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2010 Vol.8 No.2
Published 2010-04-30
Articles
1
ZHANG Chao-；Liu-Guo-Ban-；Xue-Sha-；Tu-Na
Evolution of soil anti-erodiblity of
Robinia pseudoacacia
L. plantation at different ages in Hilly-gully region of Loess Plateau
In order to reveal the effects of plantation on soil anti-erodibility,
Robinia pseudoacacia
plantation at different ages in Hilly-gully region of Loess Plateau was chosen to analyze the changes of soil anti-erodibility,and the slope cropland was used as contrasts.The results indicate that the contents of >0.25 mm soil water-stable aggregates,>0.5 mm soil water-stable aggregates,mean weight diameter and organic C increase significantly compared with slope cropland and increase with ages.Aggregate state and aggregate degree are improved markedly compared with slope cropland and declined firstly then raised with increasing of ages.Ratio of soil structure deterioration,dispersive rate and disporsive coefficient take on wavelike drop.Small microaggregates and mechanical composition transform into ones with much bigger diameter.Results of correlation analysis shows that the >0.25 mm soil water-stable aggregates,>0.5 mm soil water-stable aggregates,mean weight diameter and organic C positively correlated with N,available N,available K and total P(
P
<0.05),but negative with soil density.High negative correlation is observed between ratio of structure deteriorative,dispersive rate,dispersive coefficient and total N,available N,total P.Soil anti-erodibility index(I)rise with increase of ages and can generally reflect the change of soil anti-erodibility.It can be concluded that the poor soil anti-erodibility of slope cropland under erosive environment owing to human cultivation activities is improved greatly by plantation.
2010 Vol. 8 (2): 1-7 [
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8
YIN Xian-Beng-；Zhou-Yun-Chao-；Luo-Meng-；Zhang-Ma-Gen-；Tu-Zheng-Liang-；Yang-Xiao-Mao
Contrast on soil anti-erodibility of main soils in the source area of Ganjiang River
For the research to soil anti-erodibility of main soils in the source area of Ganjiang River in Jiangxi Province,the anti-erodibility index of various soil,such as organic matter content,bulk density,corrosion resistance index,aggregation condition,aggregation degree,dispersion rate,dispersion coefficient,the rate of structural damage,and water-stable aggregate content and so on were determined,and the principal component analysis(PCA) to follow the comparison was used.The results indicated: the discending order of soil anti-erodibility was mountain coppice soil(74.67),yellow soil(61.90),mountain yellow-red earth(47.26),yellow red earth(44.77),purplish soil(39.79),red earth(28.34).Moreover,several measures should be taken to improve soil anti-erodibility,such as,increasing the vegetation coverage,reducing the man-made damage and increasing fertilization in areas of Red earth and Purplish soil.Many propaganda works should be developed within mass to enhance their environment concern and prevent soil and water from being destroyed in the process of harnessing in areas of Mountain yellow-red earth and Yellow red earth.Besides,current eco-environment should be maintained while it was utilized comprehensively and a number of actions that resulted in soil erosion should be held back as far as possible in the areas of Mountain coppice soil and Yellow soil.The content of soil organic,aggregation degree and the aggregation condition were the best factors of appraising soil anti-erodibility in the source area of Ganjiang River.
2010 Vol. 8 (2): 8-14 [
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15
XIAO Pei-Jing-；Tao-Wen-Yi-；Shen-Shen-Zhou-；Yang-Chun-Xia
Reduction effects of grass on runoff and sediment and its mechanical mechanism
Reduction effects of grass on runoff and sediment as well as its mechanical mechanism was studied under rainfall intensities of 45,87 and 127 mm/h on 20°grass slope using simulated rainfall experiment.The results showed that soil infiltration rate of grass slope was 2.1-4.2 times higher than that of bare slope.Flow velocity,runoff and sediment amount on grass slope decreased by 77.3%-79.8%,51.9%-99.1% and 93.6%-99.2% respectively compared with those on bare slope.Relationship model between flow shear stress and sediment amount was built by analyzing of carrying force of soil partial,which can be used to predict the amount of soil loss on grass slope.The critical flow shear stress of 2.857 N/m
2
on grass slope and 0.861 N/m
2
on bare slope were measured based on the relationship model under experiment condition.The sediment amount ncreased with the increase of flow shear stress.The experiment results are meaningful for quantifying runoff and sediment reduction and deepening soil erosion mechanical process also.
