OLM 12.2. The relationship between species- and community-level variation in biomass
The phenomenon recurring in many habitats that the biomass production of a community fluctuates less than that of the species it is composed of (Figure 12.22) was explained by the portfolio effect known from investment theory (Ch12.2, p. 261). We have also made the – thus far unproven – statement that „the more diverse our investment portfolio is, the less its total value fluctuates in time” (p.263). We present a mathematical proof to this statement here.