Category: Research article
article id 1692, category Research article
Performance of lodgepole pine and Scots pine in field trials located in north-west Russia. Silva Fennica vol. 51 no. 1 article id 1692. https://doi.org/10.14214/sf.1692
Stem volume was bigger for lodgepole pine in comparison to local Scots pine except for the southernmost origin; The proportion of stems with no defects was lower for all lodgepole pine seed sources than for local Scots pine; Lodgepole pine stem growth traits were significantly related to latitude of seed origin.
Mortality, stem growth and quality of lodgepole pine (Pinus contorta var. latifolia) originating from the six Swedish seed orchards and local Scots pine (Pinus sylvestris L.) were estimated in four field trials established in the Komi Republic (north-west Russia). A randomized row-plot design with 6–12 replicates of each entry was used. The tree mortality was slightly higher for Scots pine than that for lodgepole pine, except for the lodgepole pine seed sources of the southern origins with lower survival. Scots pine stem quality was better than that of lodgepole pine, but the lodgepole pine stem growth was faster except the seed source of the southernmost origin. The lodgepole pine seed sources of northern origins had better stem growth (height, diameter at breast height and volume), while the effect of latitude on the quality traits was insignificant.
article id 1002, category Research article
Effect of growing density on biomass and stem volume growth of downy birch stands on peatland in Western and Northern Finland. Silva Fennica vol. 47 no. 4 article id 1002. https://doi.org/10.14214/sf.1002
Highlights: The thinning response in young downy birch stands was low and the mortality of merchantable stems was tolerable even in dense unthinned thickets during the rotation of 50 years; The production of above-ground woody biomass and stem volume or even the production of pulpwood increased with stand density, with these values being greatest for unthinned or very lightly thinned plots.
The objective of the study was to ascertain the relationship of thinning intensity of downy birch (Betula pubescens Ehrh.) stands with height, crown, and diameter development as well as pulpwood, stem volume, and biomass increment using long-term (20−30 years) field experiments. Diameter growth of birches increased with thinning intensity during the first 15 years from thinning in all development phases, though after that it did so only for the youngest stands. The thinning response was low. Thinning intensity had no influence on increase in height. In terms of stem volume with bark, the mortality in unthinned stands during the study period was 30–45 m3 ha-1. The mean stem number in unthinned birch thickets fell from 25 000 ha-1 at a dominant height of 7 m to 3000 ha-1 at 18 m. The stem volume increment over the first 15 years was highest (5–6 m3 ha-1 a-1) on the very lightly thinned or unthinned plots, but later there was no significant difference between initial thinning intensities. The maximum above-ground leafless biomass (over 100 Mg ha-1) was achieved on very lightly thinned plots. Also, the total production (including thinning removal) of biomass or stem volume or even the production of pulpwood increased with stand density, with these values being greatest for very lightly thinned or unthinned plots. During 50-year rotation, the highest leafless above-ground biomass production was 2.5 Mg ha-1 a-1 as a mean value from the experiments. The highest mean annual production of pulpwood (d > 6.5 cm) was 3.2 m3 ha-1 a-1, and, in practice, no saw timber or veneer timber was produced, because of the small size and low quality of the stems. A thinning in downy birch stands increased slightly the size of stems to be removed in future cuttings, but with exception for very light thinning it decreased the production of biomass and merchantable wood.
article id 973, category Research article
Spatially explicit structure of natural stands dominated by black spruce. Silva Fennica vol. 47 no. 3 article id 973. https://doi.org/10.14214/sf.973
Black spruce [Picea mariana (Mill.) BSP] regeneration emerges in clusters near the pre-existing boles within a few years after the passage of fire. This paper tested the hypothesis that black spruce forests still maintain the spatial structure deriving from postfire stand initiation. Trees and saplings were monitored during 2000-2007 and the horizontal and vertical structure of the stands were investigated on four permanent plots in the boreal forest of Quebec, Canada. Plots showed 1300-2150 trees ha-1, and were composed of trees with homogeneous sizes and a very small proportion of saplings. These characteristics identify single cohorts generated by complete, or almost-complete, stand replacement by fire. Ripley’s L(r) functions showed that the spatial pattern of trees and saplings ranged from random to aggregated, thus demonstrating that the clustering distribution of the individuals in black spruce forests can be maintained even after 80-120 years from stand initiation. These findings could results from incomplete self-thinning or from an environment with heterogeneous distribution of resources. The practices of ecosystem management recently developed in Eastern Canada should take into account both the horizontal and vertical structure to better modulate the competition among individuals during partial harvesting.
article id 903, category Research article
The contradictory role of understory vegetation on the success of Scots pine regeneration. Silva Fennica vol. 47 no. 1 article id 903. https://doi.org/10.14214/sf.903
In North-East Finland, severe problems have been encountered in the natural regeneration of Scots pine (Pinus sylvestris L.) on sites where regeneration through site preparation usually is quite successful. We hypothesized that in that area understory vegetation, especially heather (Calluna vulgaris), crowberry (Empetrum hermaphroditum), mosses and lichens, could play a key role in this pattern. We found that in general, ground- and field-layer vegetation tends to be in a negative relationship with the establishment, growth and survival of pine seedlings. Some positive relationships were also observed. Lingonberry (Vaccinium vitis-idea) tended to improve seedling height growth. Heather, instead, seemed to have a contradictory role. It was positively related to seedling establishment but negatively to seedling growth. This dual role raises further questions about the primary reasons for the regeneration problems in North-East Finland. All in all, our results suggest that conventional methods of forest regeneration in these kinds of areas are not always effective enough and additional measures are needed. These might include severe prescribed burning along with site preparation in order to decrease the impact of the dominant ground- and field-layer vegetation on the success of Scots pine regeneration.
