The black soil region of Northeast China is one of the most important grain producing areas in China. However, increasingly severe gully erosion has destroyed much farmland and reduced grain production. In this paper, a typical black soil region, located in Kedong county, Heilongjiang province of Northeast China, was chosen as the study area. Based on Corona imagery in 1965, SPOT 5 imagery in 2005 and Gaofen-1 imagery in 2015, the distributions of gullies in 1965, 2005 and 2015 were obtained by visual interpretation. Based on relief maps in 1954, MSS imagery in 1975 and Corona imagery in 1965, the land use data in 1965 were obtained. Based on TM imagery in 2005 and 2015, the land use data in 2005 and 2015 were obtained. Then by using erosion density as the main indicator, the change of erosion gully was analyzed from the perspective of land use change. The results revealed that the gully erosion in the study area deteriorated in the past 50 years. The area of severe erosion greatly increased and showed a contiguous development trend. The cultivated land was the most important type of land use in the study area, and gully erosion on the cultivated land was the most serious. With the increased gully erosion on cultivated land, grassland and construction land, forest land and unused land were constantly reclaimed. The gully density increased the most during the interchange between cultivated land and grassland. The gully density was still very high and changed greatly after cultivated land was returned to forest land and grassland in the short term. However, with the implementation of “returning farmland to forest” and the improvement of land use, the gully erosion is still developing, but it changed slower over the ten years. By analyzing gully density change in the process of land use conversion on different slopes from 2005 to 2015, we found that the development of gully erosion is prone to occur after the forest land, grassland and unused land are cultivated on higher slopes, and it is more difficult to manage gullies with higher slopes.

The initiation and development of gully erosion in the sloping farmland of black soil area are closely related to the tillage measures. Taking the Sancha River watershed in typical black soil area of Northeast China as the study area, this study used the high precision basic data provided by the geographical conditions information census to obtain the ridge direction of cultivated land and gully erosion data. The relationship between the gully density and intensity and the ridge direction angle in the cultivated land was quantitatively analyzed. Then we studied the coupling effect of the gully erosion in different ridge directions and topography. The results showed that: (1) There was an obvious trend of horizontal ridge tillage of sloping farmland; (2) The gully intensity of cultivated land was moderate in the study area; (3) The ridge angle of cultivated land was significantly negatively correlated with the gully erosion density and intensity. With the increase of the angle between contour line and ridge direction, the average gully density and intensity in sloping farmlands gradually decreased. The gully density and intensity in the horizontal ridge tillage were the largest. The linear fitting effect of ridge angle and gully density was the best, and the gully intensity was slightly worse; (4) The distribution of gullies in different ridge directions has obvious topographic differentiation characteristics. In the cultivated land where the elevation was more than 280 m, all ridge tillage cannot effectively resist the gully erosion; when slope gradient was greater than 15°, the gully intensity of cultivated land with contour ridge was the least, however, it was still higher than the gully intensity of cultivated land with every ridges on gentle slope; there was no significant difference in the effect of ridge directions on the area of the gullies on the shady slope.

In order to understand the characteristics of soil erosion in a basin and explore the applicability of the TETIS model for simulating runoff and sediment yield in the black soil region of Northeast China, the Wuyuer River Basin was taken as an example in this study. Daily runoff and sediment discharge data series from 1971 to 1987 were used to calibrate and validate the TETIS model. On this basis, characteristics of soil erosion intensity and their relationships with slope and land use types in the basin were analyzed. The results show that the TETIS model has good applicability in the Wuyuer River Basin. Nash-Sutcliffe efficiency coefficients of daily discharge and sediment ranged from 0.52 to 0.70, coefficients of determination ranged from 0.60 to 0.71, and volume errors were no more than 15%. Average soil erosion intensity was 397.2 t/(km²·a) in the basin. Slight erosion and light erosion were the dominant soil erosion types and about 90% of sediment yield was from hillslope. Average erosion intensity increased with increasing slope gradients. Slopes of 0°~5° were the main erosion area in the basin. Different land use types have different soil erosion intensities and arable land has the highest value (556.3 t/(km²·a)). Priority of erosion control should focus on the arable lands with steep slopes and low vegetation covered regions. Comparison of these simulation results with other study results in the black soil region of Northeast China demonstrates a promising future of the TETIS model for simulating runoff and sediment yields in the region. This study may provide a scientific basis for the implementation of soil and water conservation measures in the study area.

