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2017 Vol.15 No.6
Published 2017-12-31
1
XIAO Junbo, SUN Baoyang, MA Jianye, LIU Chenguang, SUN Yan, WANG Min, LI Zhanbin
Effect of seasonal freeze-thaw on the detachment capacity of aeolian sandy soil in Dongliugou watershed
[Background]
Soil detachment is the initial phase of soil erosion, and is of great significance to studies in regions that are characterized by seasonal freeze-thaw regimes. However, this process remains unclear because limited research on soil physical properties and soil detachment capacity has been carried out to date under freeze-thaw conditions. Thus, the aims of this study were to determine and compare the effects of slope gradient, flow discharge, moisture content, soil depth and freeze-thaw cycles on soil detachment capacity.
[Methods]
The soil samples were collected from the 0-20 cm soil layer in an abandoned cropland. It is located in Dalad Banner, Inner Mongolia which is the crisscross region of Hobq Desert and the Loess Plateau. In this study, in order to elucidate the effects of freeze-thaw on aeolian sandy soil detachment capacity, a series of artificial freeze-thaw simulations in combination with flume experiments were conducted by using the orthogonal method.
[Results]
1) Slope, flow discharge, moisture, freeze-thaw cycles and soil depth had significant influence on soil detachment capacity (
P
<0.05). The sensitivity degree of each factor on aeolian sandy soil detachment capacity was:slope > flow > freeze-thaw cycles > soil moisture content > soil depth, and slope and flow discharge were main affecting factors. 2) The aeolian sandy soil detachment capacity was linearly correlated with flow discharge and slope (
R
2
> 0.94). The critical value of flow discharge and slope affecting aeolian sandy soil detachment capacity was 0.07 L/min and 6%, respectively. 3) Soil moisture, freeze-thaw cycles and soil thawing depth influenced aeolian sandy soil detachment capacity indirectly by changing soil physical properties. The process, range and degree of freeze-thaw were restricted by soil moisture content and occurrence condition. If soil moisture content was too higher or lower, it would lead to the increase of aeolian sandy soil detachment capacity. When the soil moisture was 6%, the aeolian sandy soil detachment capacity reached the minimum value. Freeze-thaw cycles resulted in the redistribution of soil moisture. The effect of soil depth on soil detachment capacity was basically consistent with soil moisture content, and aeolian sandy soil detachment capacity of middle depth was the smallest. The aeolian sandy soil detachment capacity increased obviously with the number of freeze-thaw cycles increased, but gradually tended to flat trend after 10th cycles.
[Conculsions]
The above results indicated that seasonal freeze-thaw increased aeolian sandy soil detachment capacity and it will lead to the increase of soil erosion in spring of the seasonal freeze-thaw area. This research results may provide reference for the study of erosion mechanism of seasonal freeze-thaw areas. The effect of freeze-thaw on the soil detachment capacity, however, requires further investigation in regions where this process occurs seasonally.
2017 Vol. 15 (6): 1-8 [
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453
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9
WANG Daozheng, CHEN Xiaoqing, ZHAO Wanyu, ZUO Linyong
Movement and intercept characteristics of driftwood in debris flow
[Background]
Debris flow with woody could often have great impact destructive force, and threaten the safety of debris dams for woody debris may clog densely in the spillway. Judging from the results of past experiments related to driftwood in debris, we found that driftwood size, driftwood specific gravity, water depth, channel drop, and driftwood volume had a direct impact on the driftwood transport.
[Methods]
The model test tank device was selected as the rectangular section. A total of 75 kinds of test conditions under three kinds of debris flow bulk density, five kinds of driftwood number, and five kinds of
L/B
combination were designed. The experiment was conducted through 5 steps of 1) the model preparation 2) material configuration 3) test 4) change the debris flow bulk density, the number of driftwood (
N
) and the length of the driftwood, and repeat above 3 steps and 5) record the number of blocked driftwood.
[Results]
1)Driftwood tends to be parallel to the upstream debris flow direction due to the uneven forces acting on both sides of it, and transport to the downstream with a stable angle, this phenomenon is more obvious with the debris flow density becoming smaller. 2)The relative size of the driftwood has a certain effect on the intercept rate of the driftwood, and the effect on the intercept rate of the driftwood is small when relative length of driftwood
L/B
≤ 0.75 and driftwood intercept type is dead zone type. The intercept rate increases when 0.75<
L/B
≤ 1, but the intercept rate decreases due to the occurrence of blocking phenomenon when
L/B
=1, and then the intercept rate is gradually increasing because the blocking rate of driftwood is weakening. At this time, the intercept type is mainly key driftwood, and the theoretical analyses are consistent with experimental flume results. 3)The number of driftwood also has a great impact on the intercept rate, in general, the driftwood intercept rate increases with the number of driftwood increase. Driftwood intercept rate is very small and the size of the driftwood has little impact on the intercept rate when
N
≤ 120. With the increase of the number of driftwood, the probability of multiple driftwood reaching the channel shrinkage increases at the same time, and the intercept rate of driftwood increases when
N
>120.
[Conclusions]
The bulk density of debris, the number of driftwood and the relative size of the driftwood cause the great impact on the intercept rate. The results show that studying pattern of the movement and intercept rate of driftwood in debris flow is of great significance for understanding the characteristics of driftwood disaster and engineering control.
