长白山阔叶红松林演替序列植物-凋落物-土壤碳同位素特征

稳定碳同位素组成能精确指示生态系统碳循环过程,可以为深入研究森林演替进程对碳循环过程和固碳潜力的影响提供关键信息.利用稳定碳同位素技术对长白山阔叶红松林演替序列3种林分——中龄杨桦次生林、成熟杨桦次生林、阔叶红松林的叶片、树干、根系、凋落物和土壤δ¹³C值及碳、氮元素含量进行测定.结果表明: 各演替序列优势树种叶片δ¹³C从冠上到冠下均呈降低趋势;树干δ¹³C表现为树皮小于木质部;根系δ¹³C表现为细根小于粗根.阔叶红松林未分解凋落物δ¹³C小于半分解及全分解凋落物,次生林相反;土壤δ¹³C沿深度逐渐增加.总体上,δ¹³C值叶片<凋落物<根系<树干<土壤,说明植物各器官之间有明显的碳同位素分馏效应,且相同器官不同部位之间也存在差异;植物δ¹³C沿演替方向先减小后增加,土壤δ¹³C沿演替方向不断增加,且变化规律可以通过氮元素含量与碳同位素分馏效应的关系解释,说明长白山阔叶红松林演替过程优势树种和碳周转速率的变化影响了碳同位素分馏.

Stable carbon isotopic characteristics of plant-litter-soil continuum along a successional gradient of broadleaved Korean pine forests in Changbai Mountain,China.

Stable carbon isotope composition can accurately indicate ecosystem carbon cycling and provide key information for the study of the influence of forest succession on the carbon cycling and carbon sequestration potential. We measured the δ¹³C values and carbon and nitrogen contents of leaf, trunk, root, litter, and soil along a forest successional gradient in Changbai Mountain, which included a middle-aged poplar-birch secondary forest, a mature poplar-birch secondary forest, and an old-growth broad-leaved Korean pine forest. The results showed that leaf δ¹³C reduced with their position from the upper canopy to lower canopy, bark δ¹³C was less than xylem, fine root δ¹³C was less than course root. In contrast to the secondary forests, δ¹³C of the undecomposed litter layer was less than that of the semi-decomposed layer and decomposed litter layer in the broad-leaved Korean pine forest. Soil δ¹³C increased with depth. The ascending order of mean δ¹³C was leaf, litter, root, trunk, and soil, indicating that there is obvious fractionation among different organs of plants and among different parts of a specific organ. In addition, plant δ¹³C first decreased and then increased with the succession process, but soil δ¹³C increased with the succession processes. The different patterns of the changes of plant and soil δ¹³C along forest succession could be explained by the relationship between nitrogen content and carbon isotope fractionation effect, indicating that carbon isotope fractionation was affected by the change of dominant tree species and the variation of carbon turnover rate.