The black soil region of Northeast China is an important national commodity grain base. The Wuyuer River Basin is a typical black soil region and agricultural area in Northeast China. In this paper, a SWIM (Soil and Water Integrated Model) was constructed to study the applicability in the middle and upper reaches of the Wuyuer River Basin. Based on observed daily runoff data from a local hydrologic station and evaporating dish weather data from 1961-1997, the model was validated using multiple criteria and sites. Special attention was paid to the use of both spatial information (potential evapotranspiration) and more commonly used observations of water discharge at the basin outlet to validate the model. The applicability of the SWIM is evaluated using the Nash-Sutcliffe efficiency coefficient and the relative error of runoff. Based on this analysis, the study discusses the applicability of the SWIM model in the black soil region of Northeast China, and the associated errors and causes. The study reached three key conclusions. First, the Nash-Sutcliffe efficiency coefficients of monthly runoff and daily runoff are greater than 0.71 and 0.55, respectively; the relative error of runoff is less than 6.0%. The simulation efficiency of the SWIM for both monthly runoff and daily runoff satisfies the assessment requirements, but the simulation efficiency of daily runoff is not ideal, and the simulation is more accurate for monthly runoff than daily runoff. The Nash-Sutcliffe efficiency coefficient of monthly evapotranspiration is more than 0.81. Second, the calibrated monthly SWIM model can be used to conduct different runoff simulations and analyses in the black soil region of Northeast China. Third, the study identified structural elements of the model that may limit some uses in the black soil region of Northeast China. The simulated values of spring flood runoff were less than the observed values; and the yearlong simulated results with spring and summer floods were poor. In years with a sudden increase in annual precipitation, the simulated results of the annual runoff were several times of the measured value. However, the model can fundamentally reproduce the flow change process during the flood season. The simulation results have an important reference value to study the impact of land-use change and climate change on hydrological processes at the regional scale. It can provide hydrological information to support the integrated management of the basin water environment, as well as other watersheds in the black soil region.

In order to promote the management of soil fertility and precision agriculture effectively, provide some guidance for the soil and water conservation. A sloping cropland (0.91 km²) located in Heshan farm in Heilongjiang Province was selected as the research area,101 samples were collected by vertical and horizontal 100 m interval, for the study of spatial distribution of soil organic matter of the 0-15 cm top layer soil and the relation with soil erosion by the GIS and geostatistics math methods. The results showed that the average content of soil organic matter in typical black soil area was 4.13%, higher than the average level of Heilongjiang Province, and the proportion of organic matter content concentrated in the 3%-5%. Spatial variability of organic matter significantly which was mainly affected by soil erosion. High erosion area corresponds to low organic matter, erosion area in the corresponding medium organic matter content areas and sedimentary areas correspond to areas with high organic matter content. When the slope planted with an average gradient of 2.2°, per 1 000 t/km² soil erosion increased, accompanied with the content of organic matter will be reduced by 0.8%. The spatial variability of organic matter could be described by the spherical model, showed significantly spatial autocorrelation, further suggested that soil erosion causes the redistribution of soil organic matter. When the sampling interval is 200 m which based on the range, the interpolation of spatial distribution can accurately reflect spatial variability of organic matter content, to provide precision fertilizer sampling basis.