2017 Vol. 15 (6): 9-18 [
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19
LIU Dingzhu, CUI Peng, JIANG Dewang
Experimental study on breach broadening process of landslide dam
[Background]
Dynamic process of water and breach determines breach's profile during dam overtopping process. Dynamic processes in different sections along a breach are influenced by different flow regime. At present, research on breach broadening process is mainly focusing on a certain section and assumed this section could represent the broadening process of a dam. Knowledge of breach broadening in every section is short and the whole broadening process of a breach is a scientific question.
[Methods]
In order to study the whole breach broadening process in different initial conditions (height and slope), six flume experiments were designed to research. The observed data of 45 sections aimed at understanding erosion process in different sections and the influences of these initial conditions. We measured this process by using measure tools in mm accuracy and it was recorded by setting HD camera upon breach initially. Apart from this, the mechanical parameters such as the rate of water content and the density of dam were rigorously controlled for guaranteeing the same mechanical set.
[Results]
1) With the development of overflow, this process could be classified into two stages according to breach's profile. The process before the end of retrogressive erosion stage was named as the Aequilate Stage, and the process after retrogressive stage was named as the Bending Stage. In the first stage, the mechanism of water and sediment is simple but in the second stage the mechanism of water and sediment is complicated. 2) Broadening process could be divided into two modes, one is Linear Mode and another is Mutation Mode, accounting for 13.3% and 86.7% of 45 sections respectively. The Mutation Mode can be further divided into Weak Erosion ProcessⅠand Strong Erosion Process Ⅱ, in which the processⅡoccurs only in the Bending Stage. 3) The scour rate in the upstream and downstream is larger than that in the middle. The distribution of scour rate is like "U". In the first process, dam in larger initial slope causes larger scour rate in the same section. With the development of overflow, the complex flow regime has obvious secondary flow characters leading to the scour rate along the breach like "S" during processⅡ. For both processes, higher dam height leads to greater erosion rate.
[Conclusions]
Broadening ratio is different in different section and initial conditions influence the broadening ratio along the breach, which is a complicated process. This study didn't propose formulas to calculate erosion ratio along the breach, because 6 experiments couldn't reflect the physic of broadening process. Apart from this, the new understanding of broadening process of landslide dam is beneficial to the further study of mechanism of this process.
2017 Vol. 15 (6): 19-26 [
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27
WEI Xi, BI Huaxing, LIANG Wenjun
Canopy interception simulation of
Larix principis-rupprechtii
and
Pinus tabulaeformis
forests in northern China based on Gash model
[Background]
The interception process of forest canopy is a key of forest hydrology, which directly affects the prediction of hydrological cycle and forest soil and water conservation function. There are many influencing factors which are researched by scholars, and then, how to find a quick and accurate method has become a hot topic recently. One of these methods used widely is Gash model, and this paper verifies the applicability of Gash analytical model in
Larix principis-rupprechtii
and
Pinus tabulaeformis
forests in northern China.
[Methods]
Rainfall outside of stands, throughfall and stemflow of 3
L. principis-rupprechtii
forest plots and 3
P. tabulaeformis
forests plots in Mulan Forestry Management Bureau in Weichang County of Hebei Province during trees growing season of 2015 were measured and canopy interception was simulated combined with environmental and meteorological data. The core of the research methodology was to determine the accuracy of the Gash model parameters, including air temperature, temperature of soil depth, relative humidity, saturation vapor pressure, vapor pressure, open wind speed, air pressure, forest area net radiation flux, soil heat flux, psychometric constant and slope of the saturated vapor pressure curve at the temperature of air. In the process of simulation,regression method was used to determine canopy parameters and difference between intercepts of curves, which showed the relationship between stemflow and rainfall outside of stands and water storage capacity of leaves and branches was used as water storage capacity of tree trunks.
[Results]
Canopy water storage capacity of planted
L. principis-rupprechtii
forests was (1.72±0.48)mm for leaves and branches and (1.16±0.89)mm for tree trunks. Canopy water storage capacity of planted
P. tabulaeformis
forest was (2.60±0.23)mm for leaves and branches and (1.46±0.65) mm for tree trunks. The amounts of rainfall needed to saturate the canopy of
L. principis-rupprechtii
forests and
P. tabulaeformis
forest were (2.50±0.53)mm and (2.98±0.63)mm respectively. The scope of evaporation rate of plots was from (1.14×10
-1
to 1.42×10
-1
)mm/h in rainfall periods. The total values of canopy were 26.9, 38.34 and 38.29 mm, respectively, and the simulated values were 27.95, 41.22, and 38.32 mm, the relative error range was 0.07% -7.51%. The simulated values of canopy total were 54.37, 55.62, and 33.03 mm, the simulated values were 51.37, 52.69, and 35.23 mm, and the relative error ranged in 5.26%-6.66%.
[Conclusions]
There were no significant difference of variances and means between simulated value and measured value (
P
>0.1) while the correlation of them was high (
R
=0.99,
P
<0.01), indicating the fine simulating effect of Gash analytic model. This study would improve the measurement accuracy of forest canopy interception, rainfall and stemflow of two main tree species, and provide more accurate numerical simulation and theoretical basis for hydrological cycle and soil and water conservation in this area.
