Big ecology idea of the week is possible top-down control of nutrient cycling. If herbivores selectively eat plants with higher nutrition, they could either limit those plants (decelerating cycling) or cause more to grow (accelerate cycling). Here are a couple models:
(Belovsky and Slade 2002)
Neither model explicitly incorporates the fecal nutrient cycling pathway. They also don't incorporate inducible plant defenses such as secondary compounds. Plants must balance tradeoffs when inducing increased levels of secondary compounds in their tissues because, while these compounds might slow herbivory they might also slow decomposition, ultimately decelerating nutrient cycling. The rate of nutrient cycling is a key determinate of many ecosystem functions such as NPP.
Bardgett and Wardle 2003