9th IUFRO: Uneven-aged Silviculture 2014, Birmensdorf ZH, Switzerland
Concept and application of uneven-aged
silviculture in China: A case study of larch
plantations in Northeast China
Zhu JJ, Yan QL, Yu LZ
State Key Laboratory of Forest and Soil Ecology, Qingyuan
Experimental Station of Forest Ecology, Institute of Applied
Ecology, Chinese Academy of Sciences (CAS), China
June 19 2014
Concept of uneven-aged silviculture in China
2
Two stages of China forest management since 1949
Forest management for
timber harvest
(before 1998)
Characterized by excessive
cutting, and ignoring the
ecological functions of forests
Sustainable forest
management
(after 1998)
★Six large scale plantation and
rehabilitation projects
★Strict regulations on forest
Caused problems such as
depletion of forest resources, soil
erosion and desertification.
Especially, flood (Yangtze River
and Nenjiang River in 1998),
resources management
★National program: motivations
mechanism to conserve forest
resources (Li, 2014)
 Uneven-aged silviculture as one of the most conducive measures in improving
sustainable forest management has been paid a widespread attention recently
3
Outline of Presentation
Background
Purpose
Methods and Results
Summary
Acknowledgement
Application of uneven-aged silviculture in Northeast China
——A case study of larch plantations
4
Background
General information of forests in China
Area percentage
5.5%
12.4%
27.7%
2.4%
26.9%
Northeast
Southwest
Southeast
Northwest
Tropical
Other
26.2%
Total forest area: 208 million ha
Forest coverage: ca. 22%
ca. 1/3 in Northeast China
Plantation forests: 69 million ha (1/3 of national forest)
8th (2009–2013) National Forest Inventory Data (State Forestry Administration, 2014)
Background
Forests in Northeast China: Secondary forests (SF)
Playing important roles in conserving water
resource & timber production (providing 40%
of timber for the country)
Heavy timber harvest in the
past century 70% of them
were mixed broadleaved
secondary forests could not
provide timber as before
5
6
Background
Forests in Northeast China: Larch plantations (LP)
 A large area of secondary forests had been replaced by larch
(Larix spp.) plantations in order to meet increasing timber
demand since 1950’s
 Larch plantations: amount to 2 million ha, around 55% of
the planted forests in Northeast China
 Forming mosaic plantation/secondary forest landscapes
(Mason and Zhu, 2014)
Secondary Forest
Mosaic landscapes
Larch plantation
7
Background
Compared with the adjacent secondary forests, larch
plantations induced decrease of water conservation
capacity and runoff water acidification
 Water-holding capacity in larch plantations
decreased by 20%
 Runoff water pH<5.3 in larch plantations,
but pH>6.3 in secondary forests
(Xu et al., 2012)
Background
8
Compared with the adjacent secondary forests, larch
plantations induced soil fertility decline
Major reason caused the problems: mono-species
 Soil organic matter (SOM) of 40-year larch plantation decreased
composition of larch plantations  Soil fertility decline,
by 33.5% at 0-5 cm soil layer; by 42.6% at 5-15 cm soil layer
water conservation capacity decrease and acidification
(Yang et al., 2010)
Purposes
9
Try to change species composition by promoting the
regeneration of broadleaved species  to convert the
larch plantations into uneven-aged mixed forests
 For larch plantations surrounded by secondary forests:
Find out a suitable distribution pattern of larch plantations planted within
the secondary forest ecosystems; for improving regeneration potentials and
the possibility inducing LP into uneven-aged mixed forests
Determine the effects of thinning trials on natural regeneration of
broadleaved species in larch plantations
 For larch plantations not surrounded by secondary forests:
Test the feasibility of introducing broadleaved species into the thinned
larch plantations by artificial assistance
10
Study site
Qingyuan Experimental Station of Forest Ecology, CAS
Shenyang

Precipitation:
810.9 mm

Mean T: 4.7℃

Max. T: 36.5℃

Min. T: -37.6℃

Frost-free P: 130
days

Growing season:
late Apr-late Sep
Experimental forests: 1350 ha, composed of mixed broadleaved