article id 80, category Research article
Spatio-temporal variation of coarse woody debris input in woodland key habitats in central Sweden. Silva Fennica vol. 45 no. 5 article id 80. https://doi.org/10.14214/sf.80
The persistence of many saproxylic (wood-living) species depends on a readily available supply of coarse woody debris (CWD). Most studies of CWD inputs address stand-level patterns, despite the fact that many saproxylic species depend on landscape-level supplies of CWD. In the present study we used dated CWD inputs (tree mortality events) at each of 14 Norway spruce (Picea abies) dominated woodland key habitat sites to analyze the spatial and temporal patterns of CWD additions between 1950 and 2002 within a small landscape in central Sweden. We found that inputs were episodic within sites, where local windstorms created pulses in CWD input. Pulses occurred simultaneously in many sites, yielding landscape-level synchrony of CWD input. These synchronous pulses, and importantly, the breaks between pulses, may have negative implications for saproxylic species that are dependent on large volume inputs of freshly killed Norway spruce. In addition, the inherent small size and relative isolation of these sites may further increase extinction risks due to stochastic events. However, background CWD input rates occurring between pulses varied substantially among sites, presumably the result of the sites’ varied histories and structural characteristics. This finding suggests that the different sites have varied abilities to provide habitat for saproxylic species during periods with low landscape-level input of CWD.
article id 75, category Research article
Spatial structure in four Norway spruce stands with different management history in the Alps and Carpathians. Silva Fennica vol. 45 no. 5 article id 75. https://doi.org/10.14214/sf.75
In Europe most Norway spruce (Picea abies (L.) Karst.) mountain forests have been altered by human activities, leading to a lack of reference condition concerning their original structure. Nonetheless, remnants of Norway spruce primeval forests still exist in the Carpathians. Our objective was to assess the differences in structure between managed and unmanaged stands, concerning diameter distributions, amount of standing deadwood, spatial distributions and spatial structure of trees. We established four permanent plots: one in a virgin forest in the Eastern Carpathians and three in a previously managed forest in the Alps. In each plot, species, DBH, and position of the live and dead standing trees were collected. Spatial distribution and structure of all the trees was analysed through several indices. In the Carpathians forest there are clear signs of natural density-dependent mortality processes whereas in the Alpine plots such dynamics are less evident. In these latter plots, the lower snags volume and the random trees spatial distribution can be considered the legacies of past management. Nonetheless, despite the different history of the four stands, they all seem to converge towards a similar spatial structure with the presence of groups (30–40 m) of trees of similar size.
article id 32, category Research article
Developing post-fire Eucalyptus globulus stand damage and tree mortality models for enhanced forest planning in Portugal. Silva Fennica vol. 45 no. 1 article id 32. https://doi.org/10.14214/sf.32
Forest and fire management planning activities are carried out mostly independently of each other. This paper discusses research aiming at the development of methods and tools that can be used for enhanced integration of forest and fire management planning activities. Specifically, fire damage models were developed for Eucalyptus globulus Labill stands in Portugal. Models are based on easily measurable forest characteristics so that forest managers may predict post-fire mortality based on forest structure. For this purpose, biometric data and fire-damage descriptors from 2005/2006 National Forest Inventory plots and other sample plots within 2006, 2007 and 2008 fire areas were used. A three-step modelling strategy based on logistic regression methods was used. In the first step, a model was developed to predict whether mortality occurs after a wildfire in a eucalypt stand. In the second step the degree of damage caused by wildfires in stands where mortality occurs is quantified (i.e. percentage of mortality). In the third step this mortality is distributed among trees. Data from over 85 plots and 1648 trees were used for modeling purposes. The damage models show that relative damage increases with stand basal area. Tree level mortality models indicate that trees with high diameters, in dominant positions and located in regular stands are less prone to die when a wildfire occurs.
article id 31, category Research article
Snag characteristics and cavity-nesting birds in the unmanaged post-fire northeastern Canadian boreal forest. Silva Fennica vol. 45 no. 1 article id 31. https://doi.org/10.14214/sf.31
We studied the availability and characteristics of snags and their use by cavity-nesting birds in the northeastern part of the Canadian boreal forest. We built up two long-term (> 200 years) chronosequences following time since the last fire in the unmanaged boreal forest of northeastern Québec, one in the balsam fir-white birch domain (southern region) and one in the spruce-mosses domain (northern region). We then sampled and characterized snags and live trees in 30 stands from each of these two chronosequences. We also looked for nest cavities on all sampled snags, performed bird inventories by point counts, and calculated tree mortality rate from permanent sample plots. Results show that mortality rates follow a U-shaped pattern, with more snags of large diameter (> 20 cm DBH) in young (< 50 years) and in old (> 200 years) forests. In the latter, we also found more nest cavities than in any other age classes. Although abundance of primary cavity nesters (excavating species) did not vary among age classes, secondary cavity nesters (using cavities already available) tend to be more numerous in older forests. Our results highlight the capacity for young and old-growth forests to provide quality habitat for species that are dependent on large snags. Proper forest management should maintain a mosaic of different age forest stands, including snags, to promote biodiversity and provide important resources for resident bird species.
article id 468, category Research article
Tree mortality agents in pristine Norway spruce forests in northern Fennoscandia. Silva Fennica vol. 42 no. 2 article id 468. https://doi.org/10.14214/sf.468
We examined tree mortality agents in pristine old Norway spruce (Picea abies (L.) Karst.) forests in northern Finland and northwestern Russia. The data was collected on nine 40 m 400 m transects. The primary mortality agents of recently dead trees were recorded and their frequencies were calculated. The pattern of tree growth prior to death was studied based on increment core samples and compared with the growth of healthy dominant trees. Of all recently dead trees, 72% could be associated with a primary mortality agent. In both study areas the most common primary mortality agent was a Coniophora (Mérat) DC. -genus fungi, which was found on average in 33% of trees sampled. The fungi Phellinus chrysoloma (Fr.) Don and Onnia leporina (Fr.) H. Jahn as mortality agents were more common in the Finnish area compared to the Russian area. Analysis on the growth patterns indicated weak differences between different pathogens’ influence on prior-to-death growth of trees, so that fungi rotting the whole tree decreased tree growth more rapidly than fungi rotting only the heart wood. The results demonstrated that in old Norway spruce forests of northern Fennoscandia the most common primary tree mortality agents were wood rotting fungi, which weaken the mechanical stability of tree stems until they fall due to snow or wind, which should be considered only as secondary mortality agents. It is evident that tree death in pristine forest typically results from a long-lasting process involving both biotic and abiotic factors.
