【作者】 王振锡；

【导师】 潘存德；

【作者基本信息】 新疆农业大学 ， 草业科学， 2009， 博士

【摘要】 干旱区内陆河流域受损生态系统的恢复与重建是当前社会各界关注的焦点问题,对塔里木河下游荒漠-绿洲过渡带退化生态系统解析与重构研究为今后该区域生态恢复与重建工程的规划设计提供理论依据,具有重要的实践指导意义。本研究以恢复生态学理论为指导,以“退化历史→现状解析→恢复重构”为主线,采用树木年轮生态学、地统计学、数量生态学、遥感与地理信息系统等技术手段与分析方法,通过对塔里木河下游区域水环境历史变迁与生态退化历史、荒漠-绿洲过渡带浅层地下水历史变化与生态退化历史、荒漠-绿洲过渡带生境异质性、荒漠-绿洲过渡带植物群落多样性及过渡带生境与植物群落间关系进行解析,研究提出了荒漠-绿洲过渡带植物群落重构方略。主要研究结果如下:(1)胡杨(Populus euphratica Oliv.)树木年轮反映的塔里木河下游近50a来的区域水环境状况具有多样性和复杂性,并不完全表现为距离下游上段(大西海子水库)越近其水环境状况就越好,不同区域退化进程具有差异性,在生态恢复过程中应以分区治理恢复为宜。20世纪90年代是下游水环境状况最差时期,体现了长达30a断流水环境的变干累积效应,是下游生态系统退化最严重的时期;而20世纪60年代和21世纪初是下游水环境状况最好时期,分别对应了下游常年过水期和生态输水期;突变检测表明下游水环境变化对下游断流时段的突变效应具有滞后性;塔里木河下游区域水环境干湿变迁是地表径流的多寡,离流域上段(大西海子水库)、古河道、现有输水河道距离的远近,微地貌以及地质构造所决定的区域地下水构成等多方面因素共同作用的结果。(2)基于刚毛柽柳(Tamarix hispida Willd.)树木年轮重建的过渡带近50a来浅层地下水埋深序列和1972～2005年NDVI指数变化分级特征分析共同表明,荒漠-绿洲过渡带自上世纪50年代末至90年代,区域生态表现为逐年退化趋势,2000年生态输水后,区域生态初步恢复。过渡带柽柳年轮宽度指数与英苏3～6月浅层地下水埋深负相关显著(R=-0.917,p<0.01),具有明确的树木生理学意义;利用逐步回归分析,重建英苏近50a来3～6月浅层地下水埋深,延长了区域浅层地下水埋深水文记录达42a;重建序列趋势分析表明,1958～2000年英苏浅层地下水埋深序列呈波段增加趋势,20世纪50年代埋深最浅,20世纪90年代埋深最深;突变检测结果显示重建序列对下游断流、生态输水响应强烈。处于极端干旱区的荒漠-绿洲过渡带生态退化进程与区域浅层地下水为主导的水环境变迁以及NDVI指数反映的植被退化过程具有良好的同步性。(3)荒漠-绿洲过渡带现状生境在垂直梯度和水平梯度总体上均表现出空间自相关范围小,空间变异性强,受结构性因素影响大的特征,由于受河岸水文过程的影响,在整体规律性变化基础上都存在明显地局部性变异,这种局部性变异在靠近河道的区域表现更显著。在0～200cm的垂直梯度上,荒漠-绿洲过渡带土壤盐分和养分指标随土层深度的增加而表现为逐渐降低规律,pH值、CO32-和土壤含水量则相反;40～60cm土层是过渡带土壤理化性质垂直变异的突变层次,其在水平梯度上具有很强的空间变异性,空间自相关特性明显;对过渡带土壤盐分、土壤养分和土壤水分要素研究采样尺度应分别控制在2400m、4910m和11500m以下。过渡带具有土壤盐分含量高、养分贫乏的特点,但其浅层地下水埋深相对较浅,有利于进一步开展植被恢复与重建。(4)荒漠-绿洲过渡带植物种类少,以旱生耐盐植物为主;植物群落类型单一,可划分为4种类型;植物群落分布破碎,空间异质性强,以柽柳(Tamarix spp.)群落为分布面积最大的优势群落。基于面向对象的植物群落分类结果显示,从绿洲至荒漠方向上,植物群落分布整体上表现为减少的趋势;在河流流向方向上,植被群落分布差异不大;在垂直河道方向上,过渡带植物群落分布呈显著减少趋势,表现出明显的河道效应;0～180cm土层是与植物群落分布相关紧密的土壤层次,为开展植物群落格局与环境因子关系研究的关键层次;过渡带以水盐耦合为主导的环境梯度对植物群落分布格局起主导作用,其中影响显著的环境因子是以电导率、Cl-为代表的土壤盐分因子和土壤养分中的速效K;环境因子总共解释了塔里木河下游荒漠-绿洲过渡带植被分布格局变异的52.08%,其中土壤盐分因子、土壤养分因子、水分因子、空间因子和四者的交互作用分别解释了16.589%、11.104%、9.940%、7.148%和7.247%。在过渡带恢复与重建过程中,应采取分区治理,重点考虑土壤盐分因子。(5)基于“适地适生”原则,使重建群落在相对较短的时间内建立起自维持机制,并达到退化生态系统在当前生境状况下恢复与重建的目的。研究结果表明荒漠-绿洲过渡带植被重构区总面积11119.15hm2,其中:重构柽柳群落区主要位于靠近绿洲区域,面积为2990.18hm2,占重构区总面积26.89%;重构胡杨群落区主要位于输水河道中段和靠近英苏的河道下段,面积最小,为429.80hm2,占重构区总面积3.87%;重构疏叶骆驼刺(Alhagi sparsifolia Shap.)群落区主要位于过渡带中部及南部的大部分区域,面积最大,为7121.21hm2,占重构区总面积64.04%;重构花花柴(Karelinia caspica Less.)群落区主要位于河道上段的沿河区域,面积为577.96hm2,占重构区总面积的5.20%。更多还原

【Abstract】 Ecological restoration and reconstruction of damaged ecosystem becomes more and more concerned issue of the society on continental river basin in arid zone. The results of analysis and reconfiguration of degraded ecosystem provide scientific basis for planning and design of regional ecological restoration and reconstruction project and has important directive significance in desert-oasis ecotone in the lower reaches of Tarim River. On the basis of the theory of restoration ecology, this study took "history-of- degradation→analysis-of-status-quo→reconfiguration-of-vegetation-community" as the main line, explored the regional water environmental change and history of degradation of the lower reaches of Tarim river about 50-year, the change of shallow water table depths about 50-Year and history of degradation in desert-oasis ecotone, described the characteristics of habitat and vegetation community and the relationships between habitat and vegetation community in desert-oasis ecotone, and put forward the strategy of vegetation community reconfiguration for desert-oasis ecotone on the basis of status quo. The methods and technologies of this study included dendroecology, geostatistics, quantitative ecology, remote sensing and geographic information system. The main results showed:(1) The regional water environmental change were various and complicated about 50-year. The water environmental condition did not display completely that