Appalachia--Science in the Public Interest

THE PRACTICE OF ECOFORESTRY: INVENTORY AND DESCRIPTION
Part 1 of 3

Paul Kalisz, Ph.D.

1. Introduction.

Healthy ecosystems (the totality of living and non-living things, and
the forces and processes that operate among them) are the foundations of
healthy and sustainable human communities. The three-part series THE
PRACTICE OF ECOFORESTRY is intended to provide technical direction to
individuals who believe that it is both biologically and morally imperative
that we restore and protect the health of native ecosystems. This implies
that ecological restoration and protection are the transcendent goals of
forestry, and that production and harvest of forest produce for human use
are subordinate goals. Forest management founded on these principles may be
called þecoforestry.þ This series of papers may also serve as a primer on
forestry and an introduction to forestry jargon. Key terms and concepts are
presented in bold-face.

2. Maps

Your forest land should be delineated on a map that is at least as
detailed as the standard 1:24,000 topographic quadrangle maps produced by
the U.S. Geological Survey (USGS) and sold locally (check under þmapsþ in
the Yellow Pages of your phone book) for $3 to $5. Ask the map distributor
to see the index map for your state. This will enable you to determine the
name of the USGS topographic quadrangle that includes your land. To obtain
a useful scale it is usually necessary to enlarge portions of the map with
a photocopy machine. Note that the scale of the map will change on
enlargement. For example, where 1 inch represents 2,000 feet on a
standard USGS quadrangle, it will represent 1,000 feet if the map size is
doubled (i.e. enlarged 100%).

Once you have located your land on a topographic map and the map scale
is enlarged, you should divide your land into management units. Management
units are normally based on differences in bedrock, land-use history, and
topography and are drawn to delineate land areas that are internally
uniform. For example, management units may be based on whether the land is
underlain by sandstone, limestone or shale bedrock, or on whether the land
has ever been cultivated. In mountainous areas, useful management units may
also be formed by classifying land as þflatþ (if average slope steepness is
less than 20%, i.e. rise <20 feet per 100 feet horizontal distance) or as
þslopingþ; as facing north (if most slopes face to the north side of a
line running from northwest to southeast) or as facing south; and as
occurring on ridges, stream bottoms, noses, side-slopes or coves (Fig. 1).

Ecosystem characteristics within a management unit are usually
sufficiently uniform to consider the trees a stand (a group of trees
occupying an area of land and treated as a single unit) in terms of
management.

Figure 1. Portion of a USGS topographic map showing an 80-acre forest
divided into six management units: 1=ridge; 2=cove; 3=south side slope;
4=north side slope; 5=nose; 6=stream bottom. Dots represent locations for
60 inventory plots.

Next, the acreage in each management unit should be estimated and the
approximate number and spacing of inventory plots should be determined
from Table 1. Inventory plot centers may be marked on the map using the
spacing guidelines in Table 1 and the scale provided on the map (e.g. 1
inch equals 2,000 feet for a standard USGS map) or plots may simply be
located in the field without marking them on the map. To do the latter,
begin at an identifiable land mark and randomly locate the first plot
center, then locate the other plot centers in a square grid pattern of the
appropriate spacing (Fig. 1; Table 1) . In the mountains, lines of plot are
easily run by going up-and-down the slope, but in flat country a compass
may be needed to run straight lines.

Table 1. Number and spacing of plots.

3. Books

Books provide information on hard-to-measure ecosystem characteristics
such as geology, soils and animal populations. Field guides available at
libraries and bookstores cover nearly every topic imaginable, and are
useful for understanding local conditions, for constructing species lists
and for identifying unusual organisms or conditions. Since identification
of tree species is an essential part of a forest inventory, a tree guide is
indispensable if you are not familiar with the local trees. Soil survey
reports written by the USDA Natural Resources Conservation Service
(formerly called the Soil Conservation Service) are good starting points
since they provide introductions to local climate, geology, and human-
history, while presenting detailed coverage of soils. Soil surveys usually
cover one or two counties, and may be examined in libraries or obtained
from county agriculture extension agents at no charge. In addition to
published material, federal agencies such as the USDA Forest Service; state
divisions of nature preserves, forestry, water and geology; and non-
governmental organizations such as Appalachia - Science in the Public
Interest and The Nature Conservancy can often provide useful unpublished
information regarding forest ecosystems in your locality.

