Andy Gray - Alternatives for creating early seral forest openings
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Transcript of Andy Gray - Alternatives for creating early seral forest openings
Alternatives for creating early seral forest openings
Andrew Gray
What is an early seral forest?
• Early seral=Successional stage after disturbance and before tree canopy closure
• Concept of succession developed from studies of abandoned fields and glacier retreat
• But stand development rarely starts from “bare ground”
• How much disturbance?• What needs to be disturbed?• How long will it remain open?
Important disturbance characteristics
• Disturbance size• Disturbance severity
(residual structure and composition: over- and under-story)
• Available resources: light, soil moisture, nutrients
• Disturbance frequency
Experimental design
Control 1.0 0.6 0.4 0.2
WIND RIVER EXPERIMENTAL FOREST
H.J. ANDREWS EXPERIMENTAL FOREST
Old Growth- McRae Creek ~500 yrs
Gap Size Ratio
x
Old Growth- Trout Creek ~500 yrs Mature- Panther Creek 150 yrs Mature- Martha Creek 95 yrs
Eugene
Spokane
Olympia
Location of 4 stands in study
X
X
Primary set
Secondary set
GAP SIZE =GAP DIAMETER ÷ TREE HEIGHT
Each stand has 2 sets of gap sizes + controls, secondary set was used only for fisheye photographs (and other studies)
Experimental Design
DIAMETERHE
IGH
T
HJA old-growth Trout Ck. old-growth
Panther Ck. mature Martha Ck. mature
Gap light and moisture patterns
N
Light
Soilmoisture
Gap Sizecontrol 0.2 0.4 0.6 1.0
PA
R Q
uant
a (m
ol/m
2/d
ay)
0.0
2.5
5.0
7.5
10.0
12.5
15.0
17.5
20.0 NorthCenterSouth
a a a
a a a a aa
b
b
b
b
abab
Mean daily PAR (+SE), sunny summer days (n=4)
Month and Year of Soil Moisture Sample96959493929190
A S M J J A S O M J J A S O M J J A S O A S S
Soi
l Moi
stur
e (%
vol
umet
ric)
15
20
25
30
35control 0.2 0.4 0.6 1.0
Trends in soil moisture at gap centers, 0-15 cm depth
Fig. 4. Average differences in soil moisture between the clearcut and the forested areas during spring (April-June), summer (July-September), and fall (October-November), 1960-1980. Positive values indicate higher soil moisture in the clearcut area. Solid data points represent significant differences (t~ = 0.05, t-test of inequality) between the clearcut and forested areas.
P.W. Adams et al. 1991. For. Ecol. Manage. 41: 249-263
Soil moisture is temporarily more abundant after clear-cutting
Change in species richness by gap size
5.0
5.5
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
10.0
1990 1991 1992 1993 1994 1995 1997
Year
Mea
n s
pec
ies
rich
nes
s p
er m
icro
plo
t (0
.25
m2)
0
0.2
0.4
0.6
1
Gap sizes
Changes in cover of residual and invader species
0
1
2
3
4
5
6
1990 1991 1992 1993 1994 1995 1997
Year
0
0.2
0.40.6
1
Invader Species
30
40
50
60
70
80
90
100
1990 1991 1992 1993 1994 1995 1997
0
0.2
0.4
0.6
1
Residual SpeciesM
ean
of s
umm
ed c
over
by
spec
ies
grou
p
Residual plants can take the heat
Density of natural regeneration after 3 growing seasons
Den
sity
(#/
m2 )
0.0
0.5
1.0
1.5
2.0
2.5
3.0Douglas-fir
SouthCenterNorth
Gap size
0.0 0.2 0.4 0.6 1.00
10
20
30
40
50
60
70western hemlock
Hemlock in old-growth only.Density in mature stands=0.
Tree canopy closure was faster in old-growth stands
Where’d my early seral go?
Blue River Landscape Study:based on natural-disturbance regimes
Landscape area 1 (N. Fk. Quartz)
Forb species in BRLS study
Landscape Area
Stand type Rank Species Cover SE Species Cover SE Species Cover SE Species Cover SE
1 Mature 1 POMU 3.24 1.68 XETE 0.70 0.44 CIAR4 1.24 0.90 XETE 1.45 0.962 XETE 2.21 1.10 CIVU 0.30 0.21 ANMA 0.61 0.57 CIAR4 1.24 0.803 LIBO3 2.03 1.06 PTAQ 0.09 0.09 XETE 0.58 0.30 PTAQ 0.95 0.644 VISE3 1.00 0.69 CIAR4 0.09 0.08 CIVU 0.47 0.26 POMU 0.56 0.37
2 Mature 1 ATFI 6.52 6.52 ATFI 2.13 2.13 ATFI 6.76 6.762 POMU 5.41 3.08 PTAQ 1.20 1.01 PTAQ 2.56 1.943 PTAQ 3.72 2.72 GATR3 0.43 0.29 POMU 1.28 0.974 LIBO3 2.37 0.71 ADBI 0.35 0.31 CHAN9 1.00 0.60
2 Old-growth 1 LIBO3 3.82 1.50 LIBO3 0.38 0.19 LIBO3 3.83 2.532 COLA3 1.06 0.44 XETE 0.33 0.24 CHAN9 3.13 0.743 POMU 0.55 0.45 VISE3 0.19 0.08 SESY 1.67 0.994 VISE3 0.53 0.17 TRBO2 0.07 0.05 TITR 1.13 1.13
3 Mature 1 ACTR 2.68 0.952 VAHE 2.63 1.243 LIBO3 2.38 1.144 VISE3 1.35 0.26
Pretreatment Year 0 Year 2 Year 4
Teakettle study: burn and/or thin?No thin CASPO thin Shelterwood
No burn
Burn
0
10
20
30
40
50
No thin CASPO Shelterwood No thin CASPO Shelterwood
Mea
n o
f su
mm
ed c
ove
r b
y g
rou
p
herbshrub
Understory response to thinning and burning
No burn Burn
No burn Burn No burn Burn
white fir incense-cedar
Jeffrey pine sugar pine
Is NFMA a barrier to enhancing early-seral forest?
"... all forested lands in the National Forest System shall be maintained in appropriate forest cover with species of trees, degree of stocking, rate of growth, and conditions of stand designed to secure the maximum benefits of multiple use sustained yield management in accordance with land management plans.”
Seral conditions on private lands
Conclusions
• Relatively small gaps or light thinnings in the overstory create local hot-spots of early seral plants, may be beneficial to many organisms.
• Understory density and disturbance affects composition and the speed of crown closure.
• Light prescriptions can be counterproductive; severe or repeated disturbances may be important for maintaining high-quality early seral conditions.