2017 Vol. 15 (6): 27-33 [
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34
WANG Xinchuang, LU Fenglian, WU Jinru, WANG Shidong
Ecological response to change in land use at the county level: A case study of landscape patterns in Xinzheng City, Henan Province
[Background]
Rapid economic development and population growth in China have led to both environmental deterioration and ecological disturbance in different regions. By studying the effects of change in landscape patterns on Ecological Services Value (ESV), we can gain a better understanding of the changes in regional environments and ecologies. This understanding can lead to the creation of a healthier environment and more harmonious ecosystems.
[Methods]
We examined remotely sensed satellite images of Xinzheng City that were obtained in 2005, 2010, and 2015. Changes in land use were quantified in order to create landscape patterns for Xinzheng City over ten years. Then we analyzed the changes in landscape patterns using values of typical landscape pattern indexes. A method developed from Costanza's calculation was used to estimate ESV. We also analyzed the effects of landscape pattern change on ESV.
[Results]
Farm land and build-up land were the two main landscape types in Xinzheng City. The total area of farm land decreased, but the total area of build-up land increased significantly over ten years. The landscape types were mainly changed from farm land, forest land and grassland to the build-up land and waters. The patch density, the maximum patch index and the spatial pattern of different landscape types changed in varied degrees, while the landscape diversity index increased as the dominance index and the extent of fragmentation decreased.. The ESV of Xinzheng City declined slowly at first and then declined sharply. The total decrease in ESV of Xinzheng City was 34.94×10
6
RMB Yuan over ten years, of which the ESV of farm land decreased by a maximum of 34.06×10
6
RMB Yuan. The ESV of build-up land showed the most significant change, an increase of 59.17%. In terms of spatial distribution, the ESV of Xinzheng downtown was low, while in the southwestern and northwestern areas the ESV was high. During the 10 years from 2005 to 2015, the areas with low ESV grew, and thus the spatial distribution of ESV became more uneven.
[Conculsions]
This study shows that the reduction of farm land and forest land and the increase in build-up land are the main reasons for ecological deterioration and the related decrease in total ESV. We provide a scientific assessment of the ecological benefits of soil and water conservation projects and a scientific baseline for the overall planning of future land use in Xinzheng City.
2017 Vol. 15 (6): 34-43 [
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44
WANG Wenjuan, DENG Rongxin, HAO Lijun
Relationship between farmland shelterbelt and gully erosion in the black soil region of Northeast China
[Background]
The black soil region in Northeast China is one of the most important marketable grain basis. The serious soil erosion brings crucial challenges to the production of marketable grain. Farmland shelterbelt is a key part of the Three Norths Forest Protection System in Northeast China, which plays a positive role in the prevention and control of soil erosion. The study on the effect of shelterbelt on gully can provide scientific insights into gully erosion control.
[Methods]
Firstly, the typical black soil region was chosen as the study area in Keshan County, Northeast China, and the distribution of gully and farmland shelterbelt was derived by interpreting the SPOT5 imagery in 2007 and TM imagery in 2008, respectively. Then, the effect of farmland shelterbelt on gully erosion was analyzed, using the spatial analysis and mathematical statistics methods.
[Results]
Generally, the density of farmland shelterbelts increased from northeast to southwest, while the variation law was the opposite for the density of gully. The highest density of farmland shelterbelt occurred in the western and northwestern regions, with the density larger than 1 400 m/km
2
. And the highest density occurred in northeastern region for gully, >800 m/km
2
. Furthermore, the defense effect of farmland shelterbelt on gully erosion varied with the defense distance. When the distance was shorter than 120 m, no obvious difference existed for the defense effect. When the distance ranged from 120 to 240 m, the defense effect decreased linearly with the increase of distance. When the distance was longer than 240 m, the defense effect decreased distinctly. Besides, the shelterbelt and gully density showed a highly linear relationship when the shelterbelt density ranged from 500 to 1 300 m/km
2
. However, the change of gully density was not obvious when the shelterbelt density was higher than 1 300 m/km
2
.
[Conclusions]
The slope, distance from the gully, and density of farmland shelterbelt were all import factors to the effect of farmland shelterbelt on gully erosion. The effect varied under different conditions of the three above mentioned factors. The farmland shelterbelt should be better planted in regions with the slope less than 8°, less than 120 m far away from the gully, and with the density ranging 1 100-1 300 m/km
2
in black soil region of Northeast China. This work may provide a certain scientific suggestion for the erosion prevention and management.
2017 Vol. 15 (6): 44-51 [
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52
WEI Hui, ZHAO Wenwu
The optimal estimation method for
K
value of soil erodibility: A case study in Ansai Watershed
[Background]
Soil erosion has become a global ecological and environmental problem. It is now being recognized as a severe threat to socio-ecological security and stability, and it is relative with the food security, resilience to climate change and geosocial stability. Soil erosion is particularly acute in the Loess Plateau. In order to control soil erosion, the quantitative study of soil erosion must be strengthened. Soil erosion is affected by many factors such as climate, vegetation, and land use and soil properties. Among those factors, soil erodibility has been qualitatively evaluated as a key indicator for estimating soil loss and usually being measured by
K
value. The research of soil erodibility is significant to understand the principle of soil erosion, to estimate soil erosion modulus quantitatively and to control soil and water loss reasonable. The estimation method of soil erodibility is numerous, but the regional applicability of different models remains to be discussed.
