Basic HTML Version
Molecular Soil Biology (online), 2013, Vol. 4 No.2, 7-15
ISSN 1925-2005
http://msb.sophiapublisher.com
10
purpose, relationships between microsites, earthworm's
assemblage and soil parameters were analysed by
Principle Component Analysis (Mc Cune and Mefford,
1999).
3 Results
3.1 Soil characters
The greatest value of water content resulted in pit
bottom and beneath layers of soil and the least was
detected in mound top and 0-15cm depth.
Significantly statistical differences (
P
< 0.01) were
considered for this character (Table 1). Soil pH was
significantly (
P
< 0.01) higher in mound wall and top.
Fewer amounts were found in pit bottom (Table 1).
Organic matter and carbon significantly (
P
< 0.01)
increased in pit bottom whereas the least was observed
in mound wall. These characters were decreased with
increasing of soil depth (Table 1). Compare mean of
total nitrogen in the microsites and depths indicated
that pit bottom and 0-15cm depth had the higher
amounts (
P
< 0.01) than in the others. Mound wall
and 30-45cm depth includes the least value (Table 1).
Greater amounts of carbon to nitrogen ratio were
found in mound wall and 30-45cm depth whereas pit
bottom had lower values, significantly (
P
< 0.01)
(Table 1).
3.2 Ecological groups of earthworms
Analysis of data showed that abundance of
earthworm's ecological groups had significant
differences among microsites and soil depths (Table 2).
Earthworm's (epigeic, anecic and endogeic) density
and biomass had more amounts in pit bottom whereas,
no earthworms found in mound top and wall
microsites (Table 2). Studying of soil depths
indicating that epigeic gathered in 0~15 cm depth,
anecic preferred 15~30 cm and endogeic were
assemblaged in soil deeper layers (Table 2).
3.3 Principal component analysis (PCA)
Principle component analysis showed that percentages
of eigenvalue for the first and second axis are about
90.691% and 8.71%, respectively. These two axes are
indicating 99.41% of total variance (Table 3).
Eigenvectors of soil characters for these axes
presented in table 4. PCA bibplots of microsites, soil
characters and earthworm showed in figure 1. As can
be seen in this figure, the mound top and wall have
different condition in comparison to the others. These
microsites involve quarter 3 of principal components.
Whereas, pit bottom and wall presented different
position than in closed canopy and captured quarters 4
and 1, respectively. Closed canopy was located in
quarter 2 of axis. Earthworm's assemblage in quarter 4
of principal components is indicating more
appropriate condition of soil ecosystem in pit bottom
microsite.
4 Discussion
This research has confirmed the significant effect of
different microsites and soil depths on earthworm
abundance and biomass. Earthworms are sensitive to
acid condition and theirs abundance are decreased
with reducing of soil pH (Tondoh et al., 2011).
According to previous studies, earthworms are
interested in buffer condition of soil pH (Neirynck et
al., 2000; Kooch and Jalilvand, 2008; Kooch et al.,
2009; Kooch and Hosseini, 2010). The result of
Deleporte (2001) research pointed that soil pH is an
effective agent on earthworm's population. In current
study, the pit microsites presented lower pH in
comparison to the other microsites. Whereas, higher
densities of earthworms were found in these
microsites, also. Although, soil pH was less acid on
mound microsite, but earthworms population were
assemblaged in pit microsites. As can be seen in table
1, pit bottom includes more amounts of soil water
content. Water constitutes 80 to 90% of the body
weight of earthworms (Kooch and Hosseini, 2010), so
soil moisture are essential for theirs live and will kill
by reason of soil drying (Kooch and Hosseini, 2010;
Na et al., 2011; Snyder et al., 2011; Scharenbroch and
Johnston, 2011). Regarding to water content of 58.52 %
in pit bottom, this amount is due to more assembelage
of earthworm's different groups. Mounds creats hilly
surfaces on superficial soil and include more soil
volume and temperature in compare to other surfaces
(Londo, 2001; Kooch et al., 2008). On the other hand,
soil temperature is effcetive on density and biomass of
earthworms and distribution (Kooch et al., 2008).
Therefore, low moisture and high temperature created
fatal conditions for earthworms on mound microsite
(Nachtergale et al., 2002). By this reason, no