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2018 Vol.16 No.6
Published 2018-12-30
1
CHEN Meijun, MU Xingmin, GAO Peng, ZHAO Guangju, SUN Wenyi, ZHAO Jianmin
Characteristics and driving factors of runoff changes in the upper reach of the Beiluo River basin
[Background]
Studying the impact of human activities and precipitation changes on runoff and analyzing the main driving factors of the runoff changes in the upper reach of the Beiluo River basin could provide decision-making basis for water and soil conservation and rational use of water resources in the upper reaches of the Beiluo River basin and similar watersheds.
[Methods]
Based on the daily precipitation data and runoff data of Wuqi meteorological station in the upper reach of the Beiluo River basin from 1971 to 2014, the study uses the cumulative anomaly method, Mann-Kendall trend test, and precipitation-runoff double mass curve method to analyze the changes in trends and diagnosis the variation point of the annual precipitation and runoff changes in the upper reaches of the Beiluo River during 1971-2014. The double mass curve method and linear regression model are used to quantify the impact of climate change and human activities on precipitation and runoff changes in the annual scale and flood season.
[Results]
The results show that after the implementation of the Grain for Green Program in 2003, the precipitation-runoff relationship in the upper reach of the Beiluo River changed abruptly. The annual runoff and the flood season runoff after the mutation were significantly lower than those before the mutation, and the annual runoff changes were mainly caused by the reduction of the flood season runoff. Before 2003, the average daily runoff>100 m
3
/s,>1.15 m
3
/s, and <0.5 m
3
/s were 0.27%, 59.2%, and 8%, respectively, decreased to 0.07%, 44.9%, and 0.048 after 2003. The contribution of human activities to the annual runoff and the reduction of runoff during the flood season was 106% and 114% respectively. The capacity of vegetation to regulate runoff is significantly increases a few years after the implementation of the Grain for Green Program due to the increase in the area of forest land and the reduction of farmland area. The number of the days that have extreme runoff has decreased obviously after 2003. The proportion of the non-flood season runoff accounts for annual runoff has decreased in recent years. At the same time, the ratio of moderate flow after the mutation increased compared to the previous years. Changes in runoff are less sensitive to changes in precipitation.
[Conclusions]
Large-scale of the vegetation restoration is a direct factor for the decrease of runoff in the Beiluo River's source area, and the policy of Grain for Green Program and soil and water conservation is the core driving force. At the same time, with the extension of the time for Grain for Green Program, the runoff in the upper reach of Beiluo River will not continue to decrease, and will remain at a relatively low and stable level in the future.
2018 Vol. 16 (6): 1-8 [
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9
YU Xianju, LIU Chenguang, FU Suhua, MU Hongli, WU Sinan, LIU Yingna, ZHANG Guanghui
Comparison on flow transport capacity of overland flow between cohesive and non-cohesive sand
[Background]
Flow transport capacity refers to the maximum flux of sediment that can be transported under specific hydrodynamic conditions, and is an important parameter of soil erosion process model. Domestic and foreign scholars have carried out research works on the flow transport capacity of overland flow; however, the experimental materials are relatively simple, and the soil is not fully considered in the object of the overland flow and the experimental object is concentrated in the non-cohesive sand. Therefore, it is necessary to compare the flow transport capacity of overland flow between cohesive and non-cohesive sand.
[Methods]
The cohesive sand (sampled from black soil of Nenjiang county in Heilongjiang province and the median particle size of 0.28 mm) was used as experimental material. The experiment was designed with 5 slope degrees (3°,6°,9°,12°,and 15°) and 6 flow rates(0.25, 0.50, 0.75, 1.00, 1.50, and 2.00×10
-3
m
3
/s), totally 30 experiments. The experiments were carried out in a flume with 5.0 m long and 0.4 m wide. Dyeing method was to measure the flow rate. The hydraulic parameters and the flow transport capacity of cohesive sand were processed using SPSS software and Origin software, and graphed to obtain the relationship between the flow transport capacity of the cohesive sand and the different hydraulic parameters. The measured results were compared with the ones calculated by equations previously from non-cohesive sand in our laboratory.
[Results]
1) Flow transport capacity of both the cohesive sand and the non-cohesive sand increased with the increase of the flow velocity, shear stress and stream power. 2) Under the same hydrodynamic conditions, the flow transport capacity of the cohesive sand was greater than that of non-cohesive sand. 3) The relationship between the flow transport capacity of the cohesive sand and the flow velocity, shear stress and stream power was expressed as a power function, and the coefficients of determination were 0.91, 0.72 and 0.80, respectively. The flow velocity was the best hydraulic parameter for calculating the flow transport capacity of cohesive sand. The shear stress and stream power provided the higher accuracy for calculating the flow transport capacity of the non-cohesive sand. The coefficients of determination were 0.98 and 0.98. 4) The measured critical flow velocity of cohesive sand was 0.245 m/s, <0.309 m/s calculated by the equation from the non-cohesive sand previously. The coefficient of determination and Nash-Sutcliffe efficiency coefficient of cohesive sand were 0.72 and 0.78 respectively, while the shear stress equation of non-cohesive sand was used to calculate the flow transport capacity of the cohesive sand. The coefficient of determination and Nash-Sutcliffe efficiency coefficient of cohesive sand were 0.80 and 0.43 respectively, while the stream power equation of non-cohesive sand was used to calculate the flow transport capacity of the cohesive sand. The coefficient of determination of cohesive sand was 0.20 while the relationship between the flow transport capacity of the cohesive sand and the unit stream power was fitted by a power function.
