| 摘要 | 第4-7页 |
| Abstract | 第7-9页 |
| Chapter 1: General introduction | 第13-28页 |
| 1.1 Background and problems | 第13-15页 |
| 1.2 State of the art | 第15-26页 |
| 1.2.1 Root definition and functions | 第16-17页 |
| 1.2.2 The Growth, Lifespan, and Death of Root | 第17-18页 |
| 1.2.3 Factors influencing belowground production | 第18-21页 |
| 1.2.4 Methods in root research | 第21-25页 |
| 1.2.5 Land use practices and grassland restoration | 第25-26页 |
| 1.3 Objectives and skeleton diagram of the thesis | 第26-28页 |
| Chapter 2: Materials and methods | 第28-46页 |
| 2.1 Experimental sites | 第28-34页 |
| 2.1.1 General description | 第28-30页 |
| 2.1.2 Study site | 第30-34页 |
| 2.2 Methods | 第34-44页 |
| 2.2.1 Plant samples collection | 第34-41页 |
| 2.2.2 Soil sample determination | 第41-44页 |
| 2.3 Data analysis | 第44-46页 |
| Chapter 3: The combination of litter amount and seeding accelerates the restoration ofbelowground net primary production in degraded Songnen grassland | 第46-59页 |
| 3.1 Introduction | 第46-47页 |
| 3.2 Results | 第47-54页 |
| 3.2.1 Weather variability | 第47-48页 |
| 3.2.2 Soil moisture content | 第48-50页 |
| 3.2.3 ANPP, BNPP and NPP | 第50-52页 |
| 3.2.4 Root fraction (f_(BNPP)) | 第52-53页 |
| 3.2.5 Correlation comparison | 第53-54页 |
| 3.3 Discussion | 第54-58页 |
| 3.3.1 Effects of litter and seeding on soil moisture content | 第54-55页 |
| 3.3.2 The effects of litter and seeding on ANPP and BNPP | 第55-57页 |
| 3.3.3 Effects of litter and seeding on root fraction | 第57-58页 |
| 3.4 Conclusion | 第58-59页 |
| Chapter 4: Tillage and clipping aboveground litter practices increased belowground netprimary productivity and root fraction in Songnen grassland | 第59-74页 |
| 4.1 Introduction | 第59-60页 |
| 4.2 Results | 第60-68页 |
| 4.2.1 Soil moisture content (SMC) | 第60-62页 |
| 4.2.2 Aboveground net primary production (ANPP) and net primary production (NPP) | 第62-64页 |
| 4.2.3. Belowground net primary production (BNPP) and root fraction (f_(BNPP)) | 第64-65页 |
| 4.2.4 Soil organic matter (SOM) | 第65-66页 |
| 4.2.5. Correlation comparisons | 第66-68页 |
| 4.3 Discussion | 第68-73页 |
| 4.3.1 Soil moisture and management practices | 第68-69页 |
| 4.3.2 ANPP and management practices | 第69-70页 |
| 4.3.3 BNPP and management practices | 第70-71页 |
| 4.3.4 Root fraction (f_(BNPP)) and management practices | 第71-72页 |
| 4.3.5 Soil organic matter (SOM) and management | 第72-73页 |
| 4.4 Conclusion | 第73-74页 |
| Chapter 5:Clipping aboveground litter lead to enhance fine root production, mortality,turnover and fine root lifespan along artificial and natural management of degradedSongnen grassland | 第74-89页 |
| 5.1 Introduction | 第74-76页 |
| 5.2 Results | 第76-84页 |
| 5.2.1 Seasonal dynamics of fine root production, mortality and standing crop | 第76-77页 |
| 5.2.2 Belowground net primary production (BNPP) | 第77-78页 |
| 5.2.3 Root productivity, mortality, and mean standing crop | 第78-80页 |
| 5.2.4 Annual root turnover | 第80-81页 |
| 5.2.5 Correlation between soil moisture and root production, mortality, turnover | 第81-82页 |
| 5.2.6 Response of root lifespan of different soil profiles to land-use management | 第82-84页 |
| 5.3 Discussion | 第84-88页 |
| 5.3.1 Seasonal dynamics of root productivity, root mortality and standing crop | 第84-85页 |
| 5.3.2 Fine root production, mortality and standing crop | 第85-86页 |
| 5.3.3 Fine root turnover and lifespan | 第86-88页 |
| 5.4 Conclusion | 第88-89页 |
| Chapter 6: Relationship between species distribution patterns and soil salinity in Songnen grassland | 第89-98页 |
| 6.1 Introduction | 第89-90页 |
| 6.2 Results | 第90-94页 |
| 6.2.1 Soil pH, EC, Soil N and SOM | 第90-91页 |
| 6.2.2 Aboveground biomass and relative biomass | 第91-92页 |
| 6.2.3 Correlation comparisons | 第92-94页 |
| 6.3 Discussion | 第94-97页 |
| 6.3.1 Patch Size and Genesis | 第94-95页 |
| 6.3.2 Relationship between Species Distribution Patterns and Soil Salinity | 第95-97页 |
| 6.4 Conclusion | 第97-98页 |
| Summary and conclusions | 第98-103页 |
| 总结和结论 | 第103-107页 |
| References | 第107-122页 |
| Acknowledgement | 第122-123页 |
| Dedication | 第123-124页 |
| Papers published and under process | 第124页 |
