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2017 Vol.15 No.4
Published 2017-08-31
1
DAI Jinmei, ZHA Xuan, HUANG Shaoyan, CHEN Shifa, LIU Chuan, WANG Liyuan, BAI Yonghui
Spatial and temporal variations of rainfall erosivity on West Fujian during 1980 to 2013
[Background]
Rainfall erosivity is for assessing the potential ability of rainfall on soil erosion. A regional soil erosion prevention and controlling work have a guiding significance. Water erosion is one of the important forms of soil erosion in Fujian province.
[Methods]
To study the space-time distribution of West Fujian rainfall erosivity pattern, based on the 1980-2013 daily rainfall data of nine weather stations in West Fujian region and using the Daily Rainfall Erosion Force Model to calculate the rainfall erosion force, then methods of linear regression, climate tendency rate, Mann-Kendall test methods and the spatial interpolation methods were applied to analyze the spatial and temporal variations of rainfall erosivity.
[Results]
1) The range of annual rainfall erosivity in the West Fujian was 6 160-14 310 MJ·mm/(hm
2
·h) with an average value of 9 504 MJ·mm/(hm
2
·h), the amplitude of 8 150 MJ·mm/(hm
2
·h), average rainfall erosivity was very significantly and positively correlated with the average rainfall. 2) There was a spatial distribution pattern of annual rainfall erosivity and it was greater in the western area and less in the eastern area of the studied area, rainfall erosivity of high value area was in the northwest and low value area was in the northeast. The spatial distribution of average annual rainfall erosivity was similar to that of average annual precipitation; nine counties of rainfall erosivity in ascending order, respectively:Ninghua > Dongxing > Guanyinqiao > Zhongshan > Yongding > Shanghang > Yangjiafang > Zhangping > Yong'an. 3) The rainfall erosivity concentrated in rainy season (March to August), which contributed 80.12% of the whole year. During the year the distribution curve of rainfall erosivity showed bimodal type, peak for June and August. Rainfall erosivity changed in a positive trend, including January, May, June, July, August, October, November, and December, which was the most obvious in June. Meanwhile, the declining trend of rainfall eruption included February, March, April, and September, which was the most obvious in March. 4) The rainfall erosivity showed upward trend in summer, but downward trend in other periods. The annual change of rainfall erosivity indicated that rainfall and rainfall erosivity showed downward trends. Rainfall to changes in the rate of decline in 7.3 mm in every 10 years, and the climate rate of rainfall erosivity was 72.7 MJ·mm/(hm
2
·h·10 a). 5) The abrupt change of rainfall erosivity occurred in 1995 and 2002, respectively, and rainfall erosivity had a slight upward trend since 1995, and from 2002 it had the obvious downward trend.
[Conclusions]
Soil erosion in the West Fujian is the key prevention area on soil and water erosion, and the government should increase attentions on it. The results of the study provide the basis for the regional soil erosion prediction, the regional risk assessment of soil erosion, and soil erosion management work.
2017 Vol. 15 (4): 1-7 [
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660
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8
MA Jianye, LI Zhanbin, MA Bo, WANG He, ZHANG Letao, LI Chaodong
Soil water characteristics under different vegetation recovery modes in hilly and gully region of the Loess Plateau:A case study of the Qiaozigou Watershed
[Background]
The hilly and gully region of the Loess Plateau, which is suffering from lacking in water resources, is the most serious soil erosion region in Loess Plateau. Generally, the soil moisture is an effective indicator to evaluate the influence of soil and water conservation measures. The objectives of this paper were to study the redistribution process of precipitation and the effect on the stability of soil reservoir under different modes of vegetation recovery.
[Methods]
Based on paired watersheds, the effect of precipitation and slope aspect on soil moisture were quantitatively analyzed under different modes of vegetation restoration. Paired watersheds included two typical small watersheds in the hilly and gully regions of Loess Plateau:Qiaozi West Watershed (waste-grassland of natural restoration) and the Qiaozi East Watershed (black locust forestland of artificial restoration). Samples were collected at 9 soil layers in the upstream, midstream and downstream of two paired watersheds. The 9 soil depths were 0-2, 2-4, 5-15, 15-25, 25-35, 35-45, 45-65, 65-85, and 85-100 cm, respectively. This project was carried out about 4 times throughout the period from May to August. Characteristics of soil mass water content and isotope concentration of hydrogen and oxygen (
δ
O
18
) within 0-100 cm soil layer were calculated.
[Results]
The results showed that there were significant differences in the redistribution of soil water under different vegetation restoration modes (
P
<0.05). Soil water content of watershed mainly comprising of black locust forestland (16.72%) is lower than that of the watershed mainly comprising of waste-grassland (20.42%). The variation coefficient of soil water content was relatively higher and the response of soil water content to precipitation was weaker in the former watershed. Critical depth for soil moisture was identified for the two watersheds. The water content was relatively stable (about 12.19%) under the soil depth about 10 cm in the black locust forestland. However, the water content increased with the soil depth when the soil depth blew 30 cm in the waste-grassland. The maximum evaporation depth of waste-grassland was 30 cm, which was shallower than that in the black locust forestland (about 55 cm). The soil mass water content in different slope aspects in Qiaozi West Watershed ranked in the follows:shady slope (19.60%), half negative slope (17.65%), half-sunny slope (14.24%), and the content were lower respectively about 6.68%, 4.98%, 1.03% in each slope aspect of Qiaozi East Watershed than the former watershed. Additionally, the concentration of
18
O in different slope aspects ranked in the follows:negative slope(-5.57‰), half-sunny slope (-5.64‰) and shady slope(-6.08‰) in Qiaozi West Watershed, while the concentration were -5.74‰, -6.21‰, -6.03‰ in Qiaozi East Watershed, respectively.
[Conclusions]
There were differences for soil moisture in the same slope aspect under different vegetation restoration modes in the hilly and gully region of the Loess Plateau. In natural restoration watershed, the influence of slope aspect on soil water content is greater than that of artificial restoration watershed. Compared with the artificial restoration mode, the natural restoration can greatly increase the capacity of soil water storage, which is beneficial to improve and sustain the watershed ecology.
