130 -
125 |
120 +
past
L10 +
105 |
100 -
095 :
AWMPFD
1986 2000 2006
0 Closed forest (3 Shrub C) Open forest C1 Other forest C) Total
Figure 3. Landscape metrics of forest
4.3 Forest Change Trajectory
All found trajectories were cdassified into three classes, namely,
unchanged, human-induced change and natural changes (Table
2). The unchanged class indicates that forest cover was found
on the same analyzed pixel over the past 20 years. The human-
induced change class includes decisive changes due to human
activities such as cultivation, logging, reforestation and
construction. The representative trajectories of this class include
F-C-C, F-F-C, F-F-B and C-C-F. The conversion between forest
and other natural cover types are defined as natural changed
trajectories in the study area during 1986-2006. Examples of
trajectories of this class are F-F-G, F-G-G, G-G-F and G-F-F.
Level 1 classes Level 2 classes Trajectotie Am
S (ha)
Unchanged Stable forestland F-F-F 33942.37
Natural change Changed o F-F-G 529.18
grassland
F-G-G 11.71
G-F-G 1.12
W-F-G 0.16
Changed to
forestland GEF 737
W-F-F 0.72
U-U-F 2.13
U-F-F 0.41
Changed to F-W-W 0.92
water area
Subtotal 553.72
Human-induced Changed to F-C-C 72.28
change cropland
F-F-C 674.9
C-F-C 15
G-F-C 1.36
Changed to
forestland CF 21.09
C-C-F 4.43
B-F-F 0.1
B-F-F 0.1
Changed to C-F-G 114
grassland
Changed to
built-up land EFH 10.00
F-B-B 0.78
F-C-B 0.34
C-F-B 0.08
Changed to F-U-U 6.56
unused land
F-F-U 105.24
Subtotal 938.99
Table 2. Forest change trajectories and area statistics (km?)
During the 20-year study period, the unchanged area of forest
took up 78.8% of the total area. Human-induced changes in
forest occupied 2.2%, while natural change area 1.3%. The rest
of the total area was occupied by the changes between other
land use types. For the natural change area, the trajectory of F-
F-G obviously dominated, constituting 95.6%. Cropland
converted from forest occupied 79.6% of total area of the
human-induced change trajectories. Due to clear-cutting and
selective logging, 111.8 km? forest was changed to unused land,
taking up 11.9% of total human-induced changed area. About
5.3% of total human-induced changed area was lost to built-up
land. Overall, the total area of human-induced change is 1.7
times than that of natural change in the study area during past
20 years.
5. DISCUSSION AND CONCLUSION
Increases of population and intensive agriculture generally have
been regarded as main causes of land use and land cover
changes (Verburg et al. 1999). Some studies offer statistical
evidence supporting the claim that population growth drives or
strongly contributes to forest clearance (Allen and Barnes 1985).
During past two decades, the total population of the study area
increased by 12% from 1.95 million to 2.18 million. The
increased population and consequent demand for grain have
caused the increased reclamation of farmland in the study areas
in parallel to the loss of forestland. Rapid economic
development was partly responsible for land use changes in this
study area. Gross domestic product (GDP) of the Yanbian
prefecture increased dramatically, indicating a boost in
economy and accelerated infrastructure construction. The
steady population growth and economic boost coincided with a
continuous increase in its developed land area.
During the early years of the People’s Republic of China, in
order to meet the exigent demands of economic construction
and social development, the primary goal of forestry in
Northeast China was that of timber production (Yu et al. 2011).
Excessive harvesting of timber was encouraged for a long
period (Zhou 2006). More than 20 state-owned forestry
enterprises were established on the Changbai Mountains. Since
1978, forestry was to be guided by universal forest protection,
extensive reforestation and afforestation efforts, a combination
of cutting and planting, and sustainable utilization. However, in
conjunction with national economic reforms and the broadening
of international relations, excessive logging and neglected
cultivation of forests which together nearly exhausted
exploitable forest reserves in the region (Zhang et al 2000). The
‘food first’ agricultural policy exerted the longest influence
since the People’s Republic of China founded in 1949(Gao et al.
2006). Large area of natural forest in Northeast China was
cleared for farming in the past decades. There was a continuous
decrease in cropland area between 1986 and 2001, which could
be related to the abandonment of low quality croplands on steep
terrace and rapid expansion of construction land. Since 2002,
cropland area saw an upward trend partially driven by the
policy of dynamic equilibrium of the total cultivated land.
The policies of “Grain for Green” (reversing cultivated land to
forestland and grassland), the “Natural Forest Conversion
Program” (NFCP) and “Construction of an Ecological
Province” projects were formally launched in the nation since
1998. Timber harvesting levels in Northeast China have
decreased, but forest area and stocking levels have slowly
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