In April of 2009, saline soil sampl

In April of 2009, saline soil samples were collected from the
Yellow River Delta near Dongying. Precise locations are shown in Table 1. The mean annual precipitation in this area is 552 mmwith
70% occurring between June and September. The average annual
temperature is 12.1 C. Soil samples were collected from four sites
along a salinity gradient: slightly saline (Site 1, ECe ¼ 3.2 mS cm1),
moderately saline (Site 2, ECe ¼ 7.1 mS cm1) and extremely saline
(Site 3 and 4 with ECe ¼ 50.7 and 112.6 mS cm1, respectively). Soils
of the four sites are all formed by sediment deposition of the Yellow
River and classified as Calcaric Fluvisols (FAO classification). Site 1
was formed around 1976 and planted with Robinia pseudoacacia
L. in 1989. Site 1 is a forest ecosystem dominated by R. pseudoacacia
L. with a dense cover of grass. Site 2, formed around 1992, is
a grassland ecosystem dominated by the salt-tolerant Imperata
cylindrical (L.) Beauv. Site 3, also formed around 1976, is dominated
by the highly salt-tolerant shrub Tamarix chinensis Lour. Site 4 is
bare soil for the most area, with the sporadical distribution of
Suaeda glauca Bge.
In each site, three locations were randomly selected. In each
location, 3-4 soil cores were collected using PVC pipes (7.0 cm
inner diameter and 12 cm length). The cores in PVC pipes were
placed into jars (1850 mL) for future incubation and gas
measurement. The PVC tubes and jars were weighed before the
sampling. Two smaller soil cores (5.0 cm diameter), close to the
intact soil core for incubation, were also taken in 4 cm depth
increments down to 20 cm (0e4, 4e8, 8e12, 12e20 cm). The small
cores were placed in a plastic bag, homogenized in the lab and
stored at 4 C.

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