Microbial Feeders
Microbial-feeding mesofauna feed on fungi (including mycorrhizae), algae, slime molds, and bacteria by removing them from clumps of decaying material or soil aggregates (Moore and de Ruiter, 1991). Generally, bacterial-feeding nematodes such as Cephalobidae and Rhabditidae (Neher and Campbell, 1996) are abundant in agricultural ecosystems (Wasilewska, 1979 Popovici, 1984). Consumption of microbes by soil mesofauna alters nutrient availability by stimulating new microbial growth and activity...
Cropping Systems
Microbial communities in agroecosystems change with management history. In continuous cropping systems, cycling of pathogens and antagonists of pathogens and changes in crop yields can often be seen due to alteration in the disease pressure over time. An example of this is the decline of a disease of wheat called take-all decline that is the result of a change in the soil microbial community. The microbial community shifts to favor growth of antagonists of the pathogen Gaeumannomyces graminis...
Soil Microorganisms In Agroecosystems
The soil is full of microorganisms such as bacteria, actinomycetes, fungi, algae, viruses, and protozoa. Microbes are classified in categories based on their utilization of carbon and energy and their nutrient requirements (i.e., phototrophs, chemotrophs, autotrophs, heterotrophs, or lithotrophs). This provides limited information, since many situations overlap and refinement is needed (Alexander, 1977 Walker, 1992 Zak et al., 1994). Bacteria and fungi, as primary decomposers in the cycling of...
Value Of Diversity
Diversity in form and function of biotic communities results in the formation of spatial and temporal heterogeneity of organisms that contributes to the overall function of the ecosystem. Individual taxa may have multiple functions, and several taxa may appear to have similar functions. However, function may not necessarily be redundant, because taxa performing the same function are often isolated spatially, temporally, or by microhabitat preference (Beare et al., 1995). Biodiversity allows...
Sources Of Genetic Diversity In Crops
Genetic variation within a crop gene pool can be found within and among professionally bred varieties, landraces or farmers' varieties, and nondomesticated relatives. In addition, new genetic variation can be introduced through mutations and the transfer of genes from different gene pools. Commercially released varieties aim to combine genes for high productivity with those required to meet different needs and environments. They contain a wealth of useful genes and gene combinations and...
The Prairie Model
Natural grassland ecosystems may represent our best benchmarks for sustainability. Prairies (1) protect the soil from erosion, (2) provide their own nitrogen fertility requirements through the activities of both free-living and symbiotic nitrogen-fixing organisms, (3) avoid devastation by weedy invaders, insect pests, and plant diseases, and (4) run on sunlight and available precipitation (Table 1). The vegetation structure of prairies has two important general characteristics that contribute...
International Collaboration In Biotechnology Research
With the two indicators of agroecosystem quality determined, attention is now placed on examples of new technologies. Examples have been selected that take into account the emerging needs of developing countries regarding biotechnology and their ability to collaborate with international research programs. These examples are taken from information collected from IBS policy seminars and its Registry of Expertise. IBS began to collect, analyze, and discuss with client countries its information on...
Agroecosystem Impacts On Microorganisms
Microbial diversity considerations need to be included in soil quality investigations of agricultural lands (Kennedy and Papendick, 1995). Soil quality is critical to the functioning of any ecosystem (Papendick and Parr, 1992). The quality of a soil can greatly impact land use, sustainability, and productivity. Soil quality, the inherent characteristic of a soil, comprises physical, chemical, and biological properties. These properties may be altered through intensive management practices....
Plant Feeders
Plant-feeding nematodes can become abundant in agricultural ecosystems (Wasilewska, 1979 Popovici, 1984 Neher and Campbell, 1996). These nematodes may affect primary productivity of plants by altering uptake of water and nutrients. These abnormalities may result from changes in root morphology and or physiology. For many agricultural crops, a negative relationship between crop yield and populations of plant-feeding nematodes, such as Meloidogyne, Heterodera, and Praty-lenchus spp., has been...
