HFQLG Soil Moisture Monitoring – Aug 2009 to Sep 2012
Prepared by:
David Young, North Zone Soil Scientist, Redding, CA (USFS, Region 5)
Colin Dillingham, HFQLG Monitoring Coordinator, Quincy, CA (USFS, Plumas NF)
Jianwei Zhang, Research Silviculturist, Redding, CA (USFS, PSW Research Station)
Executive Summary
Continuous data-logging equipment was used to monitor soil moisture trends at two HFQLG activity areas from
2009 to present (one site from 2009-2011, one from 2011-present using the same equipment). Both sites had
multiple paired activity units, comparing treated (thinned) and adjacent unthinned stands. Time since
treatment varied for the sites. The units at Meadow Valley had thinning treatments completed in 2005-2007.
Monitoring at Franc began the first year after treatments were completed, when differences due to treatment
should be greatest. Soil moisture sensors, half with attendant soil temperature data, were installed at 10 inch
increments from 10-40 inches depth in the soil profile. At both sites, differences between soil depths and stand
treatments were highly significant (P < 0.0001), although trends were not consistent between sites and absolute
differences are relatively small.
Treated stands at Meadow Valley were on average dryer, having -5.1% volumetric water content (VWC) during
the growing season and -3.6% VWC during the non-growing season. At Franc treated stands were more moist
on average, with +1.5% VWC during the growing season and +1.4% VWC during the non-growing season. Soil
moisture differences were not attributed to soil temperature differences, which were +1.2-1.9⁰C (+2.2-3.6⁰F)
during the growing season at both sites, and -0.07⁰C (0.13⁰F) during the non-growing season at both sites.
Trends are not universal at all soil depths or at all unit-pair replicates at each site, but overall effects are
statistically clear. It must be noted that the absolute magnitude of differences are small enough to be within the
error range for the technical accuracy of the soil sensors, so from an engineering view results are questionable;
to waive this objection one must be willing to assume that sensors should mostly err in the same direction
within comparable soils. In the authors’ opinion this is a reasonable assumption.
Introduction
The original monitoring plan conducted as part of the HFQLG pilot program outlined monitoring questions and
specified monitoring protocols meant to address those questions. One element related to soil moisture:
Question 20): What is the effect of the proposed treatments on a) modeled water yield and
b) soil moisture characteristics?
Original monitoring protocols may be found in the HFQLG Monitoring Plan, and will not be repeated here.
Monitoring was conducted by Wayne Johannsen (Plumas NF soil scientist, retired), from 2001 to 2004. He
generally found no soil moisture differences as a result of thinning and fuel reduction treatments. Because of
the lack of differences, and the retirement of Wayne, further soil moisture monitoring was discontinued.
The Pinchot Institute for Conservation, in response to a Forest Service request, formed an Independent Science
Panel to carry out a review of monitoring pursuant to the HFQLG pilot program. Phase One review was
completed in 2008, with the purpose of providing feedback helpful in making changes to the monitoring
program prior to a more intensive review (Phase Two) and reporting to Congress. Among the Phase One
recommendations was one regarding soil moisture:
HFQLG Soil Moisture Monitoring Report – Meadow Valley and Franc
Page 1
“Soil Moisture. Although evaluation of soil moisture in early years did not identify a significant
difference between pre-treatment and post-treatment areas, the Panel recommends that soil
moisture content sampling be continued because changes in soil properties may evolve over time.
Testing during a single year so soon after treatment may not be adequate to characterize
potential effects of the treatments on soil properties.”
In 2009 soil moisture monitoring efforts were renewed, and protocols revised. Previous monitoring utilized a
hand-held electronic soil moisture meter, requiring site visits at a point of time between August and September.
Thus, soil moisture for each unit was represented by a single date, before and after treatments occurred. For
renewed efforts, the HFQLG monitoring program funded the purchase of soil moisture sensors and dataloggers
for continuous data recording, to enable soil moisture comparisons throughout the entire growing season. The
equipment was installed in the Meadow Valley Sale Area (Mt. Hough Ranger District, Plumas NF) from 2009 to
2011, and moved to the Franc Sale Area (Sierraville Ranger District, Tahoe NF) from 2011 to present.
