Pandit Govind Ballabh Pant Memorial Lecture: II

- Transition from cold desertic conditions in western sector in Ladakh, to cool and
moist conditions prevailing in Arunachal Pradesh in the eastern sector.
- Transition from near tropical/ subtropical conditions in south side of Himalaya
adjoining Indus-Gangetic Plains, to the cold dry Tibetan plateau in the north;
and
- Transition along the vertical gradient from tropical/subtropical conditions at the
lower altitudes, to alpine vegetation to arctic conditions at the high altitudes.
Thus, there are three major factors operating simultaneously. These are longitude
(west to east), latitude (south and north) and altitude (lower to higher). There is a
parallelism in vegetational types on account of latitude and altitude. What grows at
higher altitudes at lower latitudes, often grows at lower altitudes at higher latitudes.
This brings in a degree of complexity in distibutional pattern due to latitude, longitude
and altitude of a particular place in the Himalaya, and creates many microclimatic
situations.
There is a considerable gap in our knowledge about not only biotic wealth per se
but also its distribution and composition of communities and ecosystems. In general
bioproductivity per unit area per unit of time is lower in Himalaya (except in the
eastern sector). Individual species occupy wide ranges, and population gets broken
into smaller isolated units. It is for this reason that there is a higher rate of
endemism.
Another dimension is that Himalayan biota is under five different biogeographic
influences. These are Palaeoarctic, Mediterranean, Sino-Japanese, Indo- Malayan
and Peninsular Indian (Fig. 4). Even so, there is considerable endemicity.
As discussed above, there is parallelism between altitudinal and latitudinal
distribution of taxa. Looking at Himalaya from this point of view (i.e. distributional
pattern, from West to East, and South to North), there are four situations (see also
MacKinnon and MacKinnon, 1986):
- North-West Himalaya: These are located primarily in Kashmir, Himachal
Pradesh and parts of Western Uttar Pradesh. Here East European and
Mediterranean influence is discernible in conifers, several herbaceous elements
and animals like Ibex. Palaeoarctic influence is seen in Hippophae and Tibetan
Ass.
Fig. 4- Influence of adjoining Biogeographic Realms on biodiversity in India:
Mackinnon and Mackinnon 1986.
- Western Himalaya: These range from Sutlej Valley to Gandak in Nepal. There is
a mixture of western and eastern elements like deodar, rhododendron, red
panda, blood pheasant, etc.
- Central Himalaya: These occupy entire Nepal, Sikkim into hills of Western
Bengal to Bhutan. This is relatively moist area and there are some
Rhododendrons and tahr and brown bear indicating Indo-Chinese influence.
23