CHAPTER 6
Spatio-temporal structure in soil
communities and ecosystem
processes
Matty P. Berg
6.1 Introduction
For some time ecologists have been interested in the
relationship between the structure of communities
and the consequences this has for the rate of ecosys-
tem processes, i.e. the structure–function debate
(Vanni 2002; Ha ̈ttenschwileret al. 2005), and the
role of community architecture as a stabilizing
mechanism of communities (McCannet al. 2005).
A wealth of evidence exists that links the dynamics
of populations to rates of ecosystem processes
(Jones and Lawton 1995; Wardle 2002 and examples
therein). The role of invertebrates often relates to
their differential utilization of resources or scarce
elements in the habitat, which can result in inter-
specific functional dissimilarity (Heemsbergenet al.
2004): the more different species are in the functions
they fulfil in ecosystems, the more important they
become. However, the enormous diversity in or-
ganisms in many communities makes the evalua-
tion of their role in ecosystems a Herculean task. To
reduce this diversity into smaller components a
food web approach has been adopted. In this way
the impact of community structure on ecosystem
processes and stability and visa versa can be ana-
lysed (DeAngelis 1992).
Although community structure has been shown
to be of great importance in regulating ecosystem
processes, the question remains how important
spatio-temporal variability in community structure
is for the regulation of processes, and if we need
this kind of detail to understand underlying
mechanisms (Berg and Bengtsson 2007). In an
attempt to answer this question I will use a terres-
trial example, the organic horizon of a coniferous
forest soil, (1) to quantify community variability
in time and across space and (2) to assess possible
consequences of community variability for an
important soil process, the degradation of organic
matter and the subsequent flow of energy and
nutrients through soil. First, I will briefly introduce
soil communities, how feeding links between species
in the community can be visualized in connec-
tedness food webs, and how organic matter is
structuring these food webs. Second, I will show
that soil communities are highly variable in time
and across space, much more variable than currently
is appreciated in many empirical and theoretical
community and food web studies, and elucidate
the importance of including community variability
in our studies to improve our mechanistic under-
standing of how soil organisms regulate soil process-
es. Finally, in order to understand the mechanisms
behind the interplay between community structure
and soil organic matter quality, I will present a con-
ceptual scheme in which the impact of vertical strat-
ification of soil communities on degradation is
further elucidated.6.2 Soil communities, detrital food webs and soil processes
Soil ecologists have long been fascinated by the
enormous diversity of life in soil. There is a69