Q U A N T I T A T I V E ECOLOQY A N D W O O D L A N D E C O S Y S T E M
151
TABLE IX
Processes Changing the Capital of Chemical Elements
in Woodland Ecosystems
Increase of capital
~
Planting of seedling trees
Movement of animals into ecosystem
Collection of plant matter, e.g. leaves
Precipitation
Trapping of dust, aarosols etc.
Application of fertilizers
Soil and rock weathering
Fixation from atmosphere
Enlarging effective soil volume, e.g.
by draining and breaking up of
compact soil horizons
blown by wind
Decrease of capital
Harvesting of forest products
Movement of animals out of ecosyatem
Loss of plant matter, e.g. pollen, leaves
Run-off
Erosion of soil
Fire
Construction of drains to remove ex_
_
_
_
.
~
~
blown by wind
cess water
radioactive tracers. Radioactive phosphorus 32P injected into the base of
the trunk of a birch tree during sunny weather was well-distributed
throughout the tree crown within 28 hours. Part of the 3zP could be
washed out of the tree crowns or fall t o the ground in litter and be taken
up again by woodland plants within a period of days. Unpublished
results of J. P. Witherspoon show that when 2 mc of caesium-134 tracer
were introduced into the trunk of Quercus alba, after 165 days the
1s4Cs had become widely redistributed in the ecosystem. About 47 yo was
in the trunk, branches and large roots, 46% was in the tree leaves and
the remaining 7% had been removed from the trees either by rain,
animals or litter fall prior to the main leaf fall in autumn. Of the 7%
of 134Cs lost from the trees 5% was in the top 10 cm of soil, 0-8y0 was in
the small rootlets, and the remaining 1.2% was about equally distributed
between the understorey plants and litter with less than 0.1% in the
animals. The preceding figures do not include losses to insects, but
estimates based on leaf surface area consumed by insects suggest that
several per cent may have passed through the animal food chain. Some
of this would have been recovered in the litter, but a small fraction
might have been dispersed by animal movements. Elements such as
sodium and potassium are more mobile than caesium and probably short
cycles of this type are very important in their circulation. I n contrast,
the rate of movement through woodland ecosystems of part of the
chemical capital may be very slow, minerals incorporated in tree trunks
not being released for over a century.
Our knowledge of the circulation of trace elements is very incomplete.
151
TABLE IX
Processes Changing the Capital of Chemical Elements
in Woodland Ecosystems
Increase of capital
~
Planting of seedling trees
Movement of animals into ecosystem
Collection of plant matter, e.g. leaves
Precipitation
Trapping of dust, aarosols etc.
Application of fertilizers
Soil and rock weathering
Fixation from atmosphere
Enlarging effective soil volume, e.g.
by draining and breaking up of
compact soil horizons
blown by wind
Decrease of capital
Harvesting of forest products
Movement of animals out of ecosyatem
Loss of plant matter, e.g. pollen, leaves
Run-off
Erosion of soil
Fire
Construction of drains to remove ex_
_
_
_
.
~
~
blown by wind
cess water
radioactive tracers. Radioactive phosphorus 32P injected into the base of
the trunk of a birch tree during sunny weather was well-distributed
throughout the tree crown within 28 hours. Part of the 3zP could be
washed out of the tree crowns or fall t o the ground in litter and be taken
up again by woodland plants within a period of days. Unpublished
results of J. P. Witherspoon show that when 2 mc of caesium-134 tracer
were introduced into the trunk of Quercus alba, after 165 days the
1s4Cs had become widely redistributed in the ecosystem. About 47 yo was
in the trunk, branches and large roots, 46% was in the tree leaves and
the remaining 7% had been removed from the trees either by rain,
animals or litter fall prior to the main leaf fall in autumn. Of the 7%
of 134Cs lost from the trees 5% was in the top 10 cm of soil, 0-8y0 was in
the small rootlets, and the remaining 1.2% was about equally distributed
between the understorey plants and litter with less than 0.1% in the
animals. The preceding figures do not include losses to insects, but
estimates based on leaf surface area consumed by insects suggest that
several per cent may have passed through the animal food chain. Some
of this would have been recovered in the litter, but a small fraction
might have been dispersed by animal movements. Elements such as
sodium and potassium are more mobile than caesium and probably short
cycles of this type are very important in their circulation. I n contrast,
the rate of movement through woodland ecosystems of part of the
chemical capital may be very slow, minerals incorporated in tree trunks
not being released for over a century.
Our knowledge of the circulation of trace elements is very incomplete.