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2018 Vol.16 No.2
Published 2018-04-30
1
HAO Haoxin, DU Yifan, CAO Danni, LI Zhaoxia, GUO Zhonglu
Experimental study of flow hydraulic characteristics and soil erosion on red soil hilly-slope
[
Background
] Soil erosion by water in red soil hilly region in tropical and subtropical zones of central China cause severe soil quality degradation and environmental issues. Soil erosion is primarily controlled by large volumes of surface runoff in this region due to abundant rainfall. Previous studies show that hydraulic characteristics are important in elucidating the mechanisms of erosion and sediment yield on slope. So far several laboratory and field experiments had conducted to understand the correlations between hydraulic parameters and soil erosion. However, most researches showed diversified results on those correlations due to various types of soils and different conditions in different experiments. The objectives of this study are to assess the difference in hydraulic parameters and sediment yield under red soil hilly-slope.[
Methods
] In order to simulate the surface runoff erosion process, an indoor experiment, involving four slopes (5°, 8°, 10°, and 12°), three flow rates (5, 7.5, and 10 L/min) was carried out in a red soil flume (3-meter length and 0.5-meter wide). The bulk density and initial moisture for the soil sample was 1.35 g/cm
3
and 30%, respectively. Experimental indices were measured by different approaches, the staining method was utilized to measure the flow velocity; the flow width was measured using a ruler at 3 positions; the sediment yield rate and discharge rate were deduced and calculated from the water bottle collected the runoff samples at the bottom of the flume during a set time interval. A single trial lasted 15 min. The hydraulic characteristics mainly used were Reynolds number (
Re
), Froude number (
Fr
), and other two different expressions of flow resistance Manning roughness coefficient (
n
) and Darcy-Weisbach friction (
f
).[
Results
] 1) Water erosion of red soil slope presented obvious periodic development process. There was short time sheet flow at the beginning, and soon transformed to rill flow. The sheet flow regimes generally indicated in transitional-sub-critical zone, and rill flow regimes indicated in transitional-super-critical zone. The unit discharge, mean flow velocity, mean flow depth,
Re
and
Fr
of sheet flow were larger than those of rill flow, while the
n
and
f
exhibited inversely in a same period. 2) The
n
and
f
of the flow varies between 0.038-0.092 and 0.73-4.41, respectively. Both
n
and
f
showed a power function with
Fr
(
R
2
=0.49;
R
2
=0.52), and besides this,
f
also showed a power function with
Re
of transitional flow (
R
2
=0.29). 4) A composition hydraulic parameter
JRe
, which was define as the product of
Re
and
J
(
J
was water surface slope), was an appropriate indicator for soil erosion. Sediment yield rate in the red soil slope could be estimated by
JR
e
with an exponential function in both sheet flow phase and rill flow phase (
R
2
=0.93;
R
2
=0.51).[
Conclusions
] The results are conducive to the comprehensive understanding flow hydraulic characteristics and provide a reference for further studies on rill erosion in red soil hilly region.
2018 Vol. 16 (2): 1-8 [
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404
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9
YANG Bo, CHEN Ying, CHEN Xingwei, LIU Meibing, GAO Lu
HSPF runoff simulation and optimization based on PEST automatic calibration
[
Background
] In recent years, water cycle and water resource change have become more complicated due to the influence of climate change and human activities. Hydrological model is an approximate simulation of complex hydrological phenomena, which can realize the quantitative study of runoff. And parameter calibration is one of the most important steps in hydrological modeling.[
Methods
] In order to improve the calibration efficiency and simulation effect of the hydrological model, Hydrological Simulation Program in Fortran (HSPF) used extensively for assessing water quantity issues was selected in this paper. The PEST automatic calibration model with single objective function (squared error of daily flow) and multi-objective functions (squared error of daily flow, squared error of monthly flow, squared error of exceedance flow time) were applied in HSPF model, and the squared error of daily flow was improved by separating wet and dry seasons. These calibration methods were compared with Shanmei Reservoir watershed, southeast China.[
Results
] 1) Multi-objective calibration performed better with respect to goodness-of-fit measures (NSE,
R
2
, RMSE and PBIAS) than single objective calibration. In multi-objective calibration, the values of the NSE were above 0.79, the values of the
R
2
were above 0.80, the values of the PBIAS were between -10% and 0%, and the values of the RMSE were <30 m
3
/s during the calibration and validation. 2) In terms of the results of two multi-objective calibration methods, when the squared error of daily flows was improved by separating wet and dry seasons, the simulation results of daily and monthly runoff were significantly improved during the dry season. Taking daily runoff simulation for example, the values of the NSE increased from -0.04 and 0.43 to 0.25 and 0.54, the values of the
R
2
increased from 0.37 and 0.59 to 0.47 and 0.64, the values of the PBIAS increased from -33.57% and -22.72% to -24.52% and -16.79%, and the values of the RMSE decreased from 9.54 m
3
/s and 8.89 m
3
/s to 8.06 m
3
/s and 7.96 m
3
/s during the calibration and validation, respectively.[
Conclusions
] The objective function has a great influence in the automatic calibration of parameters. Multi-objective calibration performed better with respect to the trend of runoff, total runoff, and flow duration curves than single objective calibration. When the squared error of daily flow is improved by separating wet and dry seasons, the problem of dry flow was neglected in traditional multi-objective calibration was solved and the simulation results of daily and monthly runoff were significantly improved during the dry season.
