华北平原典型农田生态系统次生碳酸盐累积转化机制

There is a lack of knowledge on transformation and accumulation of pedogenic carbonate (PIC) in the terrestrial ecosystems. In this study, we propose to carry out a four-year, integrative study at two long-term fertilization experiment sites under wheat-maize rotation in the North China Plain. We will determine soil organic carbon (SOC) and inorganic carbon (SIC) and their isotopic compositions in archived soil samples and newly collected soils, then calculate the accumulation rates of SOC, SIC and PIC. Field measurements of aboveground CO2 and belowground CO2 (near the surface) and their δ13C will be carried out and used to calculate the contributions of various carbon sources to soil respiration, and the contributions of soil respiration and net CO2 uptake by crop to net ecosystem CO2 exchange. We will measure soil CO2 and dissolved carbonate, and their δ13C at different depths, which will be used to study the impacts of land managements on the transformations and transportations of various carbon forms in the wheat-maize rotation system. To this end, we will reveal the mechanisms regulating PIC accumulation in the typical cropland of the North China Plain. This study aims to improve our understanding of the key biogeochemical processes in the terrestrial carbon cycle.

农田碳库转化因与气候变化密切相关而受到人们广泛关注。本项目针对中国北方农田土壤有机碳（SOC）可能向无机碳（SIC）转化的假设，拟解决SIC累积转化过程及驱动机制这一科学问题，以华北平原典型潮土小麦-玉米轮作系统郑州和桓台长期试验为基础，分析不同施肥处理下历史和项目期间SOC、SIC及其δ13C，确定SIC累积速率，量化次生碳酸盐（PIC）的贡献；通过测定地上地下CO2及其δ13C，定量区分SOC分解、根呼吸和秸秆分解对土壤呼吸的贡献及作物光合/呼吸和土壤呼吸对生态系统CO2通量的贡献；通过地上地下各形态碳的同步观测，明确其时空变化规律以及地表CO2通量与土壤剖面CO2产生和扩散的关系；分析不同碳源对PIC的贡献及其与土壤环境变量的关系，探明华北平原典型农田土壤PIC累积转化过程及其驱动机制。研究结果不仅能丰富对陆地生态系统碳循环的认识，而且能为准确估算中国北方农田固碳潜力提供科学依据。

本项目围绕华北平原典型农田生态系统次生碳酸盐累积转化机制，通过开展面上采样分析、野外原位培养实验和室内控制实验，定量区分了华北平原典型潮土、小麦-玉米轮作系统土壤中原生碳酸盐、次生碳酸盐在土壤无机碳所占比重，明确了农田土壤中不同形态有机碳和无机碳的空间变化特征和主控因素，探明了施用化肥、有机物料、石膏等对农田生态系统土壤碳库及土壤呼吸的调控机制。研究取得了具有创新性的结果，发表了高质量SCI论文7篇（4篇一区，3篇二区），其中5篇top，培养2名博士研究生和5名硕士研究生。