Directory UMM :Data Elmu:jurnal:A:Applied Soil Ecology:Vol13.Issue2.Oct1999:
Applied Soil Ecology 13 (1999) 151±158
Does soil biodiversity depend upon metabiotic activity and in¯uences?
John Saville Waid1,*
School of Microbiology, La Trobe University, Bundoora, Victoria 3083, Australia
Received 1 May 1998; received in revised form 1 October 1998; accepted 25 February 1999
Abstract
A central tenet of biological science is that living organisms modify their environments. Metabiosis is a form of ecological
dependence in which one organism or a functional group of organisms must modify the environment before another organism
or functional group of organisms can live or thrive in it. Soil ecosystems are modi®ed by metabionts to create habitats or
supply resources for which dependent organisms may adapt, evolve and hence diversify. Thus, the diversity of the soil biota
and its functional capabilities may to a large extent be the result of and dependent upon metabiotic activity and in¯uences.
Examples of metabiotic activity in soil ecosystems are: plants are the main source of O2 for the soil biota; decomposers
deplete soil O2 thus enabling the growth of microaerophiles or anaerobes; ammonium released by bacterial deamination
supports the growth of autotrophic ammonium-oxidisers; burrowing earthworms improve soil drainage and create aeration
channels for aerobic biota; detoxi®cation of plant residues by biodegraders permits proliferation of toxin-sensitive organisms;
wood decay by microbes creates habitats for arthropods associated with rotting wood; arthropod comminution of litter
liberates nutrients that facilitate microbial activity. Some metabionts, the panmetabionts, had a global in¯uence by modifying
the biosphere, its evolving biota and by maintaining its biogeochemistry. For example, during the development of the
biosphere the cyanobacteria began the transformation of the atmosphere through the production of O2. The accumulation of
atmospheric O2 had an overwhelming in¯uence on the formation of soils, their physico-chemistry and biology, in particular
the evolution of diverse major groups of aerobic terrestrial organisms (plants, fungi and animals). Many practices to improve
soil fertility, e.g. agro-forestry, mulching, legume inoculation, minimum tillage are applications of metabiotic techniques,
which maintain or improve soil biodiversity and its functional potentiality. Conversely, where ecosystems are degraded
through human activity, e.g. forest destruction, irrigation with saline water, strip-mining, deep tillage, there is an inevitable
reduction of species of animals and plants. It can also result in the loss of some components of the soil community, e.g.
mycorrhizal fungi, macrobiota such as invertebrates, with a consequent reduction in or a loss of the metabiotic activities of
functional groups of the soil biota. Types of metabiotic action include facilitation, ecological engineering, commensalism and
keystone predation. Metabiosis must rank with biotic interrelationships and interactions, such as competition, predation or
mutualism, in its effects upon soil communities and ecosystems. # 1999 Elsevier Science B.V. All rights reserved.
Keywords: Metabiosis; Panmetabiosis; Biotic interactions; Biodiversity; Soil ecosystems; Ecological engineers
*Corresponding author. Tel.: +61-754-458-896; fax: +61-754769-183
E-mail address: jswsbbbud@peg.apc.org (J.S. Waid)
1
Present address: PO Box 760, Buderim, Queensland 4556,
Australia.
1. Introduction
Soil is an outstanding example of a natural system
where living organisms have and still play a major role
in the development of its physico-chemical features.
0929-1393/99/$ ± see front matter # 1999 Elsevier Science B.V. All rights reserved.
PII: S 0 9 2 9 - 1 3 9 3 ( 9 9 ) 0 0 0 3 0 - X
152
J.S. Waid / Applied Soil Ecology 13 (1999) 151±158
Soils contain a motley medley of habitats occupied by
a great diversity of organisms performing an overwhelming variety of functions. Our knowledge of the
abundance and functioning of the various components
of the soil community and of the range of mechanisms
whereby the different soil inhabitants interact with one
another is far from complete. Those interrelationships
where the effects are direct, such as the trophic
mutualistic, parasitic, predatory types of interactions
and competition for resources, have been reasonably
well investigated (Jones et al., 1994). However, there
are a number of indirect types of interrelationships and
interactions that have mechanisms and ecosystem
functions which also need to be fully elucidated.
We need to answer the following questions: Do
indirect types of interactions affect biological and
functional diversity? If so how? Can the effects of
indirect interactions upon biological and functional
diversity be measured? Do indirect interactions confer
resilience on ecosystem functioning by maintaining
the survival of biological diversity and the sustainability of an ecosystem when the environment
changes?
Characteristically organisms bring about physical
and chemical changes to their habitats. These modi®cations, whether ephemeral of enduring, alter the
environment so that some species are enabled to live
and ¯ourish, and others may adapt and evolve to
occupy the novel habitats, while others are decimated
or fail to grow. Metabiosis is a type of biological
action whereby single species or functional groups of
organisms create, maintain or modify environments
and habitats enabling other species to grow, survive
and perhaps evolve. My purpose is to speculate on the
possible involvement of metabiosis by modifying or
creating habitats in maintaining the biological diversity and consequently the functional diversity of soil
systems.
