Soil is one of the most diverse habitats on earth and contains one of the most diverse assemblages of living organisms (Giller et al., 1997). Nowhere, in nature, are species so densely packed as in soil communities (Hågvar, 1998). For example, a single gram of soil may contain millions of individual and several thousand species of bacteria (Torsvik et al., 1994).
The complex physical and chemical nature of the soil, with a porous structure, immense surface area, and extremely variable supply of organic materials, food, water and chemicals mean that various animal, plant and microbial worlds can co-exist simultaneously and find appropriate niches for their development. This provides a range of habitats for a multitude of fauna and flora ranging from macro- to micro- levels depending on climate, vegetation and physical and chemical characteristics of the given soil. The species numbers, composition and diversity of a given soil depend on many factors including aeration, temperature, acidity, moisture, nutrient content and organic substrate.
Soil biota includes bacteria, fungi, protozoa, nematodes, mites (acari), collembolans (springtails), annelids (enchytraeids and earthworms) and macroarthropods (insects, woodlice) (Fig. 1). It also includes plant roots and their exudates attract a variety of organisms which either feed directly on these secretions or graze on the microorganisms concentrated near the roots, giving this busy environment the name of rhizosphere. The soil communities are so diverse in both size and numbers of species, yet they are still extremely poorly understood and in dire need of further assessment. Research has been limited by their immense diversity, their small size and by technical problems.
The complex physical and chemical nature of the soil, with a porous structure, immense surface area, and extremely variable supply of organic materials, food, water and chemicals mean that various animal, plant and microbial worlds can co-exist simultaneously and find appropriate niches for their development. This provides a range of habitats for a multitude of fauna and flora ranging from macro- to micro- levels depending on climate, vegetation and physical and chemical characteristics of the given soil. The species numbers, composition and diversity of a given soil depend on many factors including aeration, temperature, acidity, moisture, nutrient content and organic substrate.
Soil biota includes bacteria, fungi, protozoa, nematodes, mites (acari), collembolans (springtails), annelids (enchytraeids and earthworms) and macroarthropods (insects, woodlice) (Fig. 1). It also includes plant roots and their exudates attract a variety of organisms which either feed directly on these secretions or graze on the microorganisms concentrated near the roots, giving this busy environment the name of rhizosphere. The soil communities are so diverse in both size and numbers of species, yet they are still extremely poorly understood and in dire need of further assessment. Research has been limited by their immense diversity, their small size and by technical problems.
Although some estimates on their density are available for those animal groups which have been more intensively studied, they are still preliminary and very likely to be much lower than the estimated total number of species for any particular group. For example, the described number of soil dwelling fungal species is estimated to be at least 74,000, while the projected number is over 1.5 million (Hawksworth, 2001). Other organisms expected to be much more species-rich are nematodes and mites, with perhaps only 3 and 5%, respectively, of the total species presently described (Walter and Proctor, 1999; Hawksworth and Mound, 1991). The estimates for bacteria and archea species are particularly problematic because of the differences in opinion as to what criteria should be used to define a species, and the present unculturability of many of these organisms (Hawksworth and Kalin-Arroyo, 1995).
Soil biodiversity is often used as a synonym for the number of heterotrophic species below-ground (Hooper et al., 2005) which makes it impracticable in many ecological studies as it contributes little to our understanding of their role in ecosystem function. Another approach to classify soil organisms is using their body size as the main criterion: micro-organisms (e.g. bacteria, fungi), micro-fauna (e.g. protozoa, nematodes), meso-fauna (e.g. acari, springtails, enchytraeids) and macrofauna (e.g. insects, earthworms) (Wallwork, 1970; Swift et al., 1979). Unfortunately, the ranges that determine each group size are not exact for all the members of each group, often leading to considerable confusion as to whether a particular organism should be considered macro or meso, and so on.
