Abstracts

Forest Ecosystems

The goal of the paper is to represent a conceptual bioclimatic model of the Eurasian subarctic and boreal ecosystems. The model seems to be useful for terrestrial ecosystems classification, for biodiversity arrangement across the zones and ecoregions and for evaluation of climatic parameters of terrestrial ecosystems. Taking into account that ecosystems and populations are functioning in a landscapes context, we use zonal type of landscape by A.G.Isachenko (1988) as the basis unit for land cover classification. The materials and methods of climatic ordination are published (Nazimova, 1996; Nazimova, Polikarpov, 1995, 1996).

The resulting diagram indicates general patterns remarkably similar to those visible on geographic map in spite of that the climatic space is not the same as geographic space. Principally, the axes in our diagram differ from those on a map.

According to our concept, the system-forming factors include regional biota composition, degree of continentality, heat and water supply. For the purpose of comparative biodiversity analysis in the global and subcontinental scale the axes of continentality (X - Coefficient of continentality by Conrad, Cc) is preferable in combination with the axes of heat supply (Y - Sums of active temperatures, SAT). In earlier publications it was shown that the two-dimensional scheme of Eurasian life zones in the Holdridge system was not as informative as our empirical model concerning climatic areas of forest-forming tree species.

Using range of continentality throughout boreal Eurasia it is possible to distinguish and characterize 7 landscape-climatic sectors from the Atlantic up to the Pacific shores of the continent. The sectors differ by proportion of the main forest-forming tree species, ecobiomorphs, geoelements of flora, etc. Each sector is characterized by a spectrum of zones and subzones and their climatic areas. The thresholds are continuous but rather definable. For example, Betula tortuosa and B. ermannii represented in oceanic sectors, are replaced by Picea species in moderate continental and continental climate, by Pinus sibirica and Abies sibirica in the continental but less severe climate of Siberian mountains and plains. When values of Cc reach 70 -90 (and even 98 in Verhoyansk), only Larix species (Larix sibirica, L. gmelinii, L.cajanderi) dominate in the ecoregions. It is possible to represent the climatic areas of separate tree species and population in two- and multidimensional climatic space using data base "BIOME-97".

The conceptual bioclimatic model of Eurasian terrestrial ecosystems is a result of modeling on regional level when realistic geography of the ecosystems is involved. This model seems to be an invariant system where continuous climatic space is filled by some characteristics of ecosystems. In such a way considerable data on populations, species, communities may be plotted in this ordination space and analyzed. Using neural net technology and biome models it is possible to analyze climatic reasons of forest ecosystems biodiversity.

The virtue of this graphic model is of some heuristic value as it discovers some things which are not able to be visualized on geographic maps.

The study is supported by RFFI, grant №00-04-48608 and Integration Project SB RAS № 66.

Note. Abstracts are published in author's edition

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