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hypothesis. Such studies have been initiated
recently in the Himalayan streams, which are of
global importance to biodiversity (Ormerod et al.
1994
; Suren
1994
; Rothfritz et al.
1997
; Cantonati
et al.
2001
; Nautiyal et al.
2004
). Biodiversity in
the Himalayan mountains is globally signifi cant
due to pronounced endemism, habitat heteroge-
neity and biogeographic location (Myers
1990
;
Myers et al.
2000
).
In the mountain streams of India, spatial scales
have been examined with respect to small patches
within a single stream (Badola and Singh
1981
;
Nautiyal
1984
,
1986
; Negi and Singh
1990
;
Gusain
1994
; Kishor et al.
1998
; Kishor et al.
2004
) or longitudinally (Singh and Nautiyal
1990
; Singh et al.
1994
; Gusain
1994
; Nautiyal
et al.
1996
,
1997a
; Julka et al.
1999
). The pat-
terns of distribution at larger scales are not known
in the Himalaya. Therefore, this study focused on
distribution patterns of benthic macroinvertebrate
community at the basin scale and longitudinally
for some streams in the Uttarakhand. Mountains
present an entirely different landscape as they
provide biome gradations analogous to latitude
differences. It remains to be seen if the structur-
ing force is retained in the biomes analogous to
forest type vis-a-vis subbasins or the effect of
altitude overrides it. The infl uence of land use has
also been assessed.
sampled at seasonal intervals from over 10
subbasin and 77 mountain streams of different
orders (3rd-5th).
Geology
The geology of the Himalaya is vast
and varied. The Himalayas' main axis is formed c.
25-70 Ma ago as the earth's crust folded against
the northward-moving Indian subcontinent
(Columbia Encyclopedia, 6th edition 2001.htm).
The Greater Himalaya (
Himadri
) lies above
the main central thrust; the Lesser Himalaya
(
Himanchal
) is separated from the
Himadri
by the
'main central thrust' in the north and by the 'main
boundary thrust' in the south, consisting of high
mountains cut into deep ravines and precipitous
defi les; and the Sub-Himalayan tract (
Sivalik
) -
the foothill belt of the region - consists of the latest
geological formation of loose boulders and soil.
The Greater Himalaya is composed of central
crystallines, generally granite and gneisses, quite
hard and resistant to weathering. The Lesser
Himalaya is mostly composed of crystalline and
metamorphic rocks - gneisses - and schists, with
unfossiliferous sedimentary Purana and Mesozoic
deposits (Valdiya
1962
).
Climate
In the Himalaya the topographical
variations do not straightaway correlate with the
latitudinal or continental trends. Also the
precipitation changes from rain to snow from the
Outer to Greater Himalaya. Therefore, many rivers
have glaciers at their source, which renders their
water cold. Spatial average rainfalls are 1,472 mm
for Terai/Bhabar, 1,782 mm for the Sivalik
ranges, 1,591 mm for the Lesser Himalayas and
1,635 mm for the Greater Himalayan region. The
mean aerial rainfall in the region is 1,608 mm
(Basistha et al.
2008
).
Study Area
Location
The study area extended from Yamuna
to Ramganga basin in the state of Uttarakhand
(Fig.
4.1
). The Lesser Himalayan stream basins
selected for study included Yamuna, Bhagirathi
(including Bhilangana), Alaknanda, Mandakini,
Pindar and Ramganga (Saryu-Gomti). The
latitude decreases from 30° N in the Yamuna
basin to 29° N to the Ramganga basin. Streams in
different land use and forest types are selected
(Table
4.1
), especially intensively cultivated
areas both in the hills and foothills and forested
areas [pure oak and pine forests, mixed forests].
The benthic macroinvertebrate community is
Vegetation
The Himalayan rivers fl ow through
a cross section of biomes. The vegetation of
Garhwal is usually divided into three main zones
(i) submontane zone (Sivalik 1,500 m), (ii)
montane zone (1,500-3,300 m) and (iii) alpine
zone (3,100-7,300 m) (Rawat et al.
2001
). There
is a considerable change in the vegetation from
alpine to submontane zone. The alpine is
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