稳定性碳同位素自然丰度(13C)记录着生态系统碳循环过程的关键信息,常被用于评价全球变化情景下陆地生态系统碳的动态。连续4年(2015—2018年)采用13C脉冲标记对不同园林植物光合碳分配及其向地下输入特征进行了研究,探讨不同园林植物光合碳在不同器官的分配及其对土壤有机碳(SOC)的贡献。结果 表明:(1)脉冲标记当天不同园林植物13C值均表现为叶>茎>根>土壤,具体表现为樟树>夹竹桃>广玉兰>女贞,不同园林植物根部对光合固定新碳的富集程度较大。(2)标记当天,不同园林植物地上13C固定百分比例较高,说明标记的效率较高且分配差异较大; 脉冲标记21 d后,13C值下降,固定的光合碳转移到土壤中的含量显著增加。(3)标记后植物—土壤系统各组分固定13C量占净光合13C总量分配比例呈现茎>叶>根>土壤的趋势,光合碳在不同园林植物各部分以及土体中都有所增加,主要集中在地上部分。(4)樟树和夹竹桃对土壤有机碳的贡献量最大,对土壤有机碳的贡献量具体表现为樟树>夹竹桃>广玉兰>女贞; 有机碳的累积量呈相反的变化趋势。(5)根系和地上部生物量与13C-SOC之间存在显著的正相关关系。总之,不同园林植物显著影响了光合同化碳在地上部和土壤中的分布,其中樟树和广玉兰光合同化碳在植株—土壤系统的响应较为显著。
The natural abundance of stable carbon isotopes(13C), which records key information about the carbon cycling process of ecosystems, is often used to evaluate the carbon dynamics of terrestrial ecosystems under global change scenarios. In this study, 13C pulse marker was used to study the photosynthetic carbon distribution and its underground input characteristics of different garden plants, to explore the distribution of photosynthetic carbon in different organs of different garden plants and its contribution to soil organic carbon, which is of great significance to the understanding of carbon balance of urban ecosystem. The results showed that:(1)on the day of pulse marking, the 13C values of different garden plants all decreased in the order: leaves>stems>roots>soil, and privet of camphor tree>oleanthus magnolia, indicating that the roots of different garden plants had greater enrichment of new carbon of photosynthetic fixation;(2)on the day of marking, the fixed percentage of 13C on the ground of different garden plants was higher, indicating higher efficiency of marking and greater distribution difference; after pulse marking for 21 days, the 13C value decreased and the amount of fixed photosynthetic carbon transferred to the soil increased significantly;(3)after labeling, the proportion of fixed 13C in each component of plant-soil system in total net photosynthetic 13C decreased in the order: leaves>roots>soil, and photosynthetic carbon increased in different parts of garden plants and soil, mainly in the aboveground part;(4)camphor tree and oleander have the largest contribution to soil organic carbon, and the contribution to soil organic carbon decreased in the order: camphor tree>oleander>magnolia broadleaf>privet; the accumulation of organic carbon showed an opposite trend;(5)correlation analysis results showed that there was a significant positive correlation between root and aboveground biomass and 13C-SOC. Further analysis results showed that different garden plants significantly affected the distribution of photosynthetic carbon in the aboveground and soil, among which camphor and magnolia had significant responses in plant-soil system.
