QUANTITATIVE
ECOLOGY AND WOODLAND ECOSYSTEM
135
favourable soil conditions so that in the long run any immediate effect
on tree growth is offset by deterioration of the site. Comprehensive
ecosystem studies are needed to elucidate the basic biological background of thinning and pruning.
Great advances in tree breeding have been made in the last quarter of
a century (Larsen, 1956) and undoubtedly plant breeders have an important role t o play in improving productivity. Biological productivity
can be increased by breeding new varieties or by careful selection within
existing woodlands t o obtain trees easy t o establish, capable of high
rates of photosynthesis, and resistant t o disease, drought and cold.
There is also considerable scope t o grow trees in which a greater proportion of the biological production is diverted to salable tree trunks,
i.e. t o economic production.
D. O R G A N I C MATTER T U R N O V E R
Only part of the organic matter produced by woodland plants is retained within the ecosystem, the rest being lost in various ways. Man,
for example, removes all kinds of forest produce and the intensity of
his harvesting varies enormously.
Organic matter is also removed from woodland ecosystems by natural
means, e.g. by plant roots growing beyond the recognized ecosystem
limits, by animal movement out of the ecosystem and by wind dispersal
of seeds, pollen and leaves. Little attention has been paid t o the natural
flow of organic matter into and out of woodland ecosystems and frequently it is assumed incorrectly that these are in balance and insignificant in quantity. Sjors (1954) made an intensive study of some Swedish
park meadows having about 25% of the area wooded and found that
the yearly fall of tree leaves in the woodland varied from 1.5 t o 2-5 x
lo3 kg per he. Depending on the size of the opening, the treeless areas
received 0.3 t o 0-8 x 103 kg of leaves per ha per annum from the woodland. In extreme cases, such as exposed savanna or narrow shelter belt
type woodlands, soon after leaf fall the woodland floor may be cleared
completely of tree leaves by the wind, if the understorey vegetation is
ineffective in trapping and retaining the annual leaf fall.
Normally, the greatest loss of organic matter results from decomposition within the ecosystem and this far exceeds that due t o harvesting (Fig. 4). Comminution of the primary woodland production begins
on the living plants and continues in the soil after litter fall. Litter fall
takes place throughout the year in both coniferous (Owen, 1954) and
deciduous (Miller and Hurst, 1957) woodlands. The breakdown of
organic material involves various agencies including the fauna, microflora and environmental factors such as frost and wind. Woodland ecologists have paid particular attention t o the complementary activities
ECOLOGY AND WOODLAND ECOSYSTEM
135
favourable soil conditions so that in the long run any immediate effect
on tree growth is offset by deterioration of the site. Comprehensive
ecosystem studies are needed to elucidate the basic biological background of thinning and pruning.
Great advances in tree breeding have been made in the last quarter of
a century (Larsen, 1956) and undoubtedly plant breeders have an important role t o play in improving productivity. Biological productivity
can be increased by breeding new varieties or by careful selection within
existing woodlands t o obtain trees easy t o establish, capable of high
rates of photosynthesis, and resistant t o disease, drought and cold.
There is also considerable scope t o grow trees in which a greater proportion of the biological production is diverted to salable tree trunks,
i.e. t o economic production.
D. O R G A N I C MATTER T U R N O V E R
Only part of the organic matter produced by woodland plants is retained within the ecosystem, the rest being lost in various ways. Man,
for example, removes all kinds of forest produce and the intensity of
his harvesting varies enormously.
Organic matter is also removed from woodland ecosystems by natural
means, e.g. by plant roots growing beyond the recognized ecosystem
limits, by animal movement out of the ecosystem and by wind dispersal
of seeds, pollen and leaves. Little attention has been paid t o the natural
flow of organic matter into and out of woodland ecosystems and frequently it is assumed incorrectly that these are in balance and insignificant in quantity. Sjors (1954) made an intensive study of some Swedish
park meadows having about 25% of the area wooded and found that
the yearly fall of tree leaves in the woodland varied from 1.5 t o 2-5 x
lo3 kg per he. Depending on the size of the opening, the treeless areas
received 0.3 t o 0-8 x 103 kg of leaves per ha per annum from the woodland. In extreme cases, such as exposed savanna or narrow shelter belt
type woodlands, soon after leaf fall the woodland floor may be cleared
completely of tree leaves by the wind, if the understorey vegetation is
ineffective in trapping and retaining the annual leaf fall.
Normally, the greatest loss of organic matter results from decomposition within the ecosystem and this far exceeds that due t o harvesting (Fig. 4). Comminution of the primary woodland production begins
on the living plants and continues in the soil after litter fall. Litter fall
takes place throughout the year in both coniferous (Owen, 1954) and
deciduous (Miller and Hurst, 1957) woodlands. The breakdown of
organic material involves various agencies including the fauna, microflora and environmental factors such as frost and wind. Woodland ecologists have paid particular attention t o the complementary activities