Plant lineage biome shifts within southern hemisphere landmasses.
From Crisp et al., Nature, 2009.
(1) Wet forest: closed canopy of trees, typically in high-precipitation climate. (2) Sclerophyll woodland or heathland: most species are sclerophyll shrubs;
either on low-nutrient soils or in Mediterranean climate or both. Local types include fynbos (Africa); eucalypt-dominated woodland and open forest, kwongan, wallum and Triodia-dominated ‘hummock-grasslands’ (Australia); chaparral (America); and maquis (New Caledonia). However, this biome excludes true grasslands and rainforests with scattered emergent eucalypts.
(3) Savannah: most species are graminoids or forbs, with variable presence of trees and shrubs; dominant grasses always C4; climate monsoonal (summer rain, dry winter).
(4) Temperate grassland: most species are grasses or forbs, with variable presence of trees and shrubs; grasses can be either C3 or C4; climate has cold winters, otherwise various but not arid. Can include ruderal and grassy riparian patches.
(5) Arid: mean annual rainfall ,300 mm, to ,400 mm in subtropics; includes semi-arid under European definitions; graminoid cover sparse in comparison with grasslands, if present at all; variable mixture of forbs, shrubs and trees.
(6) Alpine or tundra: above treeline, cover comprises graminoids, forbs and shrubs.
(7) Bog: permanently saturated peaty soil normally lacking surface water; not including seasonally flooded ground (swamps, floodplains) or riparian habitat, which we include in the wider biome within which they are embedded, such as sclerophyll or forest.
Species of other azonal habitats (cliffs, riverbeds, coastal strands, aquatics) were few in our data set and were included in the biome in which they are embedded.
We are aware that, as climate changed through the Cenozoic era, biomes fluc- tuated in size and changed in taxonomic composition, and that some were more stable than others. Despite these changes, the defining characteristics of the biomes, which are reflected in the physiological and morphological adaptations of species to the biome, have been maintained from the late Eocene epoch to the present.