2017 Vol. 15 (4): 8-15 [
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16
YANG Xiuqing, SHI Chan, WANG Xugang, MA Huijing, YAN Haibing
Spatial heterogeneity of soil in the secondary
Picea
forest of Guandi Mountain and its correlation with topography
[Background]
Soil properties to a large degree showed the spatial self-correlation variation characteristics. Topography is usually an important source of soil variation. Quantitative analysis of spatial heterogeneity of soil and its correlation with topography is helpful for revealing the potential mechanism of soil variation.
[Methods]
Referring to soil sampling scheme of CTFS, we collected 199 soil samples from a 4 hm
2
secondary
Picea
forest of Guandi Mountain and completed the soil properties determination. The horizontal and vertical space distribution characteristics of PH, organic matter, available nitrogen, phosphorus and potassium were analyzed using the classical statistical methods, spatial heterogeneity of soil properties at 0-10 cm layer and their distribution patterns were acquired through geo-statistics and ArcGIS interpolation, and the effects of terrain factors on spatial heterogeneity of soil properties were quantitatively assessed by RDA sorting and variance decomposition.
[Results]
The coefficient of variation for the soil pH, organic matter, available nitrogen, available phosphorus and available potassium was 8.78%、48.38%、41.15%、58.36%、46.60%, respectively. The five factors showed the spatial self-correlation variation at 4.9-58.8 m scale range, and a moderate degree of self-correlation was evaluated for pH and available nitrogen but a strong degree of self-correlation was evaluated for organic matter, available phosphorus and available potassium. Organic matter, available nitrogen and available potassium showed analogical spatial plaque distribution pattern, that is, the contents of organic matter and available potassium were also high in the plaque where there was available nitrogen in high content, while the soil pH and available phosphorus showed an opposite distribution pattern. Among the terrain factors, elevation had the strongest effects on the soil pH, available nitrogen and phosphorus, soil pH and available phosphorus had positive correlation with elevation, and the elevation explained 40.43% and 28.81% of the spatial variability of soil pH and available phosphorus, respectively, but available nitrogen had negative correlation with elevation and the elevation explained 19.48% of the spatial variability of available nitrogen independently. Convexity had the strongest negative effects on available potassium and organic matter, and it explained 9.37% and 6.88% of the spatial variability of available potassium and organic matter.
[Conclusions]
Soil properties showed structural heterogeneity in space and topography factors had important effects on the variation of soil factors. The experimental results can provide the basis for understanding the distribution and coexistence of tree species in North China.
2017 Vol. 15 (4): 16-24 [
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540
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2845KB] (
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25
HE Kaiwen, HUANG Yanhe, JIANG Fangshi, LIN Jinshi, CHENG Zijie, ZHANG Kai, XIE Weikun, HUANG Zhaoxiang
Effects of two types of herb plants' roots on soil moisture in the alluvial soil in Changting County
[Background]
Alluvial is an important part of collapsing gully, as a type of disturbed soil, alluvial feature high contents of gravel, sand, and loose materials, so that they are often weak in structure, low in cohesion and high in erodibility. Alluvial may bring hazards to ecological environment. Plant is the key to control soil and water loss. Planting vegetation on the alluvial can effectively reduce erosion and water conservation, increase stability of soil structure and soil water storage ability.
[Methods]
Two typical herbs
Pennisetum
sp.(deep-root system) and
Paspalum wettsteinii
(shallow-root system),which were planted in the alluvial soil, were chosen as the research object to analyze the effects of plants' root systems on the alluvial soil moisture. Soil samples were collected by layering sampling along the root, and soil physical properties including soil bulk density, porosity and maximum moisture capacity etc. were tested by cutting ring method, which were used to calculate the soil water storage capacity. In addition, the roots were separated from undisturbed soil samples, which were collected by big cutting ring (the inner diameter of 9.8 cm and 5.0 cm high). Root system parameters such as root length density, total surface area, total volume, average diameter, etc. were measured by WinRHIZO root analysis system.
[Results]
The indexes of root system characteristics of
Pennisetum
sp. and
P. wettsteinii
decreased with the increase of soil depth, all root indexes of
Pennisetum
sp. were greater than those of
P. wettsteinii
. Vegetation cover decreased the soil bulk densities compared to bare land, also the soil total porosity and capillary porosity of soil with vegetation covers were greater than those of bare land, decreasing with the increase of soil depth. In addition, plant root system increased the soil saturated water storage and capillary water storage, which were significantly different from those of bare land, so that showed the soil with root systems had a better effect on the soil water conservation than that of bare soil. In top soil, compared with
Pennisetum
sp.,
P. wettsteinii
greatly increased soil porosity and strengthened water-holding capacity more, the situation was on the contrary in deep soil. The capacity of root system to improve soil properties mainly depended on root length density and root total surface area, the roots whose diameters were smaller than 0.5 mm were the main effective factor of the soil moisture.
[Conculsions]
In summary, planting vegetation in the alluvial soil improves the soil structure, enhances the soil porosity, and raises the soil water storage capacity, thus the roots of vegetation are helpful in water conservation. In addition, these two measures are worthy of reference and popularization in the eroded area.
2017 Vol. 15 (4): 25-34 [
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540
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946KB] (
433
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35
OUYANG Qianchao, WEI Yang, ZHOU Xia, ZHANG Chaobo
Root tensile properties of the herbaceous plants for slope protection in earth-rocky mountain area, northern China
[Background]
Landslides caused by soil erosion are common natural geological disasters all over the world. Planting plants on hillsides is an effective project to conserve soil and water during urban construction and mountain development. The mechanical properties of plants are affected by many factors, such as root diameter, root length and rate of water content, as well as the loading ways, loading speed, logging time, etc. Effect of root length and diameter on root tensile properties of herbaceous plants in earth-rocky mountain area is still scarce.
