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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