3.3 The land use of alluvial fans
The Table 1 shows the area proportion of different land use types of
alluvial fans in LRB. The Rlaf of grassland is
the largest with 68.70% in all land-use types. TheRlaf of impervious area covered by artificial
buildings is only 4.52%, but Rllrb is 9.18%.
The Rlaf and Rllrb of
cropland had similar regulation with impervious area. TheRlaf of cropland is just 2.16%, butRllrb is 18.98% of the cropland area of LRB.
Those illustrate the great contribution of alluvial fans about providing
grass for livestock and food and residential place for human. TheRlaf and Rllrb of forest,
shrubland, wetland, and water body are far lower than cropland,
impervious area and bare land. The snow/ice almost can be ignored in all
types of land use.
The spatial distribution of land-use types of alluvial fans is showed in
Fig7. The grassland is the most in all land use types, especially in
Damshung cunty. The cropland is mainly distributed in the south of LRB,
including Taktse, Tolung Dechen, Chushur and the south part of Lhundup
county. The distribution of imperious area is the same with cropland,
including Taktse, Chenguan and Tolung Dechen. The bare land is mainly
distributed in Damshung and Chushur county. Combining Google earth, the
bare land of alluvial fans is covered by sand where is hardly grow
vegetation.
There are only 3 kinds of alluvial fans which area are occupied more
than 50% by one land-use type (A50%,), including
A50%grassland, A50%impervious area,
and A50%cropland (Fig8.). The
A50%grassland exist all counties with 665 and area of
903.17 km². The A50%impervious area only exist in
Tolung Dechen, Chenguan, and Taktsc. There is only an
A50%grassland in LRB with the area of 0.07 km². There
are 6 kinds of A50% which area are occupied more than
30% another land-use type (A50%A30%), and 4 kinds are about
A50%grassland (Fig9.) the quantity of
A50% A30% is far less than
A50%. A50%grasslandA30%bare land is the most in A50%A30%, and distribute all counties except ChuChur. The
A50%impervious area A30%bare land and
the A50%impervious area A30%grasslanddistribute in Tolung Dechen and Chenguan.