130
J. D. OVINQTON
meadow 2.4 and Cares meadow 3.4. Specht et al. (1958) in South
Australia have made intensive studies of the heath vegetation succession following fire and found that the annual biomass increment of
plant material, both roots and tops, was 3.2 x 103 kg per ha from 9 t o
25 years - primary production must exceed this. Odum (1960) has
determined net production in old abandoned fields in South Carolina,
U.S.A. ; in the first year after abandonment the invading flora produced
5 x lo3 kg of dry matter per ha, but in the following 6 years annual production decreased to about 3 x 103. Bray et al. (1959) give a range of
yearly organic-matter production for some terrestrial communities in
Minnesota of from 5 for Setaria glauca t o 46 for Typha although they
recognize that part of this organic matter was derived from previous
growing seasons. A coral-reef community on Eniwetok Atoll had the
large annual productivity of 81 x 103 kg per ha (Odum and Odum,
1955) but this may be regarded as semi-marine ; fairly high production
rates have been recorded for aquatic communities, e.g. Odum (1957)
gives an annual dry-weight production at Silver Springs in Florida of
65 x lo3 kg per ha.
Numerous data of the productivity of agricultural crops are available
but need cautious interpretation since they frequently refer only t o the
marketable plant parts. Production by weeds is frequently ignored.
Transeau (1926) for example has made an extremely detailed study of
production by maize in Wisconsin, U.S.A., preparing energy balancesheets for a field of maize with an annual net primary productivity of
15 x lo3 kg per ha but does not mention the productivity of the weed
flora. In the neighbouring state of Minnesota, maize produced 9 x lo3
and the associated weeds 1 x lo3 kg of dry matter per ha per annum on
rather poor farmland. On the better soils of the corn belt much greater
productivity is generally attained. Armstrong (1960) reports an an.nua1
cut, at probably the period of maximum biomass, of 6 x lo3 kg per ha
from rye grass at Hurley in England but gives no figures for root production. Russell (1956) has given the following dry weights, expressed
as lo3 kg per ha, for crop production commonly obtained on farms in
England, beans 3.9, meadow hay 3.2, red clover hay 4.2, oats 4.5,
wheat 4.7, turnips 5.2 and mangolds 8-5. The maximum yields on good
soils with adequate fertilizers and water would be expected to exceed
these values. Since Russell does not give any values for weed production
and the root mass is not included in these figures, they underestimate
the total net productivity, probably by as much as a half.
It is evident from the available records that, compared with other
terrestrial communities, woodlands are fairly efficient long-term producers of organic matter. Estimates by de Wit (1959) based on known
rates of photosynthesis and average measurements of incident solar
J. D. OVINQTON
meadow 2.4 and Cares meadow 3.4. Specht et al. (1958) in South
Australia have made intensive studies of the heath vegetation succession following fire and found that the annual biomass increment of
plant material, both roots and tops, was 3.2 x 103 kg per ha from 9 t o
25 years - primary production must exceed this. Odum (1960) has
determined net production in old abandoned fields in South Carolina,
U.S.A. ; in the first year after abandonment the invading flora produced
5 x lo3 kg of dry matter per ha, but in the following 6 years annual production decreased to about 3 x 103. Bray et al. (1959) give a range of
yearly organic-matter production for some terrestrial communities in
Minnesota of from 5 for Setaria glauca t o 46 for Typha although they
recognize that part of this organic matter was derived from previous
growing seasons. A coral-reef community on Eniwetok Atoll had the
large annual productivity of 81 x 103 kg per ha (Odum and Odum,
1955) but this may be regarded as semi-marine ; fairly high production
rates have been recorded for aquatic communities, e.g. Odum (1957)
gives an annual dry-weight production at Silver Springs in Florida of
65 x lo3 kg per ha.
Numerous data of the productivity of agricultural crops are available
but need cautious interpretation since they frequently refer only t o the
marketable plant parts. Production by weeds is frequently ignored.
Transeau (1926) for example has made an extremely detailed study of
production by maize in Wisconsin, U.S.A., preparing energy balancesheets for a field of maize with an annual net primary productivity of
15 x lo3 kg per ha but does not mention the productivity of the weed
flora. In the neighbouring state of Minnesota, maize produced 9 x lo3
and the associated weeds 1 x lo3 kg of dry matter per ha per annum on
rather poor farmland. On the better soils of the corn belt much greater
productivity is generally attained. Armstrong (1960) reports an an.nua1
cut, at probably the period of maximum biomass, of 6 x lo3 kg per ha
from rye grass at Hurley in England but gives no figures for root production. Russell (1956) has given the following dry weights, expressed
as lo3 kg per ha, for crop production commonly obtained on farms in
England, beans 3.9, meadow hay 3.2, red clover hay 4.2, oats 4.5,
wheat 4.7, turnips 5.2 and mangolds 8-5. The maximum yields on good
soils with adequate fertilizers and water would be expected to exceed
these values. Since Russell does not give any values for weed production
and the root mass is not included in these figures, they underestimate
the total net productivity, probably by as much as a half.
It is evident from the available records that, compared with other
terrestrial communities, woodlands are fairly efficient long-term producers of organic matter. Estimates by de Wit (1959) based on known
rates of photosynthesis and average measurements of incident solar