Soil biodiversity is often used as a synonym for the number of heterotrophic species below-ground (Hooper et al., 2005) which makes it impracticable in many ecological studies as it contributes little to our understanding of their role in ecosystem function. Another approach to classify soil organisms is using their body size as the main criterion: micro-organisms (e.g. bacteria, fungi), micro-fauna (e.g. protozoa, nematodes), meso-fauna (e.g. acari, springtails, enchytraeids) and macrofauna (e.g. insects, earthworms) (Wallwork, 1970; Swift et al., 1979). Unfortunately, the ranges that determine each group size are not exact for all the members of each group, often leading to considerable confusion as to whether a particular organism should be considered macro or meso, and so on.
Furthermore, this size-based classification does not take into account the functional capabilities of the organisms, i.e. how their activities affect their environment and the potential implications for the soil processes. In both natural and agroecosystems soil biota are responsible for performing vital functions in the soil ecosystem. These functions range from physical effects such as the regulation of soil structure and water regimes, to chemical and biological processes such as degradation of pollutants, decomposition, nutrient cycling, greenhouse gas emission, carbon sequestration, plant protection and growth enhancement or suppression.
When adding these functional aspects to soil biodiversity a ‘functional classification’ is derived and accordingly, a ‘functional group’ can be defined as a group of organisms which affects a process in a similar way (Cummins, 1974). The division of soil biota into roots, ecosystem engineers, litter transformers, phytophages and parasites, micro-predators and microflora proposed by Lavelle (1996) is a good example because it also takes into account the potential top-down regulatory controls of larger organisms (e.g., the ecosystem engineers) over smaller ones. According to this classification “ecosystem engineers” include termites, ants and earthworms, whose bioturbating activities produce structures that can last long periods of time (outlasting the organisms that produced them) and affect soil organic matter dynamics and soil physical processes. “Litter transformers” include many macro- and micro-arthropods, enchytraeid worms and other detritus feeders that stimulate the breakdown and decomposition of surface litter and organic matter, producing small, primarily organic fecal pellets. “Phytophages” and “parasites” include all organisms that feed upon or destroy plant parts, both above and below-ground. The “micropredators” are primarily microfauna such as nematodes and protozoa that do not produce any physical structures and survive by predation on microflora and other organisms, thus stimulating mineralization of organic matter and plant nutrient availability. At the lowest level, the “microflora” act upon organic matter and nutrient cycles, root and rhizosphere processes and plant production (with both positive and negative effects).
Other functional classifications focus on the dietary preferences of certain animals which provide a good indication of their behaviour. An example of this is that produced by Bouché (1971, 1972, 1977) for earthworms, who recognised three ecological groups, epigeics, endogeics and anecics, among European lumbricids. “Epigeic” worms are surface active, pigmented non-burrowing worms with relatively high reproductive rates which consume decaying plant residues on the soil surface; “anecic” worms build vertical burrows in the soil which descend into the mineral horizons but they feed at the surface usually at night; “endogeic” worms inhabit the organo-mineral and deep horizons, constructing branching sub- and horizontal burrows and they feed on more humified organic matter. Similarly, nematodes are classified into primary consumers (plant feeders), secondary consumers (bacterivores and fungivores), and tertiary consumers (predators and omnivores) (Yeates et al., 1993).
These functional classifications could well represent functional adaptations to the soil environment that allow different species to coexist by exploiting different food sources and habitat space (Edwards and Bohlen, 1996) and allow a deeper understanding of how they regulate soil processes rather than a number of species with unknown influences on their environment.
Soil is one of the most diverse habitats on earth and contains one of the most diverse assemblages of living organisms (Giller et al., 1997). Nowhere, in nature, are species so densely packed as in soil communities (Hågvar, 1998). For example, a single gram of soil may contain millions of individual and several thousand species of bacteria (Torsvik et al., 1994).
The complex physical and chemical nature of the soil, with a porous structure, immense surface area, and extremely variable supply of organic materials, food, water and chemicals mean that various animal, plant and microbial worlds can co-exist simultaneously and find appropriate niches for their development. This provides a range of habitats for a multitude of fauna and flora ranging from macro- to micro- levels depending on climate, vegetation and physical and chemical characteristics of the given soil. The species numbers, composition and diversity of a given soil depend on many factors including aeration, temperature, acidity, moisture, nutrient content and organic substrate.
