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.
A~ ~nergy budget was developed for Odontopus calceatus feeding on fresh Lmodendron tullp1/era leaves. Calorific content was determined for both weevil biomass a~d weevil f~ces. Food consump~io~ was estimated to be 97% of dry body weight per day with ~n ~gestwn rate of 45%. Assimilation was 50% of both dry matter and of energy per day. Respiration of 0. cc:Jceatus ~as 0.88. cal per milligram of dry weight per day at 27° C. Based ~>n these data and mformat10n on field population biomass for a Liriodendron forest ( 1965 m East Tennessee), canopy consumption was estimated at 1.9% (17.7 Kcal/m 2 ).
Smelter emissions (baghouse dust) and contaminated litter were applied to intact forest microcosms to determine effects of heavy metals on litter-soil carbon metabolism. Daily efflux of gaseous CO2 was monitored during the experiment. After 20 too, microcosms were harvested and effects on soil biota were determined.Heavy metals increased daily CO2 efflux rates and cumulative gaseous carbon loss. In addition, seasonal patterns of CO2 efflux rates were altered. Soil bacterial density was significantly increased at the expense of soil fungal biomass.Nondestructive monitoring of CO2 efflux provided an early indicator of smelter emission effects on soil biota. Effects on C metabolism may be detected prior to effects on communities or populations within chemically contaminated ecosystems.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.