Clouds and temperature drive dynamic changes in tropical flower production.

Tropical forests are incredibly dynamic, showing rapid and longer-term changes in growth, mortality and net primary productivity. Tropical species may be highly sensitive to temperature increases associated with climate change because of their narrow thermal tolerances. However, at the ecosystem scale the competing effects of temperature, light and precipitation on tropical forest productivity have been difficult to assess. Here we quantify cloudiness over the past several decades to investigate how clouds, together with temperature and precipitation, affect flower production in two contrasting tropical forests. Our results show that temperature, rather than clouds, is critically important to tropical forest flower production. Warmer temperatures increased flower production over seasonal, interannual and longer timescales, contrary to recent evidence that some tropical forests are already near their temperature threshold. Clouds were primarily important seasonally, and limited production in a seasonally dry forest but enhanced production in an ever-wet forest. A long-term increase in flower production at the seasonally dry forest is not driven by clouds and instead may be tied to increasing temperatures. These relationships show that tropical forest productivity, which is not widely thought to be controlled by temperature, is indeed sensitive to small temperature changes (1-4°C) across multiple timescales. [ABSTRACT FROM AUTHOR]