[Methods]
This study aims at three slope protection plants:
Lolium perenne
L.,
Vetiveria zizanioides
L. and
Paspalum notatum
Flugge in earth-rocky mountain areas in Shanxi Province, northern China. Three different root lengths:60, 80 and 100 mm were selected in this study. Root tensile tests were conducted with a WDW-5 universal electronic testing system. In the tests, maximum tensile resistance, ultimate tensile strength and elastic modulus with changing root diameter and root length were measured and analyzed.
[Results]
The root diameter of
V. zizanioides
L. and
L. perenne
L. mainly varied in the range of 0.2-1.0 mm and
P. notatum
Flugge varied in the range of 0.1-0.4 mm, and the average values of the diameters were 0.639, 0.557 and 0.230 mm respectively. The average maximum tensile resistance of the three species was in the order:
V. zizanioides
L. (16.258 N) >
L. perenne
L. (11.734 N) >
P. notatum
Flugge (4.891 N). The average tensile strength ranked as
P. notatum
Flugge (116.226 MPa) >
L. perenne
L. (50.839 MPa) >
V. zizanioides
L. (49.650 MPa). The average elastic modulus was in order as
P. notatum
Flugge (20.392 MPa/mm) >
V. zizanioides
L. (3.257 MPa/mm) >
L. perenne
L. (3.245 MPa/mm). The elastic modulus of
P. notatum
Flugge was about six times larger than the others. With certain root length, the maximum root tensile strength of the three plants decreased with root diameter increasing. Within certain root diameter, the maximum root tensile strength decreased with root length increasing. In addition, the elastic modulus decreased with both root diameter and length increasing.
[Conclusions]
According to the results,
P. notatum
Flugge has the best ability of soil fixation and slope protection among the studied three species. It can be a suitable species to maintain soil and water. The results provide a data basis for slope protection and soil and water conservation with vegetation in earth-rocky mountain areas.
2017 Vol. 15 (4): 35-41 [
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42
ZHANG Wei, ZHU Qingke, ZHANG Chanchan, WU Tao, LIU Wei
Stand structure characteristics of broad-leaved mixed forest and point pattern analysis in loess sunny slope, northern Shaanxi
[Background]
Soil erosion is serious on the arid sunny slope in semiarid loess area. Soil moisture is the main limiting factor for the construction and restoration of forests and grass benefiting soil and water conservation. Only relying on natural enclosure is difficult to achieve ideal effects in the short term. Traditional artificial afforestation schemes ignore the heterogeneity of habitat conditions, which lead to poor afforestation survival rate, serious individual differentiation in the stand and weak overall stability. Thus, it is necessary to carry out studies on near-natural afforestation, investigating the structural characteristics and spatial distribution pattern of existing forest in the area, for providing scientific basic information concerning the construction of mixed forest of soil and water conservation.
[Methods]
In this research, a study slope (6.25 hm
2
) was selected from the western slope of loess area in Wucangpu Village, Wuqi County, northern Shaanxi. The spatial distribution, tree height and diameter at breast height (DBH) of "
Armeniaca sibirica + Populus simonii + Robinia pseudoacacia
" mixed forest were measured; the distribution characteristics of tree height and DBH were analyzed using Weibull function; and the point pattern analysis method was adopted to analyze the spatial distribution pattern of
A. sibirica, P. simonii, R. pseudoacacia
and the spatial correlation between the different populations.
[Results]
1)
A. sibirica
and
P. simonii
were the main constructive species in the study area, while
R. pseudoacacia
was the companion species and
A. sibirica
took the advantage position in the community. 2) The population of
P. simonii
featured trees in large and middle diameter class accounted for the majority; the population of
A. sibirica
featured trees in middle and small diameter class accounted for the majority; the population of
R. pseudoacacia
featured trees in small diameter class accounted for the majority. The stand overall growth was in medium status. The average height of
P. simonii
was significantly greater than that of
A. sibirica
and that of
R. pseudoacacia
, indicating that stratified structure of the stand was obvious. 3) The
A. sibirica
,
P. simonii
and
R. pseudoacacia
featured aggregated distribution within the spatial scale of 0-125 m, which reached the highest aggregation intensity when the spatial scale came to 47, 65 and 104 m, respectively. Trees were mainly distributed on the microtopography, and the maximum aggregation radius was consistent with the scale of microtopography. 4) The
A. sibirica, P. simonii
and
R. pseudoacacia
presented a negative correlation within the spatial scale of 0-125 m and acute interspecific competition.
[Conculsions]
In order to increase the survival rate of afforestation, promote the quality of quick restoration of forests and grass for soil and water conservation, it is suggested that the mixed pattern and arrangement of seeds should be designed according to microtopography, and strengthen their management and tending.
A. sibirica
and
P. simonii
may grow on microtopography with fine water conditions, like the bottom of gully.
R. pseudoacacia
may grow on undisturbed slope.
2017 Vol. 15 (4): 42-50 [
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522
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51
LÜ Gang, WANG Lei, LI Yexin, FU Xinyang, WANG Kai
Comparison of litter water-holding capacity between coniferous and broadleaf forests in low mountainous and hilly areas of western Liaoning
[Background]
Domestic and foreign scholars have conducted a lot of researches on the litter hydrological characteristics of different forest types in different regions, mathematical model of litter storage, mathematical model of litter interception and its mechanism. However, it is lack of study on the hydrological characteristics of typical forests' litters in western Liaoning area of China and the differences of hydrological characteristics of litter in different leaf shapes, to compare and analyze the water-holding capacity of litter of coniferous forest and of broadleaf forest in low-mountainous and hilly areas of western Liaoning, and provide the scientific basis and technical support for forest vegetation restoration,
[Methods]
Three coniferous forests (
Pinus koraiensis
forest,
Pinus tabulaeformis
forest and
Larix gmelini
forest) and three broadleaf forests (
Ulmus pumila
forest,
Populus davidiana
forest and
Tilia amurensis
forest) were selected as the study objects, and took 3 samples along a single diagonal line of every forest's sample plot. Maximum water-holding rate, maximum water-holding capacity, accumulated water-holding capacity, and water absorption rate were measured by indoor water immersion and related calculation.
