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2009 Vol.7 No.2
Published 2009-04-01
Articles
1
LIU Gan-；Lei-Ting-Wu-；Diao-Jun
Effects of initial soil water content and rainfall intensity on Loess infiltration capacity
The Run-off-on-out(ROOO) method was used to measure soil infiltrability in order to research the effects of rainfall intensity and soil water content on soil infiltrability compared with Double Ring(DR) method.The experiments involved 3 soil moisture contents(2.6%,10.4% and 19.5%) and 3 rainfall intensities (20,40 and 60 mm/h).Soil infiltrability measured by the ROOO method decreased with higher initial soil water content and rainfall intensity.However,the initial soil infiltrability obtained by DR method increased with higher soil water content,as well as the stable infiltrability decreased with higher soil water content.The soil infiltrability processes measured with the ROOO method give better fittings with Kostiakov,Horton and Philip infiltration models,than those measured with double-ring infiltrometer.Moreover,the Horton infiltration model gives the best fitting results comparing with other models.
2009 Vol. 7 (2): 1-6 [
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1982
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7
HONG Xiao-Yong-；Zheng-Fen-Chi-；Zhang-Xin-He
Effects of upslope runoff on detachment and transport processes on loessial hillslopes
Research on upslope runoff effects on downslope detachment and transport process may deepen the understanding of hillslope soil erosion process and mechnisems.An experimental system,consisted of water feeding installation and the tested box,was used to study upslope runoff effects on detachment and transport processes on loessial 15° hillslope under different rainfall intensities by using rainfall simulator.The results showed that the total sediment delivery with upslope runoff input was greater than that without upslope runoff input at 50,75,and 100 mm/h of rainfall intensities,i.e.,upslope runoff discharging into downslope caused additional sediment delivery(net sediment delivery).Sediment delivery was not a simply positive correlation with upslope runoff rate.Additional sediment delivery was small when low upslope runoff discharged into downslope.When increasing upslope runoff rate reached to 1.6 L/min,sediment delivery was remarkably increased with an increase of upslope runoff rate,and the increment range of sediment delivery increased with the increase of upslope runoff rate.But when increasing upslope runoff rate was greater than 3.2 L/min,the increment range of sediment delivery decreased with the increase of upslope runoff rate.After upslope runoff discharged into downslope section,sediment regime at downslope section was a domination of detachment-transport
2009 Vol. 7 (2): 7-11 [
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12
TAN Zhen-Hua-；Wang-Tie-Li-；Ma-Chun-Yan-；Liu-Dun-E-；Yuan-Yan
Simulated-rainfall experimental research on soil erosion processes on downslope segment of loess hillslope
In the process of water erosion,runoff and sediment yield vary with the different segments of a hillslope.Clarifying the mechanism of erosion processes can provide a scientific basis for soil and water conservation measures.In this study,erosion processes on downslope were investigated using two flumes with different lengths under simulated rainfall.Results showed that 1) downslope erosion intensity varied with rainfall process,rainfall intensity,and slope gradient,characterized by up-down fluctuations.2) Erosion intensity varying with rainfall process,slope,and rainfall intensity between different segments on the same slope was obviously different.3) Runoff from both of the upslope and the downslope and sediment on the upslope had impacts on erosion intensity on the downslope and the impacts could be well described with a linear equation,with the former contribution being 47.8 % and the latter,20.4%.It can be concluded that only observation and analysis of average erosion characteristics cover up the detailed erosion processes.Taking soil and water conservation measures to reduce flow concentration from upslope and increase rainfall infiltration can effectively control soil erosion on downslope.
2009 Vol. 7 (2): 12-17 [
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1713
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18
FU Su-Hua-；Liu-Bao-Yuan-；Lu-Bing-Jun-；Yuan-Ai-Ping-；Wang-Nan
Effect of soil conservation practice on runoff and sediment in upper reach of Guanting Reservoir
The benefits of runoff and sediment reduction and factor value for soil and water conservation measures were analyzed based on 58 rainfall events data(2001—2006) of fish pit(bare land),fish pit(Platycladus orientalis L.Franco),narrow terrace(bare land),narrow terrace(Castanea mollissima Blume) and tree pan(Castanea mollissima Blume).The results showed that the average benefits of runoff reduction of fish pit(bare land),fish pit(
Platycladus orientalis
L.Franco),narrow terrace(bare land),narrow terrace(
Castanea mollissima Blume
) and tree pan(
Castanea mollissima Blume
) were all more than 60%,and the corresponding annual benefits of sediment reduction were above 90%.The engineering measures factors for fish pit,narrow terrace and tree pan were 0.08,0.09 and 0.10,respectively.The biological measures factors for Platycladus orientalis L.Franco and
Castanea mollissima Blume
were 0.41 and 0.48,respectively.Rainfall amount had an important effect on benefit of runoff and sediment reduction and measures factors value.The results can be served as benefits evaluations of soil and water conservation and land resource management in upper reach of Guanting Reservoir.