4. Tools

The inventory stick (Fig. 2) is the only tool needed to collect cruise
data (data characterizing individual trees and stands of trees). The
inventory stick is the basis of an inventory method called point sampling
or plotless cruising that allows all stand information to be collected from
a point, without having to establish sample plots of known area. Although
the theory behind the method is complicated, the inventory stick itself is
simple to construct and use. First, obtain a 38-inch piece of tobacco stick
or lattice wood, or a yard stick, and sand or plain both sides smooth.
Marks will be put on one side of the stick to measure tree DBH (diameter at
breast height, or 4.5 feet high) and on the other side to measure tree
height. Starting from the left side of the stick, mark DBH in 2-inch
intervals from 2 to 70 inches at the distances shown in Table 2. Note that
the interval between DBH marks becomes smaller as DBH increases. Now turn
the stick over and mark tree height in units of logs (one log equals 16
feet) with the mark for the first log located 61/16 inches from the left
end of the stick, and successive marks up to 5 logs also spaced at
intervals of 61/16 (Fig. 2).

Table 2. Location of marks on inventory stick.

An angle gauge is added to the stick to allow measurement of an
important stand characteristic called basal area, which is measured in
units of square-feet per acre and represents the cross-sectional area at
breast height of all trees occurring on an acre of land. To make the angle
gauge, drill a hole near the right end of the stick, place a 1-inch metal
washer on an 18-inch long piece of nylon line, thread the line through the
hole, and tie a knot to allow the washer to dangle from the stick. Now put
a notch, about 1/4 inch deep and wide enough to tightly hold the washer,
on one edge of the stick at a point exactly 33 inches from the left side
(Fig. 2). Your inventory stick is now complete and ready to be used in the
field.

Figure 2

5. Data Collection

General Ecosystem Properties

Data describing the local ecosystems may be collected at each
inventory point. Given the complexity of ecosystems, it is obvious that not
all properties can be described. Efforts should focus on collecting
information concerning rare or sensitive species, unique conditions, or
ecologically important features such as caves, cliffs, and cavity trees
(large living hollow trees that are used as dens by many animal species).
As time and ability allow, useful information may also be collected
regarding animals, non-woody plants, soils, bedrock, human land-use
history, and climate. In most locations the construction of simple species
lists (wild flowers, birds, butterflies, ferns, etc.) in itself represents
a major contribution to understanding of the local ecosystems.

Snags (standing dead trees), logs (fallen dead trees), and treefall
mounds-and-pits (small hillocks and depressions that form when a tree
uproots) are three features that are unique to forest ecosystems and are of
special importance in terms of their contributions to biological diversity.
Due to their ecological importance, the density of snags, logs, and mounds-
and-pits should be estimated at each point. This is most easily done by
counting the number of these features that occur within a 1/20-acre
(approximate radius = 25 feet) circular plot surrounding each inventory
point. The number of these features per acre may then be estimated by
calculating the average numbers per plot (total number counted at all the
points divided by the number of points) and multiplying by 20. Snags, logs,
and mounds-and-pits will be discussed in more detail in Part 2 (þEcological
Restorationþ) of this series of papers. Note also that the inventory stick
may be used to estimate horizontal distances. Hold the zero end of the
stick near you leg and note where the dangling washer þpointsþ to the
ground at a spot 3 feet away (Fig. 2). Step to this spot and continue to
point with the stick and pace. For example, 8 sticks plus 1 foot will
approximately delineate the radius of the 1/20-acre plot.

Forests

Data describing forests are collected at each inventory point. Using
the angle gauge, tally trees at each point are recorded by species and 2-
inch DBH class (see sample tally sheet). Insert the washer into the notch
on the inventory stick. Hold the inventory stick with the zero end at your
eye and sight all trees as you turn a complete circle while keeping your
head over the plot center. Move slightly off center to ensure that no trees
are obscured from view by other trees, and that you sight all trees. Trees
are tallied if, when viewed at breast height with one side of the washer
aligned with one side of the trunk, the other side of the trunk projects
beyond the limits of the washer (trees A and D in Fig. 3). If the sides of
the trunk exactly fit the width of the washer, the tree is a border tree
(tree E in Fig. 3); tally only every other border tree at a point. Trees
that are entirely within the angle of the washer are not tallied (trees B
and C in Fig. 3).

