Swedish Scots Pine Research Articles

Application of Transfer Effect Models for Predicting Growth and Survival of Genetically Selected Scots Pine Seed Sources in Sweden

We used a regression model approach to examine transferability of the 1.5-generation Swedish Scots pine orchard plus trees using the estimated coefficients of the transfer models recently developed for growth and survival of unimproved Scots pine in Sweden and Finland. Differences between observed and predicted values obtained for height and survival of 3214 plus tree progenies, tested at 58 progeny trials, were regressed on latitudinal transfers (∆LAT). In order to evaluate rates of improvement in height and survival of selected progenies over unimproved trees, average percentage differences in performances (∆g%) between the tree groups were calculated. Results indicate that the adopted models can further predict performances of more advanced-generation orchard trees, as there was no evidence of any systematic pattern in the slope of regression functions. Overall, ∆g% estimates obtained for height of progenies were greater than those of survival, suggesting Swedish Scots pine breeding activities are generating gain in the height growth. Moreover, ∆g% estimates obtained for height and survival of half-sib progenies were higher than those of full-sib ones, as a result of response to higher selection intensity applied in the reselection of their parents. This indicates that, in addition to the gain in growth, a gain in survival is also achievable from 1.5-generation seed orchards, depending on the intensity of selection and intended deployment site.

Early performance of Pinus sylvestris and Picea abies – a comparison between seedling size, species, and geographic location of the planting site

Small seedlings may be cheaper and establish faster than larger seedlings, but be more sensitive to stress and therefore less competitive. Site factors and species may also influence seedling performance, but the early performance of the most common species in Swedish plantations, Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) H. Karst), has rarely been compared at identical sites. To identify optimal species and size combinations, seedlings were grown in containers of two sizes, 50 and 90 cm3, and planted during two consecutive years at both coastal and inland sites in northern Sweden. The larger Scots pine seedlings grew more rapidly than the smaller and were also the tallest of all seedlings five years after planting. No seedling size-related difference in Norway spruce growth was found. Highest mortality occurred the first three years after planting and pine weevils were one of the major causes. Larger seedlings of both species had a slightly lower mortality compared to smaller. Five years after planting, the proportion of damaged seedlings plateaued for Norway spruce, but not for Scots pine. Consequently, despite a higher growth the Scots pine seedlings remained sensitive to damage during a longer period than Norway spruce. No interactions were found between geographic location and seedling size or species on growth, mortality, or damage.

Comparative Economic Value Estimation of Matsutake Mushroom and Timber Production in Swedish Scots Pine Forest

Comparative Economic Value Estimation of Matsutake Mushroom and Timber Production in Swedish Scots Pine Forest

Effects of nitrogen fertilization on the forest floor carbon balance over the growing season in a boreal pine forest

Abstract. Boreal forests play a key role in the global carbon cycle and are facing rapid shifts in nitrogen availability with poorly understood consequences for ecosystem function and global climate change. We quantified the effects of increasing nitrogen availability on carbon fluxes from a relatively understudied component of these forests – the forest floor – at three intervals over the summer growing period in a northern Swedish Scots pine stand. Nitrogen addition altered both the uptake and release of carbon dioxide from the forest floor, but the magnitude and direction of this effect depended on the time during the growing season and the amount of nitrogen added. Specifically, nitrogen addition stimulated net forest floor carbon uptake only in the late growing season. We find evidence for species-specific control of forest floor carbon sink strength, as photosynthesis per unit ground area was positively correlated only with the abundance of the vascular plant Vaccinium myrtillus and no others. Comparison of understorey vegetation photosynthesis and respiration from the study site indicates that understorey vegetation photosynthate was mainly supplying respiratory demands for much of the year. Only in the late season with nitrogen addition did understorey vegetation appear to experience a large surplus of carbon in excess of respiratory requirements. Further work, simultaneously comparing all major biomass and respiratory carbon fluxes in forest floor and tree vegetation, is required to resolve the likely impacts of environmental changes on whole-ecosystem carbon sequestration in boreal forests.