The “treatments” consisted of commercial thinning and fuel reduction activities which emphasized thinning
from below and removal of surface and ladder fuel components. Group selection units were not chosen for this
monitoring. When comparing to an unthinned stand, one may expect warmer soil temperatures due to
reduction of canopy cover and increased solar exposure. This should indirectly increase microbial and root
activity in the soil, and evapotranspiration rates of individual trees. Effects upon soil moisture may be: 1) drier
soil conditions due to evaporative loss with warmer temperatures and reduction in soil cover; 2) wetter soil
conditions due to fewer evapotranspiration ‘pumps’ in the stand; 3) seasonally dependent effects; 4) temporal
effects depending on time since treatment. Any such effects should be temporary in a thinning scenario, with
site resources (nutrients and water) merely reallocated to fewer trees, in theory, although it should presumably
take a few years for residual trees’ root systems to expand and fully reoccupy the soil volume.
Warmer soils could perhaps accelerate the growth period and shorten the growing season to a soil-dry dormant
period, resulting in the same productivity, just occurring faster. It is generally assumed that plant available soil
water holding capacity should not be appreciably affected by activity operations as a result of near-surface
compaction. The direct and indirect effects of soil environment changes due to such vegetation management
activities are largely speculative, and whether they could be measured in a thinning scenario is questionable.
Methods
Continuous-logging soil moisture sensors were installed in 4 Meadow Valley units, essentially repeating 4 of 5
units (and same approximate locations) which were pre-activity sampled by Wayne Johannsen in 2001 but not
post-sampled. It was desired to monitor 4 sites concurrently, with treated and untreated paired comparisons,
requiring 8 dataloggers and 32 sensors. When moved to the Franc Sale, measurements were expanded to 5 unit
pairs. Decagon™ brand equipment was chosen for overall affordability and utility; use of this equipment does
not imply any recommendation relative to similar equipment from other competitive sources.
Sensors are high frequency dialectric models 10HS & EC-TM/TE, the latter collecting additional temperature
data. The 10HS sensors “sense” a larger soil volume (approx. 1 liter), and were installed at the 10 and 30 inch
depth increments. The EC-TM/TE sensors have an approximate 0.3 liter volume of influence and were installed
at 20 and 40 inch depth increments. Both models output raw dialectric voltage readings and calculated
volumetric water content (VWC), estimated using standard mineral soil calibration equations developed by the
vendor. Specified sensor accuracy is +/- 3% VWC in cm3/cm3. The effort was not made to develop soil-specific
HFQLG Soil Moisture Monitoring Report – Meadow Valley and Franc
Page 2
custom calibration equations because of the several soils and soil profile horizons involved, and it would
apparently only improve the specified accuracy to +/- 2% VWC. The EM50 dataloggers have a capacity of 5
sensors, can operate for about 1 year with (5) AA batteries, utilize “stereo” serial ports for communication, and
were set to record data hourly. The loggers are intended to be installed aboveground, having a weather
resistant enclosure, but breathable to prevent moisture buildup.
Installation was done by David Young and Colin Dillingham. Soil pits were excavated to 40+ inches depth, and
sensors were installed roughly horizontal (actually at a slight sideways and downward angle to keep water from
ponding on the impervious sensor surface). At Meadow Valley, sensors were inserted into the “undisturbed” pit
face, and staggered left-right at alternating depths to avoid sensor interference. Extremely rocky soils at Franc
precluded insertion in “intact” soil, so sensors were carefully placed in “pockets” of sieved soil from the
appropriate depth, and also staggered left-right to the extent that large rocks could be avoided. The datalogger
was fastened to a small post right next to the pit, and connections and testing completed before carefully
backfilling the soil pit, attempting to restore the original soil density and source depth of the soil material.
Loggers were downloaded occasionally, and batteries replaced going into each winter.
