【作者】 杨鑫；

【导师】 刘建全； 马晓军；

【作者基本信息】 兰州大学 ， 生态学， 2008， 硕士

【摘要】 利用外来树种是我国甚至全世界森林生态恢复的重要手段之一,并且对一些地区的林业与生态恢复起到了推动作用。以往对于外来种方面的研究,大多集中于地表植物和动物群落组成和变化,以及生物多样性方面的改变,却常常忽略了广泛存在的外来种对土壤微生物多样性和微生物群落变化的影响。而微生物的群落结构及功能与地表植被紧密相连,是陆地生态系统物质和能量循环的一个重要环节。很多研究表明,地表植被的差异,尤其是引进植物物种会引起土壤微生物多样性及群落组成的改变。但是,引进外来树种日本落叶松在西北小陇山地区是否也影响或改变了土壤细菌多样性,在此之前还未有报道。本实验以甘肃小陇山森林实验站地区原始林砍伐后,对栽培引进外来速生树种(日本落叶松)、乡土树种(油松)和砍伐后自然演替的次生林形成的不同林龄的土壤为对象进行分析,研究不同林龄条件下这三种森林类型土壤理化性质的变化,并采用PCR-DGGE技术比较这三种森林土壤中细菌多样性的差异。结果表明:1.日本落叶松(JL)的土壤除JL-11(11年日本落叶松,pH7.06)外全部为酸性;次生林(NS)和油松(CP)的土壤pH值全部为酸性,其中CP-7(7年油松)最低为5.51,CP-10(10年油松)最高为6.98。所有样地的土壤田间持水量差异显著(P＜0.05),最高的是NS-60(60年次生林),为37.07%;最低为CP-7,为22.31%。田间持水量差异主要是由于该采样地区土壤性质决定,三个林份中林龄越长,其土壤含水量也普遍较高。与此同时,日本落叶松在引种及长期栽种管理后,土壤全氮及土壤有机质含量相比油松有明显增加,其中最高的JL-11(11年日本落叶松)的土壤有机质含量达到了11.86%,高于四个林龄油松3.67%的平均值。2.通过应用变性梯度凝胶电泳(DGGE)技术对比了三种林分的细菌多样性差异,结果显示日本落叶松土壤的主要细菌多样性与其它两个林份条件下的主要细菌多样性比较有一定差异。根据DGGE条带的数目和条带的亮度,计算出10个样品中细菌的Shannon指数。发现除JL-30(30年日本落叶松)外,其余三个林龄日本落叶松的土壤细菌多样性均较低,介于2.76与2.93之间。而次生林土壤中的细菌多样性较高,其中NS-30(30年次生林)中最高,为3.03±0.02。油松土壤中的细菌多样性介于三种林分之间。3.DGGE图谱的PCA和UPGMA分析显示,不同林龄日本落叶松的细菌群落结构较其它两种林分更为相似。对不同林分土壤样品DGGE图谱中标记的各个主要和差异条带切割测序后,得到了19个条带的序列。测序后发现,小陇山地区不同林分的土壤细菌中Proteobacteria(a-、β-、γ-)占主要类群,其总量占测序分析的样品量的68.4%,其次为CFB和高G+C类。实验表明,日本落叶松的引种在当地的确造成了土壤理化性质的改变,也对该地区的土壤细菌多样性产生了一定影响,使其群落组成明显区别于其它两个林分。因此认为,天水小陇山林区日本落叶松的引种会对当地土壤环境产生一定影响。但栽培外来引进树种是否可能导致当地土壤生态系统的改变以及改变的机制,由于本研究仅从土壤细菌群落的多样性方面进行了初步的探讨和分析,并没有深入探讨,所以还有待从其他方面进一步研究。更多还原

【Abstract】 The exotic tree species have been used to restore forest coverage over China and the world. Most previous studies focused on the affects of the exotic species on plant and animal community structure and original biodiversity and the exotic herbal plants were further found to affect the subsoil microbial diversity and function.However,few was made on how the exotic tree species influenced the local soil bacterial biomass or community structure.This study reported the changes of soil characteristics and soil bacterial diversity between the introduced exotic-fast-growth tree species Japan Larch(Larix kaempferi),the original native pine species (Pinus tabuliformis)and the naturally restored secondary forests.Main results are summarized as following.1.Except JL-11(11-year of Japan Larch,pH 7.06),the soils of all remaining samples were acid:the highest one was CP-10(11-year of Chinese Pine),reaching 6.98,and lowest one was CP-7(7-year of Chinese Pine),only 5.51.Significant discrepancy(P＜0.05)was also found in soil water holding capacity between different samples:the highest one was NS-60(60-year of secondary forest),reaching 37.07%,and lowest one was CP-7(7-year of Chinese Pine),only 22.31%.The discrepancy of water holding capacity depended on the soil characteristics of sampling sites:it increased with the forest age growth in three different forest stands.The soil total N and organic contents increased significantly in the Japan Larch if compared with the other two types of stands:the highest one was JL-11(11-year Japan Larch),reaching 11.86%, higher than the average 3.67%of 8,11,18,30 year-old pine stands.2.The PCR-DGGE banding patterns suggested that the main bacterial populations were different between the exotic species and two other stands soils.Based on the presence and the intensity of each band in its profile of each samples,the Shannon-Weaver diversity index(H) was calculated to reflect species richness of the bacterial community:the secondary forest soils have higher bacterial diversity and NS-30(30-year of secondary forest)was the highest (3.03±0.02).All diversity indexes from Japan Larch are lower although JL-30(30-year Japan Larch)has relatively high values between 2.76 and 2.93.The bacterial diversity of the pine soils was between those of the other two forest soils.3.Higher similarities of bacterial community composition were observed within Japan Larch forests of various ages than those in the other two stands,as demonstrated by principal component analysis(PCA)and UPGMA method analysis.Band sequences revealed that the soil bacterial in Xiaolongshan belonged to three divisions,Proteobacteria,CFB and high G+C, among which the most dominant bacterial group was Proteobao(?)eria(a-、β-、γ-).The results suggested that introduced exotic species Japan Larch had effected the soil characteristics and bacterial community structure,made it different significantly with those in two other stands.The exotic species Japan Larch in Xiaolongshan national forest could effect the local soil enverionment.But whether this effect may change the local soil ecosystem,or the mechanism of the possibility for this change,was still unknown and need to be studied further more.更多还原