This work is dedicated to my parents Rainer and Anne Blasum , my parents-in-law Liu Chengzhi and Sun Aifang and to my wife Liu Yunmei.

• Abstract

• 1. Background for legume N fixation research in a cold grassland area
• 1.1. Physiology of general N fixation and the legume-rhizobium symbiosis
• 1.1.2. Particulars of the legume system
• 1.1.2.1. Symbiotic patterns
• 1.1.2.2. Different legumes often need different rhizobia
• 1.1.2.3. How different legumes recognize different rhizobia
• 1.2. Xiaman experimental site
• 1.2.1. Location on the Qinghai-Tibet plateau
• 1.2.2. Xiaman environment
• 1.2.2.1. Relief and climate
• 1.2.2.2. Soil and vegetation
• 1.3. Ecology of leguminous nitrogen fixation
• 1.3.1. Population dynamics
• 1.3.2. Habitat-dependent efficiency: crops and pastures
• 1.3.3. Temperature
• 1.3.4. Acidity
• 1.3.5. Soil nutrients
• 1.4. Research methods
• 1.4.1. Determining overall legume quantity and distribution
• 1.4.2. Assessing N fixation
• 1.4.2.1. Direct approach: ARA
• 1.4.2.2. Indirect approach: N labeling and depletion studies
• 1.4.3. Assessing N demand
• 1.4.4. Inoculation techniques
• 1.4.4.1. Isolation and maintenance of rhizobia
• 1.4.4.2. Identification of rhizobia
• 1.4.4.2.1. Phenetic assays
• 1.4.4.2.1.1. Host-plant assay
• 1.4.4.2.1.2. Biochemical tests
• 1.4.4.2.1.2.1. Why there is no straightforward test for rhizobianess
• 1.4.4.2.1.2.2. Determining rhizobianess by numerical taxonomy
• 1.4.4.2.2. Genetic assays
• 1.4.4.3. Assessing the effectiveness of inoculants
• 1.4.4. Inoculant production
• 1.4.5. Basic research such as genetics and physiology of rhizobia
• 1.4.6. Legume improvement
• 1.5. Aims of this work
• 2. Legume distribution and biomass
• 2.1. Materials and Methods
• 2.1.1. Experimental site
• 2.1.2. Field sampling
• 2.1.3. Biomass and nodule treatments
• 2.1.4. Soil analysis
• 2.1.5. Plant identification
• 2.1.6. Area information
• 2.1.7. Data processing
• 2.2. Results
• 2.2.1. Rapidly available nutrients and grassland productivity
• 2.2.2. Overall legume distribution & nodulation
• 2.2.3. Astragalus distribution & nodulation
• 2.2.4. Oxytropis distribution & nodulation
• 2.2.5. Hedysarum distribution & nodulation
• 2.2.6. Thibetia distribution & nodulation
• 2.2.7. Other legumes
• 2.2.8. Soil nutrients and nodulation
• 2.2.9. Soil pH measurement
• 2.2.10. Sampling methodology
• 2.3. Discussion
• 2.3.1. Statistical relevance
• 2.3.2. Total biomass and legume biomass
• 2.3.3. Diversity and habitat dependence
• 2.3.4. Potential value of Astragaluis sungpanensis for dune revegetation
• 2.3.5. Distribution of potentially poisonous legumes
• 3. Inoculation and fertilization experiment
• 3.1. Materials and Methods
• 3.1.1. Experimental field
• 3.1.2. Experimental design
• 3.1.3. Plot treatment
• 3.1.4. Applying rhizobia
• 3.1.5. Harvest
• 3.1.6. Noting nodule location
• 3.1.7. Soil analysis
• 3.1.8. Mathematical analysis
• 3.2. Results
• 3.2.1. Total productivity
• 3.2.2. Soil aereation
• 3.2.3. Mineral fertilizers
• 3.2.4. Rhizobial inoculation
• 3.2.5. Biomass-nodulation ratio
• 3.3. Discussion
• 3.3.1. Productivity
• 3.3.2. Harmful effects of micronutrients
• 3.3.3. Soil pH and liming
• 3.3.4. Beneficial effects of phosphorus and potassium
• 3.3.5. Ineffectiveness of N fertilization
• 3.3.6. Relation of Nodulation to N and rhizobia availability
• 3.3.7. Nodulation of different legume crops varies markedly
• 4. Determination of wild rhizobia by numerical taxonomy
• 4.1. Materials and methods
• 4.1.1. Isolation and maintenance of bacterial strains
• 4.1.2. Origin of control strains
• 4.1.3. Choice of biological tests
• 4.1.4. C/N utilization and resistance tests
• 4.1.5. Notes on other biochemical tests
• 4.1.6. Blotting colonies onto the agar plates
• 4.1.7. Colony growth scoring
• 4.1.8. Cluster analysis of strains
• 4.2. Results
• 4.2.1. Microbial growth
• 4.2.2. Computation times
• 4.2.3. Using similarity coefficients which do not care for vigor differences
• 4.2.4. Using the Sneath (1968) matching-without-vigor coefficient
• 4.2.5. Using chi-square based coefficients
• 4.2.6. Taxonomy of rhizobia
• 4.2.7. General information yield of different biological tests
• 4.2.8. Taxonomy of biological tests
• 4.2.9. Feasability of the plate design
• 4.3. Discussion
• 4.3.1. General microbiological methods
• 4.3.2. Towards a more robust similarity coefficient
• 4.3.3. Plasticity of the trees generated
• 4.3.4. Putative grassland cross-inoculation groups
• 4.3.5. Biology of rhizobia
• 5. Screening for selective media for Xiaman-huakuii rhizobia
• 5.1. Materials and methods
• 5.1.1. Potential agents for all fast-growing rhizobia
• 5.1.2. Potential agents for individual clusters
• 5.1.3. Repetition of some C-source media
• 5.1.4. Combination of selective agents
• 5.2. Results
• 5.2.1. Selective agents for all rhizobia
• 5.2.2. Selective agents for individual clusters
• 5.2.3. Feasability of C/N source utilization media
• 5.2.4. Results of combined media
• 5.3. Discussion
• 5.3.1. Reproducibility of tests reported in the literature
• 5.3.2. Dye resistance seems promising for Xiaman-huakuii rhizobia
• 5.3.3. Fast verification of Xiaman rhizobia
• 6. Conclusions
• 6.1. Direct results of this work
• 6.2. Some sober thoughts on N cycling in cold environments
• 6.3. Feasible future research
• 6.3.1. N fixation
• 6.3.2. Indigenous legumes
• 6.3.3. Rhizobia
• 6.3.4. Numerical techniques
• 7. Acknowledgments
• 8. Literature
• APPENDIX

