Table 1. General description of the twelve artificial gaps created in December 2004 at Qingyuan Forest CERN, CAS.
Canopy gap Area (m2) Mean height of canopy trees surrounding gaps (m) Slope (o) Aspect (o) Elevation (m)
L1 513.9 19 17 170 650
L2 621.1 17 23 150 670
M1 267.3 17 24 140 640
M2 174.1 16 20 155 690
M3 307.9 16 25 145 673
M4 321.2 17 25 160 681
S1 83.9 16 20 170 630
S2 75.5 17 22 140 640
S3 68.4 16 23 170 675
S4 86.4 18 20 150 634
S5 113.8 17 26 145 655
S6 124.5 16 24 165 669
L1 – L2 = large gaps
M1 – M4 = middle gaps
S1 – S6 = small gaps
1

Fig. 1. The schematic of the experimental design: (a) canopy gap and (b) control plot.

2

Fig. 2. Mean (with standard error) size of small gaps (S), middle gaps (M), and large gaps (L) as a function of time after gap creation in December 2004.

Table 2. Gap closure equations of lateral extension growth for small gaps (S), middle gaps (M) and large gaps (L).
Gap type Canopy gap size (m2)
S y = 0.7333x2 – 16.765x + 106.59   (n = 42)
M y = 1.3584x2 – 35.521x + 301.61   (n = 28)
L y = 1.5937x2 – 50.018x + 615.56   (n = 12)
x = gap age
y = gap size
n = number of hemispherical photographs
Table 3. Mean (with standard error) closure rates and lateral extension growth rates of small gaps (S), middle gaps (M) and large gaps (L) for seven (six for large gaps) years.
Gap type Closure rate (m2 a–1) Percentage of closure rate (% a–1) Lateral growth rate (cm a–1)
S 11.2 ± 1.5 12.2 ± 1.6 44.4 ± 3.3
M 24.5 ± 2.3 9.2 ± 0.9 51.8 ± 3.6
L 38.9 ± 2.4 6.9 ± 0.4 52.0 ± 3.7
3

Fig. 3. Correlation between canopy openness and canopy gap size.

4

Fig. 4. Mean (with standard error) variation of canopy openness in the forest understory (C), small gaps (S), middle gaps (M), and large gaps (L) after gap creation in December 2004.

5

Fig. 5. Density (with standard error) and volume (with standard error) of woody species regeneration in the forest understory (C), small gaps (S), middle gaps (M), and large gaps (L) in 2006 and 2011 after gap creation (December 2004). Bars with different letters are significantly different (p < 0.05).

Table 4. Density of regenerated woody species in the forest understory (C), small gaps (S), middle gaps (M), and large gaps (L) in 2006 and 2011.
Species Shade tolerance Density (stems m–2)
2006 2011
C S M L C S M L
Betula costata Trautv. shade-intolerant 0.13 0.32 0.60 0.99 0.10 0.11 0.25 0.77
Fraxinus mandshurica Rupr. shade-intolerant 0.32 0.99 1.09 1.46 0.46 0.46 0.47 1.02
Fraxinus rhynchophylla shade-intolerant 0.77 1.96 2.48 3.66 0.58 0.73 0.75 1.58
Juglans mandshurica Maxim. shade-intolerant 0.02 0.01 0.09 0.07 0.01 0.00 0.08 0.06
Phellodendron amurense Rupr. shade-intolerant 0.09 0.51 0.67 0.83 0.09 0.20 0.23 0.64
Populus davidiana Dode shade-intolerant 0.23 0.67 1.70 2.30 0.15 0.14 0.58 1.36
Quercus mongolica shade-intolerant 0.98 1.08 1.43 1.82 0.76 0.34 0.71 1.02
Alnus sibirica (Spach) Turcz. intermediate 0.24 0.43 0.61 0.20 0.30 0.16 0.29 0.06
Aralia elata (Miq.) Seem. intermediate 0.00 0.58 0.54 0.79 0.00 0.13 0.21 0.31
Acer mono shade-tolerant 0.43 1.17 1.20 1.49 0.61 0.56 0.80 0.77
Acer pseudo-sieboldianum shade-tolerant 0.20 0.97 0.44 0.93 0.46 0.68 0.20 0.43
Acer ukurunduense Trautv. shade-tolerant 0.06 0.67 0.41 0.00 0.10 0.59 0.12 0.00
Corylus mandshurica Maxim. shade-tolerant 0.11 0.92 0.21 0.00 0.14 0.44 0.20 0.00
Tilia amurensis Rupr. shade-tolerant 0.00 0.22 0.42 0.51 0.00 0.10 0.20 0.40
Ulmus laciniata shade-tolerant 0.00 0.61 0.14 0.00 0.10 0.25 0.10 0.00
Table 5. Volume of regenerated woody species in the forest understory (C), small gaps (S), middle gaps (M), and large gaps (L) in 2006 and 2011.
Species Shade tolerance Volume (m3 m–2)
2006 2011
C S M L C S M L
Betula costata shade-intolerant 0.002 0.001 0.002 0.004 0.003 0.003 0.007 0.018
Fraxinus mandshurica shade-intolerant 0.004 0.004 0.004 0.007 0.007 0.012 0.014 0.039
Fraxinus rhynchophylla shade-intolerant 0.004 0.003 0.004 0.007 0.006 0.006 0.006 0.014
Juglans mandshurica shade-intolerant 0.003 0.004 0.007 0.015 0.007 0.006 0.013 0.034
Phellodendron amurense shade-intolerant 0.002 0.003 0.005 0.012 0.003 0.003 0.008 0.024
Populus davidiana shade-intolerant 0.003 0.002 0.003 0.007 0.003 0.003 0.007 0.019
Quercus mongolica shade-intolerant 0.002 0.001 0.002 0.005 0.003 0.003 0.007 0.016
Alnus sibirica Intermediate 0.006 0.004 0.005 0.012 0.008 0.010 0.012 0.030
Aralia elata Intermediate 0.000 0.004 0.006 0.015 0.000 0.009 0.018 0.039
Acer mono shade-tolerant 0.005 0.003 0.002 0.006 0.007 0.007 0.007 0.018
Acer pseudo-sieboldianum shade-tolerant 0.003 0.003 0.002 0.005 0.007 0.008 0.008 0.017
Acer ukurunduense shade-tolerant 0.003 0.003 0.002 0.000 0.007 0.007 0.007 0.000
Corylus mandshurica shade-tolerant 0.004 0.004 0.004 0.000 0.007 0.010 0.012 0.000
Tilia amurensis shade-tolerant 0.000 0.001 0.002 0.006 0.000 0.004 0.011 0.028
Ulmus laciniata shade-tolerant 0.000 0.003 0.004 0.000 0.006 0.010 0.011 0.000