Why does biodiversity incrase productivity throughout organisms?

Question

Why does biodiversity incrase productivity throughout organisms?

Answer 1

One reason that biodiversity increases productivity is through niche complementarity.  Niche complementarity occurs when two or more plant species occur in an area but are not directly competeing for the same resources.  An example of this is with cool-season grasses and warm-season grasses.  Each of these grasses grows at different times during the year.  So their growth, and therefore resource requirements, are temporally seperated.  Therefore a field with both grasses will be more productive than a field with only one type, because the field with both grasses will have season-long growth and the two grass types will not be in direct competition.

Other examples of niche complementary are rooting depths (shallow and deep rooted plants), differences in resource requirements, among others.

Facalitiation is another reason diversity increases production.  An example of this is where nitrogen-fixing legumes supply extra nitrogen for other plants.  In this case, the presense of legumes is facilitating the growth of other species.

The sampling effect is a simple theory that states that as diversity increases, the chances that a very productive species will be present increases.  These productive species then increase the total production of the ecosystem.

All of these probably contribute to higher productivity.