Estimation of fluxes and resorption
The site fluxes of C, N and P through insect herbivores (Xherb, g m-2 yr-1) was estimated as the product of the leaf production (LP, g m-2 yr-1), proportion of the leaf area lost to herbivory (H), and the elemental proportions in the green leaves collected in the early growing season ([Xgreen]):
Xherb = LP x H x [Xgreen]
Similarly, the flux of elements through the litter (Xlitter, g m-2yr-1) was estimated as the product of the leaf production (LP, g m-2 yr-1) corrected for the proportion lost to herbivory (H), and the elemental concentrations in the senesced leaves collected in the late growing season ([Xsen]):
Xlitter i = (1-Hi) LPi x [Xsen]i
Foliar nutrient resorption (Xresorp, %) was calculated according to van Heerwaarden et al. (2003). Briefly, it was estimated as the difference in nutrient concentrations between the green and the senesced leaves normalised to leaf area, and expressed as a fraction of the green leaf nutrient content. Nutrient resorption needs to be accounted for, when comparing fluxes based partly on green leaves (herbivore deposits), and partly on senesced leaves (leaf litter), as strong resorption amplifies the relative importance of the green-leaf component, i.e. the herbivory-mediated flux.