Who conducted long-term ecosystem experiments using outdoor plots?

Give scientific reasons: Biodiversity is important in the maintenance of the biosphere and its ecosystem.

$...............$ found that plots with more species showed less year-to-year variation in total biomass. Increased diversity contributes to higher productivity.

What characteristics make a community stable?

Is it possible that productivity and diversity of a natural community remain constant over a time period of,say $100$ years?

Which of the following characteristics are seen in a stable community?
$i$. It is strong enough to withstand environmental disturbance and recovers quickly.
$ii$. It is resistant to invasive species.
$iii$. It exhibits constant change in biomass production over a period of time.
$iv$. It has more species diversity.