14週 (1) 5-2 p.84~p.86

Many of the world's natual temperate grasslands have disappeared because their fertile soils are useful for growing crops and grazing cattle.
Cold grasslands, or arctic tunara, lie south of the arctic polar ice cap.During most of the year, these treeless plains are bitterly cold, swept by frigid winds, and covered with ice and snow.Winters are long and dark, and scant precipitation falls mostly as snow.
Under the snow, this biome is carpeted with a thick, spongy mat of low-growing plants, primarily grasses, mosses, lichens, and dwarf shrubs.Trees or tall plants cannot survive in the cold and windy tundra because they would lose too much of their heat.Most of the annual growth of the tundra's plants occurs during the 5-to 8-week summer, when the sun shines almost around the clock.Figure 3 on p.S50 in Supplement 11 shows some components and food-wed interactions in an arctic tundra ecosystem.


世界上有許多的溫和草原消失掉，因為這些肥沃的土壤常被我們用來種植作物和放養牲口。

冰原、北極寒帶草原和北極南部的冰冠，這些無樹木的草原長年寒冷、吹著強烈冷風和覆蓋著冰雪，冬天時為永夜且缺乏降雨，主要為降雪。

在雪下，這生物群系覆蓋著厚實如海棉狀草蓆的低等植物，主要為草、青苔、地衣和矮小的灌木，像樹和一些高的植物不能存活在這寒冷多風的苔原因為他們會遺失掉他們所需的熱量，許多的一年生苔原植物他們得生長期間發生在5-8星期的夏天，當太陽日以繼夜的照射時。在補充P.S50 中有北極苔原生態系統的組成和食物網的互動。