ENERGETICS AND ANIMAL PRODUCTIVITY
101
was able to calculate the ecological efficiency (gross efficiency of yield/
ingestion) by assuming “instantaneous predahion”. The figures he obtained ranged from 0.8~0-17-4%.
Wiegert’s paper is significant, not only because it is an example of
careful analysis, but because it dealt with a species in the two extremes
of its total habitat range. The gross and net productivities in the alfalfa
field exceeded most other productivities for arthropods reported in the
literature (save that of P. badius, Golley and Gentry, 1964). Yet, in the
“old field” the spittle bugs could not survive. Wiegert’s study pointed
again to the inadequacy of the Lindeman model in a situation of
imbalance.
Another study made on this “old field” of the E. S. George Reserve
was concerned with the soil arthropods (Engelmann, 1961). The study
used the author’s results and data collected previously by Hairston and
Byers (1954). The mite population was estimated from monthly soil
samples processed in Tullgren funnels. Indivilduals of each species were
’ weighed on a quartz helix balance, and the numbers and weight data
were used to estimate biomass. Data on respiration rates measured with
a, simple constant pressure respirometer were used in conjunction with
biomass information to calculate total maintenance metabolism. Radiotracer experiments gave figures on ingestion. Soil organisms were cultured in the laboratory and studied to gain information on life span,
ingestion and egestion, and birth rate. Infor mation from cultures and
field data provided a basis for making assumptions on survival. From
these data a complete energy balance sheet was constructed for the
Oribat ei .
The study approached the problem of energetics at two levels: fist
at a lower level, or taxon, concentrating upon the Oribatei; on a second
level all of the soil arthropods were included. The analysis of data on
oribatids resulted in estimates as follows: a standing crop of 0.27 kcal
on an average square meter of “old field”; ingested 10.248 kcal; assimilated 2.058 kcal; respired 1.965 kcal, and lost through mortality 0.43
kcal each year.
These data and preserved materials of Hairston and Byers (1954)
were used to estimate the ecological efficiency of the carnivores with
respect to the herbivores. Knowledge of respiration estimates and assimilation efficiency for both herbivores and carnivores made possible
calculations of efficiency values. The most reasonable ecological efficiencies ranged from 8% to 30% with 16.90/,, the most probable value.
The production on this field was very low when compared with the area
sampled by Berthet, for example. Nematodes andnrotifers were scarce
in the poor, well-drained field soil. The combined respiration of these
organisms yielded about 0.36 kcal/m2/year.
101
was able to calculate the ecological efficiency (gross efficiency of yield/
ingestion) by assuming “instantaneous predahion”. The figures he obtained ranged from 0.8~0-17-4%.
Wiegert’s paper is significant, not only because it is an example of
careful analysis, but because it dealt with a species in the two extremes
of its total habitat range. The gross and net productivities in the alfalfa
field exceeded most other productivities for arthropods reported in the
literature (save that of P. badius, Golley and Gentry, 1964). Yet, in the
“old field” the spittle bugs could not survive. Wiegert’s study pointed
again to the inadequacy of the Lindeman model in a situation of
imbalance.
Another study made on this “old field” of the E. S. George Reserve
was concerned with the soil arthropods (Engelmann, 1961). The study
used the author’s results and data collected previously by Hairston and
Byers (1954). The mite population was estimated from monthly soil
samples processed in Tullgren funnels. Indivilduals of each species were
’ weighed on a quartz helix balance, and the numbers and weight data
were used to estimate biomass. Data on respiration rates measured with
a, simple constant pressure respirometer were used in conjunction with
biomass information to calculate total maintenance metabolism. Radiotracer experiments gave figures on ingestion. Soil organisms were cultured in the laboratory and studied to gain information on life span,
ingestion and egestion, and birth rate. Infor mation from cultures and
field data provided a basis for making assumptions on survival. From
these data a complete energy balance sheet was constructed for the
Oribat ei .
The study approached the problem of energetics at two levels: fist
at a lower level, or taxon, concentrating upon the Oribatei; on a second
level all of the soil arthropods were included. The analysis of data on
oribatids resulted in estimates as follows: a standing crop of 0.27 kcal
on an average square meter of “old field”; ingested 10.248 kcal; assimilated 2.058 kcal; respired 1.965 kcal, and lost through mortality 0.43
kcal each year.
These data and preserved materials of Hairston and Byers (1954)
were used to estimate the ecological efficiency of the carnivores with
respect to the herbivores. Knowledge of respiration estimates and assimilation efficiency for both herbivores and carnivores made possible
calculations of efficiency values. The most reasonable ecological efficiencies ranged from 8% to 30% with 16.90/,, the most probable value.
The production on this field was very low when compared with the area
sampled by Berthet, for example. Nematodes andnrotifers were scarce
in the poor, well-drained field soil. The combined respiration of these
organisms yielded about 0.36 kcal/m2/year.