Eur. J. Soil Biol. 37 (2001) 213−220 © 2001 Éditions scientifiques et médicales Elsevier SAS. All rights reserved S1164556301010871/FLA A future for soil ecology ? Connecting the system levels: moving from genomes to ecosystems Opening Lecture to the XIII ICSZ “Biodiversity of soil organisms and ecosystem functioning” Herman Eijsackers* Alterra Green World Research, POB 47 6700 AA Wageningen, The Netherlands and Institute for Ecological Studies, Vrije Universiteit Amsterdam, Netherlands Received 18 August 2000; accepted 23 July 2001 Abstract − As an introduction to the XIII ICSZ “Biodiversity of soil organisms and ecosystem functioning” the question is raised what contribution soil ecology has made to general ecology. Although the appearance of soil ecological papers in general ecological journals is limited, soil ecologists have had a major contribution to especially functional aspects of ecology like nutrient release and energy turnover mechanisms, perhaps partly due to the applied character of soil ecology. As a way forward it is suggested to unify further work and scientific discussions according to five research themes: 1. Combined spatial and temporal heterogeneity; 2. Scaling up from individual mobility via distribution patterns to bio-geography; 3. Structural and functional biodiversity: from gene- to ecosystem level; 4. Nutrient cycling/energy transfer at the micro- to macro-level; 5. Adaptability from bacteria to ecosystems: is there a mutual mechanism connecting genetic variation with ecosystems´ adaptive mechanisms? © 2001 Éditions scientifiques et médicales Elsevier SAS micro- and macro-scale connections / nutrient cycling / organism adaptability / soil ecology / spatial and temporal heterogeneity 1. INTRODUCTION 2000 to discuss the way forward in the 21st century (see for an overview [27]). This has been put into a In the present era of molecular biology, frequently broader retrospective view to provide a jumping ramp felt as the enigmatic approach to biological research, it which research lines and developments are the most is often hard to understand the ultimate ecological promising and relevant for the future of soil ecology, consequences of these molecular mechanisms. given the need to protect soils because of their role as To what extent are these generalizing and generic sustainable basis of terrestrial ecosystems. concepts helpful in understanding ecological struc- Questions like ‘what is the functional role of tures and processes that always have been character- enchytraeids in a coniferous forest floor’ are quite ized by specification and diversification? Is it possible normal for soil ecologists. However, if we should ask to forge the chain from molecular to ecosystem struc- the question: ‘What is the functional role of wood- tures and ecosystem-processes? And to what extent are peckers in coniferous forests’, it would be less recog- these insights helpful in a better and more sustainable nisable as a sensible question for ecologists. This state- protection of soils? ment by Per Lundberg is an example of a general The first start for this introduction was a workshop observation: why do soil(ecology) people always think of a group of soil ecologists in Lund (Sweden) end and investigate in functional terms? Is it because of their roots, lying in agronomy and forestry? Is it because of the applied character of their research? Or is it just because it is hard to look into the opaque soil milieu and impossible during your studies to enjoy *Correspondence and reprints: Fax: +31-317-419000. the aesthetic sight of flowered, winged and feathered E-mail address: [email protected] (H. Eijsackers). fellow-creatures as above-ground-ecologists can do? 214 H. Eijsackers / Eur. J. Soil Biol. 37 (2001) 213–220 2. WHAT HAS BEEN TYPICAL IN SOIL 3. WHY SHOULD SOIL ECOLOGISTS ECOLOGY FROM AN ECOLOGICAL CONTRIBUTE LESS TO MAINSTREAM PERSPECTIVE? ECOLOGICAL THEORY; AND WHAT DO THEY HAVE TO OFFER FOR OTHER Some answers on these questions can be derived RESEARCH FIELDS from an analysis of literature references. A certain underestimation of soil ecological research The observations of Bengtsson and Bot [1, 4] beg is certainly not related to the level of research. Com- the question ‘Why do soil ecologists contribute less to paring soil ecological versus general ecological litera- mainstream ecological theory? Is it again this applied ture, Göran Bengtsson (personal comm.) concluded perspective?