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CanadianForestryService

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NATURAL RESOUHCES CANADA

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Our file Notre reference

Forest Insect and Disease Survey,

Pacific Forest Research Centre506 West Burnside RoadVictoria, B.C. , vaz 1M5

November 30, 1982

SPECIAL REPORT

SURVEY FOR DWARF MISTLETOE INFECTION IN LODGEPOLE PINE

REGENERATION UNDER MOUNTAIN PINE BEETLE-ATTACKED STANDS

IN THE CHILCOTIN,

by

T.L. Shore, R.J. Andrews, and G.A. Van Sickle

PURPOSE

In the Cariboo Region large areas of mature lodgepole pine

have been killed by the mountain pine beetle (MPB). There is also

a high rate of dwarf mistletoe (DM) infection in these stands. An

estimate of the proportion of natural regeneration infected with DM

is needed as a basis for-prescribing silvicultural treatments

necessary to return this land to productive forest. This was a

pilot survey to evaluate methods, type of information obtained and

population variance.

METHODS

TI1e Tatla Lake-McClinchy Creek area in the west Chilcotin

was selected for study because it is predominantly covered in lodgepole

pine which has been heavily attacked by MPB. A series of eight cruise

lines, spaced systematically at 16 kilometre intervals along the roads

beginning at Chilanko Forks, were run on September 21-22, 1982. Along

each line five 30 m2

circular plots, spaced at 5D m intervals, were

sampled. All seedlings falling within the plot radius were tallied as

- 2 -

infected or uninfected. Height was recorded for all sampled

seedlings and age was recorded for the closest seedling to centre

in each stocked quadrant. Information on the overstory was ob­

tained through a prism sweep at each plot centre. The status of

DM and }WB was recorded within the variable plot. A more detailed

description of the sampling method and rationale is given in

Appendix I.

RESuLTS

An average of 15.2 percent of the lodgepole pine regeneration

was infected with dwarf mistletoe (Table 1). The amount of infection

varied widely by location with very low infection levels occurring

between Chilanko Forks and Tatla Lake and much higher levels west

of Tatla Lake. Infection levels coincided with the age of regen­

eration. The stands west of Tatla Lake generally had older regen­

eration than the eastern stands (Table 1). It should be noted that

symptoms of DM are more visible in larger regeneration. This intro­

duces a source of negative bias to the survey as infection may go

undetected in very small seedlings. The sampling frequency and

percentage infection of lodgepole pine regeneration by height class

are shown in Figure 1.

The overstory was in generally poor condition with an average

28.8 percent of the trees, representing 38.9 percent of the volume,

killed by MPB and 41.1 percent of the trees infested with DM (Table 2).

Approximately six percent of the MPB-killed trees were currently

attacked· which suggests that the beetle will continue to be active in

these stands for several years. Up to 43.5 percent of the overstory

was infected in the stands east of Tatla Lake. With time, these trees

probably will cause an increase in the presently low proportion of

infected seedlings in the area. There was a higher percentage of

infection (43.4) in the unattacked trees than in those killed by ~WB

(25.2). Consequently, as the MPB-killed trees decay and the stands

open up, an increasing proportion of the residual overstory will be

producing DM seed to further infect the regeneration.

TABL

E1

.R

esu

lts

of

asu

rvey

for

dw

arf

mis

tleto

e(D

M)

inlo

dg

ep

ole

pin

ere

gen

era

tio

nu

nd

erm

ou

nta

inp

ine

beetl

e-a

ttack

ed

stan

ds

inth

eC

hi.

leo

tin

,C

arib

oo

Reg

ion

,19

82

.

Num

ber

of

Perc

en

tN

umbe

ro

fA

ver

age

1A

ver

age

Av

erag

e2

Lo

cati

on

Seed

lin

gs

Infe

cte

dS

eed

lin

gs

Pe.r

cen

tH

eig

ht

(m)

Age

Ex

amin

edw

ith

DMp

er

ha

Sto

ck

ing

Py

per

Lk.

Rd.

521.

.93

,46

76

0<

0.5

8.0

Tatl

aL

k.N

.21

0.0

1,4

00

50

1.7

16

.4.

Tatl

aL

k.s.

370

.02

,46

7.55

<0

.51

0.6

Hor

nL

k.R

d.

80

.053

33

20

33

.21

5.3

Jet.

