Epsilon Archive for Student Projects

Abstract

SCA har idag cirka 280 000 hektar beskogad med contortatall (Pinus contorta Dougl. ex Loud. var. latifolia Engelm). Stora delar av den arealen har kommit in i, eller är på väg in i, gallringsbar ålder. Då få tidigare erfarenheter finns av att gallra contorta enligt skandinaviska förutsättningar krävs kunskapsinhämtning och utprövning av lämpliga tillvägagångssätt. Då contortabestånd nu gallrats i ett fåtal år på SCA: s marker kommer subjektiva uppfattningar om hur gallringen bäst bör gå till eller hur lätt eller svårt det är att gallra contortan. För att få en objektiv uppfattning om detta sker kontinuerligt uppföljningar och undersökningar internt inom SCA.

Syftet med denna studie var att svara på frågan huruvida gallringsskador hos contorta förekommer i någon annan utsträckning än hos tall (Pinus sylvestris L.), dels kvantitativt och dels om skadorna är annorlunda än hos den svenska tallen. Om så var fallet skulle möjliga samband med beståndsfaktorer sökas. Studien genomfördes i form av en fältstudie, där 16 genomförda gallringar i contorta och tall inventerades. På 5 provytor á 200 m2 per bestånd inhämtades beståndsdata före gallring (genom stubbklavning av uttagna träd) och efter gallring samt frekvens av skador på kvarstående träd, typ av skador, skadornas storlek samt trolig skadeorsak.

För contorta hittades inga samband mellan skadeandel, gallringsårstid och skadeorsak. Ett samband mellan skadeandel och gallringsårstid kunde påvisas för tall vilket stämmer överens med tidigare litteratur. Inga samband kunde påvisas för skadeandelen i contorta och beståndsegenskaper före gallring, exempelvis m3f/ha, stamantal/ha eller grundyta/ha.
Signifikanta samband återfanns för contorta mellan skadeplacering och ett flertal beståndsfaktorer, bland annat m3f/ha och grundyta/ha före gallring. Skadorna var också signifikant högre placerade i contortabestånden jämfört med tallbestånden.
I studien kunde inte heller någon skadeorsak påvisas som signifikant dominerande i contortabestånd.

Störst andel skador återfanns i vintergallrad contorta (19 %), därefter i vårgallrad contorta (15 %), i vårgallrad tall (10 %) och minst i vintergallrad tall (3 %). Flest antal skador bedömdes vara orsakade av kranarbete, därefter okänd orsak samt upparbetning och påfällning. Skadestorleken var störst i vårgallrad tall (genomsnitt 36 cm2), därefter vinter- och vårgallrad contorta med en skadestorlek på i genomsnitt 34 cm2 samt sist vintergallrad tall med en genomsnittlig skadestorlek på 17 cm2.

Intervjuade maskinförare menade att en tydlig anledning till hög skadeandel i vintergallrad contorta var dålig sikt. Den dåliga sikten vintertid beror till stor del på upplega i kronorna som binder mer snö än den svenska tallen med mindre kronor. Vid fällning av träder faller snön ur kronan och försämrar sikten tills snön lagt sig.

Slutsatsen dras att det ur skadesynpunkt kan vara lämpligt att sommargallra contorta.

Summary (eng)

In the 1970´s, when the large-scale introduction of lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm) in Sweden begun, most Swedish foresters considered lodgepole pine as a fast-growing species which should be managed with short rotation periods, large initial spacing and a minimum of silviculture measures such as thinning. The species was first brought to Sweden as an attempt to avoid a predicted shortage of wood fibre. Today, stands with high-quality lodgepole pine are intended for production of both pulp wood and timber and are managed with one or more thinnings during the rotation period.

SCA owns about 280 000 hectares of lodgepole pine, of which a large proportion is growing into age and height suitable for thinning. Since the knowledge of thinning lodgepole pine is fairly limited, SCA manages own research and follow-ups, parallel with the national forest research in Sweden managed by SLU.

