生态补水驱动下白洋淀生态系统服务演变趋势

自20世纪八九十年代以来水利部、河北省先后开展了近50次生态补水,成为缓解白洋淀水位下降、减少生态空间萎缩和修复生态系统功能的重要措施。为进一步揭示补水措施对淀区生态系统服务功能的影响,基于白洋淀1991、1996、2005年和2015年4期遥感数据,利用InVEST模型和市场价值法对白洋淀碳储量、栖息地质量、物质生产和文化4种服务功能进行了时空分布定量评估。研究结果显示,受多重人类活动和气候变化等影响,芦苇草地和水域面积占比下降20%,且深水区面积占比显著减少;研究期内白洋淀栖息地质量平均得分从20世纪90年代的0.63下降到2015年的0.49,下降趋势显著;平均碳密度1991-2005年稳定在32.33 t·hm^-2左右,但2015年下降到30.23 t·hm^-2,与芦苇草地面积减少有关;物质生产和文化功能均随着时间变化呈现较明显的增加趋势。总生态系统服务平均得分从20世纪90年代的0.80~0.82,逐步增加到2005年的0.93,到2015年降低到0.79。从整体上看,白洋淀生态补水工程在一定程度上维护了其生态系统服务功能,但生态服务的高值区域斑块化更为明显。未来可进一步深化白洋淀生态系统服务对补水策略的动态响应和权衡模式研究,科学支撑湿地生态水利管理决策。

Changes in ecosystem services in Baiyangdian Lake driven by environmental flow releases

Environmental flow releases to Baiyangdian Lake have been implemented nearly 50 times by the Ministry of Water Resources and the local government of Hebei Province, which play a critical role in maintaining water levels, protecting the ecological space, and restoring ecosystem function. In order to further reveal the effects of environmental flow releases on the ecosystem services and function of the lake, we assessed the carbon density, habitat quality, material production, and cultural services using the InVEST model and market value method based on four remote sensing data sets from 1991, 1996, 2005, and 2015 for Baiyangdian Lake. The area ratios of reed, grassland, and open water showed a 20% decrease, in which there was a clear reduction in the deep water area. The average score of the habitat quality was reduced from 0.63 in 1991 to 0.49 in 2015. From 1991 to 2005, the average carbon density was stable at a level of approximately 32.33 t·hm^-2, but decreased to 30.23 t·hm^-2 until 2015, which was associated with the reduction in reed and grassland area. The material production and cultural function presented clear increases over time. The average score of the total ecosystem services was 0.81 in the 1990s, increased to 0.93 in 2005, and then decreased to 0.79 in 2015. Thus, we found that environmental flow releases have maintained the ecosystem services to some degree, but the fragmentation in the highest score region has been more apparent. In the future, it is necessary to disclose the dynamic response of ecosystem services to the flow releases and to develop the trade-off relationships among the services for supporting ecological water conservancy management decisions.