Showing papers by "Volkmar Wolters published in 2000"

Interactions between Aboveground and Belowground Biodiversity in Terrestrial Ecosystems: Patterns, Mechanisms, and Feedbacks

Abstract: Assistant professor in the Department of Biology at Western Washington University, Bellingham, Washington 98225-9160 10: Professor at the Laboratoire d'Ecologie de Sols Tropicaux, ORSTOM/Universite Paris VI, 32 Avenue Henri Varagnat, 93143 Bondy, France 11: Senior scientist at the Centre for Terrestrial Ecology, Netherlands Institute of Ecology, 6666 ZG Heteren, Netherlands Utrecht, Netherlands 12: Professor at the Department of Environmental Studies, University of Utrecht, Utrecht, Netherlands 13: Professor at the Institute of Soil Biology, Academy of Sciences of the Czech Republic, Na sadkach 7, 370 05 Ceske Budejovice, Czech Republic 14: Professor at the Department of Environmental Science, Policy,and Management, University of California, Berkeley, California 94720-3110 15: Professor at the Center for Microbial Ecology, Michigan State University, 540 Plant and Soil Science Building, East Lansing, Michigan 48824-1325 16: Professor at the Department of Animal Ecology, Justus Liebig University of Giessen, Heinrich-Buff-Ring 26-32 (IFZ), D-35392 Giessen, Germany 2: Professor at the Queen Mary and Westfield College, School of Biological Sciences, University of London, London E1 4NS, United Kingdom 3: Research professor and the director of the Centre for Agri-Environmental Research, Department of Agriculture, University of Reading, Earley Gate, Reading RG6 6AT, United Kingdom 4: Professor of Soil Biology and Biological Soil Quality and director of the Department of Environmental Sciences, Wageningen University, 6700 EC Wageningen, Netherlands 5: Professor at the Centre for Biodiversity and Bioresources, School of Biological Sciences, Macquarie University, Sydney, New South Wales 2109, Australia 6: Chair, SCOPE Committee on Soil and Sediment Biodiversity and Ecosystem Functioning, and professor and director, Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, Colorado 80523 7: Scientist at Landcare Research, Lincoln, New Zealand 8: Research professor in the Institute of Ecology at the University of Georgia, 102 Ecology Annex, Athens, Georgia 30602-2360 9: Professor at the Department of Soil Science and Agricultural Engineering, University of Zimbabwe, Mount Pleasant, Harare, Zimbabwe

Invertebrate control of soil organic matter stability

Abstract: The control of soil organic matter (SOM) stability by soil invertebrates is evaluated in terms of their impact on the inherent recalcitrance, accessibility to microorganisms, and interaction with stabilizing substances of organic compounds. Present knowledge on internal (ingestion and associated transformations) and external (defecation, constructions) control mechanisms of soil invertebrates is also reviewed. Soil animals contribute to the stabilization and destabilization of SOM by simultaneously affecting chemical, physical, and microbial processes over several orders of magnitude. A very important aspect of this is that invertebrates at higher trophic levels create feedback mechanisms that modify the spatio-temporal framework in which the micro-food web affects SOM stability. Quantification of non-trophic and indirect effects is thus essential in order to understand the long-term effects of soil biota on SOM turnover. It is hypothesized that the activities of invertebrates which lead to an increase in SOM stability partly evolved as an adaptation to the need for increasing the suitability of their soil habitat. Several gaps in knowledge are identified: food selection and associated changes in C pools, differential effects on SOM turnover, specific associations with microorganisms, effects on dissolution and desorption reactions, humus-forming and humus-degrading processes in gut and faeces, and the modification of invertebrate effects by environmental variables. Future studies must not be confined merely to a mechanistic analysis of invertebrate control of SOM stability, but also pay considerable attention to the functional and evolutionary aspects of animal diversity in soil. This alone will allow an integration of biological expertise in order to develop new strategies of soil management which can be applied under a variety of environmental conditions.

