Ruchun ZHANG,Zhenhua ZHENG,Jianjun CUI,Tao ZHANG

Institute of Geographical Science,Hebei Academy of Sciences,Shijiazhuang 050021,China

Since establishment of China,after 1958 in particular,lots of reservoirs,middle or large scales,have been built along large rivers and seas as well as tributaries,playing key roles in flood control,regulation,electricity generation and shipping.

Hutuo River,situated in Gangnan Reservoir and Huangbizhuang Reservoir,has a semihumid and semiarid climate,where dams and reservoirs are constructed in upper reaches,preventing most runoffs.Consequently,groundwater table declines and natural plants go degradation,affecting river ecosystem structure.In order to explore vegetation changes in lower reaches of reservoirs and analyze water change on vegetation distribution,the research performed comparisons and surveys of vegetations on two sides of Hutuo River course and proposed practical measures for vegetation restoration,providing scientific references for ecosystem restoration and reconstruction of vegetations in lower reaches.

Research Area

Originating in eastern area of FanzhiCounty, ShanxiProvince,Hutuo River flows through Xinding Basin,along Wutai Mountain,and through Taihang Mountain and it empties into the Fuyang River.At the estimated length of 566 km,it is one of large tributaries of Ziya River.Located in middle reaches of Hutuo River,Gangnan Reservoir was constructed in 1958-1961 and improved in 1966,and its total basin area is about 15 900 km2,representing 68% of Hutuo River basin area.Besides,it provides a capacity of 157.1 million m3,with a maximum height of 63.19 m.In general,it is a large water conservancy project dominated by flood control,supplemented by water supply,irrigation,and hydroelectricity[1].Huangbizhuang Reservoir is situated nearby Huangbizhuang Town,Luquan City,Hebei Province,28 km away from Gangnan Reservoir and 30 km from Shijiazhuang City,with a total capacity of 1 210 million m3,functioning well in flood control,as well as irrigation,wa-ter supply,and hydroelectricity.To gether with Gangnan Reservoir,it controls about 23 400 km2,taking up to 95% of Hutuo River[2-4].

Research Method

The research selected natural plants in typical areas and surveyed 2-3 sample sites according to vegetation distribution.Specficially,10 samples(1m×1m)were chosen randomly from every plot in order to investigate planttype,abundance,coverage,number and average height.

In the research,Gleason index(I)representing species abundance and Simpson index (Ds)representing species diversity[5]were selected to perform analysis on plant diversity in lower reaches.Assuming,

whereNrepresents total number of individuals in a community;Srefers to the number of species;nirefers to the number of individual of theithspecies.The higher the value,the higher the diversity.Besides,Gleason index isI=S/lnA,whereSrefers to the number of plant species,andArefers to quadrat area.The higher the value,the better species diverisity.

Arrangement of Sample Plot

As shown in Table 1,2-3 sample plots were arranged in upper reaches of Gangnan Reservoir, Huangbizhuang Reservoir,and the area between the reservoirs.Furthermore,10 quadrats were investigated from every sample plot and concluded to obtain vegetation growth.

Results and Analysis

Survey results of vegetation The distribution of vegetation in different sample plots

The upper reaches of Gangnan ReservoirIn sample plot 1,total vegetation coverage reached 95%,involvingArtemisia argyiof 35%,Triarrherca saccharifloraof 20%,Phragmites australisof 15%,Setaria viridisof 5%,Digitaria sanguinalisof 5%,Polygonum hydropiperof 5%,Typha orientalisof 5%,and coverage ofConyzacanadensis,Abutilon theophrasti,Bidens pilosa,Leonurus artemisia,Hydrilla verticillata,Lemna minor,Physalis alkekengi,Eleusine indica,Equisetum arvense and Miscanthus sinensistotaled below 5%.

In sample plot 2,total vegetation coveragereached90%,involvingCyperus glomeratusof 25%,Artemisia sacrorumof 20%,Amaranthus tricolorof 15%,Phragmites australisof 15%,Polygonumhydropiperof 5% ,Artemisia argyiof 5%,and coverage ofSetaria viridis,Chloris virgata,Digitaria sanguinalis,Echinochloacrusgalli,Calystegia hederacea,Nasturtium officinale,FimbristylisstauntoniiandAster subulatusreached below 5%.

The area between Gangnan and Huangbizhuang ReservoirsIn sample plot 3,total coverage rate reached 80%,involvingBidens tripartitaof 40%,Setaria viridisof 25%,Artemisia lavandulaefoliaof 10%,and coverage ofInula japonica,Xanthium sibiricum,Acalypha australis,Aster subulatusandEragrostis pilosakept below 5%.