article id 329, category Research article
Natural regeneration of Scots pine and Norway spruce close to the timberline in northern Finland. Silva Fennica vol. 40 no. 3 article id 329. https://doi.org/10.14214/sf.329
Two different datasets were analyzed in order to clarify the factors that affect regeneration success of Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) in the climatically extreme areas in northern Finland. First, pine seed maturity and the number of cones in the trees were investigated at five pairs of study sites during the period 1997–2003. Secondly, the rate of seedling establishment and seedling survival of Scots pine and Norway spruce were monitored and compared among three different timberline zones (forest zone, timberline, tree line) in 13 localities during the period 1983–1999. The first study showed that both cone production (bud formation) and seed maturity may be limiting factors for successful reproduction in the climatically marginal habitats. Seed maturity correlated well with the temperature sum of the summer, but variation in the number of cones had a periodic component rather than strictly following the temperature sum of the summer of bud formation. Monitoring surveys since 1983 showed that pine and spruce regenerated more or less regularly in all the zones during 1983–1999. However, seedling mortality of pines was much higher compared to spruce. In general, initially small sized seedlings showed higher mortality compared with larger ones. The results suggest that besides restrictions in reproduction, stand dynamics in the timberline habitats are strongly controlled by seedling mortality due to a variety of causes.
article id 382, category Research article
Survival-time analysis of white spruce during spruce budworm defoliation. Silva Fennica vol. 39 no. 2 article id 382. https://doi.org/10.14214/sf.382
Mortality and defoliation (DF%) in 987 white spruce (Picea glauca (Moench) Voss) trees were followed from 1992 to 2003 during an outbreak of the spruce budworm Choristoneura fumiferana (Clem.) in 15 white-spruce-dominated uneven-aged stands in the Fort Nelson Forest District near Prince George, British Columbia. Four stands were aerially sprayed with Bacillus thuringiensis (Bt). Defoliation and mortality levels were elevated in non-sprayed stands. The relationship between defoliation and survival-times was captured in a Cox proportional hazard model with a defoliation stress index (DSI), diameter (DBH), crown class (CCL), a random stand effect, Bt-treatment, and number of years of exposure to stand-level defoliation (DYEAR) as predictors. The DSI, optimized for discrimination between survivors and non-survivors, is the discounted sum of five lagged DF% values. Survival probabilities were predicted with a maximum error of 0.02. Hazard rates increased by 0.06 for every one point increase in DSI. CCL and random stand effects were highly significant. Bt-treatment effects were fully captured by DSI, CCL, and DYEAR.
article id 408, category Research article
Natural development of stand structure in peatland Scots pine following drainage: results based on long-term monitoring of permanent sample plots. Silva Fennica vol. 38 no. 4 article id 408. https://doi.org/10.14214/sf.408
We studied the dynamics of stand structure on drained peatland sites in Scots pine dominated stands untreated with thinnings. The data consisted of consecutive stand measurements in 10 permanent sample plots where the monitoring periods varied from 29 to 66 years. We assumed that the stand’s structural development was driven by the natural processes of regeneration, growth, and mortality, all related to inter-tree competition within the stand. The DBH distributions of live and dead trees at different times of post-drainage stand development – smoothed by Weibull function – were analysed to characterise the change in stand structure. The initial uneven-sized structure of the natural, widely-spaced stands became more uneven during the first decades following drainage due to enhanced regeneration. Later, as stand density and mean tree size continuously increased, the DBH distributions approached bell-shaped distributions. Accordingly, the suppressed trees showed their highest mortality rate during the first decades, but the peak of the mortality distribution shifted to larger trees along stand succession. The change in structure was faster in southern Finland than in northern Finland. We assumed the changes in stand dynamics reflected increased inter-tree competition, initiated by enhanced site productivity and increased stand stocking resulting from the ditching operation.
article id 504, category Research article
Modeling mortality of individual trees in drained peatland sites in Finland. Silva Fennica vol. 37 no. 2 article id 504. https://doi.org/10.14214/sf.504
Multilevel logistic regression models were constructed to predict the 5-year mortality of Scots pine (Pinus sylvestris L.) and pubescent birch (Betula pubescens Ehrh.) growing in drained peatland stands in northern and central Finland. Data concerning tree mortality were obtained from two successive measurements of the National Forest Inventory-based permanent sample plot data base covering pure and mixed stands of Scots pine and pubescent birch. In the modeling data, Scots pine showed an average observed mortality of 2.73% compared to 2.98% for pubescent birch. In the model construction, stepwise logistic regression and multilevel models methods were applied, the latter making it possible to address the hierarchical data, thus obtaining unbiased estimates for model parameters. For both species, mortality was explained by tree size, competitive position, stand density, species admixture, and site quality. The expected need for ditch network maintenance or re-paludification did not influence mortality. The multilevel models showed the lowest bias in the modeling data. The models were further validated against independent test data and by embedding them in a stand simulator. In 100-year simulations with different initial stand conditions, the models resulted in a 72% and 66% higher total mortality rate for the stem numbers of pine and birch, respectively, compared to previously used mortality models. The developed models are expected to improve the accuracy of stand forecasts in drained peatland sites.
article id 554, category Research article
Tree mortality in a Pinus sylvestris dominated boreal forest landscape in Vienansalo wilderness, eastern Fennoscandia. Silva Fennica vol. 36 no. 1 article id 554. https://doi.org/10.14214/sf.554
Tree mortality and its causes and spatial pattern were examined along four transects (width 40 m, length 2550–3960 m), with a total length of 12 190 m and area of 48.8 ha, in a Pinus sylvestris L. dominated, boreal forest landscape. Tree mortality was determined within a time window of 3 years by identifying those trees (dbh ≥ 10 cm) along the transects that fitted into one of the three categories: 1) current mortality: trees that had died during the year of survey (1998), 2) recent mortality: trees that had died during the year (1997) before the survey year, and 3) predicted mortality: trees that were expected to die during the year (1999) following the survey year. Long-term tree mortality was studied on 10 plots (20 m x 100 m) by dating 87 dead trees using dendrochronological methods. The mean current mortality was 1.4 m3 ha–1 (3.7 trees ha–1). Both the recent and predicted mortalities were also 1.4 m3 ha–1. Mortality was, on the average, higher on peatlands than on mineral soils. The highest mortality was found within an area recently flooded by beavers. Over half of the examined trees (52%) were judged to die without any visible signs of an external abiotic cause. At the landscape scale, tree mortality was continuous although somewhat aggregated in space. Of the 66 dated standing dead Pinus trees, 23 (35%) had died during the 19th century and two during the 18th century, demonstrating that dead Pinus can remain standing for long periods of time before falling. Our results show that autogenic mortality of individual trees or small groups of trees was the predominant mode of disturbance in this Pinus dominated landscape.
