黃金29 TIMBERLINE VEGETATION ON MOUNTAINS - 英檢

請問各位
在TIMBERLINE VEGETATION ON MOUNTAINS(第12篇)
最後一提的第三個選項為什麼錯
=>The temperature at the upper timberline is probably more important in
preventing tree growth than factors such as the amount of snowfall or the
force of winds.

文中:在第四段中Too much snow, for example, can smother trees, and avalanches and snow creep
can damage or destroy them. Late-lying snow reduces the effective growing
season to the point where seedlings cannot establish themselves. Wind
velocity also increases with altitude and may cause serious stress for trees,
as is made evident by the deformed shapes at high altitudes. Some scientists
have proposed that the presence of increasing levels of ultraviolet light
with elevation may play a role, while browsing and grazing animals like the
ibex may be another contributing factor. Probably the most important
environmental factor is temperature, for if the growing season is too short
and temperatures are too low, tree shoots and buds cannot mature sufficiently
to survive the winter months.

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