中国生态系统水源涵养空间特征及其影响因素

Spatial patterns of ecosystem water conservation in China and its impact factors analysis

水源涵养是陆地生态系统重要生态服务功能之一,包含着大气、水分、植被和土壤等自然过程,其变化将直接影响区域气候水文、植被和土壤等状况,是区域生态系统状况的重要指示器。我国水资源贫乏,降水时空分布不均,在区域尺度上评估全国生态系统水源涵养功能空间特征及其影响因素,对科学认识和合理保护我国生态系统水源涵养,和制定生态环境保护决策具有十分重要的意义。以全国生态系统水源涵养功能为研究对象,通过收集和分析相关数据,对各类典型生态系统水源涵养数据进行归类与统计,在区域尺度上评估中国生态系统水源涵养功能,并分析气候与人类活动对其影响。结果表明:(1)中国水源涵养总体上呈现东南高西北低、由东到西逐渐递减特征。2010年全国生态系统水源涵养总量为12224.33亿m^3。(2)森林是我国生态系统水源涵养的主体,其水源涵养量最高,占全国水源涵养总量的60.80%。其中,常绿针叶林生态系统水源涵养量最多,而常绿阔叶林水源涵养能力最高。按流域统计,相对于其他一级流域,长江流域生态系统的水源涵养量最高。(3)中国生态系统水源涵养受气候和人类活动的影响,与降水、温度、蒸散、坡度、COD密度和长江生态工程呈现显著的正相关,而与GDP密度和农村人口密度呈现明显的负相关。

Water conservation is an important component of ecosystem services, and is involved in natural processes such as regional climate circulation, the hydrologic cycle, vegetation growth and survival, soil conditions, and other natural processes. It is also an important indicator of regional ecosystem status. Water resources in China are scarce, and precipitation is uneven through time and space. Many researchers have attributed water resource loss in China to long-term human interference and widespread changes in land use and cover. Other studies have found that climate conditions, such as drought, severe storms, and temperature fluctuations are the primary cause of water resource changes. Whatever be the cause, recent studies have shown that human activities can improve the level of water conservation in selected study regions across China. It is necessary to investigate current water level conservation and its response to climatic variation and human activities, which will allow for a better understanding of their accumulated consequences.This study analyzed literature and applied Geographic Information System techniques to analyze the hydrological characteristics of different ecosystems, and to develop a method to assess the water conservation service of different ecosystems at a regional scale while considering how those water conservation services formed. We quantified the water conservation services of different ecosystems in China comparing those services across different types of ecosystems, basins and elevations separately. We then analyzed the respective effect of climate and human activities on spatial patterns in water conservation services. We found that：（1） In China, water conservation followed a decreasing trend from the southeast to the northwest of inland areas. The total amount of water conserved in China in 2010 was 12224.33×108m^3. The vast areas south of the Yangtze River, which experience high levels of precipitation, were the primary water conservation area. This included the middle and lower reaches of the Yangtze River; the hilly areas near the southern Yangtze River; the Sichuan basins; and the Yunnan, Guangxi, Guangdong, and Taiwan areas. Conversely, we found relatively weak water conservation services in ecosystems in areas of northeastern China, northeastern Inner Mongolia, northern China, Shaanxi-Gansu-Ningxia province and northwestern Xinjiang province.（2） Ecosystem types performed different water conservation services. Forests were the main carriers of water conservation, as they produced the highest amounts of water conservation. They produced 7432.32×108 m^3, which accounts for 60.80% of the total. The contribution of different forest types to water conservation in decreasing order was as follows：evergreen broadleaf forest 〉 evergreen needleleaf forest 〉 mixed needleleaf and broadleaf forest 〉 deciduous broadleaf forest 〉 deciduous needleleaf forest 〉 sparse forest. Evergreen coniferous forests could produce the most amount of water conservation, however its capacity was not the highest.（3） The spatial characteristics of water conservation services are formed by interactions among several influencing factors. There were partial correlations between water conservation and precipitation, temperature, evapotranspiration, slope, Chemical Oxygen Demand （COD） density and ecological restoration project in the Yangtze River basin were positive and statistically significant. By contrast, water conservation was negatively correlated with the Gross Domestic Product （GDP） of the region and the rural population density. As the social economy developed rapidly, the influence of human activities on water conservation gradually increased. However, climate and topography were still the dominant factors that influenced the spatial characteristics of water conservation. These results provide specific information that may serve to strengthen the necessary public awareness about protecting and restoring water conservation services.