article id 675, category Research article
Tree mortality after prescribed burning in an old-growth Scots pine forest in northern Sweden. Silva Fennica vol. 32 no. 4 article id 675. https://doi.org/10.14214/sf.675
Tree mortality and input of dead trees were studied after a prescribed burning in a forest reserve in northern Sweden. The stand was a multi-layered old-growth forest. The overstorey was dominated by Scots pine (Pinus sylvestris L.) and the understorey consisted of mixed Scots pine and Norway spruce (Picea abies L. Karst.). Ground vegetation was dominated by ericaceous dwarf-shrubs and feathermosses. The stand has been affected by six forest fires during the last 500 years. The prescribed burning was a low intensity surface fire that scorched almost 90% of the ground. Tree mortality for smaller pines and spruces (DBH < 10 cm) was over 80% in the burned parts of the reserve. For larger pines, 10–50 cm DBH, mortality showed a decreasing trend with increasing diameter, from 14% in class 10–20 cm DBH to 1.4% in class 40–50 cm DBH. However, pines with DBH ≥ 50 cm had a significantly higher mortality, 20%, since a high proportion of them had open fire scars containing cavities, caused by fungi and insects, which enabled the fire to burn inside the trunks and hollow them out. The fire-induced mortality resulted in a 21 m3 ha–1 input of dead trees, of which 12 m3 ha–1 consisted of trees with DBH ≥ 30 cm. An increased mortality among larger trees after low-intensity fires has not previously been described in Fennoscandian boreal forests, probably owing to a lack of recent fires in old-growth stands. However, since large pines with open fire scars were once a common feature in the natural boreal forest, we suggest that this type of tree mortality should be mimicked in forestry practices aiming to maintain and restore natural forest biodiversity.
Category: Review article
article id 687, category Review article
Pine mortality after planting on post-agricultural lands in South Africa. Silva Fennica vol. 32 no. 3 article id 687. https://doi.org/10.14214/sf.687
Successful afforestation has been practiced in South Africa for more than a century. Recently, however, problems with afforestation of pines have occurred in the northeastern part of the Eastern Cape Province. Rapid mortality of Pinus patula and P. elliottii have occurred when small container seedlings were planted on old-agricultural soils. Death would often occur within 5 months of planting. Growth of surviving trees was retarded and new needles were chlorotic and stunted. Acceptable survival was obtained when seedlings were planted on virgin grasslands. Apparently, some unseen factor in the post-agricultural soil reduces root growth, increases mortality, and decreases uptake of nutrients. Removal of the infested soil by scalping greatly improves survival and growth as does soil fumigation with methyl bromide.
Category: Research note
article id 9901, category Research note
Statistics of ash dieback in Latvia. Silva Fennica vol. 52 no. 1 article id 9901. https://doi.org/10.14214/sf.9901
Highlights: Dynamics of ash dieback during 2005–2015 were summarized; The area of ash dominated stands decreased twofold; The number of mature ash trees and their standing volume decreased by 53.1 and 69.9%, compared to 2005, respectively; The mortality of trees was higher during the first part of the survey, the decrease of standing volume culminated later.
Dieback of the common ash (Fraxinus excelsior L.) has been spreading throughout Europe since the 1990s, causing severe ecological and economical consequences; however, detailed statistics on its dynamics have been published rarely. This paper presents the dynamics of mature ash-dominated stands in Latvia for the period 2005–2015. Data from the national forest inventory and a permanent sampling plot network were summarised. According to the official statistics, the dieback has caused a twofold decrease in area of the ash stands (from 21 891 to 13 011 ha, which respectively comprised ca. 0.8 to ca. 0.4% of the total forest area). The official statistics on standing volume appeared biased, as they did not account for increased mortality. According to the permanent sampling plots, standing volume and stand density have been affected even more, having decreased by 53.1 and 69.9%, respectively, compared to 2005 (the stand density and standing volume of ash in 2015 was 77 individuals ha–1 and 151 m3 ha–1, respectively). The mortality of the trees has not been stable. Stand density decreased faster during 2005–2009 compared to 2010–2015, with mortality rates of 9.6 and 8.2% year–1, respectively. In contrast, the decrease in standing volume in 2005–2009 was slower than in 2010–2015 (mortality rates were 4.7 and 7.7% year–1, respectively) because trees with smaller dimensions were more susceptible to the dieback. Nevertheless, the observed mortality rates clearly indicate negative prospects for ash stands in Latvia.
article id 1656, category Research note
Survival of European beech in the central part of Latvia 33 years since the plantation. Silva Fennica vol. 50 no. 4 article id 1656. https://doi.org/10.14214/sf.1656
Highlights: Beech saplings growing in the central part of Latvia had ca. 80% survival during the recent three decades; The dimensions of saplings varied greatly likely due to canopy conditions; Some beech self-regeneration was observed; Mainly saplings had narrow crowns; The distribution of sapling dimensions had the reverse-J shape, suggesting successful development of beech.
The projections of vegetation zones suggest increasing growth potential of European beech (Fagus sylvatica L.) in Northern Europe. Such changes usually are most apparent in the marginal populations. In this study, survival of young beech growing in an experimental plantation under canopy of a mixed coniferous stand in the central part of Latvia was assessed after 33 years since the establishment. The planting material originated from an older experimental stand in the western part of Latvia. Although, at present, the studied plantation could be considered as the northeasternmost beech stand in Europe, a good survival was observed – ca. 80% of the seedlings have survived, despite several cold spells of ca. –30 °C that occurred during the recent three decades. Additionally, some self-regeneration i.e. branch sprouting was observed. The saplings were rather low, as their mean height was ca. 4 m. Still, some individuals, which were growing under canopy openings, reached considerable dimensions; their height and stem diameter exceeded 10 m and 9 cm, respectively. The distribution of sapling dimensions had the reverse-J shape that is typical for shade tolerant species, indicating normal development of the beech regrowth. The crowns of saplings were narrow and the stems were spindly, suggesting that trees with a good stem quality might be bred. Hence, our results suggest that environmental conditions in the central part of Latvia have been satisfactory for beech, thus encouraging establishment of more extensive trials within the region.
article id 1145, category Research note
Ips acuminatus kills pines in southern Finland. Silva Fennica vol. 48 no. 4 article id 1145. https://doi.org/10.14214/sf.1145
Highlights: Recently dead pines colonized by Ips acuminatus were frequently found in southern Finland, in a region where the species was thought to be absent; Colonized trees were typically large (average DBH 30 cm), located at open spots in pine-dominated stands, often forming groups of several trees; The damages may be a consequence of dry and hot summers during the 2000s.
