The basis for rainforest diversity and Biosphere 2

A miniature rainforest created in the glass-enclosed Biosphere 2 mesocosm in Arizona was compared with montane rainforest in Puerto Rico to study the basis for biodiversity and succession. Initial seeding of high plant diversity was a technique for determining by extrapolation the carrying capacity in Biosphere 2 and in disturbed areas in Puerto Rico. In Biosphere 2 the rainforest area was started in 1991 with 1890 plants of 316 species in 0.19 hectares. Three hundred and thirty-nine plants in 92 species were added in 1993. A diversity index, species per 1000 individuals counted, decreased from 250 in 1991 to 96 in 1998 compared to 60 in the comparison forest while the Shannon-Wiener index decreased from an initial 5.39 to 4.64 in 1996 compared to 4.62 in the comparison forest. Although normal populations of insects and pollinators were absent, vegetative reproduction established productivity, diversity, hierarchy and developed soil profiles approaching those in the comparison forest.;Graphs of cumulative species versus individuals counted were analyzed to identify mechanisms affecting diversity including seeding, competition for excess nutrients and carbon dioxide, extinction rate, seasonal change in insolation, and pruning and management by humans.;The productive basis for diversity was simulated with a model of production, consumption, and recycle that included management alternatives. Simulation runs showed total biomass production highest when the weedy vine biomass was regularly trimmed and removed.;Another model of main factors affecting diversity was simulated with a minimum species limit to help explain the observed patterns and anticipate species carrying capacity. With an addition of 50 new species after 2 years, the simulation showed an increase in diversity and decrease in biomass after 10 years when compared to the simulation without further additions. Emergy and emdollar evaluation showed resources required for developing the rainforest in Biosphere 2 were 2300 times larger than those for the natural succession.