Soil biota includes bacteria, fungi, protozoa, nematodes, mites (acari), collembolans (springtails), annelids (enchytraeids and earthworms) and macroarthropods (insects, woodlice) (Fig. 1). It also includes plant roots and their exudates attract a variety of organisms which either feed directly on these secretions or graze on the microorganisms concentrated near the roots, giving this busy environment the name of rhizosphere. The soil communities are so diverse in both size and numbers of species, yet they are still extremely poorly understood and in dire need of further assessment. Research has been limited by their immense diversity, their small size and by technical problems.
Although some estimates on their density are available for those animal groups which have been more intensively studied, they are still preliminary and very likely to be much lower than the estimated total number of species for any particular group. For example, the described number of soil dwelling fungal species is estimated to be at least 74,000, while the projected number is over 1.5 million (Hawksworth, 2001). Other organisms expected to be much more species-rich are nematodes and mites, with perhaps only 3 and 5%, respectively, of the total species presently described (Walter and Proctor, 1999; Hawksworth and Mound, 1991). The estimates for bacteria and archea species are particularly problematic because of the differences in opinion as to what criteria should be used to define a species, and the present unculturability of many of these organisms (Hawksworth and Kalin-Arroyo, 1995).
Soil biodiversity is often used as a synonym for the number of heterotrophic species below-ground (Hooper et al., 2005) which makes it impracticable in many ecological studies as it contributes little to our understanding of their role in ecosystem function. Another approach to classify soil organisms is using their body size as the main criterion: micro-organisms (e.g. bacteria, fungi), micro-fauna (e.g. protozoa, nematodes), meso-fauna (e.g. acari, springtails, enchytraeids) and macrofauna (e.g. insects, earthworms) (Wallwork, 1970; Swift et al., 1979). Unfortunately, the ranges that determine each group size are not exact for all the members of each group, often leading to considerable confusion as to whether a particular organism should be considered macro or meso, and so on.
Furthermore, this size-based classification does not take into account the functional capabilities of the organisms, i.e. how their activities affect their environment and the potential implications for the soil processes. In both natural and agroecosystems soil biota are responsible for performing vital functions in the soil ecosystem. These functions range from physical effects such as the regulation of soil structure and water regimes, to chemical and biological processes such as degradation of pollutants, decomposition, nutrient cycling, greenhouse gas emission, carbon sequestration, plant protection and growth enhancement or suppression.
When adding these functional aspects to soil biodiversity a ‘functional classification’ is derived and accordingly, a ‘functional group’ can be defined as a group of organisms which affects a process in a similar way (Cummins, 1974). The division of soil biota into roots, ecosystem engineers, litter transformers, phytophages and parasites, micro-predators and microflora proposed by Lavelle (1996) is a good example because it also takes into account the potential top-down regulatory controls of larger organisms (e.g., the ecosystem engineers) over smaller ones. According to this classification “ecosystem engineers” include termites, ants and earthworms, whose bioturbating activities produce structures that can last long periods of time (outlasting the organisms that produced them) and affect soil organic matter dynamics and soil physical processes. “Litter transformers” include many macro- and micro-arthropods, enchytraeid worms and other detritus feeders that stimulate the breakdown and decomposition of surface litter and organic matter, producing small, primarily organic fecal pellets. “Phytophages” and “parasites” include all organisms that feed upon or destroy plant parts, both above and below-ground. The “micropredators” are primarily microfauna such as nematodes and protozoa that do not produce any physical structures and survive by predation on microflora and other organisms, thus stimulating mineralization of organic matter and plant nutrient availability. At the lowest level, the “microflora” act upon organic matter and nutrient cycles, root and rhizosphere processes and plant production (with both positive and negative effects).