[Conclusions]
There are differences in flow transport capacity of a slope between cohesive and non-cohesive sand, he flow transport capacity equation obtained from non-cohesive sand is not suitable for cohesive sand.
2018 Vol. 16 (6): 9-14 [
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15
WANG Manyu, CAI Yongmao, LI Chunzheng, ZHANG Zhiqiang
Impact of climate change and human activities on watershed baseflow: A case study of the upstream of Miyun Reservoir in Chaohe watershed
[Background]
It is one of the challenging issues in water resources management as influence of climate changes and human activities have intensified on the hydrological cycling of watershed. As a component of streamflow, baseflow plays a significant role in water balance analysis, optimal allocation and management of water resources, as well as the maintenance of healthy river ecosystems. However, it has rarely been explored on the impacts of climate change and human activities on the baseflow up to date.
[Methods]
We, therefore, used well established baseflow separation method, Chapman-Maxwell filtering, to separate the baseflow from
in situ
measured daily streamflow data for Chaohe watershed located in the upstream of the Miyun Reservoir from 1963 to 2015 in northern China. Mann-Kendall test and double mass curve approaches were then applied to track the change trend and change points of annual baseflow and to quantify the contributing percentage from climate change and human activities for the studied period.
[Results]
1) From 1963 to 2015, the baseflow in the Chaohe watershed significantly declined with the change point occurred in 1999, baseflow decreased by average annual of 0.1 mm. Before and after the change point, the annual average precipitation decreased by 16.4% (84.4 mm), the annual average PET increased by 7.3% (84.4 mm), and the annual average base flow decreased by 66.8% (9.2 mm). 2) Climatically, the baseflow was significantly correlated with precipitation in a positive way (
R
2
=0.64,
P
<0.01) while negatively correlated with Penman-Monteith equation derived potential evapotranspiration (PET) significantly (
R
2
=0.27,
P
<0.01), precipitation played a more important role than PET in baseflow variation. 3) Decreasing baseflow was mainly caused by human activities with maximum contribution rate of 81.10%.
[Conclusions]
The human activities were the main reason for the decreased baseflow from 1999-2015 in Chaohe watershed. Such activities include land use/land cover changes, massive ecological restoration, water conservancy project construction, and water withdrawal and water uses in the watershed. More specifically, the implantation of soil and water conservation measures and land conversion programs(Grain for Green) in the Chaohe watershed made significant increase in forestland and decrease in grassland and cropland, which favored more evapotranspiration and leading to the reduction of baseflow.
2018 Vol. 16 (6): 15-23 [
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24
OU Yang, YAN Baixing, BAI Jianhong, CHEN Haosheng, GAO Yuan, LI Rongxuan, GAO Yan, ZHANG Yanling, CUI Hu
Identifying the damaged area of gully in black soil region of Northeast China
[Background]
The black soil area of the Northeast China is an important grain production area and the largest commercial grain production base in China, but the soil texture is loose and the corrosion resistance is poor. Under the driving force of hydraulic erosion, the sheet erosion of a slope-land would develop to a gully on the depression area in the watershed. The First National Water Conservancy Survey (2010) showed that there were more than 295 700 gullies of over 100 meters in the black soil area of northeast China, covering an area of 3 648 km
2
. At present, the gully erosion has been seriously deteriorated, and large-scale control is urgently needed in the black soil region of Northeast China. However, research on the area protected by gully erosion control is extremely scarce, and it had brought great difficulty to government departments in decision-making, gully erosion prevention planning, and evaluation of gully erosion mitigation effectiveness.
[Methods]
Therefore, based on the characteristics of occurrence and development of gullies, this paper defined the potential catchment area as an important part of its damaged area of gully erosion, thus that damaged scope of a gully not only included the current spatial impact of gully erosion, but also reflected the future development of gully damaged area at temporal scale. On the basis of gullies data in the black soil area of Northeast China from the First National Water Conservancy Survey and digital elevation model (DEM) with 30 m precision, GIS spatial analysis technology was comprehensively used to determine the current and the potential catchment boundary of some gullies in the black soil region.
[Results]
Based on the 10 m precision DEM, the average error of 460 gullies catchment area was about ±16.04%. The identification error of catchment area for large gullies was small. The difference among the damaged areas of different types of gullies was significant. The damaged area of large-size gullies was significantly larger than that of small-and medium-size gullies, but the latter accounted for a very high proportion of potential damaged area. Small-and medium-size gullies should be considered as prior control in the black soil area in future, so as to effectively increase the cost-effectiveness of investment in protection projects. The length of the gullies was more related to its damaged area than their covering area.