2009 Vol. 7 (2): 18-23 [
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2238
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24
ZHANG Rui-Fang-；Wang-Xuan-；Fan-Hao-Meng-；Zhou-Li-Li-；Wu-Min-；Liu-Yan-Hua
Study on the regionalization of freeze-thaw zones in China and the erosion characteristics
In this paper,based on the comprehensive analysis of the impact factors of soil freezing and thawing,the impact of the temperature and precipitation of China's climatic and environmental conditions on the freeze-thaw function and freeze-thaw erosion was discussed,and the overall distribution of freeze-thaw zones in China was defined.Based on the existing relevant research results,we explored and refined the classification standards of soil freezing and thawing,thus further explored the distributional range of freeze-thaw zones in China,finally described the regularity and characteristics of distribution and the features of freeze-thaw function and freeze-thaw erosion in the freeze-thaw zones.The results may provide the guidance for control erosion in freeze-thaw zones in China.
2009 Vol. 7 (2): 24-28 [
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1991
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29
HU Jian-Zhong-；Du-Wen-Yan-；Guo-Hai-；Yan-Li-Jiang-；Liu-Li-Ying-；He-Jing-Liang-；Guo-Jian-Yang-；Jia-Bo
Female and male proportions of artificial Hippophae rhamnoedes ssp. sinensis forest in soft sandstone area
Hippophae rhamnoedes
ssp.
sinensis
is a very suitable shrub for afforestation in the northern China especially in the Loess Plateau,which has been planted for more than twenty years in China under the careful design and strong management.The ecologic and economic benefits of which have been achieved,and play a key role to increase farmer and enterprises' incomes.The sex ratio rule of dioecious species is very important for the rehabilitation with seabuckthorn in the soft sandstone area of the adjacent area of Shanxi,Shaanxi,and Inner Mongolia of China.Survey and statistics for 36 kinds of artificial sea-buckthorn stands show that the female ratio to male is 1∶2.6 as a whole,while the male quotient of young stand is very high with the highest of 10 times as high as that of female,and the female ratio to male is about 1∶2 or so for 5 to 8 year's old stands.The female ratio to male for alluvium,sand soil,and loess is 1∶2.2-2.4 whereas the ratio is 1∶3.4 for the forest in the soft sandstone site condition.Rigorous site conditions in the research area cause the more proportions of male plants.Economic or eco-economic types of
Hippophae rhamnoedes
ssp.sinensis forest or cash forest should be set up in good site conditions like the bottomland in wide valley for more economic benefits,while the ecological type of
Hippophae rhamnoedes
ssp.sinensis forest in bad site conditions for ecological benefits consideration.
2009 Vol. 7 (2): 29-34 [
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35
DONG Chi-Li-；Zheng-Fen-Chi
Fractal characteristics of soil particles in the Hilly-gully Regions of the Loess Plateau,North of Shaanxi,China
The particle size distributions(PSD) of forty soil samples from the ten kinds of land use and four soil profiles were presented.PSD were measured by Malvern Mastersizer 2000 and analyzed by applying fractal geometry method.Results indicate that there is no significant variation in the fractal dimensions(
D
) of the soil(between 2.230 and 2.521) due to the same soil texture.There is significantly correlation between volume percentage of <0.002 mm and
D
values;and
D
values are affected indirectly by other soil size classes which are related to <0.002 mm.
D
values of PSD could represent the degree and proportion of the soils finer.In addition,because of the nonlinear characterization of volume cumulative percentage,one
D
value could not characterize the PSD across the whole size class range of the measurements.Two fractal scaling domains were identified and
D
1
and
D
2
were calculated,and
D
1
is larger than
D
2
.The boundary between the two domains is located at the particle diameter of 15 μm.Probability of fragmentation calculated by
D
1
and
D
2
is scale-dependent.
