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2008 Vol.6 No.2
Published 2008-04-30
Articles
1
BAO Xiao-Bin-；Li-Zhou
Policy changes and its evaluation of soil and water conservation in China
The policies of soil and water conservation were transformed from unilateral to multiple patterns in China.The stage changes of the conservation targets,the stakeholders,and conservation areas happened in the course of implementing soil and water conservation.The policy framework of soil and water conservation was constructed by means of implementing measures of relative policies.Applying the institution conomics,environmental economics,and expert consultation,the policy impacts were comprehensively evaluated in this paper.By comparing the outcomes of the policy implementation with the expected policy targets,the task identification,measure arrangement,organization methods,and operating efficiency for soil and water conservation project could be confirmed.Furthermore,the main experiences and existed issues on policy implementation of soil and water conservation were summarized.The approaches for improving the policies of soil and water conservation were advanced.
2008 Vol. 6 (2): 1-7 [
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8
YANG Chao-；Chen-Jie-Ren-；Zhou-Yi-；Tao-Wen-Yi-；Chen-Chi-；Shi-Hua-Jian-；Xu-Yi-；Huang-Guo-Ru
Scenario simulation of runoff and sediment processes in the small catchment in the Hilly-gully region of Loess Plateau
Based on the runoff and sediment yield mathmatical model for the Chabagou catchment in Hilly-gully region,a typical small catchment in the middle stream of Yellow River,was selected to simulate the runoff and sediment yield under several various possible situations.Firstly three designing precipitation schemes with the occurring period of 100,50 and 10 years respectively were computed and used in runoff and sediment yield simulation.Then three vegetation cover schemes were used in the scenario simulation.Results indicate: 1) The flood and sediment transport peak for the designing-strom event with 100-year period(
P
=0.01) is 805 m
3
/s and 775×103 kg/s,it is 595 m
3
/s,502×103 kg/s for those of 50-year period(
P
=0.02) and 108 m
3
/s,121×103 kg/s for those of 10-year period(
P
=0.1),It can be inferred that the occurring period of 19890701 storm event is between 100 and 50 years according to the simulation results;2) The positive impacts of vegetation coverage on reduction of water yield and soil erosion of catchment are detected,in which,reduction of 73% and 84% for water yield and sediment yield with 25% decreasing of vegetation coverage are identified,whilst,the simulated water and sediment yield will increase by 29.9% and 18.6% if the study catchment suffers 25% decreasing of vegetation coverage.The results of this investigation will be greatly benificial to regional,soil and water conservation planning and designing in Hilly-gully region.
2008 Vol. 6 (2): 8-14 [
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15
SONG Wei-Feng-；Tu-Xin-Xiao-；Zhang-Ying
Effects of slope grade and cover of
Robinia pseudoacacia
on runoff and soil loss from loess slopes under simulated rainfall
The experiment of simulated rainfall was carried out by using the soil taken from the artificial forest of
Robinia pseudoacacia
from Caijiachuan of Jixian County of Shanxi Province in the Loess Plateau.The young trees of
Robinia pseudoacacia
were planted as a vegetation cover for the experiment slopes.The amount of runoff and soil erosion was collected from slopes of different slope grades with the cover of
Robinia pseudoacacia
.The results showed that under a given condition of certain rainfall intensity and slope grade,with increasing of slope grade,the generation of runoff and soil loss starts earlier,the runoff velocity is higher,the crown interception percentage and the runoff amount increases,the soil loss yield increases;The relation between the crown interception of forest and the slope grade is
I
=29.556
α
-0.311
(
R
2
=0.987 4),and the relation between the soil loss from covered slope and the slope grade is
W
=0.116 84
α
3.005 9
(
R
2
=0.979 5);Under the same condition of slope grade,the runoff and soil loss from
Robinia pseudoacacia
covered slope is less than that from the bare soil slopes,showing a difference of 15%-25% in the average velocity of runoff,15%-48% in runoff,10%-117% in soil loss,55.5%-133% in the average sediment concentration.
