Environmental Engineering Reference
In-Depth Information
−
si
Mandakini
lp
ps
ph
Bhagirathi
ca
cr
lm
ep
bl
sp
ba
pr
Pindar
Axis 1
go
Ramgang
a
hp
gl
co
Alkanada
rh
lep
py
sa
dr
el
hm
ag
br
hy
lpc
po
dx
ly
pl
−1.5
1.5
Fig. 4.8
PCA identifi ed the characteristic taxa in each basin of Himalayan region. The rest of the acronyms are similar
to Fig.
4.5
drainage basin occupies the same biome.
However, pine forest exists in the other basins too
(Pindar, Mandakini and Bhagirathi), but the char-
acteristic taxa are different, probably due to dif-
ferences in the water characteristics, thus
emphasising the role of proximate factors.
macroinvertebrate community in the river basins
of Uttarakhand. The taxa Philopotamidae,
Limnephilidae, Leptoceridae, Baetidae,
Perlodidae and Leptophlebiidae are associated
with the slope, while Ephemerellidae and
Coleoptera are associated with the forest type
(Fig.
4.9
). The taxa associated with the slope are
mainly families of Trichoptera. Ephemerellidae
is related to the pine forest, while Coleoptera to
oak-deodar-fi r forest.
Slope is observed to be an important environ-
mental variable infl uencing taxonomic composi-
tion and distribution of caddisfl y with case
(Limnephilidae, Leptoceridae, Philopotamidae)
along with mayfl y (Leptophlebiidae, Baetidae)
and stonefl y (Perlodidae). As slope is a manifes-
tation of altitude, it indirectly indicates the role of
altitude and hence the forest. Land use is an
important factor as it indicates stress due to
human activity. The macroinvertebrate fauna dif-
fered signifi cantly among the rivers within biome
due to different land use (Corkum
1991
; Rundle
et al.
1993
; Ormerod et al.
1994
). The assem-
blages of benthic macroinvertebrate taxa are
affected by current velocity, water conductivity
and substrate size (Miserendino
2001
), pH and
hardness (Ormerod and Edwards
1987
).
Role of Environmental Variables
Based on the above discussion, it is apparent that
the stations/streams/basins are similar in taxo-
nomic composition despite the latitudinal, forest-
type and land-use-type variations within the
mountain biome. Among the array of variables,
slope, forest type, stream order and land use,
slope (
p
0.524,
F 0.77) emerge as the main environmental factors
that cause 66.67 % and 33.33 % variation in the
taxonomic composition, respectively. On remov-
ing stream order from the analysis, similar results
are obtained. But on removing both (stream order
and slope) from the analysis, land use (
p
≤
0.042, F 2.2) and forest type (
p
≤
0.652,
F 0.7) emerged as the main environmental factor
causing 100 % variation in the taxonomic com-
position. These environmental variables are
hence important to distribution of the benthic
≤
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