Soil ecology and agroecosystem studies - Microbial Ecology in Sustainable Agroecosystems - page 14

120

Colpodid
Stichotrich
Other Ciliate
Predatory
Amoebae
Flagellates
Testacea

100

80

60

40

20

0

Loft Smith Nugent Vickers Carter

0 0 4 8 25

Years in Conservation

Figure 1.6 The temporal dimensions of protozoan diversity in a southern Georgia chronosequence.
Note the increasing proportions of amoebae, flagellates, and testacea in the longer-term conserva-
tion tillage fields. (From Adl, M.S., D.C. Coleman, and F. Reed. 2006. Slow recovery of biodiversity
in sandy loam soils of Georgia after 25 years of no-tillage management. Agriculture, Ecosystems and
Environment 114:323-334. With permission from Elsevier.)

Normal
successional
trajectory

Late grassland

Restoration
shortcut

Pioneer/
immature
system

Scrub

Forest

Raw substrate/degraded site

Figure 1.7 As ecosystems mature, there is a switch in dominance from bacterial to fungal biomass;
total microbial biomass in bulk (nonrhizosphere) soil peaks around midsuccession because this
is the period of root exudates in this phase peak. As fungal symbionts begin to dominate the rhi-
zosphere, fewer plant exudates diffuse into the soil bulk phase. The aim of restoration to mature
forest systems is to short-cut this trajectory by means of establishing fungal dominance at an early
stage. (From Harris, J. 2009. Soil microbial communities and restoration ecology: facilitators or fol-
lowers? Science 325:573-574. With permission from the American Association for the Advancement
of Science.)