The Soil Biota
Organisms
- There are
astonishing numbers of living organisms in most soils (as
many as two billion per cubic inch). Humus-rich soils
usually contain complex networks of fungal threads called
hyphae. Some soil fungal hyphae form mutualistic symbioses
with plant roots - the fungal threads are called
mycorrhizae - and the fungi are able to gather moisture and
nutrients for utilization by plants. Soils contain
autotrophic and heterotrophic bacteria, fungi, and an array
of earthworms, nematodes, arthropods, snails and insects.
The soil flora and fauna are continuously recycling
nutrients in the soil released from the minerals, added
plant material, added water, and previous generations of
the organisms. Soil invertebrates can be isolated using
Berlese-Tulghren funnel techniques.
We can compare similarities in two communities at a time by
computing a similarity index: Our method of comparison will
be the simple Jaccard coefficient of community. This
coefficient is the number of species found in both
communities being compared divided by the number of species
in community 1 plus the number of species in community 2
minus the number of species common to both communities.
CCJ
= c / s1
+
s2
- c
where c = number of species found in both communities,
s1 = number of species found in
community 1, and
s2 = number of species found in
community 2, and
CCJ = Jaccard's coefficient.
Jaccard's coefficient will range in value from 0 to 1, and
the closer it is to 1 the more similar the communities are.