BACKGROUND
In terrestrial ecosystems, biological diversity of soils is poorly known, but it is estimated to be greater than in above-ground systems (Wall and Virginia 2000). Soil biota, primarily at a functional group level, are known to regulate vital ecosystem processes such as decomposition (the modification of complex organic compounds into organic nutrients available for plant growth), carbon sequestration, and nutrient cycling (Brussaard et al. 1997, Bardgett and Chan 1999, Paustian et al. 2000). The rate of decomposition is dependent on the interaction of climate, biota and the quality and quantity of organic matter (Swift et al. 1979). Scientists can predict gross estimates of decomposition based on the climate and the C:N:lignin ratio of organic matter (litter), however, soil organisms play a mediating role. In particular, they may affect the type and availability of nutrients and thus community interactions. For example, Binkley et al. (1998) stated, “the black box of the soil community can strongly affect the supply of nutrients . . .a black box . . . clearly needs to be taken apart and examined in greater detail.” Evidence from the 1980’s on deserts (Whitford et al. 1982), and more recently from subalpine and wet and dry tropical ecosystems (González and Seastedt 2001) again indicates that soil fauna are key to litter decomposition rates.
One of the most important global ecosystem processes regulated by soil biota is the decay process or decomposition (the modification of complex organic compounds into inorganic nutrients available for plant growth). Decomposition is a critical ecosystem function that removes wastes, recycles nutrients, renews soil fertility and carbon sequestration (Wall and Virginia 2000).
Our understanding of the soil species involved in decomposition and whether the individual soil species have an effect on ecosystem processes is limited. For example, the relationship between the number of species of any soil group (e.g., mites, nematodes, millipedes) and an ecosystem process, such as the rate of decomposition, has not been established in field studies. Thus when soils are degraded, it is without knowledge of effects on their biological diversity and ecosystem services.
The SCOPE Committee on Soil and Sediment Biodiversity and Ecosystem Functioning (SSBEF) recently synthesized knowledge on below-ground species diversity and ecosystem functioning in a series of international workshops (Behan-Pelletier and Newton 1999, Brussaard et al. 1997, Hooper et al. 2000, Wolters et al. 2000). Their findings suggest that most steps in soil ecosystem processes are performed by groups of species from many phyla, resulting in high species redundancy (different species performing same ecosystem process).
However, some critical steps appear to be performed by a few “keystone” species (mostly larger invertebrates such as termites, earthworms, enchytraeids). This raises the question of whether disturbance may affect these soil “keystone” species and impact ecosystem processes, and whether other smaller invertebrates also have roles as keystone species or a high species redundancy.
One result from the recent SSBEF workshop revealed a scarcity of data on species identities and associations with those species and specific ecosystem processes. This lack of data undermines efforts to identify relationships between below-ground biodiversity and ecosystem functioning. For example, the SSBEF workshop participants were not aware of a single study, in any ecosystem, that had quantified how an ecosystem process was influenced by the composition and numbers of below-ground species. The GLIDE is an important step in initiating quantitative research on this relationship of below-ground biodiversity and critical ecosystem processes.
GLIDE collaborators will examine invertebrate species involved in decomposition of a litter source (senescent vegetation on the surface of the ground), which, as specified earlier, is a process critical to ecosystem function. Decomposition rates are dependent on the interaction(s) of climate, biota, and the quality and quantity of organic matter, but how important are soil biota to this process and other ecosystem processes? What about soil biota diversity and its importance in ecosystem functions? The GLIDE will provide initial research into these complicated and interesting questions while directing future research efforts. After data collection is complete, the GLIDE hopes to have addressed the following questions:
- At varying latitudes, what are the effects of excluding animals to the rate of litter decomposition?
- Are similar taxonomic groups involved in decomposition irrespective of biomes and latitude?
- Does the succession of taxa vary with latitude and decomposition rate?
- Are patterns of organism succession involved in decomposition the same across biomes and latitude even though the rate of succession varies?
We are hypothesizing that litter decay at sites with different suites of decomposing species will decay differently than could be predicted by abiotic factors (e.g., climate). To help answer these questions and test this hypothesis, we now have 33 experimental sites in 18 countries participating in the Global Litter Invertebrate Decomposition Experiment (for information on what is required of a site collaborator click here). These sites will fill gaps in our knowledge of decomposition and diversity for certain biomes and latitudes. Additionally, satellite sites will be encouraged to participate if cooperators help pay for taxonomic sorting. Click here for specific information on experimental design.
