Analysis of Insect Consumption in a Forest Conopy

Abstract

A mathematical model has been developed for estimating the consumption of canopy vegetation by insects. The model divides canopy leaves into age classes according to time of leaf emergence. Periodic measurements were made of gross leaf area and hole area initiated by insect consumption for each generation. Gross area distributions were used to determine empirical growth functions for the canopy vegetation. The rate of change in hole area is a function of both insect consumption and subsequent hole expansion due to leaf growth. The hole expansion rate was determined empirically by punching holes in known area in growing leaves and correlating hole expansion with leaf growth. From these relationships, a linear differential equation was derived to describe the dynamics of insect grazing in the canopy. This model was used to interpret the effect of insect herbivory on the dry matter and nutrient cycles in a Liriodendron tulipifera forest. Average herbivorous insect consumption over 3 years was equivalent to 2.6% of the net primary production of foliage biomass but represented an annual loss of 7.7% in photosynthetic surface area.

Stoichiometric relationships among producers, consumers and nutrient cycling in pelagic ecosystems

“…Two aspects of ecosystem structure which likely magnify the importance of the stoichiometry of herbivore species are 1) the quantitative importance of herbivores in nutrient supply relative to all other potential sources, and 2) a high herbivore biomass relative to plant biomass. In temperate forests, summertime nutrient cycling can be dominated by frass fall from insect herbivores (Reichle et al 1973). Given that herbivorous arthropods disproportionally accumulate certain elements relative to others (Weiss & Berenbaum 1989), we speculate that insect herbivores might also induce qualitative changes in resource supply ratios similar to those described here for zooplankton.…”

The influence of plant carbon dioxide and nutrient supply on susceptibility to insect herbivores

“…The amount of herbivory among species in communities has been estimated to commonly be about 10~, but is sometimes as high as 50 or 60~o of the leaf area removed (Reichle et al 1973;Fox & Morrow 1983). Thus, leaf-eating insects can have a significant, direct impact on plant carbon budgets because they consume photosynthetic tissue and consequently directly reduce carbon income.…”

Vertical profile and canopy organization in a mixed deciduous forest

“…1986). However, early abscission and canopy herbivory are low in forests similar to the one studied: average annual leaf area lost over three years in a Tennessee Liriodendron forest was 5-10~o, which included both herbivory and the expansion of leaf holes (Reichle et al 1973). If 10~o of leaf area were lost then the maximum LAI of this stand would be 5.84.…”