三峡库区消落带落羽杉细根碳氮磷化学计量特征及其与土壤养分的关系研究

Ecological Stoichiometric Characteristics of Carbon,Nitrogen,and Phosphorus in the Fine Root of Taxodium distichum and Their Correlation with Soil Nutrients in the Riparian Zone of the Three Gorges Reservoir Region

为了进一步明确落羽杉在消落带的生态适应策略,对三峡库区消落带适生木本植物落羽杉细根C,N,P生态化学计量特征及其与土壤养分间的关系进行了研究.实验样地为重庆市忠县石宝镇汝溪河流域的三峡库区消落带植被修复示范基地,以消落带浅淹(SS,即对照)、中度水淹(MS)、深度水淹(DS)3个处理组的落羽杉(Taxodium distichum)幼林为研究对象,分别测定其植株生长指标、细根(d≤2 mm)元素质量分数(C,N,P)以及对应0~20 cm土壤样品元素质量分数(C,N,P,AN,AP).结果表明:随着水淹时间的延长和水淹强度的增加,落羽杉的株高、冠幅、基径和胸径差异均有统计学意义(p<0.05),结果从大到小依次为:SS组、MS组、DS组;不同的水淹处理对落羽杉细根C,N,P生态化学计量特征的影响不同,MS和DS组的C,N,P质量分数及其比值均与SS组差异有统计学意义(p<0.05);相关性分析表明,细根C质量分数、C∶N、C∶P和N∶P比值与落羽杉的生长指标呈显著或极显著正相关关系,细根N,P质量分数与落羽杉的生长指标呈现显著或极显著负相关关系;除土壤P质量分数与细根P质量分数显著正相关外,土壤养分质量分数与落羽杉细根C,N元素质量分数的相关性无统计学意义或呈负相关关系.实验表明:三峡库区消落带适生植物落羽杉对P元素的需求主要依赖于实生土壤中的P元素,C,N,P元素质量分数和实生土壤养分处于不完全同步的模式.

In order to clarify on the ecological adaptation strategies of suitable riparian restoration woody plants, stoichiometric characteristics of C, N and P in the fine roots as well as the relationships between C, N, P and soil nutrients of Taxodium distichum were studied in the riparian zone of the Three Gorges Reservoir(TGR). The research was carried out in a demonstration base for vegetation restoration in the Three Gorges Reservoir area in Ruxi River Basin, Shibao Town, Zhong County, Chongqing. In this study, young forests of T. distichum were divided into three groups according to the elevation as shallow waterlogging(SS, control), moderate waterlogging(MS), and deep waterlogging(DS). Plant growth indices, element content(C, N, P) in fine roots(d≤2 mm) and element content(C, N, P, AN, AP) of soil samples between 0-20 cm depths were determined. The results showed that the height, crown width, basal diameter and DBH of T. distichum were significantly different with the increase in the duration and intensity of flooding(p<0.05). Different waterlogging treatments i.e., SS group, MS group and DS group had different effects on the C, N and P ecological stoichiometry of fine roots of T. distichum. The C, N and P contents and ratios of MS and DS groups were significantly different from those of the SS group(p<0.05). Correlation analysis showed that C content, C∶N, C∶P and N∶P ratios in the fine roots were significantly positively correlated with the growth indexes of T. distichum. The N∶P contents in fine roots were significantly negatively correlated with the growth indexes of T. distichum. There was no significant negative correlation between soil nutrient content and C and N content in the fine roots of T. distichum, except that P content in soil was significantly positively correlated with the P content in fine roots. The results showed that the demand for P in the water-level-fluctuation zone of the Three Gorges Reservoir area was mainly dependent on P in the growing soil. The contents of C, N and P elements were not completely synchronized with the nutrients in the soils.