Recently dead Scots pines (Pinus sylvestris L.) apparently killed by Ips acuminatus (Gyllenhal) were observed in Sipoo, southern Finland, in summer 2013. This record was unexpected and in contradiction with what is currently known about the distribution and aggressiveness of the species in Finland. The aim of this study was to survey a larger area in Uusimaa region, to find out whether I. acuminatus occurs frequently in recently dead pines, and whether inhabited trees share some common tree- or site-level characteristics. Galleries of I. acuminatus were found in most of the studied trees. A total of 96 inhabited trees were found in 21 separate sites. Colonized pines were typically large (average DBH 30 ± 9 cm) trees located in relatively open pine-dominated heathland stands at half-open, sun-exposed spots. The whole upper part of the trunk with thin bark was usually occupied. Galleries of Tomicus piniperda L. or T. minor Hartig occurred only in few cases in the same trees, indicating that the trees had died later in the summer. Galleries of the jewel beetle Phaenops cyanea F. were found in 13 trees. Trees colonized by I. acuminatus often occurred as small groups, with generally 1–12 trees (average 3 trees), but in one exceptional group there were no less than 35 trees. It is possible that the hot and dry summers during the 2000s have increased the susceptibility of pines to insect damage, and have contributed to a population growth of I. acuminatus.
article id 5541, category Article
Performance of micropropagated plants of silver birch (Betula pendula) in a field trial. Silva Fennica vol. 28 no. 4 article id 5541. https://doi.org/10.14214/sf.a9181
Micropropagated and seed-borne plants of sliver birch (Betula pendula Roth) were compared for survival and growth in a field trial at the age of six years. Three clones for micropropagation were selected from open-pollinated progenies of selected southern Finnish plus trees at the age of 17 and 20. The three seed-borne lots were of southern Finnish stand origin. The best two lots of the experiment as regards the height and diameter growth at the age of six were the clones. The best of these differed significantly from the best-growing seed-grown lot. The weakest lot of the experiment was also a clone which was clearly slow-growing with a dense and bushy crown. Survival of the material was high (mean = 94%), and there was no damage caused by voles and elks, for example. The results clearly show that the selection of material for clonal propagation should be done carefully. The clones should also be tested for performance in the field before propagation on a large scale.
article id 5521, category Article
The survival of forest tree species in wildfires was examined on two burned stands. Norway spruce (Picea abies (L.) H. Karst.) and birches (Betula spp.) proved to be sensitive to the effects of wildfire; almost all individuals of these tree species were killed by the fires. Scots pine (Pinus sylvestris L.) was more tolerable to the effects of wildfire; i.e. one out of five Scots pines survived. Fire tolerance increased as tree size increased.
The PDF includes an abstract in Finnish.
article id 5445, category Article
Kuusen kylvö- ja istutuskoe viljavilla kivennäismailla Pohjois-Karjalassa. Silva Fennica vol. 25 no. 2 article id 5445. https://doi.org/10.14214/sf.a15599
English title: (1991). Results from the sowing and planting experiment of Norway spruce (Picea abies) on fertile sites in North Karelia, Finland.
Different methods of sowing and planting of Norway spruce (Picea abies (L.) H. Karst.) were compared on fertile sites in North Karelia (62°20’N, 29°35’E, 85–120 m a.s.l.). The planting material were 4-year-old bare-rooted transplants, 2-year-old bare-rooted seedlings, and 2-year-old containerized seedlings raised in plastic greenhouse. The sowing methods were band sowing and shelter sowing. Ground vegetation was controlled during the first growing season mechanically or chemically, or the control was omitted totally.
Planting of spruce gave better results than sowing. After eight growing seasons there were sowed seedlings left in 30% of the sowing pots. The average height of them was 35 cm. Seedling survival was best with large bare-rooted transplants (91%). Survival of containerized seedlings was 79% and of small bare-rooted transplants 71%. The average height of large bare-rooted transplants was 131 cm, of containerized seedlings 86 cm and small bare-rooted seedlings 68 cm.
Sowing is not an advisable method for regeneration of spruce due to the small survival rate and slow initial development when ground vegetation is controlled only once. Also 2-year-old seedlings gave a satisfactory result in regeneration. Seedlings raised in greenhouse were more sensitive to frost damage than seedlings grown on open ground.
The PDF includes an abstract in English.
article id 5382, category Article
Simulations on the occurrence of dead trees in natural pine stands. Silva Fennica vol. 23 no. 3 article id 5382. https://doi.org/10.14214/sf.a15539
The study aimed at recognizing the phases of forest succession where dead trees most probably occur. The model simulations showed that the increasing occurrence of dead trees culminated after the canopy closure. Thereafter the occurrence of dead trees decreased representing a pattern where high frequency of dead trees was followed by low frequency of dead trees, the intervals between the peaks in the number of dead trees being in Southern Finland about 15–30 years. Around this long-term variation there was a short-term variation, the interval between the peaks in the number of dead trees being 2–4 years. This pattern was associated with the exhausting and release of resources controlled by the growth and death of trees.
The PDF includes an abstract in Finnish.
article id 5305, category Article
Simulation model for natural regeneration of Pinus sylvestris, Picea abies, Betula pendula and Betula pubescens. Silva Fennica vol. 21 no. 1 article id 5305. https://doi.org/10.14214/sf.a15462
In the model the regeneration process is derived into three subprocesses: birth, growth and mortality of seedlings. The main emphasis is on the birth process where the following phases are simulated: seed crop, quality of seeds, maturity of seeds, predation of seeds and germination. The parameters are based on data published in Finland. Part of the parameters are obtained directly from the investigations and part is proposed by the author. The model can be calibrated by changing parameter values. The simulation is made with the help of random numbers which have the same means as the estimates and the same distributions as the residuals of the equations used in simulation. The time step of the model is one year. The number of emerged seedlings in one year is obtained by multiplying the seed crop with the probabilities that the seed passes different phases of the birth process. Because of stochasticity the regeneration period is simulated several times. From the results it is possible to evaluate the risk and succeeding probability of the regeneration. The main drawbacks of the simulation method are the lack of empirical parameters and the difficulty of testing. The model could be further developed by including spatiality into the model.
