Moist Tropical Forests

 

Climatic Conditions

  • Annual rainfall exceeds 250 cm
  • The annual temperature is about 25°-27°C
  • The average annual humidity exceeds 77 percent and
  • The dry season is distinctly short.

Characteristics

  • Evergreen: Due to high heat and high humidity, the trees of these forests do not shed their leaves together.
  • Mesophytic: Plants adapted to neither too dry nor too wet type climate..
What are mesophytes?

●     Unlike hydrophytic plants, such as water lily or pondweed, that grow in saturated soil or water, or xerophytic plants, such as cactus, that grow in extremely dry soil, mesophytes are ordinary plants that exist between the two extremes.

●     Mesophytic environments are marked by average to hot temperatures and soil that is neither too dry nor too wet.

  • Lofty: The trees often reach 45 – 60 metres in height.
  • Thick Canopy: From the air, the tropical rain forest appears like a thick canopy of foliage, broken only where it is crossed by large rivers or cleared for cultivation.
  • All plants struggle upwards (most epiphytes) for sunlight resulting in a peculiar layer arrangement. The entire morphology looks like a green carpet when viewed from above.
  • Less undergrowth: The sunlight cannot reach the ground due to thick canopy. The undergrowth is formed mainly of bamboos, ferns, climbers, orchids, etc.

 

Distribution

  • Western side of the Western Ghats (500 to 1370 metres above sea level).
  • Some regions in the Purvanchal hills.
  • In the Andaman and Nicobar Islands.

Timber

  • Hardwood: The timber of these forests is fine-grained, hard, and durable.
  • It has high commercial value but it is highly challenging to exploit due to dense undergrowth, absence of pure stands, and lack of transport facilities [Read previous posts on Climatic regions to understand how lumbering industry works in Equatorial Rainforests (hardwood) and Taiga Climatic (softwood) conditions].
  • The important species of these forests are mahogany, mesua, white cedar, jamun, canes, bamboo, etc.

 

  • They are transitional forests between tropical wet evergreen forests and tropical deciduous forests.
  • They are comparatively drier areas compared to tropical wet evergreen forests.

 

Climatic Conditions

  • Annual rainfall is 200-250 cm
  • Mean annual temperature varies from 24°C to 27°C
  • The relative humidity is about 75 per cent
  • The dry season is not short like in tropical evergreen forests.

 

Distribution

  • Western coast
  • Assam
  • Lower slopes of the Eastern Himalayas
  • Odisha and
  • Andamans

 

Characteristics

  • The semi-evergreen forests are less dense.
  • They are more gregarious [living in flocks or colonies – more pure stands] than the wet evergreen forests.
  • These forests are characterized by many species.
  • Trees usually have buttressed trunks with abundant epiphytes.
  • The important species are laurel, rosewood, mesua, thorny bamboo – Western Ghats, white cedar, Indian chestnut, champa, mango, etc. – Himalayan region.

 

Timber

Hardwood: Similar to that in tropical evergreen forests except that these forests are less dense with more pure stands (timber industry here is better than in evergreen forests).

 

Climatic Conditions

  • Annual rainfall 100 to 200 cm.
  • Mean annual temperature of about 27°C
  • The average annual relative humidity of 60 to 75 per cent.
  • Spring (between winter and summer) and summer are dry.

 

Characteristics

  • The trees drop their leaves during the spring and early summer when sufficient moisture is not available.
  • The general appearance is bare in extreme summers (April-May).
  • Tropical moist deciduous forests present irregular top storey [25 to 60 m].
  • Heavily buttressed trees and fairly complete undergrowth.
  • These forests occupy a much larger area than the evergreen forests but large tracts under these forests have been cleared for cultivation.

 

Distribution

  • Belt running along the Western Ghats surrounding the belt of evergreen forests.
  • A strip along the Shiwalik range including terai and bhabar from 77° E to 88° E.
  • Manipur and Mizoram.
  • Hills of eastern Madhya Pradesh and Chhattisgarh.
  • Chota Nagpur Plateau.
  • Most of Odisha.
  • Parts of West Bengal and
  • Andaman and Nicobar islands.

 

Timber

  • These provide valuable timers like Teak.
  • The main species found in these forests are teak, sal, laurel, rosewood, amla, jamun, bamboo, etc.
  • It is comparatively easy to exploit these forests due to their high degree of gregariousness (more pure stands).

 

  • They can survive and grow both in fresh as well as brackish water (The mixture of seawater and fresh water in estuaries is called brackish water and its salinity can range from 0.5 to 35 ppt).
  • Occur in and around the deltas, estuaries and creeks prone to tidal influences (delta or tidal forests).
  • Littoral (relating to or on the shore of the sea or a lake) forests occur at several places along the coast.
  • Swamp forests are confined to the deltas of the Ganga, the Mahanadi, the Godavari, the Krishna and the Cauvery.
  • Dense mangroves occur all along the coastline in sheltered estuaries, tidal creeks, backwaters, salt marshes and mudflats. It provides useful fuel wood.
  • The most pronounced and the densest is the Sunderban in the Ganges delta where the predominant species is Sundri (Heriteera).

 

Timber

  • It provides hard and durable timber which is used for construction, building purposes and making boats.
  • The important species found in these forests are Sundri, agar, rhizophora, screw pines, canes and palms, etc.