The Tropical-subtropical forests biome includes moderate to highly productive ecosystems with closed tree canopies occurring at lower latitudes north and south of the equator. Fragmented occurrences extend to the subtropics in suitable mesoclimates.

High primary productivity is underpinned by high insolation, warm temperatures, relatively low seasonal variation in day length and temperature (increasing to the subtropics), and strong water surpluses associated with the intertropical convergence zone extending to wetter parts of the seasonal tropics and subtropics. Productivity and biomass vary in response to: i) strong rainfall gradients associated with seasonal migration of the intertropical convergence zone, ii) altitudinal gradients in precipitation, cloud cover, and temperatures, and iii) edaphic gradients that influence the availability of soil nutrients.

Species diversity and the complexity of both vegetation and trophic structures are positively correlated with standing biomass and primary productivity, however, trophic webs and other ecosystem processes are strongly regulated from the bottom-up by the dominant photoautotrophs (trees), which fix abundant energy and carbon, engineer habitats for many other organisms, and underpin feedbacks related to nutrient and water cycling and regional climate.

Complex nutrient cycling and/or sequestering mechanisms are common, countering the high potential for soil nutrient leaching due to high rainfall. Plant species exhibit leaf plasticity, shade tolerance, and gap-phase dynamics in response to the periodic opening of canopy gaps initiated by tree death, storm damage, and lightning strikes. Fires may occur in ecotonal areas between these forests and savannas.

Biogeographic legacies result in strong compositional distinctions and consequently some functional differences among land masses within the biome