Activities

• To compile site information, micrometeorological (i.e., air temperature, relative humidity, vapour pressure deficit, precipitation), atmospheric CO2 and N deposition data for the last 50 years;
• To identify common years with climate extremes across sites, with particular reference to drought and heatwaves.

• To compile flux data from the start of the monitoring;
• To calculate ecosystem water-use efficiency

The two main tasks of this WP are sampling wood cores from trees and sample preparation for stable isotope analyses.

Fieldwork. Wood cores will be sampled from 15 dominant and co-dominant trees per site.

Larbwork. Classical dendrochronological measurements will be carried out by using CooRecorder (Cybis Elektronik and Data AB, Sweden) and CDendro (Cybis Elektronik and Data AB, Sweden). Of the 15 trees, 5 will be chosen for the measure of stable carbon (δ¹³C) and oxygen (δ¹⁸O) and nitrogen (δ¹⁵N) isotope compositions. We will focus on the last 30 years, so to include the time window where eddy covariance data are available at most of the sites.

Intra-annual measure of δ13C and δ18O will allow to ‘follow the season’ and depict the divergence i) in the physiological signal at the tree level, respect to the optimal conditions (before the occurrence of the climate extreme) and ii) between tree and ecosystem responses. Three trees (different from those used already in WP3) will be chosen to carry out intra-annual measure of both δ13C and δ18O by using the Laser Ablation (LA)-combustion line coupled to an IRMS on the selected temporal windows that will contain the climate extreme as identified in the WP1.