中国水土保持科学
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2018 Vol.16 No.5
Published 2018-10-30
1
LI Jinlin, WEI Jie, HE Xiubin
Stability analysis of different scale soil bunds on purple soil sloping farmlands
[Background]
Bunds are embankments constructed across the slope and along the contour, and play a key role in controlling soil erosion on sloping farmlands. Recently, it is unclear yet of the relationship between soil bund stability and scales. The aim of this work is to provide a basis for soil bund planning and design in the purple sloping farmland consolidation and lower-yield field reconstruction projects in the Three Gorges Reservoir area and even the upper Yangtze River, by revealing the purple soil bund stability response to scales.
[Methods]
We carried out field investigation, laboratory test, simulation and response surface analysis to reveal the stability of soil bunds under different height and slope conditions. We defined 4 levels of height (0.8, 1.0, 1.2, and 1.4 m at intervals of 0.2 m) and 4 levels of slope (50°, 60°, 70°, and 80° at intervals of 10°), a total of 16 soil bunds. The limit equilibrium analysis was adopted to calculate the stability coefficients, and the response surface analysis was adopted to build the model of purple soil bund stability responses to the bund size.
[Results]
The minimum of stability coefficient was 3.526, which indicated that all soil bunds defined in the present study were stable. When the outside slope was constant, the soil bund stability coefficients displayed a nonlinear reduction with the height increasing; however, when the height was constant, the soil bund stability coefficients decreased generally along with the outside slope, the average reduction was greater than 10% at each increasing interval under these two changing patterns. Overall, both the height and the outside slope had significant influences on the stability of soil bunds (
P
<0.01), while the interactive effect was not significant. Regression equation fitted by height, outside slope and their quadratic terms of soil bund can be used for describing the relationship between stability and scales perfectly, the adjustment determination coefficient and variation coefficient were 93% and 5.88, respectively. The potential sliding surface of soil bund was characterized by a shear resistance force greater than the moving shear force. With an increasing of the base shear mobility force and the right side normal force, the soil bund stability coefficient showed a decreasing trend, with no noticeable change trend along with the base normal force and the right side shear force change.
[Conclusions]
The reasonable scale is 1.0~1.2 m of height and 60° of outside slope while considering purple soil bund stability features, slopping farmland conditions and ease for farmers to cultivate.
2018 Vol. 16 (5): 1-9 [
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561
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10
ZHANG Shuai, DING Guodong, GAO Guanglei, ZHAO Yuanyuan, YU Minghan, BAO Yanfeng, WANG Long
Effects of straw checkerboard barrier in different setting years on ecological restoration
[Background]
According to the fifth China desertification and sandy status bulletin, China's desertification land accounted for 27.2% of the total land area, while the sandy land accounted for 17.93%. In the prevention and control of wind erosion process, engineering measure is one of the important measures. Due to simple layout and adaptability to various environments, straw checkerboard are widely used to control wind-blown sand in China. Most of the existing researches focus on windproof capacity, while there is less research on ecological restoration of sandy land.
[Methods]
To study the influence of the straw checkerboard on ecological restoration after their deployment, we conducted a long-term study of the sandy land management in this area over a period of many years. The layers of soil were sampled in plots with straw checkerboard set by 1 year, 2 years, 5 years, and 10 years, respectively, and each 10 cm was for a layer, totally 4 layers for 40 cm soil. The soil quality was carried out by drying method. The analysis of soil particle size was carried out by laser particle size analyzer, and the vegetation restoration was analyzed by pixel method. All data were analyzed by SPSS for statistical analysis.
[Results]
1) There was a positive correlation between water quality and straw checkerboard setting years(
P
<0.05), the mass moisture content of sand plots with laying 1 year, 2 years, 5 years, and 10 years straw checkerboard was 1.11,1.14,1.36,1.47 times, and the 0-10 cm, 10-20 cm, 20-30 cm, and 30-40 cm soil layer soil were 1.46,1.26,1.83, and 1.48 times than bare sand. The surface soil moisture content showed an increasing trend after the sand barrier set 1 year, and the deep soil moisture content increased obviously after the sand barrier set 5 years. 2) The soil particle size of the soil layer after setting straw checkerboard showed the increase of the clay and grain, and the decrease of the gravel content. The clay content increased by 2.5 times and the grain content increased by 1.98 times, sand content decreased by an average of 5.25%. Sand surface formation of 3-5 mm crust, some areas have begun to appear the presence of loam. The flow sand was basically fixed, the wind erosion was less, and the surface micro-terrain was more stable. 3) The germination of the pioneer plants appeared after sand barrier set 1 year, and the stable herbaceous vegetation community formed after sand barrier set 5 years, at the same time, the shrub plants appeared, the shrub community was formed after sand barrier set 10 years, and the herbaceous plants subsided. The vegetation coverage reached 59.83%. At the same time, we conducted the sample analysis of sand plot that closured 10 years, and found that the total coverage was more than 90%, and there was hardly any sand on the surface of the soil.
[Conclusions]
Straw checkerboard plays a major role in sand control, it can be effective in improving the surface microenvironment, providing favourable conditions for the restoration of vegetation, further cooperating with vegetation, improving soil and promoting ecological restoration.
2018 Vol. 16 (5): 10-15 [
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16
ZHENG Zhe, ZOU Jin, PAN Feng, ZHANG Daiqing
Spatio-temporal variation characteristics of rainfall erosivity during 1961-2010 in Nu river basin
[Background]
One of the main factors of soil erosion is rainfall. Rainfall erosivity is an important indicator for studying soil erosion due to rainfall, and it is one of the important parameters of many soil erosion models. Correct calculation of rainfall erosivity has important practical significance for soil erosion and soil and water conservation in the study area.In order to study the temporal and spatial distribution characteristics of rainfall erosivity in the Nu river basin. Using the daily rainfall data of 6 weather stations in the Nu river basin from 1961 to 2010.