Installation locations were carefully chosen to be as closely matched as possible except for stand density
representing the treated and untreated (control) conditions. Precise location pairing attempted to match slope
position, aspect, soils, microsite topography, and pre-thinning stand density. Respective of the greater
watershed, at Meadow Valley 1 site was at the toe-slope near a meadow fringe, 2 were mid-slope, and 1 was
near the ridge; at Franc 2 sites were lower slope position, 2 mid-slope, and 1 upper-slope. GPS location, as well
as site and stand characteristics (basal area, crown cover, understory cover) were recorded for each installation
point. Weather data (precipitation, air temperature) was obtained from the California Climate Data Archive
website (http://www.calclim.dri.edu/ccda/data.html), using Quincy RAWS to represent Meadow Valley and Dog
Valley RAWS to represent Franc , being the nearest stations with complete data for the time periods of interest.
Statistical analyses were performed by Jianwei Zhang. Analysis was focused upon the above monitoring
question, i.e. the statistical difference attributable to treatment, with date, unit pairs, and soil depth as
replication variables. Since date could be further used as a trend variable, a mixed-model repeated-measures
ANOVA was used in SAS™ software to amalgamate the data set, as well as account for missing data due to a few
intermittent sensors. The two sites were analyzed separately. Many more detailed analyses could be
performed comparing climate, soil temperature, and soil moisture trends by individual installation (unit pair) or
soil depth increment, and/or incorporate stand data variables; this would be desirable as a future pursuit.
However, this report is mostly limited to the primary monitoring question regarding the overall effect of
treatments on soil moisture status.
A note on statistics vs. engineering/technical properties of soil sensors: The difference between treated and
untreated unit pairs is the primary metric of interest for analysis. The technical accuracy of the deployed soil
sensors is +/- 3% VWC (absolute) and +/- 1⁰C for temperature. When analyzing pairs by differential water
content, it is therefore possible to have a maximum of 6% difference due to error in sensor accuracy alone, in
the event one paired sensor is 3% off in a positive direction and the other is 3% off in the negative direction (not
probable, but possible); likewise we could have a maximum of 2⁰C difference from sensor accuracy error.
Therefore differential water contents of < 6% VWC and < 2⁰C are dubious as being within the sensor error range,
and may not be “real” differences, even if statistically significant. To trust the statistics within that differential
error range, one must be willing to assume that sensors should in general err in the same direction, considering
HFQLG Soil Moisture Monitoring Report – Meadow Valley and Franc
Page 3
that the error in absolute numbers should be due more to soil type relative to calibration equations rather than
actual sensor output accuracy. Whether or not this assumption is accepted is relevant in concluding that
statistically significant differences are valid where absolute differences are small.
Results and Discussion
Climate Data
Climate data representing the two sites (figures 1 and 2) exhibits cold wet winters and warm dry summers
typical of California’s Mediterranean climatic zone. The Franc site, being very near the crest of the Sierra range,
shows more summer precipitation, associated with spotty summer thunderstorms typical of the area.
Precipitation events are reflected quite well in soil moisture status, with small events only showing up in the
surface layer and large events showing up as moisture spikes in all depths. No effort was made to statistically
discern precise relationships (e.g. how large an event is required to show up at various depths?). The climate
data was generally used to qualitatively error-check spikes and dips in soil temperature and moisture data, and
to differentiate the growing season from the non-growing season for statistical analysis, based upon consecutive
freezing days (a 10 day period without freezing temperatures denoted the start of the growing season). At
Meadow Valley the growing season for analysis was 6/1/10 to 10/31/10; the non-growing season followed from
11/1/10 to 5/30/11. At Franc the growing season was 6/1/12 to 9/8/12 (the last download date); the nongrowing season preceded the growing season, from 10/1/11 to 5/31/12.
Soil Temperature
Soil temperature data was only collected at 20 and 40 inch depth increments. The 20 inch depth is
conventionally used to determine the soil temperature regime used at various categorical levels in USDA soil
taxonomy. Soil temperature data was desired so that it might help explain possible differences in soil moisture.
At Meadow Valley (figure 3) seasonal trends are apparent, with thinned stands having higher summer soil temps
(particularly at 20 in depth) and cooler winter temps (particularly at 40 in depth). The two depths were
significantly different for both growing and non-growing seasons (P < 0.0001). Temperatures were only
significantly different for the growing season (P < 0.0001, versus P = 0.7677 for the non-growing season), with
thinned stands having higher soil temps than unthinned stands.
