3.1 | Environmental data
We first present seasonal variations of the precipitation, PPFD,
temperature and VPDZ in 2012 and 2013, which were
typical of boreal forests (Figure 1). The annual mean temperature during
2012 and 2013 was 1.6 °C and 3.3 °C, and the total precipitation 796 mm
and 542 mm, respectively. Precipitation was relatively high during the
thermal growing season limiting the potential for drought during the
growth period. The light level increased almost three months before the
start of the thermal growing season and the maximum values were in June
before they decreased until winter. The temperatures were the highest in
July-August and reached very low values in winter. Temperatures stayed
below zero for several months. Finally, VPDZ was highest
during the thermal growing season although its increase started around
March for both years. VPDZ showed high variability over
the whole year.