Basic HTML Version
Molecular Soil Biology (online), 2013, Vol. 4 No.2, 7-15
ISSN 1925-2005
http://msb.sophiapublisher.com
9
2 Material and Methods
2.1 Study site
This research was conducted in experimental forest
station of Tarbiat Modares University located in a
temperate forest of Mazandaran province in the north
of Iran, between 36˚31َ 56˝N and 36˚32َ11˝N latitudes
and 51˚47َ 49˝E and 51˚47َ 56˝E longitudes. The
maximum elevation is 1700 m and the minimum is
100 m. Minimum temperature in December (6.6˚C)
and the highest temperature in June (25˚C) are
recorded, respectively. Mean annual precipitation of
the study area were from 280.4 to 37.4 mm at the
Noushahr city metrological station, which is 10Km far
from the study area. For performing this research, a
limited area of reserve parcel (relatively undisturbed)
considered that was covered by
Fagus orientalis
and
Carpinus betulus
dominant stands. This limitation had
an inclination 60~70 percent with northeast exposure
at 546~648 m a.s.l. Bedrock is limestone-dolomite
with silty-clay-loam soil texture. Presence of logged
and bare roots of trees is indicating rooting restrictions
and soil heavy texture (Kooch et al., 2010).
2.2 Soil sampling and analysis
Due to, twenty hectare areas of experimental forest
station of Tarbiat Modares University studied and
numbers of thirty four uprooted trees were found. In
the all of areas, the pit and mounds resulted from the
fall of a single tree. Pits needed to be at least 0.3 m
above the general soil surface and mounds 0.3 below
(Scharenbroch and Bockheim, 2007). For this purpose,
Five microsites were distinguished including mound
top, mound wall, pit bottom, pit wall and closed
canopy. Soil samples were taken at 0~15 cm, 15~30
cm and 30~45 cm depths from all microsites using
core soil sampler with 81 cm
2
cross section (Rahmani
and Zare Maivan, 2004). Large live plant material
(root and shoots) and pebbles in each sample were
separated by hand and discarded. The air-dried soil
samples were sieved (aggragates were crushed to pass
through a 2 mm sieve) to remove roots prior to
chemical analysis. Soil pH (with an electrode), water
content (by drying soil samples at 105
℃
for 24
hours), organic carbon (Walkey and Black method),
total nitrogen (Kjeldahl method) measured in the
laboratory (Jafari Haghighi, 2003).
2.3 Earthworm's samping and identification
The earthworms were collected simultaneously with
the soil sampling by hand sorting, washed in water
and weighed with mili gram precision. Species of
earthworms were identified (epigeic, anecic, and
endogeic) by external characteristics using the key of
BOUCH (Kooch and Hosseini, 2010). Epigeic worms
feed on plant litter, dwell on the soil surface or within
the litter layer, tend to be heavily pigmented, and are
small to medium sized. Anecic worms feed on plant
litter and soil, live in nearly vertical permanent
burrows, are dorsally pigmented, and large. Endogeic
species are soil-feeders, are not heavily pigmented,
from extensive horizontal burrow systems, and range
in size form small to large. Earthworm species do not
always fall clearly into these three main categories and
may even exhibit traits of different groups at different
life stages or under different environmental conditions
(Kooch and Jalilvand, 2008). Biomass was defined as
the weight of the worms after drying for 48 hours on
filter paper at room temperature (60˚C) ( Kooch and
Hosseini, 2010).
2.4 Statistical analysis
Normality of the variables was checked by
Kolmogrov-Smirnov test and Levene test was used to
examine the equality of the variances. Differences
between pit and mound microsites and depths in soil
characteristics were tested with two-way analysis
(ANOVA) using the General Linear Model (GLM)
procedure, with microsites (mound top, mound wall,
pit bottom, pit wall and closed canopy) and depths
(0~15 cm, 15~30 cm and 30~45 cm) as independent
factor. Interactions between independent factors were
tested also. Duncan test was used to separate the
averages of the dependent variables which were
significantly affected by treatment. Significant
differences among treatment averages for different
parameters were tested at P≤ 0.05. Nonparametric
Kruskal-Wallis analysis of variance was used to find
differences in earthworm's density and biomass of
microsites, beacsuse in some cases there was no
homogeneity of variance. Analyses of whole data were
done in SPSS Ver. 11.5 of statistical program. Factor
analysis is statistic technique for achievement to
complex relationships among variables. For this