Population and community ecology and
                                               ecosystem ecology provide two different
                                               perspectives on ecological systems, their
                                               structure, their functioning, their dynamics
                                               and their evolution. While population and
                                               community ecology takes as its starting
                                               point the population and its interactions with
                                               other populations, ecosystem ecology is
                                               mainly concerned with the flows of matter
                                               and energy in the overall system composed
                                               of biological organisms and their abiotic
                                               environment.
       Linking Community and Ecosystem Ecology
       (LINKECOL)                              However, populations and communities do
       An ESF scientific programme             not exist in isolation; they are parts of
                                               ecosystems, and, as such, they are subjected
                                               to constraints arising from ecosystem
                                               functioning, in particular energy dissipation
                                               and nutrient cycling.  At the same time,
                                               ecosystems do not exist without their biologi-
                                               cal components; the latter impose their own
                                               constraints on ecosystem processes, as the
                                               disruptions generated by some biological
                                               invasions attest. And in the face of the
                                               growing threat of a massive loss of biologi-
                                               cal diversity, interest is increasing concern-
                                               ing the role of  biodiversity in ecosystem
                                               processes.
                                               This has created an urgent need to integrate
                                               the two subdisciplines and it is the principal
                                               aim of the LINKECOL programme to
                                               unify these different perspectives.  Such
                                               integration is essential not only to advance
                                               our fundamental understanding of natural
                                               and managed ecosystems but also to provide
                                               answers to more applied questions such as
                                               the impacts of biodiversity loss or species
       The European Science                    invasions on ecosystem sustainability.
       Foundation acts
       as a catalyst
       for the development
       of science by bringing
       together leading scientists
       and funding agencies
       to debate, plan and
       implement pan-European
       initiatives.
                                      1
                                                                               This separation of the two subdisci-
                                                                               plines is understandable as they
                                                                               partly address issues at different
                                                                               hierarchical levels and different
                                                                               spatial and temporal scales. But it is
                                                                               harmful insofar as it is an obstacle to
                                                                               their unity and mutual enrichment.
                                                                               Populations and communities do not
                                                                               exist in isolation; they are parts of
                                                                               ecosystems, and, as such, they are
                                                                               subjected to constraints arising from
                                                                               ecosystem functioning, in particular
                                                                               energy dissipation and nutrient
                                                                               cycling. These constraints can deeply
                                                                               alter the nature of species interac-
                                                                               tions and community properties such
                           Scientific background                               as food-web stability. On the other
                                                                               hand, ecosystems do not exist with-
                                      The need for integration of popula-      out their biological components; the
                                      tion/community and ecosystem             latter impose their own constraints
                                      ecology                                  on ecosystem processes, as the
                                      The vigorous growth in ecology from      disruptions generated by some
                                      its origins in the early years of the    biological invasions attest. In the face
                                      20th century has been accompanied        of the growing threat of a massive
                                      by the creation of numerous subdis-      loss of biological diversity, interest is
                                      ciplines. Although specialisation may    increasing concerning the role of
                                      be inevitable, it also creates problems  biodiversity in ecosystem processes.
                                      because conceptual frameworks in         There is today an urgent need for
                                      different subdisciplines often diverge   integration of the two subdisciplines.
                                      over time. This is nowhere more          Such an integration is already emerg-
                                      apparent than between two of the         ing on a world-wide scale as well as in
                                      major subdisciplines of ecology:         Europe, as a result of both basic and
                                      population and community ecology         applied scientific questions: How will
                                      on the one hand and ecosystem            changes in species and genetic
                                      ecology on the other. These two          diversity affect ecosystem processes
                                      subdisciplines have grown largely        and the related services they provide
                                      independently, each having its own       to humankind? How will these
                                      concepts, theories and methodolo-        changes affect the stability of ecosys-
                                      gies. Population and community           tems, and their ability to withstand
                                      ecology is mainly concerned with the     natural and anthropogenic perturba-
                                      dynamics, evolution, diversity and       tions? How do biological organisms
                                      complexity of the biological compo-      and abiotic factors interact to regu-
                                      nents of ecosystems; its starting        late the flow of energy, the structure
                                      point is the population and its          of the food web and the cycling of
                                      interactions with other populations.     chemical elements in aquatic and
                                      Ecosystem ecology is mainly con-         terrestrial ecosystems? On a large
                                      cerned with the functioning of the       time scale, are plants, animals and
                                      overall system composed of biologi-      micro-organisms involved in mutu-
                                      cal organisms and their abiotic          alistic relationships mediated by
                                      environment; its starting point is the   material cycling despite their appar-
                                      flow of matter or energy among           ent immediate antagonism? Can
                                      functional compartments.
                                                                             2
                         indirect interactions evolve by
                         natural selection and significantly
                         influence species traits? These are
                         some examples of the questions that
                         have recently received growing
                         attention.
                         Both population, community and
                         ecosystem ecology have a long
                         history in Europe, but, as mentioned
                         above, these subdisciplines have had
                         largely separate developments, with
                         different strengths in different
                         countries and laboratories. Attempts
                         towards the goal of integration of
                         the subdisciplines are developing
                         rapidly through new experimental             knowledge and expertise, and attract                The effects of plant species
                         and theoretical approaches, but they         new groups and researchers to the               diversity on ecosystem processes
                         are still dispersed, both scientifically     field. It will also provide a European              are investigated using field
                         and geographically. European ecology         contribution to the Diversitas and                    experiments in European
                                                                                                                                      grasslands.
                         would greatly benefit from a co-             IGBP-GCTE international                                     © N. Buchmann
                         ordinated effort to stimulate ex-            programmes. The programme will be
                         changes of ideas, of new theoretical         centred on the three main scientific
                         insights, of new experimental                themes:
                         systems, and of researchers among            1. Species diversity and ecosystem
                         European countries.                          processes;
                                                                      2. Ecology and evolution of indirect
                                                                      effects in ecosystems;
             The ESF programme                                        3. Biological invasions and ecosystem
                                                                      processes.
                         The present programme aims at                1. Species diversity and ecosystem
                         unifying the perspectives of commu-          processes
                         nity and ecosystems ecology. This is         Until recently little attention has
                         an important scientific challenge,           been given to the ecological conse-
                         both to improve our fundamental              quences of the losses of biodiversity.
                         understanding of natural and man-            Most concerns over biodiversity
                         aged ecosystems and to provide               losses have focused on the important
                         appropriate answers to more applied          ethical and aesthetic dimensions of
                         questions such as the impacts of             biotic impoverishment or on the
                         biodiversity loss or species invasions       losses of potentially economically
                         on ecosystem sustainability. The goal        valuable crops or drugs. There is now
                         of the programme is to promote the           growing recognition, however, that
                         development and integration of               ecosystems operate in a manner that
                         research linking community and               provides free ecological services to
                         ecosystem ecology across Europe.             humans. These services are derived
                         The programme will strengthen                from the normal functioning of
                         interactions among groups from               ecosystems, raising the important
                         different countries and different            question whether depauperate
                         scientific traditions, stimulate the         ecosystems perform differently or
                         development of ideas, support the            less efficiently than the more species-
                         initiation of collaborative research         rich systems from which they are
                         projects, facilitate the exchange of         derived.
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                                                                               cycling, thus affecting ecosystem
                                                                               functioning.
                                                                               This part of LINKECOL has the
                                                                               following aims:
                                                                                  