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article id 5188, category Article
Vuosina 1970-1972 Lappiin perustetun aurattujen alueiden viljelykokeen tulokset. Silva Fennica vol. 17 no. 3 article id 5188. https://doi.org/10.14214/sf.a15171
English title: (1983). Results from the reforestation experiment on ploughed sites established in Finnish Lapland during 1970–1972.
The objective of the study was to compare different reforestation methods on ploughed areas in Finnish Lapland. Four species were compared: Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L.) H. Karst.), silver birch (Betula pendula Roth) and Siberian larch (Larix sibirica Ledeb.). The experiments were established in different parts of Lapland on different types of sites in 1970–72.
In Scots pine there was a difference of 15 percentage points in survival of seedlings between the best and worst methods of regeneration. Containerized seedlings and paper pot seedlings had the best survival rates. In Norway spruce the respective difference between sowing and planting was about 20 percentage points. In favour of planting. The survival rate can be increased by about 20 percentage points by selecting the right tree species. The average height varied from 25 cm (the sowed Norway spruce) to 179 cm (the planted silver birch) after 10 growing seasons. The birch was planted at the most fertile sites only. The longer time passed from the afforestation the clearer was the effect of the local growing conditions on the development of the seedlings. The elevation of the site was one factor seemed to influence the success of the seedlings.
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article id 4983, category Article
The effects of air pollution on provenances of Scots pine and Norway spruce in northern Finland. Silva Fennica vol. 12 no. 1 article id 4983. https://doi.org/10.14214/sf.a14837
The success of certain Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) H. Karst.) provenances from Northern Finland was studied in a tree damage area occasioned by air pollution in the town of Oulu over the period of 1972-76. The pine strains from more northerly and easterly areas and the spruce strains from the immediate vicinity of the site itself were being observed to thrive best. The results point in a similar direction to those of other comparable experiments, except that the mortality rate amongst the saplings was exceptionally high and the proportion of healthy saplings in good condition was found to be unusually low. Structural properties suggestive of resistance to pollution were observable selectively in certain provenances, these including the xeromorphy of needles or thickness of the epidermis. The chief cause of mortality amongst the saplings was found to be the damage inflicted by pollution during the winter, while that arising in the summer months was relatively slight.
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article id 4954, category Article
Förrådsgödsling av rotande tallplantor med olika kvävegödselmedel. Silva Fennica vol. 10 no. 4 article id 4954. https://doi.org/10.14214/sf.a14800
English title: (1976). Fertilization of Scots pine seedlings with different nitrogen fertilizer.
The paper describes an attempt to determine whether ammonium, nitrate and urea nitrogen are bound in peat used as a filling material in containerized seedling production, what is the effect of the nutrients on certain chemical properties in the peat, and what is the effect of the nitrogen fertilizers on the primary growth of containerized (paper-pot VH 608) Scots pine (Pinus sylvestris L.) seedlings in connection with planting out. The seedlings were fertilized with ammonium sulphate, potassium nitrate and urea.
The results show that none of the fertilizers used were bound in the peat. The nitrogen content in the above ground part of the seedlings increased clearly. Fertilization with ammonium sulphate resulted in the greatest increment and this increase appears to be permanent. The wintering process was somewhat delayed by the fertilization. The seedling mortality rate for all the treatments has been quite appreciable. However, fertilization particularly with ammonium sulphate on the poorer of the two sites studied has had a positive effect on seedling survival. Furthermore, it appears that fertilizer treatments have decreased growth after planting, but in the case of ammonium sulphate this decrease has changed into a clear growth increment.
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article id 4876, category Article
Kokemuksia rauduksen istutuksesta ojitetuille soille. Silva Fennica vol. 7 no. 1 article id 4876. https://doi.org/10.14214/sf.a14706
English title: (1973). Betula verrucosa plantations on peat.
The aim of the present study was to assess whether two-year old Betula verrucosa Ehrh. (now Betula pendula Roth.) transplants can be used in afforestation of drained peatlands and what factors affect the development of the young trees. The seedlings were planted in 1967. The site was repair planted next spring due to mortality caused by a undefined fungal disease, and the plantations were fertilized with NPK fertilizer (soil application. The seedlings were measured twice a year until the autumn 1970.
Only 28% of the original transplants, and 73.4% of the repair plantations were alive in 1970. In some cases, fertilization improved the results, while in others it was detrimental to the trees or had no effect on survival. According to peat analysis, the poor survival and development of the plants could be due to the too high ratios of N/Ca and N/P. Stunted or dead trees displayed often necrosis caused by Godronia multispora. According to the experiences, Betula verrucosa plantations are inferior to those obtained with Scots pine (Pinus sylvestris L.). In addition, the results indicate that in old draining areas calcium and phosphorus are often too low in comparison to nitrogen.
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article id 4859, category Article
Istutuskuoppaan annetun kuparihienofosfaatin vaikutus männyn ja kuusen taimien elossapysymiseen ja pituuskasvuun eräällä kulotetulla ja auratulla uudistusalalla Koillis-Suomessa. Silva Fennica vol. 6 no. 1 article id 4859. https://doi.org/10.14214/sf.a14662
English title: (1972). Effect of fine-grounded copper rock phosphate placed in the planting hole on the survival and height growth of Scots pine and Norway spruce in a burnt and furrowed reforestation are in northeast Finland.
The paper describes the results of a fertilization experiment, in which transplants of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) H. Karst.) were fertilized with various doses of fine-ground copper rock phosphate (33% P2O5, 4% Cu) placed direct in the planting hole. The experiment was made in northeast Finland on a clear-cut, burnt-over and furrowed moraine heath. The fertilization increased especially the survival and condition of the Scots pines and increased to some extent also the height growth of the plants. The spruce survived better than the pines.
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article id 4849, category Article
Eräiden talvivarastointimenetelmien vaikutuksesta männyn taimiin. Silva Fennica vol. 5 no. 3 article id 4849. https://doi.org/10.14214/sf.a14651
English title: (1971). The effect of some over-winter storage methods on different Scots pine nursery stock.