Some edge correction methods for marked spatio-temporal point process models

Three edge correction methods for (marked) spatio-temporal point processes are proposed. They are all based on the idea of placing an approximated expected behaviour of the process at hand (simulated realisations) outside the study region which interacts with the data during the estimation. These methods are applied to the so-called growth-interaction model. The specific choices of growth function and interaction function made are purely motivated by the forestry applications considered. The parameters of the growth and interaction functions, i.e. the parameters related to the development of the marks, are estimated using the least-squares approach together with the proposed edge corrections. Finally, the edge corrected estimation methods are applied to a data set of Swedish Scots pine.

Genetic analysis of longitudinal height data using random regression

Genetic analysis of forest longitudinal height data using random regression (RR) has the potential to be attractive to tree breeders because of its advantages for selection at early ages. Our study provides an example of implementation of RR to forest tree height growth data. The data set comes from the Swedish Scots pine ( Pinus sylvestris L.) breeding program with a pedigree over three generations and consists of 899 trees with reconstructed phenotypic height records for 16 years. Legendre polynomials and B-splines were used as base functions in RR models. The restricted maximum likelihood method was employed to estimate (co)variance parameters. Results show that heritability increased with age, except for early ages (years 1 to 4). In general, slightly higher heritabilities were found for the RR model than for the single-trait and paired-trait analyses for most ages. Moreover, the heritabilities obtained with B-splines as the base function tended to be somewhat higher than those obtained with Legendre polynomials. The RR method provides a promising approach for estimating genetic parameters of longitudinal data that can be used in early selection. However, application to real data from other species and to simulated data is needed before general breeding recommendations can be established.

Joint analysis of spatial genetic structure and inbreeding in a managed population of Scots pine

We have investigated the fine-scale spatial genetic structure in a managed Scots pine forest. For this purpose, we perform a Bayesian genetic-cluster analysis of 96 geographically mapped individual seed trees of Swedish Scots pine based on 14 microsatellite loci. The analysis was carried out with the recently developed program GENECLUST (François et al., 2006), which provides the facility to jointly incorporate both spatial information from a geographical neighborhood structure through a Potts-Dirichlet model and account for variable degrees of inbreeding within the clusters. To evaluate whether inbreeding and spatial interaction should be included in the best-fitting statistical model for our data, we used the deviance information criterion (DIC), a weighted measure of model fit that accounts for an effective number of free parameters in a model. Analysis shows that a model with a single estimated cluster, with high levels of inbreeding (0.25) and with a moderate amount of spatial dependency within the unique cluster (Psi=0.2-0.4), best explains the data. We also carried out Bayesian parentage analysis, which enabled us to exclude the possibility that the sample constitutes one single full-sib family.

Root respiration data and minirhizotron observations conflict with root turnover estimates from sequential soil coring

The turnover of fine roots in northern coniferous forests has conventionally been assumed to be rapid, in line with results from sequential coring in the late 1970s in a Swedish Scots pine stand (SWECON project) where a rate of 7.4 year−1 was estimated. New quantifications of the root respiration in other stands motivated a recalculation of the SWECON data; an indirect estimation of the turnover rate was much slower, about 2.1 year−1. As a consequence, fine-root production is considered to be much lower than in previous estimates. Furthermore, direct observations of Norway spruce fine roots (<1 mm) from minirhizotrons in Sweden, including a site close to the SWECON site, indicated a slower estimate, with fine-root turnover rate of 0.9 year−1.