[Results]
The average storage volume of coniferous forests was larger than that of broadleaf forests, and the storage volume of coniferous forests was between 14.65 t/hm
2
and 17.75 t/hm
2
, while that of broadleaf forests was in the range of 8.44-16.92 t/hm
2
. The average thickness of litter in coniferous forests (2.79 cm) was larger than that in broadleaf forests (2.44 cm). The maximum water-holding capacity of coniferous forests was 148.88%-173.19%, while that of broadleaf forests was 145.42%-156.91%. The modified interception volume of coniferous forests was 19.47-25.59 t/hm
2
, and that of broadleaf forests was 10.56-22.04 t/hm
2
. The water absorption rate of coniferous forests was (410.92-498.74 g/(kg·h)), while that of broadleaf forests was (449.32-508.25 g/(kg·h)).
[Conclusions]
There are differences between litter storage volume and thickness of coniferous and broadleaf forests. Water-holding capacity differentiation characteristics of coniferous forests and broadleaf forests are related to the proportion of litter decomposition layers. The ability of interception of coniferous forests is stronger than broadleaf forests. The interception volumes of semi-decomposed layer of coniferous forests are significantly larger than those of undecomposed layer, while the interception volumes of undecomposed layers of broadleaf forests are greater than that of semi-decomposed layer. The water absorption rate of undecomposed layer of coniferous forest is faster than that of semi-decomposed layer, and the semi-decomposing layer of broadleaf forest is faster than that of undecomposed layer. The water absorption rate of semi-decomposed layer decreased sharply in 0-4 h, especially in broadleaf forest.
2017 Vol. 15 (4): 51-59 [
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523
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1193KB] (
416
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60
Adilai WUFU, Yusufu MAIMAITI, Yusufujiang RUSULI, Reyilai KADEER, JIANG Hong
Spatio-temporal distribution characteristics and contributing factors of
E
a
and
E
p
in Ebinur Lake Basin during 2000-2014
[Background]
Water evaporation plays an important role in the hydrological process as it is a major part of the ecological water balance. The evapotranspiration (
E
T
) is the loss of water from the soil both by evaporation and by transpiration from the plants growing thereon. Actual evaporation (
E
a
) concerns the water evaporation from natural surfaces to the atmosphere. Potential evaporation (
E
p
) is the amount of water that would be evaporated and transpired if there are sufficient water available. This demand incorporates the energy available for evaporation and the ability of the lower atmosphere to transport evaporated moisture away from the land surface. Therefore, the evaporation can substantially influence on a regional scale the amount and spatial distribution of water resources. In-depth understanding the spatio-temporal distribution and evolution process of evaporation provides scientific basis for basin water resources planning, evaluating the condition of drought, study on ecological water demand, etc.
[Methods]
The spatio-temporal distribution characteristics and evolution trend of
E
a
and
E
p
were studied by linear trend analysis and relative variation ratio using MOD16 product and observation data of meteorological station during 2000-2014 in Ebinur Lake Basin.
[Results]
1) Inter-annual variation of
E
a
and
E
p
was not obvious during recent 15 years, the mean annual
E
a
and
E
p
were 315.76 and 1 555.27 mm respectively, and the great discrepancy between mean annual
E
a
and
E
p
showed that the whole study area was in the condition of water shortage and drought. 2) The spatial distribution of
E
a
was opposite to that of
E
p
. The northwestern mountain area, Jinghe-Bole Oasis area, western branch of northern Tianshan Mountain and Mayili Mountain area had sufficient water supply, while the most eastern area of Ebinur Lake Basin, all around of Jinghe-Bole oasis suffered from drought and water shortage. 3) Analysis of influencing factors demonstrated that temperature was the most important factor to affecting the spatio-temporal distribution of
E
a
and
E
p
in the study area. 4) The evolution trend of
E
a
was decreasing in the fifteen years, and the area with decreasing trend was accounted for 50% of the total. The evolution trend of
E
p
was increasing in the fifteen years, and the area with increasing trend was accounted for 48.39% of the total. The evolution trend of decreasing
E
a
and increasing
E
p
indicated that the condition of drought was aggravated during 2000-2014 in Ebinur Lake Basin.
[Conclusions]
According to the spatio-temporal variation and evolution trend of
E
a
and
E
p
in Ebinur Lake Basin during 2000-2014, the land surface in Ebinur Lake Basin was drought, and the condition was aggravated year by year.
2017 Vol. 15 (4): 60-67 [
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402
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6428KB] (
411
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68
ZHANG Jie, XIE Songhua, MO Minghao, TU Anguo
Characteristics of phosphorus output through runoff from different soil layers by different land cover treatments in red soil slopes
[Background]
Phosphorus from the runoff migration is one of the sources of non-point source pollution because of slope agriculture development, which is also a potential threat to the groundwater environment. The most important reason of water eutrophication is the input of external phosphorus. The migration and output process of phosphorus from the soil of slopes to water is not only the focus of soil science research, but also one of the resource and environmental problems that needs to be solved urgently.
[Methods]
In Jiangxi Provincial Eco-Science Park of Soil and Water Conservation, Drainage Lysimeter was used to study the characteristics of phosphorus output through runoff from different layers under natural rainfall conditions in red soil slopes. Three 5×15 m plots with slope of 14° were established by three land cover treatments which were
Paspalum notatum
Flugge coverage,
P. notatum
Flugge litter mulching and bare land. There were four discharge outlets used to collect surface runoff, 30 cm interflow, 60 cm interflow and 105 cm underground runoff in each plot. Runoff samples were collected and analyzed for the content of phosphorus during the three natural rainfall events process in 2013 and 2014.
[Results]
1) The total phosphorus (TP) concentration migrating through runoff decreased sharply with the increase of soil depth. The proportion of dissolved phosphorus (DP) to TP was high and stable, which was the main form of phosphorus output through runoff. 2) Output amounts of TP through runoff in three treatments decreased gradually from bare land, litter mulching to grass coverage. Under the three storm conditions, the total reduction rate of TP and DP was 35%-92% and 44%-96% respectively by grass coverage treatment, and 9%-86% and 0-89% respectively by litter mulching treatment. 3) The proportion of TP through the surface runoff reached more than 90%. The proportion of TP through interflow was relatively small of the three treatments. The proportion of TP through underground runoff which reached more than 60% was the main mode under the treatments of hay mulching and grass planting.