[Conclusions]
Catchment area is defined as the damaged area of a gully, reflecting the influence of the gullies on different spatial scale areas (direct impact area, indirect influence area, and catchment area), and charactering the development of gullies on the long-term scale (the current catchment area and the potential catchment area). The method of identifying gully damaged area had moderate data accuracy requirements. The 30m DEM data was coupled with vector gullies data from the First-ever Nationwide Water Resources Survey, and the needs of identifying the catchment boundaries of erosive gullies are met.
2018 Vol. 16 (6): 24-30 [
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31
WANG Ying, ZHENG Zicheng, LI Tingxuan, HE Shuqin
Change of soil surface roughness during maize growing season and its relationship with soil erosion amount on slope of contour tillage during water erosion process
[Background]
The purple soil region is one of the typical areas suffering serious soil erosion in Southwest China. Serious soil erosion would surely result in the loss of sediment and the occurrence of runoff. The objectives of this study is to investigate the relationship between soil surface roughness and soil erosion amount of contour tillage during maize growing stages, providing a scientific basis for revealing the mechanism of soil surface roughness in sloping farmland of purple soil.
[Methods]
The artificial field rainfall experiment was carried out for determination of characteristics of soil surface roughness and soil erosion amount during maize growing stages. And the relationship between soil surface roughness and soil erosion amount was analyzed. A total of 36 rainfall simulation experiments were conducted in two 1 m×2 m boxes under 3 rainfall intensities (1.0, 1.5 and 2.0 mm/min) on a typical gradient of 15°.
[Results]
1) The largest change range of soil surface roughness was in rill erosion stage, the change range of soil surface roughness reached minimum value at tasseling stage and the soil surface roughness reduced maximally at seedling stage during water erosion process (58.87%). 2) The soil erosion amount in rill erosion was significantly higher than that in splash erosion and sheet erosion. With rainfall intensity increased, the soil erosion amount at seedling stage increased during splash erosion, while that at seedling stage was opposite to the changes at other growing stages. The soil erosion amount during maize growing season reached maximum at 2.0 mm/min rainfall intensity in sheet erosion and rill erosion (218.82 g and 349.41 g). The soil erosion amount at seedling stage was 1.60, 3.18 and 1.79 times greater than that at jointing stage, tasseling stage and maturing stage, and significantly higher than other growing stages. 3) The regression equations of initial soil surface roughness, change range of soil surface roughness, rainfall intensity and soil erosion amount significantly correlated in sheet erosion and rill erosion. A significant correlation was observed between change range of soil surface roughness, rainfall intensity and soil erosion amount during splash erosion stage.
[Conclusions]
The changes of surface roughness and soil erosion amount reached maximum at seedling stage. The change of soil surface roughness could better be predicted soil erosion amount during water erosion process.
2018 Vol. 16 (6): 31-37 [
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38
XU Wenlong, ZHAO Guangju, MU Xingmin, GAO Peng, SUN Wenyi
Variations and correlations of runoffs and sediment loads in the main stream of the upper reaches of the Yellow River over the past 60 years
[Background]
Climate change and intensive human activities have greatly altered the terrain landscapes, and further resulted in significant changes in hydrological processes throughout the world. In recent years, changes of the ecological environment in the upper reaches of the Yellow River have affected the life of downstream public due to natural and human factors. The objective of this study is to quantify the spatial and temporal variation of runoff and sediment load in the upper reaches of the Yellow River and their potential causes. Better understanding of the variations of runoff and sediment load is greatly helpful for soil and water conservation, water resources planning and Yellow River basin management.
[Methods]
This study systematically analyzed the variations of runoff and sediment load in the upper reaches of the Yellow River from 1950 to 2012 based on the observed data from 10 hydrological stations with some hydrological statistical methods. The non-parametric Mann-Kendall test and Spearman's rank correlation test were utilized to characterize the trends of hydrologic variables in the upper reaches of the Yellow River. The accumulative annual anomaly and wavelet transform method were applied to evaluate the abrupt changes and periodic characteristics of runoff and sediment load over the study period.
[Results]
1) Both multi-year average runoff and sediment load showed decreasing trends over the past 6 decades at 10 hydrological stations from Tangnaihai to Toudaoguai in the upper reaches of the Yellow River, and reducing trend in the most of stations was significant (
P
<0.01), while the changes at the Tangnaihai hydrological station did not display a significant trend. 2) The multi-year average runoff and sediment load were positively correlated, although both exhibited reduction trends. 3) The abrupt change points of annual runoff and sediment load occurred in 1968, 1985, 1986 and 1989, which were strongly related to the operation of large reservoirs Longyangxia and Liujiaxia. 4) The wavelet transform of monthly runoff and sediment load at 10 hydrological stations showed 0.5-1, 3-5, and 7-9 years periodical fluctuation. The significant wavelet spectrum of runoff and sediment load was mainly detected before 1970s or 1990s with a period of 0.5-1 years at confidence level of 95%, but later the periodicity features became more and more insignificant and even disappeared. 5) The average annual runoff showed increasing-decreasing shift from upstream to downstream stations, while the annual sediment load had stepwise increasing trend. The average runoff and sediment load after the 1990s were lower than the multi-year average, indicating that the runoff and sediment load in the upper reaches of the Yellow River decreased significantly in recent years.
