Global Litter Invertebrate
Decomposition Experiment
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.
JUSTIFICATION
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.
OBJECTIVES
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.
FUNDING
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.
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.
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