2010 Vol. 8 (2): 15-19 [
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20
XIE Liang-Qing-；Tun-Pan-；Gu-Chang-Xi-；Cao-Zhen-Xin-；Ge-Jia-Jie
Calculation of the soil erosion modulus of basin with the measurement method of sedimentation in Karst area
For studying the soil erosion modulus in the Karst rocky desertification areas,the measurement method of the sedimentation at the deposition zone of basin is used to calculate the soil erosion modulus and to speculate on the rocky desertification process of the Mawoshan of Wumeng range in the Karst area.The environmental effects on the soil erosion modulus,caused by human being's activities in Karst rocky desertification areas are discussed simultaneously.The research results indicate that the soil erosion modulus in the Mawoshan is very high,up to 2 900.55 t/(km
2
·a),which can reflect the position of the soil erosion objectively in the karst rocky desertification areas.Considering nothing but total quantity changes in the process of calculating the soil erosion modulus,the measurement method of the sedimentation at the deposition zone should be choiced firstly for the soil erosion calculation in the Karst rocky desertification areas where there is no observation data and survey station.
2010 Vol. 8 (2): 20-23 [
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24
LIU Yan-Ling-；Liu-Bin-Hui-；Wang-Li-Gang-；Yuan-Wen-Chao
Variation characteristics of rainfall erosivity in Heilongjiang Province
We analyzed the relationship between change characteristics of rainfall erosivity and precipitation using daily rainfall data during 1960 to 2000 from 16 weather stations in Heilongjiang Province.The results indicate that: trend of annual rainfall erosivity from 1960 to 2000 is increasing,as same as trend of annual precipitation and trend of erosive precipitation,however,the changes are not significant.The annual rainfall erosivity,annual precipitation and erosive precipitation increase with rate of 1.47 MJ·mm/(hm
2
·h·a),0.29 mm/a,0.35 mm/a from 1960 to 2000,respectively.There are eleven weather stations that the rates of the tendency are positive,the annual rate of the tendency of rainfall erosivity increase largestly in Mudanjiang,which rate is 15.6 MJ·mm/(hm
2
·h·a);while there are five weather stations that the rates of the tendency are negative,the annual rate of the tendency of rainfall erosivity decrease the minimum in Qiqihaer,which is-16.8 MJ·mm/(hm
2
·h·a),all sites' changes are not reach significant level.Apart from(Harbin,Keshan,Huma,Tonghe),the impact of the changes of frequency of erosive rainfall on the changes of erosive rainfall is greater than the impact of the intensity of erosive rainfall on the changes of erosive rainfall in these 16 weather stations.The results can provide a basis for the prediction of soil erosion and planning and decision-making for soil and water conservation.
2010 Vol. 8 (2): 24-29 [
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30
CAO Ying-；Zhang-Guang-Hui-；Luo-Rong-Ting
Response of runoff and sediment discharge to global climate change in Jinghe River Basin
Global climate change had a tremendous impact on the water cycle.Changes in precipitation features varied from region to region,and they also impact on river runoff,sediment discharge and regional soil loss significantly.Based on the data of precipitation,runoff and sediment discharge from 1961 to 2006 in Jinghe River Basin,this study analyzed the statistical relation between precipitation and runoff,and between runoff and sediment discharge.According to the results of precipitation of three periods(2010—2039,2040—2069 and 2070—2099) which simulated by five GCMs(HadCM3、CGCM2、CSIRO-Mk2、ECHAM4 and GFDL),the statistical relations to calculate runoff and sediment discharge in the future was brought.The results showed the ability of simulated data varied by different GCMs.It led to the difference of estimated runoff depth and sediment discharge.Compared of A2 and B2 scenarios published by IPCC,it indicated that the response of runoff and sediment discharge under A2 scenario was more strongly.And contrasted to the measured period(1961—2006),the variable ranges of precipitation,runoff depth and sediment discharge from 2010 to 2099 were-5.53%-31.65%,-9.26%-53.44%,-11.13%-64.59% respectively,and the average increases were 11.69%,19.78% and 23.94%.The finding of this study played guiding significance to the planning of soil and water conservation and strategy establishment in the future of the Loess Plateau.
