520 



THE COMMUNITY 



formula, considers Xm as referring to the 

 immediately preceding level, so that: 



Xn 

 Xo_ 



100 



represents a progressive relative eflBciency 

 at a given level in terms of relative pro- 

 ductivities. This manipulation gives a sug- 

 gestion of the degree of utilization of the 

 potential source of energy (food supply) 

 for each level of the community (Table 46) . 



satisfactory comparison of productivity 

 would be rate of production in energetic 

 terms. As in glucose formation, there are 

 too many types of inland waters, too many 

 parts of the sea, and too many kinds of 

 terrestrial communities yet uninvestigated 

 in this respect to make such a comparison 

 extensive or critical. 



A useful approach is the admirable 

 summary by Clarke (1946) on production 

 on Georges Bank, in the North Atlantic off 



Table 46. Productivities (in g-cal./cm^/year) and Biological Efficiencies (in per cent) for Two 

 American Lakes (Modified from Lindeman, 1942) 



Trophic Level 



Solar radiation (Xo) 



Photosynthetic plants (Ai) 



Herbivores (A 2) 



Carnivores (A 3(^1)) 



Carnivores (Aa^^-)) 



Cedar Bog Lake, 



Minnesota 



(after Lindeman 1941, 



1942) 



Corrected 

 Productivity 



118,872 

 111.3 

 14.8 

 3.1 

 (not present) 



Biological 

 Efficiency 



O.IOS^ 

 13.3% 

 22.3% 



Lake Mendota, 



Wisconsin 



(Based on Juday, 1940) 



Corrected 

 Productivity 



118,872 

 480* 

 41.6 

 2.3f 

 0.3 



Biological 

 Efficiency 



0.40% 

 8.7% 

 5.5% 

 13.0% 



** Lindeman (1942) considers this value too high, and Hutchinson (cf. Lindeman) thinks 

 it may be as low as 250. 



t Lindeman (1942) considers this value too low. Possibly this may be a consequence of 

 the presence of large predators. 



From a comparison of Tables 45 and 

 46, an interesting generalization may be 

 made that, within a given community, the 

 biological efficiencies increase as the rates 

 of production, or productivities, decrease. 

 This is seen in Lindeman's study of Cedar 

 Bog Lake, where no large predators (game 

 fishes) are present. It is seen in the much- 

 studied Lake Mendota, where at least two 

 grades of predators are in the level of 

 secondary consumers. There is no reason 

 to suppose that this productivity /efficiency 

 ratio (p/e) is not universal for major com- 

 munities in approximate biotic balance. We 

 propose that this relationship be termed the 

 Lindeman ratio, inasmuch as it was derived 

 from his careful work. So far, confirmation 

 is lacking for marine and terrestrial com- 

 munities. 



Previously, several types of communities 

 were contrasted in terms of glucose pro- 

 duction per unit area (Table 44). A more 



the coast of Massachusetts. Three million 

 gram-calories of energy fall on each square 

 meter of sea surface per day on Georges 

 Bank. The diatoms of the phytoplankton 

 utilize a portion of this energy in photo- 

 synthesis, and their maximum efficiency 

 calculated from the rate of diatom produc- 

 tion is 0.3 per cent. In turn, the zooplank- 

 ton feed upon the diatoms, obtaining their 

 solar energy at second hand, and their 

 maximum efficiency calculated from the 

 rate of zooplankton production is about 

 0.015 per cent. Finally, fishes feed upon 

 zooplankton directly in part, and indirectly 

 in fish-eating species. The weight of whole 

 fishes landed annually from the ten million 

 acres of Geor2:es Bank, between 1923 and 

 1945, ranged from a minimum of sixty- 

 three million pounds (1934) to a maximum 

 of 289 million pounds (1929). In terms of 

 yield, this represents a production of 7 to 

 33 pounds per acre per year. In terms of 



