8
Thin
66
59.1
46.9
71.3
6.1
Group Select
37
13.5
2.0
25.1
5.7
GS MT
2
100.0
100.0
100.0
0.0
Mast
2
50.0
0.0
100.0
50.0
107
27.1
18.5
35.7
4.3
Thin
66
9.1
2.0
16.2
3.6
Group Select
37
59.5
42.9
76.1
8.2
GS MT
2
0.0
0.0
0.0
0.0
Mast
2
50.0
0.0
100.0
50.0
Variable
Type
All
Proportion of sites
with 3 or more
logs per acre
All
Proportion of sites
with no down wood
16
100
Group Selects
Thinning Units
Percent of units
80
60
59.5
59.1
40
20
13.5
9.1
0
No Down Wood
(all classes)
3 or more logs/acre
(all classes)
Figure A-2. Post-treatment large down woody material (decomposition classes 1-5).
17