2008 Vol. 6 (2): 15-18 [
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1710
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19
XU Jing-Hua-；Wang-Guo-Liang-；Chen-Yun-Meng-；Lei-Jian-Li
Infiltration characteristics of soil and its influencing factors in abandoned farmland in the Hilly-gully region of Loess Plateau
Studying on infiltration characteristics of abandoned farmland in Loess Plateau will provide scientific basis for evaluating benefits of abandoned farmland during vegetation restoration and cognizing the influence by variations of underlying surface on soil hydrological processes.This paper studied the characteristics of soil infiltration by disc-permeameter and discussed its influencing factors in 4、6、8 years abandoned farmland.Taking the natural grassland as CK,the characteristics of soil infiltration were tested and its influencing factors were discussed in 4、6、8 years abandoned farmland in this paper.The results indicate: 1) the permeability of surface layer in natural grassland is better than that in short-term abandoned land,but in the lower layers(20 cm、40 cm)they are just contrary to that in surface layer;2) The initial infiltration rate in lower layer is 1.2 to 1.4 times faster than that in surface layer,and the final infiltration rate in lower layers is 1.9 to 2.8 times faster than that in surface layer,and the saturated hydraulic conductivity in lower layers is 1.9 to 3.0 times faster than that in surface layer;3) The permeability of surface layer drop with the increasing of years,but the opposite trend appear in lower layers;4) Soil crust is an important factor which effect permeability of surface layer.
2008 Vol. 6 (2): 19-25 [
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1597
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26
DONG Zhi-；Gu-Yu-；Li-Gong-Li
Spatio-temporal variation characteristics of dust-storm in Alaxan region of Inner Mongolia Autonomous region
Based on the observed dust-storm data of Alaxan region of Inner Mongolia from 1961 to 2003,the spatial distribution characteristics,seasonal and yearly and decadal temporal variation characteristics and the cause of dust storm were analyzed.The results showed as followed: The dust-storm-days radiation decreased from Guaizi lake as center to other area all around in spatial,and the dust storm occurred frequently in the north and east and less in the west and south of this region;the days of dust storm took on more in spring and summer,but less in autumn and winter,the years which was more than average days of dust storm occurring was few in yearly during 43 years,the dust-storm-days occurring was most in 20 century 70's,and it had trend to decline after 70's.The variation of the dust-storm-days is in response to some special climate variation,geographical situation and environment,the relationship between dust-storm-days and strong-wind-days has been positive correlation,and the intensity of dust-storm-days negatively correlated with the air temperature and precipitation of last year,further more,the linear relation was accorded with between average monthly days of dust-storm and average monthly strong-wind-days,the correlation coefficient is 0.988 5.The result can provide science gist to preventing and controlling the dust-storm for Alaxan region.
2008 Vol. 6 (2): 26-31 [
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32
LIAO Xi-Shan-；Ca-Jiang-Guo-；Cheng-Qin-Juan
Critical topographic condition for slope erosion in Hilly-gully region of Loess Plateau
This paper tries to explain the effects of slope gradient,slope length and rainfall on slope erosion from the viewpoint of energy.Analyzing data about slope gradient,slope length and rainfall observed at Ansai station in Shanxi Province and Wangjiagou small watershed in Lishi,west of Shanxi Province,the author aims to know the influences of rainfall,slope gradient and slope length on slope erosion.The result shows that the influence of rainfall on slope erosion amount is the biggest,slope gradient is the second,and slope length is the smallest. Critical slope gradient is influenced by factors of rainfall and slope length,and critical slope length is influenced by factors of rainfall,slope gradient and slope length.Critical slope gradient or slope length is not a constant value,which varies in some ranges and depends on the factors of rainfall,slope type.The results provided the scientific theory basis for slope erosion control in the Hilly-gully region of Loess Plateau.
