Introduction
in turn, may alter components of the continuum; for example, herbivores
that eat leaves, mites that alter stomatal fimction, or a disease that inhibits
photosynthesis.
Energy or mass from one part or scale of this system can flow continuously into another part or scale and the consequence of this interaction
is what is studied in "environmental biophysics." Water is pervasive
throughout the biosphere, existing in solid, liquid, or gas states, and
able to move from one place or state to another. Living organisms depend on water and have adapted in remarkable ways to its characteristics.
Consider, for a moment, the flow of water in the soil-plant-atmosphere
system. Rainfall impinges on the surface of the soil, after condensing
from the vapor in the air, and infiltrates through the pores in response
to water potential gradients to distribute water throughout the bulk soil.
Water then moves through the soil, into the root, through the vascular
system of a plant and into the leaf under the influence of a continuously
decreasing water potential. At the leaf, liquid water is changed to water
vapor, which requires a considerable amount of latent heat, and the water vapor moves in response to vapor pressure differences between the
leaf and the atmosphere rather then water potential gradients. This water vapor diffuses through the stomatal pore and still-air boundary layer
near the leaf surface and is carried by turbulent convection through the
canopy space, the planetary boundary layer, and ultimately to the free
atmosphere to be distributed around the globe and condensed again as
rain. The energy required to change the liquid water in leaves to water
vapor, which may be extracted from the air or provided by radiant energy
from the sun, couples energy exchange to water exchange. The transport
laws can be used in conjunction with conservation of mass and energy
to describe the movement of water throughout this system. Even though
the driving forces for movement of water may vary for different parts of
the system, appropriate conductances can be defined to describe transport
throughout the system. In some cases the form of the transport equation
may vary for different parts of the system, but the conservation of mass
principle is used to link transport equations for these various parts of the
system together.
Clearly, the biosphere is a complex continuum, not only in terms of the
reality of the interconnectedness of living things and their environments,
but also in terms of the mathematical and physical formulations that
biophysicists use to describe this remarkable system. Rational exploration
of the biosphere is just beginning and it is our hope that this new "head"
knowledge will be woven into your being in such a way that you will
have an increased awareness of your dependence on and implicit faith in
that which is not known, as well as having some simple quantitative tools
at your disposal to enhance a harmonious relationship between yourself
and your environment and serve others at the same time.
A schematic representation of the connectivity of energy and mass in
the biosphere is illustrated in Fig. 1.1.
in turn, may alter components of the continuum; for example, herbivores
that eat leaves, mites that alter stomatal fimction, or a disease that inhibits
photosynthesis.
Energy or mass from one part or scale of this system can flow continuously into another part or scale and the consequence of this interaction
is what is studied in "environmental biophysics." Water is pervasive
throughout the biosphere, existing in solid, liquid, or gas states, and
able to move from one place or state to another. Living organisms depend on water and have adapted in remarkable ways to its characteristics.
Consider, for a moment, the flow of water in the soil-plant-atmosphere
system. Rainfall impinges on the surface of the soil, after condensing
from the vapor in the air, and infiltrates through the pores in response
to water potential gradients to distribute water throughout the bulk soil.
Water then moves through the soil, into the root, through the vascular
system of a plant and into the leaf under the influence of a continuously
decreasing water potential. At the leaf, liquid water is changed to water
vapor, which requires a considerable amount of latent heat, and the water vapor moves in response to vapor pressure differences between the
leaf and the atmosphere rather then water potential gradients. This water vapor diffuses through the stomatal pore and still-air boundary layer
near the leaf surface and is carried by turbulent convection through the
canopy space, the planetary boundary layer, and ultimately to the free
atmosphere to be distributed around the globe and condensed again as
rain. The energy required to change the liquid water in leaves to water
vapor, which may be extracted from the air or provided by radiant energy
from the sun, couples energy exchange to water exchange. The transport
laws can be used in conjunction with conservation of mass and energy
to describe the movement of water throughout this system. Even though
the driving forces for movement of water may vary for different parts of
the system, appropriate conductances can be defined to describe transport
throughout the system. In some cases the form of the transport equation
may vary for different parts of the system, but the conservation of mass
principle is used to link transport equations for these various parts of the
system together.
Clearly, the biosphere is a complex continuum, not only in terms of the
reality of the interconnectedness of living things and their environments,
but also in terms of the mathematical and physical formulations that
biophysicists use to describe this remarkable system. Rational exploration
of the biosphere is just beginning and it is our hope that this new "head"
knowledge will be woven into your being in such a way that you will
have an increased awareness of your dependence on and implicit faith in
that which is not known, as well as having some simple quantitative tools
at your disposal to enhance a harmonious relationship between yourself
and your environment and serve others at the same time.
A schematic representation of the connectivity of energy and mass in
the biosphere is illustrated in Fig. 1.1.