QUANTITATIVE ECOLOGY A N D WOODLAND ECOSYSTEM
181
nutrients in Finland, which is largely forest covered, from data of the
chemical composition and flow of river water. He found that run-off
resulted in an annual loss of 4 kg per ha of K, 12 of Ca, 4 of Mg, 0-25
of P and 2 of N, in the case of the four mineral elements this exceeded
input as precipitation by 2, 10, 3 and 0.17 kg per ha respectively, but
twice as much nitrogen was supplied in the rain-water as was lost in the
drainage water. Some nutrients in river water are derived from agricultural areas and from the underlying rock so that the loss of nutrient
from forest ecosystems may be less than Viro’s figures suggest. Miller
(in manuscript) calculates that, in stands of Nothofagus truncata in
New Zealand, leaching losses amount to about 30 kg per ha for Ca,
15 each for Mg and K and very little for phosphorus and nitrogen.
Forest fires may cause a large loss of nutrients from the ecosystem
since volatile elements are released into the atmosphere and the
mineral elements remaining in the ash may be washed out fairly
rapidly (Burns, 1952) or dispersed by wind erosion. Under normal conditions the loss of nutrients through erosion tends to be negligible in
wooded areas because of the blanketing effect of the vegetation and the
litter. Serious erosion may occur at, certain stages, e.g. at the time of
harvesting because of soil disturbance due to the skidding out of logs
or because of badly-located extraction roads.
G . L O N G - T E R M B A L A N C E
It is impossible to generalize on long-term trends in the nutrient
budget, since so many diverse processes are concerned in the circulation
of chemical elements in woodland ecosystems, and all of these vary
according to the character of the ecosystem, the particular element
concerned and the influence of man. There may be no long-term
balance of the nutrient capital even in natural woodlands. It does
appear that the ecosystem capital for some essential nutrients, e.g.
calcium, may be seriously depleted by intensive forestry so that high
levels of production can only be maintained if sylviculturalists add
nutrients to the system, as is done in agriculture. Much would be gained
by bringing together the present fragmentary research on nutrient
circulation in order to understand more fully the dynamic interrelationships of its many facets.
VII. CONCLUSIONS
One purpose of this essay is to stress the fundamental unity of
ecosystem physiology, yet paradoxically, for convenience of description, the four processes described have had to be considered separately.
No such distinction occurs in nature and many interrelationships exist,
some of these were mentioned in passing, but the interconnections are
181
nutrients in Finland, which is largely forest covered, from data of the
chemical composition and flow of river water. He found that run-off
resulted in an annual loss of 4 kg per ha of K, 12 of Ca, 4 of Mg, 0-25
of P and 2 of N, in the case of the four mineral elements this exceeded
input as precipitation by 2, 10, 3 and 0.17 kg per ha respectively, but
twice as much nitrogen was supplied in the rain-water as was lost in the
drainage water. Some nutrients in river water are derived from agricultural areas and from the underlying rock so that the loss of nutrient
from forest ecosystems may be less than Viro’s figures suggest. Miller
(in manuscript) calculates that, in stands of Nothofagus truncata in
New Zealand, leaching losses amount to about 30 kg per ha for Ca,
15 each for Mg and K and very little for phosphorus and nitrogen.
Forest fires may cause a large loss of nutrients from the ecosystem
since volatile elements are released into the atmosphere and the
mineral elements remaining in the ash may be washed out fairly
rapidly (Burns, 1952) or dispersed by wind erosion. Under normal conditions the loss of nutrients through erosion tends to be negligible in
wooded areas because of the blanketing effect of the vegetation and the
litter. Serious erosion may occur at, certain stages, e.g. at the time of
harvesting because of soil disturbance due to the skidding out of logs
or because of badly-located extraction roads.
G . L O N G - T E R M B A L A N C E
It is impossible to generalize on long-term trends in the nutrient
budget, since so many diverse processes are concerned in the circulation
of chemical elements in woodland ecosystems, and all of these vary
according to the character of the ecosystem, the particular element
concerned and the influence of man. There may be no long-term
balance of the nutrient capital even in natural woodlands. It does
appear that the ecosystem capital for some essential nutrients, e.g.
calcium, may be seriously depleted by intensive forestry so that high
levels of production can only be maintained if sylviculturalists add
nutrients to the system, as is done in agriculture. Much would be gained
by bringing together the present fragmentary research on nutrient
circulation in order to understand more fully the dynamic interrelationships of its many facets.
VII. CONCLUSIONS
One purpose of this essay is to stress the fundamental unity of
ecosystem physiology, yet paradoxically, for convenience of description, the four processes described have had to be considered separately.
No such distinction occurs in nature and many interrelationships exist,
some of these were mentioned in passing, but the interconnections are