The black soil region of Northeast China is one of the most important grain-producing areas in China. However, increasingly severe gully erosion has destroyed much farmland and reduced grain production. In this paper, the typical black soil region of Northeast China which locates in the Nemoer River Basin was chosen as the study area. Based on Corona imagery in 1965 and SPOT 5 imagery in 2005, the distributions of gullies in 1965 and 2005 were obtained; based on relief maps in 1954, MSS imagery in 1975 and TM imagery in 1995 and 2005, the land use data were obtained in different years; then the effect of land use change on gully erosion was analyzed. The results revealed that the area of regions where gully density was greater than 250 m/km² increased from 0 km² in 1965 to 4 077.17 km² in 2005, which accounted for 37.57% of the total eroded area. From northeast to southwest of the region, the increase of gully density changed from dramatic increase to slight increase. Gully erosion on the cultivated land was the most serious, and on the grassland and marsh was the secondary, while on the forest land was the most slight. The gully density increased the most during the interchange between cultivated land and grassland, which was 600.60 m/km² and 456.08 m/km², respectively. The gully density increased 346.91 m/km² during the conversion of the forest to cultivated land. The increase proportion of cultivated land in different gully erosion zones was 29.21%-46.54%. However, the area of grassland and marsh decreased in different gully erosion zones that the proportions of decrease ranged between 27.10%-41.50% and 5.86%-12.50%, respectively.

The black soil region of Northeast China is one of the most important grain bases in China. In recent years,severe soil erosion in this region has been a threat to agricultural production. Soil and sediment transport models are important tools that predict soil erosion and sediment yield under different conditions. However,other models are rarely used except for the RUSLE and slope version WEPP models in the black soil region of Northeast China. The Water and Tillage Erosion Model and Sediment Delivery Model （WaTEM/SEDEM） was developed as a spatially distributed soil erosion and sediment delivery model and is similar to the （R）USLE model. It can spatially model soil erosion and sediment deposition rates and soil redistribution patterns. In this study,the WaTEM/SEDEM model was applied to 25 dam-controlled catchments in Baiquan county in the black soil region. Transport capacity coefficients （K_TC） in the model were first calibrated using sediment yield data of 14 dam-controlled catchments and validated using the remaining 11 dam-controlled catchments. Therefore the optimal K_TC-values of the WaTEM/SEDEM model were 0.38 and 0.55. The correlation coefficient values of sediment yield（SY） and area specific sediment yield （SSY） between observed and predicted values were 0.95 and 0.34,respectively. The simulated results of sediment yield using the WaTEM/SEDEM model were good and the simulated mean sediment delivery ratio （SDR） for the 25 dam-controlled catchments was 0.32. Finally,the calibrated WaTEM/SEDEM was applied to the Qixin dam-controlled catchment. Simulated results showed that the mean soil erosion rate is 351.2t/(km²·a). Erosion rates vary with land use types and slops. Comparison of this study to published results demonstrates that WaTEM/SEDEM gives satisfactory result for the study region. This study provides a basis for the implementation of erosion control measurements in the black soil region,Northeast China.

Black soil area of Northeast China is one of the most important marketable grain bases in China, but serious soil loss resulted in crucial challenge to the marketable grain production. This paper, supported by Remote Sensing and Geographic Information System, chose typical black soil area of Northeast China which is located in the scope of Wuyuer and Nemoer river basins as a study case and took SPOT 5 as data source, obtained gully distribution data in 2005. Based on the gully distribution data, the gully erosion status of the study area was evaluated. Using 1:50000 relief maps as data source, DEM was obtained by interpolation and then 11 topographic factors related with the gully formation were extracted. Based on gully data and eight no multi-colinearity topographic factors, the Logistic regression model was built. With the model, the risk of the gully erosion was evaluated and the risk classification evaluation of gully erosion was also done. The results showed that the total number of gully was 14184, the gully density was 322.11 m/km² and the area of eroded cultivated land was 100.36 km² in the study area. The risk map of gully erosion evaluated by Logistic model was identical with gully distribution in the study area. The high danger regions were mainly located in the northeast of Baiquan, middle of Kedong, east of Keshan, north of Nehe, middle of Beian and west of Wudalianchi. The low danger regions were mainly in the northeast low hilly region, the southwest plain and the bank region of Nemoer and Wuyuer rivers. When taking the value of 0.4 as gully dividing point, 73% of the gullies in the study area were formed in the high risk regions. In a word, the evaluation result can reflect the risk status of gully erosion. Furthermore, with the aid of the map and table of risk classification evaluation of gully erosion, this paper can get the area, pattern and characteristics of different risk classification of gully erosion. Based on the results, it can identify the serious erosion area and provide the scientific suggestion for the erosion prevention and management.