[Methods]
We conducted a study to select the optimal estimation method of soil erodibility (
K
value) based on the basic data of precipitation, soil, remote sensing images and socioeconomic data in Ansai Watershed. We used GIS technology and CSLE model to calculate soil erosion modulus in 2006-2014 and compared it with the corresponding monitoring value of sediment. Tthe
K
value was calculated by EPIC, NOMO, M-NOMO, Torri and Shirazi model. The comparison between the simulated value of soil erosion modulus and the monitoring value of sediments is based on the principle that the mean absolute error (MAE), the mean relative error (MRE) and the root-mean-square error (RMSE) are closer to 0, the accuracy factor (
A
f
) is closer to 1, the regional applicability of model is higher.
[Results]
The mean soil erosion modulus of Ansai watershed in 2006-2014 based on the five models of EPIC, NOMO, MNOMO, Torri, and Shirazi was 65.59, 106.00, 108.47, 76.69 and 47.68 t/hm
2
respectively. The mean monitoring value of sediment in corresponding year was 17.73 t/hm
2
. Based on the above evaluation indexes, we knew that the Shirazi model's regional applicability was the highest, the value of MAE, MRE and RMSE was 30.93, 3.25 and 43.66 respectively, the
A
f
value was 4.41, The regional applicability of EPIC model took second place, the value of
A
f
was 5.80, The regional applicability of Torri model was in the middle level. The regional applicability of NOMO model and M-NOMO model was lowest, it had the biggest difference with the actual situation, the
A
f
value was 7.99 and 7.88 respectively.
[Conculsions]
Based on the above analysis, we concluded that the Shirazi model had the best applicability in study area comparing to the other four
K
value estimation methods. We should be preferred to choose the Shirazi model in the future watershed scale soil erodibility (
K
value) estimation and soil erosion evaluation.
2017 Vol. 15 (6): 52-65 [
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599
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66
WANG Kunxiang, WANG Keqin
Effects of sloping land on the runoff and sediment on catchment area in Songhuaba Reservoir in Kunming.
[Background]
China is one of countries having the most serious soil erosion disaster in the world, it is across the country and it is serious. It is the concentrated reflection of various kinds of ecological problems, and results in the serious threat to food and ecological security. The study of soil and water loss mainly focuses on runoff plots, and the research on catchment area is little.
[Methods]
Two kinds of catchment area were selected at Yizhe small watershed in Songhuaba Reservoir in Kunming. The area of the mixed catchment area (L+P) was 0.42 km
2
, it included woodland catchment area (L) and sloping land. Runoff and sediment yield characteristics were monitored continuously under the natural rainfall condition. According to the long-term and effective monitoring data of rainfall, runoff and sediment yield, the dynamic change process of runoff and sediment yield would be quantitatively and qualitatively described.
[Results]
1) Runoff of mixed catchment area was higher under the strong rainfall condition, it was 9.31 times that of the woodland catchment area. Runoff coefficient and flow coefficient of variation were same as the runoff of mixed catchment area, they were 1.14 and 1.43 times that of the woodland catchment area respectively. 2) The sediment yield showed significant differences between the woodland catchment area and the mixed catchment area, they were 69.76 t/km
2
and 359.10 t/km
2
respectively. The sediment discharge coefficient of variation in the mixed catchment area was greater than that in the woodland catchment area, because the sediment control ability from woodland catchment area was much better than mixed catchment area, thus sediment losses was smaller. 3) The single factor variance was 0.01 and 0.001 of runoff and sediment yield on catchment area, and the significance of sediment yield was greater than the production flow.
[Conclusions]
Sloping land had the direct effect on water and soil loss in the catchment area. Research of catchment area was more conform to changes under natural conditions; it could avoid deviation from the limits of plot runoff because of area. It could be effectively reckoned up the influence of land-use types on water and soil loss by the runoff and sediment. And it can serve as an important basis for soil erosion control measures.
2017 Vol. 15 (6): 66-72 [
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462
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1674KB] (
419
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73
WANG Qian, LIU Linqi, WANG Peishu, CAO Jing, CHEN Jingling, ZHANG Jingshong, KOU Yuanbo
Series lines of climate space up limit of
Quercus variabilis
seedlings in static wind and different soil water stress
[Background]
The Series Lines of Climate Space Up Limit (SLCSUL) of
Quercus variabilis
seedlings are important characteristics which may reflect more accurate temperature index of heat stress of high temperature. We had determined the serial lines of climate space of
Q. variabilis
seedlings in conditions of fully water supplied and different wind speeds. In this study we explored the leaf temperature of
Q. variabilis
seedlings changing with solar radiation, air temperature in condition of different soil moistures.
[Methods]
In the sunny weather conditions, controlling microclimate factor of wind speed under 0.2 m/s, and controlling different soil moisture conditions, the leaf and air temperature difference (LATD) of
Q. variabilis
seedlings were measured and the relation between LATD and the solar radiation were analyzed. Because leaf temperature index plus LATDs are leaf temperatures corresponding to different LATDs, the linear relation of LATD and the solar radiation was transformed into relation of leaf temperature and the solar radiation. According to the linear relation of leaf temperature and the solar radiation, leaf temperature increases with solar radiation increasing. This means solar radiation contracts climate space of
Q. variabilis
seedlings. Consulting D. M. Gates' climate space graphical method, overturn the regression line of leaf temperature and solar radiation, the SLCSUL of
Q. variabilis
seedlings were drawn.