At Franc (figure 4) precisely the same seasonal trends are apparent, with thinned stands having higher summer
soil temps (particularly at 20 in depth) and cooler winter temps (particularly at 40 in depth). Again, depths were
significantly different for both growing and non-growing seasons (P < 0.0001) and temperatures were only
significantly different for the growing season (P < 0.0001), although the non-growing season was much closer to
being significant (P = 0.0833).
The data concludes that soil temperatures are significantly [statistically] warmer in thinned stands during the
summer growing season. The difference in absolute terms is less than 2⁰C (1.2⁰ at Meadow Valley, 1.9⁰ at
Franc). This is notably within the technical accuracy/error range for the sensors used, so whether these
differences are “real” is questionable, but probable. In ecological terms, a real difference of 2⁰C could be
significant in accelerating soil chemical and biological processes.
HFQLG Soil Moisture Monitoring Report – Meadow Valley and Franc
Page 4
Quincy, California
40
50
2009
30
20
30
10
20
0
10
-10
0
-20
-10
40
50
2010
30
40
20
30
10
20
0
10
-10
0
-20
-10
40
50
Precipitation (mm)
o
Daily air temperature ( C)
40
Tmax
Tmin
Precip
2011
30
40
20
30
10
20
0
10
-10
0
-20
-10
0
50
100
150
200
250
300
350
Julian date
Figure 1. Meadow Valley site – Quincy RAWS air temperature (min and max) and precipitation data for the
entire soil moisture monitoring period.
HFQLG Soil Moisture Monitoring Report – Meadow Valley and Franc
Page 5
o
40
Tmax
Tmin
precip
20
30
10
20
0
10
-10
0
-20
-10
50
2012
30
40
Col 3 vs Col 9
Col 3 vs Col 10
Col 7
20
30
10
20
0
10
-10
0
-20
-10
0
Precipitation (mm)
2011
30
40
Daily air temperature ( C)
50
50
100
150
200
250
300
Precipitation (mm)
o
Daily air temperature ( C)
40
350
Julian date
Figure 2. Franc site – Dog Valley RAWS air temperature (min and max) and precipitation data for the entire
soil moisture monitoring period.
HFQLG Soil Moisture Monitoring Report – Meadow Valley and Franc
Page 6
16
Unthinned_20in
14
Thinned_20in
Temperature (Celsius)
12
10
8
6
4
2
0
1-Sep-09
1-Nov-09
1-Jan-10
1-Mar-10
1-May-10
1-Jul-10
1-Sep-10
1-Nov-10
1-Jan-11
1-Mar-11
1-May-11
1-Jul-11
1-Sep-11
1-Jul-11
1-Sep-11
16
Unthinned_40in
14
Thinned_40in
Temperature (Celsius)
12
10
8
6
4
2
0
1-Sep-09
1-Nov-09
1-Jan-10
1-Mar-10
1-May-10
1-Jul-10
1-Sep-10
1-Nov-10
1-Jan-11
1-Mar-11
1-May-11
3
Temperature (Celsius)
DIFF_20in
DIFF_40in
2
1
treated is warmer
0
treated is cooler
-1
-2
-3
1-Sep-09
1-Nov-09
1-Jan-10
1-Mar-10
1-May-10
1-Jul-10
1-Sep-10
1-Nov-10
1-Jan-11
1-Mar-11
1-May-11
1-Jul-11
1-Sep-11
Figure 3. Meadow Valley site – soil temperature trends. Daily average temperatures in Celsius at two soil
depths, and temperature differential by depth.
HFQLG Soil Moisture Monitoring Report – Meadow Valley and Franc
Page 7
16
Unthinned_20in
14
Thinned_20in
Temperature (Celsius)
12
10
8
6
4
2
0
15-Sep-11
15-Oct-11
15-Nov-11 15-Dec-11
15-Jan-12
15-Feb-12 15-Mar-12
15-Apr-12 15-May-12
15-Jun-12
15-Jul-12
15-Aug-12
15-Jun-12
15-Jul-12
15-Aug-12
14
Unthinned_40in
12
Temperature (Celsius)
Thinned_40in
10
8
6
4
2
0
15-Sep-11
15-Oct-11
15-Nov-11 15-Dec-11
15-Jan-12
15-Feb-12 15-Mar-12
15-Apr-12 15-May-12
3
Temperature (Celsius)
DIFF_20in
DIFF_40in
2
1
treated is warmer
0
treated is cooler
-1
-2
-3
15-Sep-11
15-Oct-11
15-Nov-11 15-Dec-11
15-Jan-12
15-Feb-12 15-Mar-12
15-Apr-12 15-May-12
15-Jun-12
15-Jul-12
15-Aug-12
Figure 4. Franc site – soil temperature trends. Daily average temperatures in Celsius at two soil depths, and
temperature differential by depth.