[Conculsions]
In the development of agriculture and forestry in the red soil slope, the vegetation cover and mulching measures may reduce the phosphorus pollutant into the water body. These findings hold important implications for soil and water loss and non-point source pollution control.
2017 Vol. 15 (4): 68-77 [
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454
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1077KB] (
463
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78
ZHU Jijie, RAO Liangyi
Analysis of the ecological effects of soil and water conservation based on emergy theory:A case study of Changzhi City of Shanxi Province
[Background]
At present, the methods of ecological effects of soil and water conservation are usually dispersed in the evaluation of the ecological system and economic system. Since two methods of evaluation and measurement are different, it is difficult to compare them. Thus it is very necessary to evaluate the ecological effects of soil and water conservation by unifying measurement units. Emergy theory is based on the solar energy, which combines the ecological system and economic system, and unifies the unit of measurement. In this way, that can overcome the difficulties from the separation of ecological and economic systems. So far, the application of emergy theory in the evaluation of eco-economic effects of soil and water conservation has not been reported.
[Methods]
Based on the theory of emergy analysis and statistical yearbooks as well as other related information of Changzhi City from 2004 to 2014, we analyzed the emergy indexes of input and output of the soil and water losses control eco-economic system in Changzhi City. By analyzing and calculating, the different materials and energy were converted into the same standard emergy. Then the analysis tables of input and output of soil and water losses control eco-economic system as well as the emergy analysis index system in Changzhi City were established for analyzing and comparing the input-output emergy values. They were used for the assessment of soil and water conservation ecological effects in Changzhi and providing theory basis for the further soil and water losses control.
[Results]
The results showed that the emergy input of the water loss and soil erosion control eco-economic system was large and the overall trend was increasing. The lowest value was 3.91×10
21
sej in 2008, the highest value was 4.33×10
21
sej in 2011. Emergy input of the water loss and soil erosion control eco-economic system in Changzhi City was overall increasing, and the local time period declined. The lowest input value was 5.95×10
21
sej in 2010, and the highest value was 7.62×10
21
sej in 2014. The total emergy of stockbreeding and vegetable production in agriculture overall increased, indicating that soil and water conservation measures have achieved some success. When the structure of the total emergy output was healthy, the net emergy output ratio both were greater than 1 and sustainable development index was in a reasonable range, indicating that the soil and water conservation measures in Changzhi City were rational and sustainable.
[Conculsions]
Generally speaking, the comprehensive level of the water loss and soil erosion control eco-economic system in Changzhi City is getting better and the sustainable development eco-economic system showed that the project's ecological and economic purpose was basically fulfilled. In order to maximize the ecological effect of soil and water conservation in Changzhi City, we should clear the direction of governance and zoning, deepen the reform of land, speed up the scale and intensive production, and strengthen the supervision and enforcement of soil and water conservation.
2017 Vol. 15 (4): 78-86 [
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609
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480
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87
DUAN Qingsong, WANG Jinxia, YANG Yang, ZI Shuhui, ZHANG Chuan, ZHANG Jiansheng, SUN Gaofeng, YU Jianxin
Soil anti-shear strength enhancement by indigenous herbaceous roots in Dry-hot Valley of Jinsha River and its modeling prediction
[Background]
It is the typical fragile ecological environment in China, with dry and hot climate, serious soil erosion, and difficulty for vegetation restoration in the Dry-hot Valley of Jinsha River. Due to the rapid growth and adaptation to the local natural environment, indigenous herbaceous plants have unique advantage in restoration of ecological environment. The aim of this study is to provide the basis for plant selection and calculating their abilities of soil fixation in ecological restoration, slope protection, soil erosion control and other ecological projects in Dry-hot Valley of Jinsha River.
[Methods]
The location of the test was in Wumao Township (E101°45' and N 25°43', with an elevation of 1280 m), Yuanmou County, Chuxiong Autonomous Prefecture of Yi Nationality, Yunnan Province, on January 2016 on hot-red soil.
Heteropogon contortus, Eulaliopsis binata, Cymbopogon distans
and
Schizachyrium delavayi
, widely distributed in Dry-hot Valley of Jinsha River, were selected to measure the shear strength of root-soil composites by in-situ direct shear test, and compared with bare soil. Five treatments with six replicates were set up. No significant difference about soil moisture and density of roots-contained soil were found in the treatments, except that density between the root-soil composites and bare soil. Shear strength and displacement of composite of the root-soil composites and bare soil with 200 mm length×200 mm width×100 mm height centering on the plant was test by the Pull Test Instrument for Bolt (ML-20, Qingdao Yifeng Instrument Manufacturing Co., Ltd.). Root tensile strength was test by digital pull tester (SN100, Shadu Instrument Manufacturing Co., Ltd.). The data such as root diameters, quantities and tensile strength was put to Wu & Waldron vertical root model (WWM) and Fiber bundle root enhancement model (FBM) respectively to predict the enhanced shear ability by roots.
[Results]
1) Root diameters of four herbs were distributed mainly in the range of 0.1-1 mm. The relationship between root diameter and tensile strength of
H. contortus
,
E. binate
and
S. delavayi
was a negative power function, while
C. distans
' had no correlation. 2) Compared with bare soil, the soil shear strength was improved 20.7%, 85.3%, 84.4% and 16.1%, respectively by the roots of
H. contortus
,
E. binate
,
S. delavayi
and
C. distans
. 3) The predicted value was 3.59-10.83 times of the measured value, by using WWM model to predict the shear capacity of the soil. The predicted value of the FBM model was 1.24-2.62 times of the measured value.
[Conclusions]
The ability of
E. binate
to improve the shear strength of soil is stronger than
S. delavayi
, thus it could be selected as the priority of ecological construction in Dry-hot Valley of Jinsha River. FBM model was better than WWM model, in terms of prediction of shear strength of soil enhanced by roots.