2008 Vol. 6 (2): 32-38 [
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39
HONG Li-Na-；Mu-Xin-Min-；Zhang-Xiao-Ping-；Li-Yan
Calculation method of mean rainfall amount of river basin in the Hilly-gully region of Loess Plateau of Northern Shaanxi Province
It is crucial to calculate method of areal precipitation and the selection number of rainfall station` for mean precipitation in a river basin.The data about respective rainfall station of Kuye,Tuwei,Jialu River Basin,which located in the Hilly-gully region of Northern Shaanxi Province within the period of 1981 to 1986 were used as rainfall data relatively put together.Using Taisen polygon to calculate area mean rainfall as reference values.Analysing the relationship between maximal proportional error absolute value and the number of rainfall station by using arithmetic average law under various rainfall station combination condition.Conclusion as follow: in the river basin,increasing the number of rainfall station,maximal proportional error absolute value seems to be the decrease trend.In Kuye river the proportional error absolute values,between the calculated area mean rainfall value which accord to selecting 9 rainfall stations in Upper,Middle and Lower river,and reference values,are all within 10%.With the same method,Tuwei river's and Jialu river's the proportional error absolute values are 5 percent.This research technique has provided the method which is how to deal with the individual rainfall station data lacks,in the rainfall material limited situation and in research precision scope.This paper also displayed the simple feasible method and the theory basis.
2008 Vol. 6 (2): 39-42 [
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1606
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43
DIAO Hu-Bing-；Liu-Guo-Ban-；Cao-Qing-Yu
Influence of different vegetation types on soil and water conservation function and nutrients loss in the Hilly-gully region of Loess Plateau
The plot experiment of 10 vegetation types including 3 grass,3 shrub,3 arbor,and 1 farmland was carried out at Ansai Soil and Water Conservation Research Station in Hilly-gully region of Loess Plateau.Runoff and soil erosion data were observed.Runoff and nutrients content of sediment were analyzed in order to know the influence of different vegetation types on soil and water conservation function and nutrients loss.The obtained results show that the grass,shrub,and arbor vegetation types have much better soil and water conservation function comparing with farmland.The grass,shrub,and arbor have much less runoff and nutrient loss comparing with farmland.So the grass,and arbor vegetation should be rehabilitated and developed quickly in order to decrease soil erosion in Hilly-gully region of Loess Plateau,and then decrease soil nutrients loss.
2008 Vol. 6 (2): 43-48 [
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1334
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49
NA Lei-；Zhang-Jian-Jun-；Shu-Jin-Zhao-；He-Wei-；Dong-Huang-Biao-；Yang-Guo-Yang
Runoff and sediment processes of the small watersheds under different land use in the Loess Region of Western Shanxi Province
As an important parts of watershed hydrology research,study on runoff and sediment process is the fundamental content of watershed hydrology modeling.The watershed in West of Shanxi Province which is a national forestry ecology research station was analyzed by experiments,runoff and sediment process from different types of land use was researched by contrastive analyzing.The results show that during the representative rainfall events(rainfall amounts: 8.6 mm and 13.6 mm),suspended sediment concentration varies synchronizing with flow discharge in agricultural and stock breeding watershed.And it is obviously that peak of suspended sediment concentration lags behind flood peak in natural forested watershed.Modules of surface flow and sediment yield were highest as 2.40%、6.40% and 6.71 t/km
2
、73.69 t/km
2
in agricultural watershed,and lowest as 0.13%、0.75% and 0.02 t/km
2
、6.95 t/km
2
in natural forested watershed.