[Methods]
The methods used in this paper mainly include calculating the rainfall erosivity of the basin by using the daily rainfall erosivity model, Mann-Kendall nonparametric statistical method for the mutation calculation, and interpolating the rainfall and rainfall erosivity of the basin using the inverse distance weight interpolation method in Arcgis 10.2 software. The temporal and spatial distribution of force. In order to provide a certain reference for soil and water conservation work in Nu river basin.
[Results]
The results show that,the average annual rainfall of Nu river basin was 774.93 mm, and the average annual rainfall erosion force was 1 842.45[(MJ·mm)/(hm
2
·h)]. Among them, the rainfall changed suddenly in 1978, and the rainfall erosion force was 1966. In 1973 and 1976, the rainfall occurred, and the rainfall and rainfall erosion force in the basin showed a trend of high in the southeast and low in the northwest. The annual distribution of rainfall erosion force was mainly concentrated in summer, accounting for 48.71%, and the smallest in winter, accounting for only 5.9%.
[Conclusions]
The spatial distribution of rainfall and rainfall erosion force in the Nu river basin is similar, and the impact of erosive rainfall on rainfall erosion force is greater. The research results can provide a certain technical reference for soil and water conservation and ecological restoration in the Nu river basin.
2018 Vol. 16 (5): 16-22 [
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330
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23
AI Ning, LIU Guangliang, ZHU Qingke, LIU Guangquan, QIANG Fangfang
Rainfall threshold while runoff occurs on loess slope at northern Shaanxi based on the coupling relationship between antecedent soil moisture and rainfall
[Background]
Antecedent soil moisture and rainfall (ASAM) are the main influencing factors on runoff occurring in a loess slope at northern Shaanxi. There have been many models for the coupling relationship between runoff and factors of antecedent soil moisture and rainfall, but they are based on regression analysis, their practicality and universality are limited, especially on the forecast of runoff erosion.
[Methods]
Based on the basic principle of runoff occurring under excess infiltration and introduced 2 indicators of antecedent soil moisture and rainfall, the model for the rainfall threshold while runoff occurs for a loess slope was deduced based on the coupling relationship between antecedent soil moisture and rainfall. Then according to this model and combined with the measured soil moisture, the rainfall threshold while runoff occurs was simulated, calculated and analyzed during the drought year, normal year and wet year in the typical vegetation community in the Wuqi county of northern Shaanxi loess region.
[Results]
1) Rainfall thresholds while runoff occurred differed significantly between wet years and dry years as well as normal years in the loess slope of northern Shaanxi. The required rainfall for runoff occurring in wet years was little and the theoretical rainfall for runoff occurring was the lowest at 5.6 mm. There were no significant difference in rainfall thresholds for runoff occurring between dry years and normal years, but rainfall required in dry years for runoff occurring was large. 2) The minimum rainfall for runoff occurring at different vegetation types was different, while the rainfall threshold for runoff occurring in
Pinus tabulaeformis
forest land was the least, i.e., the runoff in the
P. tabulaeformis
forest land easily occurred. The rainfall for runoff occurring in
Hippophae rhamnoides
forest land was the most, i.e., it was difficult for
H. rhamnoides
forest land to have runoff occurring. There was a significant difference in the rainfall thresholds for runoff occurring between these two vegetation types. 3) When vegetation and other topographical conditions were the same, the lower the rainfall intensity was, the longer the time required for runoff occurring was; the more the amount of rainfall loss was, the longer the time required for runoff occurring was. 4) When the surface soil of a slope had high saturated water content and the antecedent soil moisture content was small, the field rainfall required for runoff occurring was high; when the soil density on a soil slope was large, the rainfall required for runoff occurring was also large. When the depth of soil infiltration on the slope surface was shallow, the amount of rainfall required for runoff occurring was also small.
[Conclusions]
Studying the coupling relationship between the ASMA and the critical rainfall threshold of loess slope runoff is of great significance to prevent soil erosion and to effectively utilize water and soil resources in this area.
2018 Vol. 16 (5): 23-29 [
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30
HUANG Yongchao, CHEN Xiaoyan, HAN Zhen, XING Hang, LI Yanhai
Quantitative calculation of matrix infiltration and preferential infiltration in the tillage layer of purple soil
[Background]
The soil erosion of purple soil sloping cultivated land in the Three Gorges Reservoir area is serious, and the annual soil erosion amount is as high as 9 854 t. The infiltration properties of purple soil and its influencing factors have been widely studied, but there are few reports on the quantitative calculation of the matrix and preferential inflow of purple soil. In view of this, the purple soil in sloping cultivated land was chosen as the research object, and the characteristics of soil matrix and preferential inflow in purple soil plough layer were quantitatively discussed, which provided a scientific basis for the mechanism of infiltration process in purple soil plough layer.
[Methods]
Taking the purple soil slope farmland in Beibei, Chongqing as the research object, the soil matrix and the total infiltration rate of the purple soil plough layer were quantitatively measured by using the surface ring infiltration meters, and then the preferential infiltration rate was calculated. The variation of soil matrix infiltration rate to preferential infiltration rate of this area with time was analyzed. Philip infiltration model and Kostiakov infiltration model were used to fit the matrix infiltration process measured at different test sites.