‘ that the total scope of ‘general ecology’ and ‘soil ecology’ is quite similar, although there are differences Certainly this applied perspective is one of the main in relative attention to different areas e.g. population or reasons. Irrespective of that it seems to be better to ecosystem oriented research. Thus for both groups tackle the question the other way around: what special there are clearly distinguishable periods in which features have soil ecosystem researchers to offer to research on particular issues received most attention; mainstream ecology? For example in 1972 Bouché [5] in approximate historical order: distribution problems, already proposed a concept of ecological categories biodiversity, community issues and competition. From for earthworms (anecic, epigeic, endogeic) which has an analysis [4] of work on soil arthropods in a soil been much later also adopted in other fields of ecology. ecological (Pedobiologia) versus two general ecologi- Also in general soil biologists have been leading in cal journals (Ecology and the Journal of Animal studies on nutrient cycles in terrestrial ecosystems, Ecology) the most prominent difference was the lack especially in relation to carbon, nitrogen and phospho- of theory driven (hypothesis testing) research in soil rus fluxes. See for instance the whole series of ‘green ecology. In Pedobiologia 3 out of 44 papers were books’ resulting from the International Biological theory driven, whereas in Ecology and J. of Animal Programme. Ecology these were 17 out of 20 papers. Most of the Soil ecology is featuring certainly not by easily papers in Pedobiologia were on ecology aspects, observable and colourful looking organisms like but- especially community ecology, while the two other terflies; even the larger groups of organisms in soil are journals had a much more even and wider range called cryptobiota (hidden organisms), not to mention covering also individual and population level, as well the micro-organisms. Further, the black box that soils as evolutionary aspects. Also when we assume/keep in offer asks for specialised sampling and observation mind that Pedobiologia is oriented on more factual and techniques and developing appropriate methodology is applied studies, it illustrates the statement that soil still a problem that needs much attention. On the other ecology is application driven. hand this offers a promising potential. In fact the According to Lee [21], giving a qualitative historic recent development of new identification methodolo- overview on earthworm research, up to the 1950s gies for micro-organisms already caused enormous earthworm research work was entirely confined to progress, e.g. when we look at the recent observations faunistics, phylogeny, biogeography and natural his- on the diversity of bacterial strains [18, 23]. tory, after 1950 ecologically related work started, What soil ecologists do have to offer is: mainly concerned with population biology. Only rather – Their large and extensive experience in working recently a more structural relation was made to the real with an extremely heterogeneous environment. This environment for earthworms: the soil and its condi- heterogeneity influences many of the processes. Many tions, and at a larger scale land management. Satchell organisms, e.g. earthworms, moreover, create their [28] states for research on earthworms that “this was own environment. This illustrates that in the soil, not problem or policy driven but opportunistically as abiotic and biotic processes are closely interlinked and technology evolved in quite other fields; electron must be studied as such. Further, this heterogeneity microscopy resulted in taxonomic revisions (although taught us to work and think in maximum and mini- disputed by other scientists) which in turn contributed mum (sometimes extreme) conditions, next to the to understanding earthworm distribution in relation to usual mean conditions. tectonic plate movement”. Satchellus example on tax- – This combination of abiotic and biotic processes is onomy is interesting especially because the develop- typically illustrated by the case of bioavailability ment of pure science at extremely small spatial scales research. This comprises the physico-chemical avail- has consequences for distribution problems at the ability of chemical compounds in the environment in global scale, hence connecting the different levels of relation to biological uptake mechanisms and internal biological organisation. transport to target organs. This sequential three-step In conclusion soil ecology has its own territory and approach has been worked out for soil contaminants in touches upon mainline ecological issues. However, the framework of soil ecotoxicology, but was already a soil ecological journals may have a somewhat limited long-time topic in nutrient availability. Only when penetration (Citation Index) and cross-reference to bioavailability is studied both from the perspective of other journals. physico-chemical availability and of biological uptake H. Eijsackers / Eur. J. Soil Biol. 37 (2001) 213–220