2. Metabiosis defined
GarreÁ (1887) coined the term metabiosis, which in
The New Shorter Oxford English Dictionary (Brown,
1993) is de®ned as `a form of ecological dependence
in which one organism must modify the environment
before the second is able to live in it'. This term is
used by some microbiologists but rarely by other
biologists. A broader de®nition, more appropriate
to ecological situations, is: `a form of ecological
dependence in which one organism or a functional
group of organisms must modify the environment
before the second organism or a functional group of
organisms is able to live or thrive in it' (Waid, 1997).
The organisms responsible for metabiotic changes to
the environment are called metabionts. The changes
caused by metabionts include physical and chemical
modi®cations to habitats on a micro- or a macro-scale.
Some changes are momentary, at the other extreme
they endure for 109 years or more, for example the
presence of photosynthetically-derived O2 in the
atmosphere for 2 109 years or more.
Metabiosis has potential as a useful generic term
(analogous to terms such as parasitism, antagonism,
mutualism, competition, predation) to describe all
non-associative interrelationships between species
or groups of organisms where one dependent species
or group bene®ts as a result of modi®cations to the
environment by the metabiont.
The characteristic features of metabiosis described
by Waid (1997) are summarised in Table 1.
Table 1
Characteristics of metabiosis (modified from Waid, 1997)
1. Significance of relationship to the metabiont
* A metabiont can be unaffected, positively affected or negatively
affected by its interrelationships with dependent organisms
* The interrelationship may maintain and prolong the existence of
the microhabitat, ecosystem or environment in which the metabiont
lives
2. Positive and negative effects of metabiosis
* An environment modified by a metabiont may favour some of
the organisms or functional groups originally present but the
remainder may be disadvantaged
* Some environments modified by metabionts may enable new
genotypes to develop, hence promoting diversification
3. Specificity of metabiotic relationships
* Metabiotic interrelationships may be non-specific or specific
4. Spatial relationships of metabionts to dependent organisms
* Varies from close contact to remoteness
5. Timing, duration and scale of influence of metabiotic effects
* Dependent organisms can coexist with, survive or even develop
after the death of the metabiont
* The duration of a metabiotic effect can range from a momentary
influence to one of 109 years or more
* The dimensions of a metabiont's influence can vary from
Does soil biodiversity depend upon metabiotic activity and in¯uences?
John Saville Waid1,*
School of Microbiology, La Trobe University, Bundoora, Victoria 3083, Australia
Received 1 May 1998; received in revised form 1 October 1998; accepted 25 February 1999
Abstract
A central tenet of biological science is that living organisms modify their environments. Metabiosis is a form of ecological
dependence in which one organism or a functional group of organisms must modify the environment before another organism
or functional group of organisms can live or thrive in it. Soil ecosystems are modi®ed by metabionts to create habitats or
supply resources for which dependent organisms may adapt, evolve and hence diversify. Thus, the diversity of the soil biota
and its functional capabilities may to a large extent be the result of and dependent upon metabiotic activity and in¯uences.
Examples of metabiotic activity in soil ecosystems are: plants are the main source of O2 for the soil biota; decomposers
deplete soil O2 thus enabling the growth of microaerophiles or anaerobes; ammonium released by bacterial deamination
supports the growth of autotrophic ammonium-oxidisers; burrowing earthworms improve soil drainage and create aeration
channels for aerobic biota; detoxi®cation of plant residues by biodegraders permits proliferation of toxin-sensitive organisms;
wood decay by microbes creates habitats for arthropods associated with rotting wood; arthropod comminution of litter
liberates nutrients that facilitate microbial activity. Some metabionts, the panmetabionts, had a global in¯uence by modifying
the biosphere, its evolving biota and by maintaining its biogeochemistry. For example, during the development of the
biosphere the cyanobacteria began the transformation of the atmosphere through the production of O2. The accumulation of
atmospheric O2 had an overwhelming in¯uence on the formation of soils, their physico-chemistry and biology, in particular
the evolution of diverse major groups of aerobic terrestrial organisms (plants, fungi and animals). Many practices to improve
soil fertility, e.g. agro-forestry, mulching, legume inoculation, minimum tillage are applications of metabiotic techniques,
which maintain or improve soil biodiversity and its functional potentiality. Conversely, where ecosystems are degraded
through human activity, e.g. forest destruction, irrigation with saline water, strip-mining, deep tillage, there is an inevitable
reduction of species of animals and plants. It can also result in the loss of some components of the soil community, e.g.
mycorrhizal fungi, macrobiota such as invertebrates, with a consequent reduction in or a loss of the metabiotic activities of
functional groups of the soil biota. Types of metabiotic action include facilitation, ecological engineering, commensalism and
keystone predation. Metabiosis must rank with biotic interrelationships and interactions, such as competition, predation or
mutualism, in its effects upon soil communities and ecosystems. # 1999 Elsevier Science B.V. All rights reserved.