2018 Vol. 16 (2): 9-16 [
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393
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369
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17
LI Yishan, YIN Bin, XIE Yun, YIN Shuiqing, LIU Yuxin, ZHANG Wenbo, YIN Bing, YANG Yang, DUAN Xingwu
Methods for assessing soil erosion intensity in karst regions
[
Background
] Stony desertification in karst areas demonstrates the consequence of serious soil erosion, however, the research on the comprehensive evaluation of soil erosion in rocky desertification area is deficient.[
Methods
] Information on soil erosion factors for 44 primary sample units (small watersheds) in three counties from karst regions, Guanling (Guizhou province), Luoping and E'shan (Yunnan province) was collected by field investigation and remote sensing interpretation. Soil erosion area and intensity were assessed by the factor scoring method and model-based method. In factor scoring method, erosion factors (e.g. rainfall erosivity, soil erodibility and slope) were classified into discrete classes and scores were given to classes based on expert experiences. In model-based method, Chinese Soil Loss Equation (CLSE) was first used to calculate the soil erosion modulus, and the erosion intensity was classified based on the amount of modulus. Factor scoring and model-based methods under two different classification standards (SL190-2007 and SL461-2009) were compared.[
Results
] Average soil erosion area ratios by the model-based method and factor scoring method in SL190-2007 showed an obvious difference (35.98% and 72.40%, respectively) and those by two methods in SL461-2009 were similar (70.11% and 69.31%, respectively). When it turned to the erosion intensity, the model-based method in SL190-2007 and the factor scoring method in SL461-2009 mainly generated the slight erosion intensity, followed by the moderate, high, severe and extreme erosion intensity; whereas the factor scoring method in SL190-2007 were dominated by the moderate erosion intensity. The slight and moderate erosion intensity in model-based method from SL461-2009 dominated and occupied the similar proportion. Farmland was the largest source of erosion area in both methods and both standards. The erosion area ratio in the forest, and grassland was relatively lower by the model-based method in SL190-2007 and the factor scoring method in SL461-2009, whereas that was relatively higher by the factor scoring method from SL190-2007 and the model-based method from SL461-2009.[
Conclusions
] The model-based method in SL190-2007 is not suitable for the karst regions. The factor scoring method in SL461-2009 is more reasonable comparing with the model-based method in SL190-2007 by taking the influence of bare rocky ratio into consideration. Theoretically, the model-based method in SL461-2009 is the most reasonable by considering the effect of seven natural and human related soil erosion factors, including rainfall, soil, slope degree, slope length, vegetation and biological measures, engineering measures and tillage measures. However, the soil erodibility factor in the model-based method does not reflect the typical phenomenon of exposed bedrock in karst regions at present, resulting in the unreasonable high erosion ratio in the forest and grassland. Investigation of exposed bedrock should be carried out in the next step, and taken into consideration in the model-based method for further improving the efficiency of model-based method in karst regions.
2018 Vol. 16 (2): 17-23 [
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489
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24
YONG Chenxu, FAN Jun, WANG Sheng
Effects of slope gradient on the soil saturated hydraulic conductivity of sloping land measured by three single-ring infiltrometers
[
Background
] Soil saturated hydraulic conductivity (
K
s
) of sloping field is a key parameter to predict soil and water losses, but
K
s
is mostly measured on the flat land. Therefore, directly measuring saturated hydraulic conductivity on slopes is practically important. The objective of this paper is to study the effect of slope gradient on
K
s
by three single-ring infiltrometer methods in order to select a suitable method for slope land.[
Methods
] The slope gradients of 0, 5°, 10°, 15° and 20° in sandy soil, Loessial soil and Lou soil were selected and
K
s
was measured by three single-ring infiltrometer methods (i.e., two-ponding depth, one-ponding depth and BEST methods), which usually were used for flat lands. All measurements were conducted on undisturbed soil.[
Results
] 1) On flat soil surface, all three methods obeyed the same order for
K
s
of different soils as sandy soil > Loessial soil > Lou soil. The
K
s
of three soils by single-ring BEST infiltrometer were 2.9, 2.1 and 4.5 times, which were larger than those by single-ring two-ponding depth infiltrometer. If cutting-ring infiltrometer was taken as standard, single-ring BEST infiltrometer significantly overestimated the
K
s
of the Loessial and Lou soil, but the results by single-ring two-ponding depth infiltrometer and single-ring one-ponding depth (10 cm) infiltrometer were close to that by cutting-ring infiltrometer. 2)
K
s
measured by single-ring two-ponding depth infiltrometer increased with the increase of slope gradient and there was a significant linear correlation between them. The
K
s
of three soils by single-ring BEST infiltrometer decreased with the increase of slope gradients and this method was affected distinctly by slope gradient due to the change of the ponded water area inside the ring. 3) Under flat ground condition, the results of single-ring one-ponding depth (10 cm) infiltrometer were comparable to single-ring two-ponding depth infiltrometer, but the single-ring one-ponding depth (5 cm) infiltrometer overestimated the results. 4) In sandy soil, Loessial soil and Lou soil, there was no significant difference of
K
s
between slope<10° and flat land by above 3 methods, but significant while slope >10° (
P
<0.05).[
Conclusions
] Therefore, single-ring BEST infiltrometer is not suitable for measuring
K
s
in sloping field. Single-ring two-ponding depth infiltrometer or single-ring one-ponding (10 cm) depth infiltrometer can be used to correctly measure
K
s
if the slope is <10°. Furthermore, the calculating equations for saturated hydraulic conductivity by these sing-ring methods should be revised for the three soils in the loess regions if the slope gradient is >10°.
2018 Vol. 16 (2): 24-30 [
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] (
581
) [
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412
)
31
ANARGUL·Mamtimin, ALIMUJIANG·Kasimu, MAIERZIYA·Wumaier
Analysis of landscape pattern change in Urumqi built-up area based on moving window method
[
Background
] Urban landscape is the most important concern in the study of the current urban landscape pattern, and it is also one of the fastest dynamic changes in the surface landscape. The study area is Urumqi, the capital and the centre of culture, economy and transportation in Xinjiang Uyghur Autonomous Region, located in north-western China and characterized by an arid landscape. With the rapid development of urbanization in Urumqi, the contradiction between urban layout and the structure of land use is becoming increasingly sharp. The objective of this paper is to study the formation, distribution pattern and transformation of each landscape pattern in Urumqi city during last 25 years, and to provide scientific and reasonable references for the landscape management and sustainable development of the city.[
Methods
] According to the characteristics of the city development and environmental factors in Urumqi, a reasonable and effective use of moving window method is to analyze the spatial layout and internal level difference of landscape fragmentation in Urumqi built area. Transferring matrix and landscape indexes (patch density, largest patch index, landscape separation index, number of patches, Shannon's diversity index, patch area, and landscape area) are used to analyze spatial-temporal changes of landscape fragmentation and dynamic changes in Urumqi city based on the data source Landsat TM/ETM+, OLI images taken at the same month in 1990,2002 and 2014.[
Results
] 1) The changes of landscape types in Urumqi during the past 25 years mainly are the increase of landscape area and the transformation between different types of landscape, which shows obvious temporal and spatial changes. 2) Speed of urbanization and the degree of landscape fragmentation has increased, the dominance has reduced, and the heterogeneity has risen. The degree of landscape fragmentation is aggravated, and landscape types tend to be more diversified. 3) In 1990, the city is in a development stage, and the level of urbanization is low. In 2002, the speed of urban expansion has increased significantly, and the level of urbanization has improved. In 2014, the urban expansion is faster, the level of urbanization is higher, and the city is in a stage of rapid development.[
Conclusions
] In the recent 25 years, with the rapid development of urbanization in the research area, the total area of each landscape type shows increasing trend, human impact has intensified, the fragmentation of landscape has strengthened, diversifying trend has occurred, and dominance degree has decreased. The research may provide a scientific and reasonable reference for landscape management and urban sustainable development in the intensively developed arid urban landscape of Urumqi.
