大气CO2 浓度升高条件下水稻光合碳在土壤中的转化和稳定机制

Elevated atmospheric CO2 concentration effects on the accumulation and transportation of plant photosynthetic carbon, and consequently bound to affect the key carbon cycle process of terrestrial ecosystems. However, the input, transformation and stability mechanisms of plant photosynthetic carbon in soil carbon pool as response to the elevated CO2 concentration are needed to be illuminated. Therefore, this project will use the "plant - soil – microbial ecological processes” as the main line. The 13C isotope continuous labeling technology combined with soil physical-chemical grouping method, will be taken to clarify the transformation characteristics of photosynthetic carbon in soil carbon pool and its response to elevated CO2 concentration including the influence of elevated CO2 concentration on its distribution dynamic in the soil physical (particles, density) and chemical component (humus) as well as the mineralization and transformation characteristics of photosynthetic carbon in the soil different particle component, to clear the stability mechanism and temperature sensitivity of photosynthetic carbon. The microbial molecular biology and microbial marker technology will be also used to analyze the dynamic changes of key enzyme activity and the activity, community and composition of the microbial functional groups which participated in the underground transfer process of photosynthetic carbon under elevated CO2 concentration. Its coupling mechanism and environmental factors will also be discussed. The project will provide a scientific basis for understanding the carbon cycle process in paddy ecosystems.

大气CO2浓度升高影响植物碳库并对陆地生态系统碳循环关键过程产生深刻影响。然而，植物光合碳向土壤碳库的输入及其转化与稳定过程对CO2浓度升高的响应机制尚不清楚。因此，本项目以“植物—土壤—微生物生态过程”为主线，综合应用13C–CO2连续标记技术结合土壤物理–化学分组方法，量化大气CO2浓度升高对水稻光合碳向土壤碳库输入的影响，探讨光合碳在土壤碳库不同物理（颗粒、密度）和化学组分（腐殖质组分）间的分配动态、矿化和周转特性及其对大气CO2浓度升高的响应规律，明确光合碳在土壤碳库中的稳定机制及其温度敏感性；同时，综合运用微生物分子生物学技术与微生物标识物技术，研究CO2浓度倍增条件下，深度参与水稻光合碳转化和稳定过程的土壤功能微生物群落及其结构特征、关键酶活性与环境因子的耦联机制。研究结果可为全面理解大气CO2浓度变化下陆地生态系统碳循环过程和调控机制提供基准数据支撑。

大气CO2浓度升高影响植物碳库并对陆地生态系统碳循环关键过程产生深刻影响。然而，植物光合碳向土壤碳库的输入及其转化与稳定过程对CO2浓度升高的响应机制尚不清楚。本项目以“植物—土壤—微生物生态过程”为主线，综合应用13C–CO2连续标记技术结合土壤物理–化学分组方法，量化了大气CO2浓度升高对水稻光合碳向土壤碳库输入的影响，探讨了光合碳在土壤碳库不同物理（颗粒、密度）和化学组分（腐殖质组分）间的分配动态、矿化和周转特性及其对大气CO2浓度升高的响应规律；同时，综合运用微生物分子生物学技术与微生物标识物技术，研究了CO2浓度倍增条件下，深度参与水稻光合碳转化和稳定过程的土壤功能微生物群落及其结构特征、关键酶活性与环境因子的耦联机制。取得了以下研究成果：1）CO2浓度升高和施氮均能增加水稻光合碳向土壤中的输入量，并通过微生物周转途径和与矿物结合的途径形成较为稳定的土壤有机质。2）细菌和真菌在光合碳的周转中表现出一定的时效性：真菌在新输入的光合碳的响应速度上表现出一定的优势，细菌在光合碳输入一定时间之后对其利用的活性逐渐增强。3）被微生物利用的光合碳还可通过真菌和细菌中的代谢物或死亡残体（残留体碳）的释放，进入矿物结合态有机物稳定途径中。4）CO2浓度升高和施氮通过改变光合碳的质量及其生物有效性组分，调节微生物的利用特征，从而影响光合碳对稳定有机质的贡献。以上研究结果可为全面理解大气CO2浓度变化下陆地生态系统碳循环过程和调控机制提供基准数据支撑。