Ecology 5th Edition by Manuel Molles

Exercise 19

Field experiments demonstrate that variation in soil fertility influences terrestrial primary production. However, we cannot say that nutrients exert primary control. That role is still attributed to temperature and moisture. Why do ecologists still attribute the main control of terrestrial primary production to temperature and moisture? Consider the difference in primary production between arctic tundra and tropical forest (see fig. 18.2) and the extent to which nutrient additions (Shaver and Chapin 1986) changed primary production in tundra.
Figure 18.2 Relationship between actual evapotranspiration and net aboveground primary production in a series of terrestrial ecosystems (data from Rosenzweig 1968, Kaspari, O'Donnell, and Kercher 2000).