2008 Vol. 6 (2): 49-54 [
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1419
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55
HU Zhen-Hua-；Wang-Dian-Long-；He-Qi-Ti-；Li-Xin
Infiltration laws of weathering gangue
This paper deals with the weathering gangue infiltration laws of four densities (1.20 g/cm
3
,1.30 g/cm
3
,1.45 g/cm
3
,1.55 g/cm
3
) and three kinds of mixed ratio(1∶0.5,1∶1.0,1∶2.0).The results showed that as the density increasing,infiltration rate of gangue decreases fast: the starting infiltration rate,constant infiltration rate,average infiltration rate of 1.20 g/cm
3
are 2.21 times,1.92 times,2.30 times as large as those of 1.30 g/cm
3
respectively,are 60.00 times,102.54 times,129.13 times as large as those of 1.55 g/cm
3
respectively,and the relation between density and infiltration rate is the power function;As the mixed ratio increasing,infiltration rate of gangue decreases fast: the starting infiltration rate,constant infiltration rate,average infiltration rate of the mixed ratio(1∶0.5) are 1.05 times,1.23 times,1.42 times as large as those of the mixed ratio(1∶1.0) respectively,are 3.98 times,1.45 times,3.18 times as large as those of the mixed ratio(1∶2.0) respectively;Under the density of 1.20 g/cm
3
,1.30 g/cm
3
and mixed ratio of 1∶0.5,1∶1.0,the ideal formula to express the process of infiltration is universal empirical formula and Kostiakov formula,under the density of 1.45 g/cm
3
,1.55 g/cm
3
and the mixed ratio of 1∶2.0 the best formula is the universal empirical formula.
2008 Vol. 6 (2): 55-59 [
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1358
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60
DAI Hua-Long-；Cao-Shu-You-；Liu-Xin-Nian-；Lei-Xiao-Zhang
Prediction of water erosion on purple soil slope based on WEPP model
Based on WEPP model,this paper evaluate the intensity of erosion on purple soil slope,advance methods to assess the model parameters and use long-term observation data which belongs to the station of soil and water conservation in the city of Suining in Sichuan Province,test precision and sensitive degree that forecasted in the model;discuss the possibility that the model be used to purple soil hilly area in mid Sichuan and the existent problems which would be brought in the model parameter choice.Applying WEPP model the erosion which was caused by rainfall was forecasted,then practical measure data were cpmpared.The result indicate that the data which were forecasted in the model was in reason most of the time,on low grade slope the forecasted data was higher than practical measure data,on high grade slope it was lower.Not only forecasted data were close with practical measure data,but also the model can estimate space-time distribution of the soil erosion,namely,it can estimate the changes in the completely quantity of soil and water loss on all or a random point on slope along with time,it is very important for the disposal of control measure in soil and water conservation.
2008 Vol. 6 (2): 60-65 [
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1557
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66
AN Shao-Shan-；Zhang-Yang-；Zheng-Fen-Chi
Fractal dimension of the soil aggregate and its responds to plant rehabilitation in the Hilly-gully region of Loess Plateau
The characteristics of soil aggregates fractal dimension and its responses to vegetation rehabilitation were studied in the Hilly-gully region of Loess Plateau.The results indicated that: 1) In the beginning of rehabilitation,the >10 mm soil aggregates were higher both in 0-20 cm and 20-40 cm,which were between 331.4-525.6 g/kg.Along with the increasing of rehabilitation ages,10-7 mm,7-5 mm,5-3 mm,3-2 mm,2-1 mm soil aggregates declined,the contents of 1-0.5 mm,0.5-0.25 mm and 5 mm decreased quite fast.After seven years rehabilitation,big grade size aggregates were lower in surface layer than sub-surface layer.Compared to the result of dried sieving way,soil water stable aggregates had more even and stable distribution.Soil aggregates which >0.25 mm was mainly 40%-50% after 7 years rehabilitation,in total aggregates,but >5 mm soil aggregate was only 10%-23% approximately.During the process of vegetation rehabilitation,it had the trend that big size soil aggregates converted to small size aggregates,the granule size was more uniformity which showed that good soil structure was formed.3) The fractal dimension of soil aggregates in different rehabilitation ages were between 2.75-2.86 in the surface layer and 2.77-2.89 in the subsurface layer,soil fractal dimension was declined along with the rehabilitation years increasing.