secondary forests and larch plantations; common and typical in Northeast
11
Experiment forests
Major forest types in Qingyuan Station
Mixed broadleaved
Secondary Forests
 Secondary forest
 Mosaic patterns
 Larch plantation
(Not surrounded by
SF, out of the station)
Larch plantation
Larch plantation
surrounded by
secondary forest
Larch
plantation
Secondar
y forest
Methods—Effects of two typical distribution patterns
12
of LP on seed, seedling and sapling banks
Larch plantations surrounded by secondary forests
—two distribution patterns of larch plantations within secondary forests
Secondary forest
Sample
belt
Sample
point
 The Contour Type (CT): SF and LP locating at
the same slope position/aspect side by side
 The Up-Down Type (UDT): LP locating at the
down slope of adjacent SF in the same aspect
 Survey plots: 4-paired stands
Up-Down Pattern
Contour
Pattern
Larch plantation
Secondary forest
Sample
belt
Larch plantation
Sample
point
Methods—Effects of two typical distribution patterns
13
of LP on seed, seedling and sapling banks
Transects and quadrats setting
Transects
Transects
Sampling points
32 m
SF
32 m 16 m
SF
8m
4 m 2 m 0 m2 m 4 m 8 m 16 m 32 m
SF/LP
LP
boundary
Contour Type (CT)
 3 transects, each separated by 10m
 11 sampling points, at intervals of 2,
4, 8, 16 and 32 m (1 m2)
 132 sampling quadrats (1 m2)
16 m
Sampling
points
8m
4m
2m
SF/LP
0m
boundary
2m
4m
8m
16 m
LP
32 m
Up-Down Type (UDT)
Methods—Effects of two typical distribution patterns
14
of LP on seed, seedling and sapling banks
 Litter cover and
depth, vegetation
cover, measured at
more than nine
random points in
each sample plot
 Canopy openness,
estimated in each
month of growing
season at the
sample plots
15
Results—Effects of two typical distribution patterns
of LP on seed, seedling and sapling banks
Seed density for all tree species in soil
3000
2500
2000
-2-2
of seeds m
Number
种子库密度(粒
m )
-2
-2
of seeds
Number
种子库密度
(粒 m
m )
2500
1500
1000
2
500
y = -15.013x + 180.27x + 506.78
2
R = 0.1936
0
0
SF
32
1 16
2 83
4
25
06
27
Boundary
部位
Positions
2000
1500
1000
R2 = 0.694
0
0
10 32
11 12
48 89 16
LP
The Contour Type stands
varied as a quadratic curve
from SF to LP, and peaked
at the boundary of SF/LP
y = 152.18x + 665.83
500
SF
132 216 38
44
52
60
27
Boundary
部位
Positions
48
10 11 12
89 16
32
LP
The Up-Down Type stands
increased linearly from SF
to LP; More suitable for
seed invasion
16
Results—Effects of two typical distribution patterns
of LP on seed, seedling and sapling banks
Seed density for specific tree species in soil--Fraxinus
rhynchophylla
1800
1400
-2
种子库密度(粒
) -2
of seedsm m
Number
1600
500
-2
种子库密度(粒
of seedsmm) -2
Number
600
400
300
200
y = -111.28Ln(x) + 231.4
2
R = 0.517
100
0
0
SF
32
1 16
2
83
44
25
06
27
Boundary
部位
Positions
48
1200
1000
y = 18.526x2 - 153.02x + 524.61
800
R2 = 0.5004
600
400
200
10 32
11 12
89 16
LP
The Contour Type stands
declined logarithmically
from SF to LP, and seeds
only appeared at 4m in LP
0
0
SF
1 16
2 83
32
44
25 06
10 32
11 12
27 48 89 16
Boundary
部位
Positions
LP
The Up-Down Type stands
increased as a quadratic
curve from SF to LP
17
Results—Effects of two typical distribution patterns
of LP on seed, seedling and sapling banks
Seed density for specific tree species in soil--Acer mono
600
140
y = -0.3029x + 3.1621x + 25.673
120
500
R2 = 0.0112
种子库密度(粒
of seeds mm-2)-2
Number
种子库密度(粒
of seedsm-2m) -2
Number
2
100
80
60
40
20
0
0
SF
32
1 16
2
83
44
25
06
10 32
11 12
27 48 89 16
Boundary
部位
Positions
LP
The Contour Type stands
no significant changes from
SF to LP
y = 6.1334x2 - 33.635x + 79.144
R2 = 0.7968
400
300
200
100
0
0
SF
132 216 38
44
52
60
72
Boundary
部位
Positions
48
10 32
11 12
89 16
LP
The Up-Down Type stands
increased as a quadratic
curve from SF to LP
18
Results—Effects of two typical distribution patterns
of LP on seed, seedling and sapling banks
-2-2
55
Number
Number
of
saplings
saplings
m
m-2-2mm
saplings
saplings
of
ofof
Number
Number
Number
Number
of
seedlings
seedlings
m
m-2-2mm
seedlings
seedlings
of
ofof
Number
Number
-2-2
Seedling/sapling density for all species in UDT stands
44
3
22
1
1
0
0
SF
SF
1 32 216 38 44
1 32 216
38
25 06 2 7 4
