Young Growth Management of Giant Sequoia1
Donald P. Gasser
Giant sequoia is an outstanding candidate species for
management for a variety of reasons, including the production
of wood products. This species combines fast growth with
high quality wood production, and it should be considered as
an alternative when planting new forests, replacing old, or
managing those begun in previous eras. The biology and
ecology of giant sequoia has been addressed in other papers
in this proceedings as well as in recent publications
(Hartesveldt and others 1975; Weatherspoon 1985). This
paper attempts to put this information into a management
context, with particular emphasis on goals which may be
accomplished through manipulation.
Growth
The growth of giant sequoia is of interest to managers
throughout the world. Growth has been examined within,
near, and outside existing groves. Rapid tree growth is an
indicator of how quickly various goals can be reached in
most strategies of management. Within existing sequoia grove
environs, giant sequoia seedlings and saplings consistently
outperform native competitors in height, diameter, and dominance. They have proven to do the same in many places
outside of these groves and well outside of the giant sequoia
range. European results show very impressive growth which
often outperforms both native and exotic conifers (Knigge
and Lewark 1982; Knigge and others 1983; Libby 1981).
At Blodgett Forest Research Station, on the Georgetown
Divide near the northernmost existing grove of giant sequoia,
experimentation with giant sequoia out plantings has been
conducted since the early 1960's. Growth of giant sequoia
planted in selectively cut as well as clearcut stands has
outstripped that of other species.
Compartment 321 was planted in 1981 with six species
following an earlier clearcut. Recent measurements show
giant sequoia height growth (fig. 1a) to be 20 percent greater
than its nearest competitor (ponderosa pine), while it averages
nearly double that of the other native species. Giant sequoia
diameter growth in this same compartment (fig. 1b) is over
20 percent greater than ponderosa pine and nearly triple that
of Douglas-fir, sugar pine, and white fir. A nearby group
selection planted in 1982 shows average height of giant
sequoia 50 percent greater than the nearest competitors
(ponderosa and sugar pines), while its growth triples or even
1
An abbreviated version of this paper was presented at the Symposium
on Giant Sequoias: Their Place in the Ecosystem and Society, June 23-25,
1992, Visalia, California.
120
quadruples the other mixed-conifer natives. Diameter growth
in this same stand is over 60 percent greater than the nearest
competitors, and four to seven times that of other coniferous
species (Heald 1989).
On Whitaker's Forest, which is located in the Redwood
Mountain grove, giant sequoia in mixed stands has consistently shown superior growth since early comparisons were
made by Metcalf (1948). Areas within the giant sequoia
range, such as Mountain Home Demonstration State Forest,
document this same dominance of early growth (Dulitz 1988).
Research areas outside the range of giant sequoia where
spectacular giant sequoia growth is recorded include two
properties managed by the University of California: Baker
Forest near Quincy, and Russell Reservation near Lafayette
(Libby 1992).
At Foresthill, and within 15 miles of the northernmost
grove of natural giant sequoia, a plantation was planted in
1981 on site I A land on deep soils with good rainfall. On
this site, the giant sequoia in mixed plantings were initially
the top growers but have since fallen off, while the ponderosa
pine has surpassed them. An earlier plantation near this
same site, (planted in 1966), shows that the trees have also
slowed their growth, and the color after five years of
drought is chlorotic.
Individual tree growth appears to be affected by the
availability of moisture throughout the growing season. Site
differences are not well understood, and more studies are
needed to determine water timing and amount, genetic differences between groves, soil responses, and measures of
susceptibility to root disease.
Forest Dynamics
Growth of individual trees is only one measure of the
dynamic nature of the giant sequoia forest. Long-term studies
allow the nature of forest development to be examined.
Woody Metcalf (1915) established six permanent growth
plots at Whitaker's Forest which are probably the oldest
such plots in existence in any forest in California. These
have been remeasured over the decades, but now only one
quarter-acre plot has not been disturbed or destroyed by
storms, roads, or otherwise compromised by time or progress.
Despite the lack of degrees of freedom in this data, Metcalf
Plot One shows us some of the dynamics affecting sequoia
young growth.
Figure 2a shows 77 years of stand development in
terms of number of stems in this nearly pure stand of giant
sequoia-facts that are neither new nor startling, but which
do reaffirm basic forestry principles. Many more trees can
be supported on a site when the trees are young than can be
grown on that same site as the trees age. The heavy mortality
USDA Forest Service Gen. Tech. Rep.PSW-151. 1994
Figure 1 a - H e i g h t in plantation following clearcut (Blodgett Forest Research Station,
Compartment 321)
Figure 1b-Diameter at breast height (in.) in plantation following clearcut (Blodgett Forest
Research Station, Compartment 321)
that has occurred (over 60 percent of the original trees have
died) has all been natural, and the stand is now a fire hazard
of standing and fallen dead trees. Some trees are still alive,
but barely, and the data show that some trees may have
virtually the same diameter and height for up to five
decades. While intolerant of shade, once established, giant
sequoia is not readily killed by shade.
