Vegetation-Erosion Dynamics - River Dynamics and Integrated River Management - page 94

Fig. 2.40 Geographical locations of the 13 small watersheds in the Loess Plateau used to evaluate the vegetation-
erocess dynamics model

Table 2.2 The four parameters in the vegetation-erosion differential equations and climatic, topographical, and soil
c haracteristics of 13 small watershed on the Loess Plateau

f
(t/(km 2 . yr 2 )
Chuanzhang Zhunger 400.0 7.2 0.172 0.046 0.0010 1.90 0.033 450
Nanqugou Hequ 462.9 6.8 0.708 0.044 0.0010 1.30 0.030 450
Zhuanyaogou Hequ 447.5 8.8 0.695 0.042 0.0015 1.30 0.025 450
Yulingou Mizhi 451.6 8.5 0.780 0.038 0.0015 1.40 0.021 470
Wangmaogou Suide 513.0 10.0 0.836 0.036 0.0020 1.50 0.015 510
Zhifanggou Ansai 549.1 8.8 0.680 0.034 0.0022 1.70 0.014 500
Wangjiagou Lishi 506.1 8.8 0.412 0.032 0.0020 1.75 0.020 470
Anjiagou Dingxi 427.4 6.3 0.398 0.022 0.0010 1.70 0.014 480
Huangjiaercha Xiji 402.2 5.8 0.323 0.029 0.0010 2.00 0.015 480
Wangdonggou Changwu 584.1 8.3 0.462 0.02 0.0020 1.80 0.019 380
Nihegou Chunhua 600.6 9.5 0.368 0.014 0.0030 1.50 0.012 350
Zaozigou Qianxian 590.0 10.9 0.202 0.012 0.0045 1.10 0.011 300
Luergou Tianshui 574.1 11.0 0.661 0.011 0.0040 1.32 0.014 400
Note: P is the annual precipitation; T is the annual average temperature; s is the average slope; and D 50 is the median
diameter of the soil.

T
( ć

a
(1/yr)

c
(10 -6 km 2 /t)

b
(1/yr)

Watershed County P (mm) s

50 (mm)

Table 2.2 shows that the value of a increases with the precipitation and temperature. In general the
existing vegetation favors vegetation development and parameter a is positive due to the effect of canopy
cover providing shade and propagation of mature vegetation. But this effect is limited by low precipitation
and low temperature. In arid and semi-arid areas there is not enough water for vegetation development,
the parameter a is small. In cold areas plants grow very slowly and the parameter a is small. Soil and
topography do not affect the value of a obviously. parameter c represents the area of vegetation damaged
by soil erosion, or, vegetation-damage caused by one ton of soil erosion. The erosion layer on the Loess