Agriculture Reference
In-Depth Information
Alphaproteobacteria
(
Rhizobiales: Rhizobiaceae, Phyllobacteriaceae;
Sphingomonadales; Rhodobacterales)
,
Betaproteobacteria
(
Burkhold-
eriales; Comamonadaceae
) and
Gammaproteobacteria
(
Alteromonad-
ales; Pseudomonadales: Pseudomonadaceae
) contained a high propor-
tion of OTUs (>18%) that were more abundant in alfalfa soils (Table
3). An exception for
Gammaproteobacteria
was the order of
Legio-
nellales,
of which ca. 56% of the OTUs were more abundant in the
scrubland soils (Table 3). Interestingly, for
Rhodobacterales
(
Alphap-
roteobacteria
) 40% of the OTUs were more abundant in alfalfa soils,
while 20% of the OTUs were lower compared to scrubland soils (Table
3). A high proportion (>33%) of the OTUs belonging to two orders
of
Actinobacteria
(
Acidimicrobiales
and
Rubrobacterale
s) had lower
relative abundance in natural scrublands compared to alfalfa soils.
Several families in the order of
Actinomycetales
(
Microbacteriaceae,
Micromonosporaceae, Micrococcaceae,
and
Cellulomonadaceae
) had
more OTUs with signifi cantly higher abundance in alfalfa soils than in
the scrubland soils (Table 3). In contrast to these families,
Mycobacte-
riaceae
and
Pseudonocardiaceae
decreased in relative abundance with
change in land use (Table 3).
A modifi ed test based on the fi rst fi ve principal components [38] was
applied to study the effect of land use on bacterial community composi-
tion of the taxonomic groups listed in Table 3. It revealed and confi rmed
dramatic differences in the abundance of specifi c bacterial community
members in response to land use. All the taxonomic groups listed in
Table 3 had signifi cantly different community compositions, except for
Nocardiaceae
(p = 0.07) (Table 3). As already observed with the DGGE
analyses, the variation in the bacterial community composition was
higher in the soils from scrubland than from alfalfa fi elds (Figure S5).
Compared to the land use, the two different locations had less infl uence
on the community composition. Effects of the site were only detected for
a few taxonomic groups such as the
Sphingomonadales, Rhodobactera-
les, Rubrobacterales
and
Actinomycetales
. These orders, however, were
signifi cantly different in their community composition between the two
sites (Table 3).
