46
M. E. D. P O O R E
woodland floor or the groupings of annuals and geophytes which may
be found in garrigue in the Mediterranean region. These are known as
synusiae. Cain and de Oliviera Castro (1959) define the synusia as “a
social aggregate consisting of one or a few closely related life forms
occurring together and having a similar ecology ... . The total complex
of synusiae that simultaneously occupy the same terrain is called a
phytocoenose ; this the usual concept of community”.
In comparing and classifying synusiae one is comparing groups of
ecologically closely related species growing in a habitat which is, for
them, approximately uniform. Any change in species content of the
synusia is likely, therefore, t o indicate directly a change in habitat.
Accordingly the classification and comparison of synusiae is likely t o
be profitable. Various criticisms have been levelled at treating synusiae
as material for study and classification (Nordhagen, 1943 ; Dahl, 1956)
on the grounds that the various synusiae in a phytocoenose are functionally and dynamically connected with one another. This cannot be
denied; but for certain purposes the other synusiae can be treated as
biotic factors of the environment and one synusia isolated for more
detailed study. This approach is not arbitrary; for it is clear that the
synusiae operate as independent units and may replace each other
within the same phytocoenose. The principles according t o which
synusiae may be classified will be considered later.
Where does a synusia end and a phytocoenosis begin? This depends,
according t o Gams (1918), on the consistency of the interrelationships
between the various parts of a complex community. He gives the following example of a resolution of this problem (Poore, 1955b): “A
wood is always considered as a phytocoenose, except when the rorrelations between the various synusiae which form it are so close that the
field and ground layers can only occur under the particular tree layer
concerned.’’ This is an excellent and rational working rule and corresponds to the treatment of mosaics given above. Both groups can only
be employed after examination of a large number of stands and are
accordingly subjective.
The description of a phytocoenose should be made in terms of its
synusiae and these should be sampled separately. One of these synusiae
is likely t o be dominant in the sense that it determines the presence of
the other synusiae by modifying the micro-climate or the soil. Comparison between phytocoenoses should be made principally on the basis
of the dominant synusia as this reflects the general ecological L , -h aracteristics of the habitat more faithfully than the subordinate synusiae.
The principles of classification and comparison of phytocoenoses will
be considered below.
M. E. D. P O O R E
woodland floor or the groupings of annuals and geophytes which may
be found in garrigue in the Mediterranean region. These are known as
synusiae. Cain and de Oliviera Castro (1959) define the synusia as “a
social aggregate consisting of one or a few closely related life forms
occurring together and having a similar ecology ... . The total complex
of synusiae that simultaneously occupy the same terrain is called a
phytocoenose ; this the usual concept of community”.
In comparing and classifying synusiae one is comparing groups of
ecologically closely related species growing in a habitat which is, for
them, approximately uniform. Any change in species content of the
synusia is likely, therefore, t o indicate directly a change in habitat.
Accordingly the classification and comparison of synusiae is likely t o
be profitable. Various criticisms have been levelled at treating synusiae
as material for study and classification (Nordhagen, 1943 ; Dahl, 1956)
on the grounds that the various synusiae in a phytocoenose are functionally and dynamically connected with one another. This cannot be
denied; but for certain purposes the other synusiae can be treated as
biotic factors of the environment and one synusia isolated for more
detailed study. This approach is not arbitrary; for it is clear that the
synusiae operate as independent units and may replace each other
within the same phytocoenose. The principles according t o which
synusiae may be classified will be considered later.
Where does a synusia end and a phytocoenosis begin? This depends,
according t o Gams (1918), on the consistency of the interrelationships
between the various parts of a complex community. He gives the following example of a resolution of this problem (Poore, 1955b): “A
wood is always considered as a phytocoenose, except when the rorrelations between the various synusiae which form it are so close that the
field and ground layers can only occur under the particular tree layer
concerned.’’ This is an excellent and rational working rule and corresponds to the treatment of mosaics given above. Both groups can only
be employed after examination of a large number of stands and are
accordingly subjective.
The description of a phytocoenose should be made in terms of its
synusiae and these should be sampled separately. One of these synusiae
is likely t o be dominant in the sense that it determines the presence of
the other synusiae by modifying the micro-climate or the soil. Comparison between phytocoenoses should be made principally on the basis
of the dominant synusia as this reflects the general ecological L , -h aracteristics of the habitat more faithfully than the subordinate synusiae.
The principles of classification and comparison of phytocoenoses will
be considered below.