The results of the introduction of twisted pine (Pinus contorta) in Bolshoy Solovetsky Island

The introduction of new species into the flora of a particular area always pursues certain goals: obtaining new types of products, decorative qualities, increasing forest productivity and so on. It is obvious that the North American species of twisted pine (Pinus contorta var. latifolia) was used primarily to increase the productivity of existing forests. The positive experience of such introduction of a new breed is known in western European and Scandinavian countries (Backlund and Bergsten 2012; Elfving et al. 2001) and in our country (Fedorkov and Gutiy 2017; Zhigunov and Butenko 2019; Gutiy and Fedorkov 2016; Demidova et al. 2016; Rayevsky and Pekkoev 2013; Fedorkov and Turkin 2010).

Bolshoy Solovetsky Island is the largest in the White Sea and is widely known for its history, cultural monuments and natural attractions. Within the borders of the Solovetsky archipelago, there is currently the Solovetsky State Historical, Architectural and Natural Museum Reserve. This territory has a high attendance by pilgrims and tourists, and here the twisted pine could take its place both as a species that increases the productivity of the forests of the archipelago and as a decorative species – an additional object of attraction for tourists and nature lovers. In its natural range, the twisted pine spreads naturally on burning. Due to the high temperature, the closed cones open and the seeds, falling on mineralized soil, successfully germinate (Eisenreich 1959). On Bolshoy Solovetsky Island, twisted pine cultures were created by planting on a plot with favourable and suitable growing conditions.

The purpose of the study is to establish the morphological parameters of the twisted pine, its growth in the conditions of the Bolshoy Solovetsky Island in comparison with the native species – the Scots pine, and also to consider the possibility and necessity of further introduction of the species.

In the central part of the Bolshoi Solovetsky Island in 1988, crops of twisted pine (P. contorta) and many Scots pine trees (Pinus sylvestris L.) were created. Planting with seedlings (seeds – Yukon, Rusty Creek, 63°28’ north latitude and 136°25’ west longitude) was carried out under Kolesov's sword without soil preparation. Landing site passed by fire 8 years before landing. The distance between the rows was 2.5 m and the planting steps was 2.5 m. The area is hilly. The type of forest is bilberry pine forest. At present, the growing conditions favour the growth of bilberry and lingonberry in the ground cover. Dominant ground cover species (Vaccinium myrtillus L. and Vaccinium vitis-idaea L.) are present in approximately equal amounts. In addition, lichens from the genus Kladonia are also typical for the place. The soil under the crops is thin, sandy, fresh podzol.

The studies were carried out in the thicket phase with the approach to the perch (Merzlenko and Babich, 2021). The preservation of the cultures of twisted pine (P. contorta var. latifolia) and Scots pine (P. sylvestris L.) was determined. Trees were selected (62 and 31 trees, respectively), the diameters and heights of which were measured, the number of branches of the first order (extending from the trunk) was calculated and the maximum lifespan of the needles of the terminal shoots and lateral shoots was determined. Wood samples (cores) were taken from them with an age drill to measure radial growth. To measure the height gain, six medium model trees were felled.

In the laboratory conditions, the width of the annual rings was measured using the MBS-9 microscope with an accuracy of ±0.05 mm, as well as the width of the late wood.

The taxation indicators of the two types differed slightly. The average diameter at chest height and trunk volume of the twisted pine were slightly higher compared to the Scots pine, but the differences in these parameters between the species are unreliable. The average height of twisted pine trees was significantly higher (by 85 cm; Tab. 1). The indicators of the assimilation apparatus of twisted pine surpassed those for Scots pine in the number of branches and in the life span of needles. The number of branches in the whorl prevailed in twisted pine. Up to the age of 6–8 years, the number of branches on the trees of twisted pine was less or the same as that of Scots pine (P. sylvestris L.), and in older age, the number was always greater in P. contorta var. latifolia. The average number of branches was in the range of two to four in the whorl of Scots pine and two to eight pieces in twisted pine.

It is interesting to compare the bark of two types of pines. The average value of the bark thickness at the age of 18 was 1.35 ± 0.038 mm in twisted pine and 1.86 ± 0.095 in Scots pine, that is, in native pine, the bark was 38% thicker.

