Root research under natural field conditions is still a step-child of science. The reason for this is primarily methodological. The known methods are tedious, time­ consuming, and the accuracy of their results is often not very great. Many research workers have been discouraged by doing such root studies. The need for more information on the development and distribution of plant roots in different soils under various ecological conditions is, however, obvious in many ecological disciplines. Especially the applied botanical sciences such as agriculture, horticulture, and forestry are interested in obtaining more data on plant roots in the soil. This book will give a survey of existing methods in ecological root research. Primarily field methods are presented; techniques for pot experiments are described only so far as they are important for solving ecological problems. Laboratory methods for studying root physiology are not covered in this book. Scientific publications on roots are scattered in many different journals published all over the world. By working through the international root literature I found that about ten thousand papers on root ecology have been published at the present. This is not very much compared with the immense literature on the aboveground parts of the plants, but is, however, too much to cite in this book.

Inhalt

1. Root Ecology and Root Physiology.- 2. General Survey of Root-Study Methods.- 2.1 Historical Development.- 2.2 Principles of Classification.- 2.3 Selection of the Best Method.- 3. Excavation Methods.- 3.1 Introduction.- 3.2 Outline of the Classical Method.- 3.2.1 Selection of the Plant.- 3.2.2 Digging the Trench.- 3.2.3 Excavating the Root System.- 3.2.4 Drawings and Photographs.- 3.2.5 Preparation and Storage of Excavated Root Systems.- 3.2.6 Review of Applications.- 3.2.7 Advantages and Disadvantages.- 3.3 Modifications of the Classical Method.- 3.3.1 Excavations with Water Pressure.- 3.3.2 Excavations with Air Pressure.- 3.3.3 Excavations in a Horizontal Plane.- 3.3.4 Sector Method.- 4. Monolith Methods.- 4.1 Introduction.- 4.2 Simple Spade Methods.- 4.3 The Common Monolith Method.- 4.3.1 Square Monoliths.- 4.3.2 Round Monoliths.- 4.4 Box Methods.- 4.5 Cage Methods.- 4.6 Needleboard Methods.- 4.6.1 General Survey.- 4.6.2 Construction and Preparation of the Needleboards.- 4.6.3 Excavating the Monoliths.- 4.6.4 Washing Procedure.- 4.6.5 Photographing and Sectioning.- 4.6.6 Special Modifications.- 4.6.7 Evaluation of the Methods.- 5. Auger Methods.- 5.1 Specific Features.- 5.2 Sampling Techniques.- 5.2.1 Techniques with Hand Augers.- 5.2.1.1 Sampling Procedure.- 5.2.1.2 Number or Replications.- 5.2.1.3 Special Technique for Studying Tree Roots.- 5.2.2 Mechanized Techniques.- 5.2.3 Core-Sampling Machines.- 5.3 The Core-Break Method.- 5.4 Advantages and Drawbacks.- 6. Profile Wall Methods.- 6.1 General Survey.- 6.2 The Traditional Trench Profile Method.- 6.2.1 Digging the Trench.- 6.2.2 Preparing the Profile Wall.- 6.2.3 Exposing the Roots.- 6.2.4 Mapping and Counting Procedure.- 6.2.4.1 Determination of Root Number.- 6.2.4.2 Determination of Root Length.- 6.3 The Foil Method.- 6.4 Technique in a Horizontal Plane.- 6.5 Evaluation and Applications.- 7. Glass Wall Methods.- 7.1 Introduction.- 7.2 Glass-Faced Profile Walls.- 7.3 Root Laboratories.- 7.3.1 General Survey.- 7.3.2 Features of Their Design.- 7.3.3 Methods of Recording.- 7.3.4 Light Sensitivity of Roots.- 7.3.5 Recent Research in Root Laboratories.- 7.4 Root Observations with Glass Tubes.- 7.5 Evaluation of the Methods.- 8. Indirect Methods.- 8.1 Introduction.- 8.2 Determination of Soil Water Content.- 8.2.1 Gravimetric Method.- 8.2.2 Neutron Method.- 8.3 Staining Techniques.- 8.4 Uptake of Non-Radioactive Tracers.- 8.5 Radioactive Tracer Methods.- 8.5.1 General Survey.- 8.5.2 Soil Injection Technique.- 8.5.3 Plant Injection Technique.- 8.5.4 Root Studies with 14C.- 8.5.5 Critical Evaluation.- 9. Other Methods.- 9.1 Measuring Root-Pulling Strength.- 9.2 Measuring Root-Clump Weight.- 9.3 Measuring Root Tensile Strength.- 9.4 Root Measurements Using Soil Sections.- 9.5 Root-Detecting Method.- 9.6 Mesh Bag Method.- 9.7 Root Replacement Method.- 9.8 Root Investigations with Paper Chromatography.- 9.9 Electrical Methods.- 9.10 Determination of Growth Rings in Tree Roots.- 9.11 Investigations of Root Hairs.- 9.12 Determination of Root Nodules.- 9.13 Determination of Mycorrhizae.- 10. Container Methods.- 10.1 General Features.- 10.2 Rooting Volume and Container Size.- 10.3 Types of Containers.- 10.3.1 Small Pots.- 10.3.2 Boxes and Tubes.- 10.3.3 Glass-Faced Containers.- 10.3.4 Flexible Tubes.- 10.4 Rooting Media.- 10.5 Filling the Containers.- 10.6 Seed Technique.- 10.7 Irrigation Problems.- 10.8 Special Washing Procedures.- 10.9 Modified Container Methods.- 10.9.1 Cage Method.- 10.9.2 Needleboard Method.- 10.9.3 Root Training by Plastic Tubes.- 10.9.4 Split-Root Technique.- 10.9.5 Undisturbed Soil Monoliths.- 10.10 Root Studies in Nutrient Solutions.- 10.11 Root Studies in Mist Chambers.- 10.12 Comparability of Results from Container Experiments with Field Data.- 11. Techniques of Root Washing.- 11.1 Dry Sieving.- 11.2 Storing Soil-Root Samples Before Washing.- 11.3 Chemicals for Facilitating Root Washing.- 11.4 Washing Roots by Hand.- 11.5 Flotation Method.- 11.6 Root-Washing Machines.- 11.7 Nutrient Losses from Roots During Washing.- 11.8 Cleaning Roots from Debris.- 11.9 Storing Roots After Washing.- 12. Root Parameters and Their Measurement.- 12.1 General Aspects.- 12.2 Root Number.- 12.3 Root Weight.- 12.3.1 Determination of Fresh Weight.- 12.3.2 Determination of Dry Weight.- 12.3.3 Advantages and Critical Objections.- 12.4 Root Surface.- 12.4.1 Calculation from Other Parameters.- 12.4.2 Photoelectric Measurements.- 12.4.3 Adsorption Methods.- 12.5 Root Volume.- 12.5.1 Calculation from Other Parameters.- 12.5.2 Displacement Technique.- 12.6 Root Diameter.- 12.6.1 Measurements.- 12.6.2 Applications in Tree Root Studies.- 12.7 Root Length.- 12.7.1 Direct Measurements.- 12.7.2 Intersection Methods.- 12.7.3 Root-Counting Machines.- 12.7.4 Reasons for Increasing Use of Root Length Measurements.- 12.8 Root Tips.- 12.8.1 Technique of Counting.- 12.8.2 Root Coefficients.- 12.9 Shoot-Root Relations.- 13. Some Future Aspects for the Use of Ecological Root-Study Methods.- References.