2008 Vol. 6 (2): 66-70 [
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71
CHANG Qiang-Rui-；Yue-Qiang-Ling
Soil fertility quality of artificial forest in the Hilly-gully region of Loess Plateau
Taking Wuqi County of Shaanxi Province as an example,in order to compare the effects of the different plantation on the soil fertility in Hilly-gully region, the determination analysis of soil samples and the mathematical statistic were carried on the different shrub and the arbor tree land.The result indicated: 1) The soil AN and AK content of
Caragana intermedia
was the twice of
Hippophae rhamnoides
,there was the extremely remarkable level between them.The improving effect of soil fertility of
Caragana intermedia
was better than
Hippophae rhamnoides
.Only from the improving of soil fertility,it is suggested to plant
Caragana intermedia
as a good choice.2) From the young-age of arbor tree land to the mature wood,the soil TN,AN,OM and CEC content was unceasingly increases,the soil AK,TP and AP content had the slight increase,the surface gathering of soil OM and nutrient was obvious and strengthening.In overall, in 0-100 cm soil layer of arbor tree land,the soil AN,AK,OM,CEC,TN,TP and TK content were higher than those of the shrub land.It indicated that the contribution to soil fertility of arbor tree land was better than that of the shrub land.
2008 Vol. 6 (2): 71-74 [
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1550
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75
ZHOU Ping-；Liu-Guo-Ban-；Hou-Chi-Lu
Fractal features of soil aggregate structure under different land use in the Hilly-gully region of Loess Plateau
The status of soil aggregates,water stable aggregates and microaggregates are important factors affecting soil structures and features.Based on the fractal theory,the fractal dimension of soil aggregates and microaggregates structure under seven different land use types in Zhifang Hilly-gully region was studied.The results showed that: the fractal dimension of the upper layer(0 to 20 cm) soil aggregate structure under these seven land use types ranged from 1.641 to 2.114.The fractal dimension of soil aggregate of artificial meadow was highest,followed by orchard,slope crop-land,arbor forest land,shrub land,natural meadow and artificial terrace.The fractal dimension of water stable soil aggregate ranged from 1.744 to 2.384,the fractal dimension of orchard water stable soil aggregate of artificial meadow was highest,followed by arbor forest land,artificial meadow,slope crop-land,natural meadow,artificial terrace and shrub land.Both of the conditions showed the same law: The lower total amount of the soil aggregates(more than 0.25 mm) was,the higher fractal dimension was.There were remarkable negative correlation between the fractal dimension and not less than 5 mm, 5 to 2 mm and not less than 0.25 mm soil aggregates and water stable aggregates contents.But significant positive correlation with less than 0.25 mm soil aggregates.Considered the rate of soil structural damage,the soil structure and stability of shrub land was the highest,the next was natural meadow,artificial meadow was the lowest among these seven land use types.In the upper soil layer (0 to 20 cm) the range of fractal dimension of soil microaggregate was 2.360 to 2.487.The fractal dimension of soil microaggregate of natural meadow was highest,followed by arbor forest land,slope crop-land,artificial terrace,artificial meadow,orchard,and shrub land was the lowest of that.It was showed that shrub land and natural meadow were beneficial to forming soil microaggregates. The correlation analysis results showed that fractal dimension had remarkable negative correlation with 0.25 to 0.05 mm and more than 0.001 mm microaggregates,also had positive correlation with less than 0.001 mm microaggates.But the soil texture of lower layers(20 to 60 cm) were relevant to the parent material and little affected by human beings activities.There existed significant positive correlation among three fractal dimensions(
P
<0.05),also had negative correlation between soil organic matter and fractal dimensions(
P
<0.05).The fractal dimension could be one of the indices of soil quantity evaluation.The fractal theory was also considered as a new tool to research on the soil structure and features.
