Syntaxonomical Synopsis of the potential natural plant communities of North America, I
Itinera Geobotánica 10: 5-148 (1997)
|Go to: Contents - Previous Page - Next Page
Bioclimatical and biogeographical data - Bioclimatical indexes
To make this publication more quickly comprenhensible several simple definitions about bioclimatical indexes and geobotanical terms used in the text are included. Additional information can be found in recent papers (Rivas-Martínez, 1995, 1996).
In "Global Bioclimatics" (Rivas-Martínez, in press) we have only used meteorological data easily obtainable statistically, treated as climatic parameters: single and summatory or as bioclimatic indexes: combinations of parameters, both obtained through intentionally easy arithmetical formulas. Both values have been only used when some thersholds have shown a good relation with the vegetation changes and, in consequence, high predictive value.
T: Yearly average temperature in centigrade degrees.
M: Average of the maxima temperature of the coldest month.
m: Average of the minima temperature of the coldest month.
Tmin: Coldest month average temperature.
Tmax: Warmest month average temperature.
P: Yearly average precipitation in mm.
Ps: Summer precipitation or precipitation of the driest quarter of the year in mm. Total of the average precipitation of the three summer months measured in mm. In extratropical zones (northern 27ºN and southern 27ºS) used to be in the northern hemisphere: June + July + August; and in souther hemisphere: December + January + February. In tropical zones it is considered to be "estival" precipitation, that occurs during the three consecutively driests months in the year, independent to their average temperature.
Pp: Yearly positive precipitation. Total of average precipitation in mm of the months with average temperature higher than 0ºC.
Tp: Yearly positive temperature. Total in tenths of degree of the monthly average temperature higher tahn 0ºC.
Ic: Continentality index (thermic yearly interval). Ic = Tmax - Tmin. Is a number that express thedifference in degrees centigrades between the average temperature of the warmest month (Tmax) and the same of the coldest month (Tmin) in the year. The continentality types are: hyperoceanic (0-11), euoceanic (11-18), semioceanic (18-21), semicontinental (21-28), eucontinental (28-45) and hypercontinental (45-65), associated with the oceanic (0-21) and continental (21-65) macrotypes.
Io: Ombrothermic index. Io = Pp. /Tp. The quotient resulting value of the yearly precipitation in mm of the months with average temperature higher than 0ºC by the value, expressed in centigrade degrees resulting from the total of the monthly average temperatures higher than 0ºC
It: Thermicity index. It = (T + m + M)10. The sum in tenths of degree of T (yearly average temperature), m (average temperature of the coldest month of the year minima), M (average temperature of the coldest month of the year maxima).
Association. Fundamental and basic unit of the Phytopsociology. It is a vegetal community type with particular floristic, ecological, biogeographical, succesional, historic or antropogenical features. Own charaxteristic and differential species or a precise characteristic species combination of higher ranks statistically faithful.
We may know it by means of the comparative study of relevés, in which the floristic composition is annotated and quantified, as the rest of the ecological and geographical information of a particular homogeneous vegetal community example. The association relevé taking is the most important operation of the phytosociological research. The associations with similar floristic composition , stage, biotipe and habitat or vicariant may be united in types or units of higher rank (alliances, orders, classes).
Biogeography. Science dealing with the distribution causes of species and biocoenoses location on Earth. Taking in account the actual and past areas of taxa and syntaxa, as well as information coming from other Natural Sciences (Physical Geography, Edaphology, Bioclimatology, etc.) it tries to stablish a typology or systematics of the emerged territories of the plante, whose units in hierarchical devreasing order: Kingdom, Region, Province, Sector, District and Tesela.
Catena. Conjunct of contiguous plant communities ordered by any changing ecological factor (temperature, moisture, topography, etc.). It is the landscape concretion of the zonation phenomena.
Climax. Final stage of equilibrium in the geobotaniocal succesion. Plant community or phytocoenose territorially representing the stage of biologiocal stable maximum. It can be also employed as expression of a mature phytocoenose and as the last stage or stable association of a vegetation series.