Gains from selecting Pinus sylvestris in southern Sweden for volume per hectare

An overall objective of the Swedish Scots pine (Pinus sylvestris L.) tree breeding programme is to increase volume production. Selection is based on height at young age as an indicator of future volume production. This study examined the relationship between height at young age and volume production in block-plots at older ages, and the sustainability of increased growth in volume per unit area using parent breeding values. The study included five trials with controlled pollinated progenies from 71 phenotypically selected plus-trees. Height and diameter were measured in the trials at ages ranging from 7 to 36 years. The genetic correlation between height at 9 years and volume growth per unit area at 30 years of age was 0.8. The additive genetic coefficient of variation for growth per area unit was 17% at the age of 30 years, i.e. first thinning. Based on the estimated parameters, selection of the best 25% genetic entries according to their height at age 9 years resulted in 13% volume gain at age of 30 years, while selection of the 10% best resulted in 18% volume gain. The plus-tree progenies had 12% higher volume growth per unit area than the unimproved commercial check lots, and this difference needs to be added to obtain the total gains. This means that selection of the 25% best parents gave a gain of 25% in volume per hectare compared with unimproved check lots.

Advanced generation seed orchards’ turnover as affected by breeding advance, time to sexual maturity and costs, with special reference to Pinus sylvestris in Sweden

The effect of various biological, genetic, economic and management factors relevant to advanced generation seed orchard establishment was investigated using numerical estimates for Scots pine (Pinus sylvestris L.) in Sweden. Factors considered were planting density, rate of genetic advance in the breeding population, timing of first seed collection, seed value, seed production cost (stratified to establishment, annual management, cone harvest and seed extraction), orchard rotation age and contamination level. The developed model demonstrated its utility in studying and evaluating various economic and biological options associated with advanced generation seed orchard establishment/turnover. Sensitivity analyses demonstrated the robustness of the developed model through various arbitrarily changes in genetic gain advances, establishment, management and seed production, particularly those associated with cone harvests from upper crown and costs. The Swedish Scots pine case study produced results supporting faster turnover of seed orchard generations (30 vs 40 years) with shorter orchard lifespan (early start of seed cone after 8 years vs 15 years) delivering higher gain through minimizing the genetic gain differential between the breeding and production populations and allowing the capture of this gain for inclusion in the seed orchards. Orchard planting densities of 400 and 600 grafts per hectare produced similar results with marginal differences, and the latter was recommended for future orchard establishment.

Effects on ground vegetation of the application of wood ash to a Swedish Scots pine stand

The impact of different doses and types of wood ash on ground flora was studied over a 5-year period following ash application to a medium-aged Scots pine stand in the central part of Sweden. Generally, there were only minor changes in the vegetation cover as a result of the treatments, and the species composition was unaltered after five years. When treated with hardened and crushed wood ash, the three most common bryophytes reacted rapidly, displaying severe visible damage in the initial phase of the study period. Two years after ash application, the bryophytes had started to recover, and after five years no visible damage could be discerned. At the highest ash dose (9 tons ha−1), however, the cover of bryophytes was significantly reduced, even after five years. No visible damage to the bryophytes was found after treatment with pelleted ash or after N treatment, and no visible damage to lichens was found for any treatment. However, by the end of the study period, the addition of wood ash, including the pelleted ash, had significantly reduced the cover of Cladina lichens. All wood ash treatments tended to lead to a decrease in the cover of dwarf shrubs. Nitrogen addition tended to increase the cover of Vaccinium myrtillus and decrease the cover of Vaccinium vitis-idaea and Calluna vulgaris. The results from this study highlight the need for legal restrictions on the chemical and physical properties of wood ash recycled within forest systems, in order to avoid a negative impact on ground flora. Die Folgen der Ausbringung von Holzasche auf die Bodenvegetation in einem schwedischen Waldkiefernbestand. Die Auswirkungen unterschiedlicher Dosierungen und Typen von Holzasche auf die Bodenflora wurde über eine 5-Jahres-Periode untersucht, im Anschluss an die Aschen-Ausbringung auf einen mittelalten Waldkiefernbestand in Zentral-Schweden. Generell resultierten nur geringe Veränderungen in der Vegetation als Folge der Behandlungen, und die Artenzusammensetzung hatte sich nach fünf Jahren nicht geändert. Nach einer Behandlung mit harter und zerstossener Holzasche reagierten die drei häufigsten Moosarten sehr schnell und zeigten einen gut sichtbaren Schaden in der Anfangsphase der Untersuchungsperiode. Zwei Jahre nach der Aschen-Ausbringung hatten die Moose begonnen, sich zu erholen, und nach fünf Jahren konnte kein sichtbarer Schaden mehr entdeckt werden. Bei der höchsten Aschendosis (9 Tonnen pro ha) war jedoch die Moos-Deckung deutlich reduziert, auch nach fünf Jahren noch. Nach der Behandlung mit Pellet-Asche oder nach N-Behandlung konnte kein sichtbarer Moos-Schaden festgestellt werden, und auch für die Flechten gab es bei keiner Behandlung einen sichtbaren Schaden. Am Ende der Untersuchungsperiode hatte die Zugabe von Holzasche, inklusive der Pellet-Asche, jedoch eine signifikante Reduktion in der Deckung von Cladina Flechten zur Folge. Alle Holzasche-Behandlungen tendierten dazu, die Deckung an Zwergbüschen zu verringern, die Stickstoff-Zufuhr tendierte die Deckung von Vaccinium myrtillus zu erhöhen und die Deckung von Vaccinium vitis-idaea und Calluna vulgaris zu verringern. Die Ergebnisse dieser Studie zeigen die Notwendigkeit für gesetzliche Vorgaben zu den chemischen und physikalischen Eigenschaften der im Forst recycelten Holzasche, um negative Einflüsse auf die Bodenflora zu verhindern.

