Bio-physical features

This zone is characterised by mountaneous tracts of varying altitudes, steep slopes etc. Steeper slopes receive higher intensity of radiation and are not conducive to the growth of vegetation. Conversely, vegetation abounds on the relatively gentler slopes. Moisture from snow-melt and rich organic matter generate dense vegetation of fruit and forest trees. Most of this zone consists of granite and other crystalline rocks of unforseliferous sediments.

An average rainfall of about 100 cm received during the monsoon months and its erratic distribution further necessitate suitable watershed management interventions.

A calendar year is generally divided into three main seasons viz. winter (October-February), summer (March-June) and monsoon (July-September) with a brief spring (mid February-March) and autumn (late September-October). Winter temperatures generally remain below 5°C and precipitation in the form of both rainfall and snow result from the western depression. The cold wave sets the migration of the nomadic shepherds to warmer valleys in the Himalayan foothills.

Summer temperatures remain above 20°C especially during April-June. The relative humidity remains about 40 per cent and the occasional hailstorms are known to cause extensive crop damage especially to apple, plum, apricot and peach. Rainfall during this period amounts to approximately 30 per cent of total annual rainfall.

Monsoon results from the South-west monsoon and about 50 per cent of total annual precipitation is received during this period. The temperatures are known to drop by 2-4°C and the relative humidity reaches 60 per cent. In addition to precipitation the "directional aspect" is crucial for development of vegetation. The Northern aspect receiving less direct sun-shine and facing the snowline has consequently, lower temperatures and high moisture retention which inturn create ideal agro-climatic conditions for the cultivation of temperate crops, especially fruit crops. The southern and western aspects suffer high moisture loss since they receive more direct sunshine and consequently they support a poor vegetation cover. The difference in temperature on the different aspects of hills can also be explained in terms of differential isolation i.e. by proximity or distance from the equator, for example isolation factor for the southern aspect is about 1.5-2.4 times higher than that for the northern aspect.