TEMPERATURE, PHOTOPERIOD(SUNLIGHT) AND PRECIPITATION
Temperature
The character and extent of vegetation are mainly determined by temperature along with humidity in the air, precipitation and soil. On the slopes of the Himalayas and the hills of the Peninsula above the height of 915 metres, the fall in the temperature affects the types of vegetation and its growth, and changes it from tropical to subtropical temperate and alpine vegetation.
Table 5.1: Temperature Characteristics of the Vegetation Zones
Photoperiod (Sunlight )
The variation in duration of sunlight at different places is due to differences in latitude, altitude, season and duration of the day. Due to longer duration of sunlight, trees grow faster in summer.
Precipitation
In India, almost the entire rainfall is brought in by the advancing southwest monsoon (June to September) and retreating northeast monsoons. Areas of heavy rainfall have more dense vegetation as compared to areas of less rainfall.
Have you ever thought as to why forests are important for human beings? Forests are renewable resources and play a major role in enhancing the quality of environment. They modify local climate, control soil erosion, regulate stream flow, support a variety of industries, provide livelihood for many communities and offer panoramic or scenic view for recreation. They control wind force and temperature and cause rains. They provide humus to the soil and shelter to the wildlife. India’s natural vegetation has undergone many changes due to several factors, such as the growing demand for cultivated land, development of industries and mining, urbanisation and over-grazing of pastures.
The vegetation cover of India in large parts is no more natural in the real sense. Except in some inaccessible regions, like the Himalayas, the hilly region of central India and the marusthali, the vegetation in most of the areas has been modified at some places, or replaced or degraded by human occupancy.
More to know
According to India State of Forest Report 2011, the forest cover in India is 21.05 percent.
Activity :
1. Celebrate Van Mahotsav in your school/locality and plant a few spalings and notice their growth
2. Study the bar graph (Figure 5.1) and answer the following questions.
i) Name the state having maximum area under forest cover.
ii) Name the union territory having minimum area under forest cover and why?
Figure 5.1: Area under Forest Cover
Let’s find out
1. Why are the southern slopes in Himalayan region covered with thick vegetation cover as compared to northern slopes of the same hills?
2. Why are the western stopes of the Western Ghats covered with thick forests and not the eastern slopes?
Source: This topic is taken from NCERT TEXTBOOK