[Results]
1) The initial infiltration rate of soil matrix infiltration is 8.38 to 32.66 mm/min, the stable infiltration rate is 3.15 to 4.2 mm/min, the average infiltration rate is 3.62 to 6.26 mm/min. The initial infiltration rate of preferential flow is 37.01 to 42.34 mm/min, the stable infiltration rate is 0.04 to 1.59 mm/min, the average infiltration rate is 2.31 to 9.67 mm/min. 2) The cumulative infiltration of soil preferential flow in the purple soil layer of the study area is 0.6-1.5 times that of the soil matrix infiltration. The ratio of matrix infiltration rate to preferential infiltration rate is 0.3-0.5 in the initial infiltration stage; the ratio of matrix infiltration rate to preferential infiltration rate is gradually increasing during the process of infiltration. After reaching the stage of steady infiltration, preferential infiltration rate decreases, the ratio of matrix infiltration rate to preferential infiltration rate is 1.5-16.5.
[Conclusions]
Soil matrix and preferential flow played the same important role in the hydrological process of purple soil slope farmland. The fitting results of soil matrix infiltration rate were good, and the determining coefficient was above 0.93.The results of this study may provide a scientific basis for studying the mechanism of infiltration process of purple soil.
2018 Vol. 16 (5): 30-39 [
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391
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40
LI Long, JIANG Lina, BAI Jianhua
Multi-scale correlations between spatial variability of soil organic carbon and its influencing factors in semiarid zone
[Background]
Soil carbon pool is the largest carbon pool in terrestrial ecosystem, and its dynamic change and the distribution of reserve play an important role in the quality of soil. Therefore, the accurate estimation of soil organic carbon (SOC) storage, analysis of the spatial variability and uncovering the main factors that control the spatial distribution of SOC may provide basic data and theoretical basis for regional ecological construction and scientific and rational use of land resources.
[Methods]
This research was conducted in Aohan banner of Chifeng city, Inner Mongolia, based on soil survey data. The scale effects of spatial variability in surface SOC (0-20 cm soil depth) was studied by multi-scale sampling of small watershed, medium region and county scale. The classical statistics and geostatistics with software GS+7.0 ArcGIS10.0 were used to analyze the spatial variability of surface SOC content.
[Results]
1) The mean contents of SOC at the county, medium region and watershed scales were 7.49, 7.57 and 7.54 g/kg, respectively. The change range of organic carbon content in the 3 scales was found to be between 1.43-19.48, 1.31-19.89, and 1.23-19.95 g/kg, respectively. There was no significant difference in the surface soil organic carbon fractions between the 3 scales, all of which were at a relatively low level. SOC contents showed a moderate spatial correlation with the range between 980 m and 2 100 m at the 3 scales.2) The Gauss model had better fitting effect on the soil organic carbon fraction of the small watershed scale, and the spherical model had better effect on the soil organic carbon content in the county and middle scale. The model fitting residuals was relatively small (1.96-2.43), and the determination coefficient was between 0.50-0.75, which showed that the selected model described the spatial structure characteristics of soil organic carbon content on each scale more accurately. The
C
0
/(C
0
+C)
reflected the variation characteristics of soil organic carbon data, and
C
0
/(C
0
+C)
on the 3 scales was between 27.66%-36.61%. It shows that the soil organic carbon in each scale was in the medium intensity spatial correlation. With the study scales enlarging, the spatial autocorrelation scale of SOC increased gradually. There was a significant difference of the relationship between influential factors and SOC content at different scales.3) Soil and vegetation presented the greatest influence on the distribution of SOC content at county scale, and vegetation and elevation showed the greatest influence on the distribution of SOC content at medium region scale, and elevation and slope had the greatest influence on the distribution of SOC content at small watershed scale.
[Conclusions]
The results may help us to gain a better knowledge of the spatial distribution pattern of SOC and the dominant factors that impact this pattern at different scales.
2018 Vol. 16 (5): 40-48 [
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550
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49
YI Sangui, CAI Wentao, LAI Liming, ZHOU Jihua, ZHANG Xiaolong, GUAN Tianyu, JIANG Lianhe, ZHENG Yuanrun
The characteristics of soil water infiltration on the abandoned croplands in soft hill and hard ridge of the Ordos Plateau
[Background]
The Ordos Plateau is a typical arid and semi-arid grassland area. Over reclamation of grassland is one of the main causes for shrub encroachment and desertification in the Ordos Plateau. Soil moisture is a key factor for restoration of abandoned cropland in arid and semi-arid areas. The characteristics of soil water infiltration are closely related to soil moisture in different soil layers, and the soil water infiltration in different soil layers can affect vegetation succession process in abandoned croplands. In order to better understand changes of soil water infiltration with vegetation succession in abandoned croplands, the characteristics of soil water infiltration on abandoned croplands with different abandoned years in soft hill and hard ridge in the Ordos Plateau were investigated.
[Methods]
In soft hill and hard ridge of the Ordos Plateau, croplands with different abandoned years (12 kinds of abandoned cropland) were selected, and double ring infiltration device was used to measure soil infiltration parameters, and Kostiakov-Lewis model was used to simulate soil infiltration process of these abandoned croplands with different abandoned years.
[Results]
1) In soft hill, the initial infiltration rate decreased over abandoned years, but it did not show significant difference among different abandoned years. The final infiltration rate and the total infiltration height declined over abandoned years, reached the lowest values in 15th year, and then increased over abandoned years, and the final infiltration rate and the total infiltration height showed a significant decrease in 10th year. 2) In hard ridge, the initial infiltration rate, the final infiltration rate and the total infiltration height were positively correlated with abandoned years before it reached split point in 10th year (for the initial infiltration rate) and 15th year (for the final infiltration rate and the total infiltration height), thereafter declined with further increase of abandoned years, and there were significant increase from 10th to 15th year. 3) In soft hill, there was no obvious change in a value over abandoned years, but K value showed a decreasing trend with the increase of abandoned years. There was no significant change in a value over abandoned years, K value increased with the increase of abandoned years, reached the highest value in 10th year, and then declined. K value showed a significant increase from 10th year to 20th year in hard ridge.
