DIVERSITY OF SOIL ORGANISMS IN ALPINE AND ARCTIC SOILS IN EUROPE

The diversity of soil organisms and soil ecological processes in different mountain regions of Europe are reviewed. Detailed taxonomic studies on soil organisms have been made in the Alps and in Northern Europe since the end of the last century, however, there is a paucity of data from Southern Europe. Future studies could include the re-sampling of historic study sites to assess if there has been a change in the soil fauna and microorganisms. The role of key abiotic processes such as cryoturbation should be quantified and further research should focus on identifying indicator organisms, keystone species and functional groups. In addition, studies on soil organic matter and particularly on humus forms, the products of soil ecological processes should be encouraged. Ecotones, where the influence of spatial heterogeneity on soil biodiversity is likely to be particularly pronounced, appear to be the most rewarding for such studies.


Institute of Landscape Ecology, University of
Munster, Germany, e-mail: brollg@uni-muenster.de SUMMARY.-Thediversity of soil organisms and soil ecological processes in different mountain regions of Europe are reviewed.Detailed taxonomic studies on soil organisms have been made in the Alps and in Northern Europe since the end of the last century, however, there is a paucity of data from Southern Europe.Future studies could include the re-sampling of historic study sites to assess if there has been a change in the soil fauna and microorganisms.The role of key abiotic processes such as cryoturbation should be quantified and further research should focus on identifying indicator organisms, keystone species and functional groups.In addition, studies on soil organic matter and particularly on humus forms, the products of soil ecological processes should be encouraged.Ecotones, where the influence of spatial heterogeneity on soil biodiversity is likely to be particularly pronounced, appear to be the most rewarding for such studies.
Most recent studies on arctic and alpine biodiversity have been concerned with plant diversity (e.g.CHAPÍN & KÔRNER, 1995) focusing on North America and Russia, where arctic and sub-arctic ecosystem research has had a long tradition (e.g.BEHAN-PELLETIER, 1993;HERSHEY et al, 1995;HOBBIE, 1995;PASTOR, 1995;SCHIMEL, 1995).Relatively little studied have been soil biochemical cycling and interrelationships between soil and plants in alpine (MEYER & THALER, 1995;PASTOR, 1995) or (sub-) arctic areas (BEHAN-PELLETIER & BISSETT, 1992;CALLAGHAN «&: JONASSON, 1995;CALLAGHAN et al, 1995) in Europe.It would be relatively simple to initiate more research in the specialised field of soils and biodiversity because of the broad background in European mountain research with respect to global change and specified future research needs (BENISTON, 1994;GUISAN et al, 1995;PRICE, 1995)

Soil ecology and soil organisms
In this paper soil ecology is defined as the science of interactions among soil biota and between the soil biota and the abiotic environment.Soil ecological research focuses on the interdependence between soil physical and chemical properties and soil organisms, soil organic matter, decomposition, nutrient cycling, and interactions in the rhizosphere.Soil organisms and soil ecological processes respond very sensitively to human disturbances therefore they should be considered in recommendations on environmental change (GISIeifl/., 1997).
Only those soil organisms which play an important role in ecosystem functioning have been taken into account.Apart from microorganisms, these include the following invertebrate groups: lumbricidae, enchytraeidae, collembola, acari, diplopoda, isopoda, nematoda, protozoa and insect larvae.Some small mammals, especially burrowing rodents, may influence soil properties in alpine areas in many ways (e.g.HOLE, 1981;HUNTLY & INOUYE, 1988;MEADOWS & MEADOWS, 1991;BASSANO et a/., 1992;CORTINAS & SEASTEDT, 1996).The interactions between these animals and the vegetation have been investigated (e.g.ANDERSSON & JONASSON, 1986;HANSSON, 1987;MOEN et al, 1993;HERRERO et al, 1994) and an important example is rodent damage to tree seedlings in mountain forests where the regeneration of a whole ecosystem may be affected.Rodents are also important in influencing soil ecological processes in Fennoscandia where many studies have been made on them (e.g.HENTTONEN, 1995).Despite the important role mammals play in soils of arctic and alpine areas they could not be included in this review.

