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.