Facts about the survey Quality of Regrowth
The purpose of this statistical product is to describe the quality of regrowth from the point of view of production. The results come from the inventory on regeneration monitoring. The inventory aims to supply data for continuous follow-up of the forest policy's environmental and production goals for regeneration felling and regeneration.
Since the early 1960s, the Swedish Forest Agency has been collecting information on the quality of regrowth. We have followed up on environmental considerations in regeneration felling since the early 1990s. In order to expand the possibilities of analysis and create a more rational inventory system, we merged these follow-ups into a system, called R-Polytax, in 1998. R-Polytax has been conducted throughout the country with annual inventories from 1999. We revised the system in 2008 and changed our name to Polytax. However, the term "Polytax" has been considered difficult to understand for outsiders and as of 2015 the new term "Quality of the regrowth" applies.
The purpose of the statistics
The purpose of the inventory is to provide data for continuous follow-up of the forest policy's environmental and production goals in connection with regeneration felling and regeneration. The purpose of this statistical product is to describe the quality of regeneration from the point of view of production. Further results from the inventory can be found in the statistical product Environmental considerations in regeneration felling.
Information needs of users of statistics
The statistics are mainly a strategic basis and users are entrepreneurs in forestry, researchers in forest regeneration and investigators at various authorities such as the Swedish Forest Agency, the Swedish Environmental Protection Agency and the Swedish National Heritage Board.
The statistics includes
- Proportion of harvested area regarded as in compliance with Section 6 of the Forestry Act (SVL).
- Used regeneration methods presented as a percentage of harvested area.
- Scarified area presented as a percentage of harvested area.
- The average density of the regeneration is presented as the number of main stems per hectare divided by tree species and tree groups.
- We report the results with a breakdown by owner class, part of the country, regeneration methods.
Definitions and explanations
Regions:
- Northern Norrland = AC and BD counties
- Southern Norrland = Z, Y and X counties
- Svealand = AB, C, D, U, T, S and W counties
- Götaland = E, H, K, G, F, I, O, N and M counties
Owner categories
- Individual owners = natural persons, estates of deceased persons and companies that are not stock companies.
- Others = the state, state-owned stock companies, other public owners, privately owned stock companies and other private owners
The regeneration is classified as approved if:
- the number of main plants is at least the number per hectare (at a certain site index) as said in the Section 6 of Forestry Act (1979:429), and
- the gap between the main plants is less than prescribed in the law.
More details can also be found in the inventory instructions. The inventory instruction is similar to, but not exactly the same as, the instruction for supervision under the Forestry Act. The inventory instruction is not in English.
Planting
Planting on an area with or without seed or shelter trees.
Natural regeneration
All natural regeneration with or without seed trees/shelter trees with the aim of rejuvenating naturally.
Seeded
Sowing with seeds on area with or without seed- or shelter trees.
No action
No soil preparation or other active regeneration measures have been taken.
How we make the statistics
The inventory is based on a random sample conducted from all the reports of notified areas of final felling and applications for permits for final felling of montane forest. The survey of regeneration areas is based on PPS random sampling (Probability Proportional to Size).
During the inventory season 2022/2023 472 object, stratified in 22 districts and by individual land ownership class and others, where visited.
Estimates for the inventory seasons 2020/2021 – 2022/2023 are based on a gross sample of 1,416 objects, of which 1,363 objects were inventoried.
The population consists of all final fellings larger than 0.5 hectares, with the exception felling of valuable broad-leaved forests.
The inventory is conducted by approximately 35 of the Swedish Forest Agency's forest consultants five years after harvesting in southern Sweden and seven years after in northern Sweden. The quality of the regrowth is then evaluated in relation to the requirements of the Forestry Act.
Reliability of statistics
Reliability is considered overall to be high. The results are presented as three-year averages to give sufficient quality at the regional level. Since the inventory is a sample survey the results are, however, affected by sampling error. In addition to random error there may also be other types of error sources, such as registry errors, measurement errors, etc.
These sources of error are minimized through built-in validation checks in the registration application as well as regular calibration exercises in the field. According to the Swedish Forest Agency's environmental management system, all inventors must take part in at least one calibration exercise per year.