流域陆地生态系统水体净化服务表征及驱动力分析

陆地生态系统的水体净化服务能过滤地表径流中的污染物,有助于防控流域非点源污染。准确表征该服务的时空变化特征,定量探索其驱动机制则是生态系统服务应用的前提。论文以太湖流域典型地区为例,利用空间分布式的生物物理模型,研究流域陆地水体净化服务的空间格局与时间演变特征,并借助GIS空间统计方法及面板数据模型分析其主导驱动力。结果显示：2000—2010年间研究区59.19%、58.27%的面积分别为氮、磷净化服务的弱降低区。2000—2005年与2005—2010年两个时间段内研究区氮净化服务先下降后略有上升,其中苏州市区增幅最大;磷净化服务为下降趋势,以无锡和苏州市区降幅最大。气候因素和水网密度对水体净化服务具有显著正影响,而负向驱动力则存在差异。为此应采取适当的措施调整主导因素,提高陆地生态系统的水体净化服务,减少氮、磷排放,为流域非点源污染治理及水环境管理提供支撑。

Characterizing water purification services and quantifying their driving factors in watershed terrestrial ecosystems

Water purification services of the terrestrial ecosystem can filter out pollutants in surface runoff, which helps to reduce emissions into the water body. Therefore, improving these services is an effective way to control non-point source pollution in watersheds, and accurately quantifying the spatiotemporal characteristics and driving factors of change of the services is the precondition for such improvement. Purification services for nitrogen and phosphorus are two typical water purification services, which can be quantified by nitrogen and phosphorus exports as the reverse proxy indicators. Taking a representative area of the Taihu Lake Basin in 2000-2010 as a case, we used the nutrient purification model in the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) tool to quantify nitrogen and phosphorus indicators of terrestrial ecosystem. The spatial pattern and temporal variation of purification services for nitrogen and phosphorus were characterized by the spatial analysis method in ArcGIS. In order to quantify the driving factors of change of the services, we developed a panel data model based on 31 selected factors and GIS spatial statistics methods. The results show that there were obvious spatial heterogeneities between nitrogen and phosphorus indicators and change over time. Both nitrogen and phosphorus purification services showed a spatial characteristic of widely weak decrease from 2000 to 2010, with the areal ratios of 59.19% and 58.27%, respectively. With regard to the temporal variation of service amount, nitrogen purification service of the study area first reduced then increased slightly during 2000-2005 and 2005-2010, and the increase in Suzhou urban district, Wuxi urban district, and Kunshan City were obvious. Phosphorus purification service was always in decline during 2000-2005 and 2005-2010, and the urban districts of Wuxi and Suzhou experienced the largest reduction. Water purification services are influenced by multiple driving factors in the physical, social, and economic domains. Climatic factors and water network density had significant positive influences on these two services, while the negative driving factors differed. Arable land proportion, village density, and agricultural population density had major negative effects on nitrogen purification service; while urban land density mainly impacted negatively on phosphorus purification service. Therefore, appropriate measures should be implemented to improve these two water purification services according to the driving factor analysis. Climate change adaptation policy can contribute to synergistically manage nitrogen and phosphorus purification services. Meanwhile, different control measures should be taken because of the varied driving factors between nitrogen and phosphorus purification services. Improving production and living conditions in rural areas and guiding individual behaviors of farmers can help to reduce the impact of agricultural activities on nitrogen purification service. Adjusting production and daily living activities in urban areas can reduce phosphorus emissions and enhance the phosphorus purification service of the terrestrial ecosystem. This study can provide support for non-point source pollution control and water management in watersheds.