QUANTITATIVE ECOLOGY A N D WOODLAND ECOSYSTEM
170
bearing root nodules so that Bond (1958) has suggested that alder be
used as a nurse crop on infertile land. However, nitrogen fixation may
be considerable in pure stands of coniferous tree species, such as spruce,
with no ground vegetation present. Tamm (1953) after studying the
nutrition of the woodland moss Hylocomium splendens concludes that
there may be a direct absorption of ammonia from the air and this may
account for part of the increase in nitrogen of tree leaves placed on the
forest floor by Gilbert and Bocock (1960).
On balance the nutrient capital of woodland ecosystems is probably
increased by animal movement, particularly where the woodlands occur
as small tracts within open country. Many birds roost in trees and their
droppings are scattered over the vegetation and forest floor. Ailing
animals may seek the shelter of woodlands where they die.
Appreciable amounts of nutrients may be added to forest ecosystems
by man, either within seedlings transplanted to the forest from nurseries or by the direct application of fertilizers. Artificial fertilizers may
be more generally applied in the future but at present their main use
is to assist the establishment of young plants on infertile soils or to improve the growth of young woodlands exhibiting serious nutrient deficiency symptoms. Numerous examples of improved growth of seedlings
or young trees following the application of fertilizers are given in a comprehensive bibliography compiled by White and Leaf (1956). Recently,
increased attention has been paid to the possibilities of applying fertilizers to middle-aged and older, close-canopied woodlands in order to
improve productivity and to reduce any soil degradation resulting from
raising fast-growing woodlands on poor soils. Various techniques, including aerial spreading (Holmes and Cousins, 1960) have been developed to give an economic and even application of fertilizers over
wooded areas.
The results obtained from applying nutrieiits to older woodlands vary
greatly, in most cases an increase in nutrient uptake, indicated by
foliar analysis, occurs, but this is not always accompanied by increased
production. Leibundgut and Richard (1957) in Switzerland found no
evidence of improved growth after applying various fertilizers to 45- to
70-year-old spruce growing on a rich, brown, forest soil. In Britain an
elaborate series of experiments in which K, Ca, Mg, P and N were
applied at various levels up to 250, 1570, 35, 135 and 200 kg per ha
respectively to pole stage crops of Sitka spruce, Scots pine and Douglas
fi for a range of site conditions has failed to give any growth response
by the trees during the first two years (personal communication from
G. D. Holmes, Forestry Commission). In contrast, Heilman (1961)
reports a marked effect of nitrogen supplied to natural Douglas fir
stands on poor sites, the maximum application of 740 kg of N per ha
’
170
bearing root nodules so that Bond (1958) has suggested that alder be
used as a nurse crop on infertile land. However, nitrogen fixation may
be considerable in pure stands of coniferous tree species, such as spruce,
with no ground vegetation present. Tamm (1953) after studying the
nutrition of the woodland moss Hylocomium splendens concludes that
there may be a direct absorption of ammonia from the air and this may
account for part of the increase in nitrogen of tree leaves placed on the
forest floor by Gilbert and Bocock (1960).
On balance the nutrient capital of woodland ecosystems is probably
increased by animal movement, particularly where the woodlands occur
as small tracts within open country. Many birds roost in trees and their
droppings are scattered over the vegetation and forest floor. Ailing
animals may seek the shelter of woodlands where they die.
Appreciable amounts of nutrients may be added to forest ecosystems
by man, either within seedlings transplanted to the forest from nurseries or by the direct application of fertilizers. Artificial fertilizers may
be more generally applied in the future but at present their main use
is to assist the establishment of young plants on infertile soils or to improve the growth of young woodlands exhibiting serious nutrient deficiency symptoms. Numerous examples of improved growth of seedlings
or young trees following the application of fertilizers are given in a comprehensive bibliography compiled by White and Leaf (1956). Recently,
increased attention has been paid to the possibilities of applying fertilizers to middle-aged and older, close-canopied woodlands in order to
improve productivity and to reduce any soil degradation resulting from
raising fast-growing woodlands on poor soils. Various techniques, including aerial spreading (Holmes and Cousins, 1960) have been developed to give an economic and even application of fertilizers over
wooded areas.
The results obtained from applying nutrieiits to older woodlands vary
greatly, in most cases an increase in nutrient uptake, indicated by
foliar analysis, occurs, but this is not always accompanied by increased
production. Leibundgut and Richard (1957) in Switzerland found no
evidence of improved growth after applying various fertilizers to 45- to
70-year-old spruce growing on a rich, brown, forest soil. In Britain an
elaborate series of experiments in which K, Ca, Mg, P and N were
applied at various levels up to 250, 1570, 35, 135 and 200 kg per ha
respectively to pole stage crops of Sitka spruce, Scots pine and Douglas
fi for a range of site conditions has failed to give any growth response
by the trees during the first two years (personal communication from
G. D. Holmes, Forestry Commission). In contrast, Heilman (1961)
reports a marked effect of nitrogen supplied to natural Douglas fir
stands on poor sites, the maximum application of 740 kg of N per ha
’