2018 Vol. 16 (2): 31-38 [
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437
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39
YANG Liu, CAI Wentao, LAI Liming, ZHOU Jihua, JIANG Lianhe, ZHENG Yuanrun
Characteristics of soil nutrients in abandoned croplands at different abandoned years in the Ordos Plateau
[
Background
]:Plant community succession and soil nutrients change affects each other, and it is significant to research soil nutrient change in abandoned croplands with different years for us to understand plant community succession process.[
Methods
] Abandoned croplands at different years in the regions of Ruanliang and Yingliang in the Ordos Plateau, China, were selected (abandoned time was 1, 6, 10, 15, and 20 years in Ruanliang; and 3, 6, 10, 15 and 20 in Yingliang) to conduct field investigation for analyzing change of soil nutrients during vegetation succession.[
Results
] In the abandoned cropland in Ruanliang, except fluctuations of total carbon and total potassium, soil total nitrogen and total phosphorus increased gradually with increasing abandoned years, while total nitrogen and total phosphorus decreased with increasing soil depth. In the abandoned cropland in Yingliang, with increasing abandoned years, soil total carbon increased and then decreased generally; soil total nitrogen decreased and then increased at 0-10 cm soil layer, increased and then decreased at other soil layers; soil total phosphorus increased and then decreased at 0-30 cm soil layer, decreased and then increased at other soil layers; soil total potassium increased and then decreased at 0-10 cm soil layer, decreased at other soil layers. With increasing of soil depth, total carbon decreased in 20 year's abandoned cropland and natural vegetation, increased in other year's abandoned croplands; soil total nitrogen fluctuated in 6 year's abandoned cropland, decreased in other years' abandoned croplands; total phosphorus decreased and then increased in 10 years' abandoned cropland and natural vegetation, decreased in other year's abandoned croplands; soil total potassium did not show obvious changing trends. With the increasing abandoned years, soil C/N decreased, then increased, decreased finally in the abandoned cropland in Ruanliang and Yingliang. With the increasing soil depth, soil C/N decreased in natural vegetation, increased in other years' abandoned croplands in the abandoned cropland in Ruanliang; soil C/N increased in the abandoned cropland in Yingliang.[
Conclusions
] During vegetation succession, abandoned yeas and soil depth had significant effects on soil nutrients, and soil nutrient was higher in surface soil layers. The study provids scientific basis for vegetation restoration of abandoned cropland in the Ordos Plateau.
2018 Vol. 16 (2): 39-46 [
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558
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47
WANG Jingjing, BI Huaxing, SUN Yubo, DUAN Hangqi, PENG Ruidong
Shade range analysis of apple tree crown in different ages
[
Background
] Agroforestry complex system has obvious ecological benefits of soil and water conservation in the Loess Plateau region. Recently, the research about agroforestry complex focused on the competition of water and nutrient, and neglected effects of solar radiation. Solar radiation is energy sources of intercropping, and crown shading should be focused in agroforestry complex system. Jinxi is a typical Loess Plateau region, where agroforestry complex is widely used. Thus, this study, measuring crown shadings of different age's (4 years, 5 years, 6 years, and 7 years) apple trees in Jinxi Loess Plateau area, aims to explore shading range that is shade area at corresponding moment within a day, repeated shading area that is an area continuously covered by apple tree crown within a day, and lasting shading time in a repeated shading area on different ages apple tree.[
Methods
] Based on similarity principle in parallel solar rays, the research established 3D apple tree model by reducing the 50 times of an actual apple. Apple tree shading range in a day was measured using the 3D tree. The shade was described based on the shadow of the 3D apple tree model in solar rays. The drawing describing shade range was imported to computer, and combining the software of CAD and MATLAB, the crown shade of apple tree within a day was analyzed.[
Results
] 1) As for the tree planting configuration with the plant spacing was 4 m×5 m,5 m×5 m in the study area, the 4-7 years apple trees had mutual shading overlap between apple trees, but no mutual shading overlap occurred between rows. The research about multiple apple trees configuration should focus on apple trees in economic tree and crop intercropping system. 2) The crown shading area of the apple tree in north side was always greater than that in the south side. Consequently, planting intercrops at the same distances in north and south side of apple trees was not reasonable in economic tree and crop intercropping system. When designing the row distance of intercrop, we must consider the effect of apple tree crown shading area. In the study, the reasonable intercrop planting distance was determined through analyzing apple-tree crown shading area, repeated shading area, and lasting shading time. 3) Because repeated shading area continuously increased with the increase of an apple tree age, which resulted in the competition of solar rays between tree and crop rose with the aging of the tree. While the crown shading area of an apple tree is getting closer to the apple tree, the shading time of the shading area increased. Therefore, the competitiveness for solar rays between tree and crop became growingly significant with the crown shading area was toward to the tree. And the major shading time should be in 9:00-15:00 within a day, and this moment was the important in a day.[
Conclusions
] Intercrop planting should be determined based on shading area in economic tree and crop intercropping system. And planting area of intercropping is different in economic tree and crop intercropping system with different ages' apple trees. The research provides support about reasonable planting distance of intercrop in economic tree and crop intercropping system.
