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Digitale Medien

Rapid incorporation of carbon from fresh residues into newly formed stable microaggregates within earthworm casts (2004)

Bossuyt, H. ; Six, J. ; Hendrix, P. F.

Oxford, UK; Malden, USA : Blackwell Science Ltd

European journal of soil science 55 (2004), S. 0

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ISSN: 1365-2389

Quelle: Blackwell Publishing Journal Backfiles 1879-2005

Thema: Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft

Notizen: Earthworms play an important role in protecting carbon in the soil, but the exact influence of their activity on the distribution and protection of C is still poorly understood. We investigated the effect of earthworms on the formation of stable microaggregates inside newly formed macroaggregates and the distribution of C in them. We crushed (〈 250 µm) soil, and subjected it to three treatments: (i) soil + 13C-labelled residue + earthworms (these added after 8 days' incubation), (ii) soil + 13C-labelled residue, and (iii) control (no additions), and then incubated it for 20 days. At the end, we measured the aggregate size distribution, total C and 13C, and we isolated microaggregates (53–250 µm) from macroaggregates (〉 250 µm) formed. The 13C in fine particulate organic matter between and within the microaggregates was determined. Earthworms helped to form large macroaggregates (〉 2000 µm). These large macroaggregates contained four times more stable microaggregates than those from samples without earthworms. There was more particulate organic matter within and between microaggregates in macroaggregates in the presence of earthworms. The larger amounts of organic matter inside stable microaggregates in casts than in bulk soil after 12 days of incubation (140 mg 13C kg−1 soil compared with 20 mg 13C kg−1 soil) indicates that these microaggregates are formed rapidly around freshly incorporated residues within casts. In conclusion, earthworms have a direct impact on the formation of stable microaggregates and the incorporation of organic matter inside these microaggregates, and it seems likely that their activity is of great significance for the long-term stabilization of organic matter in soils.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1111/j.1351-0754.2004.00603.x

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Digitale Medien

Population dynamics of Enchytraeidae (Oligochaeta) in different agricultural systems (1997)

van Vliet, P. C. J. ; Coleman, D. C. ; Hendrix, P. F.

Springer

Biology and fertility of soils 25 (1997), S. 123-129

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ISSN: 1432-0789

Schlagwort(e): Key words Enchytraeidae ; Population dynamics ; Soil moisture ; Soil management ; Vertical distribution ; Conventional tillage ; No-tillage

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft

Notizen: Abstract Organic matter and abiotic conditions seem to influence distribution patterns of Enchytraeidae. In this study effects of changes in management practices on population dynamics of enchytraeids were determined. At two sites (in Athens and Griffin, GA) parts of a fescue (FE) field were converted into conventional tillage (CT) and no-tillage (NT) plots and changes in densities and depth distribution of enchytraeids were followed for 3 years. A site at Watkinsville, containing various soil textures and characterised by very low organic carbon content, which was converted into no-tillage 4 years earlier, was also sampled. Significant reductions in enchytraeid densities, after conversion of fescue into CT, were only found at Griffin. The management practices affected the vertical distribution of enchytraeids. In fescue and NT more enchytraeids were found in the 0–5cm than in the 5–15cm layer. In conventional tillage fields enchytraeids were more evenly distributed over the profile or more abundant in the 5–15cm layer. Management also affected the timing of population dynamics in the different plots. At two sample dates high abundances were found in CT plots only, not in any of the other plots. Enchytraeids were larger at Athens than at Griffin and Watkinsville and contained more soil particles in their gut. At Athens enchytraeids will presumably contribute more to the development of soil structure than at the other sites. We conclude that management affects vertical enchytraeid distributions in soil and changes the timing of population dynamics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/s003740050291

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Digitale Medien

Earthworms and enchytraeids in conventional and no-tillage agroecosystems: A biocide approach to assess their role in organic matter breakdown (1990)

Parmelee, R. W. ; Beare, M. H. ; Cheng, W. ; [weitere]

Springer

Biology and fertility of soils 10 (1990), S. 1-10

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ISSN: 1432-0789

Schlagwort(e): Earthworm ; Enchytraeid ; Tillage ; Organic matter ; Biocide ; Agroecosystems