Figure 2b details the average diameter of the trees on
this plot. The slow growth in average diameter and the
recent slowing in increase of average diameter at breast
height (DBH) shows the ingrowth of white fir. There is
virtually no other regeneration of any vegetation in this plot.
USDA Forest Service Gen. Tech. Rep.PSW-151. 1994.
The development of this stand in which stagnating trees
and huge second-growth trees are side by side begs the
question of appropriate stocking and spacing of sequoia. A
variety of studies are currently underway in a number of
localities throughout California. Plots already established at
Whitaker's Forest, Blodgett Forest, Mountain Home Demonstration State Forest, and other sites should help answer
these questions.
Basal area measures are those which total the combined
tree girth on an area of land, and these often correlate to an
index of site productivity. The development of basal area on
the Metcalf Plot is shown in figure 2c. It is expected that the
121
Figure 2a-Whitaker's Forest, Metcalf Plot One --Number of Trees
Figure 2b-Whitaker's Forest, Metcalf Plot One--Tree Diameter
Figure 2c-Whitaker's Forest, Metcalf Plot One--Basal Area
122
USDA Forest Service Gen. Tech. Rep.PSW-151. 1994 limit of growth on this plot may be reached in the next
several decades, for a series of inventory plots on Whitaker's
Forest has shown that much of the giant sequoia/mixedconifer forest stabilizes at about 400 square feet of basal area
per acre. This is a measure of the limit of productivity of
this site, and other sites may have a greater or lesser
productive capacity.
It is clear that giant sequoia is capable of holding levels
of growing stock that other species may not attain before
stagnation. The control plots for the study described below
on Mountain Home Demonstration State Forest show levels
between 500 and 600 square feet of basal area.
It is instructive to note that in a 100 percent survey of
old-growth giant sequoia in the National Parks, giant sequoia
consistently carries about 200 square feet of basal area per
acre, and it is a major portion of these stands (Stohlgren
1991). This study measured almost 161,000 giant sequoia
trees in 35 groves. The findings show that over half of the
basal area rests on only 5 percent of the trees.
Response to Manipulation
Bob Martin and Don Gasser on the Mountain Home
Demonstration State Forest are conducting a study to
quantify the development of different forest responses that
are encountered following thinning and burning. Begun in
1989, a total of six stands have been thinned to different
basal area levels (130 and 240 square feet per acre). Half of
the thinned stands were burned following harvest, while one
third of the area acts as a control and has not been thinned or
burned. Permanent plots have been set up and these are
being followed and measured through time. Forest stand
dynamics have developed to reveal patterns of ecological
succession which may be important to future development
and growth, as well as management activities. While still
early in the life of this study, it is clear that giant sequoia
responds quickly to new growing space, and the thinned
stands are showing a growth spurt that is not evident in the
control areas. Understory dynamics are being measured as
well, so that the growth and regeneration of tree, shrub, and
other portions of the forest can be reported under different
management regimes.
Yield
Questions as to yield of the growing forest come about
when the trees are harvested. A recent study at Mountain
Home Demonstration State Forest has brought the two
existing volume measures into question (Pillsbury, De Laissoe,
Dulitz 1992; Wensel, Schoenheide 1971). In the thinning of
the plots discussed above, the measured differences in log
volumes were occasionally 20 percent separate. Sufficient
tests are needed throughout the range to determine the site
specific nature of taper and shape as they influence volume
and value.
USDA Forest Service Gen. Tech. Rep.PSW-151. 1994.
Wood Quality
The findings of numerous studies indicate that the
quality of second-growth redwood is vastly different from
the old-growth of the same species. The brashness for which
the old-growth tree is so well known is the factor that caused
many of the large old trees to splatter upon hitting the ground,
and chunks can still be found in Converse Basin, on Redwood
Mountain, and in other areas that show this phenomenon.
Wood quality of young-growth giant sequoia was first
detailed in California in 1971 and various work since then
has confirmed the earlier information (Cockrell, Knudson,
Stangenberger 1971). In this early research, the qualities of
old- and young-growth redwoods, both coastal and interior,
were compared and contrasted. Young-growth giant sequoia
proves to be a species with qualities that meet or exceed
those of young-growth coastal redwood, at least in terms of
important wood properties of specific gravity, most mechanical
properties, extractive content and decay resistance (fig. 3).
Piirto and Wilcox (1981) found that the wood of younggrowth giant sequoia is both stronger and heavier than that
in old-growth, and that this is the reverse of coastal redwood.
This is shown also to be true for those giant sequoia grown
out of native range (Keylworth 1954; Liubirescu, Guruianu,
Lonescu 1972). Knigge and Lewark (1982) were cautious in
recommending giant sequoia for European demands, as wood
density is an issue in some applications.
The comparison of giant sequoia to coastal redwood is
important, in that the latter is recognized as a superior species,
and regularly sells at the top end of the coniferous board and
product market. Without management, giant sequoia solid
wood product value is very low relative to its inherent
qualities because of the numerous persistent branches. These
branches are a serious detriment to the production of wood
of high quality, and early pruning is necessary to ensure that
the full value of the solid wood product is realized.