2018 Vol. 16 (2): 47-54 [
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521
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450
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55
LIU Hongyan, ZHOU Zhengchao, WANG Ning, LI Chao, QIN Miao
Soil anti-scourability at early growth stage of grasses and its influencing factors in loess region
[
Background
] The loess region is one of areas with serious soil erosion in China. Grasses restoration plays an important role in controlling soil and water loss in loess region. Yet there were few researches about soil anti-scourability of different planting densities grasses at early growth stage and its influencing factors in this region.[
Methods
] The indoor potting experiment and undisturbed soil sample scouring experiment were conducted in this study. Three treatments were set up, i.e., bare land (CK), low planting density of
Lolium perenne
L. (H1, 204 plants/m
2
), and high planting density of
L. perenne
L.(H2, 612 plants/m
2
). Each treatment had three replicates. There were nine soil samples that had grown 12 weeks. Three soil layers (i.e., surface 0-20 cm, subsurface 20-40 cm, and bottom 40-60 cm) were selected to study the change of soil anti-scourability index (I
AS
), soil density, organic matter mass fraction, aggregate mass fraction and root surface area density. Undisturbed soil samples were collected by a special sampler (20 cm×10 cm×15 cm), and the collected soil samples were soaked with water plate and removed from gravity water, then the soil anti-scourability test was carried out. The flow rate was applied at 3 L/min discharge on a scouring flume slope of 15° for 15 min.[
Results
] 1) The soil density, organic matter mass fraction, and aggregate mass fraction of CK treatment changed little in three soil layers. The soil density, organic matter mass fraction, aggregate mass fraction and root surface area density of H1 and H2 treatments changed in different degree, and the change of physiochemical properties of surface soil was most obvious. 2) Compared with the CK treatment of the same soil layer, I
AS
of H1 and H2 treatments increased significantly in surface soil layer, and decreased with the increase of soil layer depth, and surface soil of H2 treatment had the most significant effect on soil anti-scourability. 3) Except CK treatment, I
AS
of H1 and H2 treatments had a correlation with soil physiochemical properties and root surface area density (
P
<0.05), but there were some differences in the influencing factors of I
AS
.[
Conclusions
] In summary, planting grasses may improve soil physiochemical properties and soil anti-scourability, and the high planting density had more capacity to enhance the soil anti-scourability at early growth stage of planted grasses. These results indicate that planting grass may enhance soil anti-scourability especially with a high density, and these results provide a theoretical reference for the selection of planting density at early stage of grasses restoration in loess region.
2018 Vol. 16 (2): 55-61 [
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62
MA Xiaohui, ZHANG Yan, TANG Jie, FAN Conghui
Composition and distribution characteristics of vegetation in different natural restoration periods in semi-arid loess region
[
Background
] After decades of returning farmland to forests and grasslands, vegetation in semi-arid loess region has been significantly restored. Investigating the dynamics of plant community during natural restoration process could be helpful in managing the ecosystem and further promoting the restoration rate.[
Methods
] A hill top of 8.89 hm
2
enclosed around 25-32 years was taken as the study area and geostatistical analysis was applied to explore the changes of species composition and structure and spatial heterogeneity of the plant community based on 31 plants quadrats of 1 m×0.5 m in 2009 and 2016 respectively.[
Results
] 1) From 2009 to 2016, 16 new species were found while the life form was still mainly concentrated in perennial herbaceous plants in whole slope. With the dominated species changed from
Artemisia sacrorum, Artemisia leucophylla, Stipa capillata, Lespedeza bicolor
and
Artemisia frigida
to
Artemisia sacrorum, Carex tristachya, Cleistogenes chinensis, Lespedeza bicolor
and
Artemisia frigida
. The dominance of subshrub increased significantly. 2) The average biomass of the quadrats in 2009 (98.57 g/m
2
) was significantly different that in 2016 (141.27 g/m
2
) in the level of 0.01. The differences of biomass on lower slopes and upper slopes became smaller in 2016 indicating that environmental factors had less impact on vegetation growth. 3) The species diversity index increased significantly. The average values of Margalef index,Shannon-Wiener index and Pielou index increased from 1.361, 1.510 and 0.764 in 2009 to 1.831, 1.716 and 0.841 in 2016, indicating that the community became more stable. Compared to other site types with the species diversity increased remarkably, the species diversity index in lower-semi-sunny slope had little change indicating that the community had almost reached a steady state. 4) Compared to 2009, spatial autocorrelation of plant coverage, height, biomass and ratio of dry to fresh became weak in 2016. The spatial autocorrelation of Margalef index changed from strong to weak and the autocorrelation distance was about 60 m. Shannon-Wiener index did not show significant spatial autocorrelation both in 2009 and 2016. The spatial autocorrelation of Pielou index changed from positive correlation to negative. It indicates that the spatial variability of plant richness increased while the spatial variability of plant homogeneity decreased. Overall, plant species were richer, the spatial distribution was more uniform and community stability was enhanced on the investigated slope.[
Conclusions
] From 2009 to 2016, the number of species in the study area increased and the species diversity index showed an increasing trend. The plant life-form of perennial herbaceous plants still dominated in the study area. Results indicated that the community on the hill top became more stable but not reached to a steady state after 32 years of natural restoration and human intervention is necessary to accelerate the natural restoration rate.
