Precipitation, boreal zone

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. 

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 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... 

However, sulphur-deficient ecosystems are not significant in temperate forests and boreal zones and hence, with respect to sulphates, acid precipitation is no advantage. Inputs of 5 kg/ha/yr appear sufficient to satisfy S requirements in most forest ecosystems. Inputs of S in acid precipitation-affected regions frequently exceed this value. 

The cUmate is one of the most important natural factors. It is commonly defined as the weather averaged over a longer period of time and described by temperature, precipitation, wind, humidity, atmospheric pressure, and other variables. It determines the length of the growing season and hence the agricultural crops and tree species that can be cultivated as well as the number of harvests per year. The cUmate of a certain region is affected by its latitude, altitude, terrain, snow, and ice cover as well as nearby water bodies and their currents. Machinery and management methods have to be adapted to the cUmate. Especially forest machinery has to be able to operate in extreme cold conditions of the harsh winters of the boreal cUmate zone. 

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