[Results]
1) The solar radiation was main factor of LATD, and LATD increased with solar radiation in clear and no wind weather. The relationship of LATD and solar radiation was remarkably linear relation. 2) The slope of linear relation of LATD and solar radiation decreased with soil moisture increasing. 3) In noon time, and in serious soil drought condition (soil moisture was 5%), the leaf temperature of
Q. variabilis
seedlings was 3℃ higher than in appropriate soil moisture condition.
[Conculsions]
We concluded that in different soil moisture conditions the leaf temperature of
Q. variabilis
seedlings increased with solar radiation increasing and the slope of LATD of different solar radiation decreased with soil moisture increasing. The LATD of different soil moisture changing with solar radiation was quite similar to the results of our former studies in different wind speed conditions, and it had the similar SLCSUL. Combining results of this paper with SLCSUL of different wind speed, the characteristics of climate space of
Q. variabilis
seedlings of 4 factors such as solar radiation, air temperature, soil moisture, and wind speed will be obtained. Therefore, the results of this paper may provide the basis for determining precise leaf temperature index of heat stress with multiple agro-meteorological factors. This paper enriches plant climate space theory and provides guidance for heat stress leaf temperature index determination of other plants, including crops, when multiple agro-meteorological factors are needed to be analyzed.
2017 Vol. 15 (6): 73-80 [
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81
WANG Bing, LIU Zuying, ZHAO Yusen, NIU Xiang
Ecoregion division of natural forest at the key state-owned forest region in Northeast China
[Background]
The key state-owned forest region in Northeast China is one of "Two Screen and Three Zones" as the subject, to ensure the ecological safety of the Northeast China. For comprehensively, systematically, scientifically, and quantitatively evaluating the ecological benefits of the region's Natural Forest Protection, dividing the ecoregions is indispensable.
[Method]
First, we chosen the map of the Natural Forest Protection, eco-geological system of China, Chinese vegetation regionalization, China's soil erosion region and China's administrative division as the data sources. Then, we selected hydrothermal conditions, vegetation types, soil erosion types and intensities as three levels of regionalization indicators. Finally, we applied the geographic information system(GIS) space analysis to obtain the ecoregions.
[Results]
Based on the climate there are 3 Class I areas of cool moist, mid-temperate moist, and mid-temperate semi-moist. Based on the Class I and vegetation type, there are 4 Class Ⅱ areas:cool moist coniferous forest, mid-temperate moist mixed broadleaf-conifer forest, mid-temperate moist rangeland, and mid-temperate semi-moist rangeland. Based on the Class Ⅱ and soil erosion type and intensity, there are 12 Class Ⅲ areas:Ⅰ-A-a-1 cool moist deciduous conifers non-erosive area, Ⅰ-A-a-2 cool moist deciduous coniferous slight wind erosive area, Ⅰ-A-a-6 cool moist deciduous coniferous high water erosive area, Ⅱ-A-b-1 mid-temperate moist mixed broadleaf-conifer forest non-erosive area, Ⅱ-A-b-3 mid-temperate moist mixed broadleaf-conifer forest slight water erosive area, Ⅱ-A-b-4 mid-temperate moist mixed broadleaf-conifer forest mild water erosive area, Ⅱ-A-b-5 mid-temperate moist mixed broadleaf-conifer forest moderate water erosive area, Ⅱ-A-b-6 mid-temperate moist mixed broadleaf-conifer forest high water erosive area, Ⅱ-A-c-6 mid-temperate moist rangeland high water erosive area, Ⅱ-B-c-1 mid-temperate semi-moist rangeland non-erosive area, Ⅱ-B-c-2 mid-temperate semi-moist rangeland slight wind erosive area, and Ⅱ-B-c-3 mid-temperate semi-moist rangeland slight water erosive area
[Conclusions]
Based on multiple indicators, the key state-owned forest region Natural Forest Protection in Northeast China is characterized, ecoregions intuitively reflects the actual geographical regional rules. Meanwhile, we may use regionalization characteristics to verify the results of ecological benefit assessment, thus this work lays the foundation for ecological benefits monitoring and evaluation of the region's Natural Forest Protection.
2017 Vol. 15 (6): 81-88 [
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522
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89
LIAN Zhuanhong, YANG Haili, WU Fangming, HUANG Haixia
Effect of NaCl or PEG stress on seed germination of
Gymnocarpos przewalskii
[Background]
Gymnocarpos przewalskii
is the rare relic of tertiary and endangered species of desert area in central Asia, and one of the oldest groups in saline environment. It is mainly distributed in the desert area in our country being one of the main constructive species in stony desert area where rainfall is small but evaporation is strong, which results in the salt accumulation in soil, subsequently drought and soil salt affect its seed germination and further its population establishment and regeneration. To protect
G. przewalskii
, salt and drought stress was respectively stimulated to research salt and drought resistance mechanism in seed germination.
[Methods]
Seeds of
G. przewalskii
were collected from botanic garden of Anxi Extra-arid Desert National Nature Reserve with the mean annual rainfall of 45.3 mm and the salt content more than 2% in the soil depth of 30 cm. Using the different concentration of NaCl (50,100, 150, 200, 250, and 300 mmol/L) and the different potential of PEG-6000(-0.1, -0.3, -0.5, -0.7, and -0.9 MPa) to stimulate salt stress and drought stress respectively, taking the distilled water as the control to measure the germinated seeds and time, germination rate, germination energy, germination index vigor index and average germination days were calculated and the germination characteristics and the response to salt stress and drought stress were analyzed.
