Near-natural Assessment System And Its Application In Near-natural Control Of Stream Ecosystems In The Suburb Of Beijing

Stream is the area human activities concentrated on,its components include stream channel, wetland,riparian and other influenced terrestrial habitats.As the basic constituent unit of terrestrial aquatic ecosystem,stream prefers to these small flowing water body belonging to the first or second grade river and having limited watershed area,which is usually between 10 km~2 and 100km~2.For the unreasonable utilization and exploitation ago,stream ecosystem in the suburb of Beijing has suffered seriously disturbed.Therefore,this study offered stream near-natural assessment and control system,which is base on different degraded stream reaches,it used the corresponding near-natural control measurements to restore natural ecological functions and landscape values of stream ecosystem,and their environmental effects were monitored also.All of these try to make up the breakages of artificial unreasonable utilizations on stream ecosystem and can offer important suggestions to the sustainable utilizations and suitable explorations of stream resources.Firstly,according to the yearly changes of papers whose keywords include stream and recorded in SCI database and CNKI database,it can get that the number of international published papers related stream shows increasing trend from 79 papers of 1998 to 159 papers of 2007,the increasing range is high to 200 percent;and in China,the number of papers related stream shows the similar increasing trend from only 1 papers of 1980 to 3002 papers of 2008;and the number of Chinese normal published doctor papers also increased from 2 ones of 1999 to 92 ones of 2006,the increasing range is high to 46 times; and the number of Chinese normal published master papers also increased greatly,from none papers of 1999 to 475 papers of 2007,the average yearly increasing number is 68.All of these data shows stream ecosystem researches have become hot spots at home and abroad.Stream near-natural ecological assessment system in the suburb of Beijing which is constructed in this study base on lots of data from the field investigation,and according to the scientific,target,systematic,independence and operability principles,twenty-two quantitative indicators and thirteen qualitative indicators from ecological,hydrological and geographical aspects were adopted.The assessment system compares the natural conditions of the investigated stream to be reference sites,and evaluates the near-natural degree of structure and functions of degraded stream ecosystems which is disturbed by human activities or sudden natural changes.And the method of combining expert scoring and analytic hierarchy process(AHP) is used to decide the weights of assessment indicators,and fuzzy mathematics is used to build this assessment system for the randomness during field investigation.The assessing procedure includes the qualitative assessment and the quantitative assessment.If the results of the qualitative and quantitative assessments are different near-natural degrees,while,the assessed stream ecosystem is in the transition belt among two degrees.The majority of quantitative indicators are represented by ratios in order to avoid the problems with the variety of stream ecosystem. The near-natural degrees of stream ecosystems can be classified into four grades:(ⅰ) natural grade(no human disturbance);(ⅱ) near-natural grade(minimal artificial disturbance);(ⅲ) semi-degraded grade(serious artificial disturbance);(ⅳ) complete degraded by human activities,Besides,three transition belts among the four near-natural degrees in order to reflect the dynamic changes.And Hualjiuhe River which is part of the water conservation district of Hualrou Reservoir is to be seemed as the pilot study.The qualitative near-natural assessment result of the pilot reach showed that it was in the degraded natural degree(the membership grade is 0.5637),and the same as the quantitative assessment result(the membership grade is 0.3112).Therefore,the whole ecological situation of the pilot reach is in the degraded natural degree.And the following clustering verification of seventeen reaches of Huaijiuhe River has been made,the two kind of results show the highly similar classification,which offers the scientific references to its population.Pearson's correlated analysis was used to optimize the above assessment system in the next step,six comparable natural or near-natural ones were selected,and sixteen typical benthic macroinvertebrate indexes and biodiversities and nine related habitat environmental indicators of seventeen samplings was collected.And the Pearson's correlated analysis was used to remove indicators having high correlation among the sixteen candidate biological indicators and nine candidate environmental indicators.Finally,five biological metrics including percentage of Diptera,percentage of Ephemeria,percentage of Collectors, percentage of the first dominant taxa and Margalef Species Richness index were chosen to compose the framework of ecological assessment of small water bodies in the suburb of Beijing with three environmental indicator including NH3-N,water velocity and water