伊犁河三角洲景观结构的影响机制研究

Influence mechanism of landscape structure in River Ili delta

在遥感和水文数据的支持下,根据伊犁河三角洲作为典型的中亚干旱区内陆河流域尾闾区域特点,确定了伊犁河三角洲的景观分类系统。通过采用景观结构梯度分析法、景观干扰度指数和景观Kappa指数等方法,系统地分析了近32a(1975-2007)伊犁河三角洲景观结构的时空演变特征,并对景观结构的影响机制做了充分地探讨。结果表明:(1)沿着一定的地形梯度和水文梯度,伊犁河三角洲流域景观表现出特殊的纵向结构、横向结构的梯度特征和景观内部特征,与地表水直接关联的景观类型表现尤为明显,如湖泊、沼泽、漫滩。(2)在人为活动和自然环境的双重影响下,近32 a伊犁河三角洲景观结构的空间变化具有一定的周期性和不稳定性,主要体现为景观类型面积和空间位置的变化,其中以湿地景观类型的变化最为显著。(3)生态干扰对景观结构的影响因景观类型的不同存在显著的差异性和时空变异性,以湖泊和沼泽受干扰作用最为明显。高、中、低三种干扰强度区域的空间分布及面积变化同样具有一定的周期性和不稳定性。(4)水利工程建设和自然环境是影响伊犁河三角洲景观结构的主要驱动力。水利工程对伊犁河的拦蓄引起景观结构变化的作用最为深远,它通过改变三角洲上游的水文情势直接影响整个区域的景观结构。而自然环境因素中的地形和水文条件主要影响湿地景观类型的时空分布,气候因子则直接影响河川径流量。

Since the Ili River delta of Kazakhstan has experienced less human direct disturbances during 1975 - 2007, it is suitably regarded as a case to analyze landscape pattern changes and its driving mechanism for under- standing the importance of spatial ecological dynamics and maintaining sustainable development in unique wetland ecosystems of arid central Asia. In the study, two types of data were used ： （ 1 ） hydrological data, fluvial runoff volume from Ill River （ 1953 -2007） and water levels of Lake Balkhash in the last 54 years （ 1953 -2006）, and （2） land cover maps extracted from Landsat images in 1975, 1990, 2000, and 2007. Arid area in Central Asia, the classification system of landscape was established based on the land-cover maps of River Ili delta. Using the methods of landscape structure gradient of analysis, landscape disturbance index and Kappa index, the change of landscape structure from 1975 to 2007 was analyzed and the driving mechanism of landscape structure was dis-cussed. River Ili delta displays special characteristics of landscape in the horizontal structure, vertical structure and internal structure along the topographic gradient and hydrological gradient in the watershed, particularly the land- scape types related to water, such as lake, swamp, and flood land. Under the influence of human activities and cli- matic change, the spatial change in the landscape structure show a certain periodicity and instability in the late 32 years. The spatial change in vertical structure of landscape is generally influenced by corridor width and length as well as the change in landscape types; the spatial change in horizontal structure is characterized by landscape fragmentation, which resuhs in reduction in landscape connectivity. Effect of disturbance on landscape structure shows the distinct differences and temporal-spatial variability with different landscape types, in which lake and marsh are most easy to be disturbed. The change in spatial distribution and area of high, medium and low disturb- ance intensity presents periodicity and instability. Natural factors generally influence the complexity of inner struc- ture of landscape, and anthropogenic factors affect the connectivity in the vertical and horizontal structure of land- scape and diversity of inner landscape structure. The dominant driving forces of landscape structure in River Ili del- ta include a huge reservoir construction in the upstream of river and natural conditions. The interception of reservoir to River Ili has a profound impact on landscape structure and directly changes hydrological condition and landscape structure in the delta. Due to inherent characteristics of the lakes and river, the water level changes in Lake Balkhash and the wetland landscape patterns in Ili River delta were inconsistent, the former generally lagged behind the latter. This also influences the wetland landscape structure, which will be a research topic in the future.