2008 Vol. 6 (2): 75-82 [
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1730
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1171
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83
CHENG Dong-Bing-；Li-Chao-Xia-；Ca-Chong-Fa-；Bang-Yan-Beng
Effects of contour hedgerow on soil physical properties in the Three gorges reservoir area
Contour hedgerow is a very common and effective technique around the world,which is employed to revegetate on cultivated slope land and conserve water and soil resources.Contour hedgerow is considered an effective way of sustainable development of agroecosystem in the Three gorges reservoir area.Alluvial soils in front of hedges(
Leucaena leucocephala
and
Vitex negundo
) were taken as the objects,to evaluate the effects on soil water and physical properties from different distances to hedgerows(ridge) at different soil depths by contour hedgerow agriculture compound planting on slope land.The results showed that non-capillary porosity of soil,saturated hydraulic conductivity,saturated water content and natural water content in the hedgerows treatments were higher than in the rocky ridge terrace treatment,while the soil bulk density and field capacity in the hedgerows treatments were lower than in the rocky ridge terrace treatment,which reflected that the effects on water and soil conservation by hedgerows are significant,especially in the top and second layer.Based on the same depth, with the extending of the distance to hedgerows(ridge),in the hedgerows treatments soil bulk density and natural water content increased gradually,and noncapillary porosity of soil,saturated hydraulic conductivity and saturated water content decreased gradually,while no apparent change in the rocky ridge terrace treatment.With the deepening of the soil layer,in each treatment soil bulk density and natural water content increased gradually,and non-capillary porosity of soil,saturated hydraulic conductivity and saturated water content decreased gradually accordingly,and their differences among treatments were also lessened gradually.The distance to hedgerow(ridge) reflected the degree of effects on soil water and physical properties by hedgerow indirectly.The closer to hedgerow is,the greater the effects are.Comparing treatments of Leucaena leucocephala and Vitex negundo,their effects were equivalent.
2008 Vol. 6 (2): 83-89 [
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1757
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90
LI Xin-；Jiang-Pei-Fu-；Wu-Yang-；Sun-Chu-Yun-；Lei-Ting-Wu-；Yuan-Jian-Beng-；Zhang-Xiao
Influences of water harvesting with subsoiling on the growth of <i>Caragana korshinskii</i> Kom. in the arid grassland
In order to solve the problem about the inefficiency of rainwater utilization in the pasturing area of North China,a field experiment was conducted for subsoiling in the
Caragana korshinskii
Kom.field to form the linear channel to increase the rain water use efficiency;and lopping for
Caragana korshinskii
Kom.in dry season to decrease the ET.The results indicated that the bulk density of soil had decreased after subsoiling,the average decrease was 0.21 g/cm
3
.Compared with no-subsoiling treatment,the height and breadth of
Caragana korshinskii
Kom.was improved 45.54% and 30.71% each;the rainwater use efficiency was increased too.The
Caragana korshinskii
kom.that was lopped grew faster than the contrast treatment,the height was enhanced 31.15% and breadth was enhanced 32.32%.The
Caragana korshinskii
Kom.'s height and breadth were close between the two treatments by the end of experiments.The result provided some references for grassland to improve the environment.
2008 Vol. 6 (2): 90-94 [
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1462
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1253
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95
LIU Jiang-Hua-；Li-De-Wu-；Liu-Guo-Ban-；Li-Xiao-Li-；Hou-Xi-Lu
Traits of water ecotypes and life-form spectrum of vegetation under canopy of
Robinia pseudoacacia
forests
Robinia pseudoacacia
is one of the main tree species for afforestation on Loess Plateau.To gian a better understanding of the impacts that
Robinia pseudoacacia
do to undergrowth,we investigated species components,water ecotypes and life-form spectrum of vegetation under Robinia pseudoacacia forest stands with different age in forest-steppe zone on Loess Plateau.We learned that,although
Robinia pseudoacacia
over-consumed soil water and soil tend to dry, vegetation changed from xeromorphic to mesophyte vegetation,and vegetation succession under
Robinia pseudoacacia
canopy had a similar process to natural succession on abandoned farmlands.From species components,it had no xeromorphic trend.Different from succession series on abandoned farmland,Bothriochloa ischaemum,as a constructive species in native plant communities,didn't become dominant species in all plots.Along with age growth,two distinct synusias emerged under
Robinia pseudoacacia
canopy.One was the Chamaephytes synusias dominated by vermuth suffruticose such as Artemisia gmelinii,and the other was the Hemicryptophytes synusias dominated by perennial gramineous hemicryptophyte such as Stipa bungeana.It is concluded that natural succession of undergrowth was not fundamentally changed by the growth of
Robinia pseudoacacia
.It was feasible to select
Robinia pseudoacacia
as a pioneer tree specie to restore vegetation in local region.