2017 Vol. 15 (4): 87-95 [
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536
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96
YAN Dongfeng, WU Guizang, GUO Dandan, ZHANG Zhen, YANG Xitian
Short-term effects of moderate fire disturbance on soil physical and chemical characteristics of woodlands and grasslands
[Background]
Fire is recognized as a natural disturbance phenomenon that could significantly affect soil physical, chemical, mineralogical, and biological characteristics. The objective of this study is to evaluate the short-term effects of moderate fire disturbance on soil physical and chemical characteristics of woodlands and grasslands under different soil depths in Juci Mountain, Henan Province.
[Methods]
Soil samples from grasslands and woodlands at 0-5 and 5-10 cm soil depths of burned and unburned soil were collected by small circular knife, relative indices indicating soil infiltration and soil water storage capacity were determined via traditional methods such as the method of double-ring permeation. The short-term effects of moderate fire disturbance on soil infiltration and soil water storage capacity of woodlands and grasslands under different soil depths were studied by t test using t test function in R software.
[Results]
Results showed that moderate fire disturbance had a great influence on soil infiltration and water storage capacity. Compared to unburned soil, burned soil of both woodlands and grasslands exhibited a significant decrease in soil bulk density, soil water content and soil non-capillary porosity at soil top 5 cm layers (
P
<0.05), but no significant changes were observed of above soil properties between burned and unburned soil at 5-10 cm soil depth (
P
>0.05). A significant decrease in organic carbon and total nitrogen of burned soil and a significant increase in pH, total P and total K of burned soil than that of unburned soil of both grasslands and woodlands at 0-5 cm layer were noted (
P
<0.05), the similar discipline was found at 5-10 cm soil depth of grasslands. No significant changes of soil chemical characteristics were observed between burned and unburned soil of woodlands. Results showed that soil initial infiltration rate, stable infiltration rate and average soil infiltration rate at soil 0-5 cm soil depths of both grasslands and woodlands increased significantly after moderate fire disturbance (
P
<0.05), but no significant changes were observed at 5-10 cm soil depth (
P
>0.05). Soil maximal water storage capacity and soil non-capillary water storage capacity significantly decreased from 289.984 t/hm
2
and 390.971 t/hm
2
of unburned soil to 258.072 t/hm
2
and 342.386 t/hm
2
of burned soil (
P
<0.05), respectively, at 0-5 cm soil depth of grasslands and woodlands.
[Conclusions]
This study provides better understanding the influence of fire disturbance on the soil infiltration and water storage capacity, and suggests that a burned area is expected to have a faster infiltration rate and a lower water storage capacity than an unburned area especially in top 5 cm soil layer. More works should be done to improve the soil and water storage capacity in burned zone in Juci Mountain area.
2017 Vol. 15 (4): 96-103 [
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418
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104
CHANG Chenchao, CHENG Donghui, QIAN Kang
Water content distribution of unsaturated layered sediments of Weihe River in Xianyang section
[Background]
Layer structure is the most common sedimentary structure in alluvial unconsolidated sediments, which usually exhibits special hydraulic properties to influence water flow and water retention ability. In this paper, a situ investigation on the water content distribution, grain-size and bulk density for a layered sediment profile was conducted at the floodplain of Weihe River in Xianyang, in the center of Shaanxi, then the effects of the grain-size and the capillary barriers on natural water content were discussed.
[Methods]
The experiment site outcrop was mapped into 11 macro layers having different texture and structures. With each layer, well developed laminations were observed. We investigated the characteristics of water content and its corresponding influence factors including soil bulk density, grain-size and matric suction in each layer, based on sampling analysis and the measurement of EC-5 Small Soil Moisture Sensor and MPS-6 Calibrated Water Potential Sensor. Firstly, we analyzed the relationship between grain-size and water content in each layer, based on this, the effect of capillary barriers on water content was discussed. Then, we analyzed the influence of capillary barriers in the process of precipitation infiltration and soil water evaporation.
[Results]
The results illustrated that in the layered alluvial sediments with alternating layers of coarse and fine sands, natural water content exhibited in a layered distribution on a form of interbedding high and low water content. The magnitude of the water content was negatively correlated with the grain-size, and was positively correlated with the bulk density. The water content of site outcrop was between 0.010 cm
3
/cm
3
-0.148 cm
3
/cm
3
, the median size ranged from 0.16 mm to 0.39 mm and the bulk density ranged from 1.32 g/cm
3
to 1.53 g/cm
3
. The results also demonstrated that the layered sediments with alternating layers of coarse and fine sands formed the capillary barriers in the process of water flow, therefore by which the water content distribution was controlled. In both process of precipitation infiltration and soil water evaporation, the capillary barriers effects will lead to the water content in fine layer obviously higher than that in coarse layer.
[Conculsions]
In conclusion, capillary barriers become a significant factor to control water flow in unsaturated soils. At the process of precipitation infiltration, capillary barriers have the effect on permeability reduction, which can be used in designing landfill anti-seepage system, optimized drainage layers and so on. Additionally, insights are potentially useful for designing mulching strategies and capillary barriers aimed at reducing evaporative losses, increasing water retention ability of soil, which is significantly important in arid and semi-arid regions.
2017 Vol. 15 (4): 104-110 [
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111
YANG Wenda, WANG Guiyao, CHANG Jingmei, ZHANG Yongjie
Study on pull-out force in taproot by indoor test
[Background]
The deep anchoring effect of trees taproot and shrubs taproot on soil of slope can significantly improve the stability of slope. But in the rainfall conditions, whether the plant can play a favorable role in the stabilization of slope is controversial. Therefore, this has caused obstacles to judgement of pull-out force of taproot in rainfall conditions.
[Methods]
To study the factors that affect the pull-out force of taproot, the
Symplocos sumuntia
taproot was selected as the research object in this paper, and was used to study on the problem of pull-out force of taproot. Among them, pull-out tests were carried out under 4 soil water content conditions(10%,15%,20%,and 25%) and 3 vertical stress conditions(3.06 kPa,6.13 kPa,and 9.19 kPa), and pull-out tests contains two parts:single pull-out test and cyclic pull-out test. The pull-out test device was designed as in Figure 2 by our own laboratory.