Black Soil Area of Northeast China is one of the most important marketable grain bases in China, but serious soil loss bring the crucial challenge to the marketable grain production. In this paper, supportad by Remote Sensing and Geographic Information System, taking typical Black Soil Area of Northeast China which is located in the Wuyuer River and Nemoer River basins as study area, based on USLE model and SPOT 5 imagery, the amount of soil erosion on hillslope and gully distribution data in 2005 were obtained respectively. Then the coupling relations between hillslope erosion and gully erosion of different grades, slopes, aspects and so on were analyzed. The results showed that slight erosion and light erosion were the main hillslope eroded area in the study area. Gully erosion was much serious and had a great potential for development. When the slope was below 5°, slope was the key factor causing gully erosion. However, when the slope was above 5°, slope was no more the important factor causing gully erosion. In addition, it showed that the amount of hillslope erosion on sunny slope was higher than shady slope, but for the gully erosion, aspect was not the key factor affecting the formation of gully erosion in Black Soil Area of Northeast China. In areas with an erosion intensity smaller than 2500 t/(km²·a), erosion gully density increased with the amount of hillslope erosion. However, When it is greater than 2500 t/(km²·a), the erosion gully density would be comparatively stable.

Seasonal runoff-sediment dynamics and its controlling factors were studied in an agricultural watershed in the black soil region of Northeast China. Daily sediment and discharge data from 1957 to 1989 (except for 1961 and 1962) was used to investigate runoff-sediment dynamics, and the observed data shows that the discharge patterns are dominated by runoff from July to September, which accounted for about 64.7% of annual discharge; fluctuations in suspended sediment concentration (SSC) are markedly different from discharge fluctuations; and SSC in the snowmelt season (April) and late June to July is conspicuously higher than at other periods of the year. One concept was proposed to isolate the individual effect of each controlling factor on SSC from their joint effects and the preliminary analysis shows that: (1) high SSC in April is mainly dominated by freeze-thaw, and high SSC in July is dominated by intensive rainfall erosivity rather than volume of discharge; (2) an increase in rainfall erosivity increases SSC whether or not a field is covered by crops; (3) the effect of rainfall erosivity with increasing SSC in July is larger than the reduction effect from crop cover. The results reveal that the concept of isolating an individual effect from the joint effect played by multiple controlling factors on SSC provides potentially an efficient and effective way for evaluating land use and management practices in a new area with limited data.

论文在GIS技术支持下，依据环境经济学原理，利用2005年的坡面侵蚀和沟蚀数据，对黑龙江克拜东部黑土区由土壤侵蚀造成的直接经济损失进行了定量估算；在此基础上，将黑土区土壤侵蚀经济损失与西北黄土高原地区、北方土石山区、西南岩溶区进行了对比分析。结果表明：研究区2005年由土壤侵蚀所造成的直接经济损失总价值约为9414.20×10⁴元，占当地种植业总收入的17.19%，部分乡镇损失价值占种植业收入的1/4以上。将黑土区土壤侵蚀经济损失与我国其他水蚀区对比发现：东北黑土区虽以轻度侵蚀为主，土壤侵蚀量固然不能与黄土高原相提并论，但由于黑土腐殖质含量高、养分丰富，轻度侵蚀即可造成严重的养分流失，其单位面积土壤侵蚀直接经济损失价值是黄土高原的3～4倍。

With the deepen understanding of soil erosion at spatial scale, gully erosion has been attracted more interest than ever. The black soils in Northeast China is one of the important bases for food supplies, but now the soil erosion, especially the fast expansion of gully erosion, has been one of the most important reasons for soil degradation. This paper made use of Global Positioning System (GPS) to measure the shape characteristics of ephemeral gully(EG), the platform of Geographical Information System to calculate the status of EG erosion, and analysis the geomorphic factors to determine the occurrence of EG erosion. The results show that the distribution density of EG is 0.56-0.93 km/km², its annual erosion modulus is between 118 m³/km² and 199 m³/km², and the proportion of the destroyed area by EG come up to 0.11%-0.19% of the watershed area. These indicated that gully density has reached middle and intensity degree erosion, being in rapid growth stage. It was also found that the threshold catchment area of EG in the study area is larger than that in the Loess Plateau, whereas the threshold slope smaller than that in the Loess Plateau. Meantime, the analyses indicated that the volume of ephemeral gully is determined mostly by its length that is mostly determined by the length of watershed. This means that mostly the length of the watershed determines the volume of ephemeral gully, which undoubtedly provides a referred thought for the construction of gully model.