Other functional classifications focus on the dietary preferences of certain animals which provide a good indication of their behaviour. An example of this is that produced by Bouché (1971, 1972, 1977) for earthworms, who recognised three ecological groups, epigeics, endogeics and anecics, among European lumbricids. “Epigeic” worms are surface active, pigmented non-burrowing worms with relatively high reproductive rates which consume decaying plant residues on the soil surface; “anecic” worms build vertical burrows in the soil which descend into the mineral horizons but they feed at the surface usually at night; “endogeic” worms inhabit the organo-mineral and deep horizons, constructing branching sub- and horizontal burrows and they feed on more humified organic matter. Similarly, nematodes are classified into primary consumers (plant feeders), secondary consumers (bacterivores and fungivores), and tertiary consumers (predators and omnivores) (Yeates et al., 1993).
These functional classifications could well represent functional adaptations to the soil environment that allow different species to coexist by exploiting different food sources and habitat space (Edwards and Bohlen, 1996) and allow a deeper understanding of how they regulate soil processes rather than a number of species with unknown influences on their environment.
When adding these functional aspects to soil biodiversity a ‘functional classification’ is derived and accordingly, a ‘functional group’ can be defined as a group of organisms which affects a process in a similar way (Cummins, 1974). The division of soil biota into roots, ecosystem engineers, litter transformers, phytophages and parasites, micro-predators and microflora proposed by Lavelle (1996) is a good example because it also takes into account the potential top-down regulatory controls of larger organisms (e.g., the ecosystem engineers) over smaller ones. According to this classification “ecosystem engineers” include termites, ants and earthworms, whose bioturbating activities produce structures that can last long periods of time (outlasting the organisms that produced them) and affect soil organic matter dynamics and soil physical processes. “Litter transformers” include many macro- and micro-arthropods, enchytraeid worms and other detritus feeders that stimulate the breakdown and decomposition of surface litter and organic matter, producing small, primarily organic fecal pellets. “Phytophages” and “parasites” include all organisms that feed upon or destroy plant parts, both above and below-ground. The “micropredators” are primarily microfauna such as nematodes and protozoa that do not produce any physical structures and survive by predation on microflora and other organisms, thus stimulating mineralization of organic matter and plant nutrient availability. At the lowest level, the “microflora” act upon organic matter and nutrient cycles, root and rhizosphere processes and plant production (with both positive and negative effects).
Other functional classifications focus on the dietary preferences of certain animals which provide a good indication of their behaviour. An example of this is that produced by Bouché (1971, 1972, 1977) for earthworms, who recognised three ecological groups, epigeics, endogeics and anecics, among European lumbricids. “Epigeic” worms are surface active, pigmented non-burrowing worms with relatively high reproductive rates which consume decaying plant residues on the soil surface; “anecic” worms build vertical burrows in the soil which descend into the mineral horizons but they feed at the surface usually at night; “endogeic” worms inhabit the organo-mineral and deep horizons, constructing branching sub- and horizontal burrows and they feed on more humified organic matter. Similarly, nematodes are classified into primary consumers (plant feeders), secondary consumers (bacterivores and fungivores), and tertiary consumers (predators and omnivores) (Yeates et al., 1993).
These functional classifications could well represent functional adaptations to the soil environment that allow different species to coexist by exploiting different food sources and habitat space (Edwards and Bohlen, 1996) and allow a deeper understanding of how they regulate soil processes rather than a number of species with unknown influences on their environment.
Soil is one of the most diverse habitats on earth and contains one of the most diverse assemblages of living organisms (Giller et al., 1997). Nowhere, in nature, are species so densely packed as in soil communities (Hågvar, 1998). For example, a single gram of soil may contain millions of individual and several thousand species of bacteria (Torsvik et al., 1994).
