Factors Affecting the Abundance of Earthworms in Soils - Earthworm Ecology - page 86

6

Factors Affecting the
Abundance of Earthworms in
Soils

James P. Curry

Department of Environmental Resource Management, University College,
Belfield, Dublin, Ireland

CONTENTS

Introduction ......................................................................................................................................91
Climate .............................................................................................................................................92
Soil Properties ..................................................................................................................................93
Food..................................................................................................................................................94
Competition ......................................................................................................................................98
Predation...........................................................................................................................................99
Parasitism and Disease...................................................................................................................100
Land Management..........................................................................................................................100
Mining and Industrial Wastes .................................................................................................101
Deforestation ...........................................................................................................................102
Afforestation ...........................................................................................................................102
Grassland Management...........................................................................................................103
Arable Cropping .....................................................................................................................103
Manures and Fertilizers ..........................................................................................................105
Pesticides and Pollutants ........................................................................................................106
Soil Water Management..........................................................................................................106
Conclusions ....................................................................................................................................107
References ......................................................................................................................................108

INTRODUCTION

Earthworm populations show a considerable amount of variability in time and space, with mean
population densities and biomass ranging from fewer than 10 individuals and 1 g m

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, respectively,

to more than 1000 individuals and 200 g m , respectively, under favorable conditions. However,

within particular climatic zones, earthworm assemblages, with fairly characteristic species richness,
composition, abundance, and biomass, can often be recognized in broadly different habitat types,
such as coniferous forests, deciduous woodland, grassland, and arable land. There is a considerable
volume of literature describing the earthworm communities of such habitats, and much of this was
summarized by Lee (1985) and updated by Edwards and Bohlen (1996). There is also a considerable
amount of information describing the influence of various environmental and management factors
on earthworm populations, but in comparison with insects, for which the population ecology of

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91