2018 Vol. 16 (2): 62-72 [
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505
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73
LIU Panwei, GAO Peng, LIU Xiaohua, LIU Shengtao, NIU Xiang, WANG Bing
Spatial distribution and influential factors of soil carbon and nitrogen in Dagangshan Watershed
[
Background
] Soil organic carbon (SOC) and soil total nitrogen (STN) are both important ecological factors in terrestrial ecosystems and important elements of global carbon and nitrogen cycle and climate change research. So far, there are many studies on the spatial distribution characteristics of soil carbon and nitrogen elements and their influencing factors in different scales or land use patterns at home and abroad. However, the methods are mostly based on ordinary Kriging and regression Kriging interpolation. There are few studies on the spatial distribution characteristics of soil carbon and nitrogen elements and their influencing factors based on the comprehensive effects of vegetation and topographic factors.[
Methods
] In order to study the spatial heterogeneity distribution of soil carbon and nitrogen elements in Dagangshan Watershed of Jiangxi province, the topsoil of the watershed was studied with ZY-3 remote sensing image as the basic data source. Based on ESRI ArcGIS 10.2 platform, NDVI and related terrain factors were extracted to establish the correlation model between SOC, STN and vegetation and topographic factors, so as to analyze the spatial distribution characteristics of soil carbon and nitrogen elements. In addition, topographic factors such as elevation, slope, terrain wetness index, water power index, and sediment transport index were selected to analyze their influence on SOC and STN spatial distribution.[
Results
] 1) The average contents of SOC and STN were 25.55 g/kg and 1.61 g/kg respectively, and the coefficients of variation were 64.16% and 28.37% respectively. Both SOC and STN were of moderate variation. 2) Vegetation and topographic factors had a significant spatial correlation with SOC and STN, and the spatial distribution of SOC and STN were constructed based on NDVI, elevation, and terrain wetness index which showed SOC and STN decreased from northwest to southeast, which was consistent with the spatial distribution of NDVI and DEM. 3) The contents of SOC and STN were significantly and negatively correlated with water power index and sediment transport index, but positively correlated with NDVI, elevation, slope, and terrain wetness index.[
Conclusions
] The above results prove that the spatial distribution of SOC and STN of the topsoil in the Dagangshan Watershed are determined by NDVI and terrain factors. The general trend of NDVI distribution in the distribution pattern of different vegetation types in the basin is gradually decreasing from northwest to southeast. At the same time, elevation, slope and TWI are decreasing from northwest to southeast, while WPI and STI are opposite. The above factors affect the spatial distribution pattern of SOC and STN in the watershed. The results may provide a reference for the spatial distribution of soil carbon and nitrogen in forest soil and the quantitative evaluation of soil and water conservation in the red soil region of southern China.
2018 Vol. 16 (2): 73-79 [
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504
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360
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80
GUO Wei, ZHANG Luan, LIU Shuang, ZHANG Lingyun
Characteristics of soil moisture and grain size in different plantation types in windy and sandy area of North Shanxi
[
Background
] Windy and sandy region of North Shanxi where the severe water erosion and wind erosion happened is the most extremely frail eco-environment of Shanxi province. In the past few decades, large areas of plantations have been planted here for windbreaks and sand fixation. However, at the same time as it works, plantations can also absorb lots of water from soil and lead to soil desiccation. Jiajiayao catchment, located in Youyu County, is one of the most typical ecological fragile areas in windy and sandy region of North Shanxi province.[
Methods
] Due to soil moisture and grain size are the limiting factors for ecosystem restoration in this area, based on the field investigation, sampling and measurement, the characteristics of soil moisture and grain size of 6 different plantation types(11-year
Pinus tabulaeformis
, 21-year
P. tabulaeformis
, 23-year
Larix principis-rupprechtii
, 17-year
P. tabulaeformis
and
Caragana korshinskii
,
C. korshinskii
and
Hippophae rhamnoides
) in Jiajiayao catchment was analyzed in order to provide useful references for vegetation restoration.[
Results
] 1) There were considerably differences in characteristics of average soil moisture content in 0-100 cm soil profile among different plantation types. Mean soil moisture content of individual plantation type was about 4.62%-8.30%, and showed following sequence:
Hippophae rhamnoides
> 11-year
P. tabulaeformis
>
C. korshinskii
> 17-year
P. tabulaeformis
and
C. korshinskii
>23-year
L. principis-rupprechtii
> 21-year
P. tabulaeformis
. Mean soil moisture content in the topsoil (0-20 cm) among 6 plantation types was relatively low. Thereafter the pattern of variation began to be inconstant with the increase of depth. This may be explained by that the antecedent precipitation was in the uniform condition, while affected by plant transpiration, depth and density of root distribution, soil moisture content became complicated in deeper soil layers. 2) The grain size characteristic of all 6 plantation types was similar that silt and very fine sand content was the highest. However, silt content was the highest at
C. korshinskii
and
H. rhamnoides
, very fine sand content was the highest at the other plantation types. 3) The variation tendency of the grain size of different plantation types was not consistent in 0-100 cm soil profile. For the average grain size, the order was:23-year
L. principis-rupprechtii
> 11-year
P. tabulaeformis
> 21-year
P. tabulaeformis
> 17-year
P. tabulaeformis
and
C. korshinskii
>
H. rhamnoides
>
C. korshinskii
.[
Conclusions
] The water-holding capacity of
H. rhamnoides
and
C. korshinskii
was much better than the other plantation types.
H. rhamnoides
and
C. korshinskii
should be given priority in the process of vegetation restoration in windy and sandy region of North Shanxi. After years of vegetation restoration, the water consumption of plantations had increased in the study area. It was necessary to carry out the scientific management according to the soil water status, water consumption characteristics, and growth stages of plantations, such as adjusting the vegetation coverage and strengthening the protection of the undergrowth herb layer and litter layer.
2018 Vol. 16 (2): 80-87 [
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481
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88
ZHANG Jinghua, GAO Hui, OUYANG Yuan, ZHANG Jianlong
Sensitivity evaluation of soil erosion in Qianxi county of Guizhou province
[
Background
] Qianxi county of Guizhou province is an important ecological barrier and plays an important role in ensuring the ecological security of the Wujiang River Basin. However, as a typical mountainous county in karst region, carbonate rocks are more than 90% of the area of Qianxi county, and affected by various reasons, thus the ecological environment is fragile. In this paper, the sensitivity evaluation of soil erosion was carried out, in order to provide the basis for soil and water conservation and ecological environment construction.[
Methods
] The geological environment of Qianxi county is characterized by wide distribution and high purity of carbonate rocks, and karst rocky desertification. Therefore, the soil erosion in Qianxi county is different from that of non-karst areas. In addition to rainfall, topography, soil and vegetation influence, soil loss tolerance and bareness of bedrocks closely related with the geological background should also be considered. Therefore, rainfall erosion, slope gradient, soil texture, vegetation types, soil loss tolerance and bareness of bedrocks were selected as indicators to evaluate the sensitivity of soil erosion, under the support of ArcGIS. First, the single factor sensitivity evaluation of soil erosion was carried out. Second, all factors of soil erosion sensitivity were carried out by overlay analysis. And then the relationship between soil erosion sensitivity and geological background was analyzed from the structure and lithology.[
Results
] 1) The soil erosion in Qianxi county was mainly slight and moderate sensitive, accounting for 68.93%, and the sensitivity of soil erosion was low in the whole county, but rather high in some areas. The strongly and extremely sensitive areas were mainly distributed in Dingxin, Tieshi, Shajing, and Jinxing towns. Dingxin is the most sensitive town. 2) The geological background had a profound impact on the soil erosion sensitivity of Qianxi county. The structure indirectly influenced the soil erosion sensitivity by controlling the distribution of landform and lithology. The lithology directly determined the sensitivity of soil erosion. With the content of carbonate rocks increased, the more sensitive soil erosion was. The strongly and extremely sensitive areas were mostly distributed in the carbonate rock areas.[
Conclusions
] Through the study, we understand that soil loss tolerance and bareness of bedrocks should be used as the important indicators to evaluate the sensitivity of soil erosion in the karst area. At the same time, this study may also provide the basis for the soil and water conservation and ecological environment construction in Qianxi county. We suggest to carrying out the comprehensive control of soil and water loss in the strongly and extremely sensitive areas of soil erosion in order to maintain the residual soil.
