Fig. 6.1. Time course of changes in a food web involving plants, herbivores that eat the plants, and carnivores that eat
the herbivores. Plants grow rapidly during the 90 day experiment, supporting the slower growth of the animal
consumers. Plant isotopes change quickly towards the value of the added N nutrient that in this case has an isotope
label of 1000o/oo. Animal isotope values approach the 1000o/oo value more slowly due to lags as label is transferred
from one trophic level to the next, a) from plants to herbivores, and b) from herbivores to carnivores, plus c) slower
growth of animals, and d) slower tissue turnover rates in animals.