2009 Vol. 7 (2): 35-41 [
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42
LI Wei-；Tu-Xin-Xiao-；Yue-Yong-Jie
Rainfall characteristics under canopy of main tree species in loess area
With the simulated rainfall,the rainfall characteristics under canopy of the mainly tree species in loess area was studied applying the color-spot method.Combining software,such as Auto CAD and Excel,within the stand class grade of 0.1mm,the rainfall characteristics of the trees under canopy was analyzed,and the rainfall kinetic energy in and out of forest was sludced comparably.The results showed that,1) Under varied rain intensities,the observed median diameter of canopy raindrops are kept in a range stably.The rainfall characteristics under canopy won't be affected by the rain intensity of glade.2) It is probable to make a distortion by using gaussian distribution function and class chi-square distribution function to describe and analysis the rainfall characteristics under canopy,better math form should be found to figure it.3) The distribution chart of diameter-volume of canopy raindrop is a double-peak curve,which showed that Best function is unable to make a precise description of the large rain drops as well,while polynomial function is better than it.4) The descending order of kinetic energy of tree species per liter as the follows:
Platycladus orientalis
(28.18 J),
Pinus tabulaeformis
(26.74 J),
Acer truncatum
Bunge (25.75 J) and
Robinia pseudoacacia
Linn(20.07 J).And the results also can be used to evaluate whether vegetation canopy strengthens the rainfall energy,under the condition of abundant rainfall.
2009 Vol. 7 (2): 42-47 [
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48
MENG Qiang-Xiang-；Liu-Guo-Ban-；Yang-Qi-Ke
Dynamic change of land use and its ecological effects on the Loess Plateau
Based on RS,GIS and related data,the paper analyzed the land use change on the Loess Plateau between 1986 and 1997.With the Markov Model,the land use change in the future was forecasted,and the relation between land use and ecological effect by ecological response limit was studied.Results showed that the land use dynamic change on the Loess Plateau is remarkable,the relative value of which is larger than the absolute value,and land use has changed obviously between land use types.The descending order of land use change rate is grass with high coverage,construction land,other forest land,shrub land,irrigated land, water body,waste land,wood land,rainfed land and other grass land.Land use dynmic change index is 2.17%,from vertical c.g.index change,status of other grass land and irrigated land is improving,stock raising is suitablerice,food need drives the ascend of vertical c.g.index of rainfed and irrigated land and forest land.land use dynmic change index of irrigated land and other grass land is decline,and others is raise;ecological response limit is 5.17,7.30,7.60 and 7.65 in 1986,1997,2008 and 2019,ecological response limit is uptrend,but range is decrescent.
2009 Vol. 7 (2): 48-53 [
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54
QIN Wei-；Shu-Qing-Ke-；Liu-Zhong-Ai-；Xue-Zhi-De-；Diao-Lei-Lei-；Li-Yang
Assessment on soil conservation value of the returning farmland to forestland and grassland project based on GIS and RS:Taking the Simianyaogou Watershed of Wuqi,Shaanxi as the example
The benefit of soil conservation is an important ecological benefit of returning farmland to forestland and grassland.Assessing value of soil conservation can provide an important reference for founding ecological compensation mechanism of returning farmland to forestland and grassland.The Simianyaogou Watershed of Wuqi County,a demonstration area of returning farmland to forestland and grassland in China,was chosen as a study case.The type and area of returning farmland to forestland and grassland were monitored using RS and GIS techniques.The improved
L
factor of the Revised Universal Soil Loss Equation(RUSLE) was presented,which considers the effect of land cover for erosion.Based on RUSLE and GIS,the dynamic changes of soil erosion were assessed due to returning farmland to forestland and grassland.Then,soil conservation value of returning farmland to forestland and grassland was calculated using method of opportunity cost and replacement price.The results showed that in period from 1997 to 2004,the total area of returning farmland to forestland and grassland was 1 895.8 hm
2
,of which the afforestation in wasteland was 369.99 hm
2
,returning farmland to forestland was 357.48 hm
2
,returning farmland to grassland was 901.72 hm
2
and closure measure was 266.61 hm>
2
.The annual modulus of soil erosion reduced by 4 644.04 t/(km
2
·a).The intensity of soil erosion fell from very strong grade into moderate grade.The annual soil conservation value of returning farmland to forestland and grassland was up to 13.24 million yuan,of which 0.08 million yuan for reducing soil loss,11.8 million yuan for reducing fertility loss,1.24 million yuan for reducing sediment deposition and 0.12 million yuan for increasing soil nutrient.