                                                                               . To synthesise current experimental
                                                                               and theoretical advances in the area
                                                                               of the effect of biodiversity on the
                                                                               magnitude and stability of ecosystem
                                                                               processes.
                                                                                  
                                                                               . To develop innovative approaches
                                                                               in this area.
                                                                                  
                                                                               . To contribute to an understanding
                                                                               of the mechanistic basis of the
                                                                               response – or lack of response – of
                                                                               ecosystem processes to species
                                                                               diversity.
          The loss of plant            Several hypotheses have been pro-          
          species diversity            posed on this topic, ranging from one   . To investigate the functional
          reduces primary              extreme stating that all species are    properties, at the aggregated ecosys-
          production in                unique in their contribution to         tem level, of mechanistic theories of
          European                                                             interspecific competition and coex-
          grasslands                   ecosystem performance to the other      istence based on resource consump-
          (Hector et al.,              extreme stating that most species in a
          Science                      functional group are redundant in       tion, space occupancy or response to
          286:1123-                    their ecosystem impact. Another         disturbances.
          1127, 1999).                                                            
                                       possibility is the  “insurance hypoth-  . To investigate, both theoretically
                                       esis” : High species richness may not   and experimentally, the interplay
                                       always play a significant role in       between ecosystem processes and
                                       maintaining ecosystem processes         community assembly.
                                       under constant or benign environ-          
                                       mental conditions, but it may           . To examine how environmental
                                       nevertheless be important for main-     changes interact with changes in
                                       taining their stability under chang-    biological diversity in determining
                                       ing environmental conditions.           ecosystem processes.
                                       Global or more local environmental      2. Ecology and evolution of indirect
                                       changes such as increased atmo-         effects in ecosystems
                                       spheric CO  concentration or N          Interactions between organisms and
                                                  2                            between organisms and their abiotic
                                       deposition are likely to interact with  environment are not only direct, but
                                       changes in biodiversity and ecosys-     they also have a great number of
                                       tem processes. These environmental      indirect effects on other organisms
                                       changes may have profound effects       and processes. Some of these indirect
                                       on ecosystem processes such as          effects have a considerable impact on
                                       productivity, soil acidification and    the functioning of ecosystems. Well-
                                       nutrient mineralisation, which affect   known examples are keystone preda-
                                       the competitive balance between         tion, indirect mutualisms between
                                       plant species and result in changes in  plants and predators, or indirect
                                       species diversity and composition.      facilitation by ecosystem engineers.
                                       These changes in species diversity
                                       and composition in turn may have
                                       important impacts on soil organic
                                       matter dynamics and nutrient
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