2008 Vol. 6 (2): 95-99 [
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1639
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3501KB] (
1246
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100
LEI Xiao-Jie-；Li-Rui-；Zhang-Ke-Bin
Analysis on stability of plant community under different measures of desertification control in Yanchi County,Ningxia
Taking
α
-diversity index(including Shannon-Wiener index,Simpson index,
J
sw
,and
J
s
which are community evenness indces) and
β
-diversity index(measured by similarity coefficients),biomass change coefficient as targets this article analyze the stability of plant community under different measures of desertification control in Yanchi County,Ningxia from two criteria about
S
p
ace and time.The result indicated: Analyzing based on
α
-diversity and stability,the plant diversity index and community evenness index of the measure by converting cropland to forests are highest,the change of the indces of the measure about artificial fencing during years is slightest;analyzing from
β
-diversity and stability,the plant community similarity coefficients of the measure with artificial fencing are highest and the change during years is slightest,so,the plant community is stablest and the stability by converting cropland to forests is inferior to it.Analyzing based on function target,the biomass of years with artificial fencing is biggest,and the change of the biomass by converting cropland to forests is slightest.
2008 Vol. 6 (2): 100-106 [
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1390
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3417KB] (
1292
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107
CHENG Fei-；Xu-Xiang-Zhou-；Gao-Ji-Hui-；Xue-Yan-Ni
Advance of research on the rainfall simulators for soil erosion
Rainfall simulation is widely used for the experimental study on soil and water conservation.This paper reviews the characteristics,application,and prospect of rainfall simulator.The simulators could be divided into two main groups: the non-pressurised rainfall simulators,including the thread droppers and the needle droppers with drop formers primarily made of wool fibres or hypodermic needles,and the pressurised water rainfall simulators,including the spout and the sprayer,of which raindrops sprayed out of a row of spouts on the pipe or a nozzle under pressure.The former could be hardly found at present due to its drawback that the minimum size of drop produced is far larger and more even than most natural rainfall and the simulator could not easily generate rains with the similar energy to the natural one.Rainfall simulation halls with automatic operation and observation systems are booming in these years,but the basic simulators will not be completely replaced in virtue of the cheap price and convenient manipulation.
2008 Vol. 6 (2): 107-112 [
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1531
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1173
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113
WEI San-Beng-；Wang-Li-；Tun-Fa-Qi
Research and application of SVAT models
It is very important for soil-vegetation-atmosphere transfer models(SVAT model) to study the interaction and relationship among precipitation,vegetation water storage,surface water,soil water,and ground water,the process of vegetation water consumption and the regulation of ecological water demand,the feedback mechanism between ecosystem and local climate,the mechanism of reciprocity between vegetation and soil water,and the restoration and rehabilitation of ecological environment.SVAT models have been improved from single canopy models to double canopies or multiple canopies models through 3 stages development of bucket model,biophysics model and biochemistry model for about 50 years.The experts abroad and home have made many kinds of SVAT models based on a great deal of experiments and this models were verified,evaluated and modified in many regions all over the world.This paper summarized the parameterization schemes for main water and heat process,application,researches,comparison,and improvement in parameterization schemes of SVAT models,and put forward some problems to improve and perfect existing SVAT models,mainly including the offsetting of Underlying Surface,the simplification,validation,and comparison about SVAT models.
2008 Vol. 6 (2): 113-120 [
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