Boreal zone

Table 3 presents the averaged data for the whole forest area of Boreal and Sub-Boreal zone. However, there are definite peculiarities of biological and biogeochemical cycles in the individual ecosystems. We will consider the Spruce Forest ecosystem of the Karelia region, Russia. These ecosystems occur in the wide area of the Karelia, south from 63° N. 

Table 7. The statistics of heavy metal contents in the major plant species of Spruce Forest ecosystems of Boreal zone, Karelia, Russia (after Dobrovolsky, 1994).

BIOGEOCHEMICAL FLUXES AND EXPOSURE PATHWAYS IN SOIL-WATER SYSTEM OF BOREAL AND SUB-BOREAL ZONES... 

Figure 1.6 The net annual increment and fellings for temperate and boreal zone forested countries.

Table 28 Quinolizidine alkaloid frequencies in plant populations of Fabaceae in the boreal zone during 1999-2003...

Activity Tropical regions Temperate and boreal zones Globe... 

The statistical estimation of trace metal concentrations in the Spruce Forest ecosystems of the Boreal zone is the subject of wide variation, with coefficient of variation from 36 to 330%. However, we can note a clear trend in biogeochemical peculiarities of trace metal uptakes by dominant plant species. 

The Broad-leaved Forest ecosystems are widespread in regions of the Sub-Boreal zone with a well balanced precipitation evapotranspirationratio. The southern periphery of the vast belt of Eurasian boreal and Sub-Boreal Forest ecosystems is represented by Oak Forest ecosystems. These ecosystems exhibit both the largest biomass and... 

We will consider both Steppe and Desert ecosystems as deficient in atmospheric humidity (evapotranspiration exceeds precipitation). The Sub-Boreal, Semi-arid and Arid Steppe and Desert ecosystems occupy a significant part of the global area. This territory includes Sub-Boreal zones (Steppe, Arid Steppe, and Desert Steppe ecosystems) with total area of 9.23 x 10 km, as well as subtropical zones (Shrub Steppe and Desert Steppe ecosystems) with total area of 7.04 x 10 km. These areas do not include Subtropical and Tropical Sandy Desert ecosystems (5.77 x 10 km-) and Stony Desert ecosystems (8.96 x 10 km ). Thus the extra-tropical arid area takes about 20% of the World s terrestrial ecosystems. Most of this area goes to the inter-continental regions of Eurasia and, partly, of North and South America. The biogeochemistry of semi-arid and arid ecosystems shows distinctive parameters, which allow us to consider the quantitative features of element turnover and dynamics in natural fluxes. 

Discuss the net primary productivity of Forest ecosystems in Boreal and Sub-Boreal zones. Explain the similarities and differences in distribution of NPP values between various compartments of biomass in Coniferous, Deciduous and Mixed Forest ecosystems. 

TABLE 1 Coiiiparisoiis of Carbon Pools in Arctic-Alpine Tundra, in the Neighboring Boreal Zone, and the World s Total. 

Evaporation in the Boreal Zone During Summer—Physics... 

Precipitation or water supply is fundamental to terrestrial ecosystem evaporation. In the boreal zone, it is relatively sparse. Precipitation cannot generally be exceeded by evaporation in the long term. Ground water collection areas are exceptional in that water... 

TABLE 1 Latitudinal Transects of Climate Data from Miiller (1982) for the Boreal Zone ... 

TABLE 2 Boreal Zone Regional Soil Water Storage Capacities for 1° Latitude by 1° Longitude Grid Cells Based on the Global Soil Texture Database of Zobler (1986) with Hydraulic Parameter Values from Cosby etal. (1984)... 

Related to this limited water storage capacity of soils in the boreal zone is the climatological feature, especially in Siberia, of an abrupt transition from frozen winter to warm summer. Snow melt thus occurs relatively quickly and it involves relatively large... 

Summer days in the boreal zone are long, the daily period of illumination increasing virtually to 24 h in the north. Radiation is a primary driving variable of earth surface-atmosphere energy exchange including evaporation. On a clear day, for an unpolluted atmosphere, shortwave irradiance at the earth s surface obtains a maximum of around 70-80% of the extraterrestrial value due to... 

TABLE 3 Average Rates of Precipitation (P) and Evaporation ( ) and the Ratio of E and the Equilibrium Evaporation Rate ( / eq) during Summer from Boreal Zone Vegetation... 

Boreal zone forest stands are also part of a patchy landscape at least in terms of tree age, size, and density, which determine stand structure. More commonly, though, the stands of trees are interspersed with herbaceous and shrubby vegetation and wetlands. On average, P is found to be 0.5 mm day less than ( = 2.3 mm day ) for forests in summer. Rainfall interception has been included in this comparison because E comprised wet and dry canopy evaporation rates except for the Yakutsk study by Kelliher et al. (1997). The difference between rainfall and evaporation rates is up to 2 mm day for the two oldest studies. These studies also report by far the highest evaporation rates. These E measurements were made using the Bowen ratio technique, which is notoriously difficult to employ over forests because of the small gradients in temperature and humidity there. Except for Lalleur (1992), who also used this technique, the other measurements were made directly by eddy covariance. 

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