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In dit rapport wordt beschreven wat ecologische kwaliteit van bodem is, en op welke wijze deze gekwantificeerd kan worden. In bodem vinden een groot aantal processen plaats, die van belang zijn voor de mens (nutsfuncties), omdat ze bijdragen aan bijvoorbeeld de voedselvoorziening, het type en de kwaliteit van de natuur en de levering van schoon grondwater (voor de productie van drinkwater). Bodemorganismen spelen een belangrijke rol in die processen. Bij een duurzaam gebruik van de bodem ishetvan belang, om de bodemorganismen zodanig te gebruiken en te beheren, dat deze processen ook voor de toekomst gewaarborgd zijn. Hierbij moet ook de mogelijkheid beschikbaar blijven om het bodemgebruik te veranderen. Ter onderbouwing van het duurzaamheidsbeleid van de bodem wordt gewerkt aan de ontwikkeling van een bodembiologische indicator (BoBI) voor gebruik op nationale schaal. Daarvoor worden ecologische gegevens over de soortdiversiteit, het aantal organismen per soort en deactiviteitvan de organismen verzameld

Dit rapport is een update van het eerste rapport uit 2000. Het is voortgekomen uit het werkplan van het LNV-onderzoeksprogramma `Koepelprogramma Biologische Landbouw¿, waarin LNV vraagt onder andere het kerngroeprapport te actualiseren op met name de visie op biologische landbouw (onderzoek en onderwijs) en de prioritaire onderzoeksthema¿s voor de periode 2004 - 2008. Behalve een actualisatie, geeft de Kerngroep Biologische Landbouw 2003 in dit rapport ook een schets en evaluatie van de onderzoeks- en onderwijsinspanningen van 2000 tot nu. Hetzelfde doet ze ook voor de taken en doelstellingen van het in 2001 opgerichte Innovatiecentrum Biologische Landbouw van Wageningen UR. Tevens schetst ze een gewenste toekomstige ontwikkeling voor dit centrum

We analysed data from descriptive and experimental studies on the possible relationships between plants, nematodes and mycorrhizal fungi in (successional) plant communities in The Netherlands. A key role for pathogenic nematodes in cyclic succession in grazed grassland confirmed similar results in foredune succession. Plants with clonal growth forms appear to be particularly susceptible to pathogenic fungi. A large role for ectomycorrhiza at the species level (functional composition) was observed in determining the effects of acid rain and increased atmospheric CO2 on nutrient transfer to trees. Field studies showed a correlation between species richness of ectomycorrhizal fungi and hyphal-feeding nematodes in one case, but not in another. Population growth of hyphal-feeding nematodes on ectomycorrhizal hyphae was found to be strongly dependent on plant-mediated palatability of the fungus. We conclude that the limited available evidence suggests the importance of functional composition of species in determining interactions between plants, nematodes and mycorrhizal fungi, but the degree to which functional redundancy exists within the nematodes and within the mycorrhizal fungi warrants further investigation.

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/Université 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 sádkách 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

De risico's van het gebruik van gewasbeschermingsmiddelen voor het milieu worden door het College voor de Toelating van Bestrijdingsmiddelen volgens een getrapte procedure beoordeeld

The relative contribution of different soil organism groups to nutrient cycling has been quantified for a number of ecosystems. Some functions, particularly within the N-cycle, are carried out by very specific organisms. Others, including those of decomposition and nutrient release from organic inputs are, however, mediated by a diverse group of bacteria, protozoa, fungi and invertebrate animals. Many authors have hypothesized that there is a high degree of equivalence and flexibility in function within this decomposer community and thence a substantial extent of redundancy in species richness and resilience in functional capacity. Three case studies are presented to examine the relationship between soil biodiversity and nitrogen cycling under global change in ecosystem types from three latitudes, i.e. tundra, temperate grassland and tropical rainforest. In all three ecosystems evidence exists for the potential impact of global change factors (temperature change, COP enrichment, land-use-change) on the composition and diversity of the soil community as well as on various aspects of the nitrogen and other cycles. There is, however, very little unequivocal evidence of direct causal linkage between species richness and nutrient cycling efficiency. Most of the changes detected are shifts in the influence of major functional groups of the soil biota (e.g. between microflora and fauna in decomposition). There seem to be few data, however, from which to judge the significance of changes in diversity within functional groups. Nonetheless the soil biota are hypothesized to be a sensitive link between plant detritus and the availability of nutrients to plant uptake. Any factors affecting the quantity or quality of plant detritus is likely to change this link. Rigorous experimentation on the relationships between soil species richness and the regulation or resilience of nutrient cycles under global change thus remains a high priority.

All current mathematical models of the soil system are underpinned by a wealth of research into soil biology and new research continues to improve the description of the real world by mathematical models. In this review we examine the various approaches for describing soil biology in mathematical models and discuss the use of each type of model in global change research. The approaches represented among models participating in the Global Change and Terrestrial Ecosystems (GCTE) Soil Organic Matter Network (SOMNET) are described. We examine the relative advantages and constraints of each modelling approach and, using these, suggest appropriate uses of each. We show that for predictive purposes at ecosystem scale and higher, process-orientated models (which have only an implicit description of soil organisms) are most commonly used. As a research tool at the ecosystem level, both process-orientated and organism-orientated models (in which functional or taxonomic groups of soil organisms are explicitly described) are commonly used. Because of uncertainties introduced in internal model parameter estimation and system feedbacks, the predictive use of organism-orientated models at the ecosystem scale and larger is currently less feasible than is the use of process-orientated models. In some specific circumstances, however, an explicit description of some functional groups of soil organisms within models may be required to adequately describe the effects of global change. No existing models can adequately predict the feedback between global change, a change in soil community function, and the response of the changed system to future global change. To find out if these feedbacks exist and to what extent they affect future global change, more research is urgently required into the response of soil community function to global change and its potential ecosystem-level effects.

Effects of soil macrofauna, micro-environment and mulch quantity were investigated on an acid Ultisol in a high-rainfall area in S.E. Nigeria, using litterbags or littertubes with leaves from the trees of an alley cropping system with t Flemingia congesta or t Dactyladenia barteri as hedgerow species.There was no effect of mulch quantity on the rate of decomposition. Soil macrofauna contributed to between 30 and 40% of mulch decomposition over the period of approximately 50% of disappearance of the original material. The faunal effect became apparent after a longer incubation period (>20 weeks) with the slower decomposing t Dactyladenia than with the t Flemingia mulch (immediate effect). This is presumably related to t Dactyladenia's higher lignin content (40% compared to 22% for t Flemingia). The t Flemingia mulch decomposed faster in alley cropping with t Dactyladenia hedgerow than with t Flemingia hedgerow, irrespective of faunal access, suggesting a microclimate efffect on decomposition. There were no marked changes in chemical composition of the mulches with decomposition period, except for a rapid decrease of K content in both mulches and a rapid increase in lignin content of the t Flemingia mulch within the first 10 days of decomposition, which indicates that early decomposition affected the relatively easily degradable compounds.