Selective cutting in a mountain Norway spruce forest

Transcription

1 Selective cutting in a mountain Norway spruce forest Kjell Andreassen 1), Birger Solberg 2) and Øyvind Jacobsen 2) 1) Norwegian Forest and Landscape Institute 2) Norwegian University of Life Sciences

2 Background Mountain forest is vulnerable, long regeneration period, small/seldom seed production and frequent frost problems Increased focus on biodiversity, alternatives to clearcuts, recreational reasons - e.g. maintain some/most of trees Forest owner wants to examine different silviculture methods with biological and economical consequences

3 Main Objectives Which alternatives are biological and economical feasible in a mountain Norway spruce forest in central Norway?

4 Outline Case study in Mountain Norway spruce forest Perform Experimental cutting Measure stand conditions before and after cutting Study Regeneration Growth effects after cutting Time studies of the cuttings Compare economy of different management systems

5 Materials and sites 2 Norway spruce stands were investigated: > Inventory: Twenty 400 m 2 sample plots > Sum 14 ha > Mean Volume=170 m 3 /ha, 550 stems /ha > Mean tree diameter 23 cm, mean height 18 m, > Productivity 3 m 3 /ha/yr > Seedlings 150/ha (height 0,5-3 m) > Timber quality estimated

6 Location Norway Lat. 63 N Alt. 650 m a.s.l. =100 m below alpine tree line Central Norway

7 Stand 119

8 Methods and 4 types of experimental cutting > Investigate forest structure and regeneration before cutting > Perform experimental cutting and establish an experimental forest > Timestudies to estimate the forest operation costs (harvesting and extraction) > Compare Net Present Value of the 4 management systems 1. Single tree Selection system (30-40 % of volume removed) 2. Group selection (Groups on ⅓ of the area) 3. Mountain Forest Selection System MFS (80 % removed) 4. Clear cutting

9 Mountain Forest Selection System

10 Mountain Forest Selection System

11 Selection System Group Selection Clear Cutting

12 Results Stems (N/ha) Diameter distribution After cutting =green Cuttings =red

13 Stems (N/ha) Diameter distribution After cutting =green Cuttings =red

14 Assumptions for economical calculations > The Norwegian growth simulater BESTPROG > 20 yr between each Group Selection and Selection System > 120 yr between each clear cutting, 80 yr between each MFS (80% cut) > Mortality: % per year > Costs of planting, thinnings, adm. etc: 1. Clear cutting (CC): 900 (Euro/ha) 2. Mountain Forest S (MFS): 750 (Euro/ha) 3. Group selection (GS): 250 (Euro/ha, ⅓ of the area) 4. Selection system (SS): 200 (Euro/ha) > Timber prices: 50/35 Euro/m3 for sawtimber/pulp

15 Valmet cm cutter and 14m crane

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20 Experimental cutting > Measured harvesting 230 m 3, 580 trees > Quality: > Sawtimber 38 % > Pulpwood 42 % > Vaste 20 % > Forest Operation costs (Harvesting and Extraction): > Clear cutting 16 Euro/m 3 > MFSelection System 20 Euro/m 3 > Group Selection 22 Euro/m 3 > Selection System 25 Euro/m 3

21 Economical comparison of 4 silviculture methods Value (%) Net present value Stand50 Stand119 0 Clear Cut MFSel Group S Selection S Silviculture method

22 NPV and Interest rate NPV Clear Cutting Mountain Forest Selection System Selection System Interest rate

23 Discussion and Summary Stand structure: One stand has an uneven-aged structure with some natural regeneration, second stand has fewer small trees/natural regeneration. Planting will short down regeneration time much Planting is seldom economical in such low productive mountain forest - however forest owner wants to plant Selection System and Group Selection have about 10-50% less NPV than Clear Cutting and Mountain Forest Selection System (i=2-4%) if selective cutting is performed in mature stands Normally it is not economically to maintain mature trees and this is the main reason why Selection and Group system have less NPV. However, most of the mountain forest in the area have the observed structure and the forest owner has to make a decision of the management today Economy depends much on discount rate Mountain Forest Selection System with heavy cuttings is a good biological and economical alternative. However, few retention trees are observed and the forest structure is usually not conserved