DWM Sampling Protocol Clarifications

**Contribution of dead shrubs to Fuelbed Depth:** The field manual
states that the fuelbed measurement includes, "the accumulated mass of
dead, woody material on the surface of the forest floor...begins at the
top of the duff layer, and includes litter, FWD, CWD, and dead woody
shrubs." The question arises as to whether dead shrubs in this measure
have to be down dead or can be standing dead? Since other aspects of the
DWM sampling protocol measure both down and standing dead shrubs, there
is no clarification in the manual. During discussions with all regional
lead trainers, it was determined that dead shrubs in the fuelbed depth
variable could be standing (attached to roots) or down (unattached to
roots).

**Effect of slope on angle of intercept of CWD Pieces:** The lean angle
of CWD pieces is determined from the vertical angle, not angle with
slope. The DWM sample protocol does not provide for the measurement of
the actual angle that a CWD piece lies from vertical, since most CWD
pieces lie on the ground it can be assumed that most pieces lie greater
than 80 degrees from vertical (also known as piece inclination). When
CWD pieces are propped up or still attached they must lean greater than
45 degrees from vertical.

**Fractured CWD:** The field manual states that if "a piece is fractured
across its diameter or length, and would pull apart at the fracture if
pulled from either end or sides, treat it as two separate pieces." So if
field crews determine that a CWD piece would separate if pulled either
at opposite ends or sides, then the CWD piece is deemed fractured into
at least 2 pieces. Once again only tally the CWD pieces that are
intersected by sampling transects. Although one slide in the 3^rd^
presentation of the training series (both years 2003 and 2004) indicates
something about touching pieces for fractured logs, please ignore older
versions since it has been subsequently corrected.

**Covered/Buried CWD Pieces:** According to the DWM field manual, entire
pieces or sections of CWD that are buried in soil are not included in
measurements. Therefore, if an end of a CWD piece is buried in a muddy
bank, the measurements would end at the point at which the CWD piece
becomes buried, thus negating the need for field personnel to dig
through soil. For the purpose of clarification, soil will be considered
duff and subsequent organic and mineral soil horizons. If a CWD piece is
buried such that the minimum requirements (3 inches diameter for at
least 3 feet) are met aboveground for the CWD piece, field crews will be
required to measure the attributes of the CWD occurring above-ground
(where they can acquire measurements). If thick moss, sphagnum, or
litter covers logs, this will not count as being buried since they are
not part of the defined soil horizons.

**Coverage Obstructions in Microplots:** Only use the area that could be
occupied by exposed soil within the microplot as the area within which
cover is estimated. For example, if an area has 20% cover of boulders
and stumps while the rest of the microplot is completely covered by
litter, the estimate of litter cover would be 100%. In other words, 100%
of the area that could be covered by litter is indeed covered by litter.
The same applies for estimates of both live and dead shrubs/herbs on the
microplot.

Clarification of Microplot Coverage Estimation

**Field Manual 14.7.x**

Field manual procedures require an estimation of the coverage of various
fuel categories (live shrub, dead shrub, live herb, dead herb, and
litter) for each microplot. For each fuel component the field manual
simply states that "percent cover of fuel components on microplot"
should be measured in 10% cover classes.

*How should cover estimates be determined for microplots with non-forest
conditions?*

Use only the area of the microplot in accessible forested conditions to
estimate the coverage of any fuel component. So no matter how much of a
microplot is in a non-forested condition, only use the forested
condition classes to estimate coverage. If only 5 sq. ft. of a microplot
is in an accessible forested condition and has 100% litter cover, then
litter cover should be recorded as 100%.

Pictorial Example:

![](media/image1.jpeg){width="3.0in" height="4.533333333333333in"}

Clarification of DUFF_DEPTH Measurement for Training Purposes

Although in 2004 the DWM field manual was updated to include more
information of duff sampling techniques, the full description of
training DUFF_DEPTH is below.

As defined, duff_depth is the depth in tenths of inches of the duff
layer. The duff layer is the organic material layer between the
A-horizon (or uppermost soil mineral horizon) and the litter layer. The
duff layer is decomposing organic material, decomposed to the point at
which there is no identifiable organic materials (pine straw, leaves,
twigs, etc).

We anticipate that measuring the duff depth will pose no unusual
problems in most situations and states. However, there are some
locations where the duff layer is extremely deep, due to buildup of
large amounts of sphagnum moss and other material. Problems arise when
crews encounter deep, organic soils and/or soils where differentiation
between mineral soils horizon, duff layer, and litter layer is
difficult. We don\'t want crews expending massive amounts of time
digging through 4 ft of organic matter trying to reach the end of a very
deep duff layer, or what they perceive as the end of the duff layer. If
the duff layer is in fact very deep (more than 8 inches, matches the
duff depth in soil sampling at which estimation is allowed)) then crews
are allowed to estimate the full depth of this layer. To start with,
crews should dig down as deep as possible and measure this depth. If
they determine that duff continues beyond this point they can estimate
the remaining portion as follows:

Examine the subplot area and the area immediately around the sample
point. If there is a cutbank or a windthrown tree nearby where the soil
layers are exposed, obtain an estimate of the duff layer from this
disturbed area. Compare that estimate with the measured depth already
taken and estimate a value for the entire duff depth. The QA staff will
have to be lenient when evaluating the tolerance and MQO's.

