Vigorous regrowth of deciduous stump sprouts after early pre-commercial thinning (PCT) causes a need of later pre-commercial thinning in order to ensure better growing conditions for more valuable coniferous trees. Uprooting improves efficiency of young stand management by preventing sprouting and minimizing the number of repeated operations.

Dilemma of repeated cutting in young stand management

Traditionally young stand management is done motor-manually by clearing saw in two phases: early PCT (also known as early cleaning) is to control the competition between wanted and unwanted trees and ordinary PCT is to control the overall stem density at the stand. Early PCT should be done about five years after regeneration when the height of saplings is ca. one meter. When pines are 5–7 m and spruces 3–4 m tall, it is time for other PCT. Then spruce stands are thinned to the density of 1,800–2,000 and pine stands to 2,000–2,200 saplings per hectare.

Cutting young hardwoods is quite ineffective method since it stimulates vigorous regrowth as most of the stumps produce several new sprouts. Thus cutting needs to be repeated and every repetition increases the total costs of young stand management. Prevention of sprouting and growth of unwanted tree species, i.e. minimizing a number of operations, the efficiency of young stand management can be improved.

Hydraulic jaws of Naarva uprooter grip and lift a bunch of deciduous trees from the ground and break their roots. Photo: Erkki Oksanen/Luke.

Cost-efficiency to young stand management by uprooting

The basic idea of uprooting is that the uprooted hardwoods do not offshoot new sprouts. The mechanical solution for this is the Naarva uprooter (Pentin paja Oy) which uproots the deciduous trees from a conifer sapling stand. Efficiency of this method is crucially dependent on how well the need of later PCT after uprooting is prevented.

Studies have proved that uprooting can serve as the only PCT-operation in a planted spruce stand. Timing is crucial; optimal uprooting time is when crop spruces have reached about breast height (= 1.3m) but the competing deciduous trees have not yet harmed crop trees. If stand is uprooted too early, the smallest trees will not be removed because they are not tall enough for the uprooting device. Also, attention must be paid to selection of sites to uproot. On moist sites there is a risk to get new birch seedlings from seed after uprooting. As only PCT-operation uprooting is cost-effective compared to total costs of two separate motor-manual PCT-operations (early PCT and PCT).

Biologically there are no restrictions for uprooting as long as timing and worksite selection are suitable. Thus, uprooting has great potential and it has got more common in Finland. New methods face prejudices among forest owners and forest professionals as well. By qualified research together with comprehensive information new methods are adaptable into practice. Latest results of uprooting can be found in EFFORTE Deliverable 2.3: Silvicultural feasibility of new early PCT methods – Prevention of hardwood sprouting with mechanical methods in early PCT.


Text: Tiina Laine & Timo Saksa, Natural Resources Institute Finland