The tundra is the coldest of all the biomes. It is characterized by extremely low
temperatures, little precipitation, poor nutrients, low biotic diversity, simple
vegetation structure, poor drainage, short growing and reproductive seasons, and
large population-size oscillations.
Figure 4.30 Tundra climatographDead organic material functions as a nutrient pool. The two major nutrients
are nitrogen and phosphorus. Biological fixation utilizes the enzyme nitrogenase
to convert atmospheric nitrogen (N 2 ) to ammonia (NH 3 ), a form of nitrogen that
plants can utilize. This process is accomplished by free-living soil bacteria that
form associative relationships with legumes and other plants. Phosphorus is an
important nutrient in tundra ecosystems and can limit primary production. The
availability of phosphorus is largely driven by soil characteristics, e.g., pH,
organic carbon, and the abundance of phosphorus absorbing elements, such as
aluminum or iron.