黄河三角洲滨海湿地灌丛化过程及其水、盐作用机制

Due to global climate changes and human activities, the gradient patterns of environmental factors on the coastal zone have been changed greatly. Consequently, woody shrubs have increasingly encroached in the intertidal coastal wetland, becoming a new landscape feature and changing the structure and function of wetland ecosystems. However, little is known about the encroaching processes and the mechanism of shrub encroachment in the northern coastal wetland in China, since previous works have been done on the shrub-encroached grassland (SEG) landscapes, mangrove wetland landscapes and as well as. .In this proposal, we will focus on the changing patterns of water resources and their influences on shrub encroachment in the Yellow River Delta. The changes in spatial patterns of shrub encroachment from 1960 to 2017 will be analyzed by the GIS spatial analysis. The relationship between historical shrub wetlands and the related landscape factors will be calculated in order to analysis the influencing mechanism of environmental or landscape factors on the encroachment patterns. .The spatial characteristics of the effects of water resources and soil salinity on vegetation were evaluated by a species distribution model, MaxEnt model. And the distribution pattern of dominant shrub species in the delta for the next 50 years will be forecasted by MaxEnt and the planning global climate patterns. .In order to understand the maintaining mechanism of shrub encroachment, we will analysis the variability of water resource utilization in shrub and herb species on the different precipitation scales, using stable isotope technology. The differences of water sources, water use features and water use strategies for shrub and herb species in this delta will be assessed also. The effects of water competition between shrub and herb species will be discussed using ecological niche models to indicate the shrub encroachment mechanism in these high salinity coastal zones. The results will be helpful to understand the processes of shrub encroachment of coastal wetland and to provide the scientific suggestions on coastal wetland restoration.

由于全球气候变化和人为干扰活动的影响，海岸带环境因素的梯度格局发生改变，使灌木物种分界海向移动，在典型滨海湿地生态系统中比例增加，形成新的湿地景观。中国北方滨海湿地灌丛化过程和产生机制鲜有报道。本项目拟以黄河三角洲灌丛化湿地生态系统为研究对象，以水资源变化分析为主线，基于3S空间分析技术，量化黄河三角洲近50年历史时期灌丛湿地空间格局的变化过程，揭示湿地灌丛化形成的景观驱动机制和形成规律；采用MaxEnt物种分布模型，耦合未来气候变化情景，确定水、盐等主导环境因子的影响特征，进行优势灌木柽柳分布格局的预测分析；采用稳定同位素技术，对比分析不同时、空尺度上湿地系统中灌、草物种水分利用来源、水分利用特征和水分利用策略的差异，揭示灌、草物种在海岸带高盐环境下的水资源竞争机制。通过对黄河三角洲湿地灌丛化过程和产生机制的研究，旨在以此为模式对中国北方滨海湿地灌丛化研究及湿地恢复提供科学依据。

通过分析黄河三角洲湿地生态系统在灌丛入侵的过程中的湿地格局演变特征及其水盐驱动机制，为滨海湿地生态系统综合管理和全球变化下湿地演变及其蓝碳功能评估提供科学依据。整合遥感信息提取、GIS空间模型构建、野外调查采样、实验室测定分析等技术，主要结果如下：.（1）构建了基于斑块水平的黄河三角洲湿地景观连通性评估模型及方法体系，量化评估了三角洲湿地景观连通性的演变特征、空间格局和未来发展趋势，并分析其景观驱动机制；构建黄河三角洲湿地保护恢复生态网络, 实现了基于斑块水平的湿地保护、修复精准评估；确定了维持三角洲滨海湿地整体连通性的关键廊道和节点的位置、数量，分析影响其连通性的主要因素，为滨海湿地生态系统多尺度保护修复和区域水资源管理提供方法支持。.（2）建立土壤碳、氮三维空间响应模型，并从物种多样性、分布格局和生态计量特征三个层次揭示土壤系统对灌丛化响应机制；量化了灌丛化湿地区域的主要环境因子与土壤C、N及其稳定同位素的空间关系，为蓝碳生态系统固碳增汇功能提升研究提供关键参数，如尺度转移点；研究土壤CNP生态计量特征及其空间格局，揭示C:N和N:P是表征土壤质量演变的主要指标；分析灌丛化湿地土壤碳库主要组分有机碳（SOC）和无机碳（SIC）的变化特征及其影响因素，探讨SOC和SIC对灌丛化过程的响应差异，为黄河三角洲灌丛化湿地生态系统灌、草竞争效应评估和海岸带湿地生态系统功能及其演变研究提供思路。.（3）结合灌丛化湿地土壤粒径的多重分形分析方法及土壤粒径空间格局的孔隙度计算方法，量化灌丛化湿地不同景观类型下土壤粒径的空间格局和变异特征；利用地理探测器和机器学习等方法，建立了土壤粒径各参数之间及其与土壤盐度等环境变量的空间关系，揭示土壤物理特征对湿地灌丛化的响应机制；基于样带数据，建立了不同灌丛化湿地类型土壤粒径、盐度和CN的关系，利用结构方程模型量化灌丛化对其的直接和间接作用效应，初步分析灌丛化土壤CN变化的驱动影响。