Boundary
44 25 06 2 7 4
8 8 916 1032 11
8 8 916LP
1032 11
Boundary
Positions
Positions
LP
Positions
Positions
12
12
10
10
y = -0.35x + 5.55
2
R = 0.40
8
6
44
2
2
0
0
SF
SF
1 32 216 38
1 32 216
38
44
52 06 27
Boundary
44 52 06 27
Boundary
Positions
Positions
Positions
Positions
4
4
8
8
8
8
9 16 1032 11
1032 11
9 16LP
LP
Both seedlings and saplings of broadleaved species established in
the larch plantation  formed uneven aged larch-broadleaved
forests naturally
19
Results—Effects of two typical distribution patterns
of LP on seed, seedling and sapling banks
Number of seedlings/saplings m
-2
Relationships between seed/seedling/sapling densities
and canopy openness in Up-Down Type stands
10
9
8
7
6
5
4
3
2
1
0
y = -0.39x + 20.84
R2 = 0.12, P = 0.30
37
38
39
40
41
42
43
Canopy openess (%)
Canopy openness is the key factor in affecting
regeneration of broadleaved species in larch plantations
Results—Effects of two typical distribution patterns
20
of LP on seed, seedling and sapling banks
From the view of improving regeneration potential
and inducing larch plantations into the larchbroadleaved forests, the pattern of Up (SF)-andDown (LP) may be more feasible for seed invasion
and seedling or sapling establishment
Problem: How to promote the regeneration of
broadleaved species in larch plantations for Contour
Type stands? Thinning, the most important measure, has been
applied in improving the regeneration… we examined the effects of
thinning on the regeneration of broadleaved species in the larch
plantations
Methods—Effects of thinning on forming uneven aged
21
larch-broadleaved forests
Larch plantations surrounded by secondary forests
—two thinned stands of larch plantations (data: before/after thinning)
Regime A: Larch plantation was planted in 1965, thinned (10, 20,
30, & 50%) in 2004 with random thinning patterns
Thinning Stem density Basal area Canopy
Number of
intensity (trees ha-1) (m2 ha-1) openness (%) plots
30%
1620/1029
34.0/28.1
/23.5
Plots A1-A2
50%
1920/961
41.8/25.9
/34.0
Plots A3-A5
Regime A (2004 thinned larch stand) : to test
the effect of recent thinning on emergence and
survival of broadleaved species. Species number
and seedling density of all regenerated
broadleaved species were investigated soon after
thinning in 2004 & 2005
Methods—Effects of thinning on forming uneven aged
22
larch-broadleaved forests
Regime B: Larch plantation was planted in 1960, thinned in 1994
with random thinning patterns (20, 30, 40 & 60%)
Thinning Stem density Basal area Canopy
Number of
intensity (trees ha-1) (m2 ha-1) openness (%) plots
40%
1513/925
17.2/38.8
/14.2
Plots B1-B2
60%
1546/663
19.6/35.0
/16.8
Plots B3-B4
Regime B (1994 thinned larch stand): to
confirm the effect of thinning on establishment
of broadleaved species after 10 years of thinning.
Seedlings (5-50 cm) and saplings (50-500 cm) of
all broadleaved species were recorded in 2005.
The sapling height and base diameter were
measured in 2005
Methods—Effects of thinning on forming uneven aged
23
larch-broadleaved forests
Broadleaved species regeneration in 2004 thinned
stands: species number and seedling density
 Number of broadleaved species: 15
species, with abundant species of F.
rhynchophylla, A. mono,
Phellodendron amurense, Cornus
controversa
 Seedling density of broadleaved
species: 3-11 seedlings m-2
 Seedling density in 2005 > in 2004
 More seedlings in 50% than in 30%
(surveyed in 2004 and 2005)
Results—Effects of thinning on forming uneven aged
24
larch-broadleaved forests
Regeneration establishment in 1994 thinned stands
 Number of regenerated
broadleaved species: 10 with
abundant species of A. mono, F.
rhynchophylla, F. mandshurica
and Quercus mongolica etc.
 Density of regenerated
broadleaved species: 1-8
seedlings per m2, 2-7 saplings
per 10 m2
 Seedling density: 40% > 60%,
Sapling density : 60% > 40%
Seedlings: 5–50 cm in height
Saplings: 50–500 cm in height
(surveyed in 2005)
Results—Effects of thinning on forming uneven aged
25
larch-broadleaved forests
Sapling growth in 1994 thinned stands (surveyed in 2005)
 Basal diameter and height of saplings in 60% were higher than
those in 40%, but they both established.
