Stand thickness of dominant tree species in the State Forests divided into stand age classes over the years 2014-2018

Changes compared to version 1.0:

The data has been cleaned and organized using OpenRefine. A column with the average age of trees was added for each type of dominant tree species.The data has been cleaned and organized using OpenRefine.
A column with the average standing timber volume on afforested forest lands was added for each type of dominant treespecies
The dataset contains data illustrating changes in the distribution of dominant tree species in the State Forests divided into stand age classes over the years 2014-2018. Dominant species can be defined as the species in the stand with the largest share in terms of area, thickness or number. Stand thickness means the gross thickness of the timber, i.e. the thickness of trunks and branches with a thickness of at least 7 cm at the thinner end when measured with bark.
It should be noted that this only concerns forests managed by the State Forests National Forest Holding.  the span of the age class is 20 years (e.g. age class I – tree stands up to 20 years old, class II – 21 – 40 years, class III – 41 – 60 years, etc.). The average age is determined as a weighted average, with the area in individual age classes and subclasses taken as the weight. The term forest area refers to the area of forests excluding land related to forest management. The main source of information for the study is the Forest Data Bank (www.bdl.lasy.gov.pl).
The dominant tree species included in the dataset are:

So - pine
Św - spruce
Jd - fir
Bk - beech
Db - oak
Gb - hornbeam
Brz - birch
Ol - black alder
Tp - poplar
Os - aspen