Community composition of soil organisms under different wheat-farming systems - Microbial Ecology in Sustainable Agroecosystems - page 98

or ecosystem functions, see the work of Birkhofer, Bezemer, et al. (2008). FA profiles dif-
fered significantly between farming systems if based on the concentration of individual
FAs in the soil ( Figure 5.2a ; ANOSIM, R = 0.454; P < 0.001). The profiles differed signifi-
cantly between CONMIN and BIODYN, CONMIN and BIOORG, and CONMIN and
CONFYM. The FA that contributed most to these differences was 18:1ω7 as the concentra-
tion of this biomarker FA for gram-negative bacteria was always lower in the CONMIN
system ( Figure 5.3a ) . A biomarker NLFA for AMF (16:1ω5) had lower concentrations in
CONMIN soils compared to the other systems ( Figure 5.3b ) . FA profiles still differed sig-
nificantly between farming systems if individual FAs were pooled into biomarker groups
( Figure 5.3c ; R = 0.358; P = 0.003). At this organizational level, pairwise comparisons only
detected significant differences between CONMIN and BIODYN ( R = 0.667; P = 0.029) and
CONMIN and BIOORG ( R = 0.802; P = 0.029). The major subset of FAs responsible for this
difference was the biomarkers for gram-negative bacteria, which had higher concentra-
tions in the two organically managed systems.
The community composition of nematodes differed significantly between farming
systems at the genus level ( Figure 5.2b ; R = 0.738; P < 0.001), with significant differences
(a) Fatty acids
BIODYN
BIOORG
CONFYM
CONMIN
(b) Nematoda
Figure 5.2 Two-dimensional NMDS ordination of (a) profiles based on concentrations of 17 fatty
acids (2-D [two-dimensional] stress = 0.084) and (b) nematode genus composition (2-D stress = 0.185)
in 16 plots of four different farming systems (see Table 5.1 ) .