北京市4种城市功能区森林植被涵养水源功能评价及价值估算

本研究对北京市首都功能核心区、城市功能拓展区、城市发展新区和生态涵养发展区进行林分涵养水源功能评价及价值估算，旨在探究提升城市功能区森林水源涵养功能较优林分配置模式。结果表明：（1）北京市森林植被面积2009年为4.00×10⁵ hm²，2014年为4.59×10⁵ hm²，北京市NDVI平均值2009年为0.331，2014年为0.708，北京市森林植被面积总体呈增加趋势。北京市2014年林地绿化调节水量较2009年降低了近1/3，2014年水源涵养功能价值量较2009年分别减少了22.08%和8.24%。（2）生态涵养发展区水源涵养功能年平均能力最强（2.88×10⁸ m³/a），城市发展新区水源涵养功能年平均能力次之（1.72×10⁸ m³/a），而首都功能核心区水源涵养功能年平均能力相对最弱，仅1.05×10⁶ m³/a。在针叶林、阔叶林和混交林三种林分类型中，2014年混交林水源涵养功能价值量较2009年增加5.13%，而阔叶林和针叶林分别减少34.93%和55.55%。（3）培育纯林，提高森林覆盖率，对于调节水土资源和保护生态环境具有非常重要的生态意义，而从森林水源涵养功能实物量和价值量考虑，认为混交林比纯林具有更强的水源涵养功能和较优的经济价值。在城市特定的条件下，建立生态与景观相协调的人工植物群落使城市土地资源的利用达到生态、社会、经济三大效益的最佳结合，是提高城市绿地质量的关键所在。

Evaluation and value estimation of water conservation function of forest vegetation of four urban functional areas in Beijing

In this study, an optimal forest configuration for water conservation function was explored, which this optimal forest configuration could guarantee the forest vegetation can be give full play to water and soil conservation function. The remote sensing image data in 2009 to 2014 of Beijing and the data of Beijing forest resources inventory of 2009 and 2014 were used to carry out the evaluation and value estimation of water conservation function of typical forest (coniferous, broad-leaved and mixed forests) with GIS software in this paper, where in capital function core area, urban function development area, new urban development area and ecological conservation development area in Beijing. The evaluated and estimated results show: (1) the forest vegetation area in Beijing was 4.00×10⁵ hm² in 2009 and 4.59×10⁵ hm² in 2014. The average Normalized Difference Vegetation Index (NDVI) in Beijing was 0.331 in 2009 and 0.708 in 2014. The forest vegetation area in Beijing presented an overall increasing trend. The regulated water volume of forest land greening in Beijing in 2014 was nearly 1/3 lower than that in 2009, and the value of water conservation function in 2014 was 22.08% and 8.24% lower than that in 2009, respectively. (2) The annual average capacity of water conservation in the ecological conservation development area is the strongest (2.88×10⁸ m³/a), followed by the annual average capacity of water conservation in the new urban development area (1.72×10⁸ m³/a), while the annual average capacity of water conservation in the capital core area is the weakest (1.05×10⁶ m³/a). Among the coniferous, broad-leaved and mixed forests, the value of water conservation function of mixed forest is increasing, and its value of this forest type increased by 5.13% in 2014 compared with that in 2009, while the value of water conservation function of broad-leaved forest and coniferous forest decreased by 34.93% and 55.55%, respectively. (3) Cultivating pure forest to increase the forest cover rate has a very important ecological significance for regulating soil and water resources and protecting ecological environment, but considering the amount and value of forest water conservation function, this study concluded that the mixed forest had stronger water conservation function and better economic value than pure forest. Under the specific conditions of the city, the artificial plant community coordinated with ecology and landscape can make the utilization of urban land resources to reach the ecological society. The best combination of the three economic benefits is the key to improve the quality of urban green space.