Why does a rain forest have more bio diversity then a temperature forest

Tropical forests, including evergreen rainforests, cloud forests, seasonal deciduous forests and mangrove forests, have the highest biodiversity of all terrestrial biomes. Tropical rainforests, in particular, cover less than 7 percent of the Earth’s surface but harbor an estimated half of all existing plant and animal species. A small plot can yield hundreds of tree species – as many as all North American temperate and boreal forests combined -- and one reserve in Peru has more than 1,200 different butterflies. Dry tropical forests contain some of the same species as rainforests but fewer species overall. Among the major temperate forest types (temperate coniferous, rainforest, deciduous and mixed forests), temperate deciduous and mixed forests -- which include both deciduous and coniferous species -- have the highest biodiversity. Some temperate coniferous forests consist of only a few tree species, but the chatter and songs of great varieties of birds often fill their borders.( from the science book online )