Seedlings of three different Scots pine (Pinus sylvestris L.) nursery stock, 1+0 ,1+1, and 2+0, were kept over the winter, after they had been packed in polythene bags, in three different ways: 1) In a refrigerated storage room, 2) in a wooden crate in the ground, 3) submerged in a lake. The seedling to which they were to be compared with were left over the winter in a nursery bed. The 1,800 seedlings were planted out in the spring 1966 in 15 random blocks. Their development was scrutinized during the three subsequent falls.
The seedlings which had been stored in the lake all died. The seedlings which had been stored along the 1st and 2nd method, managed almost as well as the ones which had been kept over the winter in the nursery bed, except for those of 1+0 stock.
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article id 4847, category Article
Männyn erilaisten taimierien istutuskelpoisuudesta. Silva Fennica vol. 5 no. 3 article id 4847. https://doi.org/10.14214/sf.a14649
English title: (1971). The effect of differences in Scots pine nursery stock on the field survival and growth.
Scots pine (Pinus sylvestris L.) seedlings were stored for five days in an ordinary wood shed. One half of the seedlings were planted out directly, and another half after soaking the roots of the seedlings for 3–6 hours in water to compensate the possible water deficit developed. According to the results of the experiment, the effect of watering was extremely small. The difference observed, which was in favour of the trees that had been watered during storage, was discernible only in the needle length and in the number of lateral buds; in mortality or in the growth of the seedlings no difference could be observed.
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article id 4841, category Article
Lannoituksen vaikutus kylvösten ensi kehitykseen turvealustalla. Silva Fennica vol. 5 no. 2 article id 4841. https://doi.org/10.14214/sf.a14643
English title: (1971). Effect of fertilization on the initial development of Scots pine and Norway spruce plantations established by sowing on peat.
Experiments were carried out to find out the effect of fertilizer application on germination, seedling emmergnece and initial development in conifer plantations established on peat by sowing, with a special reference to Scots pine (Pinus sylvestris L.). The experiments were carried out in 1968–70 in laboratory, in greenhouse and in the field.
In the greenhouse experiments with Y fertilizer for peat soils (14% N, 18% P2O5, 10% K2O) it was shown that germination and seedling emergence decreased markedly with increased fertilizer application. Mortality among seedlings that had emerged was the higher the larger quantities of fertilizer had been applied. The effect of fertilization was the greater, the drier the substrate. Fine ground rock phosphate (33% P2O5) promoted seedling emergence on a dry substrate but not on a wet one.
The field experiments carried out in Central Finland included dry and wet sites. Y fertilizer, Oulu Saltpeter (25% N), fine-ground rock phosphate and potassium salt (50% K2O) were used. According to the results, easily soluble fertilizers decreased seedling emergence. On wet sites the effect of Y fertilizer was weaker than on drier sites. Fine-ground rock phosphate slightly increased the number of seedlings emerging. Height growth was increased during the first three growing seasons only by those fertilizers containing phosphorus.
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article id 4838, category Article
Metsityslannoituksessa käytetyn lannoitemäärän ja levitystavan merkitys istutustaimiston alkukehitykselle ojitetuilla avosoilla. Silva Fennica vol. 5 no. 2 article id 4838. https://doi.org/10.14214/sf.a14640
English title: (1971). The quantity of fertilizer and application methods used in afforestation of open bogs.
The paper describes the results obtained from an experiment of fertilization of drained treeless peatlands in connection of planting in three sites in Central Finland. Scots pine (Pinus sylvestris L.) seedlings 2+0 was used. The fertilizer (Y-fertilizer for peat soils, 14% N, 18% P2O5, 10% K2O) was applied in rates of 0, 20, 40 and 80 g/transplant. The fertilizer was strewn either around the plant within a circular patch of 20 cm in diameter, in a ring with a radius of 10 cm and in a ring with a radius of 20 cm. The seedlings were measured two and five years after planting.
The greater the quantity of fertilizer applied and the closer it was applied to the plant the higher was the mortality of transplants. Fertilization increased the mortality during the first two growing seasons after application. Later, however, the mortality decreased to a similar level irrespective the way the fertilizer was applied. In the beginning of the second growing season the fertilized plants showed considerably better height growth than the control plants. The smallest quantity of fertilizer applied produced almost full increase in growth. The pattern of application of the fertilizer had little effect on the growth.
It was concluded that a use of small amounts of fertilizer can be recommended in connection with planting and that it should not be applied very near the seedlings.
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article id 4834, category Article
Viktförlust, vattenhalt och plantavgång hos kyllagrade tallplantor. Silva Fennica vol. 5 no. 1 article id 4834. https://doi.org/10.14214/sf.a14623
English title: (1971). Weight loss, water content and mortality of cold stored Scots pine seedlings.
The aim of this study was to investigate how the weight loss and water content of cold stored plants depend on the storage conditions, and if there is a clear connection between these factors and the field survival of the planting stock. The experiments were carried out in a climate chamber at about +2°C and at three moisture levels (about 70, 85, and 95%) from November 1968 to May 1969. Three-year-old seedlings of Scots pine (Pinus sylvestris L.) average length 127 mm, diameter 3.5 mm and the top/root-ratio of fresh weight 1.93, were stored in open and sealed plastic bags. In addition, a transpiration retardant (Silvaplast) was used. The plastic bags (10 plants each) were weighted every 4. week. The remaining 270 seedlings were planted out and inspected after one growing season.
Although the experiment was made in a small scale, the results showed clearly that plant mortality, varying between 3 and 97%, was due to the storage conditions. The weight loss ranged between 2 and 50%, and the correlation between the weight loss and the mortality in the field was high. The water content of the seedlings was about 61%. The correlation between water content and survival was very high. Thus, the determination of weight loss or water content could be a useful method in observing the changes of water balance of the seedling stock during winter-storage. Further investigations are needed to show the tolerable rate of drying out for different sorts of plants. The Silvaplast-treatment had no visible effect either on the drying out or on the field survival.
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article id 4812, category Article
Pakkauksen, varastoimisen ja valeistutuksen vaikutus männyn taimien istutuskelpoisuuteen. Silva Fennica vol. 4 no. 1 article id 4812. https://doi.org/10.14214/sf.a14601
English title: (1970). The effect of packing, storing and heeling-in on the field survival and growth of Scots pine seedlings.
