喀斯特灌丛群落豆科植物共生固氮资源调查及根瘤菌多样性研究
摘要
我国喀斯特地区石漠化严重,生态系统严重退化,是我国急需治理的生态脆弱区之一。该地区氮素在耕作和退化土壤中流失严重,使其成为植被恢复过程的重要限制性因素之一。豆科植物能明显改善土壤结构和营养状况,并能改善土壤微环境,为其他植物的迁移、定居、生长创造条件,从而促进退化生态系统植被演替与恢复。但到目前为止,对喀斯特地区豆科植物及其共生根瘤菌资源调查还很少,根瘤菌的区域特异性及其生态效应还不清楚。另外,退化生态系统恢复与石漠化治理过程中,灌丛演替阶段的生态意义重大。石漠化灌丛是轻、中、重度等各石漠化程度生境上分布面积最大的一类植被,是退化生态系统恢复过程中极其重要的转折阶段。从灌丛阶段开始,生态系统水土流失等退化过程基本停止,土壤肥力、物种多样性显著提高,恢复过程逐步加强。对喀斯特地区灌丛群落开展豆科植物及其共生根瘤菌资源调查与根瘤菌多样性研究,有利于加深对该地区豆科植物及其根瘤菌共生资源多样性与特异性的认识,并为筛选出能适应喀斯特退化生境的先锋豆科植物-高效固氮根瘤菌组合提供技术指导,为豆科植物在喀斯特地区生态恢复与重建中的应用提供理论依据与实践支持。本文对喀斯特地区的25块灌木样地进行植被调查和豆科植物结瘤调查,并对分离的根瘤菌构建了16S rDNA与nifH系统发育树,主要结论如下：
1.样地共有植物81科,172属,218种。其中最大的科为豆科,有13属,16种。豆科植物占总属的7.56%,占总种数的7.34%。灌丛群落灌木层优势种为檵木、黄荆和豹皮樟；草本层优势种为翠云草、肾蕨和苔草。相比群落优势种,豆科植物在灌丛群落的重要值均很小。其中,西南杭子梢、香合欢、藤黄檀的重要值稍大。
2.16种豆科植物中,共发现7种植物结瘤。其中,蝶形花亚科6种,含羞草亚科1种,云实亚科未发现结瘤。根瘤大多数着生在侧根上,少数着生在主根上；形态多为球状、棒状,少数为珊瑚状；表面皮层厚,颜色多为土黄色或褐色。
3.总共分离出7种菌株,菌株在YMA平板上的菌落形态为透明或半透明,白色或乳白色,凸起,边缘光滑,有荚膜产生。对分离的根瘤菌进行16S rDNA与nifH序列测序,参照根瘤菌相关的标准菌株,构建供试菌株与标准菌株的系统发育树。对16SrDNA与nifH系统进化树分析发现,分离自不同植物的7种根瘤菌均属于慢生根瘤菌属(Bradyrhizobium),但根据16S rRNA基因与nifH构建的系统进化树之间存在差异。在根据16S rDNA序列构建的系统发育树中,7种菌株分别与B.canariense和B.pachyrhizi聚在一起；在根据nifH构建序列构建的系统发育树中,7种菌株分别与B.canariense、B.pachyrhizi与B.jicamae聚在一起。
The rocky desertification of Karst region is serious and the ecosystem becomes serious degradation. The Karst region is one of the ecologically fragile areas in China, which is urgent to-treatment. In the region, nitrogen drain is serious in farming and degraded soils, which makes nitrogen becoming one of the important limiting factor to recover the vegetation. Legumes can significantly improve the structure of the soil, nutritional status, and the microenvironment of the soil, which can create the conditions for other plants migration, settlement and growth. Thus it can promote the succession and restoration of degraded ecosystem. But so far, the survey of the Karst areas about leguminous plants and their symbiotic rhizobial resources is little, the regional specificity of rhizobium and its ecological effect is unclear. In addition, during the restoration of degraded ecosystems and in the processing of controlling the rocky desertification, the shrub community stage is important. The area of shrub communities is largest on the light, moderate and severe degree of rocky desertification region. The erosion of soil and other degradation processes in ecosystems stop, and the fertility of soil and the diversity of species increase significantly, and the recovery ability of shrub community gradually strengthen on the stage of shrub communities. The research about the legumes and their symbiotic rhizobial resource in Karst areas can helps us to deepen the understanding of the diversity of the regional legumes and the specificity of and rhizobia symbiosis resource. It can provide the technical guidance for selecting the pioneer legumes-efficient nitrogen-fixing rhizobium combinations which can adapt to Karst degraded ecosystem, and provide a theoretical basis for the application of leguminous plants to Karst ecological recovery and reconstruction.
