不同群落类型下南方铁杉金属元素含量差异及其与土壤养分因子的关系

Metal element contents of Tsuga chinensis var.tchekiangensis in different community types and its relationship with soil nutrient factors in eastern China

在九龙山国家级自然保护区内,针对濒危植物南方铁杉(Tsuga chinensis var.tchekiangensis)的分布特点,设置了40个具有代表性的样地。采用群落分类的双向指示种分析法(TWINSPAN)进行群落类型的划分,并在此基础上,研究了不同群落类型下南方铁杉植株和土壤中金属元素的含量差异及其与土壤养分因子的关系。结果表明:1)TWINSPAN分类将九龙山南方铁杉群落分为5种类型,代表5种不同生境和物种组成的群落类型。2)不同群落类型下南方铁杉植株和土壤中的金属元素存在一定的差异,在群落类型II和V中,植株金属元素总量相对较高,且K、Ca、Fe、Mg、Ba和Cr6种元素含量也较高,大部分土壤金属元素以群落类型II为最高。3)不同金属元素在南方铁杉植株和土壤中的含量具有很大差异,植株中Ca、K、Mg、Fe和Mn含量较高,土壤中Al和Fe的含量较高。4)南方铁杉不同器官金属元素的含量存在一定的差异,各元素在不同器官中的排列顺序和变异程度不一致。5)富集系数和相关性分析表明,南方铁杉对Mg和Zn的吸收具有相似性,对Fe和Al的吸收也相似。6)南方铁杉植株的大多数金属元素与土壤金属元素没有相关性,究其原因可能是植株元素虽主要来源于土壤,但受植物种类和生长发育状况、林地土壤类型、肥力及pH等因素的影响。

Aims Tsuga chinensis vat. tchekiangensis is a species with a small geographic distribution in the subtropical forests in eastern China. The species has been listed as Chinese national third protective plant. Our objective was to investigate the differences and correlations of metal element contents in plant and forest soil of T. chinensis var. tchekiangensis in different community types in Jiulongshan Nature Reserve, Zhejiang Province, China. Findings will provide a scientific basic for feasible in situ and ex situ conservation of the species. Methods Forty representative plots （10 m ×10 m） were investigated along different ridges from low to high altitude. The community types of these plots were identified, and the groups of tree relationships were established based on TWINSPAN. Twelve metal elements of root, stem, bark and leaf of T. chinensis var. tchekiangensis samples and forest soil were measured by ICP-AES. Soil factors such as pH, water content, organism content and electrical conductivity were also measured. Differences of metal element contents were analyzed among different community types and organs. The correlation among different metal element contents of T. chinensis var. tchekiangensis and soil nutrient factors were analyzed and compared. Important findings Based on the investigations and results of TWINSPAN classification, the plots were classified into five communities. Differences among metal element contents of plant and soil in different community types were determined. The contents of plant elements such as K, Ca, Fe, Mg, Ba and Cr were higher in community Ⅱ and Ⅴ, and most soil elements were highest in community II. The content of Ca, K, Mg, Fe and Mn were higher in plant, and Al and Fe were higher in soil. The content of metal elements among different organs was different, and their change tendencies and variation degrees were discordant. Enrichment coefficient and correlation analysis showed that the absorption of Mg and Zn, as well as Fe and Al by T. chinensis var. tchekiangensis was similar; however, most plant elements had no correlation with soil elements.