The aim of the present study was to establish, by means of planting experiments, the influence of different packing, heeling-in and watering as well as the length of the storage period on the development of Scots pine (Pinus sylvestris L.) seedlings, in all 2,090 seedlings, that had been lifted from the nursery bed in spring. The plants were packed in bundles and into plastic sacks in 1965 (6 storage methods) and in 1966 (3 storage methods). Control seedlings were planted without storing at the time when storage of the test material begun. The plantations were followed 3–4 years.
Storage for two weeks in the different ways and planting without storage gave similar results when seedling survival was compared. Storage in plastic sack proved to be as good as storage in bundles in a cellar, and healing-in in moist soil or in a drain were both usable methods. Watering the seedlings did not improve the results, which indicates that the storage caused no serious lack of water.
After four growing seasons an average of 19,6% of the seedlings of the 1965 experiment died, the bulk of them by the end of the first growing season. Despite control treatment, Hylobious abietis caused serious damages. In the plantations of the year 1966 mortality of the seedlings was under 5% by the end of third growing season. During the first two growing seasons after planting differences in growth of the seedlings stored in different ways could be observed in the plantations of the year 1965, but the differences levelled out later. In the plantations established in 1966 no differences in growth occurred.
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article id 4803, category Article
Männyn ja kuusen siemenien esikäsittelyn vaikutuksesta itämiseen ja taimien alkukehitykseen kasvihuoneoloissa. Silva Fennica vol. 3 no. 3 article id 4803. https://doi.org/10.14214/sf.a14591
English title: (1969). The effect of treatment of Scots pine and Norway spruce seeds on their germination and the early development of the seedlings.
The aim of this study was to establish the need of treatment of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) H. Karst.) seeds to be sown in greenhouse. 3 x 100 seeds of each treatment (soaking in water, treatment with Pb3O4, treatment with tiram-containing coating substance) were sown in a glasshouse on a fertilized garden peat, and covered with peat layer of 6 mm thickness. The development of seedlings was followed for 100 days before the final measurement.
Soaking the seeds with water made germination somewhat faster. In spruce the germination percentage increased, but the opposite was observed in pine. No difference could be observed between the results from soaking with acid water from peat soil and lake water. Drying the soaked seeds for a week before sowing had no harmful influence on the germination or the early development of the seedlings. Treatment with Pb3O4 did not affect the germination speed or the seedling percentage of pine or spruce, but increased the germination percentage of spruce. Coating decreased germination and seedling percentages in pine. However, the differences between the treatments were so small that their practical significance is negligible.
Germination of both the species initiated on an average in 8 days, and 16 days after sowing 80% of the seeds had germinated. Seedling mortality was about 10% of the total number of seedlings, the most common reason being damping-off.
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article id 7548, category Article
Lannoituksen ja sarkaleveyden vaikutus rämeen uudistumiseen ja taimien kasvuun. Acta Forestalia Fennica no. 114 article id 7548. https://doi.org/10.14214/aff.7548
English title: (1971). Effect of fertilization and ditch spacing on regeneration and seedling growth in pine swamps.
In 1965 and 1966 a total of 25 experiments were laid out in various parts of Finland in order to find out the effect of simultaneous variation in the intensity of drainage and fertilization on the development of plantations and natural seedling stands of Scots pine (Pinus sylvestris L.) growing on pine swamps. The fertilizer used was Y fertilizer for peat soils, a fertilizer mixture containing 14 % N, 18 % P2O5 and 10 % K2O. It was applied in rates of 500, 1,000 and 1,500 kg/ha. The ditch spacings studied were 10, 20 and 30 m. The present paper is a preliminary report on a series of studies, the experiments will be observation for a total of 15–20 years.
Mortality of the planted seedlings was found to be the higher after the first growing season, the larger the quantity of fertilizer that had been applied. Fertilizing caused an increase in seedling mortality even after the first growing season following application. At the end of the fifth growing season the height of both natural and planted seedlings is the greater, the larger the quantity of fertilizer that has been applied. Analysis of the height growth of the seedlings showed that larger quantities of fertilizer did not increase growth in the same proportion. The occurrence of growth disturbances is the greater, the more fertilizer has been applied.
Fertilization also changed the composition of ground vegetation. The in the beginning of the experiment birch (Betula sp.) was absent in the area, but was found in the stands the greater abundance the higher application of the fertilizer.
From the viewpoint of growth of the seedlings the best results were obtained with the greatest intensity of fertilization and the narrowest ditch spacing used in the study. The results also show that strong fertilization and a high degree of drainage intensity are not capable of bringing about any particularly good growth on peatlands which originally are relatively poor in nutrients. The growth values now obtained equal only one third of those obtained on peat soils of greater fertility.
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article id 7546, category Article
Nostoajankohdan, pakkaustavan, varastointiajan pituuden ja kastelun vaikutuksesta männyn taimien kehitykseen. Acta Forestalia Fennica no. 112 article id 7546. https://doi.org/10.14214/aff.7546
English title: (1970). The effect of lifting date, packing, storing and watering on the field survival and growth of Scots pine seedlings.
This study was carried out in 1966 in the nursery at Hyytiälä, Korkeakoski Forest District, in Southern Finland. The influence of lifting date (two liftings), way of packing (two methods) and length of storage (one, three and six weeks) on the development of Scots pine (Pinus sylvestris L.), 2 + 1, during the four years following planting was assessed. On the seedlings stored for six weeks, the influence of compensating for the water deficit was also studied.
According to the results, the lifting carried out later, i.e. when the seedlings had already started growth, gave slightly better results than when seedlings were lifted earlier. No difference could be observed for seedlings stored for one week, but for the seedlings stored for three or six weeks, mortality in the lot lifted earlier was 6- to 7-fold that of the seedlings lifted later. The main reason for this was probably that the seedlings of the earlier lifting suffered from lack of water at the time of lifting.
The growth of the seedlings lifted earlier and stored for three weeks showed a decrease compared to those lifted later. For the seedlings stored for six weeks, on the other hand, faster growth was recorded for both the seedlings of the earlier and the later lifting in comparison with those stored for shorter times. Watering increased to some extent the growth of the seedlings stored for six weeks.
During the normal, one- and three-week storing periods, seedlings were well preserved when packed both in bundles and in polythene sacks. Three years after the planting the average mortality was about 10%. Effect of watering was large for those seedlings that had been longer in the storage.
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