depth from water quality,geographical and ecological aspects.The canonical correspondence analysis(CCA) results demonstrated that the chosen three environmental indicators can explain 60%of the changes happened in benthic macroinvertebrate communities and biodiversities of investigated six small water bodies,which satisfies the basic requirements of this research.In order to popularize this assessment system,some methods and measurements of decision support system(DSS) were produced,this paper use VB language to develop stream environmental decision support system(SEDSS) on the Microsoft Visual Studio 2005.net framework.This system includes quantitative and qualitative interfaces,two interfaces can individually operate,and the ecological, hydrological and geographical sections of the two interfaces can fold in order to conveniently enter data.Stream near natural control measurements need to consider the geographical and hydrological characters,vegetation growing situation,prices of technique materials,the difficulty of construction and so on,and during their construction procedure,it need they cause the least effect and disturb on stream ecosystem.They should follow five principles including①poring trend of surface;②low trend of high dam;③graded trend of slope;④natural trend of materials;⑤economic trend of execution.According to different construction parts,this study divides stream near natural control measurements into stream channel near natural control measurements and stream slope near natural control measurements.Besides introducing detailed building methods and ecological functions of all kinds of control measurements,graphic works and figures at crime scene of these control measurements are still used to add instruction,which is in order to offer scientific references to stream near natural control in the suburb of Beijing.Stream near natural control measurements can affect environmental conditions of stream habitats through regulating and accelerating healthy restoration procedure of stream ecosystem.In order to comparably analyze the environmental effects of stream near natural control measurements,this research chose three reaches whose ecosystem are in different degree on Huaijiuhe river in the suburb of Peking.From the upper reach to the lower reach the first one is Tuanquan reach which is mostly in natural condition and nearly have not been managed,the second one is the key one,called Siduhe reach,it has been managed by near-natural control measurements for two years,the last one is Yiduhe reach,this reach have been managed by classical engineering control measurements.The monitoring content includes relative humidity,air temperature,and soil temperature and plant diversity. The results of this research showed that①stream near-natural control measurements increase air relative humidity of stream environment,because the water surface relative humidity of Siduhe reach is five percent higher than the one of Yiduhe reach,at the same time,the land surface relative humidity is ten percent higher,and although the land surface relative humidity of Siduhe reach is lower than natural Tuanquan reach,its water relative humidity is two percent higher than Tuanquan reach.②compared with the classical engineering measurements,stream near-natural control measurements can decrease the air temperature of surrounding environment,meanwhile,regulate the temperature different between riparian and water,the temperature difference of Siduhe reach is 0.5℃,which is only one third of Yiduhe reach.③stream near-natural control measurements also can shorten the temperature difference among different soil layers through restoring the vegetation of riparian,and regulate the temperature of soil layer,keep the soil moisture of deep soil layers.④the plant diversity of Siduhe reach which has been managed by near-natural control measurements is three times higher than Yiduhe reach,therefore,we can say near-natural control measurements can keep and restore plant diversity of riparian. Finally,the investigation results of payment willingness of people on stream near natural control show that majority of local residents have lower satisfaction on current situation of stream management in Beijing,and 84.1%of investigated people mark less than 70(the total mark is 100).Especially,the effects of stream near natural control measurements in recent years didn't get the self-identity of residents,only 27.4%of the investigated people think these stream near natural control measurements achieve some effects,36.2%of the people forgive their choice,and 26.3%of the people consider these control measurements have no effects.And the results of the investigation on the detailed stream near natural measurements show that 98.4%of the investigated people certificate the effect of al kinds of ecological measurements.All the investigated people will to contribute their strength and 68.7%of the investigated home will to pay for stream near natural control,in detail,41 people chose to donate by themselves(32.8%);36 people chose to buy environmental bonds(28.8%);54 people chose to buy environmental lottery(43.2%);12 people chose to pay environmental tax(9.6%);and 14 people chose to pay water accounts(11.2%).