[Conclusions]
With increase of abandoned years, the soil water infiltration decreased and soil water might increase in shallow soil layers in soft hill; soil structure and soil water infiltration capacity were improved in hard ridge. These results implied that the water and soil preservation capacity gradually improved in croplands over abandoned years without human disturbance, and the results may provide scientific basis in decision-making for restoration of abandoned croplands in Ordos Plateau.
2018 Vol. 16 (5): 49-56 [
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57
LI Hao, WEN Anbang, LIU Tao, LI Ting
Spatial distribution of
137
Cs reference inventory in Sichuan province using geographically weighted regression Kriging combined with
137
Cs reference inventory mathematical model
[Background]
Use of the fallout radionuclide
137
Cs as a tracer recently has been widely employed for the assessment of soil erosion. In the
137
Cs method, the magnitude of the rate of soil erosion is estimated by comparing the
137
Cs inventory of the sampling points with the local reference inventory, therefore, it is of extreme importance to determine the
137
Cs reference inventory obtained from a local stable site neither erosion nor deposition occurred while studying soil erosion using this tracing technique.
[Methods]
Based on the measured data from 147 meteorology stations and the
137
Cs fallout model derived by Walling & He, a case study on the application of geographically weighted regression Kriging interpolation (GWRK) combined with principal component analysis (PCA) for the assessment of the spatial distribution of the
137
Cs reference inventories was undertaken at Sichuan province, Southwest China.
[Results]
1) Using PCA, the transformation process to turn the influence factors of longitude, latitude and precipitation into 2 principal component variables were educed. This measure not only maintained the 90% information of original data, but also decreased the multicollinearity among the variables significantly. It was the basis for the further interpolation of
137
Cs reference inventory. 2) With the principal components as input variables, the spatial distribution of the
137
Cs reference inventories at Sichuan province were obtained by 3 different methods:the GWRK method, the ordinary Kriging (OK) method and global regression Kriging method (GRK). In the meantime, some indicators such as Mean Absolute Error (MAE), Root Mean Square Error (RMSE), Mean Absolute Relative Error (MARE) were calculated for evaluating the accuracy of different interpolation results. In terms of the interpolation results, taking into consideration of various influence factors and their spatial non-stationarity, the GWRK method had better accuracy compared with the other methods. Furthermore, this simulation result is in exactly agreement with those of the measurement.
[Conclusions]
This study reveals the regulars of space distribution of
137
Cs reference inventory and the effect of different factors. Additionally, the results of this study also demonstrate that it is obviously an approach available for obtaining the spatial distribution of
137
Cs reference inventory with high resolution and accuracy to adopt the GIS interpolation on the basis of the measured data, which is referential for the study of soil erosion using
137
Cs tracing technique.
2018 Vol. 16 (5): 57-66 [
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295
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422
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67
WU Yuheng, WU Wenyong, HAN Yuguo, LIAO Renkuan
Effects of different fertigation strategies on the distribution of cauliflower's roots and soil nitrogen
[Background]
In older to solve the problems of low level of water and fertilizer management of vegetable facilities and imperfect irrigation and fertilization system in China, field experiments were conducted in a solar-heated greenhouse to study the effects of different fertigation strategies on root growth and distribution of nitrate-nitrogen from a surface point source of urea.
[Methods]
Four fertigation strategies with different orders in which water and nutrients was applied for an irrigation event were that T1(1/5N-4/5W), T2(1/5W-1/5N-3/5W), T3(2/5W-1/5N-2/5W), and T4(3/5W-1/5N-1/5W), for example, the 1/5W-1/5N-3/5W represented irrigating water at the first 1/5 of the fertigation time, applying nitrogen at the second 1/5 of the fertigation time, and washing pipeline with water at the last 1/5 of the fertigation time, the interpretation of other treatments were similar. Cauliflower was taken as the research object in the experiment, and each treatment was triplicate. Soil moisture was determined once a week during caulifower growth. Yield was recorded for each harvest, and the quality, root length density of cauliflower and soil inorganic nitrogen was determined at the end of the experiment.
[Results]
1) Fertigation strategies had no significant effects on yield, quality and nitrogen accumulation of cauliflower. The treatments of applying the nitrogen in the later stage (T3 and T4) had higher yield by comparing the treatments of applying the nitrogen at the beginning stage (T1 and T2). The total nitrogen accumulation of cauliflower showed a trend of decreasing first and then increasing by delaying the nitrogen application to later stage, the nitrogen accumulation in T4 reached the highest of 50.23 mg/kg. 2) By comparing each treatment in the distribution of inorganic nitrogen during per-planting and post-harvest, we found that the content of inorganic nitrogen in soil before planting was high in surface and low in deep layer and the distribution of inorganic nitrogen in post-harvest soil profile was more uniform. Comparing other treatment, nitrate leaching was more likely to occur in T1 and T4. 3) The measurements of root distribution showed that fertigation at the beginning of the irrigation cycle promoted longitudinal growth of cauliflower's roots, and fertigation at the end of the irrigation cycle promoted lateral growth of roots. Contrast with other treatments, T3 had the largest root length density (2.54 cm/cm
3
) and the widest root distribution. 4) A significant linear relationship between the content of soil nitrate-nitrogen and the root length was found, and the root with diameter <2 mm had better fitting effect than other indexes of root length (
R
2
=0.811 8).
[Conclusions]
Considering yield, quality, nitrogen use efficiency, root length density and the nitrogen content in soil, the strategy of T3, i.e., applying water at first for 2/5 of the total irrigation time, then applying fertilizer for 1/5 of the total irrigation time, followed by applying water for the last 2/5 of the total irrigation time, was suggested.
