A vegetation type, or plant community, is identifiable by its distinct appearance compared to other landscape types within a landscape. For example, a grassland and a wetland differ in appearance from each other and from a forest, while a wetland-forest is yet another visibly different vegetation type. Plant species are recognizable by their form, which is related to how the plant functions. For example, in dry environments, plant leaves are more compact with harder surfaces to limit water loss, while plants in wetter environments have larger, “softer” leaves that release water readily when pores open to take in CO2. Such leaves have more surface area for photosynthesis, resulting in faster growth.
This form-function relationship explains why vegetation types differ around the globe. Plant species are adapted to particular climatic conditions according to their proximity to the equator or a coastline, for example, or their elevation.
The geographic regularity of vegetation distribution arises, of course, from the geographic regularity of Earth’s main climatic regions, driven by the global circulation pattern of the Earth’s atmosphere [Box 2013: 466].
Box, Elgene O. & Kazue Fujiwara, 2013, Vegetation types and their broad-scale distribution, Vegetation Ecology 2nd ed., John Wiley Sons, Ltd. Publishing, https://onlinelibrary.wiley.com/doi/book/10.1002/9781118452592