2010 Vol. 8 (2): 30-35 [
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36
ZHENG Hai-Jin-；Fang-Shao-Wen-；Yang-Ji-；Shang-Chong-Jun-；Hong-Bang-Wen-；Song-Ru-Jun
Analysis of rainfall erosivity on sloping land of Quaternary Red Earth in North Jiangxi Province
Rainfall erosivity is necessary to develop the soil erosion model.To study the law of rainfall erosivity on sloping land of quaternary red earth,an experimental spot was estabished on the representative area to investigate rainfall and sediment from 2001 to 2005.The relations between rainfall parameters and sediment amount were analyzed.Then,rainfall erosivity was calculated and its distribution regular in time was studied.At last,the relation between rainfall erosivity and precipitation was analyzed for easy caculation.It is suggested that ∑
EI
30
can represent commendably rainfall erosivity in the study area.Rainfall erosivity is variabile in yearly and monthly distribution,and mainly distributes between April and September,accounting for 91.66 percent among that in one year.It is also shown that rainfall erosivity has similar trendency in time distribution with precipitation,and their correlation coefficient is 0.838.The prediction equation of rainfall erosivity is important to estimate rainfall erosivity when the continuous record of rainfall is lack.
2010 Vol. 8 (2): 36-40 [
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41
YANG Xiao-Mei-；Cheng-Ji-Min-；Meng-Lei
Carbon storage and density features of natural forest of
Pinus tabulaeformis fshekannesis
in Loess Plateau
Based on investigation and laboratory analysis,carbon storage and distribution characteristics have been studied on natural secondary forest of
Pinus tabulaeformis fshekannesis
in Ziwuling area of Loess Plateau.The results showed that: 1) the rate range of carbon content was 0.413 7-0.517 4 g/g and 0.187 2-0.500 3 g/g in vegetation layer(trees,shrubs and grasses) and litter layer respectively.Furthermore,great significance of carbon content had appeared at different organs and layer.Carbon content in soil layer reduced dramatically with the depth.2) In spatial scale,total carbon density was 236.04 t/hm
2
.The discending order of that in different layers was soil layer,vegetation layers,litter layer,and was 107.55 t/hm
2
,95.20 t/hm
2
and 33.29 t/hm
2
respectively.Furthermore,the total carbon storage capacity was 15.97 Mt.The soil carbon storage was 7.27 Mt,largest in this three carbon compartment.It takes up to 45.52% of whole forest,and 1.14 and 3.22 times,respectively for vegetation and litter layer carbon storages.
2010 Vol. 8 (2): 41-45 [
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46
SONG Xiao-Yan-；Mu-Xin-Min-；Gao-Feng-；Wang-Fei-；Wang-Shuang-Yin
Analysis on historical evolution and driving force of rainfall and runoff of Harbin Station in Songhua River
As rainfall and runoff are important natural forces to cause soil erosion,studying characteristics of runoff and its affecting factors has significance to understand the laws of soil erosion.Long sequence data of 1909—2005(lack 1943—1952) of the rainfall and runoff and the methods of runs theory,Mann-Kendall and double mass curve were used,and annual variability of the average rainfall and runoff depth of Harbin Station on the Songhua River were analyzed.The results show that: Over the past 87 years,average rainfall is 501.7 mm, and average runoff depth is 106.3 mm.In Harbin Station,positive run-length of average rainfall and runoff depth are 1.7 years and 2.1 years respectively,which are less than their negative run-length 2.0 years and 2.7 years respectively.So rainfall and runoff are even more likely to appear dry years.Although there are no obvious trends in the average rainfall and runoff depth,there are significant stage characters.Both rainfall and runoff depth may be divided into three wet stages,one flat stage and three dry stages.Due to human activities,the rainfall-runoff sequence may be divided into 1909—1915,1916—1927,1928—1978 and 1979—2005 four phases.
2010 Vol. 8 (2): 46-51 [
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52
HU Zhen-Hua-；Wang-Jun-；Li-Chang-Sheng
Infiltration experiment of coal-ash mixed with earth
The experiment was done at the soil and water conservation institute of Shanxi agricultural university dealing with the coal-ash infiltration laws of three kinds of density(0.9,1.0,1.1 g/cm
3
)and three kinds of mixed ratio(1.0∶0.5,1.0∶1.0,1.0∶2.0).The results showed that: 1)with the density increasing,the infiltration rate of coal-ash deceased,and the relationship between density and infiltration rate is a power function;2) the density and surface solidity of the coal-ash increased as the coal-ash mixed with the earth,and its infiltration rate deceased;3) the infiltration rate of two mixed materials is mainly dependent on the medium value diameter,if it's bigger,the rate is also bigger;4) the infiltration process can be expressed by universal empirical formula with the pure coal-ash,and expressed by the universal empirical formula and Kostiakov formula with the mixed coal-ash.But there are small offsets between the experimental and simulated curves with the small density in the secondary phase of infiltration process.The research is importance in reducing dust pollution,decreasing infiltration and predicting runoff amount in the coal-ash storage place.