2009 Vol. 7 (2): 54-62 [
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1747
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63
LIU Bin-Hui-；Liu-Yan-Ling
Spatial distribution of rainfall erosivity in Heilongjiang Province
The spatial distribution of rainfall erosivity and erosive rainfall in Heilongjiang Province was studied,based on the daily rainfall data of 16 weather stations during the period from 1960 to 2000.Among the 16 weather stations,the average annual erosive rainfall frequency is between 9 and 15 days,and annual rainfall amount above with daily rainfall above erosive threshold is between 192 mm and 387 mm.Average annual rainfall erosivity(
R
factor) is between 794 and 2 144 MJ·mm/(hm
2
·h·a).Rainfall erosivity is mainly concentrated in June to September,and reach its highest value at later July or begin of August.The total rainfall erosivity in June to September is about 88% to 95% of annual value.
2009 Vol. 7 (2): 63-68 [
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69
LI Liang-Dong-；Gao-Feng-；Mu-Xin-Min-；Mo-Chi
Spatial-temporal varieities of rainfall erosivity in the Liaohe River Basin
Rainfall erosivity is an index of erosion ability of rainfall.With the daily rainfall data of ten meteorological sites in Liaohe River Basin,we estimated the rainfall erosivity and analyzed the spatial and temporal variability in the Liaohe River Basin by using the daily rainfall erosivity model.The results showed that the spatial characteristic of rainfall erosivity is consistent with the spatial distribution of rainfall,declining from southeast to northwest and varying from 1 000 to 3 800 MJ·mm/(hm
2
·h·a).The season distribution of rainfall erosivity is centralized and that in June,July,Augest occupy 80% of the whole year.The inter-annual variation is large,and
C
v
is between 0.367 and 0.649,but the result of Mann-Kendall test showed there is no significant trends of variation.Especially,in the basin of West-Liaohe River Basin where the soil erosionis most serious,the rainfall erosivity is comparatively low,although the rainfall erosivity is more concerted and varies much more between years.
2009 Vol. 7 (2): 69-73 [
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74
LI Tie-Hong-；Hai-Chun-Xin-；Cong-Yan-Jing
Topsoil particle-size distribution and its spatial variation in Mo Us Desert
In order to know the particle-size distribution of Mo Us Desert,top soil(0-5 cm) from grassland,woodland,cultivated land,fixed dune,semi-fixed dune and moving dune of Mo Us Desert were collected.We calculated particle-size parameters using Moment law computation to study topsoil particle-size distribution of the Mo Us Desert.The results showed: the topsoil particle-size of different sandy land types was mainly in sandy range(1 000-50 μm),and the content percentage was 41.22%-97.63%.Silt(50-2 μm) was 0-51.61%.Clay(<2 μm particles) was 2.71%-10.38%.The average particle-size of semi-fixed dune and fixed dune was 145.491 μm and 157.563 μm respectively,which was a lower level among the land types.The average particle-size of fixed dune and cultivated land was 128.782 μm and 118.175 μm,which was a medium level among the types.The average particle-size of grassland and woodland was 94.667 μm and 108.819 μm,grain-size of which was fine.The particle-size distribution of moving dune was coarsest.The particle-size classification of moving dune and semi-fixed dune was better,which showed a strong positive bias and a sharp peak.The average particle-size distribution of cultivated land,woodland and grassland also displayed a positive bias,but theirs drift rate was lower,the peak was also gentler.The particle-size distribution was significantly different among the land types of Mo Us Desert,which led to the difference of wind erosion.From the view of spatial variation,the average particle-size of topsoil changed the coarse particles to the fine particles gradually from northeast to southwest in Mo Us Desert.
2009 Vol. 7 (2): 74-79 [
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1656
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80
WANG Shuai-；Ha-Shi
Air flow dynamics of the blowout trough in the Hulun Buir sandy grassland
Blowout trough is the best surface expression of the aeolian processes responding to regional climatic changes and human ctivities,which is also the driving force of grassland landscape heterogeneity.When the wind approaches to the blowout trough parallel to the thread orientation,the velocity is become slow because of the expansion,and until jet usually occur at the 3/4 of the central line of the deflation basin.The results show that more and more air flow was sucked into the blowout trough,and the rim of the blowout trough is usually eroded by this process,and flow deceleration and expansion occur to the depositional lobe.When the wind approaches to the blowout trough obliquely,the air flow is usually extremely turbulent,and air flow was sucked into the blowout trough from the rim,because the erosion wall is very steep,so the air flow is steered as return flow,and erodes the coming wall and deposited on the opposite wall.Blowout trough morphologies are explained as a function of these air flow patterns.
