赣南地区稀土尾矿恢复树种构树根系及根际生理生态适应机制

Broussonetia is a very desirable fast-growing tree for vegetation restoration because of it's perfect stress resistance .However, no reports on the mechanism and the role of ecological restoration of underground ecosystem in Broussonetia are available.It is important for ecological reconstruction to understand the adaptation strategies from the perspective of root and rhizosphere. In the present study, the Broussonetia planted in the abandoned tombarthite mine in South Jiangxi is selected and the following aspects were investigated using field investigation and laboratory determination. 1) To reveal the responses of understory root turnover, root traits, physiological characteristics ,morphology and distribution of the roots to the stress environments using the soil drilling method ,the root window method and WINRHIZO system 2) To study the rhizosphere effect through the analysis of root exudates, rhizosphere microorganisms, soil enzyme activity, phosphorus transformation, Pb and Cd activation to the soil environment using Situ collection, PCR-DGGE method 3) To comprehensively understand the Intrinsic links among roots、 rhizospheres and biomass and nutrient distribution. This project plans to reveal the physiological and ecological adaptation strategies and mechanisms about underground ecosystem of Broussonetia. The results will help understand the excellent stress-resistance of Broussonetia, and provide references to the application for ecological restoration in the mine.

构树抗逆性极强，是矿区植被恢复难得的优良速生乔木树种，但是其地下生态系统在生态恢复中的作用和机理一直未见报道，从根系特征和根际微生态过程探讨构树逆境适应策略具有重要的理论和实践意义。本项目以赣南地区稀土尾矿植被恢复示范树种构树为研究对象,野外试验和实验室测定相结合，采用土钻法、根窗法及生化测定，结合WINRhizo2007系统分析根系形态分布、生长性状和生理特性等对土壤环境的响应；采用原位收集、PCR-DGGE等方法，剖析根际分泌物、根际微生物、土壤酶活性、磷转化、Pb和Cd活化等根际效应对矿区生境的适应性反应；结合生物量和养分积累及分配差异，综合分析根系特征和根际微生态过程之间的内在联系，揭示构树地下部分对稀土尾矿生理生态适应策略和适应机制。研究结果有助于进一步认识构树的优良抗逆性能，为构树在矿区等困难立地植被恢复应用提供科学依据和理论指导。

本研究应用构树对赣南稀土尾矿进行生态修复，探讨了根系的形态特征、生理特性、根际过程、土壤微生物和酶活性对尾矿环境的响应。结果表明，根系通过调整细根比例，增加比根长和总比表面积增强吸收能力；通过LC-MS分析检测到1968种代谢产物发生显著变化，糖类、有机酸、葫芦巴碱等对构树应对稀土尾矿环境压力起了实质性的贡献；稀土尾矿环境能够促进构树根系分泌酸类、烃类、酮类、醇类、酰胺类、酚类、苯类等，其中酸类的相对含量最高，达55.36%；通过外源添加有机酸表明根系分泌物显著提高了尾矿土壤微生物的数量和酶活性；构树根系脯氨酸等渗透调节物质和抗氧化物酶活性对尾矿胁迫因子产生响应，主成分分析显示贡献率依次是脯氨酸、根系活力、POD、SOD 、CAT、溶性糖、可溶性蛋白；16sDNA分析表明植被修复后，稀土尾矿土壤微生物群落结构发生了明显变化，且微生物多样性、均匀度、丰富度与未修复尾矿土壤相比均有了明显的提高，分析表明土壤微生物与根际土壤养分、土壤酶显著相关。综合分析表明，构树一方面调整地下生长，一方面通过改变根际分泌物组成和含量，提高微生物多样性，激发酶的活性共同适应困难逆境。研究结果从地下生态系统揭示了构树的抗逆机制，为构树在矿区等困难立地生态恢复提供了理论基础。