2010 Vol. 8 (2): 52-58 [
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59
ZHANG Zhen-Guo-；Jiao-Ju-Yang-；Gu-Yan-Feng-；Wang-Ning
Interpretation proportion analysis of different environmental factors on vegetation variations in the Hilly-gully area of Loess Plateau
In order to provide scientific basis for vegetation restoration of abandoned farmlands in the Hilly-gully area of Loess Plateau,it is important to study the relation between vegetation variation and environmental factors.Based on observation of 42 plots of abandoned farmland in Ansai,affection of local environment factors on vegetation restoration was analysised from single factor,packet variables and significant factors through Canonical Correspondence Analysis and Partial Canonical Correspondence Analysis.The results show that key environment factors affecting variation of vegetation on abandoned cropland in the Hilly-gully area of Loess Plateau are soil organic matter,total phosphorus,available phosphorus,soil water content(0-40 cm),soil invertase,soil structural index,<0.001 mm clay,aspect,and abandonment age of cropland.To promote the progress of vegetation restoration on abandoned cropland,it is essential following natural restoration domination and artificial regulation assisted such as transplanting or applying fertilizers.
2010 Vol. 8 (2): 59-67 [
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68
GUO Man-；Zheng-Fen-Chi-；An-Shao-Shan-；Liu-Yu-；Wang-Ban-；FredericDarboux
Application of Le Bissonnais method to study soil aggregate stability in the Hilly-gully region
Soil aggregate stability is a key indicator for soil quality evaluation.The transition area from forest to grassland zone of the Hilly-gully region,located in Yangou Catchments in Yan'an City,was taken as a research site.Soil samples from six vegetation types during vegetation natural restoration were used to measure soil water-stable aggregate using Le Bissonnais(LB) method,and compared the results of LB 3-treatments with the Yoder method.The results showed that,in the 3-treatments(fast wetting,slow wetting,and wetting stirring) of LB method,fast wetting(FW) was the most destructive degree to the soil aggregate stability,the distribution of soil water-stable aggregate mainly concentrated in 0.05-0.5 mm;slow wetting(SW) was the least destructive degree to soil aggregate stability,soil water-stable aggregate content was mainly >2 mm;the destructive degree of soil aggregate structure by wetting stirring(WS) was between FW and SW treatments,the soil water-stable aggregates size was well-distributed.It was explained that the primary destructive mechanism of soil aggregate structure was dissipation.During the period of 100a of abandoning cropland,the succession process of vegetation experience is annual herbaceous(4 a)—perennial herbaceous(16 a)—semi shrub(29 a)—shrub(55 a)—arbor(100 a).With the succession process of vegetation,soil water-stability aggregate size shifted from small size to large size,soil structure was improved.The correlation between >0.5 mm soil aggregate content or mean weight diameter(MWD) measured by FW or SW and soil organic carbon or physical clay content was significantly different;but for WS treatment,there was no significant different between soil aggregate content or MWD and soil organic carbon or physical clay content.This result showed that soil organic matter and physical clay content mainly influenced dissipation and disintegration by clay swelling and mechanical stirring had no significant impacts on soil aggregate stability.Comparing with the Yoder method,SW and Yoder method have highly comparability,and SW treatment of LB method was suitable to measure soil water-stable aggregate during vegetation restoration in the Hilly-gully region.
2010 Vol. 8 (2): 68-73 [
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74
MA Feng-Yun-；Bai-Shi-Gong-；Hou-Ben-Dong-；Liu-Yan-；Hou-Long-Yu
Soil properties of degraded
Robinia pseudoacacia
plantation in Yellow River Delta
The degradation of
Robinia pseudoacacia
plantation on Yellow River Delta took place in large area and the shoots of R.pseudoacacia trees were dried-up with different degree.In order to reveal the degradation causes of R.pseudoacacia plantation,soil characteristics of R.pseudoacacia plantation were studied.The results showed that soil density increased gradually with the increasing of the degradation degree of R.pseudoacacia plantation.With increasing of degradation degree of R.pseudoacacia plantation,many indices of soil nutrition were shown by decreasing degree.The contents of salt in soil increased gradually with the degradation degree increasing.It was shown that with degradation degree increasing of the R.pseudoacacia plantation the activities of soil enzymes such as peroxidase,catalase,polyphenol oxidase,urease decreased gradually.The number of total microorganism in soil of the R.pseudoacacia plantation decreased with aggravation of degradation.