2018 Vol. 16 (5): 67-76 [
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77
LÜ Gang, XIAO Peng, LI Yexin, DONG Liang, DU Xinpeng
Stability of topsoil aggregates under different reclamation modes in the dump of Haizhou opencast coal mine
[Background]
The stability of soil aggregates plays an important role in maintaining land productivity and regulating soil fertility. It is also one of the important indicators to reflect the soil structure. In order to explore the influences of different reclamation modes on the stability of soil aggregates, 5 reclamation modes of shrub (
Amorpha fruticosa
)forest,
Ulmus pumila
forest,
Robinia pseudoacacia
forest,mixed forests(
Robinia pseudoacacia
and
U. pumila
)and weeds in Haizhou opencast coal mine, Fuxin city of Liaoning province, were used as the research objects.
[Methods]
The dry sieving method and wet sieving method were used to measure soil mechanical aggregates, and the stability of soil aggregate index (
R
>0.25
) and percentage of aggregate destruction (PAD), soil aggregate diameter index (mean mass diameter MWD, the geometric mean diameter GMD and the fractal dimension of soil the number of
D
) as the evaluation index, to analyze the characteristics of soil aggregate stability under different reclamation modes.
[Results]
1) Big aggregate content(
R
>0.25
)was used to reflect the soil structure of quality, big aggregate content(
R
>0.25
) was 58%-63% in the dry sieve of different reclamation mode, and was 17.5%-37.43% in the wet sieve. Important indicators were the diameter of the soil aggregate mean mass diameter (MWD) and geometric mean diameter (GMD). 2) In the condition of dry sieving, there were MWD (2.27) and GMD (1.3) in mixed forest, MWD (1.56) and GMD (0.96) at least grassland. Under the condition of wet screening, MWD (2.97) and GMD (2.43) of
Robinia pseudoacacia
forest were the most, and MWD (1.16) and GMD (0.53) were the least in the grassland. 3) In fractal dimension, the fractal dimension of the dry sieves and wet sieves was 2.23-2.35 and 2.35-2.43, respectively. The correlation coefficients were 0.949, 0.610 and 0.514 under dry screen condition, respectively, and their correlation coefficients were 0.999, 0.276 and 0.282 under wet screen conditions, respectively. The he overall trend on the surface layer of soil in different reclamation modes for aggregate stability, soil aggregate diameter and aggregate destruction rate was better than that of weeds, the soil aggregate destruction rate was the lowest in shrub land, soil aggregate diameter index was better in the
Robinia pseudoacacia
and mixed forest, and soil stability index MWD and GMD were better in forest land.
[Conclusions]
The stability of soil aggregates were of positive correlation between the fractal dimension, and was positively correlated with the
D
value. In the process of transforming from micro aggregates (<0.25 mm) to 5 mm, the 1.00 mm and 2.00 mm aggregates were the more critical nodes. The comprehensive experimental results show that the soil structure in the dump was seriously damaged, the climatic environment of the soil where vegetation grew was poor, and the vegetation restoration was a slow process in improving the soil.
2018 Vol. 16 (5): 77-84 [
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517
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440
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85
ZHANG Hongda, WANG Baoyi, NIU Yong, SONG Yuanyuan, LIU Xia, LI Jiazuo, ZHANG Chunqiang, YUAN Li, LÜ Mingdao
Application of Ovitalmap in field survey of regional water and soil loss monitoring
[Background]
For soil and water loss monitoring, the commonly used methods are sampling survey, comprehensive evaluation, and empirical models (USLE, WEQ, and CSLE). It is known that the field investigation is the key point for the monitoring of soil and water loss when we use the methods described above. However, the tradition field investigation technic cannot meet the requirements of present regional monitoring of soil and water loss. Therefore, this research mainly focuses on exploring an efficient, accurate and high quality data collection technic in Mengyin of the Yimeng-Taishan Mountain National Key Control Area.
[Methods]
Based on the field investigation unit (Grid or watershed), the pros and cons of Ovitalmap technic with traditional field work methods were compared. Many new technics and methods have been developed through combing the Ovitalmap with Geographic Information System (GIS) in soil and water loss investigation as such:Basic data processing and importing, route navigation, position locating, data collection, location sharing, and data analysis.
[Results]
The applications of Ovitalmap technic indicated that the efficiency and accuracy of route navigation and site positioning was improved dramatically. During the field data collection, Ovitalmap provided a digitalized platform for map drawing in the field without paper, which reduced the cost of indoor data analysis and increased the working efficiency. Meanwhile, the Ovitalmap was able to provide the real-time information of landform, vegetation coverage, and soil and water conservation measures, the comparisons of the information between measured value and extracted value in specific field sites, and reasonable evaluations of the comparison. Based on the overlay of vector data and raster data, the real-time positioning, and display function of Ovitalmap, it captured information with higher accuracy and efficiency. The camera function realized the exact correspondence between the location, time, shooting direction, and photos of the shooting point. The indoor organization process was effectively simplified and better convergence with collected information was achieved.
[Conclusions]
This research found out and solved the problems in the application of Ovitalmap for the investigation of soil and water loss. Moreover, based on the practical usage experience of Ovitalmap, this paper also proposes some reasonable recommendations for the weaknesses of Ovitalmap. The results of this research can provide technical supports for regional soil and water loss monitoring, comprehensive management of soil and water loss, soil and water conservation of construction projects, and the field investigation of soil and water loss.
2018 Vol. 16 (5): 85-94 [
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522
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682
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95
JIN Yaqin, LI Donglin, SUN Lijuan, ZHANG Wenbao, YE Ziqing
Water-holding characteristics and accumulation of litter in different man-made forests in the suburb of Nanjing
[Background]
Many researchers have studied natural forest litter and obtained a lot of achievements. The litter plays a major role in forest soil and water conservation, this is beyond doubt. However, it is lack of study on the litter characteristics of man-made forests, especially in the suburbs of cities.
