Asa High-yield Experimental Forest

Last changed: 01 November 2022
We place constantly increasing demands on the forest

Asa High-yield Experimental Forest is a world-unique large-scale research arena on intensive forestry. Production possibilities together with effects on the environment are being measured and evaluated. The goal is to increase forest growth by 50%.

Many demands on the forest

Forests play a critical role in sustainable development. The view of what services the forest should provide is changing and demands are increasing. Forests supply wood that is used for building houses, making paper, furniture, energy, textiles, etc. At the same time, there is a demand from society to provide recreational services and protect biodiversity. Simultaneously forests play a key role in mitigaiting climate change. Does this sound like an impossible equation? One solution may be to significantly increase forest growth in certain areas.

The purpose of Asa High-yield Experimental Forest is to create an arena where studies of the effects of signigficantly increased forest growth at the landscape level are made possible.

Increasing forest growth

Various silvicultural practices and management programs are used to increase growth, eg.:

  • demand-driven fertilisation of spruce stands (fertilisations take place in the spring every second year since 2010)
  • use of introduced fast-growing tree species such as hybrid larch Larix x marschlinsii and lodgepole pine Pinus contorta
  • best available genetically improved seeds and seedlings
  • improved regeneration methods
  • adapted thinning programmes and rotations.


Forest growth, vegetation changes, water chemistry and runoff are being monitored at the Asa High-yield Experimental Forest.

Water is sampled monthly in 12 catchment areas, and samples are analysed with an extensive water chemistry program. Water flow is continuously measured and the hourly average value is recorded. The water control program is further expanded after every fertilisation.

Vegetation changes are monitored through airborne laser scanning and a network of permanent sample plots where trees as well as ground- and field-layer vegetation are inventoried.


Research Topics

The High-yield Experimental Forest in Asa is an unique arena for research on increased forest growth, timber production and environmental effects. Our infrastructure enables studies of eg.:

  • the impact of fertilisation on water quality at the landscape level
  • recreational values in intensive forestry
  • impact of introduced tree species on native flora and fauna.

If you have questions or research ideas, do not hesitate to contact us!

We offer you

  • Data, read more below.
  • The opportunity to set up new experiment on intensive forestry.
  • Equipment, electricity supply, help from our research engineers and experiment technicians.
  • Office and laboratory with various facilities, read more under Asa research station

Available data

Climate data from Asa climate station (since 1990)

Climate data at Asa climate station includes:

  • air and soil temperature
  • relative humidity
  • global radiation, net radiation, photosynthetic photon flux density (PPFD)
  • precipitation
  • wind speed and direction
  • atmospheric pressure

Data from Asa climate station and stations at other experimental forests is available here

Water chemistry data

The samples are analysed by SLU's Geochemical Laboratory (unless otherwise noted), read more about methods, accreditation, measurement range and uncertainty etc. here

For data, contact:

Magdalena Zuchlinska Steen, Experiment Technician
Unit for Field-based Forest Research; Asa, +46 472-263181

Monthly water chemistry from 12 catchment areas

The analysis includes 23 parameters since mid-2010: pH, alkalinity, conductivity, two different absorbance values, suspended material content, turbidity (from mid-2010 to 2014), total organic carbon, total nitrogen, ammonium, nitrite nitrate, total phosphorus, phosphate phosphorus, sulphate, chlorine, fluorine, calcium, magnesium, sodium, potassium, iron, manganese, silicon, aluminium

Water chemistry from extended sampling after fertilization

Water sampling is additionally extended after every fertilisation in all catchment areas affected by the fertilisation and also in two control areas. After fertilisation water is sampled every- or every second day after fertilisation (4-5 times) and also during the coming summer at high water flow.

Water chemistry data from extended sampling after fertilizations includes: total nitrogen, ammonium, nitrite nitrate, phosphate phosphorus, total phosphorus.

Extended sampling in 2014 within the FutMon project

Water sampling from our two reference catchment areas took place twice a month.

Monthly water analysis from our two reference catchment areas included the following heavy metals: arsenic, cadmium, cobalt, chromium, nickel, copper, lead, vanadium, zinc, uranium, methylmercury (IVL), total mercury (IVL).

Mercury was analysed by Swedish Environmental Research Institute (IVL), read more about analysis methods, accreditation, measurement range and uncertainty etc. here

Stream discharge data

  • Manual measurements (control):

    • once a month from mid-2010 to mid-2015

    • twice a month from mid-2015

  • Automatic measurements (logger) - hourly average value from mid-2012 (except for winter periods, read more below)

Manual measurements of water flow are made at weirs, the distance from the weir’s edge to the water surface is measured on both sides (see picture below). It is also noted whether water flow is influenced.

Sketch of manual flow measurement method

For automatic level measurements, Level Troll 7 loggers are used. Loggers measure the water flow and temperature every two seconds and save the hourly average value. Data is loaded twice a month (data cannot be viewed in real time).

During three winters 2017/2018, 2018/2019 and 2019/2020, the loggers were stored inside - for those periods, data is only available from one reference stream (weir equipped with a shed and infrared heating).

Quality control of water flow data is in progress.

V-notch flume at Asa

For data, contact:

Magdalena Zuchlinska Steen, Experiment Technician
Unit for Field-based Forest Research; Asa, +46 472-263181

Airborne laser scanning data

Airborne laser scanning data

Asa Experimental Forest and Asa High-yield Experimental Forest were scanned with airborne laser in 2009 and 2019. On both occasions, it was high point density scanning, approx. 20 points/m2, which enables the identification of individual trees. In connection with the scans, the areas have also been photographed aerially.

  • Laser scanning 2009. Laser data in various formats. Processed data in the form of classified laser data, digital height model, and calculated standing volume, average height and canopy height. The aerial photos are rectified and are available in two resolutions, 5 and 10 cm pixels.
  • Laser scanning 2019 with two different wave lengths (green and infrared laser). Data processing is in progress. Financed by project Mistra Digital Forest.

For data, contact:

Mikael Andersson, Group Manager
Unit for Field-based Forest Research; Asa, +46 472263170

Tree data from production sample plots

Tree inventories within a network of 234 permanent sample plots within Asa Experimental Forest and Asa High-Yield Experimental Forest constitute reference data for the two laser scanning carried out in 2009 and 2019. The network was established and GPS-positioned in connection with the 2009 scanning when all stands within area were divided into five layers depending on tree species and age. The size of the sample plot varies depending on age and condition of each stand.

The variables measured/registered at every sample plot:

  • Breast height diameter (all trees)
  • Tree species (all trees)
  • Height (some trees randomly chosen to represent all diameter classes)
  • Tree position within sample plot (all trees; during the second inventory)

For data, contact:

Mikael Andersson, Group Manager
Unit for Field-based Forest Research; Asa, +46 472263170

Vegetation inventory

In 2018, vegetation was inventoried on all samples plots used for tree inventory (234) and on additional 40 sample plots distributed over fertilised stands. On the subplot area of 1m² all occurring species and their percent of cover were registered in three layers: bottom layer (e.g. mosses), field vegetation layer (grass, herbaceous plants) and shrub layer. Tree canopy cover above the sample plot was also registered.

For data, contact:

Mikael Andersson, Group Manager
Unit for Field-based Forest Research; Asa, +46 472263170


  • Located next to Asa experimental forest and Asa research station
  • Established in May 2009
  • Landowner: Sveaskog
  • Covers 1,700 ha of which 1,485 ha is productive forest land
  • The height above sea level: 170-240 m
  • The average site quality: 8.1 m3sk / ha and year.
  • Tree species mixture: spruce 72%, pine 23%, deciduous trees 5%

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