HFQLG Soil Moisture Monitoring Report – Meadow Valley and Franc
Page 8
Soil Moisture
Overall soil moisture trends by site, treatment, and depth are displayed in figures 5 and 6. At both sites, rain
events are apparent in rapid spikes in soil moisture, which can be traced back to the climate graphs. The
consistent drawdown of soil moisture during the summer growing season is also apparent.
Realities of intermittent sensor data are also apparent – note Meadow Valley, unthinned, 40 inches depth. Each
line is an average of several unit-pairs; when individual sensors stop recording data (due to being frozen, cable
connection comes loose, misc. errors, etc.) the number of pairs composing the average changes, so the average
may abruptly change also, which creates some analytical challenges. In running statistics the data that is
“paired” to the missing data must be disregarded to avoid imbalanced comparisons (comparing two averages
that have different number of reps). There are several instances of this in the data set at large. There are also
several miscellaneous instances of obviously erroneous data, for no explicable reason (e.g. soil moisture
declining radically for just a few hours, while otherwise quite stable for days). This kind of instance is attributed
to sensor error, such as an incorrect voltage output or reading by the logger. Effort was made to clean up large
errors (by interpolating or deleting) that might have a disproportionate effect on means, leading to magnified
differences. Smaller errors were not sought out and cleaned up, assuming the data set is large enough to
compensate for small-magnitude errors.
Considering how water is normally distributed in the soil profiles, it is quite apparent at Meadow Valley that the
sensors at 20 and 40 inches depth inherently report a higher VWC. This must be due to the applicability of the
calibration equation to the particular soils at that site, and/or the different volumes of influence for the different
sensors (i.e. rock content would be more likely to affect values for the sensors with larger volume of influence).
These data could be normalized for more robust analysis and direct comparison of all depths, but were not for
this reporting. These differences are not apparent at Franc, except perhaps in March and April when soils are at
peak-high water contents from snowmelt. The soils at Franc are notably more homogeneous in texture with
depth (sandy loams throughout the profile, vs. loams over clay loams at Meadow Valley), and the volumes of
influence were further homogenized by sieving out rock and constructing measurement pockets large enough
for the sensor type.
At Meadow Valley, overall soil moisture differences are -3.9%, meaning treated stands are drier on average.
Differences ranged from -1.0% to -6.7% at various depths. At Franc, overall soil moisture differences are +1.3%,
meaning treated stands are more moist on average. Differences ranged from -0.8% to +2.9% at various depths.
At both sites and in both seasons, differences between depth increments and treatments are highly significant
(P < 0.0001), although trends were not consistent between sites and absolute differences are relatively small.
Growing seasons were broken out to look more closely at differences when tree stands are or are not directly
affecting soil moisture via growth demands.
At Meadow Valley (figures 7 and 8), differences between soil depths and treatments are highly significant in
both seasons (P < 0.0001). Combining depths for a “soil profile” average, thinned stands have 5.1% lesser soil
moisture in the growing season and 3.6% lesser in the non-growing season. Differences are greatest at 30 & 40
inch depths during the growing season, which is the opposite of what might be expected IF soil temperature
differences were a driving factor. Differences are greatest at 20 & 30 inch depths during the non-growing
season, which doesn’t make much sense in terms of soil physics.
HFQLG Soil Moisture Monitoring Report – Meadow Valley and Franc
Page 9
At Franc (figures 9 and 10), differences between soil depths and treatments are again highly significant in both
seasons (P < 0.0001). Combining depths for a “soil profile” average, thinned stands have 1.5% higher soil
moisture in the growing season and 1.4% higher in the non-growing season. During the growing season,
differences are most consistent at the 10 inch depth, negligible at the 30 inch depth, and 20 & 40 inch depths
alternate from wetter to drier throughout the season. During the non-growing season, differences are greater
at 10 & 20 inch depths, and soils are actually slightly drier at 30 & 40 inch depths during most of the season.