[Results]
The results showed that the germination rate and the vigor index increased at low concentration of NaCl (50 mmol/L) compared with the control. The germination rate, germination energy and average germination days were not significantly affected at the concentration of 100 and 150 mmol/L NaCl, and the germination rate, germination energy and vigor index decreased insignificantly at the osmotic potential of -0.3 MPa, which indicated that germination ability and uniformity was not significantly affected by relatively low concentration of NaCl (100 and 150 mmol/L) or relatively high osmotic potential of PEG (≥ -0.3 MPa). At high concentration of NaCl (≥ 250 mmol/L) or low osmotic potential of PEG (≤ -0.7 MPa), the germination rate, germination energy, germination index and vigor index extremely significantly decreased and the germination process was markedly prolonged, the seed germination of
G. przewalskii
was significantly inhibited and delayed due to the intensified osmosis and toxic action. Regression analysis indicated that the critical and limited value of NaCl stress on seed germination was 337.4 mmol/L and 628.6 mmol/L, respectively and the critical and limited value of PEG stress on seed germination was -0.70 MPa and -1.01 MPa, respectively.
[Conculsions]
The seed germination of
G. przewalskii
was improved at the concentration of 50 mmol/L NaCl and showed some tolerance to salt and drought stress, beyond the range (more than NaCl concentration of 250 mmol/L or less than PEG osmotic potential of -0.7 MPa), its seed germination was significantly inhibited. Researching the seed germination characteristics of
G. przewalskii
can provide some basis for the cultivation of
G. przewalskii
and combating desertification in desert area.
2017 Vol. 15 (6): 89-96 [
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374
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444
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97
MA Tao, JIA Zhiqing, YU Yang, ZHANG Feng, DONG Yanli, TIAN Jinhua, CHEN Aihua
Effects of soil environment on soil carbon flux of
Robinia pseudoacacia
forest at different stand ages in Longdong Loess Plateau
[Background]
Soil environment is one of the key elements affecting soil carbon flux on artificial plantations. This study investigated the mechanisms between soil environmental factors and soil carbon flux thus distinguishing the main driving factors for soil carbon flux, which remained poorly understood to date.
[Methods]
This study was carried out to understand the soil carbon flux of
Robinia pseudoacacia
for different restoration periods (12, 14, 15, and 18 years) in the Longdong Loess Plateau. Soil carbon flux of different stand ages were monitored by Li-8100 system and the grassland was used as control. Meanwhile, the soil environmental factors such as soil organic matter, soil moisture soil temperature at 5 cm and surface temperature were detected simultaneously. The experimental data were analyzed and plotted by Excel2007. The correlation analysis was carried out by SPSS21.0, and the fitting degree between soil carbon flux and temperature, soil water content and single factor and two factors was tested.
[Results]
1) The surface temperature and soil temperature were significantly correlated with soil carbon flux (
P
<0.01), the degree of fitting was 64.64%-96.27%. Compared with surface temperature, soil carbon flux was more sensitive to soil temperature, and the values of
Q
10
varied from 2.21 to 4.36. The highest value was detected in 15 and 18 years, whereas the grassland exhibited the lowest. 2) There was a significant linear correlation between soil carbon flux and soil moisture (
P
<0.01), while the regression model can only explain the variation of soil carbon flux by 19.57%-36.70%. 3) Total nitrogen, available nitrogen, available phosphorus, available potassium and soil organic matter showed similar trend in different stand ages, all of these decreased with the increase of soil depth. In the top soil layer (0-10 cm), soil nutrients showed the highest value while the lowest values were at 60-100 cm soil layer. The level of soil nutrient contents affected the release rate of soil carbon flux. The soil nutrient contents of 14 and 15 years increased rapidly.
[Conculsions]
Soil temperature is the main driving factor for determining soil carbon flux. Our results may provide data for exploring the mechanism of soil carbon flux in the Longdong Loess Plateau.
2017 Vol. 15 (6): 97-105 [
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555
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452
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106
CHENG Dongbing, ZHAO Yuanling, ZHANG Pingcang, ZHAO Jian
On the risk assessment of collapse gully erosion in Jiangxi Province based on Logistic model
[Background]
Collapse gully erosion is a special type of soil erosion in southern China, but risk assessment research on collapse gully erosion is few. Risk assessment provides new ideas and methods for the study of collapse gully erosion and soil erosion.
[Methods]
This article selected Jiangxi Province as the study area. The index of the risk assessment was selected by the correlation factor analysis, and the Logistic model was used to calculate the occurrence risk of collapse gully erosion. On this basis, the hazardous risk of collapsing was estimated by the expert scoring method. In the end, the risk of collapse gully erosion can be obtained by superposing the occurrence risk and hazardous risk, so as to discuss the feasibility of risk assessment of collapse gully erosion at the regional scale.