 The regeneration of broadleaved species was successful in 40%
and 60% thinning treatments after 11 years.
Results—Effects of thinning on forming uneven aged
larch-broadleaved forests
For larch plantations surrounded by secondary
forests, it may be feasible to develop uneven-aged
larch-broadleaved forests through thinning; the
thinning intensity should be large enough to satisfy
the survival and growth of seedlings or saplings
For larch plantations not surrounded by secondary
forests, whether can we promote the regeneration of
broadleaved species by artificial assistance?
26
Methods—Seed germination & seedling growth of
27
introduced broadleaved species in LP stands
Larch plantations not surrounded by secondary forests
—nine stands in a thinned larch plantation (10.3 ha, 20yrs) in 2011
CK
50%
25%
100%
25%
100%
50%
50%
CK
Thinning intensity
Stem density (trees ha-1)
Canopy openness
0 (CK)
25%
50%
100%
900
675
450
0
11±1%
21±1%
25±1%
100%
Dominant broadleaved species: Fraxinus mandshurica & Juglans mandshurica
Methods—Seed germination & seedling growth of
28
introduced broadleaved species in LP stands
Seed germination in thinned larch plantations not
surrounded by secondary forests (Oct 2011-Oct 2013)
Treatments: Fraxinus & Juglans seeds were collected and
directly seeded at five positions by simulating the states of seeds
after falling off in thinned stands in autumn (2011)
pressed halfway into the
soil (ST)
under 1cm soil with on top of the
4cm litter cover
(LS1)
litter cover
(LT)
under 1cm soil beneath the
without litter
litter of 4 cm
cover (S1)
depth (LS)
 Germination, seedling emergence and survival were monitored
after seeding (50 seeds×3 replications)
Results—Seed germination & seedling growth of
29
introduced broadleaved species in LP stands
CK
ST
LT
40
LS
S1
Seed germination (%)
50
LS1
50
30
20
20
10
10
0
50
50%
40
30
60
 Highest:
60
60
0
Jun
25%
Aug
Month
40
30
20
10
Sep 60
Seed germination (%)
Seed
germination
(%)
(%) Seed
rate
germination
germination
Seed
Seed
germinationrate
(%) (%)
Seed germination—J. mandshurica
0
50
Jun
100%
Aug
Month
Sep
40
30
 Lowest:
20
10
0
Jun
Aug
Month
Sep
25% & 50%
thinned
stands;
S1/LS1:
19.2±2.2%/
21.3±2.2%
Jun
Aug
Month
Sep
ST: pressed half-way into soil; LT: on top of litter; LS: beneath litter; S1:
under soil without litter cover; LS1: under soil with litter coverage
100% & CK;
LT:
5.4±2.2%
Results—Seed germination & seedling growth of
30
introduced broadleaved species in LP stands
CK
ST
LT
60
40
20
0
80
60
Jun
50%
Aug
Month
40
20
0
Jun
Aug
Month
LS
S1
80
LS1
Seed germination rate (%)
80
Seed germination rate (%)
(%)
germination
Seedrate
Seedrate
germination
rate (%)
Seed germination
(%)
Seed germination—F. mandshurica
Sep
Sep
 Highest: 50%
25%
60
40
20
0
80
Jun
100%
60
Aug
Month
Sep
thinned stands,
next CK, 25%;
S1/LS1:
34.7±2.0%/
37.7±2.3%
 Lowest: 100%
40
20
0
Jun
Aug
Month
Sep
ST: pressed half-way into soil; LT: on top of litter; LS: beneath litter;
S1: under soil without litter cover; LS1: under soil with litter coverage
(17.7±2.5%),
ST/LT:
20.3±2.3%/
22.0±2.4%
31
Results—Seed germination & seedling growth of
introduced broadleaved species in LP stands
Seedling emergence and survival
F. mandshurica
20
ST
LT
LS
S1
LS1
Total
15
10
5
0
0
25
50
Thinning intensity (%)
100
Seedling survival rate (%)
Seedling survival rate (%)
J. mandshurica
35
30
ST
LT
LS
S1
LS1
Total
25
20
15
10
5
0
0
25
50
Thining intensity (%)
100
 J. mandshurica: lower survival rates in general, less than 4%; Control
plot exhibited the lowest survival; The highest: 25%/S1 10.7%,
50%/LS1: 10.3%
 F. mandshurica: 14% survival in average; The highest: 50%/S1 23%
Results—Seed germination & seedling growth of
32
introduced broadleaved species in LP stands
For larch plantations not surrounded by secondary
forests, 25% (675 stems per hectare) and 50%
thinning (450 stems per hectare), and under soil
seeding are necessary for the germination and
emergence of Juglans and Fraxinus. But, the survival
of the seedlings after germination was very poor.