In sample plot 4,coverage rate reached almost 100%,dominated by Gramineae,involvingIsachne globosaof 60%,Phragmites australisof 20%,Artemisia capillariesof 10%,Bidens pilosaof 5%,and coverage ofInula japonica,Plantagoasiatica,Alisma plantago-aquatica,Potamogeton perfoliatus,Ceratophyllumdemersum,Sonchusbrachyotus,Amethystea coerulea, andPennisetum alopecuroidesmaintained below 5%.

Lower reaches of Haungbizhuang ReservoirIn sample plot 5,total vegetation coverage reached 90%,involvingImperata cylindricaof 55% andSetaria viridisof 30%,and coverage ofAmaranthus tricolor,Salsola collina,Digitaria sanguinalis,Xanthium sibiricum,Chloris virgata,andChenopodium serotinumtotaled below 5%.

In sample plot 6,total coverage achieved as high as 95%,involvingDigitaria sanguinalisof 50%,Setaria viridisof 20%,Imperata cylindricaof10%,Artemisia capillariesof 10%,and coverage ofCorydalis edulis,Salsola collina,Chloris virgataandEleusine indicatotaled beolow 5%.

Table 1 Conditions of sample plots in lower reaches of Gangnan-Huangbizhuang Reservoirs

Table 2 Species diversity index and richness index of each sample site

In sample plot 7,vegetation coverage reached 95%,Setaria viridisof 70%,Chenopodium albumof 10%,Eleusine indicaof 5%,and the coverage ofDatura stramonium,Humulus japonicus,Imperata cylindricaandCrperusglomeratuskept below 5%.

Changes of plant speciesIt is surveyed that the research area totaling has 51 herbaceous plants in 45 genera of 22 families,including 9 species of aquatic plants,6 species of hygrophytes and 36 species of mesophyte or xerophytes.There were over 15 sampled plants in upper reaches of Gangnan Reservoir;11 and 14 plant species from banks between Gangnan andHuangbizhuangReservoirs.In downstream of Huangbizhuang Reservoir,below 10 plantspecies were collected.

As shown in Table 1,Anthropochory plant proportion[6]tended to be volatile upon areas,including 27.2% in upper reaches of Gangnan Reservoir,36.0% between Gangnan and Huangbizhuang Reservoir,and 80.2% in down stream of Huangbizhuang Reservoir.

Species diversity and richnessAs shown in Table 2,average diversity index and average richness index differed significantly in different typical areas,and the value of number kept decreasing from upstream to downstream.

Renovation Countermeasures of Plants

Recovering of wetland area

To restore wetland area in Hutuo River lays foundation for vegetation eco-restoration.Besides,it is necessary to convert farmlands to wetlands to increase wetland area,which enhances regulation and storage capacity of reservoirs and improves eco-environment and semi-climate.What’s more,to keep farmlands away from wetlands would significantly reduce human interference on watercourse and restore vegetations in banks of watercourse.

Constructing artificial water landscape

Urban water landscape can be constructed on basis of the landscapes of Hutuo River in Shijiazhuang.Specifically,with flood pathway,the water landscape can be constructed,covering,water,dam,road,bridge,island,vegetation,landscape and residential buildings and ornamental plants can be planted along watercourses,such as Iris wilsonii,Lythrum salicaria andNymphaea albaand the banks can be grown withSalix babylonica,Cosmos bipinnataandRosa chinensis,which is effective in restoring watercourse ecology and improving urban eco-environment.

Forests construction along Hutuo River

It is recommend to build closed greenbelts with width of 50-100 m in or out of river levees in down stream of Hutuo River with flood diversion guaranteed,to formulate a framework of eco-environment modification of Hutuo River.

Reinforcement on comprehensive management of watercourse

According to China Watercourse Management Rules,irrational reclamation,digging (dinas and herbs),grazing,piling of construction,domestic,industrial and medical wastes,industrial and sanitary sewages should be inhibited to improve eco-environment and advance sustainable use of rivers.

Analysis and Discussion

Generally speaking,vegetation coverage tends to be volatile upon regions in the range of 80% -100%.However,the vegetation species differs in differentregions and the species number is decreasing as the distance with Hutuo River is growing.Besides,the number of vegetation species is more in the sites with water,because of environment diversity.Additionally,natural environment is deteriorating in terms of water and soil when the distance with upper reaches area is increasing,which is a cause of differed vegetation constituents.

In the sampling sites,Anthropochory plants are available,includingChloris virgata,Physalis alkekengi,Humulusjaponicus,Eleusineindica,Chenopodium album,Setaria viridis,Chenopodiumserotinum,Sonchus brachyotus,Calystegiahederacea,Xanthiumsibiricum,Echinochloacrusgalli,Digitariasanguinalis,Plantago asiatica,Acalypha australis,andInula japonica,which indicates human effects on plant’s existent environment.What’s more,Anthropochory plants keep increasing from upper reaches to down reaches,and even dominates in some sampling sites,because villages and farmlands are distributed in river banks.

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