Effects of Global Changes on Above- and Belowground Biodiversity in Terrestrial Ecosystems: Implications for Ecosystem Functioning

Abstract: bove- and belowground organisms are criticalforthe biogeochemical cycles that sustain the Earth,butthere is limited knowledge on the extent to which the biotabelow ground and the functions they perform are dependenton the biota above ground,and vice versa.Hooper et al.(2000) provide a synthesis ofthe patterns and mechanismslinking above- and belowground biodiversity.The close re-lationship between vegetation change and soil carbon (C)dynamics (Jobbagy and Jackson 2000) suggests that anydisruption ofthe coupling between plants and soil organ-isms as a result ofglobal change may have deleterious con-sequences for functioning ofterrestrial ecosystems.However,most ofthe scientific evidence supporting this hypothesiscomes from correlative approaches.The complexity ofthenumerous interactions between various environmental

Microbial activity and functional diversity in the mounds of three different ant species

Abstract: Activity and functional diversity of the soil microflora in the mounds of Myrmica scabrinodis , Lasius niger and L. flavus were investigated. These three ant species strongly differ in foraging strategy and in the mode of mound construction. To take account of changing microbial performances during the cycle of mound building, immature mounds of L. flavus were compared to well established ones. The study was carried out with substrate sampled in the rural district of Hohenahr-Erda (Lahn-Dill Bergland, Central Hesse, Germany). Nest abundance as well as mound size and architecture were recorded for all three species. Microbial activity was quantified by determining the C mineralization rate ( C min ). Functional diversity of the microflora was measured by means of the Biolog method. Additional factors were substrate moisture and pH. Substrate moisture and pH value were not different in the mounds from that in the control. High C min values in all mound types indicate that the mounds of the three ant species investigated form a mosaic of microbial hot spots at the study site. Substrate diversity and evenness were higher in the mounds of both M. scabrinodis and L. niger than in the control soil, but lower in the two mound types of L. flavus . The results of the Biolog measurements suggest that different components of the microbial community were activated in the different mounds. The increase of C min in L. flavus mounds seems to be based on the stimulation of a comparatively small and specialized microbial community. The high microbial activity in the mounds of L. niger and M. scabrinodis , in contrast, is accompanied by an increase in functional diversity. Investigations on the developing L. flavus mounds show that typical features characterizing the microflora in the mounds of this species need a considerable time to develop. It is concluded that ants have an important role as soil engineers and that species specific differences in the effect on the soil microflora are related to feeding strategy and nest architecture. Methodological difficulties arising from the application of the Biolog approach are discussed.

Diversity and Role of Microorganisms

Abstract: The focus on biodiversity changes is often on the conspicuous elements of ecosystems, like trees and flowers, birds and mammals, while the less visible part operating below ground has often been ignored. It is well established that soil communities are among the most species-rich compartments of terrestrial systems (Hall 1996). The implications of this enormous diversity for soil function are still very little known and difficult to address (Wolters 1997). The elucidation of species richness of soils in conjunction with sustainability assessments of soil-mediated ecosystem processes must therefore have a high priority in global biodiversity efforts (Freckman 1994). This holds particularly for soil microorganisms, which have the greatest impact on soil nutrient storage and turnover, but are the most poorly investigated components of the below-ground community. The major factors affecting microbial diversity in soils are climate, substrate conditions and other organisms. In recent times, these factors have been strongly modified by anthropogenic forces.

Diversity and Role of the Decomposer Food Web

Abstract: Only a small part of primary production is consumed by phytophagous organisms (Ellenberg et al. 1986). It is generally agreed that the food web based on detritus is more important for the flow of energy and nutrients through terrestrial ecosystems than the food web based directly on autotrophic production (Swift et al. 1979). The decomposer community that is responsible for this flow is composed of microorganisms and invertebrates. The major components of the decomposer microorganisms are bacteria and fungi. The dominant decomposer fauna groups belong to the Protozoa, Nematoda, Oligochaeta and Arthropoda Fig. 17. There is evidence that the effects of soil organisms on ecosystem functioning critically depend on both the structural diversity of the decomposer community and environmental conditions (Freckman 1994; Hall 1996). However, little information is available concerning the impact of soil biodiversity on the integrity, function and sustain ability of terrestrial ecosystems (Wolters 1998a).