The complex physical and chemical nature of the soil, with a porous structure, immense surface area, and extremely variable supply of organic materials, food, water and chemicals mean that various animal, plant and microbial worlds can co-exist simultaneously and find appropriate niches for their development. This provides a range of habitats for a multitude of fauna and flora ranging from macro- to micro- levels depending on climate, vegetation and physical and chemical characteristics of the given soil. The species numbers, composition and diversity of a given soil depend on many factors including aeration, temperature, acidity, moisture, nutrient content and organic substrate.
Soil biota includes bacteria, fungi, protozoa, nematodes, mites (acari), collembolans (springtails), annelids (enchytraeids and earthworms) and macroarthropods (insects, woodlice) (Fig. 1). It also includes plant roots and their exudates attract a variety of organisms which either feed directly on these secretions or graze on the microorganisms concentrated near the roots, giving this busy environment the name of rhizosphere. The soil communities are so diverse in both size and numbers of species, yet they are still extremely poorly understood and in dire need of further assessment. Research has been limited by their immense diversity, their small size and by technical problems.
Although some estimates on their density are available for those animal groups which have been more intensively studied, they are still preliminary and very likely to be much lower than the estimated total number of species for any particular group. For example, the described number of soil dwelling fungal species is estimated to be at least 74,000, while the projected number is over 1.5 million (Hawksworth, 2001). Other organisms expected to be much more species-rich are nematodes and mites, with perhaps only 3 and 5%, respectively, of the total species presently described (Walter and Proctor, 1999; Hawksworth and Mound, 1991). The estimates for bacteria and archea species are particularly problematic because of the differences in opinion as to what criteria should be used to define a species, and the present unculturability of many of these organisms (Hawksworth and Kalin-Arroyo, 1995).
Soil biodiversity is often used as a synonym for the number of heterotrophic species below-ground (Hooper et al., 2005) which makes it impracticable in many ecological studies as it contributes little to our understanding of their role in ecosystem function. Another approach to classify soil organisms is using their body size as the main criterion: micro-organisms (e.g. bacteria, fungi), micro-fauna (e.g. protozoa, nematodes), meso-fauna (e.g. acari, springtails, enchytraeids) and macrofauna (e.g. insects, earthworms) (Wallwork, 1970; Swift et al., 1979). Unfortunately, the ranges that determine each group size are not exact for all the members of each group, often leading to considerable confusion as to whether a particular organism should be considered macro or meso, and so on.
Furthermore, this size-based classification does not take into account the functional capabilities of the organisms, i.e. how their activities affect their environment and the potential implications for the soil processes. In both natural and agroecosystems soil biota are responsible for performing vital functions in the soil ecosystem. These functions range from physical effects such as the regulation of soil structure and water regimes, to chemical and biological processes such as degradation of pollutants, decomposition, nutrient cycling, greenhouse gas emission, carbon sequestration, plant protection and growth enhancement or suppression.
When adding these functional aspects to soil biodiversity a ‘functional classification’ is derived and accordingly, a ‘functional group’ can be defined as a group of organisms which affects a process in a similar way (Cummins, 1974). The division of soil biota into roots, ecosystem engineers, litter transformers, phytophages and parasites, micro-predators and microflora proposed by Lavelle (1996) is a good example because it also takes into account the potential top-down regulatory controls of larger organisms (e.g., the ecosystem engineers) over smaller ones. According to this classification “ecosystem engineers” include termites, ants and earthworms, whose bioturbating activities produce structures that can last long periods of time (outlasting the organisms that produced them) and affect soil organic matter dynamics and soil physical processes. “Litter transformers” include many macro- and micro-arthropods, enchytraeid worms and other detritus feeders that stimulate the breakdown and decomposition of surface litter and organic matter, producing small, primarily organic fecal pellets. “Phytophages” and “parasites” include all organisms that feed upon or destroy plant parts, both above and below-ground. The “micropredators” are primarily microfauna such as nematodes and protozoa that do not produce any physical structures and survive by predation on microflora and other organisms, thus stimulating mineralization of organic matter and plant nutrient availability. At the lowest level, the “microflora” act upon organic matter and nutrient cycles, root and rhizosphere processes and plant production (with both positive and negative effects).