The purpose of this study has been to look into whether thinning damage is more frequent in lodgepole pine stands than in native Scots pine (Pinus sylvestris L.) stands. An important question was if thinning damage was more frequent in lodgepole pine stands thinned during the sap flow period in spring compared to stands thinned during winter. Another aim was to investigate the type of damage occurring in lodgepole pine, concerning size, type of damage, location on the stem and most probable cause of damage.

Stand data was collected to analyze if any significant connections could be found between thinning damage and stand characteristics (such as age, height, stems/ha, m3f/ha and basal area before and after thinning). Other connections between thinning damage and how the thinning was performed (removed basal area/ha, removed m3f/ha and so on) were sought. The stand data originated from an inventory of 16 stands; 4 stands of lodgepole pine and 4 stands of Scots pine thinned during the sap flow period, 4 stands of lodgepole pine and 4 stands of Scots pine thinned during winter.

The study showed that damage to residual stems did occur more frequent in lodgepole pine stands than in Scots pine stands. No significant conclusions could be established about damage frequency and time of the year for thinning, even though more damage was registered in lodgepole pine stands thinned during winter and in Scots pine stands thinned during the sap flow period. Location of damage had a significant connection with some stand characteristics such as m3/ha and basal area/ha before thinning in lodgepole pine stands. The drivers stated that most of the damage was due to poor visibility. This was especially important in lodgepole pine stands thinned during winter, since the large crowns of lodgepole pine holds much snow which blinds the drivers for a moment when the trees are cut down.

The study showed that thinning lodgepole pine during summer could be appropriate to reduce mechanical thinning damage.

In the 1970´s, when the large-scale introduction of lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm) in Sweden begun, most Swedish foresters considered lodgepole pine as a fast-growing species which should be managed with short rotation periods, large initial spacing and a minimum of silviculture measures such as thinning. The species was first brought to Sweden as an attempt to avoid a predicted shortage of wood fibre. Today, stands with high-quality lodgepole pine are intended for production of both pulp wood and timber and are managed with one or more thinnings during the rotation period. SCA owns about 280 000 hectares of lodgepole pine, of which a large proportion is growing into age and height suitable for thinning. Since the knowledge of thinning lodgepole pine is fairly limited, SCA manages own research and follow-ups, parallel with the national forest research in Sweden managed by SLU. The purpose of this study has been to look into whether thinning damage is more frequent in lodgepole pine stands than in native Scots pine (Pinus sylvestris L.) stands. An important question was if thinning damage was more frequent in lodgepole pine stands thinned during the sap flow period in spring compared to stands thinned during winter. Another aim was to investigate the type of damage occurring in lodgepole pine, concerning size, type of damage, location on the stem and most probable cause of damage. Stand data was collected to analyze if any significant connections could be found between thinning damage and stand characteristics (such as age, height, stems/ha, m3f/ha and basal area before and after thinning). Other connections between thinning damage and how the thinning was performed (removed basal area/ha, removed m3f/ha and so on) were sought. The stand data originated from an inventory of 16 stands; 4 stands of lodgepole pine and 4 stands of Scots pine thinned during the sap flow period, 4 stands of lodgepole pine and 4 stands of Scots pine thinned during winter. The study showed that damage to residual stems did occur more frequent in lodgepole pine stands than in Scots pine stands. No significant conclusions could be established about damage frequency and time of the year for thinning, even though more damage was registered in lodgepole pine stands thinned during winter and in Scots pine stands thinned during the sap flow period. Location of damage had a significant connection with some stand characteristics such as m3/ha and basal area/ha before thinning in lodgepole pine stands. The drivers stated that most of the damage was due to poor visibility. This was especially important in lodgepole pine stands thinned during winter, since the large crowns of lodgepole pine holds much snow which blinds the drivers for a moment when the trees are cut down. The study showed that thinning lodgepole pine during summer could be appropriate to reduce mechanical thinning damage.