[Results]
Collapse gully erosion in Jiangxi Province are mainly distributed in such as precipitation from 1 500 mm to 1 700 mm, granite red soil land, sloping from 10 degrees to 30 degrees, below 300 m altitude, vegetation coverage less than 0.2 or from 0.6 to 0.8, in forest or grassland area. By using the function of geographic analysis in ARCGIS, after overlay factors and the distribution of collapse gully erosion, 4 000 grid cells are sampled randomly and respectively in study area with collapse gully erosion or not, and logistic regression model is constructed with date of collapse gully erosion distribution and 6 screened factors such as hypsography, relief, vegetation cover, soil type, land use, and rock type. For accuracy tests amount to 70.9%, then the occurrence risk of collapse gully erosion in Jiangxi Province can be calculated by this logistic regression model. The occurrence risk of collapse gully erosion in the south and the west of Jiangxi Province is relatively higher, and those in the eastern, northern and central are relatively lower. The hazardous risk of collapse gully erosion is generally minor in the whole province, and the hazardous areas with relatively high risk showing a sporadic distribution trend. After comprehensive analysis of the occurrence risk and the hazardous risk, the collapse gully erosion presents medium and low risk in Jiangxi Province, which possesses more than 95 percent of the province's total area. Among them, the light risks accounts for 68% of the total area of the province and is mainly distributed in the surrounding areas of Poyang Lake. The measures of risk prevention and control should be mainly focused on prevention and protection in these areas. The medium-and upper-class risks is mainly distributed in the southern and western parts of Jiangxi Province, and in these parts, risk prevention and control measures should be taken equal attention to prevention, protection and comprehensive management.
[Conclusions]
Finally, the study proves that Logistic model is feasible for estimating the risk of collapse gully erosion.
2017 Vol. 15 (6): 106-116 [
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570
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117
LI Hujun, WANG Quanjiu, TAO Wanghai, CHAI Jing, ZHAO Guangxu
Effects of different amendments on the yield of surface runoff and loss of nutrients along loess slope soybean farmland
[Background]
Soil erosion caused by rainfall contributes significantly to land degradation and nonpoint source pollution in the Loess Plateau. The application of soil amendment agent may improve soil structure and promote crop growth, which is of significance to reduce soil erosion and improve soil fertility.
[Methods]
In order to clarify the influence of three different amendments (Polyacrylamide (PAM), sodium carboxymethyl cellulose (CMC), and humic acid (HA)) on characteristics of surface runoff, sediment transport and nutrients losses on soil water and the distribution of nutrients in soil profile of soybean(
Glycine max
L.) fields during the heavy rainstorm (rainfall intensity was 100 mm/h), a stimulated rainfall experiment was performed at Changwu State Key Agro-Experimental Station on the Loess Plateau.
[Results]
Compared with CK (without soil amendment), the application of PAM and CMC amendments reduced soil infiltration capacity and increased surface runoff, and the total runoff amount increased by 20.8% and 12.1% respectively while HA had no significant influence on surface runoff. By comparison, three soil amendments had effects on reducing sediment yield. The sediment yield were reduced by PAM, CMC and HA, and the reduction rate were 34.8%, 22.5% and 7.9%, respectively. Hence, PAM worked best in reducing rainfall erosion. PAM and CMC had a better performance in inhibiting ammonium nitrogen losses than that of the HA and CK in the middle and late stage. There was no obvious effects of soil amendment on soluble phosphorus loss, but PAM treatment resulted in a highest loss of soluble phosphorus which was 1.13 times amount of CK. There was a highest ammonium nitrogen loss under CK condition, followed by PAM, CMC and HA. The content of ammonium nitrogen at the depth of 15 cm was the highest under PAM treatment condition, followed by CMC, CK and HA. And HA increased the leaching depth of ammonium nitrogen. In addition, soil available phosphorus was mainly concentrated in the inner 10 cm of surface soil layer.
[Conclusions]
Soil amendments like PAM, CMC and HA can play a certain role in the reduction of soil erosion and preventing nutrient over slope land on the Loess Plateau, but PAM may have no effect on soluble phosphorus loss. The results of this study may provide a scientific guidance for the rational selection and application of the local soil conditioner.
2017 Vol. 15 (6): 117-125 [
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401
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396
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126
KANG Qing, JIANG Dewen, FU Qinghua, WANG Xiaogang
On the identification of construction disturbance patches based on optimal segmentation scale
[Background]
Identifying construction disturbance patches is significant to soil and water conservation. With high spatial-resolution imagery prevalent, object-based image analysis (OBIA) is proposed because it can offer substantial information to overcome the infamous "salt-and-pepper" speckle and phenomenon of "different objects with same spectrums" or "different spectrums with same objects" associating with pixel-based classification. Image segmentation and classification are two main steps in OBIA, wherein the former is foundation. Yet there has challenges of estimating appropriate scale parameters, known as optimal scale parameters (OSP), for an interest land cover. Although dozens of algorithms have been proposed, none of them were used in construction project recognition.
[Methods]
Two widespread algorithms of OSP were analyzed and evaluated. One is the local variance (LV) method with the conception that the rate of change of LV (
Roc
_LV) can capture the variation of object heterogeneity within a scene. The other is an objective function method with taking into account both of object's internal homogeneity and external distinguishability. The calculated OSP from LV method and objective function method were validated by two items, i.e., artificial sketched OSP according to field survey, and the identifying accuracy of construction disturbance patches was conducted by an object-oriented supervised classification method.