2018 Vol. 16 (2): 88-94 [
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438
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95
ZOU Yang, HU Guohua, YU Zexing, GU Qingfu, CHEN Xiao, NING Maijin
Application of HEC-HMS model for mountain flood forecasting in the Wushui Basin
[
Background
] Mountain flood disaster often leads to heavy economic losses, even casualties. The integration of hydrological model system with Geographic Information System (GIS) and remote sensing technology provides a new perspective for mountain flood forecast. By using Wushui Basin in the Xiangjiang Basin as an example, this study investigated the application of HEC-HMS model for mountain flood.[
Methods
] Based on the land-use classifications derived from the 2010 TM remote sensing images, the mountain flood process was simulated by using semi-distributed hydrological model. According to the DEM and the outlet locations in the basin, the study area was divided into a set of sub-basins. The topographic information like the length of the river, sub-basin area, the longest flow path slope and other characteristic parameters were extracted by using remote sensing image and GIS technology. Meanwhile, the rainwater and the runoff database were established in the visual data storage system HEC-DSSvue. The rainfall and flow time series of typical floods in the period from 2000 to 2014 were interpolated and converted into regular time series based on the mathematical function of HEC-DSSvue. In addition, according to the actual situation of the study basin, the SCS runoff curve number extension was applied to calculate the runoff volume. The SCS unit hydrograph method and the exponential recession method were selected for calculating direct runoff and base flow. The Muskingum method was used to guide flow routing. Moreover, the model parameters were calibrated by the 17 observed flood events from 2000-2008, and the 10 observed flood events from 2009-2014 were used to validate the performance of the model. The good-of-fit between simulated and observed flood events were evaluated by using the relative error and the Nash-Sutcliffe coefficient.[
Results
] The results showed that the relative errors of peak flow were less than 20% and the time errors of peak flow were within 1 hour. the absolute average Nash-Sutcliffe coefficient was 0.816 in the rate period, indicating that the calibrated hydrological parameters in model were accurate and effective. Furthermore, There was only 10% of the 10 flood events having a relative error of peak flow more than 20% in the validation period. The time errors of peak flow in all the flood events were within 1 hour, the Nash-Sutcliffe coefficient of all the floods was larger than 0.7.[
Conclusions
] The simulated flow agreed well with the observed flow at the outlet of the Wushui Basin, and the model also performed well in the basin. In addition, compared to multi-peak flood, the HEC-HMS model showed a better performance in the simulation of single peak flood.
2018 Vol. 16 (2): 95-102 [
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309
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285
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103
BAI Yong, DU Jing, YANG Tingting, WANG Zhengxuan, QIU Jinliang, LI Jing
Effects of different soil and water conservation measures on soil and water loss from rocky desertification area
[
Background
] Karst rocky desertification is a process of land degradation involving serious soil erosion, extensive exposure of basement rocks, drastic decrease in soil productivity, and the appearance of a desert-like landscape. The process is expanding rapidly, and it is daily reducing the living space of residents and is the root of disasters and poverty in the Karst areas of southwestern China. Although some profitable experience has been conducted, scientific evaluations and effective remedial actions have not been carried out.[
Methods
] These experiments were conducted in Guanmaidi small watershed of Zhanyi County, Yunnan Province, where rocky desertification was severely suffered. We compared the difference of runoff and sediment yield characteristics after taking different measures in 5 runoff plots under different vegetation arrangements (soil and water conservation forest, economic fruit forest, slope farmland(
Pennisetum
sp.), terracing farmland, and wild grassland).[
Results
] 1) Under the condition of the same rainfall, soil and water conservation measures played a key role in reducing soil erosion. The flow of rain at slope farmland was the most while soil and water conservation forest was the least. Under different soil and water conservation measures, the descending order of soil erosion was as wild grass land, slope farmland (
Pennisetum
sp.), terracing farmland, economic fruit forest, and soil and water conservation forest. The amount of soil erosion in the total erosion amount were 65.00%, 56.13%, 52.43%, 50.35% and 46.03%, respectively. 2) The measures of soil and water conservation improved the soil environment to a better condition. In soil and water conservation forest, economic fruit forest, terracing farmland, and slope farmland, soil bulk density decreased while soil porosity increased and soil structure was improved. 3) The measures of soil and water conservation also improved the nutrient content of rocky desertified soil. The effect of slope tillage measure on improving soil total nitrogen and total phosphorus content was the highest, then the second for soil and water conservation forest and economic fruit forest, and the lowest for wild grassland. Specifically, the content of soil total nitrogen of slope farmland, economic fruit forest, soil and water conservation forest, terracing farmland increased by 90.63%, 74.48%, 26.56%, 22.4%, and the soil total phosphorus of them increased by 123.64%, 96.36%, 67.27%, 16.64% compared with wild grassland.[
Conclusions
] In our data, soil and water conservation forest acts the best role in combating rocky desertification in this area, and then followings are economic fruit forest, slope farmland, terracing farmland. Our result provided a case study on combating rocky desertification in Southwest China, and helped to explore and improve the management of soil and water conservation in Karst area. Further study should be considered to combine soil and water conservation measures with industrial crops, such as using fruit tree forests or timber forests to combat rocky desertification in this area. Moreover, quantitative analysis of the pattern, process and evolutional mechanism of Karst rocky desertification will be the trend.