[Methods]
Water-holding characteristics and accumulated amount of litter in 8 species city man-made forests was studied in the suburb of Nanjing. Litter thickness (
d
) and accumulation (
M
) of litter were measured by sampling, natural water content (
R
0
),water holding rate (
R
t
), maximum water holding rate (
R
max
) and water absorption rate(
V
) were analyzed in laboratory, maximum retain rate(
R
拦
), maximum retain capacity (
W
拦
) were calculated and effective retain deepness was calculated.
[Results]
1) The effect of forest composition on litter characteristics was significant, litter thickness and accumulated amount showed significant difference in different communities (
P
<0.05). 2) The change of litter thickness ranged from 2.10 to 5.24 cm, the descending order of litter thickness was as
Cinnamomum camphora
forest(Ⅰ),
Michelia chapensis
forest(Ⅱ),
Ligustrum lucidum
forest(Ⅲ),
Liriodendron chinense
forest(Ⅳ),
Phyllostachys glauca
forest(Ⅷ),
Celtis sinensis
forest(Ⅴ),
Zelkova serrata
forest(Ⅶ),
Acer palmatum
forest(Ⅵ), and the change of accumulated amount was the similar. The correlation analysis showed it was positive between litter accumulation (
M
) and its thickness (
N
), the linear equation was
M
=1.405 4
d
+0.665 4 (
R
2
=0.823 4,
P
<0.05). The change of water-holding capacity of litter in different forests was consistent, i.e., the water-holding capacity(
W
) increased sequentially with the increase of immersion time (
t
), and showing as an inverted "J" curve with the equation
W
=
a
ln
t
+
b
. The water absorption rate of all litter showed another change, that was, the water absorption rate decreased successively with the increase of immersion time, showing as a "L" curve and the equation was fitted as
v
=
at
b
. 3) The
R
max
of the 8 plantations were 667.56%(Ⅶ), 462.90%(Ⅵ), 341.18%(Ⅴ), 292.19%(Ⅱ), 298.01%(Ⅲ), 290.76%(Ⅷ), 191.38%(Ⅳ), and 271.99%(Ⅰ). 4) The water-holding capacity of litter varied among different forests types,
Z. serrata
forest(Ⅶ) was the strongest by by comparing the
W
sv
, which was 26.32 t/hm
2
,
A. palmatum
forest(Ⅵ), and
L. lucidum
forest(Ⅲ)were more strong, that of which were 16.64 t/hm
2
,16.44 t/hm
2
. The
W
sv
of the
L. chinense
forest(Ⅳ) was only 9.55 t/hm
2
, which was the weakest on the effective retain deepness.
[Conclusions]
The water-holding capacity of different plantation communities was significantly different, and the selection of tree species and community types in urban plantation construction had an important effect on the water-holding capacity and water conservation ability of forest land. Cultivating
Z. elkova
forest is more reasonable development direction of urban forest construction in Nanjing at present because of its strong ability of the effective retain deepness to water and soil.
2018 Vol. 16 (5): 95-104 [
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105
HUANG Ripeng, LI Jialin, DUAN Yibin, FENG Baixiang, HE Gaili
Effects of rapid urbanization on land use and ecosystem service value in Cixi county, the south shore of Hangzhou Bay
[Background]
Rapid urbanization has resulted in the reduction of other types of land due to the large number of urban construction sites, and has an impact on the value of regional ecosystem services. Relevant research may provide information for regional sustainable development and policy decision-making.
[Methods]
Taking Cixi county on the south shore of Hangzhou Bay in China as the study area, this work utilized 3 periods' (in the year of 2005, 2010,and 2015) remote sensing data and extracted the information of land use in the 3 periods to analyze the change of land use as well as the change of ecosystem services value (ESV) due to the rapid urbanization in Cixi county. ESV was calculated by the modified model from R. Costanza.
[Results]
1) From 2005 to 2015, land use changes in Cixi county showed a large decrease in tidal flats, and its area decreased by nearly 40.4%. Most of the tidal flats were transformed into dry lands, and a few were converted into paddy fields. The increase in construction land was the most significant, with an average annual increase of 11.3 km
2
. The expansion of construction land increased the fragmentation of other land types. 2) Among the various types of land use in Cixi county, the ESV of tidal flat was much higher than that of other land types. In 2005, the ESV of tidal flats accounted for 60.2% of the entire Cixi area. In the past 10 years, the ESV in Cixi County has continued to decline, reaching 10.02×10
8
Yuan. The main reason for this was the sharp drop in tidal flats. 3) Over the past 10 years, the ESV lost due to the expansion of construction land up to 7.30×10
8
Yuan, accounting for 73% of the total ESV reduction, and the ESV loss from various land use types during 2005 to 2010 was higher than that of 2010-2015. Regarding the structure of ESV loss, the amount of lost ESV due to the conversion of tidal flats into construction land amounted to 4.60×10
8
Yuan, accounting for 62.9%, followed by occupied water area, the loss ESV accounted for 23.6%, and the remaining land types had a relatively small impact on ESV.
[Conclusions]
Overall, there is a negative correlation between the urbanization level and the ESV in Cixi County. The expansion of construction land and the reduction of tidal flats affected by urbanization is the main reason for the ESV loss.
2018 Vol. 16 (5): 105-113 [
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442
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114
SHI Yanjin, ZHOU Yunchao
Soil erosion characteristics of clear cutting plots in Karst rocky desertification area
[Background]
As a result of low content of acid insoluble material in bedrock and the slow weathering rate of rock in Karst area, the rate of soil formation is very little, and extremely serious environmental and social problems will occur while soil is eroded. Moreover, it is difficult to monitor soil erosion accurately because of the complex structures above ground and underground at Karst area. Here we are trying to find appropriate method to monitor the amount, variation pattern, and formation mechanism of soil erosion during the natural restoration of a typical clear cutting in Karst area in Puding county of Guizhou province.
