Epsilon Archive for Student Projects

Abstract

Over the past 40 years 600 000 ha of lodgepole pine (Pinus contorta ssp. latifolia (Engelm.) Critchf.) has been planted in Sweden (280 000 ha on SCA's forest land alone which represents about 15% of the company's total forest land area). In the early 70's SCA situated a number of experimental stands in order to investigate different aspects of the exotic tree, primarily growth rate. To be able to compare the two species plots with scots pine (Pinus sylvestris L.), this species was also planted at the same time and under the same conditions.
A number of questions should always be raised when exotic species are introduced in an ecosystem. Invasiveness, the pathogen situation and purely ethical issues should be discussed. One of the limiting factors of the lodgepole pine's invasiveness is its serotinous cones. Nevertheless has a certain self-spread still been shown to occur in the Swedish forest.
The serotinous cones of the lodgepole pine are an evolutionary adaption to forest fire. In these cones it accumulates a great number of seeds in order to be released after the next fire. In addition to these cones there are a few cones that are able to spread the seed without heat. This makes the culture populations of lodgepole pine and their close environment is subjected to continuous exposure of viable seeds.
The intention of this report is to investigate the potential of self-spread and establishment of P. contorta beyond the bounds of the cultural stands in northern Sweden. The establishment ability of the lodgepole pine is influenced by several habitat characteristics (such as vegetation, altitude, latitude, soil moisture). In the autumn of 2011 a field study was conducted with the intention of collecting suitable data in order to analyze these characteristics. The studies were carried out on 20 of SCA's trial facilities. These are located between 120-510 meters above sea level and in the range of 62° 12' N and 66° 11' N. Similar studies were carried out in 2000 and those results gave the opportunity to a comparison between 30 and 40-year old stands.
On both occasions string inventory was used throughout the data collection. The same strings were investigated in 2011 as in 2000. The number of lodgepole pine, Scots pine and Norway spruce seedlings were recorded. Height, edge zone type, vegetation, etc. were noted. Whether the plants become established on disturbed or undisturbed soil was also recorded. For lodgepole pine measured distance to the nearest parent tree.
The results show the great importance of disturbance for plant establishment. Only 14% of lodgepole pine seedlings that were found were on the ground that was not disturbed in any way. This compared with a Scots pine and Norway spruce: 38% and 54%. In 2000 the majority of plants were also found in disturbed areas, but with slightly less difference between the disturbed /undisturbed soil: 32% and 68%. The total number of lodgepole pine seedlings/ha was 98 st (62 of 2000). Divided into buffer zone and inside the stock, the result is: 165 pcs/ha of buffer zone (113 pcs/ha in 2000) and 32 pcs/ha within the population (11 pcs/ha in 2000).
The number of lodgepole pine seedlings were lower than both Swedish pine and Norway spruce, except inside the stock where the same number of lodgepole pine seedlings as a Swedish pine found: 32 pcs/ha (2000: 11 lodgepole pine/ha and 127 Scots pine/ha). The number of Norway spruce seedlings was much higher: 649 Norway spruce/ha in 2011 and 833 years in 2000). The tendency was the same in the edge zones.
It was also found a gradual decrease in the number of plants with distance from the nearest parent tree: at 20-25 m found only 3% of the self-scattered lodgepole pine seedlings. This was roughly the same result as 10 years earlier. The self-scattered lodgepole pine seedlings grew at an average distance from the nearest parent tree about 9.6 m (6.7 m in 2000) and the average height was 61 cm (62 cm in 2000). The average height of the stock was in the year 2011 134 cm and in the border zones 47 cm (Scots pine: 191 cm and 71 cm and Norway spruce: 73 cm and 78 cm).
The results show a lack of ability for plants to establish themselves in undisturbed soil. Only 14% of lodgepole pine seedlings that were found in the study grew on undisturbed ground. In comparison both Scots pine and Norway spruce showed a somewhat different result: 38% respectively 54% were found on undisturbed ground. In the study from 2000 there were registered a slightly smaller difference in the number of seedlings between the disturbed / undisturbed soil: 32% and 68%.
Furthermore, the quantity of plants was distinctively reduced with the distance from the nearest parent tree. Merely 3% of the self-spread lodgepole pine seedlings were found at a distance of 20-25 meters. The results were largely unchanged from the former study 10 years earlier. There was no association between latitude nor altitude and the ability for the seedlings to establish.

