• ecosystem dynamics
• carbon cycle
• critical zone
• alpine grasslands
• accumulation chamber
• global change

This kind of study aims to evaluate the role of alpine ecosystems such as high altitude prairies in defining carbon budgets of the atmosphere, clariyifing the effects of its main environmental drivers and exploring the dynamics which regulate its entity through in situ observations. In this work, a suitable instrumental and experimental design, aimed to define the role of different physical and biological structures in the site under study, is illustrated.

In order to reach this scope, a series of surveys have been taken during the 2018 vegetative season in a prairie located at “Col del Nivolet”, at the average altitude of 2700 m a.s.l. in the Gran Paradiso national park (Italy). Carbon dioxide flux has been estimated thanks to a static non-stationary flux chamber, connected to a fluxmeter equipped with a CO2 infrared (IR) detector. An array of other environmental and meteorological parameters, such as solar radiation, air temperature and relative humidity, soil temperature and volumetric water content, as well as geographic coordinates, have been recorded through a blue tooth connected to the IR spectrophotometer in a synchronized fashion. Soil samples have also been collected, in order to characterize some main pedological features such as organic matter content and pH.

The experimental design included two sequential measures: a first measure at normal light conditions, allowing photosynthetic processes to take place and estimating the net ecosystem exchange (NEE) between photosynthesis and respiration, and a second measure, perform by completeley covering the transparent chamber and measuring only fluxes emitted due to ecosystem respiration.

Measurements took place in spots representing the vegetational diversity of the different sites, around an area of approximately 225 m2 for each plot. At each single point, two sequential measures in the two different conditions were recorded. Four plots were chosen because of their different geological and vegetational features. Photographic documentation was recorded at each point for documenting the status of vegetation during different stages of vegetative season.

The fluxmeter allows to record the concentration of CO2 inside the flux chamber vs time, and to calculate the slope of the ‘concentration vs time’ regression curve, during its linear phase, i.e. the initial phase after the end of the system indertial adjustment, when the concentration change inside the flux chamber does not influence the diffusion of the gas inside the chamber significantly. Given the linear accumulation model of Chiodini et al. (1998) we calculated the flux thanks to the following formula:

Where is the recorded slope of the curve, is the height of the chamber and is the CO2 flux. Also Pearson correlation coefficients (R2) for the same curve were collected.

Collected data were adjusted by using a calibration regression model, which gives back flux values in standard conditions. In order to estimate the real final flux, we applied the ideal gas law by using experimental temperature and pressure.

The photosynthetic gross primary production (GPP) has been then calculated, according to the formula:


Before the field surveys, we tested the suitability of our specific intruments with respect to others, testing the effectiveness of the air mixing method inside the chamber and the suitability of the use of a 2 cm portable metal collar as external support in order to avoid air infiltrations at the interface between soil and chamber.

We also improved the scheme of measurement on the specific environment: given a variability coefficient for a bunch of measures, we calculated the minimum number of repetitions in order to give a good estimate of the average flux.

We also carried out a number of laboratory tests at low flux regimes by performing flux measures on controlled gas fluxes, obtained thanks to a Mass Flow Controller, proving the suitability of this method for detecting low entity fluxes and estimating them through linear accumulation model.


Finally, we elaborated values for Re, NEE and GPP from data collected at Nivolet during the vegetative season of 2018, and we have been able to plot seasonal distributions of values for the fluxes.

By including a description of pedological features and future monitoring of the vegetation, this work aims to set out a complete scheme for the monitoring the mountain Critical Zone, which would aim to clarify feedbacks at a multiple scale occurring in the external layer of the Earth crust, where biosphere, atmosphere and geosphere interact and support ecosystem services. This work is carried out in the frame of global change studies by using Earth observation and has been conducted as a part of the H2020 project ECOPOTENTIAL.