Linkages Between Biodiversity And Sustainability
Management of agrolandscapes for sustainability both influence and is influenced by biodiversity (Paoletti, 1995). Landscape planning is a process through which the conservation and management of biodiversity can be pursued (Rook-wood, 1995). Turner et al. (1995) stressed that there exists a three-way interaction of biodiversity, ecosystem processes, and landscape dynamics at greater scales. Sustainable agricultural practices leading to increased crop and genetic diversity have resulted in...
Approaches To Conservation
Conservation can be broadly considered in two ways ex situ and in situ. Ex situ conservation involves removing reproductive plant material from its natural setting for maintenance in seed or tissue banks or plantations. Because of the finite nature of any living plant material, ex situ conservation also requires regeneration of the reproductive material at given storage conditions and at species-dependent intervals. In situ conservation is accomplished by protecting plant material in the site...
Habitat Management Crop Structure and Diversity
Habitat management is viewed as a strategy aimed at designing and constructing phytocenotic architecture dominated by plants that support populations of natural enemies (Altieri and Whitcomb, 1979 Altieri, 1983). Diversification of habitat is achieved through crop structure, protective refugia, occurrence of alternative prey host, and supplementary food resources (nectar, pollen). Crop structure is the agroecosystem and its specific characteristics, its biotic composition, seasonality, etc....
References
Crop-weed-insect interactions and the development of pest-stable cropping systems, in Pest Pathogens and Vegetation. The Role of Weeds and Wild Plants in the Ecology of Crop Pests and Diseases, Proc. Univ. of York and Br. Ecol. Soc. and Fed. Br. Plant Path., 1980, J. M. Thresh, Ed., Pitman, Boston, 459-466. Altieri, M. A., 1983. Vegetational designs for insect-habitat management, Environ. Manage., 7 3-7. Altieri, M. A. and Letourneau, D. K., 1982. Vegetation management and...
Biology And Ecology Of Soil Fauna
Soil mesofauna are often categorized by specific feeding behaviors, often depicted as microbial feeders. However, it should be emphasized that many organisms are at least capable of feeding at other trophic groups. As a result, omnivory in soil communities may be more prevalent than assumed previously (Walter et al., 1986 Walter, 1987 Walter et al., 1988 Walter and Ikonen, 1989 Mueller et al., 1990). Our discussion will focus specifically on nematodes, Collembola (springtails), and mites...
The Global Strategy
To assist countries to respond to these imperatives for upgrading the management of animal genetic resources, a framework for a global strategy has been supported and is known as the Strategy for the Management of Farm Animal Genetic Resources. The framework of the Strategy consists of four fundamental components. The Strategy is designed to be comprehensive to emphasize the balanced approach required to understand, utilize, and maintain AnGR better and more cost-effectively over time. The four...
Patterns Of Insect Biodiversity In Agroecosystems
Arthropod diversity has been correlated with aspects of plant diversity in agro-ecosystems. A greater variety of plants conforming to a particular crop pattern should lead to a greater variety of herbivorous insect species, and this in turn should determine a greater diversity of predators and parasites (Figure 5). A greater total biodiversity can then play a key role in optimizing agroecosystem processes and function (Altieri, 1984). Several hypotheses can be offered to support the idea that...
Protozoan Diversity In Agroecosystems
Studies on grasslands (McNaughton, 1977 Tilman, 1996) show that biodiversity stabilizes community and ecosystem processes, although individual species within the system may fluctuate considerably. Tilman (1996) found wide variations in the biomass of the 24 most abundant species of plants in an 11-year study. In a 6-month study of soil ciliates under a spruce stand, Lehle (1992) found that the proportions of the three dominant ciliate species fluctuated widely Cyclidium muscicola ranged from 8...
Research Agenda And Findings That Support The Model
Question 1 Can a Perennial Grain Yield As Well As an Annual Grain Work at the Land Institute to domesticate perennial grains began in 1978 with an inventory of nearly 300 herbaceous perennial species for their suitability to the environment of central Kansas and their promise as seed crops. A second inventory examined the agronomic potential in 4300 accessions of perennial grass species within the C3 genera Bromus, Festuca, Lolium, Agropyron, and Elymus (Leymus). From these inventories, a...