Under de senaste 40 åren har det planterats ca 600 000 ha contortatall (Pinus contorta ssp. latifolia (Engelm.) Critchf.). Enbart på SCA Skogs marker finns 280 000 ha vilket motsvarar ca 15 % av bolagets totala skogsmarksinnehav. SCA lade i början av 70-talet ut ett 20-tal försöksbestånd i syfte att göra uppföljningar av contortatallens utveckling. För att kunna jämföra arterna finns även parceller med svensktall (Pinus sylvestris L.) i dessa lokaler.
Införandet av en exot i ett ekosystem väcker frågor. Invasivitet, patogensituation och rent etiska frågor bör besvaras. Vad gäller contortatall är dess serotina kottar en begränsande faktor för dess virulens. Dock har det visat sig att en viss självspridning ändå förekommer i det svenska skogslandskapet. Vid sidan av de kådindränkta kottarna (där, i väntan på nästa skogsbrand, frön bevaras under flera årtionden) finns kottar som har möjlighet att sprida frön utan att utsättas för värme. Detta gör att kulturbestånden av contortatall och deras nära omgivning utsätts för en kontinuerlig exponering av grobara frön.
Denna rapport ämnar utreda contortatallens förutsättningar att etablera sig och sprida sig utanför de ursprungliga kulturerna i norra Sverige. Frågeställningen berör olika ståndortsegenskaper (exempelvis markvegetation, höjd över havet, latitud, markfuktighet) och deras inverkan på contortatallens etableringsförmåga. För att kunna besvara detta utfördes en fältstudie under hösten 2011 då datainsamlingen gjordes på 20 av SCA Skogs försökslokaler i Norrland vars lokalisering var inom spannen: 120-510 m.ö.h. och 62° 12' N-66° 11' N. Dessa lokaler besöktes år 2000 då en liknande undersökning utfördes. Nu gavs möjlighet till jämförelser av självföryngringssituationen i direkt anslutning till de då 30-åriga bestånden tio år senare.
Resultaten visar på den stora betydelsen av störning för plantornas etablering. Endast 14 % av contortaplantorna som hittades fanns på mark som ej störts på något sätt. Detta kan jämföras med svensktall och gran: 38 % respektive 54 %. Även år 2000 hittades majoriteten av plantorna på störda ytor, men med något mindre skillnad mellan störd/ostörd mark: 32 % respektive 68 %. Det totala antalet contortaplantor/ha var 98 st (62 st år 2000). Uppdelat på kantzon och inne i bestånd blir resultatet: 165 st/ha i kantzon (113 st/ha år 2000) respektive 32 st/ha inne i bestånd (11 st/ha år 2000).
Antalet contortaplantor var mindre än både svensktall och gran utom inne i bestånd där lika många contortaplantor som svensktall hittades; 32 st/ha (år 2000: 11 contorta/ha och 127 svensktall/ha). Antalet granplantor var mycket högre; 649 gran/ha år 2011 respektive 833 år 2000). I kantzonerna var tendensen densamma.
Vidare framkom en tydlig gradvis minskning av antalet funna plantor med avståndet från närmaste moderträd: vid 20-25 m hittades endast 3 % av de självspridda contortaplantorna. Detta var, i princip, samma resultat som 10 år tidigare. De självspridda contortaplantorna växte på ett medelavstånd från närmaste moderträd om 9,6 m (6,7 m år 2000) och medelhöjden var 61 cm (62 cm år 2000). Medelhöjden i bestånd var år 2011 134 cm och i kantzonerna 47 cm (svensktall: 191 cm respektive 71 cm och gran: 73 cm respektive 78 cm).
Vad gäller latitud och altitud hittades inga samband mellan dessa två variabler och förutsättningar till lyckad plantetablering.