[Results]
Image segmentation was implemented in eCognition software by the scale of 30 to 500 with an interval of 10. According to the UAV image and ground survey, 300 was manually judged as the OSP that unambiguously distinguished boundary between construction disturbance patches and other land use type. This artificially determined OSP was used as ‘real’ value to evaluate LV method and objective function method. The OSP calculated by LV method and objective function method were 310 and 300, which were slightly higher than and equal to the ‘real’ value, respectively. Then, construction disturbance patches of each segmented image from scales of 150 to 390 were identified by an object-oriented supervised classification method and interpretation keys, and their identifying accuracies were calculated by the identification according to the UAV image, statistic data and ground survey. The result indicated that scale of 300 (i.e., the OSP) had the highest accuracy with the producing accuracy and user accuracy of 86.3% and 84.2%, respectively, while other's producing accuracy was less than 85% and user accuracy was lower than 82%. This result illustrated the consistency between OSP and construction disturbance patches identifying accuracy.
[Conclusions]
Two conclusions are reached. 1) Compared to LV method, the objective function method is recommended to calculate the OSP of construction project in given study area and GF-1 image. 2) The identification process based on objective function method and object-oriented supervised classification method is proposed because by which the better accuracies than other segmental scales was obtained.
2017 Vol. 15 (6): 126-133 [
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445
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479
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134
WANG Chunhong, WANG Zhiguo, FAN Hua
Relationship and several planning issues between soil and water conservation and water ecological civilization
[Background]
Water and soil conservation and water ecological civilization construction are essential sections of national ecological civilization construction. Also, it is urgent to strengthen the ecological construction associated with water for satisfying the reform and development of the Ministry of Water Resources in the new era. In order to correctly understand and deal with the relationship between soil and water conservation and water ecological civilization in the new era, as well as giving full play to the role of soil and water conservation in the construction of water ecological civilization, the article was generated.
[Methods]
Firstly, the difference and relationship between water and soil conservation and water ecological civilization construction were analyzed by clarifying the concepts and connotation of them. On the basis of the clarification, the core contents of soil and water conservation in the construction of water ecological civilization were defined and picked out. Furthermore, the key techniques and key contents of thematic planning of soil and water conservation in ecological civilization planning were discussed by the same way, including the relationship, the entire allocation, main tasks and goals, key technical links, demand analysis, partition layout and measure system, key projects and their main contents.
[Results]
Through those analyses, we came to three results. First, soil and water conservation is a basic work of land remediation, with emphasis on combination and harmony of water and soil. While water ecological civilization is a more macroscopic and powerful guiding ideology. The acting point of the water and soil conservation is the protection and construction of the related terrestrial ecosystem for the construction of water ecological civilization, so as to provide a healthy land and vegetation condition. Second, there are two parts of the soil and water conservation closely related to the construction of water ecological civilization, which are the protection and rehabilitation of water ecological restoration within national spatial, and the ecological protection of the construction and operation of water conservancy projects. Thus the core contents of soil and water conservation in the construction of water ecological civilization are the maintenance and improvement, protection and restoration, of the function of soil and water conservation. Third,we put forward that the thematic planning of water and soil conservation should be emphasized on the creation of a healthy land and vegetation condition for the construction of water ecological civilization, which could accomplish the goals of maintenance and improvement of regional soil and water conservation, especially for water conservation, water quality maintenance, soil conservation, and sand blockage and reduction.
[Conculsions]
Clearing the position of the soil and water conservation in the construction of water ecological civilization is extremely important for the planning and operation of them both. Therefore, finding the linkage and starting with them could find a shortcut to maintaining and improving regional soil and water conservation function.
2017 Vol. 15 (6): 134-139 [
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463
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494
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140
ZHU Bisheng, CAO Wenhong
Study on mandatory standards of soil and water conservation
[Background]
There are masses of problems, for instance, out-of-scope contents, including "main contents and preparation depth of report", as well as flood protection & security, blasting construction, scaffolding, etc. covered in other standards, in existing mandatory standards in the field of soil and water conservation. In order to solve the issues such as the cross, duplication, contradictions and out-of-scope preparation among compulsory standards, the mandatory standards in the field of soil and water conservation field were studied and analyzed in accordance with the requirements of national mandatory standards must be integrated and briefed.
[Methods]
On the basis of comprehensively collecting and sorting the compulsory standards in the field of soil and water conservation, we classified and gathered 5 aspects of data, including security, of which covers facilities security, flood protection security, construction security and property security, soil erosion protection, environmental protection, acceptance of management and protection, design requirements; besides, we studied and analyzed item by item according to the factors such as necessity, purpose, core content, and applicable scope of a formulated standard by classification and summarizing.
[Results]
In all 186 Paragraphs of 71 Articles of the mandatory standards, the 74 Paragraphs from 19 Articles were proposed to be remained, 35 Paragraphs from 24 Articles that complied with mandatory standards but can be integrated into other standards were proposed to be integrated; 10 Paragraphs from 7 Articles that were fully covered by other mandatory standards or not applicable to be standardized in the form of standards were proposed to be abolished; 67 Paragraphs from 22 Articles that were not targeted to "Health, Security, Environment-friendly, Social Economy Management" were proposed to be transformed.
[Conclusions]
We proposed to integrate standards related to out-of-scope professional and industries; defined the scope in strict accordance with the national mandatory standards to avoid excessive mandatory scope; added verifiable, confirmable and detectable mandatory standards; put forward suggestions for the improvement on the mandatory standards in the field of soil and water conservation, for instance, comprehensive control of soil erosion; built the frameworks for perfecting mandatory standards in the field of soil and water conservation, so as to provide references for integrating, briefing, and perfecting of the compulsory standards above.
2017 Vol. 15 (6): 140-146 [
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361
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