Attention is drawn to a significant number of pathologies in P. contorta and especially two vertexes in trees (13% of trees) (Fig. 1). There are other damages in equal quantities: cancer, dry top, trunk curvature. In general, 22% of the trees of the species are susceptible to pathologies. The reasons probably lie in the weak mechanical properties of the trunk on the one hand and the powerful snow cover in the region on the other hand.

Figure 1

An assessment of the average size of the annual ring width in trees of different ages showed that in general, the radial growth of twisted pine and Scots pine was close in magnitude (Fig. 2). We can talk about significant differences in growth at the age of 9 and 15 years, and the strongest differences between the species are characteristic of 18 and 19 years of life. At this age (in these years), the growth of Scots pine was greater than that of twisted pine by 38% and 136%, respectively. Twisted pine demonstrated a distinct trend of increasing the width of the annual ring with age up to 13–14 years and then it declined. For the Scots pine also, increase in growth was observed at 14–15 years, following which the values of the width of the annual rings decreased slightly, remaining at a consistently high level. The average values of the annual ring width for the considered time interval were 3.02 mm for twisted pine and 3.30 mm for Scots pine.

Figure 2

It is interesting to trace the change in the width of the late zone of the annual ring in the twisted pine (P. contorta var. latifolia) in comparison with the Scots pine (P. sylvestris L.) On average, over the studied time interval, the width of the late zone in the Scots pine was 12% of the width of the annual ring and was 14% in the twisted pine. The change in the average values of the width of the late zone shows that the twisted pine is characterized by a pronounced trend of increasing this indicator with age, and in the Scots pine, on the contrary, it is weakly expressed and the size of the late wood is stable over time (Fig. 3). At a young age, the width of the late zone of wood in twisted pine is more than twice that of Scots pine. This explains the fact that at a young age, relatively many trees of the P. contorta var. latifolia species lie down, which was previously noted in the literature (Feklistov et al. 2008). The data on the number of two-vertex pines and the curvature of the trunk of P. contorta var. latifolia are presented above. The manifestation of such changes is most likely due to the low mechanical properties of the trunks due to the small size of the late wood. At the age of 9–12 years, there is an increase in the accumulation of the late zone in the twisted pine relative to the Scots pine, and in the future, this increase persists. All the data presented are reliable for a significance level of 0.05.

Figure 3

The presence of well-defined whorls in model trees allowed us to obtain data on linear growth in height from the beginning of pine planting. In the first years after planting, the increase in height was small, differed little in species and was within 2–20 cm. Both breeds showed a very clear trend of height gain with age. In recent years, the increase in height of twisted pine (P. contorta var. latifolia) has become noticeably higher than the increase in height of Scots pine (P. sylvestris L.); in the last 2 years, the increase has been 50–60 cm in twisted pine and 40–50 cm in Scots pine. On average, over the entire period of growth, the height increase in twisted pine was less than that of Scots pine – 25.84 ± 0.92 and 28.05 ± 0.76 cm, respectively.

The dependence of the trunk volume on the diameter of the twisted pine (P. contorta var. latifolia) was actually the same as that of the Scots pine (P. sylvestris L.) (Fig. 4). The relationship was very clear and close. The presented approximation equations can be used to determine the volume of the trunk, both for one and for another breed. These dependencies once again confirm the previously considered conclusion about the unreliability of the difference in the average volume of the trunk of both species.

Figure 4

We can sum up some results. If in the conditions of western Europe, twisted pine significantly exceeds Scots pine in productivity (Tigerstedt 1922; Metzger 1928), in the conditions of Sweden, productivity is almost 2 times higher (Swedish experiment 1972; Lindbeck 1977). Then, in the conditions of a more severe climate or, more precisely, the microclimate of the Bolshoy Solovetsky Island, this is not so obvious. In almost all growth indicators, both species had very similar characteristics. With the same initial density of crops (1600 pcs/ha), in the future, their safety differed: the planting of twisted pine was characterized by a fairly high safety (68%), which is slightly lower than the safety observed in Scots pine crops (76%). At the time of the study, the density was 1088 and 1216 units/ha for twisted pine and Scots pine, respectively. Taking into account the lower density of twisted pine and approximately equal volumes of trunks for medium diameters, wood reserves will be 10%–12% higher in Scots pine than in twisted pine. In addition, as shown above, 22% of P. contorta var. latifolia trees have pathologies. Therefore, it is hardly possible to increase the productivity of Solovetsky forests by introducing twisted pine.