Agriculture Reference
In-Depth Information
formed at different taxonomic levels,
Bacteria, Actinobacteria, Alpha-
and
Betaproteobacteria
in order to analyze not only dominant bacteria. The
so-called PhyloChip developed by Brodie et al. [36] offers the potential to
detect 8741 operational taxonomic units (OTUs) and the dataset is ideal
for identifying taxa containing a high proportion of OTUs with treatment
dependent signifi cantly increased or decreased abundance. Therefore, the
PhyloChip dataset was used to analyze whether, and if so which bacterial
taxa responded to agricultural use, and multivariate statistics was applied
to explore the relationship between discriminative soil parameters and re-
sponsive taxonomic groups.
5.2 MATERIALS AND METHODS
5.2.1 SITE AND SAMPLING
Two typical sites in the Santo Domingo valley, Baja California, Mexico
(site 1: N25°06′31.5″ W111°32′34.3″, altitude 70; site 2: N25°16′5.2″
W111° 36′ 02.5″, altitude 90; the distance between site 1 and site 2 is ca
50 km; No specific permits were required for the described field studies.
The location is not protected in any way. The field studies did not involve
endangered or protected species.) were selected. Soil samples were taken
on 30 April 2007 from two covers, i.e., a field planted with alfalfa (
Medi-
cago sativa
) and the adjacent natural scrubland. Four replicates per site
and cover were taken respectively from plots (1 m×1 m squares) that were
at least 20 m apart from each other. After removing the top 1-2 cm soil
layer, the soil from 2-15 cm depth was mixed with a shovel and approx.
2 kg of soil was sampled, put into plastic bags and transferred to the labo-
ratory. Within 24 h after sampling, the soils were sieved through a 2 mm
mesh and aliquots were used for microbiological and chemical analysis.
5.2.2 SOIL PROPERTIES
All soils were analyzed by the certified laboratory at CIBNOR (La Paz,
Mexico). Briefly, soil particle size determinations were conducted with the