In summary, soil moisture differences between thinned and unthinned stands are statistically significant at both
sites, but one site is drier and one is moister on average for the whole soil profile. Meadow Valley has the drier
soils, and this site has gone a longer time between treatments and monitoring. It is presumed that these
thinned stands have had more time to expand crown and root systems post-thinning and fully take advantage of
site resources. Increased net transpiration rates in these stands may be responsible for the drier soils.
Conversely, the Franc site has the moister soils, and the site has gone only 1 season since treatments.
Presumably this site has not had adequate time for residual trees to take full advantage of site resources, so
fewer evapotranspiration ‘pumps’ are leaving soils more moist. This net transpiration explanation seems
reasonable, but it is strictly speculative without research level monitoring of many possible causal factors.
Conclusions
There are very-statistically-significant differences in soil moisture and temperature between treated and
untreated stands. The absolute magnitude of differences is relatively small, and differences are inconsistent
among sites, soil depths, and individual unit-pairs, so the ecological significance of these differences is unknown.
The overall HFQLG monitoring question has been investigated, and overall results for the two monitored sites
are statistically clear, albeit different. The different results may be a result of different times since treatment,
fine-scale differences in climates (e.g. solar radiation), differences in soil types at the two sites, or a combination
of these and other factors. It was not the purpose of this operational monitoring to determine cause (or effects)
of differences in moisture, but simply to document status and trend as a function of vegetation management
treatments. Longer temporal trends are likely necessary to better interpret findings.
There are several curious differences and trends in the finer details of the data that are interesting and difficult
to explain. It is desired to further analyze this data set, parsing out individual unit-pairs and soil depths and
factoring in stand data metrics to investigate these trends more closely. It may also be desirable to leave the
sensors in place at Franc and continue monitoring for several years to look at longer temporal trends. Barring
Congressional renewal of the HFQLG program, and therefore a desire to relocate the monitoring equipment, it is
the authors’ intent to continue actively monitoring the Franc site for several years to come.
HFQLG Soil Moisture Monitoring Report – Meadow Valley and Franc
Page 10
Volumetric Water Content (cm3/cm3)
0.70
0.60
UNTHINNED
0.50
VWC_10
VWC_20
VWC_30
VWC_40
0.40
0.30
0.20
0.10
1-Sep-09
1-Nov-09
1-Jan-10
1-Mar-10
1-May-10
1-Jul-10
1-Sep-10
1-Nov-10
1-Jan-11
1-Mar-11
1-May-11
1-Jul-11
1-Sep-11
Volumetric Water Content (cm3/cm3)
0.70
0.60
THINNED
0.50
VWC_10
VWC_20
VWC_30
VWC_40
0.40
0.30
0.20
0.10
1-Sep-09
1-Nov-09
1-Jan-10
1-Mar-10
1-May-10
1-Jul-10
1-Sep-10
1-Nov-10
1-Jan-11
1-Mar-11
1-May-11
1-Jul-11
1-Sep-11
Figure 5. Overall soil moisture trends at Meadow Valley site by Treatment and Soil Depth (averages of 4 unit
pairs). Differences (not shown) range from -1.0% to -6.7%, with absolute differences ranked by depth as
10<40<20<30.
Volumetric Water Content (cm3/cm3)
0.60
UNTHINNED
0.50
VWC_10
VWC_20
VWC_30
VWC_40
0.40
0.30
0.20
0.10
15-Sep-11
15-Nov-11
15-Jan-12
15-Mar-12
15-May-12
15-Jul-12
15-Sep-12
Volumetric Water Content (cm3/cm3)
0.60
THINNED
0.50
VWC_10
VWC_20
VWC_30
VWC_40
0.40
0.30
0.20
0.10
15-Sep-11
15-Nov-11
15-Jan-12
15-Mar-12
15-May-12
15-Jul-12
15-Sep-12
Figure 6. Overall soil moisture trends at Franc by Treatment and Soil Depth (averages of 5 unit pairs).
