COMMUNITY ORGANIZATION: METABOLISM 



507 



autumnal, pulse. If the maximum August 

 daily production of glucose is used as an 

 average for the growing season (Manning 

 and Juday, 1941), lake plankton could pro- 

 duce 39 pounds of glucose per day per 

 acre. A third of this yield has been added 

 for the glucose of rooted aquatic plants, 

 and the growing season placed at 240 days 

 (March to October). This is tentative for 

 north temperate lakes, since phytoplankton 

 often metabohze for a much longer period, 

 possibly 300 days in parts of the area or in 

 some years. Production for higher or lower 

 latitudes would differ from this tentative 

 average. 



With respect to grassland, Transeau 

 (1926) gave 200 pounds of glucose as the 

 yield of an acre of field corn (p. 506), and 

 the growing season for this annual herb as 

 100 days. Later, Transeau, Sampson, and 

 Tiffany (1940, Chap. 20) discussed the 

 subject of energy transformation and 

 pointed out that this glucose yield was 

 high, and might average as much as one- 

 third of the maximum. This would reduce 

 the yield to something like 70 to 80 pounds 

 per day per acre of field corn. On the 

 other hand, natural tall grass prairie might 

 do better than average field corn if allow- 

 ance is made for stratification. The grow- 

 ing season would certainly be longer, and 

 we have substituted 150 days (April to 

 August) for the growing season, and have 

 increased the daily yield by 30 per cent 

 over the average corn figure. 



With respect to deciduous forest, Hein- 

 icke and Childers (1937) have given us 

 glucose production figures for an acre of 

 apple trees in New York. They find the 

 growing season to be 188 days, and the 

 photosvnthetic productivity to be 93 

 pounds of glucose per day per acre of 400 

 trees. If we use this figure for the tree 

 stratum of woody perennials, and add one- 

 third to allow for the shrub and herbaceous 

 strata, the conservative estimate of 125 

 pounds of glucose per day is obtained. This 

 would apply to average canopy develop- 

 ment, and not to a community of tall, old 

 deciduous trees. An estimated season of 180 

 days (April to September) has been used. 



These glucose productivities are esti- 

 mates. They represent a portion of the po- 

 tential energy stored later in plant protein 

 synthesis. In turn, such compounds are 

 available for plant growth and as a margin 



for animal consumption in the balanced, 

 self-maintaining community. 



Table 44. Estimated Photosynthetic Productivity 



in Terms of Pounds of Glucose, per Day, and 



Growing Season, per Acre for Typical 



North Temperate Communities 



It must be remembered that these glu- 

 cose yields are suggestive, rather than 

 actual; that they are based on different 

 lengths for the growing season; and that 

 they deal with the green plants of the com- 

 munity only. 



The postulate has just been made that 

 the grassland community has a lower total 

 photosynthetic productivity than the forest 

 community. This extends the argument pre- 

 viously advanced that the higher develop- 

 ment of stratification in forests is probably 

 partially the cause of this higher productiv- 

 ity. This argument suggests that stratifi- 

 cation of structure and photosynthetic pro- 

 ductivity are expressions of the developing 

 complexity of the community, making 

 more space available, and increasing the 

 amounts of carbohydrates and proteins. 

 This increase in the utilization of the space 

 lattice is accompanied by increasing utiliza- 

 tion of time from the point of view of over- 

 lapping periodicities. 



We have been concerned with two key 

 industries in the metabolism of the com- 

 munity. These are anabolic. They have to 

 do with the transformation of energy, and 

 with the formation of plant protein 

 and carbohydrates. The catabolic proc- 

 esses in connection with bacterial activity 

 have been touched upon. We turn next to 

 the study of the catabolic processes of the 

 community, that is, the transfer and resyn- 

 thesis of these plant materials into animal 

 protoplasms, and their eventual conversion 

 to raw products once more, in the circula- 

 tion of substances in the community. 



In general temis, a community at the 

 level of self-maintenance is a self-regulating 

 assemblage in which the populations of 