Hor

nL

k.R

d.-

Tat

lay

ok

oL

k.R

d.4

128

9.4

8,5

33

100

1.4

11

.6

18K

m.

w.o

fT

atl

aL

k.31

54

.82

,06

745

5.9

25

.0

462

35

.54

,13

36

0C

learw

ate

rL

k.1

.42

3.9

8K

m.

N.

of

~lcClinchy

Cr.

Bri

dg

e40

20

.02

,66

765

2.9

27

.8

Perc

en

tag

eo

fse

ed

lin

gs

infe

cte

dw

ith

D.M

.1

5.2

+1

3.6

(0<

=0

.10

)

lQu

ad

ran

tsco

nta

inin

go

ne

or

mor

ese

ed

lin

gs

wer

eco

nsi

dere

dst

ock

ed

;b

ased

onfi

ve

30m

2cir

cu

lar

plo

tsp

er

locati

on

.2

Bas

edon

on

etr

ee

per

sto

ck

ed

qu

ad

ran

t.

3rf

~lit

esp

ruce

reg

en

era

tio

nis

inclu

ded

this

beco

mes

2,8

67

seed

lin

gs

per

ha,

45p

erc

en

tst

ock

ing

.4 A

rea

log

ged

leav

ing

scatt

ere

dre

sid

uals

.

I~

I

-4-

Frequency of sampling and dwarf mistletoe infection byFIGU-RE 1.

------.----- ------,II

height class of lodgepole pine regeneration, Cariboo, 1982.

Infected

Uninfected

30.0%

16.7%

71.4% ;33.3% 100.07 a IOO . O% 0.0% f

._r._~~~__._~~~=:::r-~O~.O~%~.__. __J3 4 5 6 7 8 9 10 11 1221a

2209.6%

210

180 j~z 160

i~::JCY~

J~

140~

f..')ZHH

120~en

100

8017.8%

60

16~3%

40

20

HEIGHT CLASS (t--f)

TABL

E2

.S

tatu

so

fth

elo

dg

ep

ole

pin

eo

vers

tory

wit

hre

spect

tod

war

fm

istl

eto

ean

dm

ou

nta

inp

ine

beetl

ein

the

Ch

ilco

tin

,C

arib

oo

Reg

ion

,19

82.

Ste

ms

per

ha

Vol

ume

3P

erc

en

tag

eo

fT

ota

lL

ocati

on

per

haem

)S

tern

sp

erh

aV

olum

eh

a,

MPB

2p

erDM

J.T

ota

lDl

-1M

PB

To

tal

D~1

11PB

DM:t-'

1PB

Py

per

Lk.

Rd.

29

.22

19

.55

38

.59

.45

1.3

91

.65

.44

0.8

10

.35

6.0

Tatl

aL

k.N

.1

41

.57

13

.91

,09

7.1

8.5

.52

.28

6.8

12

.96

5.

19

.86

0.1

Tatl

aL

k.s.

28

2.1

16

6.8

64

7.8

11

.81

7.7

33

.14

3.5

25

.73

5.6

53

.5

Hor

nL

k.R

d.3

53

.03

00

.21

,06

0.6

25

.24

0.5

71

.43

3.3

28

.33

5.3

56

.7

Jet.

lIarn

Lk

.R

d.-

32

01

.60

.02

01

.61

7.2

0.0

17

.21

00

.00

.01

00

.00

.0T

atla

yo

ko

Lk.

Rd.

18K

m.

w.o

fT

atl

aL

k.6

01

.542

4.7

82

6.7

83

.44

5.2

99

.37

2.R

51

.48l~.

04

5.5

.-3

14

1.7

49

.12

59

.91

8.2

14

.23

6.2

Cle

arw

ate

rL

k.5

4.5

18

.95

0.3

39

.2

8K

m.

N.

of

McC

line

hyC

r.B

rid

ge

26

.30

.04

28

.74~6

0.0

39

.16

.10

.01

1.8

0.0

AVER

AGE

22

2.1

23

4.3

63

2.6

22

.32

7.6

59

.34

1.1

28

.84

2.1

38

.9

1 DMin

fecte

dw

ith

dw

arf

mis

tleto

e.

? -MPB

kil

led

by

mo

un

tain

pin

eb

eetl

e.