2009 Vol. 7 (2): 80-85 [
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1520
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1526
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86
DAN Sha-；Ju-Hua-Yong-；Zhang-Chun-Lai-；Su-Ge-Ri-Le
Investigation of vegetation restoration in the area of Beijing and Tianjin sandstorm source control project
Regional vegetation restoration effect of the area of Beijing and Tianjin sandstorm source control project is the crucial part for environment research of this area.Based on the traditional ecology field survey method,the plant diversity variation under the Beijing and Tianjin sandstorm source control project was studied.The original plant coverage date has been compared with that one which has been measured after the implementing of the first phase of the project by Normalized Difference Vegetation Index(NDVI) method for dimidiate pixel model.The results showed that the low covered area have reduced gradually,and the high covered area have increased correspondingly in the sandstorm source controlled area;and there are good vegetation restoration potential and tendency in this region.The average vegetation coverage has been risen in this area based on five-year efforts of the Beijing and Tianjin sandstorm source control project.The research results provide basic data and reference for second phase of the project.
2009 Vol. 7 (2): 86-92 [
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1673
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1598
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93
JU Ai-Beng-；Chen-Zhi-Biao-；Chen-Li-Hui
Spatio-temporal variation of eroded landscape in typical small watershed in the hilly region of red soil: A case study of Zhuxihe Small Watershed in Changting County,Fujian Province
Zhuxihe Small Watershed in the hilly region of red soil was chosen as the typical study area.Based on the soil erosion data of 1999 and 2007,the transfer matrix of eroded landscape types were extracted by using ArcGIS 9.0 software,and the spatio-temporal variation of eroded landscape was analyzed by using barycenter transfer model.The analyse on watershed landscape variation will provide important bases for ecological construction in future.The statistics on areas and percentages of landscape types show that slight erosion has been dominating landscape pattern inlaid by some small pieces of light,moderate,strong,very strong and severe erosion in 1999 and 2007.The analysis on transfer matrix of landscape pattern shows that the areas of slight and light erosion increased,among which the slight erosion in the eastern part of watershed increased most greatly with most stemming from light erosion.It is found that the areas of moderate,strong,very strong and severe erosion decreased,among which the area of severe erosion decreased most rapidly,and it has resulted in the converting of severe erosion into moderate erosion.This phenomenon mainly appears in the sub-watershed of upper reaches of Zhuxihe Small Watershed,including Youwuzhen and Gaopiduan. The study on barycenter transfer model indicates that the barycenter transfer distance of severe erosion was the furthest from 1999 to 2007,the barycenter transfer direction of light,moderate and very strong erosion was southwest,and the barycenter transfer direction of strong erosion was southeast,only the barycenter transfer stern vally direction of slight erosion was northeast.Human activity is the main driving factor for the dynamic variation of spatial pattern of landscape in this area.
2009 Vol. 7 (2): 93-99 [
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100
LI Fen-；Wang-Ji-Jun
Driving forces analysis of agro-ecological security change of Zhifanggou Catchment in Hilly-gully Region of the Loess Plateau
Based on investigation and monitoring data from 1985 to 2006 at Zhifanggou Catchment in Hilly-gully Region of the Loess Plateau and current research achievement,methods of principal components analysis(PCA) and path analysis(PA) were combined to analyze impact factors which affect change of agro-ecological security state,and driving forces of agro-ecological security change were discussed.The obtained results show that the basis of agro-ecological security change are natural conditions and its main driving forces are socio-economic situations that can be classified into four types,which are economic development,the pressure of population,industrial restructuring of catchment,agricultural scientific and technological progress.Besides,the related policies of nation and region,correlation degree of agricultural industrial chain and resources have influence on it to some extent.