In some situations, where its difficult to distinguish the duff, litter,
and organic soil layers, crews will need to acquire a sense of duff
density and texture. Not only is duff different from litter in that
litter contains recognizable dead plant parts, but it is much denser. A
handful of litter is much lighter than a handful of duff. In fact, when
processing duff and litter layer measurements, duff can easily weigh 6X
more than litter per cubic foot. Slight error in measuring duff, through
inclusion of litter, will be compounded when per acre tonnage estimates
are created. When differentiating between duff and the uppermost mineral
horizon, your eyes and soil texture should serve as good guides. If
unsure of the bottom of the duff layer, crews should feel the texture of
the suspect soil in their hand. Crews may eliminate needless sampling of
duff depths and reduce measurement error by making sure the soil from
the bottom of the duff layer is organic and not a mineral horizon. Crews
should be trained to avoid sampling A horizons which have some organic
material in it. Rhetorical questions to ask are: is this duff layer
dried out, would it burn? If someone wanted to calculate the total
amount of carbon in this duff layer, would they find organic matter or
mineral soil along the full measured depth at the sample point?

Examples:

A light litter layer with deep, organic soils \--\> make sure the litter
is scraped away revealing a soil horizon with no identifiable plant
parts, use hands to keep feeling soil texture down the soil profile till
the soil texture changes from that of a smooth organic feel till the
texture changes to a more gritty, mineral feel\... this is the bottom of
the duff layer.

Additional info (information from soil sampling may aid in Duff
identification:

## Soil Indicator Tips for Telling the Difference between Mineral and Organic Soil Horizons

> In some soils, telling the difference between the bottom of the
> O-Horizon and the top of an A-horizon (organic-rich mineral horizon)
> can be difficult. If uncertain:

-   Look for evidence of plant parts (e.g., leaves, needles). If you can
    see them decomposing in place, you're still in organic.

-   Rub the soil between your finger. Does it crumble (organic) or feel
    more like modeling clay (try pinching into a ribbon).

-   Look for shiny flecks of mica or quartz (won't help in all soils).

-   Look for a subtle change in color. Organic horizons tend to be
    black; an A-horizon may be more brownish.

-   Wet a sample of the material and press it between your fingers. Note
    the color of the liquid that runs out. The blacker the color, the
    higher the organic content.

-   Check for a change in density (mineral soils are denser).

Definitions used in Soils Manual

Duff (Humus) A soil layer dominated by organic material derived from the
decomposition of plant and animal litter and deposited on either an
organic or a mineral surface. This layer is distinguished from the
litter layer in that the original organic material has undergone
sufficient decomposition that the source of this material (e.g.,
individual plant parts) can no longer be identified.

Litter Undecomposed or only partially decomposed organic material that
can be readily identified (e.g., plant leaves, twigs, etc.)

QA/QC Important Issues

Probably the most important DWM estimate requested by FIA customers is
that of tons/acre by DWM component. A simple mistake in the decimal
place of one DWM variable can cause DWM tonnage estimates to be expanded
by 10x or more. If a FIA customer receives one incorrect plot estimate
(i.e., 500 tons per acre of CWD), they will doubt all FIA DWM data.
Although we cannot have zero tolerance of errors because we are human
beings working long days in the weeds and woods, one measurement error
by one crew member can decrease the perceived value of the data by users
and hence reduce the value of all the hard work by all field crews. What
can you do? The following three DWM variables are most likely to suffer
measurement/data entry errors resulting in large estimate discrepancies.

1.  CWD Diameters: The small, large, and transect diameter of CWD pieces
    is measured in inches to the [nearest inch]{.underline}. Because
    field crews enter the diameters of phase 2 trees to the nearest
    tenth of inch, crews can have mental lapses and accidentally enter
    diameters for any CWD piece to the tenth of an inch. They can also
    have keystroke errors. Thus, a 5-inch CWD piece becomes a 50-inch
    CWD piece.

2.  Mismatching data. For instance, crews indicated a condition number 2
    along one for the transects although P2 data indicates there is only
    one condition on the plot.

3.  Duff Depths: A few inches of duff covering an entire acre can weigh
    dozens of tons. Therefore, a duff measurement error can result in a
    substantial error in a total tonnage estimate for a plot. Simple
    keystroke errors can lead to field crews entering a duff depth of 10
    inches instead of 1.0 inches.

4.  Slash Pile Density: The density of slash piles usually runs between
    10-40%. A neatly organized wood pile might approach 70%. It is
    almost geometrically impossible for slash piles to approach 80-90%
    densities for roughly assembled piles. Although the PDR will accept
    values approaching 99%, crews must be vigilante and understand the
    implications of their density estimates.