[Conclusions]
Both annual runoff and sediment load from Tangnaihai to Toudaoguai hydrological stations showed significantly decreasing trends. The major cause resulting in the reduction of runoff and sediment load in the upper reaches of the Yellow River were large water conservancy project, irrigation, and soil and water conservation measures on some tributaries.
2018 Vol. 16 (6): 38-47 [
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48
YANG Wei, ZHANG Xuexia, ZHAO Jingyao
Remote sensing inversion of leaf area index based on Geosail model and SVR algorithm
[Background]
As an indispensable vegetation parameter in land ecosystem and hydrological models, Leaf area index controls many physiological and ecological processes of plant canopies. Therefore, real-time and accurate acquisition of regional LAI is very important for studying vegetation and soil erosion. Combining the physical model and the statistical model to estimate physiological parameters of the plant is non-destructive, simple, and highly efficient, which is one of the major approaches to quantitative remote sensing.
[Methods]
In the paper, leaf area index of broad-leaved forest was studied in Beijing. Geosail model, a combination of a geometric model and a mixed medium model, was used to simulate the broad band reflectance of canopy. Prospect model, a kind of leaf optical physical model, was used to simulate the leaf hyperspectral reflectance of broad-leaved forest. The leaf hyperspectral reflectance was converted into leaf broad band reflectance by the spectral response function, and then Geosail model used leaf broad band reflectance to simulate reflectance of canopy of broad-leaved forest. LAI and 7 kinds of remote sensing vegetation indexes were generated by simulated canopy reflectance, including RVI, NDVI, GNDVI, RDVI, SAVI, OSAVI, and MSAVI. Then 4 types of statistical regression methods (Linear function, quadratic function, exponential function, logarithmic function) and SVR algorithm were used to establish LAI inversion models. The accuracy of LAI inversion models was verified by Landsat 8 OLI remote sensing data and measured data.
[Results]
The analysis showed:1) SVR algorithm could improve accuracy and prediction accuracy of LAI inversion models than other statistical regression methods. 2) The prediction results of LAI inversion models showed that the performance of OSAVI was better than that of NDVI and other vegetation indices in the field of LAI inversion. This indicated that OSAVI could eliminate the most influence of atmospheric condition and soil background by using the correction factor of canopy background in computing formula, and had better anti-interference ability. 3)The LAI inversion modeling and models prediction showed that the modeling accuracy of NDVI index was very high, but in reality, the prediction accuracy of NDVI index was relatively low. 4) The accuracy and stability of the model constructed by the OSAVI and SVR algorithm were better, and it was the preference model for LAI inversion. Its prediction results were the most accurate, its value of coefficient of determination (
R
2
) was 0.852 8, its value of root mean square error (RMSE) was 0.204 6, and its value of
Slope
was 0.988 1.
[Conclusions]
Therefore, the inversion method based on Geosail model and SVR algorithm was feasible, which could improve the accuracy of LAI inversion and provide new ideas and methods for the application of LAI inversion in large area. Through the LAI inversion model, the ground measured data could be converted to the remote sensing image data scale, which expanded the application potential of Geosail model, SVR algorithm and Landsat 8 OLI remote sensing data in LAI inversion.
2018 Vol. 16 (6): 48-55 [
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56
LI Zixuan, ZOU Haitian, ZHAO Hui, QI Jianhuai
An approach of dividing key control area for soil and water loss at the county scale
[Background]
Forty national key prevention and control regions for soil and water loss were divided in China according to National Plan on Soil and Water Conservation (2015-2030), involving 1091 counties, with a total county area of 49.805×10
8
km
2
,which was approved by the State Council of the People's Republic of China in 2015. The key control area is 4.944×10
8
km
2
, but its specific scope has not been defined up to now. Due to this, key regionalization of prevention and control of soil erosion and water loss are affected on provincial and county levels. Thus studying a dividing method of key control area at the county scale for national key prevention and control region is necessary.
[Methods]
We used ArcGIS to study the dividing method of the key control area in Pingshan county, Hebei province. Before the research, we collected the results of national key regionalization of prevention and control of soil erosion and water loss, township-level divisions of Pingshan county, land use, vegetation coverage and soil erosion. Next, we selected the quantitative and qualitative indexes for analysis. At last, We divided the key control area in Pingshan county by the unit of township district and small watershed partly, and discussed contrastively between the results of study and the reference value of Pingshan county which had been rechecked and provided in National Plan on Soil and Water Conservation (2015-2030).