Figure 3

The DBH of a tally tree is measured by holding the inventory stick 25
inches from the eye (armþs length) and against the tree at breast height,
with the left end of the stick aligned with the left side of the trunk.
Without moving your head look at the right side of the trunk and read DBH
(to the nearest inch) from the markings on the inventory stick (Fig. 4).
When the tree tally is completed for all inventory points, basal area and
density are calculated as shown under þSample Calculation.þ

Figure 4

Merchantable height should be recorded at a subset (at least 50%) of all
the inventory points to provide an estimate of sawtimber (trees greater
than 10 inches DBH) and poletimber (trees 5.0 to 9.9 inches DBH that yield
pulpwood or cordwood) volumes, and for use in making management decisions
as described in Part 3 (þTending and Harvest) of this series of papers.
Merchantable height for poletimber trees is defined as the height to the
point where the upper stem diameter is 4 inches. Merchantable height for
sawtimber trees is defined as the height to the point where the upper stem
diameter is 8 inches, or to a fork, major branch, or visible defect like a
hole. The merchantable sawtimber height of hardwoods (except yellow-poplar)
is usually limited by branching and forking before the upper stem diameter
decreases to 8 inches. Merchantable height is measured standing on the same
level as the base of the tree at a distance of 66 feet while holding the
inventory stick 25 inches from the eye and parallel to the tree trunk.
Align the bottom of the stick with stump height (stump height = 1 foot) on
the tree and without moving your head sight merchantable height at the
point on the trunk where you think the tree would be cut. Read merchantable
height to the nearest half-log from the marks on the inventory stick (Fig.
5). As you measure merchantable height, estimate percent cull, or the
proportion of the merchantable stem that is useless due to rot or decay.
Although cull estimates on standing trees are difficult to make even for
experienced individuals, look for wounds, bark distortions, holes, and
bumps as indicators of internal defects, and make your best guess. As shown
under þSample Calculations,þ DBH and merchantable height estimates may be
used to calculate gross volumes of sawtimber and cordwood, while cull
estimates may be used to reduce the gross volumes to net volumes.

Figure 5

Sample calculations are illustrated using a set of inventory data on the
following pages. Blank field sheets are also provided for duplication.

Basal Area

The inventory stick was designed to have a basal area factor (BAF) of
10. This means that each tally tree contributes a basal area of 10
sq.feet/acre. To estimate the average basal area for a stand, count the
total number of trees recorded on the dot tally sheet, divide by the total
number of sample points, and multiply by 10. In this case:

(73 --- 7) X 10 = 104 sq.ft/ac basal area

The basal area may be determined in the same way for any DBH-class or
species. For example, the basal are of white oak is:

(34 --- 7) X 10 = 49 sq.ft/ac or 47% of the total

Number of Trees

A BAF of 10 means that each tally tree represents 10 sq.ft/ac of
basal area. Small tally trees must therefore represent many more trees/ac
than large tally trees. To determine the number of trees/ac, multiply the
number of tally trees in each DBH-class by the number listed in the
following table for that DBH-class, then divide by the number of sample
points. In this example, there are 630 trees/ac, and in the 2-4.9 inch DBH-
class there are:
(16 X 204) --- 7 = 466 trees/ac

Volume

Volume is calculated from the DBH - height -%cull data listed on the
second field sheet (above). Poletimber trees and sawtimber trees too poor
to be sawn into boards are considered pulpwood, and volumes are calculated
in units of cords ( a cord is a 4 X 4 X 8 foot stack of wood containing
about 85 cubic feet of solid wood). Sawtimber trees with merchantable
lengths of at least « log are calculated in units of board feet
(abbreviated, BF; MBF = 1,000 BF).

For example, consult the correct volume table to find that the gross
volumes for a tree with DBH = 10 inches and height = 1 log is 0.08 cords as
pulpwood and 14 BF (Doyle scale) as sawtimber. If the cull deduction is
20%, the net volumes for this tree are 0.08 X 0.8 = 0.06 cords, and 14 X
0.8 = 11 BF. Note that volumes are not calculated for trees smaller than 5
inches DBH. Note also that a number of board-foot volume tables exist, and
that the one used must be specified by name.

Total pulpwood or sawtimber volumes are calculated by multiplying the
volume of each tallied tree by the þtrees per acreþ number (see table on
preceding page) for the appropriate DBH-class, adding the results together
for all the trees, and dividing by number of inventory points. For
example, for the two pulp and two sawtimber scarlet oaks recorded in the
sample data:

Pulpwood (0.04 cords/tree X 15 trees/ac) --- 7 = 0.09 cords/ac in 10 inch
DBH trees
(0.12 cords/tree X 8 trees/ac) --- 7 = 0.14 cords/ac in
14 inch DBH trees

0.23 cords/ac

Sawtimber (38 BF/tree X 8 trees/ac) --- 7 = 43 BF/ac in 14 inch DBH trees
(73 BF/tree X 6 trees/ac) ---7 = 63 BF/ac in 17 inch DBH
trees
106
BF/ac

Application of Inventory Results

You are now ready to use the inventory results to restore or maintain
ecological health, and to sustainably tend the forest to provide wood
products. See Supplement 2.