Climatic dominion. Area where a climatophilous vegetal association has really or virtually the climax function. Taking in account its usual pluriteselar diversity, can be recognized more homogeneous lower ranked units.
Geosigmetum. Also denominated geosigmassociation or geoseries, is the basic unit of the integrated or Phytosociology ( Geosinphytosociology). It. tries to be the catenal and succesionist expression of the vegetal landscape science. It is built up with the contiguous sigmeta or vegetation series.
Phytosociology. Science dealing with biocoenoses from a botanical perspective (Phytocoenoses or Phytosyntaxa). In other words, it pays attention to the plant communities, their relations with the environment and the temporal processes modifying them. With all this information, by means of and inductive and statistic method, based in the reality of the vegetation phytosociological relevé tries to create an universal hierarchical typology using the association as the basic unit of the taxonomic system. Nowadays we distinguish, besides the classical or Braun-Blanquet"s Phytosociology (association level), the dynamic-catenal or Landscape Phytosociology, whose units are the series or sigmetum (Dynamic or Successional Phytosociology) and the sigmetum or geoseries (Catenal Phytosociology).
Potential vegetation. Stable plant community that would exist on a given area as a consequence of the progressive succession if the man did not influence and alter/upset the ecosystems. In the practise the potential vegetation is considered as a synonym of climax and the same that primitive vegetation (not altered yet by man). But we must distinguish between the climatophilous natural potential vegetation and the edaphophilous series (permanent plant communities).
Sigmetum. Typological unit of the Dynamic Phytosociology. It is the successionist expression of vegetation series or climacic domain, meaning, belonging to a geographic and ecological homogeneous territory in which an association has the function of climax. It is also denominated sinassociation or vegetation series.
Succession. Natural process by which several plant communities or stages follow several others in the same place unit or tesela. We can talk about progressive succession the one going to the stable optimum or climax and about regressive succession the opposite (regression; subseral stages). The progressive and regressive processes do not follow necessary the same stages.
Tesela. Elemental unit of the Biogeography. It is a territory or geographic surface, with more or less extension, ecologically homogeneous. It means it has only one potential vegetation type and then only one sequence of substitution plant communities.
Types of forests. In the followint table on summarized the types of forests and life forms (biotypes) deppending of the heigth of trees and canopies.
Vegetation series. Geobotanical unit that express all the plant communities collection of stages, that can be found in similar teselar places as a result of the succession processs, that includes as well the representative vegetation type of the mature stage of series head (climax) as the initial or subseral communities replacing them. Conceived this way, the vegetation series is a synonym of synassociation or sigmetum, basic unit of the Dynamic Phytosociology (Sinphytosociology). If we integrate to a series their contiguous ones, meaning, if we take in account besides the succession the catenal phenomenon, -for instance, the climatophilous and edaphophilous series that can be in contact- we have another complexer unit denominated geoseries (geosigmetum), elemental unit of the Catenal Phytosociology.
Zones and latitudinal belts in the Earth. In the Earth can be distinguished three wide latitudinal zones: 1. Tropical (0º to 30º N & S), 2. Temperate (30º to 51º N & S), 3. Frigid (51º to 90º), and also ten latitudinal minor belts (see below).
Bioclimatical data and tables
Continentality types in the Earth. The simple continentality index (Ic) is a number that express the difference in centigrades degrees between the average temperature of the warmest month (Tmax) and the coldest one (Tmin) in the year. Ic = Tmax - Tmin. The continentality types and subtypes that we recognized in the Earth are in the next table.
Global bioclimatics. In the next table is summarized in only one page the last approach (02.05.97) of the Bioclimatical Classification System of the World.
insertar tabla del archivo sinop-in.doc
Macrobioclimatical map of North America. One first general approach of the bioclimatical map of North America is published in this paper.
An Biogeographical typologicalsynthesis of the regions, provinces and sectors of North America (bilingual) is proposed below. Also is presented a synthesis at subsector level of Californian biogeographical region. A detailed map of biogeographical sectors of Center and West United States is also given.
Provinces, sectors and subsectors of the Californian biogeographical region.