黔西南北盘江镇喀斯特高原峡谷区植被演替阶段碳氮稳定同位素特征

Carbon and nitrogen stable isotopes of vegetation succession stages in karst plateau gorge area of Beipanjiang in southwestern Guizhou

关键词:  δ¹³C值, δ¹⁵N值, 叶片-凋落物-土壤连续体, 森林演替, 碳氮循环, 喀斯特高原峡谷

Key words:  δ¹³C value, δ¹⁵N value, leaf-litter-soil continuum, forest succession, carbon and nitrogen cycle, karst plateau gorge

摘要:

为了探究森林不同演替阶段碳氮(C、N)、稳定碳氮同位素值(δ¹³C、δ¹⁵N)随演替发生的变化特征与内在联系,该文以喀斯特高原峡谷区草灌、灌木、乔灌和乔木4个演替阶段的森林植物群落为研究对象,测定了叶片-凋落物-土壤的C、N及稳定同位素值,并分析其在不同层次间的互作效应。结果表明:(1)喀斯特地区森林叶片-凋落物-土壤δ¹³C值分别为-31.31‰～-28.23‰、-29.96‰～-20.07‰、-26.83‰～-21.14‰,相应的δ¹⁵N值依次为-3.41‰～1.54‰、-2.61‰～0.99‰、5.36‰～8.63‰,总体上土壤表现出富集效应。(2)伴随着演替发生,叶片δ¹³C值与土壤δ¹⁵N值均为先减小后增大,土壤、凋落物δ¹³C值呈降低趋势,叶片和凋落物δ¹⁵N值均无明显变化规律。(3)乔灌阶段叶片-土壤δ¹⁵N值最低,表明该阶段生态系统N饱和程度较小,N含量相对亏缺。(4)叶片-土壤C、N及稳定同位素之间相关性较强,表明两者间养分循环紧密相关,具有显著抑制或促进效应。综上认为,该区生态系统修复时,应选择水分利用效率高的川钓樟(Lindera pulcherima)、圆叶乌桕(Triadica rotundifolia)、翅荚香槐(Cladrastis platycarpa)等树种,提高生态系统对资源利用和养分吸收的自调控能力。

Abstract:

To explore the variations and internal relations between the carbon and nitrogen(C and N), and the carbon and nitrogen stable isotope(δ¹³C and δ¹⁵N)with succession proceeding. Four succession stages about forest communities in karst plateau gorge area were selected as the subjects, which were herbage-shrub, shrub, tree-shrub and tree. By measuring C, N and stable isotope ratios in leaf-litter-soil to analyze their interaction effects among different levels. The results were as follows:(1)The δ¹³C values of leaf-litter-soil in karst forest were -31.31‰--28.23‰, -29.96‰--20.07‰, -26.83‰--21.14‰ respectively, and the corresponding δ¹⁵N values were -3.41‰-1.54‰, -2.61‰-0.99‰ and 5.36‰-8.63‰, generally, the soil showed a more enrichment effect.(2)With the succession, the leaf δ¹³C and soil δ¹⁵N values increased first and then decreased, while the soil and litter δ¹³C values decreased, and there were no obvious changing rules about the leaf and litter δ¹⁵N values.(3)The leaf-soil δ¹⁵N values at the tree-shrub stage was the lowest, indicating the stage with low N saturation and relatively deficient N content.(4)The correlations among the leaf-soil C, N and their isotopes were strong, demonstrating that the both cycles were closely relevant with the significant inhibiting or promoting effects. In conclusion, in order to improve the self-regulation ability of the ecosystem to resource utilization and nutrient absorption, the tree species with high water use efficiency, such as Lindera pulcherima, Triadica rotundifolia and Cladrastis platycarpa, should be applied for ecosystem restoration in this area.