By using fixed field profile experiment and Rare Earth Elements (REE) tracer technique, we studied the course of soil erosion on two parcels of black soil in Jingyue Economic Development District, Changchun City, and Yongji County, Jilin City, Jilin Province. The stable REE were used in tracing soil erosion, sedimentation, distribution and the possibility of erosion process in black soil area, soil erosion and the relative soil erosion of different parts of the slope were worked out, and effect of rainfall on the slope of soil erosion process described successfully. Experimental method is to trace elements evenly mixed with the soil, laid on the slope of the different terrain under test site, so that the entire process of rainfall runoff silt be done together with the relocation of its acquisition of sediment samples. The content of REE was tested in neutron activation method. Then soil erosion and the relative soil erosion of different parts of the slope were calculated according to concentrations of trace elements added into different parts of the slope and sediment collected after rainfall respectively. The experiment results show that the rate of soil erosion on the slope increases with rainfall period. Rain duration and slope are the two factors influencing soil erosion by affecting the movement speed and direction of soil particles. This paper concluded that: 1) artificial rainfall and natural rainfall field experiment showed that the slope erosion often turned around 10 min after rainfall, after that, the slope erosion rate became more stable, larger with the time increase. It could be considered that 10-15 min after rainfall is the best observation period for slope soil erosion study; 2) soil erosion occurred mainly in the middle and lower slope part (marked with Nd, Sm and Eu in the slope) in 7?-12 ? slope, which indicated that soil erosion is closely related to the slope and bands structure; and 3) the adoption of tracer REE for quantitative determination of the relative erosion in different terrain positions can provide an alternative method for vertical soil erosion. This method can not only monitor slope relative erosion in different terrain positions accurately, but also describes their distribution character objectively. Generally, the paper reveals the law of slope soil erosion intensity and provide new methods for the black soil erosion study.

Ephemeral gully erosion can be a major sediment source serving as main conduits to convey runoff and sediment from most farmland. Ephemeral gully erosion is similar to but differ from both rill and classical gully erosion.But ephemeral gully erosion is often overlooked, and it is also not estimated with rill-interrill erosion prediction models such as the Revised Universal Soil Loss Equation. Soil erosion is increasingly severe in Northeast China with black soils, in which ephemeral gully erosion is an important type of water erosion. However, the existing literature indicated that little research on ephemeral gully erosion has been done in this area.In this paper, ephemeral gully erosion was investigated in spring and summer of 2005 in black soil regions of two small catchments on Heshan Farm of Heilongjiang Province.The aim of the study was to present the characteristics of ephemeral gullies and their seasonal discrepancies and controlling factors. The results show that soil losses due to ephemeral gully erosion fluctuate along the slope, and the high erosivity belts alternate with the low belt.There are also great differences in the morphology, the erosion intensity and controlling factors of ephemeral gully erosion between spring and summer. Ephemeral gully erosion in spring is mainly resulted from snow storm and is significantly influenced by freeze-thaw and snowmelt runoff. Ephemeral gully erosion in spring is slightly severer than that in summer. Ephemeral gully erosion was caused by storm. Compared with that in spring, ephemeral gullies in summer were shorter and shallower, but wider due to the storm characterized by high intensity and low duration. Furthermore, the depth and distribution of ephemeral gully are significantly influenced by tillage practice and crop type, especially in summer.

