FAUNA AND FLORA O F MANGROVE SWAMPS
121
roots of Rhizophora associated with the animals characteristic of the
midlittoral flats and pools. The trees in this " Mangrove Park )' may
go for weeks on end without the surface of the soil drying out.
On the seaward side the pioneer is Aegialitis annulata which elsewhere in Queensland grows as a sprawling shrub in the landward fringe.
H. Mangrove soils
Mangroves live in a habitat characterized by a high salt content and
a high water content. The soils have a low oxygen content and abundant
hydrogen sulphide. They are fine grained soils, often semi-fluid and
ill consolidated, and in parts with abundant humus-mangrove peat, a
fibrous soil composed largely of the remains of roots and other woody
structures.
Anderson (unpublished information) has sampled the soils in two
transects across the mangal from the seaward fringe into the peat forest
in Sarawak. The locality is on the Maludam-Triso peninsula, a belt of
almost featureless forest lying between the estuaries of the Batang
Lupar and the B. Saribas in central Sarawak. The soils here within the
mangal are greenish-grey silty clays of apparently marine or estuarine
origin. Soluble salts seem to be leached out by rain water and replaced
by the tides. At higher levels in the mangal the clays are mined and
mixed thoroughly by the mud lobster, Thalassina anornula, and thrown
into mounds reaching 3 m high. I n the nypa zones of the mangal these
clays come to be covered by peat soils. There is a marked and abrupt
change in conductivity (a measure related to salinity), in pH and in loss
of weight on ignition at the interphase where the zone dominated by
mangrove trees passes over to the zone dominated by Nypa. The
estuarine or marine clays of the seaward avicennia fringe have an
average conductivity of between 5 000 and 8 000 p mhos, a pH of
more than 7 , and a loss of weight on ignition of between 5 and 15%.
Similar figures prevail through the rhizophora forests. On the other
hand, the muck soils of the nypa zone show a low conductivity,
0-1 000 p mhos hence a low salinity, a pH falling gradually to the acid
Ievel of peat forests and a loss of weight on ignition of up to 80 and
90%. I n the peat forest soils this loss of weight is more than 95%.
The mangrove soils are young soils for the most part, and have been
well sorted before deposition. The silt brought in from the sea by the
rising tide will contain shells of foraminiferans and debris from molluscan
and other shells. This calcareous material, together with the brokendown shells of molluscs which live within the mangrove and its mud,
forms a most important constituent of mangrove mud, and of other
intertidal muds. Much of the calcareous material of molluscan shells is
121
roots of Rhizophora associated with the animals characteristic of the
midlittoral flats and pools. The trees in this " Mangrove Park )' may
go for weeks on end without the surface of the soil drying out.
On the seaward side the pioneer is Aegialitis annulata which elsewhere in Queensland grows as a sprawling shrub in the landward fringe.
H. Mangrove soils
Mangroves live in a habitat characterized by a high salt content and
a high water content. The soils have a low oxygen content and abundant
hydrogen sulphide. They are fine grained soils, often semi-fluid and
ill consolidated, and in parts with abundant humus-mangrove peat, a
fibrous soil composed largely of the remains of roots and other woody
structures.
Anderson (unpublished information) has sampled the soils in two
transects across the mangal from the seaward fringe into the peat forest
in Sarawak. The locality is on the Maludam-Triso peninsula, a belt of
almost featureless forest lying between the estuaries of the Batang
Lupar and the B. Saribas in central Sarawak. The soils here within the
mangal are greenish-grey silty clays of apparently marine or estuarine
origin. Soluble salts seem to be leached out by rain water and replaced
by the tides. At higher levels in the mangal the clays are mined and
mixed thoroughly by the mud lobster, Thalassina anornula, and thrown
into mounds reaching 3 m high. I n the nypa zones of the mangal these
clays come to be covered by peat soils. There is a marked and abrupt
change in conductivity (a measure related to salinity), in pH and in loss
of weight on ignition at the interphase where the zone dominated by
mangrove trees passes over to the zone dominated by Nypa. The
estuarine or marine clays of the seaward avicennia fringe have an
average conductivity of between 5 000 and 8 000 p mhos, a pH of
more than 7 , and a loss of weight on ignition of between 5 and 15%.
Similar figures prevail through the rhizophora forests. On the other
hand, the muck soils of the nypa zone show a low conductivity,
0-1 000 p mhos hence a low salinity, a pH falling gradually to the acid
Ievel of peat forests and a loss of weight on ignition of up to 80 and
90%. I n the peat forest soils this loss of weight is more than 95%.
The mangrove soils are young soils for the most part, and have been
well sorted before deposition. The silt brought in from the sea by the
rising tide will contain shells of foraminiferans and debris from molluscan
and other shells. This calcareous material, together with the brokendown shells of molluscs which live within the mangrove and its mud,
forms a most important constituent of mangrove mud, and of other
intertidal muds. Much of the calcareous material of molluscan shells is