METLA Project 3180

Field afforestation in EU-Finland

Duration: 1996-2000 Keywords: economy, socioeconomics of field afforestation, soil aeration, soil fertility, soil waterconditions, technical quality, vegetation management, vole and moose damage

Objectives

Large-scale afforestation of agricultural land in Finland, aimed at reducing the cultivation area in the country, began in the late 1960s. The area afforested to date exceeds 200, 000 hectares. Although many of Finland's extremely well growing tree stands are located on former agricultural land, the general opinion that afforestation of old fields has been unsuccessful. Afforestation of peatland fields is felt to be particularly problematic.

In this project following main questions are studied. a) Afforestation methods of agricultural fields (choise of tree species, soil treatment, natural regeneration, sowing, development of tree roots) b) Physical and chemical properties of of soil and their significance for growing trees is evaluated. Need for fertilization is studied. c) Effect of competition of vegetation on the success of seedlings d) Vole and moose damages e) Technical quality of trees g) Profitability of afforestation h) Socioeconomical questions of afforestation.

Results

Success of practical afforestations:

The success of practical afforestations made in the 70's and 80's have been reported from three areas (Northern Carelia, Northern Savo and Central Ostrobothnia). In all these studies it was found that the success of Scots pine, Norway spruce and silver birch on afforested peat fields in much poorer than on mineral soil fields. Especially silver birch grown on peat fields have grown poorly. On peat fields the number of living seedlings is smaller,. They are shorter and the vitality of seedlings is poorer than on mineral soil fields. Natural downy birches eventhoug situation in clusters along ditches, fill in the plantation considerably. Ground vegetation, fungal deceases, moose, sprouts and nutrient deficienses are main pests and deceases.

Afforestation methods: The significance of downy birch, especially on peat fields was studied. Natural regeneration, sowing and planting were compared. Also pests and deceases typical to birch have been identified. Also similar survey on silver birch was made.

The possibilities of aspen in fields afforestation was estimated by means of literature survey.

Soil characteristics, especially on peat fields:

The cultivation of agricultural crops, use of machinery, fertilization and liming all have changed the physical and chemical properties of the soils and especially that of peat during the decades of cultivation. A common practice has been to mix mineral soil as a soil ameliorating agent into the soil of peat fields. Mineral soil addition has long term effects on the amounts of certain nutrients and on the physical properties of the peat In cases where mineral soil had been added to the peat fields, the amounts of P, K, Ca, Mg, Mn and Zn were higher in the 0-20 cm soil layer whereas the amounts of N and B did not significantly differ from those in the soils of peatland forests.

The nutritional status of the soil is essential information required when afforesting peat fields. The results emphasise the importance of examining the use of adding mineral soil to peat fields and they show that adjacent peatland forests posses a low indicative value in the assessment of the nutrient status of peat fields. The changes in the physical and chemical properties of peat due to cultivation seem to be significant and long lasting to such a degree that the original nutritional state of the former peat fields is very unlikely to be regained even with a long period of time.

Fertilization and soil amelioration:

Boron and potassium deficiencies can be attended by remedial fertilisation. One solution to growth disturbances in young stands established on peatland fields has been wood-ash fertilisation. Basic improvement of the nutritional status is essential on certain afforestation sites. Intercorrelations between growth disturbance and nitrogen metabolism (amino acids, proteins) of Scots pine have been the subject of research. Scots pine particularly is adapted to nitrogen poor sites and on nitrogen rich sites it may have metabolic problems. These take the form of dense, bushlike growth habit, heavy branching, leader losses and possible reduced frost hardiness.

Vegetation control: The most important element in the success of afforestation is that ground vegetation needs to be controlled to safeguard the seedlings' initial development. The effect of vegetation cover on the mean height, mortality, percentage of seedlings damaged by vole and foliar nitrogen content of birch seedlings was studied in an field afforestation experiment at Vilppula, Central Finland. Results show that high vegetation cover is detrimental to seedlings in many ways. The possibility of using different kings of mulches has also been studied.

Vole and moose damage: The risk of vole (Microtus agrestis) damage on fields is 25 times greater than on any other regeneration site. The voles damages and their significance and dependence of different measures were studied in the project.

Effect on biodiversity: A literature survey on the soil properties and vegetation succession of old afforested fields was made.

Project leader: Hytönen, Jyrki
The Finnish Forest Research Institute, Kannus Research Station, PL 44, 69101 Kannus
Phone: +358 10 211 3405 Telefax: +358 10 211 3401
E-mail: Jyrki.Hytonen@metla.fi

Other researchers: Aarnio, Jukka, HE (1996), Heikkilä, Risto, VA (1996-2000), Heiskanen, Juha, SU (1996-1998,2000), Henttonen, Heikki, VA (1996), Lilja, Sakari (1997-99), Nurmi, Juha, KA (1998-2000), Pietiläinen, Pekka, MU (2000), Saksa, Timo, SU (1997-2000), Siipilehto, Jouni, VA (1997-99), Wall, Antti, KA (1996-2000)

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Updated 31.12.2003
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