Annual and long-term fluctuations of the nematode fauna in a Swedish Scots pine forest soil

Summary Samples from an old Scots pine forest at Ivantjarnsheden in the middle of Sweden were used to study predictability and patterns of variation of soil nematode communities. There were two annual sampling series (1974–75 and 1977–78) and one long-term series sampled in September ten times over a period of 25 years. The abundance and the composition of the fauna fluctuated rather considerably in both the annual and long-term series. In the annual series abundance and species composition varied in a way which can partly be explained by changes in temperature and moisture. Total nematode abundance was influenced by soil water contents as indicated by co-variations with precipitation. Although the variations in abundance and fauna composition were large no systematic changes could be detected during 25 years. The differences in faunal structure between the two annual series were greater than between the annual and the long-term series. In all series there was a distinct vertical stratification of the fauna. In the superficial moss and litter layers species belonging to Adenophorea ( Plectus ) dominated. In deeper layers members of Rhabditida ( Acrobeloides ) contributed a greater proportion of the fauna. Variations of the annual series indicate that coexistence of different nematode species is facilitated by differences in response to temperature and moisture. The abundance of fungal and bacterial feeders changed in a regular way. During the summer the proportions of fungal and bacterial feeders were almost equal, but during the wet and cold winter the proportion of bacterial feeders increased. Rapidly growing bacterial feeding species belonging to Rhabditida were common in late summer and early autumn, whereas the more slowly growing bacterial feeders belonging to Adenophorea were most abundant during the winter. Although the community fluctuated rather much the average values indicated a rather high degree of predictability and also a high similarity with nematode faunas of other pine forest soils.

High heritability of wood extractives in Pinus sylvestris progeny tests

Pinosylvin, resin acid, fatty acid, and sterol contents were analyzed in north Swedish Scots pine (Pinus sylvestris L.) heartwood from 160 and 44 trees in two full-sib progeny tests, aged 25 and 44 years, respectively. Large variations were found between individual trees, with coefficients of variation of ca. 0.7, 0.8, 0.3, and 0.5 for the four groups of extractives, respectively. Heritabilities were estimated to be 0.5-0.7, ca. 0.6, 0.3-0.8, and 0.6-0.9, respectively, and corresponding genetic coefficients of variation were 0.4-0.8, ca. 0.6, ca. 0.2, and 0.2-0.5, respectively. The results indicate that there is strong genetic control of the wide individual variation, which consequently provides excellent opportunities for genetic improvement. Although similarities in genetic parameters were observed at the two test sites, some differences in total levels of the extractive groups and in their isomeric ratios were detected. This suggests that the genetic control of these features, although strong, may be modulated by environmental factors or other influences, such as the phase of tree development.

