There is an obvious limitation to what one may establish by distinguishing between biological communities on the basis of a selection of ecological criteria and structure characterisation of the vegetation. An important limitation of physiognomic characterisation is that it does not work so well in savannah formations that are subject to varying degrees of dynamism. Savannahs that are the result of fluctuating intensities of burning, draught, and grazing may show considerable differentiation in physiognomy, both in space and in time, while the species in the described units may be remarkably similar. The resulting differentiation may lead to over-representation in a protected areas system. On the other hand, large physiognomic units exist – particularly grasslands - which show remarkable differentiation in at least some of the dominant species that cannot be distinguished on the basis of the physiognomic and ecological criteria of the UNESCO system. This may lead to an under-representation.

In order to be able to achieve greater detail, TNC and the USNVC have expanded the UNESCO system by adding floristic criteria for the USA. They added the possibility of subdividing UNESCO classes with plant species as modifiers. For the needs in the USA, they also brought about some modification in the organisation of the physiognomic-ecological classes. While the UNESCO system is perfectly capable to describe vegetation structures in agricultural systems, it has not been used to do so. For instance, a pine plantation forest could be described as a temperate evergreen needle-leaved forest, while a field of potatoes could be classified as an episodical forb community. Distinction between cultural and (semi-) natural communities is important, and the Americans made an explicit distinction between natural, semi-natural and agricultural (Grossman et al. 1998) biounits. Thus, the USA government and private organisations adapted the UNESCO approach to a physiognomic-ecological-floristic classification system with adequate mapping detail for conservation purposes of that country.

The UNESCO system as applied in the “Map of the Ecosystems of Central America” has added some primary elements to the original design. Where possible, it has followed the principle of the USNVC approach by adding a few floristic elements for further distinction of classes. Of course, this was a very early attempt and will need much more future work. Furthermore it has added an eighth formation for water systems. This element too needs further elaboration. In a number of occasions some biogeographical distinction was made. Ecologically, “moderately” drained was classified as an additional feature. Lastly, different levels of disturbance were mapped when appropriate for affected ecosystems.

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NATUREZA DO MUNDO é o Web site oficial do World Institute for Conservation and Environment, WICE, Es uma red de páginas Web tratando de temas diferentes relacionados à natureza, la conservação el manejo de recursos naturaleiss, parques nacionais y áreas protegidas. Lea aqui porqué creamos Natureza do Mundo. Nossa Methodología explica como produjimos a informação. Nosso Mapa do sitio le ayuda encontrar sua informação no web site. Desfrute!

NATUR DER GANZEN WELT ist, die offiziellen Website der World Institute for Conservation and Environment, WICE. Es ist ein einheitliches Netzwerk von Web Sites, über Themen wie Natur, Natur-Schutz und natürlichem Ressourcen Quellen Hege. Lesen Sie hier warum wir Natur der ganzen Welt gemacht haben. Unsere Verfahrensweise erklärt, wie wir unsere Informationen produziert würde. Unsere Site Map  hilft Ihnen Ihren Weg im Website zu finden. Viel Spaß!

NATUUR UIT ALLE STREKEN is, de officiële Website van het World Institute for Conservation and Environment, WICE. Het is een geïntegreerd Netwerk van websites, over Natuur, Natuurbescherming en het beheer van natuurlijke hulpbronnen. Lesen Sie hier warum wir Natuur uit alle Streken gemacht haben. Onze pagina Methode legt uit, hoe we onze informatie vergaarden. Onze Site Map helpt u op weg door onze website. 

WICE is a worldwide non-government non-profit organization that contributes to the conservation of nature. While it works on a many issues related to the conservation of nature and the protection of the environment, it is particularly committed to the conservation of national parks and other protected areas.

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