hlp 1997 12 prsnttn workshpstructuralattributesofconiferousstandsdisturbedbyloggingandwildfire
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https://foothillsri.ca/sites/default/files/null/HLP_1997_12_Prsnttn_WorkshpStructuralAttributesofConiferousStandsDisturbedbyLoggingandWildfire.pdfTRANSCRIPT
Structural Attributes
of Coniferous Stands
Disturbed by Logging
and Wildfire:
A Reality Check
Hierarchical Spatial Scales
100 km
10 km
0.001 km
Mosaic of many wildfire patches
Within-patch structure
Structure
within a
stand
Disturbance Workshop, 09Dec97 3
Wildfire and Logging in the Foothills
Wildfires have occurred for many years
Logging is recent, and is intended to replace
wildfire on lands allocated for sustained yield
of fibre
Ecological effects of logging relative to fire are
unclear
One ecological effect: modification of forest structure through removal of
tree boles during logging
boles frequently are retained during wildfire
major input source of down deadwood material
Disturbance Workshop, 09Dec97 6
Natural Disturbance as a Template?
Makes several assumptions:
“human activities can approximate
natural processes, at least to some
degree” Alberta Forest Conservation Strategy, draft July 8, 1996
How do human activities (clearcutting)
compare to natural processes (wildfire)?
Disturbance Workshop, 09Dec97 7
Forest structure
Live trees: density, size, species composition
Dead trees: density, size, species composition Standing dead trees (snags)
Down deadwood material
Deadwood material Involved in ecological processes such as
decomposition
Structure contributes to the presence of species
deadwood material is frequently abundant in stand
of pyrogenic origin
Disturbance Workshop, 09Dec97 9
Forest Structure and Disturbance
Has rarely been estimated except
immediately after disturbance
Poor understanding of the dynamics of
deadwood material in burned and logged
stands, & how abundance and condition
may differ through time
Disturbance Workshop, 09Dec97 10
Stand Structure Project
Primary Researchers Dan Farr
Chris Spytz
George Mercer
Supporting Agencies Foothills Model Forest
Jasper National Park
Weldwood of Canada
Preliminary data, ms in prep
Disturbance Workshop, 09Dec97 11
Research Objective
Estimate and compare the range of
variability in the origin, abundance and
condition of deadwood material and live
trees recently disturbed by wildfire and by
clearcut harvesting
Disturbance Workshop, 09Dec97 12
Study areas
1 Mountain wildfire 34 yr.
3 Foothills wildfires 35 - 40 yr.
3 Foothills harvests 23 - 27 yr.
0 50 100 KilometersN
Disturbance Workshop, 09Dec97 13
Sample plot layout
30 plots per site
(15 in Mountain burn)
randomly located
(almost)
#S
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0 5 10 Kilometers
Lynx Creek
Disturbance Workshop, 09Dec97 14
30 m
390 m2
Sampling method
down deadwood
standing dead
standing live
Disturbance Workshop, 09Dec97 16
Results
Ranges of variability in burned & logged stands
Live trees, abundance and size
Standing dead trees, abundance & condition
Pre-disturbance & Post-disturbance
Down deadwood, abundance & condition
Pre-disturbance & Post-disturbance
Infer probable successional trajectories for
deadwood in these burned and logged stands
Disturbance Workshop, 09Dec97 17
Years since disturbance
Time since disturbance (yr)
0 10 20 30 40
De
nsit
y o
f liv
e t
ree
s (
pe
r h
a)
0
10000
20000
30000
Logged
Burned
Density of Live Trees
Mean: Burned > Logged
Variability: Burned > Logged
(mean SD)
Disturbance Workshop, 09Dec97 18
Live trees: Size Distribution
Burned
0
5000
10000
Logged
Diameter (cm)
0 10 20 30 40 50
0
5000
10000
Mea
n d
ensity p
er
plo
t (t
rees /
ha
)
mean of 3 sites
Disturbance Workshop, 09Dec97 21
Live Trees: Species Composition
ChabaGregg
Gregg
Lynx
Lynx
Smith
Smith
Lodgepole Pine
Black Spruce
White Spruce
Subalpine Fir
Poplar / Birch
Burned
Logged % Basal Area
Disturbance Workshop, 09Dec97 22
Distinguishing Deadwood Origin
0
2
4
6
8
0 10 20 30 40 50
Diameter (cm)
Nu
mb
er
co
un
ted
Live Standing Dead Down Dead
Smith Burn Plot #17
Standing Dead Trees
Disturbance Workshop, 09Dec97 27
Standing Dead Trees: Pre-disturbance
Time since disturbance (yr)
0 10 20 30 40No. sta
ndin
g d
ead t
ree
s
0
20
40
60
Logged
Burned
Mean: Burned > Logged
Variability: Burned > Logged
(mean SD)
Disturbance Workshop, 09Dec97 28
Standing Dead Trees: Post-disturbance
Time since disturbance (yr)
0 10 20 30 40No. sta
ndin
g d
ead t
ree
s
0
20
40
60
Logged
Burned
Mean: Burned > Logged
Variability: Burned > Logged
(mean SD)
Disturbance Workshop, 09Dec97 29
Standing Dead Trees: Size Distribution
Pre-disturbance
Post-disturbance
Burned
0
10
20
Logged
Diameter (cm)
0 10 20 30 40 50
0
10
20
mean of 3 sites
Disturbance Workshop, 09Dec97 30
Standing Dead Trees: Decay Pattern
Burned
0
10
Pre-disturbance
Post-disturbance
Logged
Decay class
3 4 5 6 70
10
Mea
n #
sta
ndin
g d
ea
d tre
es p
er
plo
t
mean of 3 sites
Down Deadwood Material
Disturbance Workshop, 09Dec97 32
Down Deadwood: Pre-disturbance
Time since disturbance (yr)
0 10 20 30 40
No.
