240
above four formula comprehensive can comprehensive describe
a single land use types of spatial dynamics.
3. THE PROCESSES OF LAND USE / COVER
CHANGE AND TRENDS IN THREE GORGES
RESERVOIR AREA AT NEARLY 30 YEARS
3.1 The range of area change of land use
Formula 1 indicates the range of six land use types on the
Three Gorges reservoir in 1972 -1986. 1986-2000 and 1972-
2000 periods were calculated (Table 1).
in increasingly, at -0.91%, -0.70% Reforestation been checked
to a certain extent. Grassland area has experienced first
decreased and then increased the process, the range of area
change of-1.42%, 3.59%; building area continued to increase;
unused land area continued to decline, and its range of
reduction growing. Water area continued to decline, the range
of reduction is -1.38%, -1.19%. Through the above, the area of
woodland and grassland view of the range of changes, returning
farmland to forest and pastures are beginning to bear fruit.
3.2 A single land use / cover types of dynamic change
1972-1986
the range of
area change
1986-2000
the range of
area change
1972-2000
the range of
area change
Farmland
34204.60
1.36%
-20234.70
-0.79%
13969.90
0.55%
Woodland
-27241.10
-0.91%
-20821.70
-0.70%
-48062.80
-1.61%
Grassland
-9453.30
-1.42%
23675.75
3.59%
14222.45
2.13%
Construction sites
3678.80
10.44%
18525.10
47.59%
22203.90
63.00%
Unused land
-201.00
-2.37%
-303.15
-3.66%
-504.15
-5.94%
Waters
-988.00
-1.38%
-841.30
-1.19%
-1829.30
-2.56%
Table 1. Area net change of the land use/cover in the study area at different periodsin lately fifty years (units: hm )
The results showed that from 1972 to 2000 nearly 30 years of
time, the area of 6 land use types have occurred in different
degrees, the area of 3 land use types decreased, while others
increased. In the type whose area increased, the reduction of the
woodland area was the biggest, which is 48062.80 hm 2 ; the
reduction of water area was smaller than woodland, which
reduce 1829.30 hm 2 ; the area of unused land reduced 504.15
hm 2 ; In the type whose area decreased, construction is first,
which increased 22,203 hm 2 ; the area of lawn increased
14222.45 hm 2 ; the area of arable land increased 13969.90 hm 2 .
In the reservoir of all types, in the past 30 years, at the
magnitude of changes of area, the change of construction was
the largest, which was 63.00%; unused land was Second, which
was 5.94%; the range of area change of water, grassland,
woodland and farmland were also reached 2.56%, 2.13%,
1.61% and 0.55%.
From the changes of the area of all types in 1972 -1986 and
1986-2000, farmland area has increased prior to the reduction
process, the range of area change were 1.36%, 0.79%;
woodland area continued to decline, but the range of reduction
According to the formula 2, 3, 4, 5 calculating the Three
Gorges reservoir area nearly 30 years of all types of dynamic
change indicators, calculated results are shown in table 2.
The results showed : ® output speed : 1972-1986, the area of
all types, the output speed is from the order of unused land,
grass, water, woodland, farmland, and construction sites; in
years 1986-2000 will become the order of unused land,
grassland, farmland, forest land, waters, building sites. On the
output speed of all types areas in two periods of comparison, in
addition to construction sites, other types of land use in 1986
and 2000 transfer rate was more than the fore periods. (2) output
speed : 1972-1986 years, to the speed of all types, from large
order to the small were construction land, farmland, grassland,
unused land, woodland, water; 1986-2000, the order of the rate
of all types were construction land, grassland, farmland, forest
land, waters, unused land. On the transfer of all types of speed
in two periods of change, output speed increased both. (D
integrated dynamic degree: in 1972-1986, the composite
dynamic degree of 6 land use types followed the order of
construction land, unused land, grassland, farmland, waters and
^"\t:he type
Indicatofs^^^
of change
the Period
Farmland
Woodland
Grassland
Construction sites
Unused land
Waters
Transferrate (%)
1972-1986
0.01
0.07
0.14
0.00
0.20
0.10
1986-2000
0.19
0.18
0.21
0.00
0.30
0.14
Output speed
1972-1986 íT
0.11
0.01
0.04
0.75
0.03
0.00
(%)
1986-2000
0.13
0.13
0.46
3.40
0.04
0.04
Integrated dynamic
1972-1986 ífi
0.11
0.08
0.18
0.75
0.22
0.10
degree (% )
1986-2000 íp
0.32
0.31
0.67
3.40
0.33
0.19
State index
1972-1986 íp
-0.86
0.83
0.56
-1.00
0.76
0.97
1986-2000
0.18
0.16
-0.38
-1.00
0.78
0.46
Table 2. The change indexes of the land use typein the study area at different periods
