Contents

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v

Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii

Introduction

I. General Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

A. Decomposition, Nutrient Turnover, and Global

Climate Change . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

B. Biomass Distribution between Soil and Above-Ground

Ecosystem Compartments . . . . . . . . . . . . . . . . . . . . . . . 9

C. The Importance of Balance . . . . . . . . . . . . . . . . . . . . . . 12

Litter Fall

I. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

II. Litter Fall Amounts—Main Patterns and Regulating Factors . 21

A. Patterns on the Forest Stand Level . . . . . . . . . . . . . . . . 21

B. Litter Fall Patterns in Scots Pine—A Case Study . . . . . . 23

III. A Model for Accumulated Litter Fall, Stand Level . . . . . . . . 26

A. General Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

B. A Case Study for a Scots Pine Stand . . . . . . . . . . . . . . . 26

IV. Main Litter-Fall Patterns on a Regional Level: Scots Pine and

Norway Spruce . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

A. Distribution of Species . . . . . . . . . . . . . . . . . . . . . . . . . 28

B. Factors Influencing Amounts of Litter Fall. . . . . . . . . . . 28

C. Needle Litter Fall—Pattern and Quantities: Scots Pine

and Other Pine Species . . . . . . . . . . . . . . . . . . . . . . . . . 29

D. Basal Area and Canopy Cover. . . . . . . . . . . . . . . . . . . . 35

E. Needle Litter Quantities: Norway Spruce . . . . . . . . . . . . 36

F. Comparison of and Combination of Species . . . . . . . . . . 36

G. Litter Fall on a Continental to Semiglobal Scale . . . . . . . 37

V. The Fiber Structure and Organic–Chemical Components of

Plant Litter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

A. The Fiber. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

B. The Organic–Chemical Components. . . . . . . . . . . . . . . . 43

x CONTENTS

VI. Nutrients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

A. General Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

B. The Trees Withdraw Nutrients before Shedding their

Foliar Litter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

C. Scots Pine—A Case Study. . . . . . . . . . . . . . . . . . . . . . . 53

D. Foliar Litter N Concentration in a Trans-European

Transect, Several Species. . . . . . . . . . . . . . . . . . . . . . . . 58

E. Several Deciduous and Coniferous Leaf Litters. . . . . . . . 58

VII. Anthropogenic Influences . . . . . . . . . . . . . . . . . . . . . . . . . . 62

A. Nitrogen-Fertilized Scots Pine and Norway

Spruce Monocultures . . . . . . . . . . . . . . . . . . . . . . . . . . 62

B. The EVect of Heavy Metal Pollution . . . . . . . . . . . . . . . 67

VIII. Methods for Litter Collection . . . . . . . . . . . . . . . . . . . . . . . 69

A. Quantities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

B. Qualitative Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . 71

Decomposers: Soil Microorganisms and Animals

I. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

II. Communities of Soil Microorganisms and Animals . . . . . . . . 75

A. Soil Microorganisms. . . . . . . . . . . . . . . . . . . . . . . . . . . 75

B. Soil Animals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

III. The Degradation of the Main Polymers in Plant Fibers . . . . . 79

A. Degradation of Cellulose . . . . . . . . . . . . . . . . . . . . . . . 79

B. Degradation of Hemicelluloses . . . . . . . . . . . . . . . . . . . 82

C. EVects of N, Mn, and C Sources on the Degradation

of Lignin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

D. Degradation of Lignin . . . . . . . . . . . . . . . . . . . . . . . . . 87

IV. Degradation of Fibers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

A. Fungi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

B. Bacteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

V. Microbial Communities and the Influence of Soil Animals. . . 94

A. Microbial Succession and Competition. . . . . . . . . . . . . . 94

B. EVects of Soil Animals on the Decomposition Process . . 96

Changes in Substrate Composition and Rate-Regulating

Factors during Decomposition

I. Introductory Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

II. Organic–Chemical Changes During Litter Decomposition . . . 104

A. Decomposition of Single Chemical Components and

Groups of Compounds . . . . . . . . . . . . . . . . . . . . . . . . . 104

B. Relationships between Holocellulose and Lignin

during Decomposition . . . . . . . . . . . . . . . . . . . . . . . . . 114

CONTENTS xi

III. Concentrations of Nutrients and Heavy Metals During

Litter Decay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

A. Nitrogen (N) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

B. Phosphorus (P) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

C. Sulphur (S). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

D. Potassium (K) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

E. Calcium (Ca) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

F. Magnesium (Mg) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

G. Other Metals and Heavy Metals in

Natural Concentrations . . . . . . . . . . . . . . . . . . . . . . . . . 118

IV. A Three-Phase Model Applied to Litter of DiVerent InitialChemical Composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

