G SOUTH EST
FOREST SERVICE:
U.S.DEPARTMENT OF AGRICULTURE
P. O.BOX 245, BERKELEY, CALIFORNIA 94701
AL
GRASSES REDUCE
WOODY PLANT SEEDL NGS.. . on mixed coni
Harry E. Schimke
U.S.D.A . Forest Service
Research Note PSW-203
"id970
Lisle R. Green
Danny Heavilin
The forest manager is faced with speedy regrowth
of tsm& and trees on fuel-breaks following removal
of the original cover in the central Sierra mhed
conifer zone. To prevent this, he must respond with
some combination of herbicides, mechanical e q i p ment, hand labor, and competing vegetation.
h r i n g fuel-bre& constmction on the Stanislaus
Nationd Forest in central Cdifornia in 1962-63,
perennial grass was planted on l@foot-wide drdl
strips on one fuel-break sement,and alternate strips
were unseede0.l Pine trees were to "s planted on
these unseeded strips, but never were. Now, some 5
years later, the unseeded strips are domhated by
naturally regenerated pine and bmsh seedlings. The
strips and areas seeded to perennid grasses are
occupied primardy by seeded grasses. This sugests
that perennid grasses can be of considerable help in
fuel-break mgntenmce.
METHODS
ABSTWACE After h i ~ dcledng, parts of a fuelbreak on the St=idaus Nationd Fores& central
CdZomia, were planted to perennial grasses; other
p a t s werre not. After 5 years, a comparison between
adjacent seeded sand unseeded strips shows that the
perernnids had reduced the number of woody plant
seedlhgs by a factor of 8, hei&t of seedlkgs by 50
percent, and amount of m n u d plant gound cover by
33 percent. Without perenmid grass, the site would be
reoccupied by woody plmts in a very few yeas.
OXFORD: 432.317:U582.542.1:]L87 X 665.75.
RETRHE VAL T E M : fuel-break cover; perennial
gass; woody plant cover; seedlhg repression; Stanislaus National Forest.
The study site has a scratteslng of ponderosa pine
trees, a few sugar pines, and before being cleared for
fuel-break had m uderstomr~,of bmsh-mostly whiteleaf mmzanita (Arctosraphylos viscida Parry). Exposure is east to south to west in a ""U9shape around a
slope ran@ng from 0 to 28 percent gradient. Elevation is about 4,000 Eeet. The soil is Marigosa sfit
loam, contains smdl rock f r a ~ e n t sand
, is about 20
inches deep. The site is mar@nd h r timber
pro duc"eon,
Perennid grasses were seeded with a rangeland drjill
in strips dong the contour skaortly after bulldozer
clearing early in winter 196'2-63. Skeded species and
approximate rates were: hardinwass, 3% poouds;
pubescent wheatgrass, 3 pounds; and smdo, M pound
-a total sf 7 pounds per acre. 'Ihe seeded strips were
fe'ertdked with ammonium phosphate (16-20-0) at
100 pounds per acre, applied throu& the drill with
the seed.
Paired plots, each a ma-aere in size, were established by randody locating 30 plots in the center of
the contour drilled strips, then locating the unseeded
"mate'yn the strip hmediately above the seeded
plots.
The following data were gathered on each plot in
June 196 8:
1. Number of pine and bm& seedlings.
2. Estimated area of plot covered by pine and
bnr& seedlhgs.
3. Hei@t of a representative sample of pine ana
Ism& seedfings.
4. hhrea of plot drill. strips occupied by perennial
gasses as deterdned by measurhg linear distance in
each drill row occupied by perennial gasses.
5. Esthated area of plot covered by herbaceous
plants other than perennials.
The difference between the seeded and unseeded
areas was maked (able 1;fig. I). Mter 5 years, the
unseeded plots averaged 15.4 tree sedlings; the
seeded plots, 1,9. The unseeded plots averaged 19.8
bmr& seedlhgs; the seeded plots, 2.2. 'l"hus, there
were 3 5,200 woody plants per acre, or one bm& or
tree seedlhg for each 1.2 squae feet, where no @ass
competition existed. S e Q h g @ass reduced the average total woody plant count to 4,100 plants per acre,
or one for each 10.6 squxe feet. Most of these plants
were concentrated in breaks in the gass stand. Few
bmsh or tree seedlings grew where the grass stand was
conthuous,
The competition afforded by perennial grasses
reduced both the size and number of tree and brush
seedbgs. Both trees and bmsh on seeded strips were
about hdf as tall as those on unseeded strips. Because
of this difference, and the greatly reduced number of
glmts, woody plants occupied almost one-fourth (23
percent) of the aanseeded plot area, but o d y 0.5
percent of the seeded plot.
Growth of m n u d gasses and f o r b was also
restricted by perennid grass, but not as severely as
were tree and shmb seedlhg. Winter annuds, suck as
soft chess, red brome, and cheatgass were most
abundant in this goup. Common forbs included
alfilaiaia and chickweed.
