This indicator shows the state of forests in view of growing stock, increment and fellings, which all reflect forest management. The data on growing stock and increment are presented for the period 1947–2010, while the data on fellings are presented for the period 1991–2013.

According to FAO, the subindicators are defined as follows:

Growing stock: Volume of all living trees with bark that have more than a certain diameter (X cm) at breast height (or above any irregularities in the trunk). This includes the stem from ground level or stump height up to a given top diameter (Y cm), and may also include branches above the minimum diameter (W cm). In Slovenia, the diameter threshold (X) is 10 centimetres, so all trees thicker than 10 cm are counted as growing stock. The minimum diameter (Y) is 5 centimetres. Branches are not included as growing stock.

Increment: Average annual volume of incremental growth over the reference period with tree diameter measured at breast height (or above any irregularities in the trunk). This includes the increment of trees that have been felled during the reference period.

Fellings: Average annual volume of all trees, living or dead, measured overbark that are felled during the given reference period, including the volume of trees or parts of trees that are not removed from the forest.

Throughout history, growing stock has been a key indicator of the state of forests. Information on growing stock is indispensable for understanding the dynamics and production capacity of forests. It is the basis for the development of national policy and strategy for the sustainable use of forest resources.

Together, growing stock, increment, felling, forest area and allowable felling constitute a basic set of indicators used to monitor forest dynamics. In addition, these indicators are the basis for conducting estimates of biomass and carbon contained or stored within a certain forest. For this reason, information pertaining to how these indicators change over time is extremely important.

We are pleased to note that from the viewpoint of growing stock and increment, Slovenian forests have been improving for decades. This is mainly due to systematic forest management, and partly a consequence of changes in the methodology of determining what constitutes growing stock (ocular estimation – control sample method).

Increment percentages in Slovenian forests are kept at a steady level compared to the growing stock. The allowable cut, whose implementation was only 75% in the last decade, also follows this trend.

According to reports by the Slovenia Forest Service for 2014, growing stock amounts to 289 m³/ha, increment is 7.17 m³/ha and annual allowable felling volume is 3,923,995 m³. Over the past 60 years, growing stock per hectare and increment have increased by 130%, while the volume of felling fluctuated between 2 million m³ (in 1991) and almost 4 million m³ (in 2013), which represented between 100% of increment in the 1950s and less than 40% in the beginning of the 1990s. Today, the volume of felling amounts to approximately 50% of increment. The reason for such accumulation of growing stock in Slovenian forests and such increment fluctuation is effective forest management.

When speaking of growing stock, increment or fellings, one must also indicate the structure by tree species and broader categories (coniferous and deciduous trees). The ratio between coniferous and deciduous trees changes constantly and was increasing in favour of coniferous trees until 1961, when the percentage of conifers was 58%. After 1961, the percentage of conifers began to decrease and, in 2000, it dropped under 50%.

Fellings reflect the economic and social use of forest resources in the national economy and the dependent local communities. They contribute to the monitoring of the sustainable use of forest resources by comparing actual wood removal with sustainable wood removal.

According to the FAO Global Forest Assessment Study, the growing stock and increment in Slovenian forests in 2005 were much larger than in the rest of Europe.

In Slovenia, as well as in Europe (the EU-27), trends of increasing growing stock and increment have been observed. In 1990, the fellings in Europe were reported to be 378,651,600 m³, in 2000 443,649,000 m³ and  in 2005 441,995,300 m³. A slightly positive trend with fluctuations between individual years is noted in the majority of European countries, the main reasons being the increase in forest areas and the increase in increment. Fellings are strongly influenced by the market, which explains the significant variation between individual years. The ratio between fellings and increment is low and constant.

In Slovenia, we expect development to follow the guidelines stated in the National Forest Programme. Further planned forest management will allow Slovenia to get closer and closer to the optimal average growing stock, which is 320–330 m³/ha. In order to achieve that, further moderate and selective accumulation of increment will be required. Therefore, we anticipate that development will grow in the direction leading to the attainment of this qualitative goal.