98
MANFRED D . ENGELMANN
be considered. The data on the grasshopper were those of Smalley
(1960). The gross productivity of 29.4 kcal/m2 was used by Teal. A
gross productivity figure of 275 kcal/m2/year was reported for an average
standing crop of 70 kcal/m2 for Prokelisia, the plant bug. Teal calculated
that the nematodes respired 64 kcal/m2/year, and he assumed production in the marsh to be 21 kcal/m2/year or 25% of the respiration rate.
Teal did not calculate ecological efficiencies for the various trophic
levels, although he did report efficiencies for the utilization of the Spartina standing crop by the insects 4.6%). If we use the formula by
Engelmann (1961) which is correctlyreported by Slobodkin (1962, p. 98),
an ecological efficiency of 6.8 can be obtained for the herbivore-carnivore
trophic levels. Teal’s paper is important because it deals with an
ecotone. The work suffers because it relied too heavily upon assumptions and was not sufficiently comprehensive.
B. TROPHIC DYNAMIC ANALYSIS OF (‘OLD FIELD” COMMUNITIES
The second group of papers to be discussed center on the “old field”
habitat. Studies have been made under the very different climatic conditions of southern Michigan and Georgia.
Golley and Gentry (1964) studied the bioenergetics of the southern
harvester ant, Pogonomyrmex badius in South Carolina. They located
ant hills in the “old field” study area, labeled individuals radioactively
with P32 to estimate the numbers of animals in each hill by mark - release - and recapture methods. Ant hills were excavated to ascertain
the numbers of all stages present, and respiration measurements were
made on the various stages. Counts indicated that there were 0.0027
hillslm2 and that each hill contained from 4 000 to 6 000 individuals.
From data on numbers present and respiration studies, it was calculated that 14.2-47.7 kcal/m2/year were lost by the population in respiration. Using the numbers of young found in the hills, plus supplementary
data, Golley and Gentry estimated that the ants produced 0.09 kcal/ma
in new individuals each year. The authors did not make an estimate of
calories lost to the population through death. The total estimates for
P . badius were: net productivity 0.09 kcal/m2/year; gross productivity
14.29 to 47.79 kcal/mZ/year. Golley and Gentry reported that the ant
was primarily a gramnivore and that the field produced 22 kcal/m2/
year in seeds. The ant, then, consumed the equivalent of 64 to 213% of
the seed crop each year. Since the field also supported other gramnivores
(mice and sparrows), the authors concluded that other foods must have
been used by the ants in addition to seed. The authors noted that the ant
consumed more energy than either the sparrow (4 kcal/ma/150 days) or
the mouse (7-17 kcal/mQ/year) populations associated with it in the
“old fields”.
MANFRED D . ENGELMANN
be considered. The data on the grasshopper were those of Smalley
(1960). The gross productivity of 29.4 kcal/m2 was used by Teal. A
gross productivity figure of 275 kcal/m2/year was reported for an average
standing crop of 70 kcal/m2 for Prokelisia, the plant bug. Teal calculated
that the nematodes respired 64 kcal/m2/year, and he assumed production in the marsh to be 21 kcal/m2/year or 25% of the respiration rate.
Teal did not calculate ecological efficiencies for the various trophic
levels, although he did report efficiencies for the utilization of the Spartina standing crop by the insects 4.6%). If we use the formula by
Engelmann (1961) which is correctlyreported by Slobodkin (1962, p. 98),
an ecological efficiency of 6.8 can be obtained for the herbivore-carnivore
trophic levels. Teal’s paper is important because it deals with an
ecotone. The work suffers because it relied too heavily upon assumptions and was not sufficiently comprehensive.
B. TROPHIC DYNAMIC ANALYSIS OF (‘OLD FIELD” COMMUNITIES
The second group of papers to be discussed center on the “old field”
habitat. Studies have been made under the very different climatic conditions of southern Michigan and Georgia.
Golley and Gentry (1964) studied the bioenergetics of the southern
harvester ant, Pogonomyrmex badius in South Carolina. They located
ant hills in the “old field” study area, labeled individuals radioactively
with P32 to estimate the numbers of animals in each hill by mark - release - and recapture methods. Ant hills were excavated to ascertain
the numbers of all stages present, and respiration measurements were
made on the various stages. Counts indicated that there were 0.0027
hillslm2 and that each hill contained from 4 000 to 6 000 individuals.
From data on numbers present and respiration studies, it was calculated that 14.2-47.7 kcal/m2/year were lost by the population in respiration. Using the numbers of young found in the hills, plus supplementary
data, Golley and Gentry estimated that the ants produced 0.09 kcal/ma
in new individuals each year. The authors did not make an estimate of
calories lost to the population through death. The total estimates for
P . badius were: net productivity 0.09 kcal/m2/year; gross productivity
14.29 to 47.79 kcal/mZ/year. Golley and Gentry reported that the ant
was primarily a gramnivore and that the field produced 22 kcal/m2/
year in seeds. The ant, then, consumed the equivalent of 64 to 213% of
the seed crop each year. Since the field also supported other gramnivores
(mice and sparrows), the authors concluded that other foods must have
been used by the ants in addition to seed. The authors noted that the ant
consumed more energy than either the sparrow (4 kcal/ma/150 days) or
the mouse (7-17 kcal/mQ/year) populations associated with it in the
“old fields”.