Diversity of soil organisms
Although a large body of literature on biodiversity exists, comparatively few investigations have been carried out on biodiversity of soil organisms to date (e.g.LEE, 1991LEE, , 1994;;BERNARD, 1992 for nematodes; TRÜPER, 1992 for prokaryotes; HAWKSWORTH & COLWELL, 1992;FRECKMAN, 1994;SOMBROEK, 1994).There is a paucity of data at the species level (e.g.GROOMBRIDGE, 1992;HAWKSWORTH & RITCHIE, 1993); only about 11% of estimated bacteria species in the world are described, and the figure for fungi is only 5% (HAWKSWORTH, 1991).In extreme environments such as those in alpine and arctic areas many species are unknown (GROOMBRIDGE, 1992).Many new methods (e.g.molecular biological methods) have been developed for identifying microorganisms that are also available for studying microorganisms in alpine and arctic environments.
The diversity of soil organisms is of great importance for ecosystem functioning.(SCHULZE & MOONEY, 1993;ALLSOPP et al, 1995;COLLINS et al, 1995;LAVELLE et al, 1995;DI CASTRI & YOUNÉS, 1996;HEAL et al, 1996).Most of the reported studies have been made in relation to sustainable agriculture (HAWKSWORTH, 1991;GREENLAND & SZABOLCS, 1994) and natural ecosystems have been of less interest (MOLDENKE et al, 1994).A diverse array of soil organisms is necessary for decomposition and biogeochemical cycles in every ecosystem, natural or managed (LEE, 1991;BEARE et al, 1995).The functioning of nutrient cycles is a good indicator of ecosystem integrity and stability (BERENDSE, 1993;SCHULZE & MOONEY, 1993;COLEMAN et al, 1994).Earlier studies have acknowledged the importance of the diversity of the soil fauna and its role in ecosystem functioning (e.g.WALLWORK, 1976a;DANKS, 1981), but perhaps overlooked the importance of the diversity of microorganisms.
There is an important connection between the diversity of soil organisms and climate change (COLEMAN et al, 1992;DANKS, 1992;S0MME, 1993).An increase in temperature could have a pronounced effect on the carbon and nutrient cycles in alpine and arctic regions (CHAPÍN et al, 1992).It is believed that currently these regions act as carbon sinks, but they could become carbon sources through for example increased mineralisation rates (HEAL et al, 1998).The impacts on soil microbial activity could therefore be better predicted if the diversity of soil organisms and soil ecological processes in these extreme environments were better known.
Many studies of soil microbiology have been carried out in Austria including an early study by GAMS (1959).One of the most important sources of knowledge in this special field has been the above mentioned MAB projects, where most of the microbiological investigations were made by Schinner and co-workers.Their results on abandoned pastures and along altitudinal gradients were summarised by CERNUSCA (1978CERNUSCA ( , 1989)).In addition to taxonomic identification and quantification of soil microorganisms, the following have been characterised: processes of the carbon and the nitrogen cycles (REHDER & SCHÀFER, 1978;HAUNOLD et al, 1980;BRUNNER & BLASER, 1989;HACKL et al, 1995) and decomposition rates (e.g.SCHINNER, 1982;GSTRAUNTHALER & SCHINNER, 1989;SCHINNER & GURSCHLER, 1989;SCHINNER et al, 1989).The investigated alpine soils had a relatively low number of fungi species, high cell counts of bacteria, actinomycetes and yeasts.From soil respiration measurements it has been concluded that soil microorganisms PIRINEOS 151-152 were adapted to low temperatures in the alpine zone.Decomposition has been reported to be most intensive after snow melt in early summer, whilst tends to be followed by a decrease in microbial activity during summer because of low soil moisture.The initial studies on soil respiration at abandoned alpine sites by CERNUSCA et al. (1978) have later been extended to include the relationship between soil respiration and secondary succession in the Italian Alps (INTEGRALP project, TAPPEINER & CERNUSCA, 1994).Mycorrhizae have also been studied in the Austrian MAB projects.Ericoid mycorrhiza in the dwarf shrub heath and the vesicular-arbuscular mycorrhiza of the grass and herbaceous species in grass heath communities have been shown to be important for plant nutrition with the ericoid infection intensity decreasing with altitude (HASELWANDTER & READ, 1980;HASELWANDTER, 1989).In. alpine areas mycorrhizal infection is of special importance for re-afforestation projects (ALLEN et al, 1987;GÔBL, 1994).Changing abiotic site factors and their influence on soil microorganisms along altitudinal gradients have also been considered (DUTZLER-FRANZ, 1981), however it has been difficult to demonstrate changes along an altitudinal gradient as they may easily be offset by microtopographic heterogeneity (SCHINNER, 1983;McCOY, 1990;RANGGER et al, 1994).
