COMPONENT !■ \SHIPS 



Yet the ecosystem functions in the 

 way it does because of the specific 

 response of each and every animal in 

 the ecosystem, the totality of which 

 represents the food pyramid or web 

 of life. Understanding of these mat- 

 ters is critical to our understanding 

 of climate and its effect on plant and 

 animal communities of the world. 



Greatly improved physiological 

 measurements of metabolic rates and 

 water-loss rates as a function of 

 environmental conditions are needed. 

 It is necessary to know the values 

 of radiation absorbed by the animal, 

 air temperature, wind speed, and hu- 

 midity during the course of any 

 measurements. The conditions under 

 which the animal was conditioned 

 must be specified. In the laboratory, 

 it would be particularly important 

 that complete energy-budget analyses 

 be done for each set of observations 

 of the animal. In the field, careful 

 observations are needed of metabolic 

 rates and water-loss rates as well as 

 of the microclimate conditions near 

 the animal. These measurements are 

 difficult to make, but must be done 

 and can be done with the aid of 

 telemetry and other modern methods. 



Systems Analysis 



On the one hand, mathematical 

 analysis of the productivity of in- 

 dividual plant leaves is now being 

 done based on a holistic approach 

 including the use of physics, chem- 

 istry, physiology, and biochemistry. 

 On the other, agronomists are work- 

 ing out the energy and gas exchange 

 of a community of simple plants — 

 e.g., corn, wheat, or millet. A great 

 deal of work is required to bridge 

 the gap between these two ap- 

 proaches. A given species has leaves 

 that may occupy various parts of a 

 plant canopy. The leaves forming 



one part of a canopy are in an en- 

 tirely different microclimate than the 

 leaves of another part, and the prop- 

 erties of shade leaves are different 

 from the properties of sun leaves of 

 the same species. One can evaluate 

 the individual leaves of each part of 

 a canopy, apply the numbers game 

 for all the leaves of a part of the 

 canopy, and integrate over the entire 

 canopy for productivity, respiration, 

 total water use, and so on. This ap- 

 proach will match up eventually with 

 the approach of the agronomist to 

 the problem of evaluating the whole 

 stand. However, since the ecologist 

 is interested in the role of various 

 species within a stand, it is necessary 

 to take this detailed approach. 



Competition and Phenology — The 

 ecologist is interested in competition 

 among the species of a plant commu- 

 nity — competition for light, mois- 

 ture, carbon dioxide, and nutrients, 

 and maybe for wind and air flow, 

 soil bacteria, and other factors. In 

 order to understand competition one 

 must understand the plant response 

 to energy and gas exchange as they 

 affect growth, flowering, seed devel- 

 opment, and so on. A closely related 

 topic is phenology — the response of 

 organisms to time-cycles of climate. 

 To understand phenology we need 

 to understand the temperature of a 

 plant as it responds to the climate 

 of soil and air and to realize the 

 significance of events throughout the 

 season that may integrate into plant 

 response. Studies of competition and 

 phenology require good laboratory 

 measurements and good field meas- 

 urements. It is not so necessary to 

 obtain an abundance of field data, 

 however, as it is to analyze well and 

 completely the field data obtained. 



Prediction — As we understand the 

 specific response of animals to energy 

 flow (radiation, convection, conduc- 



tion, evaporation, and metabolism), 

 we can begin to work out the re- 

 sponse of a set of organisms within 

 a community. (See Figure IX-8) It is 

 not sufficient to know the amount of 

 energy transferred through the food 

 pyramid from primary producer to 

 primary, secondary, and tertiary con- 

 sumers; it is also important to under- 

 stand the energetics of each organism 

 in the community and the response of 

 each organism to all climate and 

 edaphic factors. Furthermore, be- 

 havioral studies of some animal pop- 

 ulations often ignore or treat only 

 cursorily the detailed environmental 

 conditions. Animal behavior will of- 

 ten respond to energy flow, as well 

 as to other factors, in an intimate 

 fashion. 



Despite an acute shortage of good 

 physiological data for most animals, 

 we can begin to simulate on the com- 

 puter communities of plants and an- 

 imals and their response to climate. 

 We can set up simple experimental 

 ecosystems in the laboratory or out- 

 of-doors and check prediction from 

 a model against observation. We 

 need much better evaluations of en- 

 ergy flow through various ecosys- 

 tems, as well as evaluations of gas 

 exchange and nutrient flow. The 

 biome studies of the International 

 Biological Program will add consider- 

 able knowledge, but much remains 

 to be done. 



Modern science has the capacity to 

 do a much better job of analyzing 

 energy flow through ecosystems and 

 evaluating specific physiological re- 

 sponse. Here is a magnificent oppor- 

 tunity for a strong theoretical dis- 

 cipline to be developed. It must be 

 based on good physiological data 

 from the plant and animal sciences. 

 Theoretical development must be 

 constantly checked by field observa- 

 tions. 



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