黄河三角洲盐碱地垦殖对土壤碳过程的影响及其机制研究

Developing the study that the utilization and reclamation in typical saline and alkali area influences the soil carbon content and output dynamic and changing mechanism, has important scientific significance, such as estimating the changing of soil carbon storage before and after reclamation and the situation of carbon budget accurately; evaluating the functions of source and sinks and environmental effect exactly. This project uses the typical coastal saline area---the Yellow River delta in China as a case. Then we choose typical sample plots for researching the behavior changes of soil carbon (organic carbon, inorganic carbon) in 1 meter of soil before and after reclamation. We use the system that is” use of land reclamation –carbon allocation and turnover in soil –the carbon expenditure in both over and underground-changing of soil carbon and carbon balance-evaluation of environmental effect” as research idea. The main methods are field survey and controlled monitoring. And the research is focused on carbon allocation and dynamic condition and mechanisms in soil. The goal of our research is to parse the break-even of soil carbon pool, to explore the rule of soil respiration and soil carbon washing, to discuss the carbon flux which bases on the upper and lower interfaces of soil respiration and soil carbon leaching and to dissect the main process and mechanism of carbon emission. Finally, the results of our study could be used to provide fresh thoughts and fundamental data of regional carbon cycle theory and the structure of model, and to afford scientific foundation of estimating and predicting soil carbon pool’s evolutionary tendency and effect accurately in saline areas of the Yellow River delta.

开展典型盐碱区垦殖利用对土壤碳分布及输出变化等过程的影响与机制研究，对准确估算垦殖前后土壤碳储量变化及碳收支状况，正确评价其源汇功能及环境效应具有重要的科学意义。本项目以我国典型滨海盐碱区黄河三角洲为例，选择典型样地，以研究盐碱地垦殖前后1m土层土壤中碳（有机碳、无机碳）行为变化为主线，按照“土地垦殖利用—土壤内部碳分配与转化—地上地下碳支出—土壤储量变化与碳平衡—环境效应评估”的系统研究思路，采用野外调查与野外受控监测的主要方法，重点研究土壤内部碳分配及其动态与机制，解析土壤碳库盈亏变化，探求土壤呼吸和土壤碳淋洗规律，探讨基于土壤呼吸与土壤碳淋溶的上、下界面碳通量，剖析土壤碳排放主要过程与机理。研究结果可为区域碳循环理论与模型的构建提供新的思路和基础数据，为准确估算和预测黄河三角洲地区盐碱土壤碳库的演变趋势及效应提供科学依据。

开展典型盐碱区垦殖利用对土壤碳分布及输出变化等过程的影响与机制研究，对准确估算垦殖前后土壤碳储量变化及碳收支状况，正确评价其源汇功能及环境效应具有重要的科学意义。本项目以我国典型滨海盐碱区黄河三角洲为研究区域，选取了垦殖前典型盐碱荒地和垦殖后农田土壤，通过定量分析不同土层土壤碳时空分布特征，土壤呼吸动态变化以及碳淋溶特征，找出了影响碳平衡的主导因素，量化了滨海地盐碱地碳的碳收支。研究结果表明：(1) 土壤有机碳含量随着黄河三角洲土壤形成时期的增加呈先降低后升高的变化趋势，其中未利用地和农用地土壤有机碳平均含量范围分别为 2.33～4.06 g/kg和 2.82～6.09 g/kg。垦殖有利于土壤碳含量的提高，且随着垦殖年限的增加而升高，在垦殖30年左右达到平衡。(2) 小麦/玉米连作、棉田土壤有机碳储量显著高于荒地，土壤有机碳密度分别增加 44.93%和 40.32%。不同垦殖方式土壤呼吸速率表现明显的日变化、季节变化规律，土壤呼吸均为小麦/玉米连作>棉田单作>荒地。土壤温度和土壤含水量与土壤呼吸速显著正相关，是影响其变化的主导因素。(3) 灌溉淋洗导致土壤的SOC和盐分含量下降，但会导致SOC和盐分含量在土壤底层积累。300 mm灌溉水量能将0-40 cm土层土壤从重度盐碱土改良到轻度盐碱土，有机碳淋失率相对较低，为最合适灌水量。(4) 基于对比垦殖前后土壤有机碳动态变化分析，并结合土壤呼吸以及灌溉淋溶液的碳输出，对垦殖前后土壤碳储量进行估算，构建了滨海盐碱地垦殖利用后的碳平衡模型，研究发现黄河三角洲盐碱地垦殖为农田后变现为土壤碳库增加。研究结果为区域碳循环理论与模型的构建提供了基础数据，并为准确估算和预测黄河三角洲地区盐碱土壤碳库的演变趋势及效应提供科学依据。