Keywords: Metabiosis; Panmetabiosis; Biotic interactions; Biodiversity; Soil ecosystems; Ecological engineers
*Corresponding author. Tel.: +61-754-458-896; fax: +61-754769-183
E-mail address: jswsbbbud@peg.apc.org (J.S. Waid)
1
Present address: PO Box 760, Buderim, Queensland 4556,
Australia.
1. Introduction
Soil is an outstanding example of a natural system
where living organisms have and still play a major role
in the development of its physico-chemical features.
0929-1393/99/$ ± see front matter # 1999 Elsevier Science B.V. All rights reserved.
PII: S 0 9 2 9 - 1 3 9 3 ( 9 9 ) 0 0 0 3 0 - X
152
J.S. Waid / Applied Soil Ecology 13 (1999) 151±158
Soils contain a motley medley of habitats occupied by
a great diversity of organisms performing an overwhelming variety of functions. Our knowledge of the
abundance and functioning of the various components
of the soil community and of the range of mechanisms
whereby the different soil inhabitants interact with one
another is far from complete. Those interrelationships
where the effects are direct, such as the trophic
mutualistic, parasitic, predatory types of interactions
and competition for resources, have been reasonably
well investigated (Jones et al., 1994). However, there
are a number of indirect types of interrelationships and
interactions that have mechanisms and ecosystem
functions which also need to be fully elucidated.
We need to answer the following questions: Do
indirect types of interactions affect biological and
functional diversity? If so how? Can the effects of
indirect interactions upon biological and functional
diversity be measured? Do indirect interactions confer
resilience on ecosystem functioning by maintaining
the survival of biological diversity and the sustainability of an ecosystem when the environment
changes?
Characteristically organisms bring about physical
and chemical changes to their habitats. These modi®cations, whether ephemeral of enduring, alter the
environment so that some species are enabled to live
and ¯ourish, and others may adapt and evolve to
occupy the novel habitats, while others are decimated
or fail to grow. Metabiosis is a type of biological
action whereby single species or functional groups of
organisms create, maintain or modify environments
and habitats enabling other species to grow, survive
and perhaps evolve. My purpose is to speculate on the
possible involvement of metabiosis by modifying or
creating habitats in maintaining the biological diversity and consequently the functional diversity of soil
systems.
2. Metabiosis defined
GarreÁ (1887) coined the term metabiosis, which in
The New Shorter Oxford English Dictionary (Brown,
1993) is de®ned as `a form of ecological dependence
in which one organism must modify the environment
before the second is able to live in it'. This term is
used by some microbiologists but rarely by other
biologists. A broader de®nition, more appropriate
to ecological situations, is: `a form of ecological
dependence in which one organism or a functional
group of organisms must modify the environment
before the second organism or a functional group of
organisms is able to live or thrive in it' (Waid, 1997).
The organisms responsible for metabiotic changes to
the environment are called metabionts. The changes
caused by metabionts include physical and chemical
modi®cations to habitats on a micro- or a macro-scale.
Some changes are momentary, at the other extreme
they endure for 109 years or more, for example the
presence of photosynthetically-derived O2 in the
atmosphere for 2 109 years or more.
Metabiosis has potential as a useful generic term
(analogous to terms such as parasitism, antagonism,
mutualism, competition, predation) to describe all
non-associative interrelationships between species
or groups of organisms where one dependent species
or group bene®ts as a result of modi®cations to the
environment by the metabiont.
The characteristic features of metabiosis described
by Waid (1997) are summarised in Table 1.
Table 1
Characteristics of metabiosis (modified from Waid, 1997)
1. Significance of relationship to the metabiont
* A metabiont can be unaffected, positively affected or negatively
affected by its interrelationships with dependent organisms
* The interrelationship may maintain and prolong the existence of
the microhabitat, ecosystem or environment in which the metabiont
lives
2. Positive and negative effects of metabiosis
* An environment modified by a metabiont may favour some of
the organisms or functional groups originally present but the
remainder may be disadvantaged
* Some environments modified by metabionts may enable new
genotypes to develop, hence promoting diversification
3. Specificity of metabiotic relationships
* Metabiotic interrelationships may be non-specific or specific
4. Spatial relationships of metabionts to dependent organisms
* Varies from close contact to remoteness
5. Timing, duration and scale of influence of metabiotic effects
* Dependent organisms can coexist with, survive or even develop
after the death of the metabiont
* The duration of a metabiotic effect can range from a momentary
influence to one of 109 years or more
* The dimensions of a metabiont's influence can vary from