Advances in agronomy. V.96 /

Front Cover 1
Advances in Agronomy 4
Copyright Page 5
Contents 6
Contributors 10
Preface 14
Chapter 1: Microbial Ecology of Methanogens and Methanotrophs 15
1. Introduction 16
1.1. Global methane budget and processes controlling methane emission from rice fields 16
1.2. Role of methanogens and methanotrophs in carbon cycling and methane emission 17
2. Microbial Ecology of Methanogens 22
2.1. Physiology and phylogeny of methanogens 22
2.2. Diversity, habitats, and ecological niches 24
2.3. Microbiological explanations for macroscopic processes, that is production and emission of methane 30
3. Microbial Ecology of Methanotrophs 45
3.1. Physiology and phylogeny of methanotrophs 45
3.2. Diversity, habitats, and ecological niches of aerobic methanotrophs 48
4. Mitigation of Methane Emission from Rice Fields 56
5. Conclusions and Outlook 57
References 59
Chapter 2: Strategies of Plants to Adapt to Mineral Stresses in Problem Soils 79
1. Introduction 80
2. Fe-Deficiency Stress 83
2.1. Chemistry of Fe in soils 84
2.2. Mechanism of Fe acquisition in plants 87
2.3. Genetic improvement of Fe-acquisition ability in plants 99
3. Al-Toxicity Stress 100
3.1. Chemistry of Al and plant-originated Al-detoxifying agents in soils 101
3.2. Mechanism of Al toxicity 109
3.3. Mechanism of Al-toxicity tolerance 113
4. P-Deficiency Stress 118
4.1. Chemistry of P and plant-originated P-dissolving agents in soils 119
4.2. Mechanism of P acquisition in plants 121
4.3. Genetic improvement in plants to tolerate P deficiency 125
5. Future Prospects 126
References 126
Chapter 3: Water Flow in the Roots of Crop Species: The Influence of Root Structure, Aquaporin Activity, and Waterlogging 147
1. Introduction 148
2. Water Movement Through the Plant 149
2.1. Driving forces 149
2.2. Hydraulic conductance 151
2.3. Hydraulic conductivity of roots (Lpr) 152
3. Root Characteristics and Water Flow 154
3.1. Factors that influence root growth and water uptake 154
3.2. Root anatomy 155
4. Changes in Lpr 160
5. Plant Aquaporins (aqps) 161
5.1. AQP structure 162
5.2. AQP selectivity 164
5.3. Control of water permeability 166
6. The Role of AQPs in Root Water Transport 181
6.1. Inhibition studies 181
6.2. Expression and transformation studies 183
6.3. The contribution of AQPs to radial water flow 184
7. Waterlogging 185
7.1. Effect on O2 in the rhizosphere 185
7.2. Effect on root growth 186
7.3. Effect on water use 188
7.4. Anoxia and AQP activity 189
8. Conclusion 194
Acknowledgments 195
References 196
Chapter 4: Phytoremediation of Sodic and Saline-Sodic Soils 211
1. Introduction 213
2. Description of Sodic and Saline-Sodic Soils 215
3. Degradation Processes in Sodic and Saline-Sodic Soils 217
4. Phytoremediation of Sodic and Saline-Sodic Soils 220
4.1. Historical perspective 222
4.2. Mechanisms and processes driving phytoremediation 226
4.3. Comparative efficiency of phytoremediation 237
4.4. Plant species for phytoremediation 247
5. Perspectives 250
Acknowledgments 253
References 253
Chapter 5: Ecology of Denitrifying Prokaryotes in Agricultural Soil 263
1. Introduction 264
2. Agronomical and Environmental Importance of Denitrification 267
2.1. Consequences of denitrification for agriculture 267
2.2. Impact of denitrification on the environment and human health 268
3. Who are the Denitrifiers? 269
3.1. Denitrifiers and nitrate reducers 269
3.2. Denitrifying populations 269
4. Assessing Denitrifiers Density, Diversity, and Activity 272
4.1. Measuring denitrification and N2O emissions 272
4.2. Resolving diversity of denitrifiers 273
4.3. Quantification of denitrifiers 274
5. Natural Factors Causing Variations in Denitrification 276
5.1. Temperature and water 276
5.2. Freeze-thaw cycles 277
5.3. Dry-wet cycles 279
6. Denitrification in the Rhizosphere of Crops 280
6.1. Crops as a factor influencing denitrifiers 280
6.2. Impact of crop species, crop cultivars, and transgenic plants 284
7. Impact of Fertilization on Denitrification 287
7.1. Fertilization affects denitrification 287
8. Effect of Environmental Pollution on Denitrifiers 293
8.1. Pollution affects denitrification 293
8.2. Pesticides 294
8.3. Heavy metals 297
9. Conclusions and Outlook 299
References 301
Chapter 6: Linking Soil Organisms Within Food Webs to Ecosystem Functioning and Environmental Change 321
1. Introduction 322
2. Overview of the Soil Food Web 323
3. Impacts on Soil Food Web Dynamics Associated with Human Activities 327
3.1. Biodiversity loss 327
3.2. Invasive species 329
3.3. Climate change 331
3.4. GM crops 334
4. Alternative Approaches: Seeing the Forest for the Trees 336
4.1. Nematode faunal analysis 337
4.2. Modeling food web dynamics 342
5. Missing and Ambiguous Components of Current Soil Food Web Knowledge 349
5.1. Resolution 349
5.2. Integration of the detritivore and herbivore food webs 350
5.3. Role of technology in resolving soil food webs 352
6. Summary and Conclusions 354
Acknowledgments 355
References 355
Chapter 7: Comparative Typology in Six European Low-Intensity Systems of Grassland Management 365
1. Introduction 367
2. Presentation of Study Areas 369
2.1. Northern Sapmi, Fennoscandia 369
2.2. Tatra mountains, Poland 372
2.3. UNESCO Biosphere Entlebuch, Switzerland 373
2.4. Bavaria, Germany 373
2.5. Baixo Alentejo, Portugal 374
2.6. Castile-La Mancha, Spain 375
3. Material and Methods 375
3.1. Main criteria and indicators 376
3.2. Management units 381
3.3. Sampling process 382
4. Results 384
4.1. Land uses 384
4.2. Size of farm-holding, land prices, and grazing fees 386
4.3. Institutional economics 389
4.4. Institutional and legal frameworks 393
4.5. Forage deficit 395
4.6. Grazing infrastructure 399
4.7. Labor 402
4.8. Productivity estimates 404
4.9. Economic performance 409
4.10. Grazing management and trends 415
4.11. Main limiting factors 418
4.12. Interface to biodiversity 420
5. Discussion 422
References 428
Index 435