No real answers, idiosyncratic processes. Effects less in a large community than in a small community. Monocultures more susceptible to pest outbreaks. Pest outbreaks not common in rainforests. Reducing diversity of insect communities with pesticides precipitates pest outbreaks.
Stable communities have more complex food webs.
Stability of tropical systems is overstated, pest outbreaks are known. Rainforests are susceptible to human disturbance. Ag. systems suffer from outbreaks due to a lack of coevolutionary history of the species. If diversity causes stability in natural communities, it does so due to long standing relationships. Food webs that contain reasonable elements show more stability.