[Results]
1)The taproot pull-out force increased with the increase of stress on the taproot surface and gradually became stable. The single pull-out test results showed that, taking soil water content of 11.74% of the situation as an example, when the vertical stress was 3.06 kPa, 6.13 kPa and 9.19 kPa, the taproot average pull-out stress was 42.61 Pa, 71.52 Pa and 91.36 Pa. 2) With the increase of soil water content, the taproot pull-out force increased firstly and then decreased. The single pull-out test results showed that, taking vertical stress of 3.06 kPa of the situation as an example, when the soil water content was 11.74%, 16.02%, 21.11% and 26.53%, the taproot average pull-out stress was 42.61 Pa, 61.79 Pa, 70.35 Pa and 63.11 Pa. 3) When the soil was clay, the corresponding soil water content of the greatest pull-out force of
Symplocos sumuntia
taproot was 22%. 4) In the low state of stress, taproot external organizational integrity had a greater effect on the pull-out force; while in the high state of stress, taproot internal organizational integrity had a greater effect on the pull-out force. Taking soil water content of 16% of the situation as an example, when the vertical stress was 3.06 kPa and 9.19 kPa, the average pull-out stress obtained by the cyclic pull-out test was 40.79 Pa and 101.03 Pa. And the average pull-out stress obtained by the single pull-out test was 61.79 Pa and 109.01 Pa.
[Conclusions]
Experiments show that the soil properties and water content, root surface stress and integrity will have a significant effect on the pull-out force of taproot. And, as long as the soil water content does not exceed the optimal value, the anchoring effect of the taproot will be fully exerted.
2017 Vol. 15 (4): 111-116 [
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492
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117
XIA Xiaoping, XIN Zhongbao, KONG Qingxian, ZHANG Dong
Vegetation and soil physicochemical properties in different types of the Huaijiu River riparian in Beijing
[Background]
As an important component of riparian ecosystem, vegetation and soil are closely related to the biodiversity, stability, nutrient filter in riparian. To date, however, there are few studies about the spatial variation of the riparian vegetation communities and soil physicochemical properties under different types of riparian.
[Methods]
The study was carried out in the Huaijiu River, southwest of Huairou district, Beijing. According to the extent of disturbance and development status of riparian zones, we divided it into three types (natural type, near-natural type, and artificial type). Then, based on the survey of 15 natural type plots, 25 near-natural type plots and 20 artificial type plots, we investigated the vegetation diversity and the soil physicochemical properties and compared them between different riparian types.
[Results]
Vegetation diversity and soil physicochemical characteristics were significantly different in different types of riparian. The vegetation composition in the riparian of the Huaijiu River was mainly herbs, accounting for 79.22% of the total number of species, and of species diversity (4.6±0.16) and species richness index (7.26±0.40) of the natural type riparian was greater than the near-natural type (3.82±0.16 and 6.36±0.32) and the artificial type (3.94±0.18 and 5.40±0.42) (
P
<0.05); The soil quality showed a degradation trend with increasing magnitude of disturbances. The soil organic matter content of the natural riparian (4.88±0.43%) was higher than the near-natural riparian (3.47±0.31%) and artificial riparian (1.92±0.15%) (
P
<0.05). The soil bulk density of the natural type was lower (1.18±0.03 g/cm
3
) than near-natural riparian (1.35±0.03 g/cm
3
), and the soil bulk density of artificial riparian was the highest, which was matter content (
P
<0.05), while the richness index was negatively correlated with soil bulk density (
P
<0.01) and positively correlated with soil total porosity (
P
<0.05).
[Conculsions]
The results showed that the correlation relationship between vegetation and soil was influenced by human disturbances. It provides a theoretical basis for the restoration and reconstruction of riparian ecosystem in Beijing mountain area.
2017 Vol. 15 (4): 117-124 [
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125
FANG Pei, XIA Yu, LIU Hanxiao, WANG Feng, YANG Jianying, SUN Shengnian, SHI Changqing, GENG Xuemeng, ZHAO Tingning, LI Qiang
Effects of plant growth retardants on the germination of 3 herbaceous seeds in slope greening in North China
[Background]
Herbs can reinforce a large number of exposed slopes left by construction work of roads, railways and mines and other projects. It also improves their ecological environment. In comparison of the shrub seeds, the herbaceous seeds germinate and grow more rapidly. Moreover, the herbaceous seeds are more competitive than shrub seeds in herb-shrub mixed type, which is the target community in the slopes greening. The application of plant growth retardants in lawn conservation is more extensive. However, there are few studies on the soaking treatment of herbaceous plants in slope greening. Therefore, it is necessary to develop the study of plant growth retardants to inhibit the germination of herbaceous seeds.
[Methods]
In this paper,
Astragalus adsurgens, Medicago sativa
and
Festuca arundinacea
,that are widely used in slopes greening in North China, were selected as the test materials. Chlormequat, uniconazole and paclobutrazol were chosen as test retardant reagent. A seed soaking experiment was carried out by using different density and kind of above three plant growth retardants. Firstly, three herbs seeds were soaked in different concentrations of chlormequat, paclobutrazol and uniconazole solution. Then three seeds were taken out, washed and placed in a constant temperature incubator within 15 days. Finally, the germination energies of three herbs and their effects of radicle and embryo growth were analyzed.
[Results]
For
A.adsurgens
, the optimal paclobutrazol soaking concentration were 300-500 mg/L, and optimal chlormequat soaking concentration was 100 mg/L. For
M.sativa
, the optimal paclobutrazol soaking concentration was 480 mg/L, and optimal uniconazole soaking concentration was 320 mg/L. For
F.arundinacea
, the optimal chlormequat soaking concentration was 520 mg/L, and optimal paclobutrazol soaking concentration was 420 mg/L. Chlormequat and uniconazole solution reduced the ratio of germ length of
A.adsurgens
and
M.sativa
, and increased the ratio of radicle length. The germination energies of the three herbaceous seeds were inhibited by the 300-400 mg/L paclobutrazol solution. The germination energies of
A.adsurgens
and
F. arundinacea
were inhibited by 500 mg/L uniconazole solution. The inhibitory effect of chlormequat solution on the germination energy of
M.sativa
and
F.arundinacea
was significant. And the higher the concentration of chlormequat solution, the stronger the inhibitory effect on the length of their embryo.
