The Ecology of Soil Decomposition

Transcription

1 115? The Ecology of Soil Decomposition Sina M. Adi Department of Biology Dalhousie University Halifax, Nova Scotia Canada CABI Publishing

2 Preface Acknowledgements 1 The Saprotrophs 1 Eukaryotic Cells 2 Protists 8 Protozoa 9 Retortomonadea and Trepomonadea (phylum Metamonada) 9 Oxymonadea (phylum Metamonada) 10 Trichomonadea and Hypermastigea (phylum Trichozoa) 11 Percolozoa (phylum Percolozoa) 13 Euglenids (phylum Euglenozoa: Euglenoidea) 14 Bodonids (phylum Euglenozoa: Kinetoplastea) 16 Amoebae (phylum Amoebozoa) 17 Cercozoa and Neomonada 26 Ciliates (phylum Ciliophora) 30 Chromista 32 Bicoecea, Labyrinthulea (phylum Sagenista) 33 Oomycetes and Hyphochytrea (phylum Bigyra: pseudo-fungi) 33 Fungi 34 Chytrids (phylum Archemycota: Chytridiomycetes, Enteromycetes, Allomycetes) 38 Zygomycetes (phylum Archemycota: Zygomycetes and Zoomycetes) 41 Glomales (phylum Archemycota: Glomomycetes and Bolomycetes) 42 Ascomycetes (phylum Ascomycota) 44 Basidiomycetes (phylum Basidiomycota) 44 ix xiii

3 Invertebrates 45 Nematodes (phylum Nemathelminthes: Nematoda) 46 Rotifers (phylum Acanthognatha: Rotifera) 51 Gastrotrichs (phylum Acanthognatha: Monokonta: Gastrotricha) 52 Tardigrades (phylum Lobopoda: Onychophora and Tardigrada) 53 Earthworms (phylum Annelida: Clitellata: Oligochaeta) 56 Microarthropods (phylum Arthropoda: Chelicerata, Myriapoda, Insecta) 60 The Bacteria (Prokaryote: Bacteria and Archea) 66 Roots, Fine Roots and Root Hair Cells 75 Summary 77 Suggested Further Reading 78 2 The Habitat 79 'Through a Ped, Darkly' 79 The soil habitat 81 Soil Mineral Composition 81 Ped structure 84 Soil Air 86 Water Content 87 Natural loss of water 90 Soil temperature 92 Soil Organic Matter 93 Soil horizons 95 Soil nutrient composition 97 Dynamics of Soil Physical Structure 101 Summary 101 Suggested Further Reading Sampling and Enumeration 103 Soil Collection 103 Soil handling 105 Soil storage 106 Site Variation and Statistical Patterns 107 Spatial distribution patterns 108 Pedon sampling and enumeration 109 Experimental design and field sampling 112 Extraction and Enumeration 114 Total potential species diversity 115 Active species at time of sampling 127 Number of Species in Functional Groups 134 Summary 135 Suggested Further Reading 135

4 4 Reconstructing the Soil Food Web 137 Functional Categories 137 Primary Decomposition 139 Plant senescence and necrosis 141 Physical degradation of tissues 142 Macrofauna invertebrates 142 Litter mass loss rates 146 Litter chemistry and decomposition 148 Mesofauna diversity and climate effect on initial litter decomposition 149 Secondary Decomposition 152 Primary Saprotrophs 153 Saprotrophic bacteria 153 Saprotrophic fungi. 158 Osmotrophy 162 Secondary Saprotrophs 164 Bacteriotrophy 165 Cytotrophy 171 Fungivory 175 Detritivory 180 Other Consumers 180 Nematotrophy 181 Predatory microinvertebrates 184 Earthworms 185 Omnivory 187 Symbionts 188 Symbiosis with animals 188 Symbiosis with plant roots 190 Opportunistic Parasites and Parasitism 197 Summary 199 Suggested Further Reading Spatial and Temporal Patterns 201 Regulation of Growth 202 Prokaryotes 202 Protists 206 Invertebrates 209 Periods of Activity 211 Osmoregulation 212 Growth response dynamics 215 Why so many species? 218 Patterns in Time and Space 221 Primary Saprotrophs 223 Spatial organization in bacteria 223 Organization of fungal species 231

5 Secondary Saprotrophs and Other Consumers Patterns in soil protozoa Patterns in nematodes Patterns in the distribution of soil mites Collembola patterns in soil Other insects Earthworm distribution in soil Synthesis and Conclusions Summary Suggested Further Reading 6 Integrating the Food Web Global Impact of Decomposition Carbon Phosphorus ' Nitrogen How to Trace Nutrients Tracer studies Soil Food Web Models Regulation of population growth Regulation of nutrient flux rates Effect of food web structure on decomposition Summary Suggested Further Reading References Index