MATERIALS & METHODS
Two soils under different management practices
were chosen for incubation i.e. grassland and arable
from Beijing Forestry University area (40°002 252
N, 116°202 40"E) in Beijing, China.
Thus, Beijing has a rather dry, monsooninfluenced
humid continental climate (Köppen
climate classification ), characterized by hot, humid
summers due to the East Asian monsoon, and
generally cold, windy, dry winters that reflect the
influence of the vast Siberian anticyclone. Spring can
bear witness to sandstorms blowing in from the Gobi
Desert across Mongolian steppe, accompanied by
rapidly warming, but generally dry, conditions.
Autumn, like spring, sees little rain, but is crisp and
short (Zhao, 2011). Fig.1 showsthat the monthly daily
average temperature in January is -3.7 °C (25.3 °F),
while in July it is 26.2 °C (79.2 °F) .
Precipitation averages around 570 mm (22.4 in)
annually, with close to three-fourths of that total
falling from June toAugust (Fig.1). Table1 showsthat
with monthly percent possible sunshine ranging from
47% in July to 65% in January and February, the city
receives 2.671 hours of bright sunshine annually.
Extremes have ranged from -27.4 °C (-17 °F) on 22
February 1966 to 42.6 °C (109 °F) on 15 June 1942
falling from June to August (Table1). With monthly
percent possible sunshine ranging from 47% in July
to 65% in January and February, the city receives
2.671 hours of bright sunshine annually (Table1).
Extremes have ranged from -27.4 °C (-17 °F) on 22February 1966 to 42.6 °C (109 °F) on 15 June 1942
as reported by China meteorological administration.
Soil samples were taken from a depth of 0-15 cm by
removing upper vegetation and then were well
homogenized to ensure homogeneity. Soils sample
was from different peripheral area of Beijing. After
sampling, soils was immediately transported to the
laboratory and sieved to 4 mm sieve as reported by
Thomson et al., (2010). Soil samples of 130 g soil
were packed into columns (100 cm3
) resulting in a
bulk density of
. 1.3g/cm. Then, the soils were
artificially saturated and adjusted to pF 1.8 i.e. 32%
gravimetric water content (
wt
) by weight through
pressure plates (Loveday, 1974). After pF adjustment,
soil cores were placed into microcosms (0.85 l) and
sealed with plastic lids containing rubber septa. In
total, 80 microcosms were prepared. The microcosms
were then transferred to a climate chamber, set at a
constant temperature of 20°C in darkness about sixty
days.