[Conculsions]
The inhibitory effect of paclobutrazol on the germination energy of
A.adsurgens, M. sativa
and
F.arundinacea
was significant, and also inhibited the germ length of
A.adsurgens
and
M.sativa
. Uniconazole had a significant inhibitory effect on
A.adsurgens
and
F.arundinacea
. Therefore, three plant growth retardants inhibited the germination of three herbaceous seeds, which provides reference index for plant growth retardants to treat herbaceous seeds in slopes greening.
2017 Vol. 15 (4): 125-133 [
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134
WEN Wanxin, WANG Dongmei, ZHANG Linlin, REN Yuan
Model of calculating suitable volume of rainwater tanks for real estate construction projects
[Background]
China is on the peak of urbanization. However, with increased hardened proportion and imperfect drainage measures in cities, rainstorms cannot efficiently infiltrated and ultimately resulted in the formation of waterlogging. As the best measure of reducing flood, solving water pollution and shortage, the rainwater tank has been promoted and applied widely. Though rainwater tank was widely used in estate construction projects and was advocated in a larger volume on the principle of none out drainage, few studies had been conducted on it. Otherwise, the design of rainwater tanks in our country is mainly based on the experience formula of foreign countries, or estimated by the annual rainfall. Therefore, a convenient and reliable method for calculating the volume of rainwater tank is very important to the development of the city.
[Methods]
We took nine construction projects in Beijing as the research site, selecting three kinds of daily rainfall (maximum, average and minimum) from the rainfall data of Beijing during 1953-2012. We assumed recycled rainwater used for both greening and road sprinkling. Applying the method of daily water balance model, we analyzed trends of rainwater tank availability and reclaimed water recharge rate. We suggested an appropriate volume of rainwater tank after taking the economy benefits. Applying the method of polynomial fitting, the model of calculating suitable volume of rainwater tanks was obtained. Lastly, we used five construction projects for verification.
[Results]
With the increasing of rainwater tank volume, rainwater tank availability becomes higher (0-1) and reclaimed water recharge rate becomes lower (1-0). When rainwater tank volume reaches to a certain level, the tendency of rainwater tank availability and reclaimed water recharge rate become gentle. The rainwater tank availability relationship of three years is maximum year > mean year > minimum year. The reclaimed water recharge rate relationship of three years is maximum year < mean year < minimum year. The trend of rainwater tank availability and reclaimed water recharge rate is complementary. The benefit-cost ratio becomes lower as rainwater tank volume increase.
[Conclusions]
In this study, we set up a simple and convenient calculation model of volume of the rainwater tank. It can enhance accuracy in practical application by comparing the results of model calculation and the minimum construction standards. We need to strengthen the maintenance and management of the rainwater tanks after completion for increasing revenue by extending service life. The future study of rainwater tanks should be focused on the more abundant data samples, additional safety volume of it, and negative impact of sediment accumulation.
2017 Vol. 15 (4): 134-142 [
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143
ZHANG Guanghui
Potential effects of changes in near soil surface characteristics driven by farmland abandonment on soil erosion
[Background]
The Loess Plateau is one of the most erodible regions in China, even over the world. The erosion intensity and properties of spatial and temporal distribution are significantly affected by near soil surface characteristics. The effective implementation of the "Grain-for-Green" project certainly causes the great changes in near soil surface characteristics, i.e. soil physiochemical properties, vegetation stem, litter, biological soil crust, and root system, which will lead to great influences on hydraulics of overland flow and soil erosion processes.
[Methods]
We collected 74 references from relevant studies in the past several decades, and comprehensively analyzed them. We presented the review results by 1) the changes in near soil surface characteristics driven by "Grain-for-Green"; 2) the effects of changes in near soil surface characteristics on hydraulics of overland flow; 3) the potential effects of changes in near soil surface characteristics on soil erosion processes (soil detachment, sediment transport, and sediment deposition) and their mechanisms; 4) the responses of regional soil erosion to "Grain-for-Green"; and 5) research prospects in this field.
[Results]
1) There were great changes in near soil surface characteristics, i.e. soil physiochemical properties, vegetation stem, litter, biological soil crust, and root system. 2) The effects of changes in near soil surface characteristics on hydraulics of overland flow after "Grain-for-Green" project were related to plant flexibility, density and arrangement, types of litter, coverage and thickness, type of biological crusts, a variety of factors, community structure and coverage etc. 3) Soil detachment was decreasing with the years of "Grain-for-Green" increasing, also fluctuating due to many factor, and finally reached stable. Vegetation from "Grain-for-Green" decreased the sediment transport in the runoff duo to the existence of vegetation stems and bio-crust though the mechanisms were extremely complex. Moreover, grass after "Grain-for-Green" significantly retained sediment. 4) In general, the changes in near soil surface characteristics enhanced the soil resistance to both of overland flow and soil erosion, though the mechanisms have not been fully understood yet.5) Thus more studies are needed in the future a) the effects of changes of near surface characteristics driven by "Grain-for-Green" on the hydraulic characteristics of runoff on slope and its mechanism; b) the separation capacity model on farmland under the condition of "Grain-for-Green", especially the functional relationship between rill erodibility, critical shear stress and near surface characteristics; c) the overland flow sediment transport capacity equation under the condition of vegetation restoration; d) and sediment deposition process and simulation on vegetation covered hillslopes.
[Conclusions]
This review is conducive to understand soil erosion processes and their dynamic mechanism, to develop process-based soil erosion models, and to evaluate soil and water conservation benefits for vegetation covered hill-slopes.
2017 Vol. 15 (4): 143-154 [
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501
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