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3 The Role of the Group in Biodiversity
Pages 223-252

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From page 225...
... Since then, the importance of soils and the organisms within them for many vital ecosystem processes has been identified, for example, cleansing of water, detoxification of wastes, and decay of organic matter. Indeed, it is now recognized that the functioning of soils, the dark material beneath our feet, is critical for the survival of life on the planet in its present form.
From page 226...
... Information on the number and types of soil species and phyla required to decompose plant material or invertebrates might be avail' TABLE 1 Some Ecosystem Services Provided by Soil Biota Biota Ecosystem Services Regulation of major elemental cycles Retention and delivery of nutrients to plants Generation and renewal of soil, and soil fertility Detoxification and decomposition of wastes Modification of the hydrological cycle Mitigation of floods and droughts Translocation of nutrients, particles, and gases Regulation of atmospheric trace gases (production and consumption) Regulation of animal and plant populations Control of potential agricultural pests Foundation of life from which humanity has derived elements of its agricultural, medicinal, and industrial enterprises Source: Modified from Daily (1997)
From page 227...
... Soil bioturbators, while changing the physical and chemical environment of the soil, also transfer other, smaller organisms and soil particles within the soil, constantly creating new soil aggregates and new surfaces as habitats for microorganisms and facilitating topsoil formation. In this way, the soil biota "plows" the soil, mixing organic matter and nutrients essential for life throughout the soil profile.
From page 228...
... There is a poor understanding of the ecological roles played by soil species. Fac' tars contributing to the dearth of knowledge are many and include the following: · The diversity of soil organisms spans many phyla (from microorganisms to arthropods to vertebrates)
From page 229...
... As a result, the approach to studying the link between organisms and ecosystem processes has been to place soil organisms in functional groups at a gross level for example, considering all oribatid mites and springtails that feed on fungi to be fungivores, all mesostigmatid mites to be predators of other micro' fauna, and so on. The taxonomic and ecological limitations of this approach have been emphasized (Moore and others 1996; Walter and others 1988~.
From page 230...
... Viruses are rarely con' sidered even though they can be potential biological control agents for soilborne pathogens of plants or plant pests. The importance of these microorganisms to ecosystem function is detailed in Lynch and others (this volume)
From page 232...
... In other groups, some of the species live outside the soil; estimates of total species in these groups include bacteria, 1,000,000; fungi 1,500,000; algae, 400,000; Nematoda, 1,000,000; protozoa, 200,000 (Hammond and others 1995~; acari, 348,500-900,000 (Walter, personal communication; Walter and others 1998~; and Diplopoda, 50,000-60,000 (Hoffman 1982b, 1990~. These estimates of total existing species could be low; the soil component of biodiversity has traditionally been underappreciated and poorly described relative to aboveground species because of soil organisms' abun' dance and microscopic size and the dearth of soil taxonomists.
From page 233...
... The effects of introductions of soil species on ecosystem functioning constitutes a new field of study by aboveground ecologists, but it is a well-established field among agriculturalists. An example of the introduction of an alien species from Asia into a natural ecosystem in the United States is the earthworm species Amynthas h~'voyanus, which reduced New York forest-floor organic matter and increased water runoff and soil erosion (Burtelow and others 1998~.
From page 234...
... What is difficult to assess is the importance of the interactions of functional groups or individual species with other soil biota in the food web and how these perhaps less noticeable interactive effects influence eco' system processes. Soil biodiversity is adversely affected by human induced disturbances that can be classified as physical (plowing, desertification, and landfill)
From page 235...
... Programs such as the Tropical Soil Biology Fertility Program (Swift 1997b) , which has been going on for 11 years, are using international experiments that incorporate available information on soil biota and ecosystem processes to develop sustainable soil management in tropical agriculture.
From page 236...
... and international cross-site experiments with predictive models to quantify the relationship of soil biodiversity to critical ecosystem processes on various spatial scales (see Freckman 1994 for examples of experiments, http://www.nrel.colostate.edu/soil/lifeinthesoil.html)
From page 237...
... Madison WI: Soil Science Society of America.
From page 238...
... 1993. Making greater use of introduced microorganisms for biological control of plant pathogens.
From page 239...
... 1987. Biological control.
From page 240...
... of Ornithology, American Museum of Natural History. Thematic Issue: soil biota and global change.
From page 241...
... 1997. Linking biodiversity and ecosystem functioning of soils and sediments.
From page 242...
... Indeed, most well-studied bioremediation experiments and many examples of effective biological control show that natural, or "intrinsic," processes are at least as important in achieving economic ends as specific and targeted biotechnological interventions. This paper suggests that exploitation of microbial communities is a potentially rewarding alternative to the "classical" or "single-species" biotechnological approach.
From page 243...
... Such matches appear to be the exception rather than the rule. Involvement of Many Organisms in "Natural" Biological Control Soil communities comprise a large variety of microbial species.
From page 244...
... That approach is based on little understanding of host-parasite population dynamics, and the selection of agents for development is complicated by issues of ease of culture and product shelf-life. Biological control of cyst nematodes provides a good example; NematopEtora gynophila and Pasteuria penetrans are thought to be important agents of nematode control in natural soil (Davies and others 1992; Kerry and others 1982)
From page 245...
... Suppressive soils need not be only "hunting grounds" for potential biological control products; an understanding of suppressive~soil community ecology is likely to lead to aug' mentative and manipulative management practices that are of considerable eco' nomic benefit.
From page 246...
... Complex Interactions' Biological Diversity' and the Exploitation of Intrinsic Bioremediation Processes Molecular studies have shown that diverse microbial species assemblages (and genes) are involved in the complete catabolism of complex substrates (for ex' ample, Vallaeys and others 1995~.
From page 247...
... As Hamer (1993) has stated, the utility of genetically engineered microorganisms in bioremediation processes is likely to be restricted to specific in situ and ex situ applications because recombinants fail to match the degradative abilities of natural microbial species assemblages (despite the addition of metabolic capabilities)
From page 248...
... This is well documented and often cited to support "species conservation" (Wilson 1992~. However, diverse microbial species assemblages can act in concert (via complex ecosystem level interactions)
From page 249...
... Similarly, shared preferences for specific hosts are well documented among potential biological control agents. This could suggest "redundancy" in the normal community state but have considerable eco' nomic value in "variable" natural systems.
From page 250...
... 1992c. The effectiveness of Verticillium chlamydosporium as a biological control agent for Meloidogyne incognita in pot tests in three soils and for control of M
From page 251...
... 1997. Environmental influences on the microbial degradation rate of Exxon Valdez oil on the shorelines of Prince William Sound, Alaska.


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