explain with reference relief relief and rainfall why they are evergreen forests in the Western Ghats and desert vegetation in the shower and coach in Gujarat
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Because the length and severity of the 'dry season' in these regions is offset by the length of, or intensity of rainfall in, the 'wet season'.
Water that has seeped into the soil and thereby into the water table, and into water bodies such as rivers, lakes, etc., tends to remain plentiful for a considerable amount of time following the end of a rainy spell. Deciduous trees thrive better than evergreen trees in regions where the dry season is long enough to severely deplete the water table and moisture available to the trees; if the dry season is not long enough, the deciduous flora can get quickly outcompeted by evergreen flora.
As far as the Western Ghats are concerned, they get an extraordinary amount of orographic precipitation during the south-west monsoon, an amount significant enough to keep the water table replenished during the dry season from ~ November to ~May. The stable high-pressure systems over the Arabian Sea and the influx of hot dry air from the desert regions of Balochistan, Iran and Arabia inhibit pre-monsoonal activity, but inspite of this the forests manage to stick around owing to extraordinary monsoonal precipitation. Perhaps more quantitatively, this can be expressed in the difference between a Tropical monsoon climate and a Tropical savanna climate.
The North-Eastern states get a significant amount of precipitation (amounting to upto a third of the total yearly precipitation in some areas) during the pre-monsoon months of March-May. This pattern is not linked to the monsoon, and is largely driven by local convective thunderstorms (sometimes isolated, sometimes in clusters) formed from diurnal heating in the adjoining Eastern India and the influx of moisture-laden wind from the Bay of Bengal. Other rain-causing factors include lows in the Bay of Bengal and, most noticeably in the winter, passing Western Disturbances. As such, the 'wet season' there is effectively upto 8-9 months in length, and the amount of rainfall received easily sustains evergreen forests (except for rain-shadowed areas).
Water that has seeped into the soil and thereby into the water table, and into water bodies such as rivers, lakes, etc., tends to remain plentiful for a considerable amount of time following the end of a rainy spell. Deciduous trees thrive better than evergreen trees in regions where the dry season is long enough to severely deplete the water table and moisture available to the trees; if the dry season is not long enough, the deciduous flora can get quickly outcompeted by evergreen flora.
As far as the Western Ghats are concerned, they get an extraordinary amount of orographic precipitation during the south-west monsoon, an amount significant enough to keep the water table replenished during the dry season from ~ November to ~May. The stable high-pressure systems over the Arabian Sea and the influx of hot dry air from the desert regions of Balochistan, Iran and Arabia inhibit pre-monsoonal activity, but inspite of this the forests manage to stick around owing to extraordinary monsoonal precipitation. Perhaps more quantitatively, this can be expressed in the difference between a Tropical monsoon climate and a Tropical savanna climate.
The North-Eastern states get a significant amount of precipitation (amounting to upto a third of the total yearly precipitation in some areas) during the pre-monsoon months of March-May. This pattern is not linked to the monsoon, and is largely driven by local convective thunderstorms (sometimes isolated, sometimes in clusters) formed from diurnal heating in the adjoining Eastern India and the influx of moisture-laden wind from the Bay of Bengal. Other rain-causing factors include lows in the Bay of Bengal and, most noticeably in the winter, passing Western Disturbances. As such, the 'wet season' there is effectively upto 8-9 months in length, and the amount of rainfall received easily sustains evergreen forests (except for rain-shadowed areas).
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