PE EIE[R-Rg RESEARCH ON - HJ Andrews Experimental Forest

d.o .b. were made at periodic lengths along th e
felled stems. Since this harvest procedure i s
not effective- for estimating cone productio n
(Ovington, Forrest, and Armstrong 1967 ,
Lotan and Jensen 1970), this is not include d
in the study . Biomass values are reported at
700 C. ovendry weights except for bole materials
(stem wood and bark) which are reporte d
at 102° C. ovendry weights .
Stem biomass was calculated by the Smalian
equation, multiplying each volume segment
by the appropriate wood density observed
from the disks . Stem biomass increments wer e
computed as the difference between Smalian
biomass for the years 1969 and 1968 . Similarly,
bark biomass for each bole was deter -
mined by the Smalian difference betwee n
diameters inside and outside bark, using bark
densities for each volume segment . The increment
of living branches was calculated using
estimative ratios (Whittaker and Woodwel l
1968), assuming that relative branch increments
are approximated by relative ste m
wood increments . Branch mortality was computed
by a canopy displacement model
(Madgwick 1968). The computation assume s
a canopy steady state in which the upward
displacement of the envelope of green foliag e
within a stand leaves a wake of dead branche s
that were alive the previous year . The average
displacement of foliage was further assume d
to be the mean height growth of each stand .
Stem mortality was computed from the mortalities
of table 1, in which the biomass o f
dead stems during the mortality period wa s
determined from the basic allometric relation -
ship between stem biomass and d .b.h .
Calculations were based on the equation s
below :
Biomass and growth increments .
H = total stem length (ft )
T = stem length to crown
(lowest living whorl )
d i , d2 , d 3
= diameter inside bark at ground
level, 1 ft, and lowest living
whorl respectively (inch) .
P 1, P2, P3 = wood densities at ground level ,
1 ft, and lowest living whorl
(g/cc) .
k = conversion constant t o
metric = 0 .0772 2
Ar' 1 , Ore, Ara = mean radial growth (inch) at
ground, 1 ft, and crown base.
Ws = biomass (kg) at 102° C
II. Living branches.
AWb = Wb ~ s
Ws
+ new twig biomass
Branch mortality (per tree) = Wb(AH )
T '
where AH . is average height growth for
stand, T' is stem length within the crown
over which branch mortality is observed ,
and Wb is the live branch biomass along
stem portion T' , Wb is total live branc h
biomass of the crown (along stem lengt h
H-T) .
III. Basic allometric equation .
W = k 1 D k 2 , for biomass W and DBH of D ,
and regression constants ,
k 1 and k 2 .
In the case of plot 4 .3 where a clear trend of
stem wood increment with d .b.h . exists, the
plot increment of stem wood was computed
by linear regression over the independent
variable, d .b.h .
I. Stem .
Ws = k[(di + di )P1 + (di + 43) (T - 1)p2
+(d3 + .75 2 ) (H-T-3)ps ]
AWs = W s - Ws- 1 , where Ws- 1 is obtaine d
by substituting
di - 2Ori for di (i = 1,2,3) .
Litter Productio n
Results
Tables 2 and 3 give annual litter productio n
in the six stands over the 4-year period . The
mean annual litter production was 0 .4 6
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