A newly established FLUXNET site for monitoring energy exchange and carbon budgets of agricultural cropping systems in Southern Italy

Gaseous emissions in the atmosphere in relation to anthropogenic activities are a growing menace for the environment at the planetary level. Agriculture and forestry may play a positive role by substituting biomasses to fossil hydrocarbons as a source of energy and via sequestration of carbon in the terrestrial sinks. Monitoring C dynamics in agricultural systems is an urgent priority in view of compiling national inventories of emissions and sinks. Due to the considerable incidence of arable land on emerged lands, the lack of directly measured data contribute to present uncertainties in the assessment of global C budget. The present experiment is aimed at monitoring CO2 and H2O net exchange of an irrigated agricultural system in the course of several growing seasons, in a farm sited in Eboli (Salerno). Alfalfa is presently grown, at its fourth year from establishment. Continuous monitoring of fluxes was started in July 2002 and will be continued throughout all stages of growth. Following, the sod will be cultivated and new crops established, so that C exchange in response to cultivation and management patterns will be evaluated. The eddy covariance flux monitoring apparatus has an open type configuration. A secondary station, logs at a frequency of 1 Hz the environmental variables needed to check energy balance closure and to model NEE response to environment. By adopting the Bowen ratio approach, an independent estimate of fluxes is made - to backup data during eddy station downtimes. Seasonal C budget are checked by destructive samplings of aerial and below-ground biomass. The relevant soil and canopy variables - according with the EC CARBOEUROFLUX project database - are determined at periodical intervals. By the mean of a labelling technique (14C), soil carbon budget will be reconstructed via small scale experiment on monoliths. The combination of direct flux measurement and stable isotopes determinations (13C) allows for partitioning of the different ecosystem factors of C budget. Concurrent CO2 air concentration and isotopic composition will be used to assess sources and sinks of CO2 of the system, adopting the well-known Keeling plot theoretical approach.