pie
ces o
f d
ow
n d
eadw
oo
d
0
25
50
75
100
Logged
Burned
(> 7 cm diameter)
Mean: Burned > Logged
Variability: Burned > Logged
(mean SD)
Disturbance Workshop, 09Dec97 33
Down Deadwood: Post-disturbance
Time since disturbance (yr)
0 10 20 30 40
No.
pie
ces o
f d
ow
n d
eadw
oo
d
0
25
50
75
100
Logged
Burned
(> 7 cm diameter)
Mean: Burned = Logged
Variability: Burned = Logged
(mean SD)
Disturbance Workshop, 09Dec97 34
Down Deadwood: Size Distribution
0
10
20
30
Piece diameter (cm)
0 10 20 30 40 50
0
10
20
30
Pre-disturbance
Post-disturbance
Burned
Logged
Me
an n
um
be
r of
pie
ces p
er
plo
t
mean of 3 sites
Disturbance Workshop, 09Dec97 35
Burned
0
10
20
Pre-disturbance
Post-disturbance
Log decay class
1 2 3 4 50
10
20
Burned
Logged
Me
an n
um
be
r of
pie
ces p
er
plo
t
Down Deadwood: Decay Pattern
mean of 3 sites
Disturbance Workshop, 09Dec97 36
Down Deadwood: Height above ground
Pre-disturbance
Post-disturbance0
10
20
30
Piece height (cm)
00-
10
10-2
0
20-3
0>3
00
10
20
30
Burned
Logged
Me
an n
um
be
r of
pie
ces p
er
plo
t
mean of 3 sites
Disturbance Workshop, 09Dec97 38
Summary of Major Findings
Burned stands (36 - 40 yr) deadwood carried over from previous stand was
highly variable, occasionally abundant
few standing dead trees
occasionally abundant down deadwood elevation above ground may slow decay
Logged stands (23 - 27 yr) less (and less variable) deadwood carried over
from previous stand compared to burned stands
very few standing dead trees
fewer pieces of down deadwood contact with ground may accelerate decay
Disturbance Workshop, 09Dec97 39
Successional trajectory: Fire & Logging D
ea
dw
oo
d c
arr
ied o
ve
r
from
pre
vio
us s
tand
Time since disturbance
Next disturbance? Next disturbance?
Disturbance Workshop, 09Dec97 40
Pathways for deadwood material carried over from
previous stand overlap, but average amounts may
differ considerably for many decades after disturbance
Probable effects of return interval:
Fire: Variable return interval
Logging: Less variable return interval (?)
Successional trajectory: Fire & Logging
shorter interval between disturbances
reduction in deadwood supply
longer interval between disturbances
increase in deadwood supply
Disturbance Workshop, 09Dec97 41
Additional considerations
Adoption of the natural disturbance model
may be more difficult at stand scales
compared to landscape scales
Construction of yield curves for some
wildlife habitat variables should distinguish
among origin types fire vs logging
Ecological function of future logged stands
may be dissimilar to similar-aged burned
stands
Disturbance Workshop, 09Dec97 42
Silvicultural solutions?
IF: An increase in the supply of deadwood
material in future logged stands is a
desired outcome of management,
AND: Material retained during harvest may
be standing or down,
THEN: Retention of standing live and dead
trees during harvest would provide a
potential source of future down deadwood
several decades after harvest
