Agriculture Reference
In-Depth Information
on community composition of total bacteria or responsive phyla, redun-
dancy analysis (RDA) was performed using the R add-on package 'vegan'.
A forward selection of soil parameters was applied to avoid using collin-
ear soil parameters in the same constrained ordination model. Only those
parameters contributing signifi cantly (p<0.05 via 1000 times permutation
tests) to community variation were added to the model.
5.3 RESULTS
5.3.1 SIGNIFICANT EFFECTS OF LAND USE ON THE
BACTERIAL COMMUNITY COMPOSITION REVEALED BY
DGGE FINGERPRINTS
To compare the bacterial community in soils under different land use, 16S
rRNA gene fragments of bacteria,
Alphaproteobacteria, Betaproteobac-
teria
and
Actinobacteria
PCR-products amplified from total community
DNA of alfalfa or adjacent scrubland soils sampled at two sites were ana-
lyzed by DGGE (Figures S1, S2, S3, S4).
Pairwise Pearson correlation indices were subjected to permutation
tests to determine the signifi cance of the land use effects on the bacte-
rial community structure. A signifi cant effect of land use was found for
bacteria and all bacterial groups analyzed for both sites (Table 2). The
extent of the infl uence was dependent on the phylogenetic group analyzed
(Table 2). The strongest infl uence of land use was found for the
Betapro-
teobacteria,
especially at site 1 (Table 2). In the community profi le for
Betaproteobacteria
, a strong band was observed only in all replicates in
soils with alfalfa from site 1 (Figure S4). For
Alphaproteobacteria,
the
dissimilarities of bacterial community fi ngerprints of soil under different
land use were comparable between both sites. The lowest yet still signifi -
cant effect of land use was observed for
Actinobacteria
(Table 2). Signifi -
cant differences in community composition between the two study sites
were found mainly for alfalfa growing soils as opposed to scrubland soils
(Table 2). Compared to the effects of land use, the infl uence of different
sites on community composition was smaller except for
Betaproteobacte-
ria
(Table 2), probably still due to the strong bands for alfalfa soils from