High heritability of wood extractives in &lt;i&gt;Pinus sylvestris&lt;/i&gt; progeny tests

Pinosylvin, resin acid, fatty acid, and sterol contents were analyzed in north Swedish Scots pine (Pinus sylvestris L.) heartwood from 160 and 44 trees in two full-sib progeny tests, aged 25 and 44 years, respectively. Large variations were found between individual trees, with coefficients of variation of ca. 0.7, 0.8, 0.3, and 0.5 for the four groups of extractives, respectively. Heritabilities were estimated to be 0.5-0.7, ca. 0.6, 0.3-0.8, and 0.6-0.9, respectively, and corresponding genetic coefficients of variation were 0.4-0.8, ca. 0.6, ca. 0.2, and 0.2-0.5, respectively. The results indicate that there is strong genetic control of the wide individual variation, which consequently provides excellent opportunities for genetic improvement. Although similarities in genetic parameters were observed at the two test sites, some differences in total levels of the extractive groups and in their isomeric ratios were detected. This suggests that the genetic control of these features, although strong, may be modulated by environmental factors or other influences, such as the phase of tree development.

Silviculture and management of Scots pine in Sweden

This paper gives some information about silvicultural trends in Sweden with the main focus on management of Scots pine stands and measures proposed to enhance biodiversity. During the last decades there has been a shift away from volume production orientated forestry towards forestry focusing on both production and environment with a special emphasis on biodiversity. Our current Forestry Act has two equal goals, (i) forest production and (ii) environment with sustained biodiversity. The major Swedish forest companies and other forest owners are signing agreements in order to meet certification requirements and show that their forest management considers the sustainability of the whole forest ecosystem and the environment of surrounding ecosystems. Even though Scots pine will still mainly be managed on a clear-cutting system, these developments will change Swedish Scots pine forests from even aged, uniform monocultures towards more mixed species and multi-storied stands. Prescribed burning will be practised on Scots pine sites as a site preparation measure that also enhances biodiversity. In this way silviculture will mimic the major natural disturbance agent in boreal Sweden – forest fire. Measures to enhance biodiversity are based on the best available knowledge, but the effect of these measures on biodiversity and forest production is largely unknown. Another uncertainty is how these new stands should be managed in an efficient way.

High heritability for heartwood in north Swedish Scots pine

In 44-year-old full-sibs of north Swedish Scots pine (Pinus sylvestris L.), the estimated heritability of heartwood diameter was 0.5 despite the influence of environmental changes (caused by an earlier thinning) which apparently had reduced the heritabilities of height and diameter to around zero. The heritability of bole straightness was estimated to be 0.6. The coefficient of additive genetic variation of heartwood diameter was estimated at 0.2. If a reliable ‘heartwood-meter’ becomes available that allows nondestructive measurements to be rapidly made in the field it should be possible to breed for or against heartwood formation with less effort compared with that required in breeding aimed at improving regular production traits.

