近30年来深圳河网变化及其生态效应分析

River Network Change and Its Ecological Effects in Shenzhen Region in Recent 30 Years

在地形图、河道普查数据、遥感影像等多源数据支持下,分析了深圳近30年河网的时空变化规律及其与城市化水平的关系,在此基础上通过分析植被盖度、生产有机物质的价值、生态系统服务价值、生态资产等指标的变化规律探讨了深圳观澜河流域河网变化的生态效应。结果表明:(1)近30年深圳市河网结构趋于简单化、主干化,河流支流发展受到较大限制;河网总长度减少355.4km,总条数减少378条,河网密度从0.84km/km2降低到0.65km/km2;以区/街道办驻地为圆心,半径为1-2km的圆环区成为河网萎缩、河网消失的主要区域;依据流域城市化水平和河流主干是否直接入海等2个指标可将深圳市9大流域/水系分为4种不同的河网变化类型;(2)当城市化水平低于30%时,城镇用地扩展与河网萎缩,尤其是河网支流的萎缩存在显著相关;当城市化水平大于30%时,城镇用地扩展对河网的影响较小;(3)2000-2005年观澜河流域生态系统功能显著降低,以生产有机物质价值降低幅度最大(41%),植被盖度次之(24%),单位面积生态资产从2.79元/m2降低到2.34元/m2,总生态资产减少3136万元;(4)河网变化和城市化成为影响生态系统功能的主要因素,其中河网变化因素和城市化因素对植被盖度降低的贡献率分别为23.1%和35.8%,对生产有机物质价值减少的贡献率分别为25.1%和32.7%,对生态系统服务价值减少的贡献率分别为7.7%和56.2%,对生态资产减少的贡献率分别为10.6%和52.2%。

Based on the topographic map data （in the late of the 1960s and 1980s）, rivers general investigation data （in 2003） and remote sensing data （MMS in 1980; TM in 1988, 2005） of Shenzhen region, the temporal and spatial changes of river networks and the relationship between river networks and urbanization ratio were analyzed. According to the above results, ecological effects of river networks change in Guanlan River basin, based on the four indicators of vegetation coverage （Vc）, biological resources value （Br）, ecosystem services value （Es） and ecological capital （Ec）, were discussed. The results showed that： （1） the river network structure appeared as a trend from comprehension to simplicity, and the development of river branches were restricted strongly in recent 30 years. The length was shortened by 355.4 km, and the number of rivers reduced 378, while the drainage density decreased from 0.84 km/km2 to 0.65 kin/km2. The major area, where the river networks decreased or disappeared, is located in the circle area with the town as the center and the radius of 1-2 km. There were 4 different types of change characteristics of river networks in all 9 drainages of Shenzhen according to urbanization ratio in the main drainage and whether or not it flows into sea directly. （2） There was significant correlation between urban expansion and river networks reduction, especially with river branches decreasing when the urban land ratio was less than 30%; while it was above 30%, the effects became weak. （3） The ecological functions of Guanlan River basin became weaker remarkably, of which Br decreased most （about 41%）, Vc was second （24%）. The ecological capital per unit area decreased from 22.79 million yuan/km2 to 2.34 million yuan/km2, while total capital reduced 3136 million yuan in 2000-2005. （4） Changing river networks and urbanization were the main reasons for the degradation of ecological functions, and they had different contribution ratios for decline of the four indexes, of which they were respectively 23.1% and 35.8% for Vc, 25.1% and 32.7% for Br, 7.7% and 56.2% for Es, and 10.6% and 52.2% for Ec. The paper provided an empirical case to recover river networks in the last several periods, and a quantitative expression of river networks change.