【作者】 李瑞；

【导师】 王百田； 张克斌；

【作者基本信息】 北京林业大学 ， 生态环境工程， 2008， 博士

【摘要】 北方农牧交错带是我国北方半湿润农区与干旱、半干旱牧区接壤的过渡交汇地带,也是将我国农业区与草原牧区分割开来的半农半牧、时农时牧交替变化的地域。北方农牧交错带地理位置独特,生态环境脆弱。近年来,由于生态环境恶化、草地资源大面积遭到人为破坏而导致土地荒漠化和大量贫困人口产生。因此,对北方农牧交错带植被动态学的研究有着重要的生态学意义和现实意义。本文以地处北方农牧交错带的宁夏盐池为例,从植物种群、植被群落及景观等3个不同尺度对北方农牧交错带草地植被的动态特征进行研究。种群和群落尺度上的研究主要以不同生境类型、不同植被恢复措施进行样地布设。根据样地生境梯度,分别采用样方法和样线法进行植被和土壤调查,调查时间为每年的6～8月,时间跨度为2002～2006年,共5年。采用TWINSPAN双向指示种分类法和DCA除趋势对应分析法及种群、群落指标分析法等,结合WinTWINS、CANNCO、Biodiversity Pro、SPSS13.0等生态学、统计学软件对外业资料进行处理分析,在此基础上对北方农牧交错带草地植被群落、植物种群现状及动态特征进行系统的研究;景观尺度(即宏观尺度)上采用归一化植被指数(NDVI)对研究区植被景观2002—2005年动态特征进行分析,同时结合了研究区2002—2005年的气象资料和相应的NDVI均值进行相关分析,探讨影响北方农牧交错带植被动态的主要气象因子。此外,群落边缘效应作为一种特殊的植被动态类型本文也进行了讨论。研究表明,种群、群落以及景观三个不同尺度的研究均表明盐池县2003年植被生长状况是近年来最好的一年,2005、2006年相对较差。主要初步研究结果如下;(1)群落分类结果将研究区草地植被主要划分为3个植被型,21个群丛类型。3个植被型分别为草原植被、草甸植被和沼泽植被。草原植被分布范围广泛,是盐池县主要的植被类型;草甸植被主要分布在低洼地、湿地—草原的过渡带等水热条件较好的区域;沼泽植被主要分布在沼泽湿地;土壤水分状况,全N、速K是影响区域群落分布格局的主要环境因子。此外,放牧等人为干扰及不同植被恢复措施对植被分布格局也有一定的影响。(2)种群波动研究表明;2002—2006年,研究区种群动态主要有4种形式;一是波动式上升,代表种群为黑沙蒿;二是波动式下降,代表植物为白草;三是较为稳定的种群,代表种群为老瓜头和苦豆子;第四种波动形式是气候波动型,主要以一年生草本植物为代表,受调查前期降水等影响较大。研究区主要植物种群2002—2006年格局均多呈聚集分布,聚集度受降水等气象因子影响较大。(3)本文在生态学及统计学的意义下,结合北方农牧交错带草地植被特征,在群落尺度上初步构建了北方农牧交错带草地植被波动测度公式,即;据公式知,2002—2006年,研究区植被波动率分别为0.666、0.685、0.637、-1.098、-0.889。正向波动以2003年的0.685为最大,表明2003年是近年来草地植被生长状况较好的年份;负向波动以2005年-1.098的绝对值为最大,表明2005年是近年来草地植被生长状况较差的一年。(4)群落结构波动特征研究表明;2003年群落各项指标如群落生态优势度、群落均匀性等均最高,表明2003年是近年来盐池县植被生长状况最好的一年;2005年及2006年群落组成结构各项指标均较低,表明2005年和2006年植被状况是近年来较差的年份。(5)不同植被恢复措施群落波动研究结果认为;退耕还草、植被自然恢复、撂荒等措施均起到了有效的植被恢复作用,尤其退耕还草地。不同植被恢复措施2002—2006年群落动态研究还发现,人工封育草地自2000年底封育后2—3年群落各项指标均较高,此后呈现下降趋势,到2006年,封育区植物群落各项指标均是6种不同植被恢复措施中最低的一种。(6)在景观(宏观)尺度上,采用反演模型法对研究区NDVI和生物量进行回归分析,并建立植被生物量反演模型,即;Y=887841NDVI~3-710288NDVI~2+198232NDVI-15935(R=0.809);基于上述反演模型,2002—2005年研究区草地植被生长状况最好的是2003年,最差的是2005年;月平均NDVI值和研究区气象因子的秩相关分析结果表明,研究区草地植被动态的最主要外部因子是降水和气温,其它气象因子如风速等和植被动态无显著关系。(7)湿地—草原群落交错带边缘效应研究发现,湿地—草原交错带除群落均匀度稍小于草原生态系统外,其它群落组成结构指标如群落丰富度指数、群落生态优势度、物种多样性指数、群落均匀度指数均是交错带最大,充分体现了群落交错带的边缘效应。更多还原

