Calorific Equivalents for Studies in Ecological
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CALORIFIC EQUIVALENTS FOR STUDIES IN ECOLOGICAL ENERGETICS Compiled by Kenneth W. Cummins Pymatuning Laboratory of Ecology University of Pittsburgh Pittsburgh, Pennsylvania 15213 Second Edition, October, 1967 TABLE OF CONTENTS Page Introduction ......................................................................................... 1 Notations ............................................................................................... 2 I. Superscript for Calorie Values and Error Terms .. 2 II. Season Material was Collected .................................... 2 III. Parts of Organisms Used .........3 IV. Methods of Analysis ......................................................... 4 V. Authors and Sources of Data ........................................... 4 VI. General Notes 6 VII. Notations for Mean Values ............................................. 10 Literature Cited in Introduction ................................................... 11 Table of Calorific Equivalents ....................................................... 12 I. Primary Producers ....................................................... 12 A. Aquatic 12 B. Terrestrial ................................................................ 14 II. Microconsumers ............................................................. 32 A. Aquatic 32 B. Detritus (defined as partially decayed organic matter plus bacterial and fungal flora) ............. 32 1. Aquatic ................................................................... 32 2. Terrestrial 32 III. Macroconsumers ............................................................. 33 A. Aquatic ........................................................................ 33 B. Terrestrial ................................................................ 40 IV. Miscellaneous Materials ............................................... 47 V. Summary Values 48 A. Primary Producers ............................................... 48 B. Microconsumers ..................................................... 50 C. Macroconsumers ..................................................... 51 IN TRODUCTION Since Lindeman (1942) exerted a synthesizing influence on the theory of the "trophic dynamic aspects of ecology," the tendency to deal in the common denominator of the calorie has increased steadily among ecologists. The progression has recently culminated in the equilibration of ecosystem ecology and ecological energetics (e. g. Philipson, 1966). This equivalence intended by ecological investigators has created a demand for calorific values. Several summaries of calorific values have been presented previously (e. g. Slobodkin and Richman, 1961 and Golley, 1961). The present tabulation is an attempt to expand former summaries and to indicate areas, speaking both taxonomically and ecologically, where calorie data are wanting. A number of problems associated with a tabulation of caloric equi- valents should be stressed. In the first place the total theoretical gram calorie range for living organisms, namely about 3850 for pure carbohydrate to about 9500 for pure fat is rather narrow and actual organisms would be expected to exhibit only a portion of this range (4013 to 8190 from the table on a per ash-free gram basis). This means, that given the other rather large errors with which ecology is presently forced to deal, it might be more realistic to use a median calorie value or a grand mean, or at the very least a producer mean and a consumer mean. Another frequent objec- tion concerns the large variation in calorie values dependent upon such variables as the season of collection, diet of the organisms (and, incidentally, whole individual values almost always include the gut contents of such organisms) and sex of the individuals burned. The latter objection is parti- cularly critical since females carrying eggs usually would be expected to have the highest values for a given species. With regard to seasonal varia- tion, of particular interest are the extremely high values of premigratory birds due to large fat reserves. Another variable concerns methodology. The three most common procedures employed so far involve 1) various types of oxygen bomb calorimeters manufactured by the Parr Instrument Company (Moline, Illinois 61265), 2) modifications of the Philipson Bomb such as that manufactured by Gentry-Wiegert Instruments (313 Silver Bluff Road, Aiken, South Carolina 29801) or 3) wet dichromate oxidation as described by Maciolek (1962). With regard to the problem of per gram dry weight vs. per ash-free gram weight values, it seems that both values are still required. This is especially true if ash values are based on residual weights obtained in bomb calorimetry. Such ash determinations