3lo

gg

edle

av

ing

scatt

ere

dre

sid

uals

.A

rea

I V1 I

- 6 -

Generally, stocking levels of the regeneration were fairly

good with art average of 3,450 seedlings per ha (including white

spruce at Horn Lake Rd.) and 60 percent stocking (0.8 milhectare

quadrants) (Table 1). The height distribution of this regeneration

is approxima ted by that of the sample (Figure 1).

~~AGEMENT CONSIDERATIONS

In the stands examined, :MPB attacks have killed up to 65

percent of the larger mature trees under which varying amounts of

advanced regeneration exist. From 0 to 55 percent of this regen­

eration is already infected with DM and, as 43 percent of the

overstory trees surviving the bark beetle are DM infected, a

continuing source of infection remains... · The production of D1"1

seed from these trees will likely increase with increased light

as the stand opens, and decreased overstory stocking will allow

more of the seed to reach the regeneration. As the regeneration

grows it presents a larger target and the probability of being

infected increases.

A plan for identifying and priorizing treatment of such DM

infected stands should be considered and policy-based thresholds for

management action established. As shown in Fig. 2, depending on yet

to be determined levels of stocking and DM infection, stand management

options could include at least:

1. do nothing, stand should reach maturity with minimallosses;

2. remove infected overstory residuals;

3. remove infected overstory residuals and sanitize advancedregeneration;

4. remove overstory and regeneration and re-establishstand.

In order to utilize percent infection in management decision­

making, the precision of the estimates will need to be increased. This

will involve running many more lines. On the basis of this pilot

survey, approximately 80 lines would be required to reduce the error

to within 25 percent of.the mean at the 90 percent probability level.

- 7 -

FIGURE 2. A possible format for relating stand management

options to percentage of regeneration infected

with dwarf mistletoe.

Ds----------------~ toc lng enslty--------------

Remove Overstory and Regen and Re-establish

Stand

IiI

Remove Overstory and Sanitize AdvancedbOlI :>... CI(1) H e,-11

Regenrl ctl +JI~+J CIo..c: cUI

f--=,-Q)--,:-fT(J) S P-4 I

I Remove Overstory1I

.-I

Do Nothing, stand should reach maturity with

minimal loss

a

III

o

Percentage

of

Regeneration

Infected

- 8 -

Literature Cited

Cochran, W.G. 1977. Sampling Techniques, 3rd Ed. John Wiley

and Sons. New York. 428 pp.

Freese, F. 1962. Elementary Forest Sampling. USDA Agriculture

Handbook No. 232. 91 pp.

Scheaffer, R.L., W. Mendenhall and L. Ott. 1979. Elementary

Survey Sampling, 2nd Edition. Duxbury Press, Massachusetts.

278 pp.

( i)

APPENDIX I

The sampling design used was Repeated Systematic Sampling

C.Scheaffer et ale 1979). The average proportion of seedlings

infected with dwarf mistletoe on each line was determined and the

average and variance of the infected proportions between lines

calculated. TIlis is basically a two stage sampling technique with

the lines as the first stage and plots as the second stage. As

the sample size was very small in comparison with the population,

the variance component is mainly between primary units (Cochran

1977). Also, because the plots on a line are not independent of

one another, a simple random sampling approach cannot be justified.

Although the plots are of equal size there is an unequal nt@ber of

seedlings in the plots. Thus the proportion of infected seedlings

for each line was calculated using a ratio approach (Freese 1962;

Cochran 1977).

Due to manpower and time constraints a sample size of eight

lines was selected. The origins of the lines were on the roads

intersecting the study area and were spaced systematically, with a

random start, at sixteen kilometre intervals. This interval was

based on total length of main roads intersecting the study area

divided by the sample .size. If the systematically selected line

origin point was "out of type" the first subsequent "in type" location

was selected. If both sides of the road were "in type", one was

selected randomly. Plots were spaced systematically with a random

start at 50 m intervals. The line was on a bearing perpendicular

to the road except where all five plots could not be contained "in

type" in which case a 900

turn was made at the last "in type" plot

on that bearing.

RECOMMENDED 110FIFICATIONS TO THE SURVEY METHOD

The plot size should be increased to include more seedlings.

A 50 m2

(4.0 m radius) plot size is recommended as this would also be

compatible with BCMF regeneration surveys.

(ii)

It is also recommended that- instead of running five plots

on a straight line perpendicular to the road, a 900

turn should be

made at the second plot and again at the third plot thus forming

an open rectangle. This would return the crew to the vicinity of

the road thereby reducing walking time and also reduce the risk

of running "out of type".