[Results]
According to quantitative index, the divided key control area based on the unit of township district was 1 358.81 km
2
, and the divided key control area based on the unit of small watershed was 1 273.61 km
2
. The results were all greater than the reference value. And area ratio of sloping land had no reference significance. Instead, the result (1 126.44 km
2
) was close to the reference value (1 106.80 km
2
) and reasonably distributed, the quantitative and qualitative indexes were considered comprehensively and were superimposed over the unit of township district and small watershed.
[Conclusions]
The division of the national key control area of soil and water loss is an important basic work. Firstly, the comprehensive, scientific and operable index system should be constructed. Secondly, the relatively suitable division unit should be selected, which follows the principle demand such as relative centralization. Thirdly, priority should be given to dividing key control area of soil and water loss at the national level, and the division of key control area at the provincial level and below should be carried out under its guidance. Fourthly, the national key control area should be adjusted and managed regularly through dynamic monitoring of soil and water loss.
2018 Vol. 16 (6): 56-63 [
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64
MA Jinping, WANG Weifeng, ZHU Baocai, WANG Shuangxi
The effects of drip irrigation quota on the root distribution characteristics and grain yield of spring corn
[Background]
The Loess Plateau is drought and water shortage. There are many researches on water-saving effect of drip irrigation with mulch, which could accurately irrigate plants. However, the effect of mulched drip irrigation on root and yield of spring corn is very few.
[Methods]
The randomized block experiment was conducted for 2 years in Taigu, Shanxi. The irrigation quota treatments were set up to 0, 8, 12, 16, and 20 mm respectively. The effects of different irrigation quota on the root distribution parameters of the soil depth from 0 to 100 cm and grain yield were studied. The sampling of root distribution included integral excavation and stratified, WinRHIZO analyzed the distribution parameters of root system, and the grain yield was dried by air. Data were processed by Microsoft Excel 2007,SPSS 20.0 software for significance test and Pearson correlation analysis. SigmaPlot 12.5 was plotted.
[Results]
The distribution characteristic parameters of the whole root system increased with the increase of the irrigation quota, and reached the maximum in the irrigation 20 mm. The root length, the root surface area, the root tip number and the root dry weight were very significant, and the root volume and root diameter were significant. The vertical distribution of root length in the 10-20 cm soil layer was the largest, account for 47.29%-60.28% and 48.29%-62.30% in 2016 and 2017, respectively. The root dry weight distribution in the 0-20 cm soil layer was the heaviest, account for 72.03%-85.48% and 71.50%-84.97% in 2016 and 2017, respectively. The grain yield increased with the irrigation quota increasing, but there was no obvious difference in treatment irrigation quota of 16 mm and 20 mm.
[Conclusions]
The plastic mulching drip irrigation measures obviously promote the root growth of the soil surface soil and grain yield. The best irrigation quota of mulched drip irrigation in the central area of Shanxi is recommended to be 16 mm.
2018 Vol. 16 (6): 64-70 [
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WANG Xinyu, LI Suyan, SUN Xiangyang, ZHANG Hua, XIONG Kaiyi, QU Bingpeng, YUN Binghui
Effects of different surface mulches on the physical properties of surface soil
[Background]
With the development of urbanization, human disturbance in the urban soil is more serious than the agricultural soil, thus it is easy to cause a series of adverse consequences such as soil physical property decline, soil erosion and haze weather. In order to improve this phenomenon, using mulch is an ideal way in urban surface soil management.
[Methods]
Five mulches with materials of waterborne polyurethane organic, phenolic resin organic, garden greening waste, bark, and pebble were selected and compared for a one-year barrel-packing experiment. Barrel-packing experiment referred to this:Soil was loaded into the bottom of the plastic barrel and covered with different mulches on the surface, which was repeated for 3 times to investigate the effects of different mulches on soil temperature, moisture, porosity and other physical properties. In this experiment, soil temperature, soil moisture and soil density were measured by curved soil thermometer. The data were processed by SigmaPlot Microsoft Office Excel 2007 and SPSS 21.0.
[Results]
1) According to the influence of temperature of soil caused by different surface mulch in January and July, the soil temperature increased by garden greening waste and bark mulching in the 0-10 cm soil layer in January; the soil temperatures in the 10-20 cm soil layer under different mulching were lower than the control group, but the difference was small. In July, the soil temperature under the pebble mulch was too high, and the water-borne polyurethane organic mulch caused the soil temperature changing slowly. 2) Different mulches all increased soil moisture content. In the 0-10 cm soil layer, the soil moisture content under the waterborne polyurethane organic mulch pad was superior to other mulches, especially in spring, summer and autumn, which was significantly higher than that without mulching treatment. In the 10-20 cm soil layer, except that the soil moisture content under the coverage of garden greening waste was relatively poor in summer, the other treatments had better water retention effect compared with no coverage. 3) Pebble mulch significantly increased soil density in any soil layer, but there was no significant difference in soil density between other mulches except pebbles.
[Conclusions]
The comprehensive indexes showed that the organic mulch of waterborne polyurethane and the bark mulch had a better effect on the physical properties of soil. The bark mulch increased the soil temperature in January and decreased the soil temperature in July; meanwhile waterborne polyurethane organic mulch pad had minimum daily temperature difference in July. At the same time, both of them increased soil moisture content and caused no effect on soil density, thus they can be the first choice for mulching bare soil in the future.