The Nature And Function Of Biodiversity In Agroecosystems
Biodiversity refers to all species of plants, animals, and microorganisms existing and interacting within an ecosystem. In agroecosystems, pollinators, natural enemies, earthworms, and soil microorganisms are all key biodiversity components that play important ecological roles, thus mediating such processes as genetic introgression, natural control, nutrient cycling, decomposition, etc. (Figure 2). The type and abundance of biodiversity in agriculture will differ across agroecosystems which...
Role Of Soil Protozoa
Microarthropods and larger fauna, especially earthworms, increase the rate and amount of mineralization by comminution of organic matter and by redistribution of hot spots of activity through movements. However, mineralization and return of nutrients to plants occur in the water films covering soil aggregates and filling their pores. Here, bacteria and fungi decompose organic matter and immobilize the extracted nutrients into their bodies, but grazing by the microfauna, protozoa, and nematodes...
Plant Biodiversity And Insect Stability In Agroecosystems
From the early 1970s on, the literature provides hundreds of examples of experiments documenting that diversification of cropping systems often leads to reduced herbivore populations (Andow, 1991 Altieri, 1994). Most experiments that have mixed other plant species with the primary host of a specialized herbivore show that, in comparison with diverse crop communities, simple crop communities have greater population densities of specialist herbivores (Root, 1973 Cromartie, 1981 Risch et al.,...
Ecosystem Processes
Micro- and mesofauna contribute directly to ecosystem processes such as decomposition and nutrient cycling in complex and interactive ways (Swift et al., 1979). Bacteria, actinomycetes, fungi, algae, and protozoa are primary decomposers of organic matter. These microorganisms are involved directly with production of humus, cycling of nutrients and energy, elemental fixation, metabolic activity in soil, and the production of complex chemical compounds that cause soil aggregation....
Augmentation Of Beneficials
Augmentation, broadly defined, covers all of the activities that improve the effectiveness of beneficials (DeBach, 1964), such as new species releases (inoculative or inundative), planned genetic change, landscape modification, and so on. The addition of a new species or strain of species into a new area increases species diversity, but it can also affect interspecific relationships and population genetic characteristics. Releases of Mass-Reared Natural Enemies There are two main types of...
Evolution Of The Global Strategy
The Food and Agricultural Organization (FAO) mandate, which is regularly reviewed by its 174 member governments, covers (1) collating, analyzing, and reporting information (2) providing technical assistance, with emphasis on the developing world and (3) providing a forum for intergovernmental discussion and policy development. The member governments have resolved that FAO should lead, coordinate, facilitate and report on the Strategy for the Management of Farm Animal Genetic Resources...
Linkages Between Agricultural And Urban Components Of The Landscape
Figure 3 The development of an agro-urban sustainable (P R 1) landscape. The town marketplace historically was closely linked to the agricultural landscape. Sustain-ability in the modern agro-urban landscape increasingly must be based on the management of suburban areas (ecotones) as natural linkages between urban and agricultural systems. Figure 3 The development of an agro-urban sustainable (P R 1) landscape. The town marketplace historically was closely linked to the agricultural landscape....
Introduction
Today, scientists worldwide are increasingly starting to recognize the role and significance of biodiversity in the functioning of agricultural systems (Swift et al., 1996). Research suggests that, whereas in natural ecosystems the internal regulation of function is substantially a product of plant biodiversity through flows of energy and nutrients and through biological synergisms, this form of control is progressively lost under agricultural intensification and simplification, so that...
Contents
Beneficial Insects and Their Value Biodiversity Crisis Biodiversity in Farmland Biodiversity Monitoring Key Beneficials in Agroecosystems Intraspecific Diversity of Beneficials Biodiversity of Beneficials in Insect Pest Control Systems Importation of Beneficials Natural Enemy Spectrum, Selection, and Adaptation Beneficial Introductions and Specificity Conservation of Beneficials Habitat Management, Crop Structure, and Diversity Food Sprays and Semiochemicals Modification of Chemical Pest...
