3) . You are viewing a mountain from western North America in the northern hemis

Question

3). You are viewing a mountain from western North America in the northern hemisphere. The areas labeled A, B, C and D represent different types of vegetation. For example, zone A might be some high-elevation red fir forest, while B could be yellow pine, C might be mixed evergreen forest, and D might be grassland. Notice the distribution patterns of these vegetation zones.

B) Discuss how three environmental factors, light, temperature and moisture might account for the observed vegetation patterns.

C) Why are the zones higher on one slope and lower on the other?

D) Which of these vegetation zones is likely to contain species that are more tolerant of dry conditions and why?

Explanation / Answer

A) If the species A and B exists in zone C, they equally co-dominate on N and S-facing slopes. This is because the species A and B are long trees that are located near the hill top. But normally the long trees grow best at toe of the hill and their existence at toe increases the safety factor by 10 %.

B) The temperature is very low towards north when compared to south side of a mountain. Hence, we can see more vegetation towards south in the given case. The suitable temperature exists in the center of the mountain. Moisture and temperature decreases with the increase of the height. In the given case, long trees are located in ‘A’ and ‘B’ zones that are the located nearly top of the hill. Hence, penetration of sunlight to the bottom of hill is less. Hence, the vegetation at the toe of the hill is very low.

C) Vegetation and slope stability are interrelated. It depends on variety of factors like soil, rainfall, plant species, slope aspect, and steepness of slope. In the given case, the vegetation is high in “C” Zone. This is because the trees or plants that are located in this region can acquire sufficient temperature, moisture, and sunlight. Normally, the larger trees have to be planted at the toe of hill for better vegetation.

D) The A zone trees are more tolerant to dry conditions. This is because with the increase in height the temperature and moisture decreases. The high elevation of mountains receives high intensity of light than basal lines.

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