Differences (not shown) range from -0.8% to +2.9%, with absolute differences ranked by depth as
40<30<20<10.
HFQLG Soil Moisture Monitoring Report – Meadow Valley and Franc
Page 11
Volumetric Water Content (cm3/cm3)
0.60
UNTHINNED
0.55
0.50
0.45
0.40
VWC_10
0.35
VWC_20
0.30
VWC_30
0.25
VWC_40
0.20
0.15
0.10
1-Jun-10
15-Jun-10
29-Jun-10
13-Jul-10
27-Jul-10
10-Aug-10
24-Aug-10
7-Sep-10
21-Sep-10
5-Oct-10
19-Oct-10
Volumetric Water Content (cm3/cm3)
0.60
THINNED
0.55
0.50
0.45
0.40
VWC_10
0.35
VWC_20
0.30
VWC_30
0.25
VWC_40
0.20
0.15
0.10
1-Jun-10
15-Jun-10
29-Jun-10
13-Jul-10
27-Jul-10
10-Aug-10
24-Aug-10
7-Sep-10
21-Sep-10
5-Oct-10
19-Oct-10
VWC (cm3/cm3)
0.20
DIFF_10
0.15
DIFF_20
DIFF_30
DIFF_40
Treated is
Wetter
0.10
0.05
0.00
-0.05
-0.10
Treated is
Drier
-0.15
-0.20
1-Jun-10
15-Jun-10
29-Jun-10
13-Jul-10
VWC (cm3/cm3)
0.12
27-Jul-10
10-Aug-10
24-Aug-10
7-Sep-10
21-Sep-10
5-Oct-10
19-Oct-10
DIFFERENTIAL - ALL DEPTHS COMBINED
0.09
Treated is
Wetter
0.06
0.03
0.00
-0.03
-0.06
Treated is
Drier
-0.09
-0.12
1-Jun-10
15-Jun-10
29-Jun-10
13-Jul-10
27-Jul-10
10-Aug-10
24-Aug-10
7-Sep-10
21-Sep-10
5-Oct-10
19-Oct-10
Figure 7. Meadow Valley Growing-Season soil moisture trends. Treatments and depths are significantly
different (P < 0.0001). Differences are greatest at 30 & 40 inch depths (-8.6% and -7.1% respectively).
Averaging the whole soil profile, thinning stands have 5.1% lower soil moisture.
HFQLG Soil Moisture Monitoring Report – Meadow Valley and Franc
Page 12
Volumetric Water Content (cm3/cm3)
0.60
UNTHINNED
0.55
0.50
0.45
0.40
VWC_10
0.35
VWC_20
0.30
VWC_30
0.25
VWC_40
0.20
0.15
0.10
1-Nov-10
1-Dec-10
1-Jan-11
1-Feb-11
1-Mar-11
1-Apr-11
1-May-11
Volumetric Water Content (cm3/cm3)
0.60
THINNED
0.55
0.50
0.45
0.40
VWC_10
0.35
VWC_20
0.30
VWC_30
0.25
VWC_40
0.20
0.15
0.10
1-Nov-10
1-Dec-10
1-Jan-11
1-Feb-11
1-Mar-11
1-Apr-11
1-May-11
VWC (cm3/cm3)
0.20
DIFF_10
0.15
DIFF_20
DIFF_30
DIFF_40
Treated is
Wetter
0.10
0.05
0.00
-0.05
-0.10
Treated is
Drier
-0.15
-0.20
1-Nov-10
1-Dec-10
1-Jan-11
VWC (cm3/cm3)
0.12
1-Feb-11
1-Mar-11
1-Apr-11
1-May-11
DIFFERENTIAL - ALL DEPTHS COMBINED
0.09
Treated is
Wetter
0.06
0.03
0.00
-0.03
-0.06
Treated is
Drier
-0.09
-0.12
1-Nov-10
1-Dec-10
1-Jan-11
1-Feb-11
1-Mar-11
1-Apr-11
1-May-11
Figure 8. Meadow Valley Non-Growing-Season soil moisture trends. Treatments and depths are significantly
different (P < 0.0001). Differences are greater at 20 & 30 inch depths (-7.4% and -7.1% respectively).