the nearer to the upper reaches(Daxihaizi reservoir) the site was, the better its water environmental condition was, reflecting degree of ecology degeneration of different regions in the downstream were not same; The worst periods of water environmental conditions occurred mainly in the 1990s. This phenomenon was attributed to the breaking flow of river downstream for more than 30 years. The best periods of water environmental conditions appeared in the 1960s and at the beginning of this century, and this phenomenon was attributed to perennial water period and eco-water period. The abrupt change examination indicated that the regional water environmental change had the obvious sudden change effect. The regional water environmental change in the lower reaches of Tarim River was determined by quantity of surface flow, distance to the upper reaches (Daxihaizi reservoir), distance to ancient watercourses, distance to the waterring watercourse, micro-topography and pattern of regional shallow water table determined by regional geological structure et al. jointly.(2) The analysis of regional shallow water table depths about 50-year reconstructed by Tamarix hispida Willd. Tree-ring width data and NDVI change classification between 1972 and 2005 both showed that degree of ecology degeneration become gradually serious from 1950 to 1990s, but regional ecology is on the way to preliminary restoration after 2000 because of eco-water transfer in desert-oasis ecotone. There was an obvious relationship between tree-ring widths of Tamarix hispida Willd. and regional shallow water table depths. The analysis result showed that there was the evident negative correlation(-0.917) between the STD tree-ring index and the 3-6 Month shallow water table depths in desert-oasis ecotone in the lower reaches of Tarim River, indicating obvious tree physiology significance. Using the stepwise linear regression models, the 3-6 Month shallow water table depths about 50-year in desert-oasis ecotone was reconstructed. Method of“Leave-one-out”was used to estimate stability of regression function based on statistics between the observed and estimated series, the result of reconstruction lengthened hydrology records of regional shallow water table to reach 42a. For the series of the construction, there was the rise trend in regional shallow water table depths from 1958 to 2000. Furthermore, the shallowest periods of shallow water table depths appeared in the 1950s, and that the deepest periods occurred mainly in the 1990s. The abrupt change examination indicated the reconstruction series had obvious response to the breaking flow of river downstream and eco-water transfer. The results showed the course of ecology degeneration had obvious synchrony with regional water environmental change determinated by shallow water table depths and the course of vegetation degeneration reflected by change of NDVI index in desert-oasis ecotone. (3) Environmental factors had obvious spatial heterogeneity; spatial autocorrelation was distinct both in vertical gradients and in level gradient in desert-oasis ecotone. Along and across the direction of the river water flowing and along the direction of the oasis to desert, all the soil elements were characterized by the partial variation on the basis of the whole regularity variation.And this partial variation was clearer across the direction of the river water flowing.The analysis of habitat heterogeneity showed that soil salinity and soil nutrient in 0～200cm soil depths in ecotone had decreasing trend with the increasing of the soil depth, while the change trend of pH, CO32- and soil moisture content were opposite. There is distinctly different between 0-60cm soil depths and 60-200cm soil depths as for soil factors, 40-60cm soil