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft

Notizen: Summary Earthworm and enchytraeid densities and biomass were sampled over an 18-month period in conventional and no-tillage agroecosystems. Overall, earthworm densities and biomass in the no-till system were 70% greater than under conventional tilling, and enchytraeid densities and biomass in the no-till system were 50%–60% greater. To assess the role of annelids in the breakdown of soil organic matter, carbofuran was applied to field enclosures and target (earthworm and enchytraeid biomass, standing stocks of organic matter) and non-target effects (bacteria, fungi, protozoa, nematode and microarthropod densities, litter decay rates, plant biomass) were determined in two 10-month studies. In the winter-fall study, carbofuran reduced the annelid biomass, and total soil organic matter standing stocks were 47% greater under no-till with carbofuran compared to control enclosures. Twelve percent of the difference could have been due to non-target effects of carbofuran, as determined from litterbag decay rates. In the summer-spring study, carbofuran again significantly reduced the annelid biomass, and treated pens in the no-till area had significantly greater standing stocks of fine organic matter (43%–45%). Although the densities of bacteria and nematodes were reduced in carbofuran-treated litterbags under a no-till system, the rates of decay were not reduced and estimates of the amount of organic matter processed could not be adjusted for non-target effects. A 76% difference in the standing stock of coarse organic matter between control and carbofuran-treated pens in the conventional-till system indicated further non-target effects. We concluded that our estimates of the amount of organic matter processed by annelids in no-till and conventionally tilled agroecosystems represented a maximum potential because of the confounding non-target effects of carbofuran.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00336117

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Digitale Medien

A hierarchical approach to evaluating the significance of soil biodiversity to biogeochemical cycling (1995)

Beare, M. H. ; Coleman, D. C. ; Crossley, D. A. ; [weitere]

Springer

Plant and soil 170 (1995), S. 5-22

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ISSN: 1573-5036

Schlagwort(e): biodiversity ; biotic interactions ; biogeochemistry ; detritusphere ; drilosphere ; functional groups ; keystone species ; microsites ; nutrient cycling ; porosphere ; rhizosphere ; spatial heterogeneity

Quelle: Springer Online Journal Archives 1860-2000

Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft

Notizen: Abstract The significance of biodiversity to biogeochemical cycling is viewed most directly through the specific biogeochemical transformations that organisms perform. Although functional diversity in soils can be great, it is exceeded to a high degree by the richness of soil species. It is generally inferred from this richness that soil systems have a high level of functional redundancy. As such, indices of species richness probably contribute little to understanding the functioning of soil ecosystems. Another approach stresses the value of identifying “keystone” organisms, that is those that play an exceptionally important role in determining the structure and function of ecosystems. Both views tend to ignore the importance of biodiversity in maintaining the numerous and complex interactions among organisms in soils and their contributions to biogeochemical cycling. We describe some of those interactions and their importance to ecosystem function. Soil organisms alter the physical, chemical and biological properties of soils in innumerable ways. The composition and structure of biotic communities at one hierarchical level can influence the spatial heterogeneity of resource and refuge patches at other hierarchical levels. This spatial heterogeneity is supported by a number of biologically relevant spheres of influence that include the detritusphere, the drilosphere, the porosphere, the aggregatusphere and the rhizosphere. Each has fairly distinct properties that operate at different spatial scales. We discuss how these properties may function in regulating the interactions among organisms and the biogeochemical processes that they mediate. It is through the formation of a spatially and temporally heterogeneous structure that biodiversity may contribute most significantly to the functioning of soil ecosystems. Real advances in understanding the significance of biodiversity to biogeochemical cycling will come from taking a broader view of biodiversity. Such a view will necessarily encompass many levels of resolution including: 1) the importance of biodiversity to specific biogenic transformations, 2) the complexity and specificity of biotic interactions in soils that regulate biogeochemical cycling, and 3) how biodiversity may operate at different hierarchically arranged spatial and temporal scales to influence the structure and function of ecosystems.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF02183051

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