三峡库区消落带池杉-土壤碳氮磷生态化学计量特征

为探究三峡库区消落带消落期池杉(Taxodium ascendens Brongn., 1833)及其实生土壤C、N、P生态化学计量特征,于2018年7月对忠县消落带植被修复示范基地3个水淹处理(DS、MS、SS)池杉幼林不同组分(枝条、叶片、根系和土壤)的C、N、P三种元素含量及其化学计量比进行测定分析。结果表明:(1)随着水淹时间和强度的增加,池杉株高、冠幅、基径和胸径均受到一定的抑制,但总体生长良好,与其稳定的化学计量比关系紧密。(2)不同水淹处理组的池杉枝条、叶片中C、N、P含量及其比值分别均无显著性差异(P0.05)。同一水淹处理组的N、P含量表现为叶片根系枝条土壤;除枝条P含量外,其他器官组分C、N、P含量均显著高于土壤组分(P0.05)。(3)池杉各器官N/P比值均远低于临界比率(14),表明池杉的生长可能受N元素限制较为严重。(4)池杉与实生土壤的C、N、P元素内稳性整体表现为PCN,比值内稳性表现为C/NN/PC/P,地上部分(枝条、叶片)C、N、P元素及其比值的稳定性较地下部分(根系)强。(5)冗余分析(RDA)结果表明池杉生态化学计量特征及生长指标与土壤性质密切相关。研究表明,在三峡库区消落带水文多变的环境下,池杉能够有效维持体内化学计量的平衡以响应不同的水淹强度,并且生长良好,是三峡库区消落带植被恢复与重建的优势树种。

Carbon, nitrogen, and phosphorus ecological stoichiometric characteristics between Taxodium ascendens and soil in the water-level fluctuation zone of the Three Gorges Reservoir region

The present study investigated differences in the C, N, and P ecological stoichiometric characteristics of Taxodium ascendens Brongn. and soil in the water-level fluctuation zone of the Three Gorges Reservoir (TGR) region. The C, N, and P contents and stoichiometry in different parts (branches, leaves, and roots) of T. ascendens and in the soil in Zhong County under three submergence treatments (Deep Submergence, DS; Moderate Submergence, MS; and Shallow Submergence, SS) were measured and analyzed in July 2018. (1) The height, canopy, basal diameter, and DBH of T. ascendens were all inhibited by increasing flooding time and intensity, whereas growth was maintained, possibly due to the tree''s stable stoichiometric ratio. (2) Submergence treatment had no significant effect on the C, N, or P contents or ratios of the branches or leaves (P>0.05), and the N and P contents decreased as follows: leaves > roots > branches > soils, under each submergence treatment. The C, N, and P content of other organs were significantly greater than those in the soils, except for the P content of the branches (P<0.05). (3) The N/P ratio of each T. ascendens organ was much lower than the threshold (<14), which suggested that the growth of T. ascendens is more severely restricted by N. (4) The homeostasis of the C, N, and P contents of T. ascendens and soil decreased as follows: P > C > N, and the homeostasis ratios decreased as follows: C/N > N/P > C/P. The homeostasis of C, N, and P in the aboveground parts (branches and leaves) and their ratios were much higher than that in underground parts (roots). (5) Redundancy analysis (RDA) indicated that the ecological stoichiometry and growth indicators of T. ascendens were closely related to soil properties. This work demonstrates that T. ascendens is able to grow well and to effectively maintain the stoichiometry balance in response to different flooding strengths that result from hydrological changes in the water-level fluctuation zone of the TGR region. In other words, T. ascendens is a potentially promising tree species for vegetation restoration and reconstruction in the water-level fluctuation zone of the TGR region.