Modeling nitrogen flux by larval insect herbivores from a temperate hardwood forest

Abstract

Herbivorous insects flux considerable amounts of nitrogen from the forest canopy to the soil in the form of frass. The amount of nitrogen fluxed varies depending on the characteristics of the herbivores, their food resources, and their physical environment. We used concepts from metabolic ecology and ecological stoichiometry to develop a general model of individual nitrogen flux via frass fall for moth and sawfly larvae from a temperate hardwood forest in northern Wisconsin, USA. We found that individual nitrogen flux (Q(N), mg N/day) was related to larval body mass (M(B), mg dry), short-term variation in environmental temperature (T, K), and larval nitrogen concentration (N(B), proportion dry mass) as Q(N) = e(25.75) M(B)(0.77) e(-0.83/kT) N(B)(-1.56), where k is Boltzmann's constant (8.62 x 10(-5) eV/K). We also found that larval nitrogen flux did not vary with the nitrogen concentration of food, and suggest that this was due to compensatory feeding by larvae living on low-quality leaves. With further work, models of individual N flux could be used to scale individual fluxes to population and community levels, and thus link the characteristics of insect herbivore communities with the flow of nitrogen through forested ecosystems.

Mass invariance of population nitrogen flux by terrestrial mammalian herbivores: an extension of the energetic equivalence rule

“…1997; Vanni et al. 2002; Anderson & Jetz 2005; Meehan & Lindroth 2007). Thus, it is quite possible that general elemental equivalence will hold across several types of organisms.…”

“…2002) and nitrogen (Wen & Peters 1994; Vanni et al. 2002; Hobbs 2006; Meehan & Lindroth 2007) fluxes scale approximately as mass to the ¾ power. Several other studies have demonstrated that population density scales approximately as mass to the negative ¾ power (Damuth 1981, 1987; White et al.…”

Effect of Body Size on Expression of Manduca sexta Midgut Genes

“…Compensatory responses, such as increased expression of midgut amino acid transport proteins, might be necessary to maintain metabolic rate in larger animals, especially if nitrogen uptake is closely linked to metabolic rate. This link is supported by similar scaling exponents for nitrogen excretion and metabolic rate in larval lepidopterans (Meehan and Lindroth, 2007). Also, fifth instar Manduca larvae showed the lowest growth efficiency on low-protein diets, suggesting that protein assimilation may be particularly difficult for the largest instar (Ojeda-Avila et al, 2003).…”

Responses of symbiotic N2 fixation in Alnus species to the projected elevated CO2 environment

“…The leaf litter C/N ratio decreases rapidly from 20 to 12 in A. hirsuta (Tobita et al 2013a) and from 20.5 to 15 in A. japonica (Yoon et al 2014), suggesting that litter decomposition immediately moves into the mineralization stage (Takeda 1998). Another feature of Alnus species is the high susceptibility of leaves to herbivore damage (Kikuzawa et al 1979;Tadaki et al 1987;Tobita et al 2013a), and their feces are a N input pathway to soils (Meehan and Lindroth 2007). In addition, symbiotic N 2 fixation in Alnus species may affect the distribution patterns of regenerated tree species (Tobita et al 2015) and diversity (Hanley et al 2006) as well as improve soil fertility.…”