Net ecosystem exchange

Effect of vegetation and irradiance on net ecosystem exchange in (a) forests and (b) crops (reproduced by permission of Academic Press from Aiiv. Ecol. Res., 1996, 26, 1-68). 

Net-Ecosystem-Exchange-NEE Net-Ecosystem-Productivity-NEP (= change in litter organic layer)... 

Hunt, E. R. Jr., Piper, S. C., Nemani, R., Keeling, C. D., Otto, R. D. and Running, S. W. (1996). Global net carbon exchange and intra-annual atmospheric CO2 concentrations predicted by an ecosystem process model and three-dimensional atmospheric transport model. Global Biogeochem. Cycles 10, 431-456. 

Wang W. Davis K.J. Cook B.D. Bakwin P.S. Yi C. Butler M.P. and Ricciuto D.M. (2005b). Surface layer C02 budget and advective contributions to measurements of net ecosystem-atmosphere exchange of C02. Agricultural and Forest Meteorology, 135(1 -4), 202-214. 

Bowling D. R., Tans P. P., and Monson R. K. (2001) Partitioning net ecosystem carbon exchange with isotopic fluxes of CO2. Global Change Biol. 7(2), 127-145. 

Table 18.4 Summary of Net Sediment-Water Oxygen and Nutrient Exchanges and Flux Ratios from 48 Estuarine and Coastal Ecosystems Developed by Bailey (2005)...

Land net exchange of carbon between terrestrial ecosystems and the atmosphere... 

In the context of saltmarsh/coastal flux studies, a flux is the net exchange of a substance between these two ecosystems. The fluxes of several types of material, including nutrients, trace metals, herbicides and radionuclides, have been studied by researchers. Although this paper primarily appraises the methodology of nutrient flux estimations, many of the problems are also shared by researchers working on other types of material fluxes. 

In order to understand how H2O and CO2 are exchanged between leaf tissues and the air, measurement of the photosynthetic isotope fractionation by open flow gas analysis is conducted in a gas exchange chamber under controlled conditions of temperature, light intensity and humidity, and CF-IRMS and GC are employed. " When the same method is applied to ecosystem isotope fractionation in a field experiment, the variation in atmospheric CO2 concentrations and S values primarily reflect variations in net photosynthesis (daytime) and respiration. The S and CO2 data also reflect these processes, but with added complications because of oxygen isotope exchanges with soil and leaf water pools. 

There appears to be a potential for deposition of elemental mercury via plant-leaf uptake. Lindberg et al. (1992) indicated that forest canopies could accumulate elemental mercury vapor, via gas exchange, at the leaf surface followed by mercury assimilation in the leaf interior during the daylight hours. However, Hanson etal. (1995) indicated that this would only occur when air concentrations of elemental mercury were above an equilibrium level for the local forest ecosystem. Therefore, dry foliar surfaces in terrestrial forest landscapes may not be a net sink for atmospheric elemental mercury, but rather a dynamic exchange surface that can function as a source or sink dependent on several factors. 

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