2018 Vol. 16 (6): 71-78 [
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79
QI Shi, LIU Hui, BI Chao, LI Yue, CHEN Fangxiao, LI Shirong, LU Daming
Study on soil and water conservation safety of small watershed in Beijing
[Background]
With the increasing of human activities in recent years, water security, non-point source pollution, the increase of soil erosion area has begun restricting the production activities of Beijing and people's daily life. Soil and water loss has seriously affected the capital's economic and social development and the improvement of people's production and living standards. Therefore, soil and water conservation has played an important role in the prevention and control of soil erosion, and improved the ecological environment of Beijing area. Soil and water conservation is the cornerstone of ensuring the development of the city of Beijing to the international metropolis, taking small watershed as the basic unit, it is necessary to realize the function orientation of different small watershed in the process of specific management, so it is very important to carry out the targeted management.
[Methods]
Total 1 085 small watersheds were taken as the research objects, taking "Three Safeties" (water source safety, flood control safety, and ecological safety) as the goal oriented, using the GIS technology and the method of principal component analysis and cluster analysis, the evaluation indexes of "water source safety", "flood control safety" and "ecological safety" were constructed respectively, the zones of soil and water conservation for "Three Safeties" in Beijing were divided, and the functional orientation of small watershed in different regions was put forward.
[Results]
The main problem of water source safety in Beijing small watershed was the pollution to water source, the area was 16%, and the water source in danger was 1.9%. The main problem in flood control safety zone was that mountain torrents occur easily, accounting for 25%. The main problem in ecological security zone was ecological hazard, accounting for 17.2%. From the comprehensive scoring of the "Three Safeties", the main problem in the plain area was water pollution and ecological risk, the double risks such as mountain water pollution-soil loss risk (2.2%), water pollution-mountain torrents prone (1%), water source danger-mountain torrents prone (0.9%) were the key area that needs to be focused on and governed.
[Conclusions]
Based on the current characteristics of Beijing city, we took the small watershed as the basic unit, with the guidance of "water source safety", "flood control safety" and "ecological safety", respectively, analyzed and evaluated the composition and decisive factors of each requirement, and finally selected and determined the index system according to the importance of various indicators. Taking landform type as the first-level regionalization index and "Three Safeties" as the second-level regionalization index, 2 first-level zones were obtained (plain zone and mountain zone), and 18 second-level zones were obtained.
2018 Vol. 16 (6): 79-88 [
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89
ZHENG Yonglin, WANG Haiyan, XIE Yalin, LI Xiang, QIN Qianqian, YANG Dandan
Effect of tree species on soil fertility quality in plain afforestation area, Beijing
[Background]
Soil fertility affects tree growth and development, whereas tree growth also changes soil fertility. Exploring the relationship between tree species and soil nutrients will contribute to the structural adjustment of plantations and soil fertility restoration, and thus provide guidance on management and regulation of plain afforestation as well as soil ecological restoration.
[Methods]
Five kinds of pure plantations (
Sophora japonica
,
Populus tomentosa
,
Ginkgo biloba
,
Pinus tabuliformis
,
Ulmus pumila
) in the plain afforestation area, Daxing District, Beijing were selected for the determination of soil particle fractal dimension, organic matter, total nitrogen, total phosphorus, total potassium, available phosphorus and pH at depths of 0-20 and 20-40 cm. Principal component analysis was used to evaluate the effect of tree species on soil fertility quality.
[Results]
(1) Soil texture of the study area was sandy loam, with soil particle fractal dimension in the range of 2.439 to 2.609, and there existed no significant differences between tree species. (2) At 0-20 cm, the effects of tree species on soil organic matter, total nitrogen, total phosphorus and available phosphorus were significantly different (
P
< 0.05). At 20-40 cm, tree species had significant effects on soil total nitrogen, total potassium and pH value. With the increase of soil depth, soil organic matter, total nitrogen and phosphorus decreased significantly. In general, total nitrogen and total phosphorus were in a state of deficiency, while available phosphorus mass fraction and pH value were high. (3) At 0-20 cm, soil particle fractal dimension had a very significant positive correlation (
P
<0.01) with soil total nitrogen, and a significant positive correlation with soil organic matter (
P
< 0.05). At 20-40 cm, soil pH was significantly and negatively correlated with total nitrogen, but positively correlated with total potassium and available phosphorus. (4) Principal component analysis showed that soil particle fractal dimension, total nitrogen and total potassium had the greatest influence on soil fertility quality evaluation. The final comprehensive score was in the order of
P. tabuliformis
>
S. japonica
>
G. biloba
>
P. tomentosa
>
Ulmus pumila
.
[Conclusions]
Plain afforestation in Daxing District of Beijing should select tree species according to the purpose of afforestation and give priority to
S. japonica
and
P. tabuliformis
in order to improve soil physico-chemical properties in the short term. To better the effects, traditional fertilizer and organic fertilizer should be applied together so as to provide a good growth environment for the tree species.
