Asa high-yield experimental forest

Many demands on the forest

The demands on the forest are increasing and becoming more varied. The forest can provide timber used for building houses, making paper, furniture, energy, textiles, etc. At the same time, we want to protect biodiversity, use the forest for recreation, and the forest plays a key role in mitigating climate effects. Does this sound like an impossible equation? One solution could be to significantly increase timber production in certain areas. The purpose of the high-yield experimental forest is to study the effects of increased timber production at the landscape level by applying the results from previous research.

How do we increase growth?

To increase growth, various management measures and programs are used, such as:

• Need-based fertilization in spruce stands (fertilization is done in the spring every other year since 2010)
• Use of introduced fast-growing tree species like lodgepole pine and hybrid larch
• The best available improved plant material
• Improved regeneration methods
• Tailored thinning and rotation periods

Why do we aim to increase growth?

The forest is important. We use wood to build houses, produce paper, furniture, and energy, as well as textiles. From a climate perspective, it makes sense to reduce the use of fossil fuels and concrete in favor of renewable wood products.

In 2008, the Swedish government tasked the Swedish University of Agricultural Sciences (SLU) with investigating the possibilities for intensive forest cultivation. The investigation concluded that if abandoned agricultural land and forest areas with low natural value were used for intensive cultivation, the annual timber harvest could increase by 36 million cubic meters (in 2012, Sweden's annual harvest was 85 million cubic meters).

So, on one hand, we want to produce more timber, but on the other hand, the demands to protect biodiversity and continue using the forest for recreation are increasing. To meet the rising demand for biomass, one solution could be to significantly increase production in certain areas. To evaluate the production potential in Swedish forests, large-scale experimental areas are needed.

This is the purpose of the high-yield experimental forest – to study the effects of intensive forestry on a landscape level. The goal is to increase timber production by 50% by applying results from previous research while monitoring and evaluating the environmental effects of the intensive management.

Environmental Monitoring

Within the high-yield experimental forest, monitoring of forest production, vegetation changes, water chemistry, and runoff is ongoing.

Water sampling is conducted monthly in 12 catchment areas. The samples are analyzed using a comprehensive water chemistry program. Continuous flow recording takes place, and average hourly values are saved. After each fertilization event, the water quality control program is expanded.

Vegetation monitoring is carried out through laser scanning of the area, as well as a fixed network of sample plots where trees and ground vegetation are inventoried.

Research Opportunities

The high-yield experimental forest in Asa is a unique research arena for intensive forestry, focusing both on timber production and the environmental effects of intensive management. We have the infrastructure to enable studies on topics such as:

• The impact of fertilization on water quality at the landscape level
• Recreational value in intensive forestry
• The impact of non-native tree species on flora and fauna
• If you have any questions or research ideas, don’t hesitate to contact us!

Available Data

Climate Data from the Asa Climate Station

Climate data at the Asa climate station includes:

• Air (1.7 and 0.25 m) and soil temperatures (10 and 20 cm)
• Relative air humidity
• Global (SR), net (NR), and photosynthetically active (PPFD) radiation
• Precipitation
• Wind speed and direction
• Air pressure

Data from Asa and other experimental stations is available here.

Water Chemistry

Base program from 12 catchment areas

Monthly water chemistry from 12 catchment areas since mid-2010.

The analysis includes 23 parameters: pH, alkalinity, conductivity, two different absorbance values, sediment content, turbidity (from mid-2010 to 2014), total organic carbon, total nitrogen, ammonium, nitrite-nitrate, total phosphorus, phosphate phosphorus, sulfate, chloride, fluoride, calcium, magnesium, sodium, potassium, iron, manganese, silicon, aluminum.

Water Chemistry Data from Extended Post-Fertilization Sampling

The analysis includes 5 parameters: total nitrogen, ammonium, nitrite-nitrate, phosphate phosphorus, total phosphorus.

After each fertilization event, additional water sampling is done in all catchment areas affected by fertilization and in two control areas. Water is sent for analysis every other day immediately after fertilization (4-5 times), and then twice during the following summer at high water flow (after significant rainfall).

In 2014, water analysis was expanded within the FutMon project

Water sampling from two reference catchment areas was done twice a month during 2014.

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

Flow Data

Manual measurements (control):

• Once per month from mid-2010 to mid-2015
• Twice per month from mid-2015.

Manual measurements are performed at our dams where the distance from the dam's edge to the water surface is measured on both sides. At each measurement, it is also noted whether the water flow is affected.

For automated level measurements, we use LevelTROLL 700 loggers that measure water levels for flow calculations and temperature every two minutes and store hourly averages. Data is retrieved twice a month (data cannot be viewed in real-time).

Multispectral Laser Scanning from 2009 and 2019

The Asa experimental forest and high-yield forest have been scanned with airborne laser in 2009 and 2019. In both cases, the scans were done with high point density, about 20 points/m², allowing for the identification of individual trees. During the scans, the areas were also photographed.

• Laser Scanning 2009: Laser data in various formats. Processed data in the form of classified laser data, digital elevation models, and calculated standing volume, mean height, and upper height. Aerial photos are rectified and available in two resolutions, 5 and 10 cm pixel size.
• Laser Scanning 2019: With two different wavelengths (green and infrared laser). Funded by the Mistra Digital Forest project.

Tree Data from Production Areas

Tree inventories within a network of 234 fixed plots in the Asa experimental and high-yield forest serve as reference data for the two laser scans performed in 2009 and 2019. The plots were established and georeferenced during the 2009 scan, when the area was divided into five strata based on tree species and age. Plot sizes vary depending on age and condition.

On the plots, the following is measured and recorded:

• Diameter at breast height (all trees)
• Tree species (all trees)
• Tree height (for a number of randomly selected sample trees representing diameter classes)
• Tree positions on the plot (all trees; during the second inventory in 2019)

Ground Vegetation Inventory

In 2018, ground vegetation was inventoried on all 234 production plots and on an additional 40 plots distributed over fertilized stands. All species occurring on a 1m² area in the center of production plots, along with their coverage percentage (%), were noted, distributed over three layers: ground layer (e.g., mosses), field layer (grasses, herbs), and shrub layer. Canopy cover above the surface was also noted in percentage.