DISCUSSION
%me of the reduction in size and numbers of
woody plmt seedlhgs could be attributed to cultivation by the drill during seeding, a treatment the
alternate strips did not get. But this difference was .
not sigificant, we believe, for several reasons: (a)
This type of disturbance usudy promotes growth of
bm& seedlings; (b) d l of the pound was tractorcleaned to mherd soil before planting; (c) the grass
drillhg was done during the s m e whter as the
tractor clearhg and "sfore woody plant emergence;
(d) the rangeland drill disturbs only about one-thkd
of the ground mrface, and numerous woody plant
seedEngs would have sunived; and Gndly, (e) there
are spots that were disturbed by the drill but where
Table 1-DItfferences in vqetation r n w t h l on strips of fuel-breaks drill-seeded to perennhl
~ Q S and
S
orit strip not seeded, StanisEaus National firesf, alifomia
Dgference
Standad error
* Statisticdly siaficml at 5 percent level.
**Sta"cstically si@%cant at 10 percent level.
lwoody vegetation was p1-iincipdly 5-year-old ponderos pine and whiteled mmzwzanib
seedhgs.
2 ~ e a s u ~ eonly
d when both paired plots had trees, brush, or both. If all heights were
included, averages ape:
Unseeded stxip: Trees-9 inches, bmsh-9.1 hches
Seeded strips: T~ees-2.3 inches, bmsh-3 inches.
Figure 1-A thick stand of woody
p lan t seedlings developed on
"kave" strips,left, but very few on
strips occupied by perelia~zialpass.
seed was not plmted, or if planted it did not
germlirnate for some reason. Such spots are now
occupied by mmzanita and pine seedlings.
The results are important to the forest mmager
who must consider fuel-bre& m&ntenmce. Fuelbreak that was orijlgjinally deared at great expense
without seeding can quiclk8y become choked with
woody vegetation, m d after a few years, lose much of
its value as a fuel-break. k e a s with a good perennid
grass stand give no inacation after 6 years that they
will not function as fuel-breaks for mmy more years,
On seeded portions of the fuel-bre&s at the Stanislaus Nationd Forest, woody g o m h is concentrated
in voids in the @ass stand. Scattered clumps of
woody grow& can often be tolerated, and may help
provide w d d ~ f ecover and improve fuel-break appeaante.
If woody plmt seedhgs are abundant and distributed so they threaten fire control values of the
fuel-break, they must be removed by herbicides or
prexribed fire. This removd is generally accompbshed most easily while the woody plants are smdl.
Experience elsewEhere2 in Cdifornia sugests that
once woody plant gowth is eliminated from a
perennid grass stand, woody pliant reinvasion will be
slow. khultz and Biswell%and Bentley suggesked
that annud ryegass may suppress seedling grow^
during the year fogowkg seeding better than perennial grasses. But mnual yepass u m d y disappears
within 3 to 5 years, and therefore cannot be
recommended for longgtime fuel-break use.
P e r e n ~ dgasses provide the best fuel-bre& cover
we have, They are low in volume and in burning
intensity. They do not spot much when burning, and
provide a relatively safe area for Grefi@ting operations. h d because soit on gadients normadly seeded
is stabjilized and protected, bttle erosion occurs.
Perennid grass dso increases the Iliwstock and deer
carryling-capzity of a forest. These advantages of
perennids, together with their comptitive vdue,
should encourage their use on d l fuel-breah to wEcB.1
they are adapted.
Notes
IA research and action program dmed at cornffhagatiorn
control a r o u a forest mmagemmt, emied out by the
Cdgonnia R e ~ o n ,Stanislaus Nationd Forest, and Pacific
Southwest Forest and Range Exge6ment Station of the
Service.
,Forest
2 ~ e n t ~ e yJay
, R.; Green, Lisle R.; and Evanko, A. B.
Bineiples and techniques in convert& native chagamal to
stable passland in Glifornk. Proe. El: Int. Grasslmd Congress, HelsinE, Fhlmd 1966: 55-59. 1966.
3~chultz,A. M., a d Bisweu, H.H. Ccprnpeti~onbetween
~ Q S S C reseeded
S
on burned, BmshE~ndsin Californb. J. Range
Manage. 5(5): 338-345. 1952.
"~ersond cor~espondenwwith Jay R. Bentley, Pacsc SW.
Forest & Rmge Exp. Sta., Berkeley, Calif. Jim. 6, 1969.
The Authors
W M Y E. SCHIIMm, a forestry reseach t e e h ~ c i mstationed at Sonora,
Mi&',,
is assiped to the Station's research on f u d k a a d reduction by
convertkg ckapzrd to grass cover. He joined the Station staff in 1962,
after service with the Cdaveras Ranger District, Sta~slausNation& Forest.
LISLE R. GREEN heads fuel hazslrd reduction studies, with headquatens
at Riverside, Calif. He holds bachelor's (1941) and master's (1948) degrees
in. ranrpe mmqsgement from Ut& State Unkersity. He has been on the
Berkeley station staff since 1948, except for 5 y e a s when he bught range
nnmgerment m d soil sdence at Cdgomia State PoEytechic College.
D A H Y HEAWILm a forestry research technician, formedy stationed at
Everside, is now assimed to the Station's reseach staff at k c a t a , Caw.
He joined the Forest Service in 1966.
. . . Conducts forest and r a g e resexcka at more than 75 I w a ~ o mfrom h e d o R w to
Masks md Haw&i.
. . . Pdcipates v&th dl State f m s t q agencies in.cooperative progms to pr&wt md hprove the Na~on9s
395
on acres of State, lwd, m d p ~ v a t forest
e
Bmds.
. . . Mmages md pmtects the 187-rn3~on-skereN a ~ o n dForest System for wst~mtedyield
of its mmy prducts m d sewices.