【Abstract】 The North Farming-Pastoral Ecotones of China(NFPE)was a transition zone where the semi-humid agriculture area and arid & semi-arid pasturing area meet here.The significances of studying NFPE were as follows;first of all,the geographic position of NFPE was important and the ecological environment was quite fragile; secondly,the ecological environment was deteriorated and the grassland was destroyed,resulting in large numbers of poor people in recent years.Thus,the studies about the vegetation dynamics in NFPE were significant in the meaning of ecology and actuality. This dissertation takes Yanchi County in NFPE as an example to study the characteristic of grassland vegetation dynamic from 3 scales;plant species,community and landscape(RS scale).The sample-plots were distributed according to different measures of vegetation protection and restoration in population and community scales.The quadrat method and sample line approaches were quoted according to the biotope gradient to investigate vegetation and soil in annual June to August,2002-2006. The data was analyzed by the means of TWINSPAN,DCA and indices analyse of species and community by using community classification software WinTWINS,community ordination software CANNCO,biodiversity analysis software Biodiversity Pro and other ecological statistics software.On this base,the present status and dynamic of grassland vegetation community and plant species in NFPE were studied systematically.In the scale of landscape(macroscopic scale),the vegetation dynamic characteristics from the year of 2002 to 2005 were studied by using NDVI.At the same time, correlation analysis between meteorologic data and mean NDVI values had been done to discuss the main meteorologic factors that influence the vegetation dynamic in NFPE.At the same time,as a special vegetation dynamics type,community edge effect was also studied in this dissertation The grassland vegetation dynamics were studied on 3 scales in Yanchi County in NFPE,2002-2006. Results showed that the best vegetation growth was in 2003 and the less vegetation growth was in 2005 & 2006 and the main phasic research findings were as follows; 1)The vegetation in study area was classified into 3 types and 20 associations.The three vegetation types were;grassland vegetation,which distributed widely and was the main vegetation type in Yanchi County; meadow vegetation,which distributed in the wetland-grassland ecotones and low lying land; halophytic marsh vegetation,which was mainly distributed in the wetland zone.Soil moisture content, organic matter,soil salt content,total nitrogen and so on were the main environmental factors which influence the vegetation distribution pattern along the biotope gradient.Also,the microtopography and grazing pressure were the other influencing factors. 2)Population fluctuation study showed that there were 4 dynamic types;fluctuation increase, representative species was Artemisia ordosica; fluctuation decline,representative species was Pennisetum flaccidum; stable community,representative species were Sophora alopecuroides and Cynanchum komarovii; type of climate fluctuation,mainly included annual plant whose growth status was influenced easily by investigation antecedent precipitation.Plant species mainly present gathering distribution from 2002-2006,but gathering degree was different because of species’ biological and ecological characteristic.Otherwise,precipitation,temperature and so on were the other factors influencing populations gathering degree. 3)Based on the meanings of ecology and statistics from community scale,this paper defined the grassland vegetation fluctuation and fluctuation ratio,and built the fluctuation ratio formula as follows; The grassland vegetation quantitative fluctuation and fluctuation ratio in Yanchi,2002-2006 were calculated.Results showed the maximal positive fluctuation ratio was 0.685,meaning a better vegetation growth,which was in 2003.The most negative fluctuation ratio was -1.098,meaning a less vegetation growth,which was in 2005. 4)Community structure fluctuation study showed;all of the values of ecological indices such as community ecological dominance,evenness index and so on were maximal in the year of 2003.In the year of 2005 & 2006,the values of the ecological indices were smaller,especially 2006,the minimum. Thus,the year of 2003 was a better vegetation growth year and 2006,a vegetation less growth year. 5)Community fluctuation of different measures of vegetation protection and restoration showed that nature grassland,rehabilitated fields,abandoned land and so on were effective grassland vegetation restoration measures,especially nature grassland and rehabilitated fields.The study outcomes also discovered that the fenced taming grassland,one of the measures of vegetation restoration was special. After 2-3 years’ fencing cultivation,dominant plant community reinforced their dominant position with some companion species dying out in the competition.Plant characteristic number peaked during this time and descended later.In addition,both plant species diversity and the main plants’ importance value showed the same trend. 6)Based on the regression analysis between NDVI and biomass,the inversion model applicable for NFPE was built up as follows; Y = 887841NDVI~3 - 710288NDVI~2 + 198232NDVI-15935(R=0.809) On this base,the grassland vegetation quantitative attribute in study area from 2002-2005 was studied. Results showed that the vegetation growth status was best in 2003 and worst in 2005.Rank correlation between values of month-mean NDVI and meteorologic factors presented that precipitation and temperature were the main vegetation dynamic influencing factors in NFPE.Other meteorologic factors such as wind etc.had no obvious correlation to grassland vegetation dynamic in NFPE. 7)The study about edge effect of wetland and grassland ectone discovered that all of the ecological induces such as species richness,community ecological dominance and species diversity were maximal in ecotones than in other two vegetation zone(wetland zone & arid grassland zone)excepting the community evenness index.This indicated community ecotones had higher edge effect.更多还原