ENERGETICS AND ANIMAL PRODUCTIVITY
111
where N is the total number of poikilothermic species in the community,
P, net productivity in calories and Rp, annual respiration in calories.
It follows that estimation of net productivity should be possible, if the
average respiration ( R p ) and the total number of species present in the
community are known, by using the formula:
N Log R1, - 0.62
0.83
~When testing this formula on Macfadyen’s (1963b) community data
and my own oribatid data (Engelmann, 1961 Table 4, p. 226), I found
that the average respiration consistently gax-e an estimate which was
8 to 12% lower than net productivity calculated from the respiration
of each individual species. The formula for crdculating community net
productivity, using average respiration rate would then become :
)
N Log Rp - 0.62 + 0.1 (! Log T8; 0.62
L o g p =
0.83
which is not very satisfying.
Finally, if we are to calculate the total net productivity of an entire
animal community, we must include a term for the homiotherms. The
homiotherm regression in Fig. 2 does not show a significant correlation
with the points on the Figure. If we assume, however, that the regression line fits, then the equation for total net productivity of the community would be :
1
1
N
N’
ZLog Rp - 0.62 + ZLOg Rh - 2.59
Log p = ~~
~
~
_
_
_
2-61
where N equals the total number of poikilothermic species, N 1 equals
total number of homiothermic species, Rp = annual respiration (in
kcal) of poikilotherms, and Rh = annual respiration (in kcal) of homiotherms. If, however, the homiotherm slope is actually that of the
poikilotherms, then the constant in the homio1;herm portion of the equation would be 1.7 and the divisor would be changed to 1.72.
These equations, if valid, will be useful tools for the further analysis
of communities, inasmuch as the respiration of a species is relatively
easy to measure.
Finally, it is reasonable to hypothesize that a relationship exists between total caloric ingestion and net productivity. It is also probable
that the relationship of calories ingested ancrnet productivity at the
community level, though simpler, is not so aclxrate as the relationships
of respiration and net productivity.
111
where N is the total number of poikilothermic species in the community,
P, net productivity in calories and Rp, annual respiration in calories.
It follows that estimation of net productivity should be possible, if the
average respiration ( R p ) and the total number of species present in the
community are known, by using the formula:
N Log R1, - 0.62
0.83
~When testing this formula on Macfadyen’s (1963b) community data
and my own oribatid data (Engelmann, 1961 Table 4, p. 226), I found
that the average respiration consistently gax-e an estimate which was
8 to 12% lower than net productivity calculated from the respiration
of each individual species. The formula for crdculating community net
productivity, using average respiration rate would then become :
)
N Log Rp - 0.62 + 0.1 (! Log T8; 0.62
L o g p =
0.83
which is not very satisfying.
Finally, if we are to calculate the total net productivity of an entire
animal community, we must include a term for the homiotherms. The
homiotherm regression in Fig. 2 does not show a significant correlation
with the points on the Figure. If we assume, however, that the regression line fits, then the equation for total net productivity of the community would be :
1
1
N
N’
ZLog Rp - 0.62 + ZLOg Rh - 2.59
Log p = ~~
~
~
_
_
_
2-61
where N equals the total number of poikilothermic species, N 1 equals
total number of homiothermic species, Rp = annual respiration (in
kcal) of poikilotherms, and Rh = annual respiration (in kcal) of homiotherms. If, however, the homiotherm slope is actually that of the
poikilotherms, then the constant in the homio1;herm portion of the equation would be 1.7 and the divisor would be changed to 1.72.
These equations, if valid, will be useful tools for the further analysis
of communities, inasmuch as the respiration of a species is relatively
easy to measure.
Finally, it is reasonable to hypothesize that a relationship exists between total caloric ingestion and net productivity. It is also probable
that the relationship of calories ingested ancrnet productivity at the
community level, though simpler, is not so aclxrate as the relationships
of respiration and net productivity.