2018 Vol. 16 (6): 89-98 [
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99
MA Junming, QI Shi, CHENG Baihan, LIANG Bin, GUO Hubo, CHEN Jianhui
Analysis of rainstorm characteristics in the lower reaches of Honghe River in Yunnan province: Taking Hekou county as an example
[Background]
Yunnan province is a storm-prone region. Due to the climatic and complex geographical environment, characteristics of rainstorm are various a lot in different regions. A study of the characteristics of the rainstorm in small region is helpful for the prevention of rainstorm damages. The lower reach of the Honghe River is located at Honghe region where rainstorms occur frequently. In addition, it is easy to cause flooding, landslides and debris flows and other geological disasters when amount of daily rainfall is over 25 mm. Hekou county is located in the lower reach of the Honghe River and is one of the six major rainstorm centers in Yunnan. This paper takes Hekou county as an example to study the characteristics of rainstorm types in this region.
[Methods]
Based on 177 rainstorms occurring in this region, K-means clustering was used to study type, characteristics and risk of rainstorms in Hekou county.
[Results]
The results show that the rainstorm is obviously seasonal, mainly from April to September, and dominated by
P
24
in Hekou county. The types of rainstorms in Hekou county can be divided into four which are the previous rainfall (Ⅰ) type, medium-term rainfall (Ⅱ) type, late-rainfall (Ⅲ) type, and even rainfall (Ⅳ) type. The type Ⅰ accounts for more than 2/3 of the total rainstorm and is the main type of rainstorm in this area. 80% precipitation of rainstorm and the larger value of average rainfall intensity generally occur within the first 0.4 cumulative rainfall duration, the first 4 hours in a day. Since this type rainstorm will cause very serious damage, it should be paid highly attention to; According to the national grade of rainstorm warning, the rainstorms are dominated by orange and yellow warnings, which accounting for 42% and 32% of the total number of rainstorm warnings respectively. In this case, the risk of hazard level is higher, which may cause mountain torrents and mudslides in Hekou county. The warning and control measures of rainstorm should be made in advance.
[Conclusions]
This study discusses the characteristics of rainstorm in Hekou county, clarifies the types of rainstorm and duration, rainfall precipitation, rainfall intensity, warning level of each type, which are helpful to the prevention of rainstorm damages in this region.
2018 Vol. 16 (6): 99-107 [
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108
LI Yiran, ZHANG Xinggang, LI Zedong, ZHANG Ruming, CHENG Tiantian, ZHANG Yongtao
Evaluation of soil and water conservation benefits of different mixed forests in hilly area of middle southern of Shandong province by TOPSIS
[Background]
Soil and water loss is one of the important factors that restrict the ecological construction and development in hilly area of middle southern of Shandong province. Based the benefit evaluation results of soil and water conservation, selecting suitable forest species and creating mixed forest are important measures for ecological environment management under different site conditions in this area. In order to better to carry out the ecological work of soil and water loss in hilly area of middle southern of Shandong province, the soil and water conservation benefits of the mixed forests in this area were comprehensively evaluated and the appropriate mixed forest model was selected.
[Methods]
Twelve types 10-year mixed forests in typical limestone and sand mountainous areas of middle southern of Shandong province were selected as the research object, and the benefits from the soil and water conservation as well as the improvement of forest stand were studied by field investigation and indoor analysis. The weights of comprehensive benefit evaluation indexes of soil and water conservation were calculated by entropy weight method, and each mixed forest mode was evaluated based on TOPSIS principle. The comprehensive benefits of soil and water conservation in different mixed forests were evaluated by combining 13 indicators of soil and water conservation benefits, and the suitable mixed forest mode for the study area was screened out.
[Results]
1) In the limestone mountainous areas, for the mixed types of arbor and shrub, the benefit of soil and water conservation of the mixed forest of
Platycladus orientalis
and
Armeniaca sibirica
was the best, the soil improvement benefit of the mixed forest of
P. orientalis
and
Cotinus coggygria
was the best. Meanwhile, for the theropencedrymion, the benefits of soil and water conservation and soil improvement of the mixed forest of
P. orientalis
and
Robinia pseudoacacia
were the best. In addition, for the comprehensive benefits of soil and water conservation based on TOPSIS method, the mixed forest of
P. orientalis
and
C. coggygria
was the best in the mixed forest of arbor and shrub, and the mixed forest of
P. orientalis
forest and
R. pseudoacacia
forest was the best in the theropencedrymion. 2) In the sand mountainous areas, for the theropencedrymion, the benefits of soil and water conservation and soil improvement of the mixed forest of
Pinus thunbergii
and
R. pseudoacacia
was the best. And for the mixed types of broadleaved and broadleaved, the benefits of soil and water conservation and soil improvement of the mixed forest of
R. pseudoacacia
and
Quercus acutissima
were the best. 3) Also, according to the results of comprehensive benefit evaluation of soil and water conservation, the mixed forest of
P. thunbergii
and
R. pseudoacacia
was the best in the theropencedrymion, and the mixed forest of
R. pseudoacacia
and
Q. acutissima
was the best in the mixed types of broadleaved and broadleaved.