2018 Vol. 16 (2): 103-110 [
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439
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397
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111
YUAN Zhongyou, WU Jialong, LIU Chun, DAI Jinjun, YUAN Jiaming, DAI Jun
Comprehensive effects of temporary used land in expressway construction on soil quality
[
Background
] Expressway construction will temporarily occupy and destroy part of the land, and bring damage to land resources, such as soil erosion and other resources and environmental problems. Compared with natural soil, the soil quality of temporary used land becomes worse; moreover, only basic physical and chemical properties are considered in the restoration, and neither the enzyme activity index, nor the correlation among affecting factors. Thus ecological restoration and reclamation of those temporary lands are not so effective.[
Methods
] In order to effectively reclaim and ecologically restore the temporary land damaged by Jianglou expressway engineering construction in Guangdong Province, the T test and Principal Component Analysis (PCA) via SPSS 17.0 SAS 9.0 software were used to study the changes of soil quality in 5 kinds of temporary used land, such as pioneer road,mixing station,construction camp, spoil ground and borrow pit, as well as the difference of soil quality among 5 temporary lands.[
Results
] 1) The soil organic matter, total nitrogen (N), available N, phosphorus (P) and enzyme activities (soil invertase, urease, acid phosphatase, and catalase) in the soil from borrow pit were the lowest, and the soil acidification was also the most severe. 2) The soil damaged by construction camp had the highest organic matter, total N, available N and P. 3) The highest soil bulk density and compaction, the porosity and field capacity in the soil from the mixing station were the lowest. 4) The spoil ground soil had the lowest soil bulk density and minimum compaction, lower organic matter content, total N, available N and P, but the highest available K. 5) The higher level of soil organic matter content and other nutrient content was found in the soil from pioneer road, while soil bulk density and soil porosity, moisture content and field capacity were lower in this soil (
P
<0.05). The differences in the soil quality among the soils affected by different use of highway temporary construction were extremely significant (
P
<0.001).[
Conclusions
] Lack of organic matter, total N, available N, P content and the decrease of enzyme activities are the major limiting factors for land reclaim and ecological restoration of soils from borrow pit and spoil ground. The increased compaction and soil bulk density, and decreased porosity and field capacity are the major limiting factors for the land reclaim and ecological restoration of soils from construction camp, mixing station and pioneer road. PCA reveals that the comprehensive quality of soils from borrow pit and spoil ground is significantly different from that of soils from the other three sites. Targeted measures for soil improvement should be taken to temporary land. PCA is a robust tool to distinguish the properties of soils under different temporary construction land and to explore the key factors of soil amelioration. The study provides a theoretical basis for reclaim, ecological restoration and soil erosion control in land damaged by engineering.
2018 Vol. 16 (2): 111-118 [
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594
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348
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119
XUE Zhibin, LI Ling, ZHANG Shaokai, DONG Jing
Comparative study between Nemerow Index Method and Compound Index Method for the risk assessment of soil heavy metal pollution
[
Background
] The accumulation of heavy metals in soil will influence the physical and chemical properties of soil, leading to soil structure damage and soil and water loss. Furthermore, along with the function of food chain, heavy metal pollutants can migrate to animals and plants, as well as human beings, which is harmful to food safety and human health. The sustainable development of economy and human health are seriously endangered by soil heavy metal pollution. Thus the risk assessment of soil heavy metal pollution is an important basis and premise for solving this problem.[
Methods
] There are many methods for assessing the risks of soil heavy metal pollution, in order to explore the differences among different assessment methods and the reasons for the differences of the results, as well as to choose a more reasonable and operable method, we calculated Nemerow index and compound index according to single factor index. We used ArcGIS to overlay the spatial variation of Nemerow index and compound index and obtained the areas with different levels. Then we compared and analyzed the results.[
Results
] According to Nemerow Index Method, 1.73% of the study area was slight pollution, with an area of 292.87 hm
2
, and 0.15% of the study area was moderate pollution, with an area of 24.82 hm
2
. The result based on Compound Index Method indicated that the areas with slight pollution, moderate pollution and heavy pollution were 494.74 hm
2
, 138.71 hm
2
and 11.30 hm
2
, respectively, which were 2.92%, 0.82% and 0.07% in percentage. The results of above-mentioned two methods were inconsistent in the region of 739.12 hm
2
(i.e. 4.36% of the study area). The warning area based on Nemerow index and the compound index slight pollution were overlapped in 1.93% of the study area, whereas Nemerow index slight pollution area and the moderate pollution area according to compound index were overlapped in 0.74% of the area. The overlap areas for these two cases were 327.05 hm
2
and 125.18 hm
2
, respectively. At the same time, 0.07% of the study area, with an area of 11.30 hm
2
, was predicted to be moderate pollution according to Nemerow index, and was estimated as heavy pollution area using compound index. We selected 4 spots for the areas with inconsistent estimations using a random function. The Nemerow index of spot b was 0.811, indicating a level of warning; while the compound index was 1.038, indicating slight pollution.[
Conclusions
] Nemerow Index Method will reduce its index in the calculation process. And when the maximum of single factor is large, but the average index is small, Nemerow Index Method may reduce the level. Compound Index Method can avoid these problems. Therefore, Compound Index Method can reflect the regional soil environmental quality more objectively and reasonably, thus it should be popularized and used in practical work.