[Methods]
Drilling method is appropriate to trace soil erosion
in situ
according to previous studies, it was combined with runoff plot method to be used in this study. Test bras had been set by uniform distribution of a interval of 1 meter and the distance from top of bras to soil surface was measured each time to obtain the erosion depth between ever two measurement. on the other hand, runoff plot was built around the clear cutting plot and sediment was collected and weighed after every heavy rainfall. The result of these two methods was compared.
[Results]
1) During the 4.5 years of restoration after clear cutting, the result by drilling method showed an overall trend of erosion, with a cumulative erosion depth of 1.46 cm (Equivalent erosion modulus 2 066.7 t/(km
2
·a)), which had a large fluctuation at the first one year of the natural recovery, then the fluctuation, decreased (except the test of April 2015(about 3 years of the natural recovery)), and tended to be stable after 3.5 years. 2) The erosion modulus obtained by the runoff plot method was 0.78 t/(km
2
·a), and the sediment can only be collected after one rainfall of 67.6 mm,which rainfall intensity reached 42.4 mm/h within two months after clear cutting. 3) There was a huge difference between the erosion modulus obtained from the drilling method and runoff plot method (about 2 065.92 t/(km
2
·a)). This might be resulted from the special surface rock and soil distribution pattern of Karst area and the different observation emphases and properties between the two monitoring methods. The results by the two methods could not be compared generally. The drilling method was more representative at this situation on account of it could monitor the special move form of Karst (soil creeping and underground soil loss) by situ monitor. 4) During the early natural restoration stage, rainfall played the most important role in influencing the soil erosion due to soil exposure, but coaction of litter, soil organic matter and other factors might reduce soil erosion after the restoration of vegetation.
[Conclusions]
The amount and variation of soil erosion at the clear cutting plot are understood at certain level in this research, but the feasible major influencing factors, which have a very important effects on soil and water conservation, are only speculated. Further research is needed.
2018 Vol. 16 (5): 114-119 [
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473
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120
WANG Yangui, CHEN Kang, CHEN Yin, LIU Xi
Variations in runoff and erosion and their distributions in the Yellow River basin
[Background]
With climate changes and the frequent occurrences of human activities such as reservoir construction, soil and water conservation, and water diversion project, water and sediment characteristics in the Yellow River basin would be changing.
[Methods]
In order to understand the processes of the runoff and sediment yields in the Yellow River basin, according to the water and sediment field data of the main hydrological stations in the mainstreams and the main tributaries in 1950-2015, the variation process and spatial distribution characteristics of runoff and erosion in the basin were studied with the Mann-Kendall statistical test method (called M-K Method) and the hydrological accumulation curve method by introducing the parameters of regional runoff depth and regional sediment transport modulus.
[Results]
1) For the runoff depth in the basin, there are no variation trend in the Tangnaihai station of the mainstream with an average value of 164.4 mm, and decrease trends in the Lanzhou station of the mainstream and in the tributaries of the Yan River and the Beiluo River and obvious decrease trends for the other hydrologic stations in the basin in an exponential form, which shows the runoff generation capacity in other areas of the Yellow River basin gradually or obviously attenuates except for the area above the Tangnaihai station. 2) For the sediment transport modulus in the basin, except for no change trend in the Tangnaihai station with an average value of 97 t/(km
2
·a), there are obvious decrease trends for the other hydrological stations in the stem mainstream and 11 tributaries in the exponential decay law, which shows that sediment yield capacities in the basin are greatly weakened and soil erosion is reduced except for the area above the Tangnaihai station. 3) In the Yellow River basin, the upper reaches is the main area of runoff yield with the great regional runoff depth value of 138.9 mm and the small regional sediment transport modulus value of 260.6 t/(km
2
·a) in the area above the Lanzhou station, the middle reaches is the main area of sediment yield with the small regional runoff depth value of 39.1 mm and the great regional sediment transport modulus value of 2 776.9 t/(km
2
·a) in the Longmen-Tongguan area, and the lower reach area is the main consumption area of runoff and sediment with the negative regional runoff depth value of -340.8 mm and the negative regional sediment transport modulus value of -7 060.6 t/(km
2
·a). It still exists, but weakened for the runoff and sediment from different sources.
[Conclusions]
Therefore, there are obvious variations in runoff and sediment yield characteristics because of influence of the human activities in the Yellow River basin, and it is weakened for that the runoff and sediment are from different sources, which needs to be paid attention.
2018 Vol. 16 (5): 120-128 [
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417
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129
QI Fei, HU Xuli, LIU Xia, XING Xianshuang, SONG Yuanyuan, ZHANG Hongda, XU Chun, ZHANG Zhiyang, LI Zhengbo
Soil and water conservation planning layout and measures configuration for Yiyuan county based on small watersheds
[Background]
Small watershed is the basic unit in the comprehensive control of soil erosion and water loss. It is of great significance to carry out the division of small watersheds and determine the control direction for soil and water conservation layout at county scale. Yiyuan county, located in the national key management area, one of the key counties for the comprehensive control of soil and water conservation at the state and provincial level, was taken as the research object in the paper.
