Nicola Arndt und Matthias Pohl - Neobiota

In practical terms, delineation of EZ level 2 adapting Köppen-Trewartha’s climatic types was
proposed as the working level for definition and mapping of global classes. This will be accomplished
by using both macroclimatic data 4 and existing climax or potential vegetation maps. Use of vegetation
maps will assure a more precise delineation of the Ecological Zones 5 . Using generalized climate maps
alone might result in a final product where the zones actually mapped could probably correspond
poorly to boundaries of homogenous vegetation transitions.
3.2 Cambridge expert consultation
The proposed approach and classification scheme briefly outlined above was presented and discussed
at an expert consultation in Cambridge from 28−30 July 1999, organized by WCMC (FAO 2000). The
participants were mostly regional experts in ecological zoning and forest/vegetation mapping. Case
studies on North America and South America were presented as well, illustrating the overall concept,
methods, and utility of the map in an operational context. The workshop adopted, with some
modifications, the proposed classification system based on Köppen-Trewartha climatic types in
combination with potential natural vegetation as a sound basis for global ecological zoning. The
workshop results indicated that the proposed system could be implemented in all regions, both in
scientific and practical terms. Source input maps were identified for all regions, most of them available
in digital format. It was noted that the Köppen-Trewartha system might not match well with potential
natural vegetation in specific regions, for instance Australia. Some modifications to the proposed
classification were made to better reflect the vegetation zonation (see Table 1), and they include:
a) the separation of a mountain systems zone at level 2 in four broad climatic domains: tropical,
subtropical, temperate, boreal (not applied in polar domain)
b) the subdivision of the boreal zone into a more northerly (poleward) tundra woodland and a
southerly coniferous forest zone (approximately corresponding with the Taiga in former USSR)
c) the division of the tropical seasonally dry climate type (Aw) into two: one with a short dry season,
roughly corresponding with moist deciduous forest, and one with a long dry season, corresponding
with dry deciduous forests and woodlands.
4 Among the existing climate classification systems, the one by Köppen-Trewartha is found to be the least
demanding on data, which is primarily based on precipitation and temperature − an important consideration
from the production standpoint and may account for its wide use. As meteorological stations around the world
routinely collect values for these attributes and the information is generally available in existing maps, this was
seen as an additional advantage from the perspective of producing the map and database, which would require
a relatively consistent global distribution of input data. Other global climate classification systems, for
example THORNWAITE (1931) and HOLDRIDGE (1966), call for evapo-transpiration data, which is not
uniformly available at the global level.
5 The FAO Ecological Zone maps developed during Forest Resources Assessment 1990 for the tropics used a
similar approach. A hierarchic system was adopted, using climatic and physiographic factors for identifying
the regional classes or Ecological Zones. These zones were defined by aggregation of more detailed
ecofloristic zones (EFZ). The classification criteria for EFZ included physiognomy, phenology, floristics and
vegetation dynamics (FAO 1989). The dominant or characteristic species of the natural flora were used as
indicators. Boundaries of ecofloristic zones were delineated with the help of existing potential, mostly
national, vegetation maps, and brought to a common classification and scale. Class boundaries were delineated
using standardized vegetation maps of the tropical regions.
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