2009 Vol. 7 (2): 100-106 [
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1494
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1280
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107
LIU Ceng-Wen-；Duan-Er-Jun-；Fu-Gang-；Cui-Fang-Fang
Soil polarizations of forest plantation in semi-humid gullied area of southern Loess Plateau
Soil property polarization means non-equilibrium or polarizing tendency of development.In order to recognizing the trends of soil polarization of planted pure forests in semi-humid gullied area of southern Loess Plateau,soil properties of planted forests of
Pinus tabulaeformis
,
Platycladus orientalis
and
Robinia pseudoacia
were determined with sampling methods of multi-plots and multi-sites.It can be conclusioned that: 1) Forest soil of
Pinus tabulaeformis
was light worsened in physical properties(polarization value
P
r
is -9.26%,the same as following),partially acidified,moderate leaned in nutrients(
P
r
is-11.54%),moderate worsened in some enzyme activities(
P
r
is-12.88%) and its total number of microorganisms increased.2) Forest soil of
Platycladus orientalis
showed tendency of being worsened in physical properties,conserved stable in pH value,light leaned in nutrients(
P
r
is-8.24%),no obviouse indication of polarized in some enzyme activities and its total number of microorganisms conserved stable.3) Forest soil of
Robinia pseudoacia
was moderate worsened in physical properties(
P
r
is-12.74%),conserved stable in pH value,moderate leaned in nutrients(
P
r
is-12.77%),light worsened in some enzyme activities(Pr is-8.89%) and its total number of microorganisms conserved stable.4) The absolute comprehensive polarizations of soil among different properties took quantitative composition of microorganisms as the most sensitive and pH as the most slowly.These conclusions mean that long-term grown or continuous planted pure forests will risk soil polarization and degradation.
2009 Vol. 7 (2): 107-112 [
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1744
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1397
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113
LIU Yan-；Song-Yu-Min-；Chen-Fu-Liang-；Ma-Feng-Yun-；Hou-Long-Yu
Effects of mulching on emergence rate of direct seeding of four tree species
In order to solve the problems of drought and animal damages and so on with direct seeding in spring in Shandong barren mountain area,taking four species tree seeds as the test material,a new film mulching(film mulching 2) was studied.The results showed that compared with the conventional film mulching(film mulching 1) and open field(control area),film mulching 1 increases day average temperature of surface and soil temperature of vertical profile,which supplies suitable temperature to the generation of seeds,and that the surface temperature of film mulching 2 is higher than that of the soil,which is suitable to sow in later spring.Film mulching 2 can effectively improve water content in the soil of 020 cm depth and use limited precipitation resource and the water preservation and storage capacity are higher than these of the conventional film mulching,which efficiently settles the problems of drought and supplied a perfect water environment to seedling growth.The enmergence rate and seedling height of four tree species with film mulching methods are significantly higher than those with open field treatment.And for litter seeds,including
Robinia pseudoacacia
L.and
Amorpha fruticosa
L.,the enmergence rate and seedling height with film mulching 1 are higher,while those are greater with film mulching 2 for big seeds,including
Sophora japonica
L.and
Gleditsia sinensis
Lam..Those big seeds should be choosen in direct seeding in barren field.For direct seeding with little seeds,more grains in each hole are needed to keep high enmergence rate.
2009 Vol. 7 (2): 113-117 [
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118
ZHOU Gang-；Tian-Yo-Xin-；Chen-Guo-Yu-；Fu-Zheng-Liang-；Bao-Wen
Runoff and sediment yield on slope land in initial stages of conversion of cropland to forest in Northwestern Hunan Province
In order to evaluate ecological benefits of conversion of cropland to forest in Northwestern Hunan Province scientifically,11 types of conversion of cropland to forest were studied with permanent investigation in 3 rock type areas in Rvrezai small watershed there.The results showed that,1)Both the surface runoff and sediment yields were reduced on the slope lands of afforestation,29.45% of surface runoff and 47.02% of sediment were reduced in the board-shale areas,56.54% of surface runoff and 64.04% of sediment were reduced in the granite areas with terracing,14.16% of surface runoff and 36.27% of sediment were reduced in the lime-rock areas in initial stages of conversion of cropland to forest.2)The surface runoff and sediment yields were reduced greatly by terracing,and average surface runoff and sediment yields on terrace is only 34.92% and 3.66% of that on slope land respectively.3)The surface runoff and sediment yields were decreased greatly with the rainfall declining.The surface runoff and sediment yields caused by the rainfall more than 50mm were 52.17%、70.79% respectively of that in the whole one year.
2009 Vol. 7 (2): 118-122 [
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