黄河三角洲滨海湿地CNP生态化学计量学格局及其驱动因素研究

The coastal wetland is a sensitive transition zone with land-ocean interactions. How can water and salinity gradients change C, N and P stoichiometry of coastal wetland? Does it have quantitative expression? How big are the differences among the stoichiometry of typical plant communities at different succession stages? Does each of them have a certain threshold? Meanwhile, how does anthropogenic cultivation affect C, N and P stoichiometry of soil and plant in the costal wetland? In order to answer these scientific questions, coastal wetlands located in the Yellow River Delta (YRD) are selected as study objects, and patterns of C, N and P ecological stoichiometry will be studied by using filed survey and laboratory simulation method. The main goals of this project are (i) to determine the effect degree of water and salinity to C, N and P ecological stoichiometry, (ii) to confirm the value of soil and plant C:N:P stoichiometry and its threshold of typical plant communities in coastal wetland of YRD, (iii) to evaluate anthropogenic cultivation on C, N and P stoichiometry of coastal wetland function and environmental effects. The results of this study not only can fill the blank of C, N and P ecological stoichiometry research in coastal wetland of YRD, but also can offer important scientific gist which is propitious to perfect mechanism of vegetation formation and succession and exploration of elemental stoichiometry with human intervention in coastal wetland, but also provide a useful reference for ongoing wetland conservation and restoration in the YRD.

滨海湿地处于陆海相互作用最敏感地带。滨海湿地CNP化学计量学随着水盐梯度的变化如何？是否可以定量化表达？不同演替阶段典型植物群落生长季内CNP化学计量学差异程度有多大？是否具有阈值？农业开发对土壤和植物元素化学计量学的影响程度又是如何？为了回答这些问题，本项目选择黄河三角洲滨海湿地为研究对象，运用野外调查与控制实验相结合的方法，研究黄河滨海湿地土壤及植物CNP生态化学计量学格局；阐明非生物环境因子(水分、盐度和养分等)对滨海湿地植物CNP生态化学计量学的影响程度；明确黄河三角洲土壤和植物化学计量学比值大小及典型植被群落化学计量学阈值；评估农业开发对湿地土壤和植物元素化学计量学的贡献及其环境影响。研究结果有助于完善滨海湿地植物群落演变机理，有助于探索对滨海湿地元素计量学的人为干预途径，同时对评价滨海湿地养分限制状况及其潜在的环境效应具有一定的理论和实践意义。

本研究以黄河三角洲国家自然保护区内滨海湿地为研究对象，通过野外大范围土壤植物调查和测试工作获取滨海湿地土壤和植被CNP化学计量学格局图；通过水位控制和NP添加控制实验；阐明非生物环境因子(水分、盐度和养分等)对滨海湿地植物CNP生态化学计量学的影响程度。通过对不同植被类型和不同开发程度的滨海湿地的定点监测，明确黄河三角洲土壤和植物化学计量学比值大小及典型植被群落化学计量学阈值，同时评估农业开发对湿地土壤和植物CNP化学计量学的贡献及其环境影响。.研究发现：1）黄河三角洲国家级自然保护区土壤RCN、RCP和PNP值范围分别为12.44-158.76、26.48-133.26和0.23-9.97。大汶流、黄河口和一千二管理站的RCNP值分别为64.10: 2.29: 1、60.48: 1.31: 1和61.58 : 1.94 : 1。2）微地貌对黄河三角洲贝壳堤湿地土壤和植物CNP化学计量特征的影响显著，土壤和植物RCNP约束性较差，生态系统受到N和P限制，芦苇和翅碱蓬的生长受到P限制。3）随补水频次的增加，规律性补水可以增加芦苇对营养物质的吸收。施用N肥可以提高芦苇根器官对P的吸收。施用P肥对促进芦苇生物量和营养物质积累作用不明显。4）自身生长节律在NP供应条件剧烈变化的情况下仍是碱蓬叶片N、P元素特征重要控制因素，而生长时期对柽柳叶片化学计量特征的调节作用不显著，表明不同生活型物种在生理生态上对生长阶段的反馈强度存在差别。5）不同生境和不同土地利用方式下，新生湿地、退耕湿地和棉田土壤RCNP比值分别为42.6 : 1.6:1、71.2 : 2.0 : 1和63.2 : 1.9 : 1，约束性较差。土壤中RNP比值约为1.9 : 1，显著低于世界和中国平均水平，土壤处于缺N状态。新生湿地、退耕湿地和棉田中植物RCNP分别为1753 : 22.4 : 1、1539 : 23.0 : 1和1196 : 23.8 : 1。植物土壤RNP约束性较好，在23左右。.研究结果有助于完善滨海湿地植物群落演变机理，有助于探索对滨海湿地元素计量学的人为干预途径，同时对评价滨海湿地养分限制状况及其潜在的环境效应具有一定的理论和实践意义。