Problem: Is it possible to plant the seedlings of
broadleaved species in the thinned larch plantations
to promote the regeneration of broadleaved species?
Methods—Seed germination & seedling growth of
33
introduced broadleaved species in LP stands
Planting seedlings in thinned larch plantations not
surrounded by secondary forests (May-Oct 2013)
Treatments: 1-year & 2-year FM & JM seedlings were planted
randomly in each stand in spring (50 seedlings×3 replications)
0.5cm
1-yr-old
2-yr-old
J. Mandshurica
0.5cm
F. mandshurica
 Seedling survival was monitored at interval of one month from May to Oct.
 Seedling harvest was conducted in autumn. Height, collar diameter, root
length, biomass, leaf δ13C, non-structural carbon content were measured
Results—Seed germination & seedling growth of
34
introduced broadleaved species in LP stands
Seedling survival
 Lowest: at 100%
thinned stands
(33% for F.
mandshurica;
58% for J.
mandshurica)
Seedling survival rate (%)
100
80
60
40
20
0
0
25
50
Thinning intensity (%)
100
 Highest: CK,
25% & 50%
thinning stands
(45% for F.
mandshurica,
86% for J.
mandshurica)
35
Results—Seed germination & seedling growth of
introduced broadleaved species in LP stands
Soil water content (%)
30
25
May
Jun
Sep
Light
regime at
100 cm
mean
20
15
10
5
0
0
25
50
100
Thinning intensity (%)
Soil water
content in
0-20 cm
Photosynthetic active radiation
-2 -1
( μmol m s )
Water use efficiency
500
400
May
Jun
Sep
mean
300
200
100
0
0
25
50
100
Thinning intensity (%)
-27
13
δ C (‰)
δ C (‰)
-28
-29
-30
-31
1-yrold
J. Mandshurica
F. mandschurica
δ13 C (‰) 13
-32
-33
-27
-28
-29
-30
0
2-yrold
25%
50%
Thinning intensity
100%
-31
-32
-33
0
25%
50%
Thinning intensity
100%
 It may be caused by the water stress
because of lower soil water contents and
higher light intensities in the clearcutting plot
 δ13C of leaves: carbon isotope was the
highest in seedling leaves of clear-cutting
plot, which confirmed the deduction
36
Results—Seed germination & seedling growth of
introduced broadleaved species in LP stands
Seedling growth
Seedling basal diameter (cm)
Seedling height (cm)
60
50
40
30
20
10
0
0
25
50
Thinning intensity (%)
100
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
0
25
50
Thinning intensity (%)
 Height/diameter: no significant differences between thinning
intensities for both aged seedlings (short observed period)
 Growth trend: diameter growth of both species showed the
increasing trend with the increase of thinning intensities
100
Results—Seed germination & seedling growth of
37
introduced broadleaved species in LP stands
 For the larch plantations not surrounded by
secondary forests, artificial assistance (thinning, and
planting seedlings of dominant broadleaved species)
has potential to improve the regeneration of
broadleaved species in the larch plantations.
Further observations are being carried out…
Summary
38
 For larch plantations (LP) surrounded by secondary forests
(SF), the natural regeneration of broadleaved species have
established with Up secondary forest and Down larch
plantation pattern. Therefore, it is feasible for the Up-Down
pattern larch plantations to develop the uneven-aged larchbroadleaved forests
 For LP surrounded by SF, when they located side by side, it is
likely to form an uneven-aged larch-broadleaved forest by
thinning with appropriate canopy openness
 For LP not surrounded by SF, artificial assistance, including
thinning larch plantations and planting broadleaved species
seedlings, has potential to promote the regeneration of
broadleaved species in the larch plantations. But, the further
observations are needed
Questions & Comments
Qingyuan Experimental Station of Forest Ecology, CAS
Acknowledgement
 National Basic Research Program of China (973) (2012CB416900) & National Natural
Science Foundation of China (31330016) provided the financial support
 The member in Research Group of Ecology & Management of Secondary Forests,
IAE, CAS gave the helps in field observations and valuable suggestions
Thank you for your attention!
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40
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