QPANTITATIVE ECOLOGY A N D WOODLAND ECOSYSTEM
107
B. TERMINOLOGY
Before discussing woodland ecosystem processes, it seems desirable
t o clarify the meaning of certain terms as used in this account for, in the
past they have been given different meanings which have resulted in
some misunderstanding. In this text, primary production refers solely
t o the production by the green plants, net primary production (apparent
assimilation) being the total amount of organic matter synthesized by
the plants as a result of photosynthesis and mineral absorption over a
specified time, usually a year. Gross primary production includes net
primary production plus the photosynthate used in respiration by the
green plants. Biomass refers t o the total quantity of organic matter
present in the ecosystem at a stated time and may relate to particular
organisms or groups of organisms. The term standing crop has been
avoided since the forest crop can be extremely varied for it is not always
restricted t o timber but may also include items such as decorative
foliage, Christmas trees, game, fruiting bodies of fungi and water.
Unless otherwise stated all weights are given on an oven-dry basis.
111. ORGANIC MATTER DYNAMICS
One of the most obvious, yet frequently overlooked features of
mature woodland ecosystems is that compared with other types of
ecosystems they contain a relatively large mass of organic matter. The
amount present is subject t o change, reflecting the overall balance
between organic matter production, harvesting and breakdown. Since
energy flow, and mineral and water circulation are all closely linked t o
the organic system it seems appropriate to consider it first.
A. LACK O F WEIGHT DATA
Unfortunately, forestry, unlike agriculture, does not have a long
history of crop weight recording, so there is no mass of detailed routine
weight data for woodland ecosystems from which t o show broad
differences in weight on a geographical scale and to give a general
indication of the magnitude of organic matter production. There are
several reasons for this, the main one being that the value of a forest
fitand is normally assessed from estimates of the marketable volume of
wood in the tree trunks. Wood-volume figures can be converted t o dry
weights since the specific gravities of different woods are known, but
the results of such conversions have only a limited application to
ecosystem studies became not all, or even complete, tree trunks are
harvested. Further complications arise in that trees are harvested
selectively over many years and tree boles form only part of the organic
matter produced in woodland ecosystems. Not unnaturally most re-
107
B. TERMINOLOGY
Before discussing woodland ecosystem processes, it seems desirable
t o clarify the meaning of certain terms as used in this account for, in the
past they have been given different meanings which have resulted in
some misunderstanding. In this text, primary production refers solely
t o the production by the green plants, net primary production (apparent
assimilation) being the total amount of organic matter synthesized by
the plants as a result of photosynthesis and mineral absorption over a
specified time, usually a year. Gross primary production includes net
primary production plus the photosynthate used in respiration by the
green plants. Biomass refers t o the total quantity of organic matter
present in the ecosystem at a stated time and may relate to particular
organisms or groups of organisms. The term standing crop has been
avoided since the forest crop can be extremely varied for it is not always
restricted t o timber but may also include items such as decorative
foliage, Christmas trees, game, fruiting bodies of fungi and water.
Unless otherwise stated all weights are given on an oven-dry basis.
111. ORGANIC MATTER DYNAMICS
One of the most obvious, yet frequently overlooked features of
mature woodland ecosystems is that compared with other types of
ecosystems they contain a relatively large mass of organic matter. The
amount present is subject t o change, reflecting the overall balance
between organic matter production, harvesting and breakdown. Since
energy flow, and mineral and water circulation are all closely linked t o
the organic system it seems appropriate to consider it first.
A. LACK O F WEIGHT DATA
Unfortunately, forestry, unlike agriculture, does not have a long
history of crop weight recording, so there is no mass of detailed routine
weight data for woodland ecosystems from which t o show broad
differences in weight on a geographical scale and to give a general
indication of the magnitude of organic matter production. There are
several reasons for this, the main one being that the value of a forest
fitand is normally assessed from estimates of the marketable volume of
wood in the tree trunks. Wood-volume figures can be converted t o dry
weights since the specific gravities of different woods are known, but
the results of such conversions have only a limited application to
ecosystem studies became not all, or even complete, tree trunks are
harvested. Further complications arise in that trees are harvested
selectively over many years and tree boles form only part of the organic
matter produced in woodland ecosystems. Not unnaturally most re-