DATASET data????
        DATASET.FER vetch fertilization plot dataҰ?㶹ʩ??????
        DATASET.RHI rhizobial strains??????????
        DATASET.SEL published selective media or numerical taxonomiesÇ°?Ë·?????Ñ¡?????????????????Ý·???
        DATASEL.DBF same for DBASE/FOX
        DATASET.TAX strain data for rhizobial taxonomy??????????????????
        DATASET.TRA legume transect sampling data????Ö²???Ö²?????????
        DATATRA.DBF same for DBASE/FOX
        DATASET.TUY soil samples????
        MEDIUM.ALL media used???õ???????

PROG program source code????(Ô­??)
        PROG_LAB.PRG + PROG_LA.PRG using transect data to label herbarium specimen???????????Æ±í±¾????
        PROG_GC.PRG screening for selective mediumɸѡѡ??????????
        PROG_CLU.C cluster analysis????????
        PROG_SLO.C calculating slopes from height lines??ͬ?????????¶?
        FENLEI.F dataset for cluster analysis?????????õ?????
        FCLEAN.C transform DATASET.TAX to FENLEI.F??Ϊ????FENLEI.F
        STA.H + MY.H header files for most of the C programsC??????ͷ?ļ?
        PROG_REF.C English/Chinese reference manager??Ӣ?IJο????׹???
        RR.R + R.R header files for PROG_REF.C?õ?ͷ?ļ?

XIAPLANT botany at XiamanϽ????ֲ??ѧ
        XIAPLANT.ALL list of Xiaman higher plantsϽ???ߵ?ֲ??Ŀ¼
        XIAPLANT.FAB artificial key to Xiaman legumes?ʺϵ??ض???ֲ????????
        XIAPLANT.MY list of species included in the transect data???????ݵ?ֲ????ϸ????
        XIAPLANT.POA artificial key to Xiaman grasses (Chinese only)?ʺϵ??غ̱???ֲ???ļ?????
        XIAPLANT.WEE some data on weeds in vetch experiment?й??㶹????ʵ???Ӳݵ?????

MUMIN ethnobotany of Hongyuan nomads??ԭ????????ֲ??ѧ
        NOMADBOT.CHI report in Chinese???ı???
        NOMADBOT.ENG report in EnglishӢ?ı???
        DATASET.NOM original dataÔ­??????
        OUT.ASC table of answers?Ø´???
        VIEWLEG.PRG generates???? OUT.ASC
        DIAOCHA.JUA original questions??????

From left to right: Dr. Zhou Jiming, Prof. Liu Shigui, Holger Blasum

Tibetan nomad in Xiaman grassland (photo by Andreas Gruneberg)