2010 Vol. 8 (2): 74-79 [
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80
YANG Feng-；Li-Chuan-Rong-；Sun-Meng-Gao-；Zhang-Liu-Dong-；Sun-Jiu-Shi-；Liu-Pu-Xiao
Soil structure characteristics and health evaluation of different revegetation types around the coastal damaged mountain
The soil structure characteristics were studied on seven revegetation types by using dry sieving and principal component analysis(PCA) in Huangwu County,Yantai City,Shandong Province.The results show that the soil densities of artificial revegetation were significantly lower than that of mature brushwood,among which,that of
Quercus acutissima
and
Pinus thunbergii
mixed forest was the lowest.The discending order of effects of soil porosity improved by plantations is: mixed forests,pure forests,brushwood.The soil porosities in 0-10 cm layer were largger than that of 10-20 cm.Soil water carrying capacities and its average mass diameters of soil aggregate of plantations were all higher than that of brushwood.Among these revegetations,the improved soil porosity of
Quercus acutissima
and
Pinus thunbergii
mixed forest was the best.Comprehensive evaluations of soil structure health indicate that the health of brushwood was the worst,that of
Quercus acutissima
and
Pinus thunbergii
mixed forest was the best.The results can provide scientific references for revegetations in the similar damaged mountain area.
2010 Vol. 8 (2): 80-84 [
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85
ZHANG Bei-；Zhang-Jian-Jun
Application of LFA method to landscape function assessment of vegetation in Western Shanxi Loess Plateau
Based on the LFA(Landscape Function Analysis) method,35 samples of 7 land types and the effects of the vegetation type and human activity on forest landscape function and soil properties were evaluated.The results show that the affects of different vegetation type on soil properties are distinctly different.The soil properties(structure stability,infiltration,nutrients cycle) of natural secondary forest are the best;that of
Robinia pseudoacacia
and
Pinus tabulaeformis
plantation are second;that of grassland is the worst.Human activity has obvious affection on landscape function of plantation.The affection of vegetation on forest soil properties and the affection of human activity on forest landscape function and soil structure stability can be evaluated by LFA.
2010 Vol. 8 (2): 85-90 [
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91
LIU Hong-Yan-；Diao-Yu-Sen
Analysis on landscape pattern of land use in Harbin based on remote sensing image
In this paper,we analysis on landscape pattern of land use in Harbin,based on the 1/250 000 TM remote sensing image of Harbin in 2000.Used various types of landscape parameters,we calculate the indexes including patch area,number of patch,patch density,edge index,shape index,connection index and diversity index on levers both of Patch and Land.It shows: 1)Farmland is the matrix of the landscape.2)The land patches of farmland and land used for construction have complicated edge,high edge density,good connection.3)The land patches of woodland,grassland,water area,unutilized land have simple edge,low edge density,bad connection.In conclusion,both the amount of patches and diversity are decreased,and the area of plain paddy landscape element is increased.
2010 Vol. 8 (2): 91-98 [
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99
WEI Zhen-Rong-；Xiao-Yun-Li-；Li-Dui
Natural restoration process and diversity change of vegetation on abandoned cropland of Bashan Mountain region
Bashan Mountains,a transition region of North and South China,is an important area of water resources retention in China.The researches on change characteristics of species diversity index and succession process of vegetation restoration on abandoned cropland are very important for artificial vegetation construction.We studied the changes of species diversity on abandoned cropland during natural restoration process of vegetation by using the methods of substituting space series for time series.Results show: 1) The vegetation succession order on abandoned cropland of Bashan Mountains is annual herb community,perennial herb community,miscellaneous shrub and herb community and broadleaf forest community dominated by
Quercus variabilis
or
Quercus variabilis
and
Quercus baronii
,and it generally takes 40-50 years to form this community.2) Species diversity changes with the site environment.All species diversity indexes on shady slope are obviously higher than sunny slope,but nearly with the same change law.In early succession stage,species number,Shannon-wiener index,Simpson index and Pielou index are lower comparatively.With the increase of succession time,all community diversity indexes increase wavily.In the twenty-fifth year of the succession stage,species number,Shannon-wiener index,Simpson index and Pielou index reach to maximum,which are 23,2.5,0.89 and 0.8.When vegetation develops to zonal plant community,all species diversity indexes decrease a little bit,and tend to stablility.This result is very meaningful for ecological improvement by natural vegetation restoration and manual management of vegetation accoding vegetation succession process.
