鄱阳湖不同湿地植物群落光合碳储量及分配

Photosynthetic Carbon Storage and Distribution in Different Wetland Communities in Poyang Lake

稳定性碳同位素自然丰度(^(13)C)表征生态系统碳循环关键过程,为了追踪陆地生态系统碳的动态及其分配,通过采用^(13)C脉冲标记对不同植物光合碳分配及其向地下输入特征进行研究,探讨鄱阳湖不同湿地植物群落(藜蒿群落、水蓼群落、苔草群落和芦苇群落)连续4年(2015—2018年)光合碳储量及分配及其相关影响因素。结果表明:(1)2015—2018年土壤有机碳含量和有机碳储量平均值均呈一致的变化规律,其中以表层土壤最高,随土层深度的增加逐渐降低,20—40 cm以下土壤有机碳含量变化范围相对较小;60—80 cm土壤有机碳含量最低;土壤^(13)C含量随土层深度的增加呈逐渐增加趋势,其中不同土层大致表现为藜蒿群落>水蓼群落>苔草群落>芦苇群落。(2)2015—2018年不同湿地植物群落土壤养分含量、地上和地下生物量平均值呈一致的变化趋势,均表现为藜蒿群落<水蓼群落<苔草群落<芦苇群落,不同植物群落差异均显著(p<0.05);而全磷含量呈相反的变化趋势,不同植物群落差异均显著(p>0.05)。(3)脉冲标记当天不同植物^(13)C值均表现为叶>茎>根>土壤,具体表现为藜蒿群落>水蓼群落>苔草群落>芦苇群落,这表明不同植物根部对光合固定新碳的富集程度较大。标记当天,不同植物地上^(13)C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,^(13)C值下降,固定的光合碳转移到土壤中的含量显著增加。(4)标记后植物-土壤系统各组分固定^(13)C量占净光合^(13)C总量分配比例呈现茎>叶>根>土壤的趋势,光合碳在不同植物各部分以及土体中都有所增加,主要集中在地上部分。(5)相关性分析结果表明,地上生物量与茎叶^(13)C含量显著正相关(p<0.05),地下生物量与根和土壤^(13)C含量显著正相关(p<0.05);由此说明地上和地下生物量对光合碳的分配起着主导作用,有利于对地下碳平衡过程和固碳减排的理解。

The natural abundance of stable carbon isotopes(^(13)C)characterizes key processes in the ecosystem carbon cycle and is used to track the dynamics and distribution of carbon in terrestrial ecosystems.The^(13)C pulse marker of different plants and photosynthetic carbon distribution to underground input characteristics had been studied for four consecutive years(2015—2018)to explore different Poyang Lake wetland plant community(plant artemisia community,water smartweed community,carex community,reed community)photosynthetic carbon reserves and distribution and its related influencing factors.The results showed that:(1)both soil organic carbon content and organic carbon storage showed consistent change patterns,among which the topsoil was the highest;with the increase of soil depth,the soil organic carbon content below 20—40 cm had a relatively small change range,the soil organic carbon content of 60—80 cm was the lowest;the content of^(13)C in soil gradually increased with the increase of soil depth,among which the different soil layers showed roughly plant artemisia community>water smartweed community>carex community>reed community;(2)the soil nutrient content and aboveground and underground biomass of different wetland plant communities showed consistent variation trends,which were all manifested as plant artemisia community<water smartweed community<carex community<reed community,and the differences among different plant communities were significant(p<0.05);the total phosphorus content showed an opposite trend,and the difference among different plant communities was significant(p>0.05);(3)on the day of pulse labeling,all the^(13)C values of different plants showed the order:leaves>stems>roots>soil,and plant artemisia community>water smartweed community>carex community>reed community,indicating that the roots of different plants had greater enrichment of photosynthetic fixation new carbon;on the day of marking,the fixed percentage of^(13)C on the ground of different plants was higher,indicating higher efficiency of marking and greater distribution difference;after pulse marking for 21 days,the^(13)C value decreased and the amount of fixed photosynthetic carbon transferred to the soil increased significantly;(4)after labeling,the proportion of fixed^(13)C in each component of plant-soil system in total net photosynthetic^(13)C showed a trend of:leaves>roots>soil,and photosynthetic carbon increased in different parts of plants and soil,mainly in the aboveground part;(5)the correlation analysis results showed that the aboveground biomass was significantly positively correlated with the^(13)C content of stems and leaves(p<0.05),and the underground biomass was significantly positively correlated with the^(13)C content of roots and soil(p<0.05),suggesting that the aboveground and underground biomass plays a leading role in the distribution of photosynthetic carbon.