are highly variable and separate percentage ash measurements will eventually be required. Naturally, such refinements in percentage ash must be applied to per gram dry weight determinations. Also, since many ecologists are interested in converting biomass data to calorie equivalents, the almost complete lack of data on ash-free weights means that such conversions must be made by multiplying grams dry weight times per gram dry weight calorie values. However, there is no doubt that the comparison of calorie value s along taxonomic or ecologic lines is best accomplished by employing calorie per ash-free gram values. Finally, unless percentage water data are available conversions between per gram dry weight and wet digestion values are impossible. 2 Regardless of the many objections, it does seem reasonable at present to take stock of the calorie values obtained thus far. In most cases these values carry withh them specific data as to the nature of the material burned and some estimate, such as standard error, of the variation encountered within a given set of samples. Comparison of values for the same species obtained in different laboratories should allow conclusions to be drawn relative to seasonal, habitat3 dietary and other differences that might be expected. Thus, if either extreme prevails, that is very narrow ranges cutting across vastly different taxonomic and ecologic groups or, wide ranges of variation even within the same species, we will have the data from which to decide on an approach that will yield maximum benefit to the field of ecology. Much of the tabulation which follows was compiled with the help of the staff and students of the Pymatuning Laboratory of Ecology of the University of Pittsburgh. Many of the included values were brolgit to my attention by workers at other institutions and their assistance is greatfully acknowledged. Naturally, the table is not complete, particularly since a wealth of data undoubtedly exist in various theses and manuscripts yet to be brought to my attention. The data have been organized according to categories that should be most useful for ecosystem ecologists. The primary organization is according to trophic levels and the secondary organization is according to habitat. Within secondary categories the data are presented by taxonomic grouping down to the family level. Summary mean values have been presented separately. These are not "true means" since table entries were averaged rather than individual determinations. The outline of the tabular presentation can be found in the table of contents above. NOTATIONS I. Superscript Notations for Calorie Values and Error Terms 1. Value calculated from data reported by the author 2. Standard error 3. 95% confidence limits 4. Standard deviation 5. Coefficient of variation 6. Plus or minus the range, i. e. difference between high and low values 7. % deviation from the mean II. Season Material Was Collected 1. January 2. February 3. March 4. April 5. May 6. June 7. July • 3 8. August 9. September 10. October 11. November 12. December 13. Spring 14. Summer 15. Fall 16. Winter 17. Laboratory culture 18. November through March 19. Throughout the year 20. June through July 21. April through May 22. October through May 23. October, December through May, July III. Parts of Organism Used and Sex 1. Entire plants or entire cells in the case of algae, bacteria or protozoans 2. Stems 3. Leaves or needles 4. Roots 5. Seeds, 5a. Hulled seeds 6. Flowers, 6a. Male flowers, 6b. Female flowers 7. Nectar 8. Eggs, 8a. Egg sacs with eggs, 8b. Ovaries with eggs, 8c. Newly fertilized, 8d. yolk only 9. Larvae or nymphs 10. Pupae 11. Adults, I la. adult males, 11b. adult females 12. Roots, stems, leaves, fruits 13. Roots, stems leaves, flowers 14. Roots, stems, leaves 15. Stems, leaves 16. Stems, leaves, capsule with spores 17. Thallus 18. Fruits 19. Tops (mixed), stems, leaves, roots, fruits, flowers 20. Mixed proportions of stems, leaves, roots, fruits, flowers 21. Bark 22. Entire animal without shell 23. Animals divided into three general size classes: a=small, b=medium, c=large 24. Entire animals of varying size classes; 24a both sexes, 24b. sexes not determined 25. Juveniles, 25a. males, 25b. females 26. Adults - values for non-fat (that is fat extracted) individuals 27. Adults - values for body fat only 28. Prepupal larvae 29. Newly emerged adults 30. Eleven day pupae • 4 31. 144 hour tadpoles 32. Live needles 33. Live twigs 34. All above ground parts 35. Dead twigs 36. Dead leaves 37. Copepodite stages: a=I, b=II, c=III, d=IV, e=V 38. Copepodite stage V, fat only IV. Methods of Analysis 1. Unknown 2. Wet digestion, 2a. dichromate digestion method 3. Parr oxygen bomb a. Macrobomb non-adiabatic b. Macrobomb adiabatic c. Semi-microbomb non-adiabatic d. Semi- microbomb adiabatic 4. Phillipson