2018 Vol. 16 (2): 119-125 [
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474
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314
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126
YUAN Ying, WANG Shanhe, MA Ning, GUAN Bin, HAO Huili, REN Jingzhu
Configuration proportion of soil and water conservation measures in Shaanxi province
[
Background
] The proportion of measures to conserve soil and water in Shaanxi province is a necessity while determining the quantity of water-and-soil conservation measures in the whole province defined in
Regulations of Conserving Soil and Water in Shaanxi province
, which has important guiding meanings to scientifically make allocation plans of comprehensively controlling measures for conserving soil and water in small watersheds and for improving the efficiency of soil and water loss control. To conduct researches about the proportion of water-and-soil conservation measures in Shaanxi province and to determine the types and quantities of water-and-soil conservation measures based on local conditions has important realistic meanings in constructing ecological civilization at local regions and promoting the regional economy.[
Methods
] With the summary of the already implemented comprehensive controlling projects of conserving soil and water in recent years in Shaanxi province, this study chose typical and representative small watersheds to conduct actual investigation regarding different regions based on the regulations of soil and water conservation in Shaanxi province. According to the coverage, types and quantities of measure of the already existed water-and-soil conservation measures at typical small watersheds, as well as the regulated coverage, types and quantities of measures, we calculated the proportions of water-and-soil conservation measures in all regions after actual verifications.[
Results
] On the basis of the proportions of measures in all regions and using the controlling coverage and weighted mean, the proportion of the already-taken measures in Shaanxi province is that the major six measures such as the prime farmland (including terrace, dam land and other water-and-soil conservation measures), arbor forest, shrub forest, economic forest, grass-growing and enclosing treatment take 22.3%, 27.7%, 17.2%, 14.0%, 8.3% and 10.5% respectively. Among the already controlled water-and-soil loss area of 1 000 km
2
, there are 35 large dams, 125 medium-sized dams, 297 small dams, 245 km long cut ditches and 9 209 reservoirs. The proportion of regulated measures is that the major six measures such as the terrace, arbor forest, shrub forest, economic forest, grass-growing, and closed treatment take 5.6%, 12.3%, 11.7%, 6.7%, 4.7% and 59.0% respectively. In every controlled water-and-soil loss area of 1 000 km
2
, it needs to build 29 large dams, 66 medium-sized dams, 255 small dams, 354 km long cut ditches and 93 ponds. All these need to be allocated to the current 12 cities (or regions) in Shaanxi province.[
Conclusions
] The index of the proportion of water-and-soil conservation measures in Shaanxi province may provide a basis for the municipal regulating work of water and soil conservation in future and serve as a reference for the management of comprehensive controlling projects of water and soil loss invested by national, the provincial and the city-level governments.
2018 Vol. 16 (2): 126-133 [
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549
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350
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134
KE Qihua, ZHANG Keli
A review on the erosion-related researches by simulated rainfall experiments in China
[
Background
] Simulated rainfall experiment is an important method in the mechanism study of soil erosion process due to its characteristics of easy control and study process expediting, and it has been applied around the world since the 1960s.[
Methods
] We collected all relevant literatures from databases etc., and made a statistical analysis of the literatures of erosion-related researches by simulated rainfall experiments from the aspects of time courses, spatial distribution, research topics, test-bed types, rainulator types, research methods, research facilities and their distribution in China.[
Results
] 1) In China, the application of simulated rainfall in the domain of soil erosion relevant can be divided into three phases:initial stage throughout the 1960s and 1970s, slow developing stage throughout the 1970s and 80s and the high-speed development after entering the 21st century. 2) In China, the erosion-related researches by simulated rainfall experiments focus on the Loess Plateau, the main tested soil types are loess, red soil, purple soil, black soil and limestone soil, the hot research topic is about rill and interrill erosion, the primary test-bed type is the uniform slope, the major type of rainulators are the side-spraying and down-spraying with stationary nozzles. 3) Involved research facilities and documents are concentrated in Beijing and Shaanxi, respectively. Research institutions headed by Institute of Soil and Water Conservation of Chinese Academy of Sciences, colleges and universities represented by Northwest Sci-Tech University of Agriculture and Forestry, are the main force of erosion-related researches by simulated rainfall experiments in China, some experiments stations and administrative units are also involved in the flood. At last, the problems existing in the artificial rainfall test methods and its future direction are proposed respectively from the aspects of rainfall devices and simulation methods. To elevate values for application and universalization of soil erosion simulation experiments results, it is a necessary path to ascertain erosivity parameters of various rainulators and to normalize operating methods of simulated rainfall experiments.[
Conclusions
] These findings of the study could provide basic research datum for the exact grasp of research methods of soil erosion simulation experiments and a better acquaintance with the scientific research and practical work on water and soil conservation in China.
2018 Vol. 16 (2): 134-143 [
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542
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144
BAO Yanfeng, YANG Liu, LONG Chao, KONG Zhe, PENG Peng, XIAO Jun, JIANG Lina, LU Qi
Review of 60 years combating desertification in China and prospects on it
[
Background
] Desertification is one of the major threats to people around the world. It also affects the security of ecosystem and the sustainable development of economic society. China is one of the victim countries suffering from various types of desertification. Therefore, China has started combating desertification earlier and a number of successful achievements have been earned. These successful policies and examples of combating desertification may be applied by the similar countries and regions or translated into combating desertification models.[
Methods
] We reviewed and analyzed the works of combating desertification from past 60 years in China and cleared the development process of combating desertification in China.[
Results
] 1) The serious researches on desert science and practices of combating desert was initiated while the People's Republic of China was built. The period of 1949-middle of 1970s was beginning stage, desertification in China worsened due to massive cultivated crops though some combating works of investigation and monitoring were done. The years of 1978-1993 were preliminary development stage with the initiation of "Three North Shelterbelt" and establishment of several basic laws. Since 1994 until now, the desertification combating was in stable developing stage with joining in international conventions and built-up of national regulations. 2) First we have been conducting the fundamental researches on desert science such as desert ecology, wind-sand geomorphology, wind-sand physics, understanding basic situations of deserts in China, and building desert classification system, etc. Then we constructed institutional organizations such as field monitoring stations and key laboratories. Moreover, we built varied models and technical systems of combating desertification such as Hotan desertification control model in extreme arid areas, the Kubuqi desert ecological wealth creation model to get people out of poverty via the development of sand industry, rapid breeding technique system for sand-fixing plants, remote sensing monitoring technology for desert and desertified land, etc. 3) We earned experiences from 60 years desertification combating to share with international community, i.e., desertification prevention and controls should be directed by government and according to laws, and served for diplomatic cooperation with the countries, and promoted by international cooperation. 4) China's desertification combating has been developed so well that profoundly affects international rules, and currently leads the global desertification prevention and control in the world.[
Conclusions
] China's experiences on combating desertification are conducive to other desertification regions all around the world. We in this global village may win in this desertification combat by relying on more appropriate laws, allowing government to direct it, being based on scientific knowledge, using successful Chinese models, building advanced evaluation system, and enhancing international cooperation.
2018 Vol. 16 (2): 144-150 [
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554
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