三峡库区消落带水位变化对落羽杉C、N、P生态化学计量特征的影响

为了解落羽杉C、N、P生态化学计量特征对三峡库区消落带水位变化的响应,2016年9月测定重庆市忠县汝溪河消落带植被修复示范基地内种植于海拔165 m(重度水淹组)、170 m(中度水淹组)、175 m(对照组)的落羽杉根、枝条、叶片中碳(C)、氮(N)、磷(P)元素含量以及植株生长指标,分析水位变化对其生长和C、N、P生态化学计量特征的影响。结果表明:(1)三峡库区消落带落羽杉通过降低生长速率来适应水位变化,植株整体生长状态良好;(2)落羽杉各器官C含量分配比较均衡,N集中在叶片中,P主要贮存在根中,未见严重缺素现象;(3)重度水淹组植株叶片C含量受到水位变化显著提高;水位变化显著降低了中度水淹组植株根P含量却显著提高了其叶片P含量,导致中度水淹组植株叶片C∶P和N∶P显著降低,根C∶P显著升高。研究结果表明,三峡库区消落带落羽杉能保持器官之间合理的元素分配来保障其生长所需,表现出对三峡库区消落带水位变化的良好适应性。

Effects of water-level changes in the hydro-fluctuation zone of Three Gorges Reservoir on carbon, nitrogen and phosphorus stoichiometry of Taxodium distichum

After completion of the Three Gorges Dam, its special hydrological scheduling caused the extinction of some original plants in hydro-fluctuation zone of Three Gorges Reservoir (TGR). It also led to the ecological and environmental problems including soil erosion, biodiversity loss, landslide, collapse and so on. The suitable plants selection for vegetation reconstruction is considered as one of the effective methods to solve these problems. The previous study has been proved that Taxodium distichum was a good choice for vegetation reconstruction in the TGR. In March 2012, we selected the section at an altitude of 165 to 175 meters above sea level. According to the hydrological characteristics of the TGR, two-year-old T. distichum that grew evenly at a row spacing of 1 meter multiplying 1 meter were planted in Ruxi River vegetation reconstruction demonstration base. After four years of in-situ flooding cycle, T. distichum showed good adaptability. In order to further understand its adaptive mechanism to the water-level changes in the TGR, the leaf, branch and root samples were collected from control check (CK; 175 m ASL), moderate submergence (MS; 170 m ASL), and deep submergence (DS; 165 m ASL) in mid-September 2016 before impoundment of TGR. The contents of carbon (C), nitrogen (N), and phosphorus (P) in the roots, branches, and leaves were determined. The effects of water-level changes on C, N and P stoichiometry and growth were analyzed. The results showed that:(1) In the TGR, T. distichum reduced the growth rate to adapt water-level changes. The overall growth state of the plants was good. (2) The distribution of C content in various organs of T. distichum was relatively balanced. N was concentrated in the leaves and P was mainly stored in the roots. There was no serious lack of elements. (3) The water-level changes significantly increased the leaf C content of DS group plants. The water-level changes significantly reduced the root P content of the MS group plants, but significantly increased the leaf P content. Those resulted in C:P and N:P ratios of leaf in the MS group plants decreased significantly and the root C:P increased significantly. The results indicated that T. distichum in hydro-fluctuation zone of the TGR could maintain a reasonable elemental distribution among organs to ensure their growth needs, showing good adaptability to the water-level changes.