In this study, short-term gully retreat was monitored from the active gullies selected in representative black soil area, using differential GPS. With the support of GIS, multitemporal digital elevation models (DEM) were constructed in light of the data collected by GPS and used for further analysis. Based on the analysis of multi-temporal DEM, we discussed the erosion-deposition characteristics of a gully and a developing model for black soi l gully area of Northeast China was proposed. The results are: (1) The analysis of the monitored gully data in 2004 indicated that the retreat of gully head reached more than 10 m, gully area extended 170-400 m², gully net eroded volume 220-320 m3 and gully erosion modulus 2200-4800 t·km^-2·a^-1. (2) Compared with the mature gully the initial gully grows rapidly, and its erosion parameters are relatively large. The erosion parameters have not only to do with flow energy, but also with growth phase. (3) There are significant seasonal differences in gully erosion parameters. The extension of gully area and width dominates in winter and spring without marked net erosion while changes mainly occur in gully head expansion and net erosion in rainy seasons. (4) It is remarkable for freeze-thaw erosion in the black soil area of NE China. The gully wall of SG2 extended 0.45 m under freeze-thaw effect in 2004, and the distance of gully head retreated maximally 6.4 m. (5) Due to freeze-thaw action and snowmelt, gully is primarily in the interior adjustment process in winter and early spring. There are much more depositions compared with that in autumn, which can almost happen throughout the gully, while erosion mostly occurs near head, esp. for gullies having a relatively long history of development.

Gully erosion is an important part of the soil erosion process and their occurrence and development may cause serious problems to a region’s agricultural sustainable development.Nowadays,wide and deep gullies can be commonly observed in Black Soil Region of Northeast China,owing to unreasonable land use option and human activities in the past 100 years.Some new technology such as Global Position System(GPS),phtogrammetry,and so on,is often used to study the process of gully development at local scale.But the research of gully distributing patterns at larger spatial scale is rarely reported.In this paper,taking black soil region of the eastern Kebai as a case study area,the SPOT-5 high resolution image was used to study the gully types,image character and their distribution on a regional scale.Since more active gullies have sparser vegetation cover,this study classified the gullies into three types(active gully,semi-active gully and stable gully) by their stage of development which can be estimated by fractional vegetation cover at gully bottom.The Normalized Difference Vegetation Index(NDVI) was used to calculate the average fractional vegetation cover of gullies.The image character of the erosion gullies is also described in detail.The gully density maps were made to show the spatial distribution character for each type of gullies.This study revealed that gully distribution is influenced by many factors.Gully density first increases sharply when slope degree increases,then decreases when the slope angle goes beyond 8 degree.Gully distribution is not uniform on each slope aspect,and highest gully density occurs at west and southwest side of the slope.Gully density also varies as altitude increases. It reaches the peak when altitude ranged from 210m to 280m.There is a great difference in gully density on two sides of the ridge between Runjin,Shuangyang and Tongken river systems.Most of the erosion gully occurs on the east side of the ridge,owing to the ridge migration in the natural process of landform evolvement.This result revealed that at local scale,gully occurrence is often influenced by such factors as slope steepness,vegetation cover,farm management,etc.,but at regional scale,the natural process of landform evolvement can not be negligible and may become a significant factor on gully distribution.This result indicates that constructing more reservoirs and dams across valleys is an effective way to control soil loss in Black Soil Region of Northeast China,as it can raise the base level and control the velocity of running water.

Gully erosion can be widely observed on cultivated slopes in Black Soil Region of Northeast China. Today, vast areas have been permanently ruined by erosion gullies. In many places, the farmland has been deeply incised, leading to loss of arable land as well as fertile black soil. The erosion gullies in Black Soil Region also affect farming activities and threaten the villages. Global Position System (GPS) and photogrammetry are often used to study the process of erosion gully development in a small scale. However, the research of gully distributing pattern and its variation on a larger spatial-temporal scale is rarely reported, owing to lack of high-resolution satellite imagery in the earlier time. Nowadays, the declassified images from spy satellites are an important addition to the record of the Earth's land surface back to the middle stage of the 20th entury. In this paper, taking eastern Kebai area as an example, based on field investigation of erosion gullies, the CORONA images of 1965 acquired by spy satellites of USA and SPOT-5 images of 2005 were used to extract erosion gully and land use information. The interpretation signs of erosion gully were presented and the image character for different type of gullies was described in this paper. With the support of GIS software, the image interpretation was conducted to obtain two stages of gully distribution maps, then the line coverage of erosion gullies were interpolated to gully density map using Arc/info9.0. Based on those work, the spatial distribution of erosion gully development from 1965 to 2005 and its regional variation were analyzed. This study revealed that from 1965 to 2005, the extent of high gully density area enlarged and tends to be onnected with each other in eastern Kebai area. But the spatial distribution of erosion gully development is not uniform in the study area. There is a great difference on the gully density change along the ridge of Tongken River, which is related to the natural process of landform evolvement. The study also showed that the gully density increased sharply when forest land changed into arable land or grassland. The unreasonable land reclamation and land use change in Black Soil Region of Northeast China during the past decades may be an important factor in the process of gully formation and development. This study can provide data for research of land degradation process, soil and water conservation and agricultural sustainable development in Black Soil Region of Northeast China.