In this research, we investigated the vegetation of25shrub communties and collected the nodules of legume plants in Karst shrub communities, then constructed the phylogenetic trees based on16S rDNA and nifH sequences of the rhizobia. The main results of my research were shown as following:
There are81families,172genera,218species of plants in plots. The largest family is Leguminosae. In shrub layer, the dominant species of shrub communities are Loropetalum chinense, Vitex negundo, Litsea coreana var. sinensis. In herbaceous layer, the dominant species of shrub communities are Selaginella uncinata, Nephrolepis cordifolia, Carex tristachya. Compared to the dominant species, the important values of legume plants are very small. Of sixteen legume plants,
Six species of Fabaceae and one species of Mimosaceae can nodulate in total sixteen legume species. The forms of the most nodules are spherical or rod-like. The color of the most nodules is khaki or brown. The most nodules grow on the lateral roots. Seven strains are isolated. The colony morphology of the strains in YMA are transparent or translucent, white or milk white, convex, edge smooth. The strains are Gram negative strains.The phylogenetic trees based on16S rDNA and nifH sequences are constructed by neighbour-joining method. All of the seven strains belong to Bradyrhizobium, but there are some differences between the phylogenetic trees based on16S rDNA and nifH sequences.
1.样地共有植物81科,172属,218种。其中最大的科为豆科,有13属,16种。豆科植物占总属的7.56%,占总种数的7.34%。灌丛群落灌木层优势种为檵木、黄荆和豹皮樟；草本层优势种为翠云草、肾蕨和苔草。相比群落优势种,豆科植物在灌丛群落的重要值均很小。其中,西南杭子梢、香合欢、藤黄檀的重要值稍大。
2.16种豆科植物中,共发现7种植物结瘤。其中,蝶形花亚科6种,含羞草亚科1种,云实亚科未发现结瘤。根瘤大多数着生在侧根上,少数着生在主根上；形态多为球状、棒状,少数为珊瑚状；表面皮层厚,颜色多为土黄色或褐色。
3.总共分离出7种菌株,菌株在YMA平板上的菌落形态为透明或半透明,白色或乳白色,凸起,边缘光滑,有荚膜产生。对分离的根瘤菌进行16S rDNA与nifH序列测序,参照根瘤菌相关的标准菌株,构建供试菌株与标准菌株的系统发育树。对16SrDNA与nifH系统进化树分析发现,分离自不同植物的7种根瘤菌均属于慢生根瘤菌属(Bradyrhizobium),但根据16S rRNA基因与nifH构建的系统进化树之间存在差异。在根据16S rDNA序列构建的系统发育树中,7种菌株分别与B.canariense和B.pachyrhizi聚在一起；在根据nifH构建序列构建的系统发育树中,7种菌株分别与B.canariense、B.pachyrhizi与B.jicamae聚在一起。
The rocky desertification of Karst region is serious and the ecosystem becomes serious degradation. The Karst region is one of the ecologically fragile areas in China, which is urgent to-treatment. In the region, nitrogen drain is serious in farming and degraded soils, which makes nitrogen becoming one of the important limiting factor to recover the vegetation. Legumes can significantly improve the structure of the soil, nutritional status, and the microenvironment of the soil, which can create the conditions for other plants migration, settlement and growth. Thus it can promote the succession and restoration of degraded ecosystem. But so far, the survey of the Karst areas about leguminous plants and their symbiotic rhizobial resources is little, the regional specificity of rhizobium and its ecological effect is unclear. In addition, during the restoration of degraded ecosystems and in the processing of controlling the rocky desertification, the shrub community stage is important. The area of shrub communities is largest on the light, moderate and severe degree of rocky desertification region. The erosion of soil and other degradation processes in ecosystems stop, and the fertility of soil and the diversity of species increase significantly, and the recovery ability of shrub community gradually strengthen on the stage of shrub communities. The research about the legumes and their symbiotic rhizobial resource in Karst areas can helps us to deepen the understanding of the diversity of the regional legumes and the specificity of and rhizobia symbiosis resource. It can provide the technical guidance for selecting the pioneer legumes-efficient nitrogen-fixing rhizobium combinations which can adapt to Karst degraded ecosystem, and provide a theoretical basis for the application of leguminous plants to Karst ecological recovery and reconstruction.
In this research, we investigated the vegetation of25shrub communties and collected the nodules of legume plants in Karst shrub communities, then constructed the phylogenetic trees based on16S rDNA and nifH sequences of the rhizobia. The main results of my research were shown as following:
There are81families,172genera,218species of plants in plots. The largest family is Leguminosae. In shrub layer, the dominant species of shrub communities are Loropetalum chinense, Vitex negundo, Litsea coreana var. sinensis. In herbaceous layer, the dominant species of shrub communities are Selaginella uncinata, Nephrolepis cordifolia, Carex tristachya. Compared to the dominant species, the important values of legume plants are very small. Of sixteen legume plants,
Six species of Fabaceae and one species of Mimosaceae can nodulate in total sixteen legume species. The forms of the most nodules are spherical or rod-like. The color of the most nodules is khaki or brown. The most nodules grow on the lateral roots. Seven strains are isolated. The colony morphology of the strains in YMA are transparent or translucent, white or milk white, convex, edge smooth. The strains are Gram negative strains.The phylogenetic trees based on16S rDNA and nifH sequences are constructed by neighbour-joining method. All of the seven strains belong to Bradyrhizobium, but there are some differences between the phylogenetic trees based on16S rDNA and nifH sequences.
引文
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