【作者】 张超；

【导师】 刘国彬； 薛萐；

【作者基本信息】 中国科学院研究生院（教育部水土保持与生态环境研究中心） ， 生态学， 2013， 博士

【摘要】 根际是指根系周围、受根系生长影响的土体，由于其环境的特殊性，根际土壤的研究已经成为植物营养学、生态学及土壤学等学科的热点，鉴于我国在黄土高原植被恢复方面对根际环境尚未全面系统地开展研究工作，本研究选取黄土丘陵区坡耕地退耕后的不同植被恢复类型和撂荒演替初级阶段的主要植被群落为研究对象，采用磷脂脂肪酸图谱技术（PLFA）和碳素利用技术（BIOLOG）系统研究了根际微生物对植被恢复的响应过程，重点分析了不同植被类型对根际微生物量、酶活性、微生物群落结构和代谢功能特征的影响以及撂荒演替过程中根际微生物群落结构的演变特征，以期为深入认识该区植被恢复中土壤微生物的作用机理提供科学依据。主要结果如下：1.不同植被恢复类型根际微生物特征黄土丘陵区退耕地六种植被恢复类型中（年限均为8年），相对于人工灌木（柠条、沙棘）和人工草地（沙打旺、柳枝稷），自然形成的天然草地（阿尔泰狗娃花、茵陈蒿）具有较高的根际有机碳、全氮、微生物量碳、微生物量氮、酶活性、微生物群落结构多样性以及碳源代谢功能多样性。微生物指标中，代谢熵、脲酶、基础呼吸、水溶性碳及纤维素酶可作为评价黄土丘陵区根际土壤生物质量的关键指标。结合标准化模型，建立了根际土壤生物质量指标体系及评价方法，提出了根际微生物指数，结果表明，天然草地对根际土壤生物质量的改善效果最佳，其次是人工草地，最后是人工灌木。不同植被类型中，天然草地的根际效应（根际>非根际）较为广泛，主要体现在有机碳、全氮、微生物量碳、微生物量氮、基础呼吸、过氧化物酶、革兰氏阴性菌、细菌、真菌以及微生物总量。2.撂荒演替过程中根际微生物的演变特征黄土丘陵区退耕地撂荒演替过程中，有机碳、全氮、微生物量碳、微生物量氮、基础呼吸和酶活性具有较强的根际效应。群落优势种根际微生物指标并非都高于伴生种，其优势主要体现在有机碳、全氮、微生物量碳、微生物量氮以及糖类碳源利用效率，而在微生物群落结构、酶活性以及羧酸类碳源利用效率上并未表现出优势。演替前期的植物茵陈蒿群落根际微生物性质波动较为强烈，而中后期铁杆蒿变化规律性较强，总体随退耕年限呈增加趋势。3.人工模拟撂荒演替根际微生物群落结构特征黄土丘陵区撂荒演替中不同阶段的优势种植物茵陈蒿、铁杆蒿和长芒草革兰氏阴性菌、细菌含量和微生物总量根际效应显著，表现为距离根系越近，微生物含量越高。在相同条件下，演替中后期植物铁杆蒿和长芒草的细菌和微生物总量的根际效应大于前期植物茵陈蒿，而革兰氏阳性菌和真菌根际效应低于茵陈蒿。在植被竞争中，前期植物茵陈蒿和中后期植物铁杆蒿、长芒草的根际微生物群落对竞争的反应不同，表现为三者相互竞争时，茵陈蒿的根际微生物种类未发生变化，铁杆蒿和长芒草则显著降低；茵陈蒿的根际微生物含量显著高于铁杆蒿和长芒草。4.撂荒演替中不同群落优势种植物之间化感作用种子萌发试验表明，不同演替阶段的群落优势种茵陈蒿、铁杆蒿和长芒草相互之间其高浓度浸提液不仅对对方的种子萌发具有抑制作用，而且对自身种子萌发也具有一定自毒作用。黄土丘陵区退耕地撂荒演替过程中植物之间存在化感作用，这种群落间的化感作用可能是推动植被演替的原因之一。更多还原

