Brief Characterizations of Major Sea-level Climate/Vegetation Types

[add extreme desert, between 2 and 3]

1. Wet tropics—All plants are evergreen.  Dense, closed-canopy.  Very many families, many or most consisting of many genera and species.  Most plants are woody, and trees and vines/lianas predominate (not very many shrubs).  Some trees are very tall.  Overall shape/form/size of leaves and whole plants extremely variable, including by far the largest leaves.  Epiphytes abundant, but very few terrestrial perennials or bulbs, almost no annuals; no succulents except epiphytes.  Palms abound, also banana-like plants, ferns, tropical bamboos.  No conifers (unless “primitive” types).  No fall color of course.  (The realm of gigantism—buttress trunks on many trees).
2. Northern Hemisphere—“rich” subtropical deserts with monsoon climate, winters not very cold.  Many families (all of tropical origin) but not very many species in each.  Succulents and semi-succulents (like Yucca, Agave, and Dasylirion); bulbs; annual, suffrutescent perennials; shrubs; small trees (mostly in Fabaceae).  Many plants are spiny, all trees and shrubs have very small leaves; legumes have finely divided leaves with tiny leaflets.  All evergreen or drought-deciduous, it hardly seems to matter which.  No fall color.  Vegetation is open, sparse.  Delicate “ferny” overstory and short or no understory, but lots of bulky, “sculptural” succulents of many forms.  No epiphytes, almost no ferns, no conifers, no oaks?
3. Northern Hemisphere Mediterranean climates—mostly evergreen, canopy dense (woodland) to absent (scrub and grassland).  Trees lowish.  Families and species of woody plants few; few families of herbs but many species, especially of annuals.  Bulbs and perennials also abundant.  No epiphytes, very few succulents, few? spiny plants.  Sclerophylls common.  Conifers and oaks begin here.  Few palms or none.  Leaves small but rarely finely divided as in desert trees.  Little fall color.  Not much diversity in size, shape, or color of leaves (unlike tropics).
4. North Temperate climates—arid version is grassland.  Mesic version is dense deciduous woodland, with conifers increasing toward the north and evergreen dicots increasing toward south.  Families and species relatively few in all categories.  Flora more-or-less evenly divided between woody plants and herbs, but fewer bulbs than in desert and Mediterranean, and very few annuals.  Leaves average larger than in desert and Mediterranean, but more uniform and smaller than in tropics, rather uniform except for subtle shape differences, thinner-textured (because deciduous) and brighter/paler green than in Mediterranean.  No shrub-dominated communities, not many shrubs in any case.  But unlike other types in having magnificent fall color.  Snowy winters and rainy warm humid summers.  No epiphytes or succulents, but hardy bamboos.
5. Northern Montane and Boreal Conifer Forest—Cool rainy summers; long, cold, snowy winters.  Very few genera and species, mostly conifers with a few deciduous dicots (Vaccinium, birch, aspen, willow).  Understory can be fairly diverse, but few or no bulbs, and annuals.  Fall color limited but conspicuous.  No epiphytes or succulents of course.
6. Tundra (above treeline) very few families, few species, all perennial herbs, none succulent, no bulbs? Although there can be conspicuous red fall color provided by prostrate vacciniums, etc.

Trends:  diversity of forms and habit as well as of families and species is by far the greatest in the tropics, decreasing rapidly northward.  The only thing the tropics don’t have that others do is deciduous species, fall color, or many annuals (or bulbs?) or succulents.

Gestalt-wise, wet tropics are VERY different from dry subtropics (desert) which in turn is VERY different from the rest.  The last three grade into each other.