Residual effects of N fertilization on soil-water chemistry and ground vegetation in a Swedish Scots pine forest

A study was made of soil-water chemistry and ground vegetation in a previously established N fertilization experiment in a Scots pine forest in central Sweden. Plots had been fertilized two, three or four times during a 15-year-period, each time with 150 kg N ha −1. The fertilizer used was initially pure ammonium nitrate, but at the latest fertilization made 4–8 years before the study, a minor dose of lime was also included. The aim of the study was to reveal possible residual affects of the previous fertilization. Soil water was sampled six times during a nine-month-period. Water samples were analyzed with respect to inorganic N, pH, Al, base cations and Cd. The only statistically significant treatment effect was that the concentration of base cations decreased with increasing total N dose in one of the two replicate blocks. Both fertilized plots and control plots had very low concentrations of inorganic N (<10 μg/l). Few species in the ground vegetation appeared to be affected by the previous N fertilization. Cladina rangiferina, the most abundant lichen species, had a much lower cover on plots that had been fertilized four times than on all other plots. Also, the other lichens tended to be less abundant on plots that had received fertilizer four times. The lower abundance of lichens on these plots resulted in a change in vegetation type from lichen types to dwarf shrub types. The experiment studied is situated in a region where deposition of N is larger than the critical load. Despite this, an extra addition of 600 kg N ha −1, corresponding to 40 kg N ha −1 year −1, had no consistent long-lasting effects on soil-water chemistry. At this dose, but not at the lower doses tested, there was a change in the plant community.

Population ecology of Suillus variegatus in old Swedish Scots pine forests

Spatial characteristics of Suillus variegatus populations, including the size, distribution and number of genets, were measured in four naturally regenerated stands of Scots pine, Pinus sylvestris in Sweden that were more than 100 years old. In the oldest forest, a continuous tree-layer had been present at least since the last forest fire in 1647. Genets were identified based on somatic incompatibility reactions performed on mycelial cultures from sporocarps. In total, 38 genets were identified from 120 tested sporocarps. The maximal extension of a genet, as reflected by its outermost sporocarps, was 27 m in the oldest stand and ranged between 10 and 17 m in the other stands. On average, genet size was 20 m in the oldest stand and 10 m in the other stands. Other genets were not found within the domains of established genets. The closest detected distance between genets was 1–5 m, and the average distance was 4 m. The number of genets ranged between 56 and 74 ha − at the studied sites. Possible reasons for the high degree of resemblance in characteristics in old forests between S. variegatus, the dominant bolete in mature forests, and S. bovinus when present, more a characteristic for younger forests and only scarcely occurring in older forests, are discussed.

Levels of outcrossing and contamination in twoPinus sylvestrisL. seed orchards in Northern Sweden

The joint levels of outcrossing and contamination in two young northern Swedish Scots pine (Pinus sylvestris L.) seed orchards were studied with the aid of allozyme markers. High levels of contamination (21–36%) were estimated and were attributed to the observed low within orchard pollen production. Outcrossing rate estimates were high (0.957–0.961), though they departed significantly from complete outcrossing (t= 1.0) in spite of the observed high contamination levels. These results confirmed reported relationships between outcrossing and contamination levels in open‐pollinated seed orchards. It was concluded that a crop management option relying on supplemental mass‐pollination would be effective in reducing both contamination and inbreeding levels.

Environmental persistence of the nuclear polyhedrosis virus of the European pine sawfly in relation to epizootics in Swedish Scots pine forests

A bioassay was used to study the occurrence of the nuclear polyhedrosis virus of Neodiprion sertifer in field-collected samples of foliage, soil, and other substrates in seven areas in southern and central Sweden. General contamination of the forest environment was found 1 year after an epizootic. Virus was demonstrated on both shaded and exposed pine foliage in two areas but activity levels were 10 and 100 times lower on exposed foliage. Based on virus activity on foliage, the primary infection level in a larval population was predicted to be 42%. The observed value was ca. 50%. Soil extracts contained 10 5 PIB/ml soil 1 year after an epizootic and 7 × 10 2 PIB/ml 9 years after an application of virus. It was concluded that virus surviving on foliage may infect larvae in the following generation, but that survival between sawfly outbreaks is unlikely. However, in soil, virus remained active for at least 13 years, longer than most intervals between outbreaks. Since, during an outbreak, the probability that a virus deposit on foliage will be ingested is high, an epizootic could start from a few such deposits.