The theory of geomorphic threshold has been widely applied in study of predicting the area of ephemeral gully incision. Based on the measurement in field and relief map, this paper got the coefficient (a) and (b) in threshold model S=aA^-b (where S is local slope, A is upslope drainage area), and verified whether the gully incision formula used by Moore is suitable in study area. The analysis showed that the threshold value (a) and exponent coefficient (b) are 0.1161 and -0.4457 respectively for gully, 0.0631 and -0.4643 respectively for ephemeral gully; and that gully incision formula used by Moore is not suitable in study area. Compared with the distribution of ephemeral gully in field, it is found that the prone area predicted by threshold model is fairly well consistent with the actual ephemeral gully distribution. Meanwhile, it was found that the bigger the bvalue in threshold model, the more unsusceptible the prone area to the change of threshold value, vice versa, which is approved by the prone area of gully incision. These provide primary design guidance for local soil and water conservation.

The black soil resource of China is famous for its fertility, high organic content, and the best applicability for cultivation. The long-term human activities of over-reclamation and irrational cultivation resulted in water and soil loss on a large scale. Especially the erosion gullies incise the land surface, nibble the field, wash out the fertile soil and degrade the efficiency of the large cultivator. Erosion gully research is one of the important parts of soil erosion subject. In this paper, based on the Remote Sensing and Geographical Information System, taking Kebai area as a case study, using density of erosion gully as the main indicator, the authors analyzed the dynamic change of the erosion gully density, the variation of the erosion gully on different altitudes, slopes and aspects, as well as the variation in different morphogenetic regions, and finally revealed the rule of temporal and spatial variations of erosion gullies in recent 50 years in typical black soil area of Northeast China.

The paper investigates the distribution depth of cesium-137 and erosion rate of black soil using cesium-137 tracer, discusses the influence of soil erosion on the contents of particle size, organic matter, specific gravity and water quantity, nitrogen and phosphorus in the tillage layer of 0～20 cm on a typical slope. Cesium-137 activities in the profile, mainly distributed in the layer of 0～25 cm deep, are in the range of 1246.05±85.90 Bq/m² to 1499.45±101.73 Bq/m² .So,the annual soil erosion rates can reach 3033.6-3940.3 t/km² within the last 40 years,which have reached the moderate erosion level. It is the right time to pay enough attention to the black soil erosion. Also, it is completely feasible to investigate the erosion rate of black soil using cesium-137 tracer method. The slope length and gradient have distinctly effects on soil erosion intensity. The trend that the soil particles are becoming increasingly coarser is also obvious. The percentage of sand and clay declines gradually, and silty sand increases from top down to bottom of the slope. Moreover, organic matter （OM） is also in the trend of increase from top to bottom of the slope, but the contents of OM in both erosion and sedimentation profile （2.56～3.10%） are markedly lower than that in original black soil. The specific gravity increases and water content declines in the erosion profile. Furthermore, the phenomenon that the contents of nitrogen and phosphorus decline is clear. Both of the quick degradation of black soil quality and agricultural non-point source pollution should be paid attention to by all circles. Due to the geographical location of black soil belt and its relative location to Pacific and Eurasia, both of frequency and intensity of wind taking place in spring every year are high. So, the above-mentioned soil erosion intensity is the result of wind erosion and water erosion. The percentage of soil quality degradation induced by water erosion and flux of main agricultural non-point source pollutants should be further studied.