【Abstract】 Rhizosphere is commonly defned as the soils where the root activity signifcantlyaffects the biological properties of soil. Due to the special environment, the rhizospheremicro-zone has become one of hot topic for the plant nutrition, plant physiology, ecologyand soil science. Because the lack of the available and comprehensive work on therhizosphere soils in the hilly loess region, the present study chose the different revegetationtypes and the vegetation community in the natural succession on the abandoned croplandto analyze the response of rhizosphere soil microorganism to the revegetation usingphospholipid fatty acids and BIOLOG carbon utilization technology. The study mainlyinvestigated the effect of revegetation types on rhizosphere soil microbial biomass,enzymes activities, microbial community structure diversity and metabolic functionaldiversity as well as the dynamic of microbial community structure diversity during theabandoned cropland for natural succession. The results could provide scientific basis forthe understanding of microbial function during the vegetation restoration. The main resultsare as follows:1. The characteristic of rhizosphere microbial properties under differentrevegetation typesSix vegetation types with8-year-old were evaluated: two artificial (i.e. planted byhumans) shrublands (Caragana korshinskii and Hippophae rhamnoides) species, twoartifcial grasslands (Astragalus adsurgens and Panicum virgatum) and two species fromcroplands that were abandoned for natural recovery (Artemisia capillaries andHeteropappus altaicus). The results showed the higher value of organic C, total N,available Mn, available Cu, available Zn, microbial biomass C, microbial biomass N,enzymes activities, microbial community structure diversity and carbon resource metabolicfunctional diversity was record for the natural grassland compared to the artificial shrublands and artificial grassland.Among the microbial properties, metabolic quotient (BR/MBC), BR, urease,water-soluble C and cellulase were found to be most important for assessing rhizospheresoil biological quality. Results of rhizosphere soil microbial index indicated that naturalgrasslands are most effective for the improvement of rhizosphere soil biological quality inthe hilly loess region, followed by the artificial grassland and artificial shrubland.A significant difference was found on the rhizosphere effect under the differentvegetation types. Natural grassland species have the significant rhizosphere effect than theartificial shrubland and artificial grassland.2. The dynamic of rhizosphere microbial properties during the abandonedcropland for natural succession.During the natural succession, the significant rhizosphere effect was only found inorganic C, total N, microbial biomass C, microbial biomass N, basal respiration, enzymesactivities and microbial community structure.Not all the microbial properties in the rhizosphere soil of dominant species werehigher than those of companion species. The higher value in the rhziosphere of dominantspecies was found in organic C, total N, microbial biomass C, microbial biomass N as wellas the metabolic on carbohydrate resources than that of companion species, while in theenzymes activities and the metabolic on carboxylic acids, the dominant species did notshowed the higher value.The successional stage of the ecosystem can significantly affect the microbialproperties in the plant rhizosphere. In the current study, the pioneer species, A. capillaries,exhibited significant fluctuations in the microbial properties, whereas the middle-latespecies, A. sacrorum, presented an increasing trend.3. The characteristics of rhizosphere microbial community structure in thenatural succession simulationThree community dominant species of the succession, A. capillaries, A. sacrorum andS. bungeana showed the significant microbial rhizosphere effect in G-negative bacterial,bacterial and total microbial biomass, their contents decreased with the increase of distancefrom root surface.At the same soil conditions, the middle-late successional species, A. sacrorum and S. bungeana had a higher rhizosphere effect of bacterial and total microbial biomass whilehad the lower G-positive bacterial and fungi rhizosphere effect than that of the pionnerspecies, A. capillaries,In the successional vegetation competition, the microbial community structurerhizosphere soil of A. capillaries and A. sacrorum and S. bungeana responded differentlyto the competition. In the competition between A. capillaries and A. sacrorum, as well asbetween A. capillaries and S. bungeana, the number of microbial PLFA of A. capillariesdid not change, while that of A. capillaries and S. bungeana decreased significantly.Furthmore, the microbial contents in the rhizopshere soil of A. capillaries was greatlyhigher than that of A. capillaries and S. bungeana.4. Allelopathic effect of dominant plants of vegetation commnutiy during theabandoned cropland for natural successionIn the seed germination experiment, an inhibition was found on the seed germinationof A. capillaries, A. sacrorum and S. bungeana with each other in their high concentrationof aqueous extracts. Furthermore, a self-allelopathic effect was observed for the seedgermination of A. capillaries. In conclusion, there is a significant alleopathic effectbetween vegetation communities during the abandoned cropland for natural succession,this effect maybe the one of the reseaons for promoting the vegetation succession in theloess hilly region.更多还原