A. Overview of the Model . . . . . . . . . . . . . . . . . . . . . . . . . 119

B. Initial Decomposition Rates for Newly Shed Litter—The

Early Decomposition Stage . . . . . . . . . . . . . . . . . . . . . . 119

C. Decomposition in the Late Stage—A Phase Regulated

by Lignin Decomposition . . . . . . . . . . . . . . . . . . . . . . . 129

D. Link between the Retardation of Litter Decomposition,

Lignin Degradation Rate and N Concentration. . . . . . . . 137

E. Comments on Spruce Needle Litter Decomposition

versus the Three-Phase Model . . . . . . . . . . . . . . . . . . . . 139

F. The Litter Close to the Limit Value and at a

Humus-Near Stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142

G. Do Limit Values Indicate a Stop in the Litter

Decomposition Process? . . . . . . . . . . . . . . . . . . . . . . . . 150

V. Lignin Dynamics in Decomposing Litter. . . . . . . . . . . . . . . . 150

A. Repeatability of Patterns in Lignin

Concentration Changes . . . . . . . . . . . . . . . . . . . . . . . . . 150

B. Variation in the Increase in Lignin Concentration

Relative to DiVerent Initial Lignin Concentrations in

the Litter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153

C. Variation in Lignin Concentration Increase Rate

as Compared to DiVerent Concentrationsof N in Litter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153

VI. Does the Litter Chemical Composition Influence Leaching

of Compounds from Decomposing Litter?. . . . . . . . . . . . . . . 154

xii CONTENTS

Nitrogen Dynamics in Decomposing Litter

I. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157

II. The Dynamics of Nitrogen—Three Phases in

Decomposing Litter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159

A. General Comments. . . . . . . . . . . . . . . . . . . . . . . . . . . . 159

B. The Leaching Phase . . . . . . . . . . . . . . . . . . . . . . . . . . . 161

C. Nitrogen Accumulation Phase—A Phase with a Net

Uptake and a Retention of N . . . . . . . . . . . . . . . . . . . . 164

D. A Release Mechanism. . . . . . . . . . . . . . . . . . . . . . . . . . 170

E. The Final Release Phase . . . . . . . . . . . . . . . . . . . . . . . . 176

III. Nitrogen Concentration Versus Accumulated

Litter Mass Loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177

IV. Nitrogen Concentration in Litter Decomposing to the

Limit Value and in Humus . . . . . . . . . . . . . . . . . . . . . . . . . 181

A. Background and Some Relationships . . . . . . . . . . . . . . . 181

B. A Model and a Case Study for Calculating N

Concentrations in Humus . . . . . . . . . . . . . . . . . . . . . . . 182

Origin and Structure of Secondary Organic Matter and

Sequestration of C and N

I. Introductory Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . 185

II. Terminology According to Traditional Humus Classification

and Chemical Composition of Secondary Organic Matter . . . 189

III. Origin of Secondary Organic Matter—Some

Primary Scenarios. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194

A. Introductory Comments . . . . . . . . . . . . . . . . . . . . . . . . 194

B. Two Traditional Scenarios . . . . . . . . . . . . . . . . . . . . . . 195

C. Some More Recent Approaches to Humic Substances . . . 196

IV. The Role of SOM in Soil . . . . . . . . . . . . . . . . . . . . . . . . . . 198

V. What Litter Components May Be of Importance for the

Formation of Humus?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200

VI. The Accumulation Rate of Humus. . . . . . . . . . . . . . . . . . . . 203

A. Direct Measurements of Humus Accumulation. . . . . . . . 203

B. Accumulation of Humus—Estimates . . . . . . . . . . . . . . . 204

C. How Reliable are Quantitative Estimates of

Humus Accumulation? . . . . . . . . . . . . . . . . . . . . . . . . . 210

VII. May All Humus be Decomposed or Just a Fraction?. . . . . . . 210

A. DiVerent Fractions—General Comments . . . . . . . . . . . . 210

B. Four Cases of Turnover of Humus Layers . . . . . . . . . . . 211

CONTENTS xiii

VIII. Humus Accumulation and Decomposition Versus The

Concept ‘‘Steady State’’ . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215

A. Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215

B. Why Is It an Error to Use the Concept ‘‘Steady State’’? . 216

IX. Nitrogen Sequestration to SOM . . . . . . . . . . . . . . . . . . . . . . 217

A. We Can Estimate the Sequestration Rate of N in

Stable Organic Matter. . . . . . . . . . . . . . . . . . . . . . . . . . 217

B. We Can Validate the Long-Term Accumulation of

Stable Nitrogen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218

X. The Capacity of SOM to Store N. . . . . . . . . . . . . . . . . . . . . 221

XI. Can DiVerent Capacities to Sequester N Be Related to

Species or to The Initial Litter N Concentration? . . . . . . . . . 222

XII. How Stable Is the Long-term N Stored in Humus? . . . . . . . . 225

Climatic and Geographic Patterns in Decomposition

I. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227

II. The Microbial Response to Temperature and Moisture . . . . . 228

III. The Influence of Climate on Early-Stage Decomposition

of Scots Pine Needle Litter . . . . . . . . . . . . . . . . . . . . . . . . . 229

A. Early-Stage Decomposition at One Forest

Stand over Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229

B. Decomposition Studies in Transects with Scots

Pine and Norway Spruce . . . . . . . . . . . . . . . . . . . . . . . . 231

IV. The EVect of Substrate Quality on Mass-Loss Rates

in Scots Pine Transects . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240

A. Early Stages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240

B. Decomposition over a Transect with Scots Pine

Monocultures—The Late Stage . . . . . . . . . . . . . . . . . . . 242

C. Respiration from Humus from Scots Pine

Stands in a Pan-European Transect . . . . . . . . . . . . . . . . 245

V. The Influence of Climate on Decomposition of Norway

Spruce Litter in a Transect . . . . . . . . . . . . . . . . . . . . . . . . . 250

A. General Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250

B. Climate Versus First-Year Mass Loss . . . . . . . . . . . . . . . 251

C. Lignin-Mediated EVects on Litter Decomposition

Rates during Late Stages of Decomposition . . . . . . . . . . 252

VI. A Series of Limiting Factors for Decomposing Litter. . . . . . . 255

A. Factors Influencing Lignin Degradation Rates . . . . . . . . 255

VII. The Influence of Climate on Decomposition of Root Litter . . 257

xiv CONTENTS

VIII. Litter Chemical Changes as Related to Climate. . . . . . . . . . . 259

A. Development of Litter N Concentration with

Climate in Decomposing Scots Pine Needle

Litter (Transects I and II) . . . . . . . . . . . . . . . . . . . . . . . 259

B. Development of Litter ‘‘Lignin’’ Concentration with

Climate in Decomposing Needle Litter. . . . . . . . . . . . . . 260

Anthropogenic Impacts on Litter Decomposition and Soil

Organic Matter

I. Introductory Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . 263

II. Fate of Pollutants in Litter and Soil. . . . . . . . . . . . . . . . . . . 264

A. General Background. . . . . . . . . . . . . . . . . . . . . . . . . . . 264

B. Acidic Precipitation . . . . . . . . . . . . . . . . . . . . . . . . . . . 265

C. Heavy Metals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266

D. Accumulation of Heavy Metals in Decomposing

Litter—A Case Study . . . . . . . . . . . . . . . . . . . . . . . . . . 268

E. Sources of Heavy Metals in Litter . . . . . . . . . . . . . . . . . 271

F. Organic Pollutants . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275

III. EVects of Pollutants on Decomposition . . . . . . . . . . . . . . . . 277

A. Heavy Metals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277

B. Acidic Precipitation . . . . . . . . . . . . . . . . . . . . . . . . . . . 280

C. Organic Pollutants . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281

D. EVects of Climate Change. . . . . . . . . . . . . . . . . . . . . . . 283

E. Changes in Water Regimen . . . . . . . . . . . . . . . . . . . . . . 289

Methods in Studies of Organic Matter Decay

I. Introductory Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . 291

II. Incubation Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292

A. In Situ (Field) Methods . . . . . . . . . . . . . . . . . . . . . . . . 292

B. Decomposition Rate—Laboratory Methods . . . . . . . . . . 309

III. Studying Chemical Changes During Decomposition . . . . . . . 314

A. Introductory Comments . . . . . . . . . . . . . . . . . . . . . . . . 314

B. Preparation of Samples for Chemical Analysis

and Some Analytical Techniques . . . . . . . . . . . . . . . . . . 315

IV. Data Analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320

A. Regression Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . 320

B. Analysis of Variance (ANOVA) . . . . . . . . . . . . . . . . . . 324

C. Multivariate Methods . . . . . . . . . . . . . . . . . . . . . . . . . . 326

V. Presentation of the Results . . . . . . . . . . . . . . . . . . . . . . . . . 328

CONTENTS xv

Appendix I. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333

Appendix II . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377

Index. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 407

Cumulative List of Titles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 423