2010 Vol. 8 (2): 99-104 [
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105
DAN Jiang-Hua-；Wang-Ke-Qi-；Chen-Zhi-Zhong-；Zhang-Rui-Guo-；Chen-Quan-Fang
Application of pond system to control non-point pollution in rural area
The domestic sewage discharge is the important source of non-point pollution in rural area.To purify domestic sewage from rural area,pond system were constructed in downstream of domestic sewage rout to test the effect of treatment by pond system.Field monitoring were conducted and lasted more than a year.The result showed: 1) the pond system can control the outputs of ammonia nitrogen,total nitrogen and total phosphorus,the corresponding decreasing value were 3.78,4.20 and 1.06 g/(m
2
·d),respectively.The decreasing rate of ammonia nitrogen is provided with the best performance,with an average rate of 88.35%.the next are total nitrogen and total phosphorus,with the decreasing rate of 79.28% and 86.49%.2) the variance content of nitric nitrogen was not an criteria for decreasing by pond system owing to the coincidence of denitrification and nitrification.3) the corretation between the purifing effects and input rate of pollutions is negative.The results can provide a theoretical basis for rural non-point source pollution control of the same area.
2010 Vol. 8 (2): 105-110 [
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111
KANG Ling-Ling-；Zhang-Qing-Li-；Wei-Xi-Chang-；Liu-Xiao-Jiang
Review of the effects researches of soil and water conservation on sediment reduction in the middle reaches of the Yellow River
The effects of soil and water conservation on sediment reduction in the middle reaches of the Yellow River relate to the overall strategy of the river harnessing.Review of the effects researches of soil and water conservation on sediment reduction,therefore,has a significant reference value for the ongoing revision of comprehensive planning of the Yellow River.The studies of the role of water projects and soil and water conservation on sediment reduction have shown that about 510 million tons of sediment had been impounded each year during 1996-2000,including 100 million tons(19.6%) impounded by reservoirs of the main stream,120 million tons(23.5%) by reservoirs of tributary treams,60 million tons(11.8%) intercepted by irrigation system,200 million tons(39.16%) by warping dams,and 30 million tons(5.9%) by terrace.This ratio of sediment intercepting had changed in the 1980's and 1990's,the proportion of sediment intercepting of water projects had changed a little,while the proportion of water and soil conservation had reduced.The studies also show that about 300 million tons of sediment was intercepted annually by water projects and water and soil conservation in the middle reaches of the Yellow River during the 1970's-1990's,and the figure is 350 million-450 million tons now.To the effects of water projects and soil and water conservation on sediment reduction,we consider that the storm intensity is decreased in the soil erosion area of the Loess Plateau in recent years,therefore the data of measured incoming sediment cannot be used as main basis in calculation of current sediment reduction effects of soil and water conservation in revision of comprehensive plan of the Yellow River.The main reason for this is that,the changes of incoming sediment in the middle reaches of the Yellow River depends on the combination of many factors.Therefore,the effects of soil and water conservation on sediment reduction should be studied from now on and for a long time.
2010 Vol. 8 (2): 111-116 [
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117
QIN Wei-；Shu-Qing-Ke-；Zhang-Yan
Advance in researches on slop length factor in Universal Soil Loss Equation
lop length is one of topographical factors determining soil erosion intensity.As one of important indexes in the Universal Soil Loss Equation(USLE),the slop length factor(
L
) reflects the relationship between slop length and soil loss,which has been used widely and studied deeply in soil loss prediction and soil and water conservation planning.The research progress of
L
factor at home and abroad was reviewed from the relationship between slop length and soil loss、the estimating methods of
L
factor,and extraction of
L
factor in geographic information system.Finally,five main problems of
L
factor in the study and application of soil loss prediction model in China were summarized,and the research trends were put forward.
2010 Vol. 8 (2): 117-124 [
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