Nature 408, 578 - 580 (2000) © Macmillan Publishers Ltd.
Nutritional constraints in terrestrial and freshwater food webs
JAMES J. ELSER, WILLIAM F. FAGAN, ROBERT F. DENNO, DEAN R. DOBBERFUHL, AYOOLA
FOLARIN, ANDREA HUBERTY, SEBASTIAN INTERLANDI, SUSAN S. KILHAM, EDWARD
MCCAULEY, KIMBERLY L. SCHULZ, EVAN H. SIEMANN & ROBERT W. STERNER
Biological and environmental contrasts between aquatic and terrestrial
systems have hindered analyses of community and ecosystem structure across
Earth's diverse habitats. Ecological stoichiometry provides an integrative
approach for such analyses, as all organisms are composed of the same major
elements (C, N, P) whose balance affects production, nutrient cycling, and
food-web dynamics. Here we show both similarities and differences in the
C:N:P ratios of primary producers (autotrophs) and invertebrate primary
consumers (herbivores) across habitats. Terrestrial food webs are built on an
extremely nutrient-poor autotroph base with C:P and C:N ratios higher than in
lake particulate matter, although the N:P ratios are nearly identical.
Terrestrial herbivores (insects) and their freshwater counterparts
(zooplankton) are nutrient-rich and indistinguishable in C:N:P stoichiometry.
In both lakes and terrestrial systems, herbivores should have low growth
efficiencies (10–30%) when consuming autotrophs with typical
carbon-to-nutrient ratios. These stoichiometric constraints on herbivore
growth appear to be qualitatively similar and widespread in both environments.
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