[Conclusions]
The results may provide the theoretical basis for the hybrid tree species selection of the artificial afforestation in hilly area of middle southern of Shandong province. Besides, the evaluation results based on the entropy weight and TOPSIS method are in fine agreement with the results obtained in other studies, and the evaluation method is recommended in the evaluation of soil and water conservation benefits of mixed forests.
2018 Vol. 16 (6): 108-117 [
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118
YAO Chengping, ZHANG Xiaoyuan, ZHENG Guoquan, YANG Xianjie, LI Jiansheng
Zoning of key prevention and control region of water and soil erosion in Guangdong province
[Background]
The division of key prevention and control region for water and soil erosion in Guangdong province, can specified the key prevention and control points for water loss and soil erosion, and provide the basis for compiling water and soil conservation planning and water loss and soil erosion subregion prevention,also can guide the work of water and soil conservation planning at all levels in Guangdong province.
[Methods]
This paper took town-level administrative region as the basic division unit, through use GIS technology, combined with the unique natural conditions of Guangdong province,such as the characteristics of heavy rainfall and concentration and soil resistance to erosion is poor, according to relevant laws & regulations, planning and main function division of Guangdong province,at the same time analysis characteristics of soil and water loss control of Guangdong province, combine with quantitative analysis methods and qualitative analysis methods, put forward the quantitative index of the key prevention area of soil erosion, such as the ratio of light and micro area of soil and water loss, the ratio of the soil erosion potential danger area,vegetation coverage of forest and grass and so on. also put forward the quantitative index of key control region of soil erosion, such as soil erosion intensity, the ratio of the slope disintegration erosion region, cultivated land area, the ratio of the cultivated land in slope cropland and so on. Combined with qualitative analysis, structure the index system of division of key prevention and control region of soil erosion, and then divided into key control region of soil and water loss of Guangdong province.
[Results]
The results show that within the Guangdong province, delineated two provincial key prevention region,the name is the key prevention region of soil erosion of upper reaches of Moyang River and the key prevention region of soil erosion of upper and middle reaches of North River, the total area of the delineation region is 23 613.52 km
2
which accounting for 13.13% of the whole province. as well as delineated three provincial key control region, and the name is the key control region of soil erosion upper and middle reaches of Jian River, the key control region of soil erosion upper and middle reaches of Rong River and the key control region of soil erosion lower reaches of West River, the total area of the delineation region is 8 211.79 km
2
which accounting for 4.57% of the whole Guangdong province.
[Conclusions]
The results of the division of key prevention and control region of soil and water loss in Guangdong province made the key management of soil erosion more operational and convenient for meticulous management, also provides an important basis for implementing the responsibility assessment and reward and punishment system of soil and water conservation objectives at all levels of government.
2018 Vol. 16 (6): 118-123 [
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501
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124
CAO Danni, ZHONG Qi, QIN Jiahui, CHENG Liang, GUO Zhonglu
Literature review on the role of root in soil erosion control based on the knowledge map
[Background]
As the most important factor hindering the soil erosion, root plays an irreplaceable role in the process of soil erosion. At present, there are many domestic studies on the control of soil erosion by root system; however, the knowledge structure on this area is not systematically sorted.
[Methods]
In order to reveal the research and development trend of role of the root system in soil erosion control, this paper used the 1 193 articles from CNKI database during 1988 to 2017 as the original data, using bibliometrics and CiteSpace Ⅲ to map the root system resisting erosions, identify the main journals publishing the papers of this topic, top authors and institutions, sources of major funds and hotspots in different stages of this field.
[Results]
1) In the past 30 years, the number of research papers about this topic published in China showed a rapidly increasing trend. In particular, the number of papers published in 2012-2017 accounted for 43.25% of the total papers, and highly cited papers mainly were concentrated in 1990-2003. 2) The journals publishing this topic were mainly related to the disciplines of soil and water conservation, and the researches were supported by the National Natural Science Foundation of China and the National Science and Technology Support Program accounted for 25.23% of the total papers. 3) The authors showed a partially centralized, fragmented status with high-frequency authors, and the cooperation between the authors was limited to a team. 4) Studies on the intensification of soil anti-scourability by plant roots were the research hotspots in 1988-2001, and then the scientific research was dominated by root system slope protection, root system characteristics on soil permeability, and root-soil complexes. In addition, the study of root exudates, roots increasing soil infiltration rate and the temporal and spatial dynamic processes of plant community roots evolution in soil may be the focus of research in this field in the future.
[Conclusions]
Through the visual excavation and analysis of knowledge maps of the role of root in soil erosion control research, it is conducive to researchers to have a more comprehensive and detailed understanding on the history and current situation of the role of root in soil erosion control research in China. This study can provide a reference for subsequent research in this field.
2018 Vol. 16 (6): 124-135 [
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