The National Science Foundation and the Soil Science Society of America have generously offered their support to GLIDE in the form of a $50,000 and $8,700 grant respectively. We cannot thank these organizations enough for their financial support for this groundbreaking experiment.
Core Sites: These sites have been selected from pre-established international networks and International Long Term Ecological Research (ILTER) cooperators. These sites will fill gaps in our knowledge of decomposition and diversity for certain biomes and latitude.
Satellite Sites: These cooperators have provided their own funding for litterbags, shipping, and taxonomic sorting.
| Country | Site name | Contact |
| Canada | Stavely | Dr. Dan Johnson |
| Canada | Onefour | Dr. Dan Johnson |
| China | Xishuangbanna Tropical Botanical Garden | Dr. Xiaoming Zou |
| United States | MacArthur Agro-ecology Research Center | Dr. Patrick Bohlen |
Behan-Pelletier, V. and G. Newton. 1999. Linking soil biodiversity and ecosystem function: the taxonomic dilemma. Bioscience 49:149-152.
Binkley, D. and G. Christian. 1998. Why do tree species affect soils? The warp and woof of tree-soil interactions. Biogeochemistry 42:89-106.
Brussaard, L., V.M. Behan-Pelletier, D.E. Bignell, V.K. Brown, W. Didden, P. Folgarait, C. Fragoso, D. Wall Freckman, V.V.S.R. Gupta, T. Hattori, D.L. Hawksworth, C. Klopatek, P. Lavelle, D.W. Malloch, J. Rusek, B. Soderstrom, J.M. Tiedje, and R.A. Virginia. 1997. Biodiversity and ecosystem functioning in soil. Ambio 26:563-570.
González, G., and T.R. Seastedt. 2001. Soil fauna and plant litter decomposition in tropical and subalpine forests. Ecology 82(4):955-964.
Hooper, D.U., D.E. Bignell, V.K. Brown, L. Brussaard, J.M. Dangerfield, D.H. Wall, D.A. Wardle, D.C. Coleman, K.E. Giller, P. Lavelle, W.H. van der Putten, P.C. de Ruiter, J. Rusek, W. Silver, J.M. Tiedje, and V. Wolters. 2000. Interactions between above- and belowground biodiversity in terrestrial ecosystems: Patterns, mechanisms, and feedbacks. BioScience 50:1049-1061.
Paustian, K., J. Six, E. T. Elliott, and H. W. Hunt. 2000. Management options for reducing CO2 emissions from agricultural soils. Biogeochemistry 48:147-163.
Swift, M.J., O.W. Heal, and J.M. Anderson. 1979. Decomposition in terrestrial ecosystems. University of California Press, Berkeley, CA.
Wall, D.H., and R.A. Virginia. 2000. The world beneath our feet: soil biodiversity and ecosystem functioning. Pages 225-241 in P.R. Raven and T. Williams, editors. Nature and human society: the quest for a sustainable world. National Academy of Sciences and National Research Council, Washington, DC.
Whitford, W.G., D.W. Freckman, P.F. Santos, N.Z. Elkins, and L.W. Parker. 1982. The role of nematodes in decomposition in desert ecosystems. Pages 98-116 in D. W. Freckman, editor. Nematodes in soil ecosystems. University of Texas Press, Austin, TX.
Wolters, V., W.L. Silver, D.E. Bignell, D.C. Coleman, P. Lavelle, W.H. van der Putten, P. de Ruiter, J. Rusek, D.H. Wall, D.A. Wardle, L. Brussaard, J.M. Dangerfield, V.K. Brown, K. Giller, D.U. Hooper, O. Sala, J. Tiedje, J.A. van Veen. 2000. Effects of global changes on above- and belowground biodiversity in terrestrial ecosystems: implications for ecosystem functioning. BioScience 50:1089-1098.
GLIDE was a project of the International Biodiversity Observation Year 2001-2002.
This material is based upon work supported in part by the National Science Foundation under Grant No. 98 06437 Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.