In Germany, there have only been few studies on the soil fauna in alpine soils (e.g.TOPP, 1975;BOLLER, 1986;GEMESI et al, 1995;SKAMBRACKS, 1996).Most of the soil ecological studies in the German Alps have been carried out in the Berchtesgaden National Park as part of a MAB project (HABER et al, 1990).Humification processes, in particular chemical characterisation of humic substances (BOCHTER & ZECH, 1985;KÔGEL, 1987;KÔGEL et al, 1988), have been of primary interest and investigations focused more on the products of soil ecological processes, including humus forms (BOCHTER, 1988), than on the soil organisms themselves.
There is a paucity of data on soil ecological processes in the southern part of the Alps and the Iberian Peninsula.There have been some recent ecological investigations on altitudinal gradients in Italy (e.g.DI CASTRI, 1973;BRANDMAYR et al, 1995) after earlier studies on soil fauna (e.g.VERHOEFF, 1932).SIMON et al (1994) have reported their work on soil organic matter in the Sierra Nevada, Spain.
The published recommendations for priority research on biodiversity apply particularly to soil ecology.Comparisons between the results of detailed taxonomic studies on soil organisms made in the late 19th and early 20th century and those of current research have shown a loss of species in several mountain regions (ALPNET, unpublished).However, this kind of comparison (regarding a-diversity) is fraught with uncertainties because of the large number of organisms involved and because there are still many undescribed species.Research has begun to focus on finding indicator soil organisms (HAWKSWORTH, 1992;FOISSNER, 1994) and keystone species (SCHULZE & MOONEY, 1993), but rarely in mountain areas.Important types of keystone species are earth movers which affect soil ecological processes by bioturbation.Decomposers and mycorrhizae are also important types of keystone species for nutrient cycling.Abiotic agents which cause physical disturbances such as cryoturbation, contribute to key proceses which have a bearing on the diversity of soil organisms.In the lowlands and in low mountain areas lumbricides are the most important indicator organisms (e.g.GLASSTETTER, 1991) and they also play an important role in high mountain ranges (e.g.POP, 1987;POP & VASU, 1995;SKAMBRACKS, 1996), with the exception of northern Europe with low temperature.
A right step would be to identify species ecotypes and functional groups (SINNIGE et al, 1992;ZVYAGINTSEV et al, 1992;SCHULZE & MOONEY, 1993) and to study below-ground food webs in mountain soils.It would also be desirable to understand the ability of species to invade after perturbation and how this affects the habitat.Redundancy aspects should also be taken into account (SCHULZE & MOONEY, 1993;EUROPEAN COMMUNITY, 1994).Until now, such studies in soil ecology have more or less been restricted to agro-ecosystems (e.g.ANDRÉN et al, 1995).There is a considerable scope for experimentation there.
With regard to mineralisation and humification, research should focus on meso-and microhabitats of microorganisms in soil organic matter.Also, this would help to provide recommendations on how to protect humus on mountain slopes, particularly where there is intensive erosion.Another issue is the rhizosphere, where the role of mycorrhizae in alpine and arctic areas should be more intensively investigated.
Soil type, including humus form, is an important tool to characterise habitats.The influence of abiotic site factors such as texture and pH, on soil organisms and their activity has been widely studied.However, the role of soil organisms in pedogenesis is often neglected today, but had previously been studied by KUBIENA (1943) and KÜHNELT (1944).They have shown the impact of lumbricides on the genesis of mull rendzina soils (see MARTINUCCI & SALA, 1979).Some related studies have also been conducted in alpine areas by FREI (1944), ZÔTTL (1965), GILOT & DOMMERGUES (1967), GRACANIN (1970) andSZABÓ (1974).The description of the humus form to characterise habitats for soil organisms is very useful because the humus form is the result of the activity of organisms.Such work has to date been made in forest soils, the results of which only apply to a limited extent to subalpine and alpine situations (F.EDNORZ et al, unpublished).In mountain regions, natural and managed grasslands cover large areas (CERNUSCA, 1991) and an improved classification of grassland humus forms would help classify habitats for soil organisms (BROLL & BRAUCKMANN, 1994).
In line with general recommendations for biodiversity research, the monitoring of permanent plots could be combined with using existing longterm sites such as those of ITEX.Applied studies on the impact of recreation and tourism in mountain areas (e.g.MOSER et al, 1987;JANETSCHEK et al, 1987;MEYER, 1993;TROCKNER & KOPESZKI, 1994) should have a soil ecological component in the future.Current soil ecological research uses many new methods, e.g.mesocosm studies and molecular biological