From military tests to restoration success

It is home to a rich mountain flora

and populations of muskoxen,

wild reindeer,

and arctic foxes.

It was also the playground for "Hjerkinn PRO", the largest landscape restoration project performed in Norway thus far, aimed at restoring the former Hjerkinn firing range to a nature conservation area.

The firing range was surrounded by protected areas

and covered an area of 165 km ² 

that was used for military training exercises by Norwegian and allied military forces from 1923 to 2008.

In 1999, the Norwegian Parliament decided to close down the firing range and restore the area for future protection of ecosystem functioning and landscape quality, and for civilian use.

From 2009 to 2020, restoration activities were carried out by the Norwegian Defence Estates Agency (NDEA) in collaboration with the Norwegian Institute for Nature Research (NINA).

This included the removal of 75 km of roads,

more than 100 buildings,

and 19,000 pieces of undetonated ammunition.

A large number of sites were restored. In some of them, experimental projects were set up to study vegetation recovery after restoration.

This is the story of one of these sites: the restoration of a 400 x 600 m ammunition testing area that had been used to test cluster bombs and other types of ammunition.

The ammunition testing area had been severely disturbed and contrasted strongly with the intact surrounding vegetation.

(photo taken in 2011)

1) Removal of undetonated ammunition

Restoration started with the removal of undetonated ammunition by soldiers with the assistance of trained dogs.

2) Addition of olivine

After clearance, the field was treated with the mineral olivine to prevent leakage of heavy metals from the gravel, which was stirred for terrain formation.

3) Creation of small-scale relief

Later, the terrain was provided with small-scale relief to mimic natural landscape elements.

4) Assisted revegetation

Assisted revegetation was performed to promote initial recovery of the ecosystem. Cuttings of three native willow species (grayleaf, tea-leaved and downy willow; Salix glauca, S. phylicifolia and S. lapponum, respectively) were collected from Hjerkinn in autumn 2013 ...

... and propagated in a greenhouse over the winter.

In spring 2014, a total of 25,000 propagated willows was planted, covering ca. 4% of the field.

But how many plants are needed per area to effectively speed up the revegetation process?

To study this, the willows were planted in three densities:

• High (4 plants/m ² )
• Medium (2.5 plants/m ² )
• Low (1 plant/m ² )

Additionally, 25% of the field was fertilized and seeded with the native grass species sheep fescue (Festuca ovina), propagated from local seeds.

The presence of permanent plots allows for regular monitoring of the vegetation and an evaluation of the effectiveness of the restoration measures.

HFK-sletta had become noticeably greener ...

... and harbored at least 38 different vascular plant species.

98% of the monitored willows had survived ...

... and 93.5% of them had increased in size.

Planting density mattered;

plots with higher willow densities (≥ 2.5 plants/m ² ) had a higher species richness of vascular plants ...

... and a higher number of newly established willow seedlings.

Seeding of sheep fescue on the other hand increased vegetation cover,

as was clearly visible in the field.

These findings suggest that combining planting and seeding of native species is a promising approach to promote vegetation recovery ...

... and speed up the restoration of severely disturbed sites.