Tropical alpine grasslands and herbfields are limited to a few mountainous areas of Africa, the Americas and southeast Asia. Productivity is low, limited by dry conditions, rocky substrate and nightly cold, but is not strongly seasonal. Snow and fog are common. Typical flora includes mosses, lichens, and flowering plants including distinctive megaherbs and low shrubs. Plant species have adaptations for cold dry conditions, such as tiny leaves, cushion and rosette growth forms and slow growth. Plant composition is affected by competition and facilitation between species, as well as grazing and occasional fires. Simple foodwebs include invertebrates, small mammals and reptiles, along with visiting predators and occasional herbivores from lowland savannas.