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plant tissues which may then be consumed at higher trophic levels (such as by an
aphid that is a pest on food crops; which may then be consumed by a lacewing
insect larvae that is a predator and control on insect pests; which may then be consumed by a bird). Energy flow is often described as “one-way”—as opposed to
cyclical nutrient recapture—because energy either changes form or is converted to
heat such that it is not re-consumed by its previous consumers.
Energy flow and storage efficiency in an ecosystem depends on the living organisms and other components that are present; only a fraction of the energy stored at
one trophic level is typically transferred to the next higher level. For example,
organisms such as birds and mammals are inefficient relative to insects at storing
energy, because they must spend much of the energy they consume on maintaining
their body temperature. This principle can be utilized to increase human food supply sustainability, for example, by substituting insect protein for other animal
protein.
The flow of energy into living tissues that then die and decompose can concentrate the release of energy into the decomposition process itself—or into energy
stored as fossil fuels formed through geologic pressure exerted on decaying plant
and animal matter.
9.2.2 Land and Soil
9.2.2.1 Formation and Weathering Processes
Soil is a layer of relatively loose minerals that have been weathered from the earth’s
crust and have undergone a variety of other physical, chemical and biological processes over a period of time making them suitable to support plant growth.
Geological variations across the earth’s crust contribute to different chemical composition in the associated soil that is formed through surficial processes such as the
hydrologic cycle, erosion, and sedimentation. Weathering of rock via either
mechanical or chemical processes results in the loosening or transformation of
materials that may then be eroded, transported, and deposited in other locations and
in other forms, and may make raw minerals available for use by organisms—these
are the parent materials from which soils are then formed through biological and
other processes.
Soil texture is important to an understanding of the agricultural potential of land,
and a region’s human and animal carrying capacity. Typically described by the
relative amounts of sand, silt, and clay particles, soil texture originates from the
rock the soil develops from. For example, granite contains sand-sized particles of
quartz—which do not readily weather—and feldspar which weathers into finegrained clay particles. The resulting clays are significant for supporting life because
their layer-like structure with many negatively charged anionic adsorption sites provides a structure that can retain essential cations of calcium, magnesium, potassium,
9 Ecosystems and Ecosystem Services
plant tissues which may then be consumed at higher trophic levels (such as by an
aphid that is a pest on food crops; which may then be consumed by a lacewing
insect larvae that is a predator and control on insect pests; which may then be consumed by a bird). Energy flow is often described as “one-way”—as opposed to
cyclical nutrient recapture—because energy either changes form or is converted to
heat such that it is not re-consumed by its previous consumers.
Energy flow and storage efficiency in an ecosystem depends on the living organisms and other components that are present; only a fraction of the energy stored at
one trophic level is typically transferred to the next higher level. For example,
organisms such as birds and mammals are inefficient relative to insects at storing
energy, because they must spend much of the energy they consume on maintaining
their body temperature. This principle can be utilized to increase human food supply sustainability, for example, by substituting insect protein for other animal
protein.
The flow of energy into living tissues that then die and decompose can concentrate the release of energy into the decomposition process itself—or into energy
stored as fossil fuels formed through geologic pressure exerted on decaying plant
and animal matter.
9.2.2 Land and Soil
9.2.2.1 Formation and Weathering Processes
Soil is a layer of relatively loose minerals that have been weathered from the earth’s
crust and have undergone a variety of other physical, chemical and biological processes over a period of time making them suitable to support plant growth.
Geological variations across the earth’s crust contribute to different chemical composition in the associated soil that is formed through surficial processes such as the
hydrologic cycle, erosion, and sedimentation. Weathering of rock via either
mechanical or chemical processes results in the loosening or transformation of
materials that may then be eroded, transported, and deposited in other locations and
in other forms, and may make raw minerals available for use by organisms—these
are the parent materials from which soils are then formed through biological and
other processes.
Soil texture is important to an understanding of the agricultural potential of land,
and a region’s human and animal carrying capacity. Typically described by the
relative amounts of sand, silt, and clay particles, soil texture originates from the
rock the soil develops from. For example, granite contains sand-sized particles of
quartz—which do not readily weather—and feldspar which weathers into finegrained clay particles. The resulting clays are significant for supporting life because
their layer-like structure with many negatively charged anionic adsorption sites provides a structure that can retain essential cations of calcium, magnesium, potassium,
9 Ecosystems and Ecosystem Services