depths was the abrupt layer of soil physical and chemical properties in ecotone. Soil physical and chemical properties of 0-60cm soil depths in level gradient had obvious spatial heterogeneity, spatial autocorrelation was distinct. The max range of soil salinity, soil nutrient and soil moisture content were 2390m, 4906m and 11430m. The changing range of all indexes of the soil offers a reference for future study how to locate the points for collecting the soil samples.The soil salinity was higher and the soil nutrient was lower in ecotone, but shallow water table depths was lower and was in favor of vegetation restoration and reconstruction; the simulation of the soil elements spatial distribution can offer the information of habitat pattern in every point of study area for restoring regional vegetation.(4) The analysis about diversity of vegetation community showed that plant species was seldom. Eighteen species belong to nine family and seventeen groups existed in the study area. Type of vegetation community was unitary, classified into four types; Based on the result of object-based classification, distribution of vegetation community was broken, significantly, strong spatial heterogeneity, the size of Tamarix spp. Community was the largest in ecotone. Along the direction of the oasis to desert, distribution of vegetation community was decreased; along the direction of the river water flowing, there was little difference; across the direction of the watercourse, distribution of vegetation community was distinctly decreased in ecotone. The 0-180cm soil layer was closely related with plant community distribution patterns in desert-oasis ecotone. The environmental gradient of coupling relationship between water and salt played the most important role in the forming of community distribution pattern or species abundances variation in the communities. Conduct and Cl- in soil salt variables and available K in soil nutrient variables were the significant factors in all environmental factors. The total contribution rates of the environmental factors were 52.08%, the contribution rates of soil salt factors, soil nutrient factors, water factors and special factors were 16.589%,11.104%,9.940%,7.148%and 7.247%, respectively. From a management standpoint, it is most important to adopt corresponding ways according to the difference of soil salt in different region, and keep dynamic balance of water and salt in the process of restoration of damaged ecosystem in desert-oasis ecotone in the lower reaches of Tarim River.(5) Reconfiguration of vegetation community on the basis of habitat status is useful to build self-sustained mechanism of vegetation community in a short time. The reconfiguration not noly gives an indication in choosing the most appropriate community types in the process of restoration of damaged ecosystem in desert-oasis ecotone, but also fully embodies the corresponding environmental characteristics of different community types. The results of reconfiguration of vegetation community indicated that Tamarix spp. community reconfigured was located near oasis, its area was 2990.18hm2 and occupied 26.89% in whole vegetation loss zones; Populus euphratica Oliv. community reconfigured was located at the middle of watercourses and the lower of watercourses near Yengisu, its area was least, 429.80hm2 and occupied 3.87% in whole vegetation loss zones; Alhagi sparsifolia Shap. community reconfigured was located at the middle of ecotone and most of northern region, its area was largest, 7121.21hm2 and occupied 64.04%in whole vegetation loss zones; Karelinia caspica Less. community reconfigured was located at the upper of watercourses region, its area was largest, 577.96hm2 and occupied 5.20% in whole vegetation loss zones.更多还原