Phytogeography (or plant geography) is the branch of biogeography that studies the geographical distribution of plant species and their influence on the earth's surface.
The current distribution of plants is heavily influenced by geological history and the environmental limits of the plants themselves.
This theory explains how landmasses moved over time, causing the isolation of plant populations or creating "land bridges" that allowed migration. This movement explains why closely related plant species are sometimes found on different continents.
This theory states that a plant's distribution is limited by its range of tolerance for various environmental factors (like temperature, moisture, and light). A species will only exist in areas where the environmental conditions fall within its physiological limits.
Endemism refers to the condition of a plant species being unique to a specific geographic location, such as a specific mountain range, island, or country, and not found naturally anywhere else.
Biomes are large geographical areas characterized by their climate, soil, and specific types of vegetation.
| Biome Type | Climate Characteristics | Vegetation Type |
|---|---|---|
| Tropical Biome | High temperature and rainfall year-round. | Tropical Rainforests, high species diversity. |
| Temperate Biome | Moderate temperatures with distinct seasons. | Deciduous forests or grasslands. |
| Tundra Biome | Extremely cold, short growing season. | Mosses, lichens, and dwarf shrubs; lack of trees. |
India is divided into several phytogeographical regions based on varied climatic and topographic features. These divisions typically include the Western Himalayas, Eastern Himalayas, Indus Plain, Gangetic Plain, Central India, Malabar (Western Ghats), Deccan, and the Andaman/Nicobar Islands.
North-East India is a significant biodiversity hotspot with a wide array of vegetation types.
Special Reference to Assam: The vegetation is dominated by tropical evergreen, semi-evergreen, and moist deciduous forests, with significant riverine grasslands in areas like Kaziranga.
Q: What is the significance of Continental Drift in phytogeography?
A: It explains the "disjunct distribution" of plant families, where identical or related plants are found in widely separated parts of the world.
Q: Why is NE India called a biodiversity hotspot?
A: Due to its unique position at the junction of three biogeographical realms, leading to exceptionally high species richness and endemism in its vegetation.