Last modified 22nd January 1998
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GENERALIZED KEY TO GLOBAL VEGETATION TYPES.
The definitions for categories are intended as a basis for discussion, and must be regarded as preliminary.
Temperature zones used here;
TROPICAL VEGETATION (mean temperature of coldest month above 15.5°C for forest vegetation, and mean temperature of coldest month above 10°C for all other physiognomic types).
COOLER CLIMATES; SUBTROPICAL AND TEMPERATE (mean temperature of coldest month below 18°C, or below 15.5°C for forest vegetation).
COLD CLIMATES; ARCTIC/POLAR (mean temperature of warmest month below 11°C).
Cover values used here;
FOREST VEGETATION; more than 60% canopy (leaf/branch) cover above a level 8m off the ground.
WOODLAND VEGETATION; 20-60% canopy (leaf/branch) cover above a level 8m off the ground.
SAVANNA/PARKLAND VEGETATION; 2-20% canopy (leaf/branch) cover above a level 8m off the ground.
Note that the descriptions of cover are partly based on a concept of 'cover strata', selectively taking the percentage cover above a particular horizontal plane, as if the leaves and branches above it were casting down a shadow onto this imaginary plane.
NON-SWAMP VEGETATION; WATER TABLE AT OR ABOVE 50% OF THE SOIL SURFACE LESS THAN 50% OF THE TIME, IN AN AVERAGE YEAR.
1. Tropical evergreen broadleaved forest
Mean temperature of coldest month above 15.5°C. Leaf/branch cover above a level 8m off ground, >60% . Cover above 8m at least 50% of broadleaved species. No more that 50% loss of canopy leaf cover at any one time during average year.
2. Tropical deciduous broadleaved forest
Mean temperature of coldest month above 15.5°C. Leaf /branch cover above a level 8m off the ground, >60% during peak month of leafiness. >50% of leaf/branch cover above 8m consisting of Broadleaved plants. >50% loss of canopy leaf cover at some stage in average year, except for Australian Eucalyptus dry forests, where limit of rainforest is defined by where Eucalyptus becomes >50% of canopy.
3. Tropical broadleaved woodland
Mean temperature of coldest month above 15.5°C. Leaf /branch cover above 8m off ground, 60%-20%. >50% of leaf/branch cover above 8m being broadleaved
4. Needle-leaved tropical woodlands and forests
Mean temperature of coldest month above 15.5°C. Leaf /crown cover above 8m off ground > 20%. At least 50% of this cover being composed of needle-leaved plants.
5. Tropical and cool climate scrub.
Less than 20% vegetation cover above a level 8m off the ground. >20% vegetation cover between 8m and 80cm off the ground, during an average year. (temperature limit does not apply)
6. Open Scrub and scrub savanna (tropical and temperate)
Leaf/branch cover above 80cm off ground less than 2%. But total cover above soil level, greater than 25%. (Temperature limit does not apply).
7. Cool evergreen broadleaved forest
Coldest monthly mean temperature during average year, less than 15.5 deg.C. >60% leaf/branch cover above 8m off the ground. >50% of this cover being of broadleaved species. <50% of the broadleaved cover lost simultaneously at some point during an average year.8. Cool deciduous broadleaved forest
Coldest monthly mean temperature during average year, less than 15.5 deg.C. >60% leaf/branch cover above 8m off the ground. >50% of this cover being of broadleaved species. >50% of the broadleaved cover lost simultaneously at some point during an average year.9.Cool needle-leaf forest .
Mean temperature of coldest month less than 15.5°C. Cover above 8m off ground, greater than 60%. Greater than 50% of this cover being needleleaved plants.
10. Parkland
Mean temperature of coldest month less than 15.5°C. Woody/leaf vegetation cover above 8m 2-20%. Cover 8m-0.8m less than the % cover above 8m.
11. Cool woodland
Mean temperature of coldest month less than 15.5°C. Cover above 8m, 20-60%.
12. Tundra
Mean temperature of warmest month less than 11°C. Woody vegetation cover above 0.8m off soil level, <2%. Grass/herb/shrub cover >20%
13. Tropical savanna
Mean temperature of coolest month greater than 18°C. Woody cover above 0.8m, 2-20%. Cover above 8m, greater than the cover in the 0.8-8m height interval.
14. Steppe
Mean temperature of coolest month less than 18°C. Woody cover above 0.8 m, less than 2%. Grass/herb/shrub cover 2-20%15. Semi-desert Shrub or Steppe
Mean temperature of warmest month greater than 11°C.. Cover above 0.8m, less than 2%. Grass/herb/shrub cover 2-20%
16. Cold Semi-desert (semi-desert tundra or cold steppe)
Mean temperature of warmest month less than 11°C.. Cover above 8m, less than 2%. Grass/herb/shrub cover 2-20%
17. Extreme Desert
No temperature limit. Less than 2% cover above 8m off the ground. <2% total grass or herb cover.
WETLAND OR SWAMP ENVIRONMENTS; WATER TABLE AT OR ABOVE SOIL SURFACE FOR >50% OF THE TIME DURING AN 'AVERAGE' YEAR.
18. Herbaceous wetland
No temperature limit. Leaf/branch cover above 80cm less than 2%. Grass/herb/shrub cover >2%.
19. Open Water
No temperature limit. <2% woody (leaf/branch) cover above 80cm. Grass/herb/shrub cover <2%.
20. Wooded Swamp.
No temperature limit. <2 % woody (leaf/branch) cover above 0.8m from the water surface.
INTENSIVELY CULTIVATED ENVIRONMENTS
21. Arable and Orchards
More than 50% of the coverage (within each unit sample square) by fields or orchardsWoody cover above 0.6m from soil, less than 10%. Ploughed or re-seeded each year or two years. = arable
Woody cover above 0.6m from soil, greater than 10%. Planted trees, producing a non-timber harvest each year or every few years = orchard.
PERMANENT ICE AND SNOW
22. Ice and ice-field
More than 50% perennial ice and snow cover, above ground surface (not melting at any time of year).
MOSAIC CATEGORIES
Many areas will be a mosaic of sample squares which fall into different categories. The category which has the largest proportion of squares should be the one which is used to name the area on the map; so if 40% of squares come out as savanna and 60% as forest, the map category should be 'forest' but the map should be annotated to show that the area is also '40% savanna'. The percentage of squares of each category can be indicated by a number, and contour lines drawn on the map to indicate changing percentages of components within the mosaic.