Other functional classifications focus on the dietary preferences of certain animals which provide a good indication of their behaviour. An example of this is that produced by Bouché (1971, 1972, 1977) for earthworms, who recognised three ecological groups, epigeics, endogeics and anecics, among European lumbricids. “Epigeic” worms are surface active, pigmented non-burrowing worms with relatively high reproductive rates which consume decaying plant residues on the soil surface; “anecic” worms build vertical burrows in the soil which descend into the mineral horizons but they feed at the surface usually at night; “endogeic” worms inhabit the organo-mineral and deep horizons, constructing branching sub- and horizontal burrows and they feed on more humified organic matter. Similarly, nematodes are classified into primary consumers (plant feeders), secondary consumers (bacterivores and fungivores), and tertiary consumers (predators and omnivores) (Yeates et al., 1993).
These functional classifications could well represent functional adaptations to the soil environment that allow different species to coexist by exploiting different food sources and habitat space (Edwards and Bohlen, 1996) and allow a deeper understanding of how they regulate soil processes rather than a number of species with unknown influences on their environment.
REFERENCES
Bouché, M.B., 1971. Relations entre les structures spatiales et fonctionelles des ecosystems, illustrées par le role pédobiologique des vers de terre. In: La Vie dans les Sols, Aspects Nouveaux, Études Experimentales (Ed. P. Pesson), pp. 187- 209. Gauthier-Villars, Paris.
Bouché, M.B., 1972. Lombriciens de France. Ecologie et Systématique, Institut National de la Recherche Agronomique, Paris.
Bouché, M.B., 1977. Stratégies lombriciennes. In: Soil Organisms as Components of Ecosystems ( Eds. U. Lohm and T. Persson), pp. 122-132. Ecological Bulletins 25, Stockholm, Sweden.
Cummins, K.W., 1974. Structure and function of stream ecosystems. Bioscience 24, 631-641.
Edwards, C. A. and Bohlen, P. J., 1996. Biology and Ecology of Earthworms. Chapman and Hall, London.
Giller, K.E., Beare, M.H., Lavelle, P., Izac A.M.N and Swift, M.J. , 1997. gricultural intensification, soil biodiversity and agroecosystem function Applied Soil Ecology 6, 3-16.
Hågvar, S., 1998. The relevance of the Rio-Convention on biodiversity to conserving the biodiversity of soils. Applied Soil Ecology 9, 1-7.
Hawksworth, D.L. & Mound, L.A., 1991. Biodiversity Databases: The Crucial Significance of Collections. In: D.L. Hawksworth (Ed), The Biodiversity of Microorganisms and Invertebrates: Its Role in Sustainable Agriculture, pp. 17-31. CAB Intemational, Wallingford.
Hawksworth, D.L. and Kalin-Arroyo, M.T., 1995. Magnitude and distribution of biodiversity. In: V.H. Heywood and R.T. Watson (Eds) Global biodiversity assessment, pp. 107-191. United Nations Environment Programme & Cambridge University Press, Cambridge, UK.
Hawksworth, D.L., 2001. The magnitude of fungal diversity: the 1•5 million species estimate revisited Mycological Research 105, 1422-1432.
Hooper, D.U., Chapin III, F.S., Ewel, J.J., Hector, A., Inchausti, P., Lavorel, S., Lawton, J.H., Lodge, D.M., Loreau, M., Naeem, S. , Schmid, B., Setälä, H., Symstad, A.J., Vandermeer, J., Wardle, D. A., 2005. Effects of biodiversity on ecosystem functioning: a consensus of current knowledge. Ecological Monographs 75, 3–35.
Lavelle, P., 1996. Diversity of soil fauna and ecosystem function. Biology International 33, 3-16.
Swift, M.J., Heal, O.W. and Anderson, J.M., 1979. Decomposition in terrestrial ecosystems, Blackwell, London.