With the substantially superior volume growth shown
for giant sequoia, the value for biomass chips should not be
ignored, and a mixed stand of conifers which includes giant
sequoia may be managed from the start for a variety of
products. The ability of giant sequoia to initially colonize
and capture the site may be combined in a product-oriented
strategy that includes pruning only a portion of the stand
designated as crop trees. With advancing age, some trees
may be removed to make room for the high quality growing
crop, while still providing for a high biomass yield.
Operations
The California Forest Practices Act and numerous rules
give protection to the potentially affected resources, but soil,
as the basic resource, deserves special consideration. Most
stands within the native range of giant sequoia are on deep
soils which have access to deep water on a year-round basis.
Careful planning and control of the placement of tractive
123
Giant sequoia*
Mechanical property
Specific gravity#
Static bending
Modulus of rupture (psi)
Modulus of elasticity
(million psi)
Work to maximum load
(in-lb/cu in)
Compression parallel to grainmaximum crushing strength (psi)
Oldgrowth
0.30
5200
Coast redwood+
Younggrowth
Oldgrowth
0.35
0.38
6670
7500
Younggrowth
0.34
5900
0.56
1.14
1.18
0.96
5.3
6.7
7.4
5.7
3110
2700
3510
4200
Compression perpendicular
to grain-fiber stress at
proportional limit (psi)
230
380
420
Maximum shearing strength
parallel to grain (psi)
730
740
800
270
890
*Cockrell (1971).
+USDA Wood Handbook (1974).
#Specific gravity is based on oven-dry weight and green volume. Figure 3-Mechanical properties (green condition): giant sequoia and coast redwood.
equipment is important to ensure that neither displacement
nor compaction take place in the area of the watercourses.
Despite the above proviso that current operations follow,
it is more than interesting to note that the finest stands of
young-growth giant sequoia exist in those areas which were
treated the most harshly and with the least sensitivity a
century ago. Giant sequoia at Whitaker's Forest, Big Stump,
Converse Basin, and numerous other locations which were
virtually clearcut, have impressive young-growth trees
reaching seven feet in diameter and two hundred feet in
height. Huge stumps give testimony to what was there before,
and which will be again, despite primitive logging efforts
which undoubtedly displaced soil following logging and
burning. As described elsewhere in these proceedings, it is
these conditions that give rise to the dense regeneration
which characterizes giant sequoia cut areas.
Current commercial operations within existing groves
are commonly controversial. The soil and water regimes in
many existing groves may limit operations designated for
scenic and aesthetic areas. In these groves, dry season
operation with low ground pressure equipment is prudent.
Post-harvest stump cutting to ground level, or even stump
grinding, would be desirable, due to the longevity and the
visual nature of these stumps. Burning following logging
has been shown to promote a forest floor that is safer
from wildfire, and which may provide regeneration benefits
as well.
Operations in most existing stands will have to contend
with the extreme branchiness and the tendency for significant
taper in open stands. Both of these factors will probably
cause commercial forests to be grown at a higher density and
124
thinned later than other species in order to minimize these
effects. Early pruning of branches may yield significant
returns to the landowner.
In looking at the response of thinning of giant sequoia
on other resource values, minor thinning and understory
manipulation has had little impact on avifauna within the
giant sequoia forest (Kilgore 1971), while a long-term study
by Marshall (1988) details the changes in bird and small
mammal habitat that has occurred on Redwood Mountain
in a 50-year period. Despite low levels of logging in the
immediate area of the sequoias, some bird species have
disappeared from the area. These data suggest that larger
scale harvest of trees from areas outside of the groves may
have a greater affect on bird populations than does minor
manipulation within the groves. A half century of growth and
development of the forest in the absence of operations also
appears to have had an impact on certain wildlife abundance.
Revitalization of deer habitat has resulted in an increase in
deer utilization following thinning and understory cleaning
at Whitaker's Forest (Lawrence, Biswell 1972). Clearly,
manipulation of the forest results in habitat change favoring
some animals but detrimental to the existence of others.
Conclusion
For a species to be a candidate for management, it needs
several characteristics such as growth, value, and responsiveness to manipulation. If the purpose of management is to
allow for goals to be brought to fruition, than the species
must be able to fulfill objectives through manipulation or
other activity.
USDA Forest Service Gen. Tech. Rep.PSW-151. 1994
Even for parks or those areas which are dedicated to
aesthetic purposes, giant sequoia management is a viable
alternative. The fast initial growth and the development of a
substantial bole size makes it a natural for these purposes. In
existing redwood groves, trees may be removed with the
assurance that growth response to manipulation will reward
the landowner with speedy recruitment into the larger size
classes. Low stump cutting will promote the appearance of
old-growth forest characteristics, as stump rotting appears to
be a very slow process.
Proper giant sequoia management can yield useful
products by combining tremendous growth potential, a wide
range of density options, and very responsive reaction to
manipulation. When combined with the high value that the
redwood markets enjoy, it is surprising that so little
management effort has heretofore taken place. A society which
consumes so much should take advantage of a species where
such broad potential exists.
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