Carbon, nitrogen, and phosphorus ecological stoichiometric characteristics in leaves and fine roots of Taxodium distichum in the water-level fluctuation zone of the Three Gorges Reservoir region

Abstract

为探究三峡库区消落带落羽杉（Taxodium distichum（L.） Rich.）叶片与细根C、N、P生态化学计量特征，于2018年7月对忠县三峡库区消落带植被修复示范基地3个水淹处理组（深度水淹组，DS；中度水淹组，MS；浅淹对照组，SS）的落羽杉进行叶片与细根采集，并调查其生长特征，测定分析落羽杉叶片与细根C、N、P生态化学计量特征及相关性.结果表明：（1）各水淹处理组落羽杉叶片C含量表现为SS组 > DS组 > MS组，且SS组显著高于MS组；细根C含量在不同水淹处理组之间均无显著性差异.（2）细根N、P含量表现为DS组 < MS组 < SS组的协同增长趋势；叶片N、P含量则表现为DS组 > MS组 > SS组的协同降低趋势，且叶片N、P含量分别约为细根N、P含量的3倍和2倍.（3）各水淹处理组的叶片C/N、C/P比值均显著或极显著低于细根；叶片N/P比值均高于细根，且其比值相对恒定，均表现为SS组 > DS组 > MS组的趋势.（4）相关性分析表明，叶片P含量与细根N含量呈显著负相关关系，叶片N/P比值与细根N/P比值呈显著正相关关系.研究表明，落羽杉叶片与细根在生长和代谢过程中具有整体性，养分和光合产物在地上与地下部分之间分配权衡，以维持营养的动态平衡，使落羽杉具有内稳性，从而更好地适应和响应三峡消落带水位变化.;To explore the C, N, and P ecological stoichiometric characteristics of leaves and fine roots of Taxodium distichum (L.) Rich in the water-level fluctuation zone of the Three Gorges Reservoir (TGR) region. The C, N, and P content and their ratio in leaves and fine roots of T. distichum in Zhong County under three submergence treatments—Deep Submergence (DS), Moderate Submergence (MS), and Shallow Submergence (SS) were measured and analyzed in July 2018. The results showed that: (1) The C content in leaves of T. distichum showed a trend of SS>DS>MS group, and SS group was significantly higher than that in MS group; there was no difference in C content of fine roots under three submergence treatments. (2) The N and P content in fine roots showed a synergistic growth trend of DS < MS < SS group; the N and P content in leaves showed a cooperative decrease trend of DS>MS>SS group, and the N and P contents of the leaves was about 3 times and 2 times of that in fine roots, respectively. (3) The C/N and C/P ratios of the leaves were significant or extremely significantly lower than those of fine roots in submergence treatment group; the N/P ratio was higher than that of fine roots, and its ratio was relatively constant. Moreover, the N/P ratio between leaves and fine roots showed a trend of SS > DS > MS group. (4) Correlation analysis showed that there was a significant negative correlation between leaf P content and fine root N content, and the leaf N/P ratio was significantly positively correlated with fine root N/P ratio. This work demonstrates that the leaves and fine roots of T. distichum have integrity in the process of growth and metabolism, the nutrients and photosynthetic products are distributed between the above- and below ground parts to maintain the dynamic balance of nutrients, so that the T. distichum has homeostasis and thus adapt well to and respond to changes in the water-level fluctuation zone of the TGR region.