Torsvik, V., Goksoyr, J., Daae, F.L., Sorheim, R., Michalsen, J. and Salte, K., 1994. Use of DNA analysis to determine the diversity of microbial communities. In: Ritz, K., Dighton, J. and Giller, K.E., Editors, 1994. Beyond the Biomass, Wiley, Chichester, pp. 39–48.
Wallwork, J.A., 1970. Ecology of Soil Animals. McGraw-Hill. New York.
Walter, D.E. and Proctor, H.C., 1999. Mites: Ecology, Evolution and Behaviour. University of New South Wales Press and CAB International.
Yeates, G.W., Bongers, T., de Goede, R.G.M., Freckman, D.W., Georgieva, S.S., 1993. Feeding habits in soil nematode families and genera – an outline for soil ecologists. Journal of Nematology 25, 315-331.
Bouché, M.B., 1972. Lombriciens de France. Ecologie et Systématique, Institut National de la Recherche Agronomique, Paris.
Bouché, M.B., 1977. Stratégies lombriciennes. In: Soil Organisms as Components of Ecosystems ( Eds. U. Lohm and T. Persson), pp. 122-132. Ecological Bulletins 25, Stockholm, Sweden.
Cummins, K.W., 1974. Structure and function of stream ecosystems. Bioscience 24, 631-641.
Edwards, C. A. and Bohlen, P. J., 1996. Biology and Ecology of Earthworms. Chapman and Hall, London.
Giller, K.E., Beare, M.H., Lavelle, P., Izac A.M.N and Swift, M.J. , 1997. gricultural intensification, soil biodiversity and agroecosystem function Applied Soil Ecology 6, 3-16.
Hågvar, S., 1998. The relevance of the Rio-Convention on biodiversity to conserving the biodiversity of soils. Applied Soil Ecology 9, 1-7.
Hawksworth, D.L. & Mound, L.A., 1991. Biodiversity Databases: The Crucial Significance of Collections. In: D.L. Hawksworth (Ed), The Biodiversity of Microorganisms and Invertebrates: Its Role in Sustainable Agriculture, pp. 17-31. CAB Intemational, Wallingford.
Hawksworth, D.L. and Kalin-Arroyo, M.T., 1995. Magnitude and distribution of biodiversity. In: V.H. Heywood and R.T. Watson (Eds) Global biodiversity assessment, pp. 107-191. United Nations Environment Programme & Cambridge University Press, Cambridge, UK.
Hawksworth, D.L., 2001. The magnitude of fungal diversity: the 1•5 million species estimate revisited Mycological Research 105, 1422-1432.
Hooper, D.U., Chapin III, F.S., Ewel, J.J., Hector, A., Inchausti, P., Lavorel, S., Lawton, J.H., Lodge, D.M., Loreau, M., Naeem, S. , Schmid, B., Setälä, H., Symstad, A.J., Vandermeer, J., Wardle, D. A., 2005. Effects of biodiversity on ecosystem functioning: a consensus of current knowledge. Ecological Monographs 75, 3–35.
Lavelle, P., 1996. Diversity of soil fauna and ecosystem function. Biology International 33, 3-16.
Swift, M.J., Heal, O.W. and Anderson, J.M., 1979. Decomposition in terrestrial ecosystems, Blackwell, London.
Torsvik, V., Goksoyr, J., Daae, F.L., Sorheim, R., Michalsen, J. and Salte, K., 1994. Use of DNA analysis to determine the diversity of microbial communities. In: Ritz, K., Dighton, J. and Giller, K.E., Editors, 1994. Beyond the Biomass, Wiley, Chichester, pp. 39–48.
Wallwork, J.A., 1970. Ecology of Soil Animals. McGraw-Hill. New York.
Walter, D.E. and Proctor, H.C., 1999. Mites: Ecology, Evolution and Behaviour. University of New South Wales Press and CAB International.
Yeates, G.W., Bongers, T., de Goede, R.G.M., Freckman, D.W., Georgieva, S.S., 1993. Feeding habits in soil nematode families and genera – an outline for soil ecologists. Journal of Nematology 25, 315-331.
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