Averaging the whole soil profile, thinning stands have 3.6% lower soil moisture.
HFQLG Soil Moisture Monitoring Report – Meadow Valley and Franc
Page 13
Volumetric Water Content (cm3/cm3)
0.60
UNTHINNED
0.55
0.50
0.45
0.40
VWC_10
0.35
VWC_20
0.30
VWC_30
0.25
VWC_40
0.20
0.15
0.10
1-Jun-12
15-Jun-12
29-Jun-12
13-Jul-12
27-Jul-12
10-Aug-12
24-Aug-12
7-Sep-12
Volumetric Water Content (cm3/cm3)
0.60
THINNED
0.55
0.50
0.45
0.40
VWC_10
0.35
VWC_20
0.30
VWC_30
0.25
VWC_40
0.20
0.15
0.10
1-Jun-12
15-Jun-12
29-Jun-12
13-Jul-12
27-Jul-12
10-Aug-12
24-Aug-12
7-Sep-12
VWC (cm3/cm3)
0.20
DIFF_10
0.15
DIFF_20
DIFF_30
DIFF_40
Treated is
Wetter
0.10
0.05
0.00
-0.05
-0.10
Treated is
Drier
-0.15
-0.20
1-Jun-12
15-Jun-12
29-Jun-12
VWC (cm3/cm3)
0.12
13-Jul-12
27-Jul-12
10-Aug-12
24-Aug-12
7-Sep-12
DIFFERENTIAL - ALL DEPTHS COMBINED
0.09
Treated is
Wetter
0.06
0.03
0.00
-0.03
-0.06
Treated is
Drier
-0.09
-0.12
1-Jun-12
15-Jun-12
29-Jun-12
13-Jul-12
27-Jul-12
10-Aug-12
24-Aug-12
7-Sep-12
Figure 9. Franc Growing-Season soil moisture trends. Treatments and depths are significantly different (P <
0.0001). Differences are consistent at 10 inches depth (+4.1%). Averaging the whole soil profile, thinning
stands have 1.5% higher soil moisture.
HFQLG Soil Moisture Monitoring Report – Meadow Valley and Franc
Page 14
Volumetric Water Content (cm3/cm3)
0.60
UNTHINNED
0.55
0.50
0.45
0.40
VWC_10
0.35
VWC_20
0.30
VWC_30
0.25
VWC_40
0.20
0.15
0.10
1-Oct-11
1-Nov-11
1-Dec-11
1-Jan-12
1-Feb-12
1-Mar-12
1-Apr-12
1-May-12
Volumetric Water Content (cm3/cm3)
0.60
THINNED
0.55
0.50
0.45
0.40
VWC_10
0.35
VWC_20
0.30
VWC_30
0.25
VWC_40
0.20
0.15
0.10
1-Oct-11
1-Nov-11
1-Dec-11
1-Jan-12
1-Feb-12
1-Mar-12
1-Apr-12
1-May-12
VWC (cm3/cm3)
0.20
DIFF_10
0.15
DIFF_20
DIFF_30
DIFF_40
Treated is
Wetter
0.10
0.05
0.00
-0.05
-0.10
Treated is
Drier
-0.15
-0.20
1-Oct-11
1-Nov-11
1-Dec-11
VWC (cm3/cm3)
0.12
1-Jan-12
1-Feb-12
1-Mar-12
1-Apr-12
1-May-12
DIFFERENTIAL - ALL DEPTHS COMBINED
0.09
Treated is
Wetter
0.06
0.03
0.00
-0.03
-0.06
Treated is
Drier
-0.09
-0.12
1-Oct-11
1-Nov-11
1-Dec-11
1-Jan-12
1-Feb-12
1-Mar-12
1-Apr-12
1-May-12
Figure 10. Franc Non-Growing-Season soil moisture trends. Treatments and depths are significantly different
(P < 0.0001). Differences are greater at 10 & 20 inch depths (+2.6% and +4.0% respectively). Averaging the
whole soil profile, thinning stands have 1.4% higher soil moisture.
HFQLG Soil Moisture Monitoring Report – Meadow Valley and Franc
Page 15