[Methods]
The basic data were remote sensing ZY-3 with resolution 2.1 m and 1:50 000 maps of topography, soil, administrative division and forest resources. The characteristics of soil erosion in the Yiyuan county were obtained by CSLE model, and its main influencing factors vegetation coverage was calculated by NDVI (normalized difference vegetation index) and field survey. The elevation, topographic fluctuation and slope were extracted and the landform types were classified based on the DEM. The land use was determined by human-computer interaction interpretation and field verification. The division of a small watershed was determined based on the ArcSWAT and 25 m DEM combined with rivers and administration division. The layout of soil conservation and the key area of prevention and control were determined by:1) firstly investigating the needs of soil and water conservation via field investigation, and 2) then by spatial overlay and statistical analysis based on the basic information such as land use, slope, forest and grass vegetation coverage, soil erosion and geomorphology according to the combined method of "top-down" and "bottom-up" and the demand of soil and water conservation while taking a small watershed as an unit.
[Results]
1) The total area of soil erosion in the county was 765.99 km
2
, accounting for 46.83%, mainly mild erosion, distributed in the southeast, southwest and northeast of the county. 2) There were 68 small watersheds in the county. The average area of a small watershed was 24.06 km
2
, and channel density was from 1.87 to 2.99 km/km
2
. Soil erosion area percentage of 45% small watersheds was more than 50%. 3) Four soil and water conservation districts and "3 Belts and 3 Areas" key layouts were taken out according to the needs of soil and water conservation and characteristics of small watersheds. 4) The 21 small watersheds would be developed into ecologic and clean-type small watersheds, with enclosure mainly (55%). The 47 small watersheds would be developed into ecological economy watershed, of which mainly with enclosure (45%) in the northeast, with economic fruit forest (60%) in the southeast, and with enclosure (35%) and bench terrace (30%) in the southwest.
[Conclusions]
Soil and water conservation layout and measures configuration at county level, based on the small watersheds and polygon, may provide technical and scientific support for county soil erosion control and soil and water conservation management.
2018 Vol. 16 (5): 129-135,144 [
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136
ZHANG Xuemei, CHEN Tao, FU Honglun, WANG Xuchun, KUANG Peipei, LIU Min
Experimental preparation of light particles for flower growth using living sludge
[Background]
The domestic sludge contains a large number of nutrients such as nitrogen, phosphorus and potassium, but accumulates a large number of pathogens and organic pollutants such as parasites (eggs).The light particles can be prepared for flower growth by using sludge and adding inorganic powders including clay, quartz sand tailings, diatomaceous earth, and so on. This effectively reuses domestic sludge and avoids environmental pollution from domestic sludge.
[Methods]
Each raw material was ground using an agate mortar before test to maintain the particle size of the raw material between 200 and 600 mesh. The particle size distribution of each raw material was measured using a Bettersize2000 laser particle size distribution analyzer. The compressive strength of lightweight particles was measured using an ATH-5000 spring tension tester. The microscopic morphology of light particles was analyzed using an EVO-18 scanning electron microscope. The product crystal analysis was carried out by XD-3 X-ray powder diffractometer.
[Results]
The compressive strength of the light particles decreased from 7.47 to 2.33 MPa, the bulk density decreased from 1.63 to 1.11 g/cm
3
, and the water absorption rate increased from 33.33 to 63.67%, when the sludge content increased gradually from 0 to 100%. The compressive strength of the light particles increased to 7.35 MPa then began to decline, the bulk density of the light particles increased from 0.91 to 1.20 g/cm
3
, thus, the water absorption rate gradually decreased from 61.33% to 40.33%, when the contents of clay increased from 0 to 100%. Quartz sand tailings were to increase the content of the SiO
2
of the product, and improved compressive strength of the products. The products possessed strong adsorption with water absorption rate of 50%, by the porous structure of diatomaceous earth and the amount of organic matter evaporated in the sludge. The optimal addition amount of each inorganic powder reagent was determined using single-variable control method as domestic sludge 50%, clay 30%, quartz sand tailings 10%, kaolin 5%, diatomaceous earth 2%, Al
2
(SO
4
)
3
3%, firing temperature 930℃, and holding time 50 min, the compressive strength of the light particles prepared under the optimal conditions was 4.0 MPa, the water absorption rate was 50%, and the nutrient mass fraction N 37.1 mg/g, P 12.5 mg/g, K 4.4 mg/g.
[Conclusions]
The utilization rate of the domestic sludge is up to 50%, the compressive strength of the light particles is above 7.0 MPa, and the water absorption rate is 50%. The performance of the product particles is superior to the domestic and foreign equivalent products, and meets the vegetation growth requirements of flowers and the like, accorded with national standards GB/T 17431-1998. The conditions provide a simple and easy way to utilize sludge efficiently, and showing certain economic, environmental and social benefits.
2018 Vol. 16 (5): 136-144 [
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340
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145
QIN Qingfeng, CHEN Chen, ZENG Xianzhi, HE Jiafei
Review and prospect of protection forest system construction in the Yangtze River Basin in the past 30 years
[Background]
The Yangtze River Basin shelterbelt system construction project is the first national key ecological treatment project in China. In order to improve the deteriorating ecological environment of the Yangtze River Basin, China has put forward the overall goal of building shelter forests in the Yangtze River Basin. It is planned to use 30-40 years to plant trees in the Yangtze River Basin, increase the area of forests, improve the situation of soil erosion, and ensure social and economic development.
[Methods]
Through the implementation of the Yangtze River Basin shelterbelt system construction project, we will continue to push forward the watershed ecological management work.
[Results]
Promoting ecological management in the Yangtze River Basin with the model of ecological engineering has achieved remarkable results, and has achieved obvious ecological, economic and social benefits.
[Conclusions]
Through reviewing the 30-year history of the construction of the protective forest system project in the Yangtze River Basin, this paper clarifies the development context of the Yangtze River Basin engineering control in China, summarizes the technical system and comprehensive control model of soil and water loss by biological measures such as afforestation, and extends the successful experience and typical achievements to other areas. We are looking forward to the future development trend of the Yangtze River Basin shelter forest construction in China.
2018 Vol. 16 (5): 145-152 [
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