Fluctuations in gross volume increment estimated by the Lithuanian National Forest Inventory compared with annual variations in single tree increment

One may observe significant inter-annual fluctuations of living trees growing stock volume changes estimated by Lithuanian National Forest Inventory (NFI). In current study, we compared two sources of information on forest productivity: conventional NFI data and dendrochronological data based on tree cores collected in parallel with the measurements of the 4th Lithuanian NFI cycle during 2013-2017 on the same permanent plots (total number of cores was 4967). The main message of this study is that the dendrochronological basal area increment data confirm the depression of gross stand volume increment around the 2006-2007 (based on Lithuanian NFI measurements in 2008-2009), followed by steep increment increase during 2008-2011 (NFI from 2010-2013). We discuss that the findings explain the differences between projected growing stock volume change, which has been used for forest reference level estimation according to LULUCF regulation, and the one recently provided in National Greenhouse Gas Inventory Reports.