Ecoinformatics and Soil-Plant Formations - New Ecoinformatics Tools in Environmental Science: Applications and Decision-making - page 673

and the initial condition:

0

xð z g ; t 0 Þ ¼ x ð z Þ;

where W(t) is precipitation intensity, L(t) is the intensity of evaporation off the soil
surface,

ρ is water density, ρ S is the volume density of soil, ʦ is the relative soil

moisture, ˕ ʠ B is the total water capacity of soil; V is the rate of moisture motion in

soil, ʼ = n ˕ ʠ B /( ρ g), m=1+2n, n is a constant, g is a gravity acceleration,

n ,

/ P B ¼ / S x ˕ S is the water potential of soil, K ʠ B is the conductivity corre-

sponding to soil moisture ʦ ʠ B , z is the vertical coordinate. The f function describes

the intensity of water absorption by the root system:

dS = dz ;

f ð z ; t Þ ¼ n 0 /uð z ; t Þþ v ð t Þ

where t Þu S ð t Þ is the deviation of the dimensionless water poten-

tial from the average value for the root layer of the soil,

uð z ; t Þ ¼ u S ð z ;

ʾ 0 = ʾ k ˃ 0 is the conductivity

of the entry of water to the root system, ʾ k =1/r k is the speci c conductivity of the

entry of water to the root, r k is the speci c resistance of the entry of water to the root,

˃ 0 is the total area of the sucking roots of the tree per unit soil area

n

u S ð t Þ ¼ 1 þ / S . /;

xð z ; t Þ

u S ð z ;

t Þ ¼ 1

;

x

where u S is an average dimensionless water potential for the root layer of the soil,

v ¼ n 0 / S / 0

is the rate of water absorption by roots from the soil.
Water from the root system moves upward along the trunk, through branches
into leaves and evaporates into the atmosphere. It is assumed that an amount of the
moisture from respiration is equal to that assimilated by the root system, and the
rate of motion is equal to v. The integral effect of the impact of the coniferous forest
on water cycle in its territory is the sum of the effects of each tree. The practical
application of the developed model requires information about spatial heteroge-
neities and distributions of the characteristics of the forest stand. An application of
the model to deciduous and mixed forest systems requires additional units which
would describe the processes of the transformation of water potentials as well as
carbon cycle in leaves. Intensive studies are being carried out in this direction.

8.3.9 Modeling Succession Processes in the Tundra-Taiga
System

Predicting the northern boundary of forests has become problematical as a conse-
quence of worldwide anthropogenic processes and the way in which their effects are
inexorably propagating towards northern latitudes. Connections between the