Phytogeographical regions of India | Botany Optional for UPSC PDF Download

Introduction

India, with its vast expanse and diverse landscapes, is a land of remarkable ecological diversity. One of the key factors contributing to this diversity is its phytogeographical regions, each characterized by a unique combination of climatic conditions and distinctive types of vegetation. In this article, we delve into the nine phytogeographical regions of India, as identified by D. Chattarjee in 1962, shedding light on their individual characteristics and ecological significance.

Western Himalayas

The Western Himalayas, an awe-inspiring region, encompass north and south Kashmir, portions of Punjab, and the Kumaon region of Uttaranchal. With an average annual rainfall ranging from 100 to 200 cm, this region experiences varying degrees of moisture. The outer southern ranges are relatively wet, while the inner areas tend to be drier. High altitudes are often adorned with snowfall during winters. The Western Himalayas can be further subdivided into three distinctive zones:

Eastern Himalayas

Stretching from the eastern part of Nepal to Arunachal, the Eastern Himalayas exhibit a warmer and wetter climate compared to their western counterparts. They boast higher tree and snowlines, elevated by about 300 meters. This region's tropical temperatures and ample rainfall give rise to remarkable species diversity, especially in the oak family, although conifers are less abundant here. Similar to the Western Himalayas, the Eastern Himalayas consist of three distinctive zones:

Indus Plain

• The Indus Plain, comprising parts of Punjab, Delhi, Rajasthan, Gujarat, and Cutch, experiences extremely dry and hot summers, followed by dry and cold winters. Annual rainfall in this region is generally less than 70 cm, with some areas receiving a meager 10-15 cm. 
• Although this region was once lush with dense forests approximately 2000 years ago, extensive cattle grazing and other biotic factors led to their destruction. Presently, the Indus Plain features tropical thorn forests and grasslands in select areas.

Gangetic Plain

Encompassing portions of Delhi, Uttar Pradesh, Bihar, West Bengal, and Orissa, the Gangetic Plain experiences annual rainfall ranging from 50 cm to 150 cm from east to west. The vegetation in this region comprises tropical moist deciduous forests, dry deciduous forests, thorn forests, and mangrove forests.

Assam

Covering most of Assam, this region is characterized by high temperatures and substantial rainfall. The lower plains feature tropical evergreen and wet temperate forests, while hilly tracts up to 1700 m altitude boast subtropical pine forests.

Central India

• Central India, comprising parts of Orissa, Madhya Pradesh, the Vindhyan region, and Gujarat, primarily consists of hilly areas with altitudes ranging from 500 to 700 m. Annual rainfall averages between 100 and 170 cm. This region experiences frequent biotic disturbances, resulting in the degradation of forests into thorny forests in open areas. 
• The vegetation here includes tropical moist deciduous forests, primarily Sal forests in areas with annual rainfall above 150 cm, and mixed deciduous forests in regions with 125-150 cm annual rainfall. Areas with annual rainfall below 125 cm are home to tropical thorn forests.

Western Coast of Malabar

• This small region, stretching from Gujarat to Kanyakumari along the Western Ghats, boasts a warm, humid climate with annual rainfall exceeding 400 cm. The coastal areas exhibit a tropical climate, while the hills experience temperate conditions. 
• The vegetation in this region is characterized by tropical wet evergreen, moist evergreen, and moist deciduous forests. Wet temperate forests (Sholas) thrive in the Nilgiri Hills, while mangrove forests are found in saline swamps along the coasts.

Deccan

The Deccan region encompasses southern Peninsular India, from southern Madhya Pradesh to Kanyakumari, excluding the Western Ghats. Annual rainfall in this region averages about 100 cm. The vegetation here primarily includes tropical dry evergreen, dry deciduous, and swamp forests.

Andaman and Nicobar

• Comprising the Andaman and Nicobar Islands, this region experiences a warm and humid climate, characterized by high temperatures and significant annual rainfall. The vegetation is diverse, featuring littoral mangrove, evergreen, semi-evergreen, and deciduous forests.
• In conclusion, India's phytogeographical regions are a testament to the country's ecological diversity, each contributing to the rich tapestry of its natural heritage. These regions serve as vital ecological niches, housing unique flora and fauna, and understanding their distinct characteristics is crucial for conservation efforts and biodiversity preservation.