QUANTITATIVE ECOLOGY A N D WOODLAND ECOSYSTEM
117
material overlying the mineral soil, since the microflora cannot be
separated easily. Hafler (1937) collected fruiting bodies of fungi in
beech-oak forests and found a wide range of weights, up t o 0.18 x lo3
kg per ha. Russell (1956) estimates the oven-dry weight of bacteria and
fungi in Rothamsted arable soil t o be approximately 0-34-0-78 and
0.34 x 103 kg per ha respectively.
Relatively few records of root weights are available for forest ecosystems and although the published data give similar values on the
whole, experience in root sampling indicates that these may be seriously
in error for it is difficult t o ensure that all roots are collected and no
mineral soil is incorporated within the root mass. Frequently, the
weight of the root system exceeds that of the tree canopy. Significant
amounts of organic matter are present in the mineral soil but since it is
difficult to distinguish between that due t o plant roots and that due
to other organic matter - e.g. leaves, etc. incorporated from the
litter, or material such as fungal spores (Burges, 1950), pollen grains
(Dimbleby, 1961) and the soil fauna-no
figures other than root
weights are given for the organic matter in the mineral soil.
The proportionate distribution of plant organic matter within woodland ecosystems is influenced by numerous factors such as the species
of trees present and intensity of forest management, and consequently
varies greatly. I n the middle-aged, well-grown woodlands listed in Table
I about 75% of the total plant biomass is contained within the living
trees, the amount in the tree trunks exceeding that of the roots and
canopy.
If the weights of the different types of plant matter are added together for the individual woodlands of Table I and appropriate adjustments made for missing components, it is noteworthy that the total
oven-dry weights of the plant biomass in the better grown, close
canopied stands is about 300 to 350 x lo3 kg per ha. Ogawa et al. (1961)
have made some tentative calculations of plant biomass for two luxuriant forests of tropical Africa described by Aubrkville (1938) and Jones
(1956) and obtained weights of 200 and 227 x lo3 kg per ha exclusive
of roots. They suggest that throughout different latitudes the plant
mass in well-grown forests is fairly uniform in dry weight ranging between 200 and 350 x lo3 kg per ha irrespective of climatic zone. However, this apparent "uniformity" of dry weight may be fortuitous,
resulting from the limited number of woodlands sampled and certainly
the sequence of forest types observed in passing northwards through
Scandinavia for example, gives the impression of a progressive decrease
in plant biomass. Their estimates of plant biomass weight for tropical
forests may be low since Greenland and Kowal (1960) found the total
weight of the vegetation cover in a disturbed moist tropical forest in
117
material overlying the mineral soil, since the microflora cannot be
separated easily. Hafler (1937) collected fruiting bodies of fungi in
beech-oak forests and found a wide range of weights, up t o 0.18 x lo3
kg per ha. Russell (1956) estimates the oven-dry weight of bacteria and
fungi in Rothamsted arable soil t o be approximately 0-34-0-78 and
0.34 x 103 kg per ha respectively.
Relatively few records of root weights are available for forest ecosystems and although the published data give similar values on the
whole, experience in root sampling indicates that these may be seriously
in error for it is difficult t o ensure that all roots are collected and no
mineral soil is incorporated within the root mass. Frequently, the
weight of the root system exceeds that of the tree canopy. Significant
amounts of organic matter are present in the mineral soil but since it is
difficult to distinguish between that due t o plant roots and that due
to other organic matter - e.g. leaves, etc. incorporated from the
litter, or material such as fungal spores (Burges, 1950), pollen grains
(Dimbleby, 1961) and the soil fauna-no
figures other than root
weights are given for the organic matter in the mineral soil.
The proportionate distribution of plant organic matter within woodland ecosystems is influenced by numerous factors such as the species
of trees present and intensity of forest management, and consequently
varies greatly. I n the middle-aged, well-grown woodlands listed in Table
I about 75% of the total plant biomass is contained within the living
trees, the amount in the tree trunks exceeding that of the roots and
canopy.
If the weights of the different types of plant matter are added together for the individual woodlands of Table I and appropriate adjustments made for missing components, it is noteworthy that the total
oven-dry weights of the plant biomass in the better grown, close
canopied stands is about 300 to 350 x lo3 kg per ha. Ogawa et al. (1961)
have made some tentative calculations of plant biomass for two luxuriant forests of tropical Africa described by Aubrkville (1938) and Jones
(1956) and obtained weights of 200 and 227 x lo3 kg per ha exclusive
of roots. They suggest that throughout different latitudes the plant
mass in well-grown forests is fairly uniform in dry weight ranging between 200 and 350 x lo3 kg per ha irrespective of climatic zone. However, this apparent "uniformity" of dry weight may be fortuitous,
resulting from the limited number of woodlands sampled and certainly
the sequence of forest types observed in passing northwards through
Scandinavia for example, gives the impression of a progressive decrease
in plant biomass. Their estimates of plant biomass weight for tropical
forests may be low since Greenland and Kowal (1960) found the total
weight of the vegetation cover in a disturbed moist tropical forest in