Category: Research article
article id 677, category Research article
Analysing uncertainties of interval judgment data in multiple-criteria evaluation of forest plans. Silva Fennica vol. 32 no. 4 article id 677. https://doi.org/10.14214/sf.677
The use of interval judgments instead of accurate pairwise comparisons has been proposed as a solution to facilitate the analysis of uncertainties in the widely applied pairwise comparisons technique. A method is presented for deriving probability distributions for the pairwise comparisons and for utilizing the distributions in the analysis of uncertainties in the evaluation process. The first step is that the expert or the decision-maker is queried as to the best guess of the priority ratio of the attributes compared. This is followed by an adjusting query concerning the uncertainty in the comparison: what is the probability of the priority ratio being between the best guess ± 1 unit of the pairwise comparison scale? An application of the method is presented in the form of multiple-criteria evaluation of alternative management plans for a forest area.
article id 676, category Research article
Afforestation of low-productive peatlands in Sweden – a tree species comparison. Silva Fennica vol. 32 no. 4 article id 676. https://doi.org/10.14214/sf.676
In 1970, five low-productive treeless peatlands in Sweden, ranging from latitudes 56°N to 67°N, were drained and fertilized for afforestation. The aim of the study was to determine the effect of four ditch spacings, varying from 7.5 to 60 m, and five NPK-fertilizer combinations, on the survival and growth of planted Scots pine (Pinus sylvestris), lodgepole pine (Pinus contorta), Norway spruce (Picea abies), and silver birch (Betula pendula) seedlings. The assessments were carried out 18–22 years after planting. Neither silver birch, nor Norway spruce was regarded suitable for the site type. The mortality of silver birch was almost complete, and Norway spruce did not grow well in any of the study areas, however, better than Scots pine in the north. Lodgepole pine had better height and diameter growth but also higher mortality rates than Scots pine. In the two northernmost experimental areas no response to fertilization was found. In the other three areas, the response to fertilization did not differ between species. Phosphorus was the most effective of the added fertilizer elements, whereas nitrogen showed no positive effect. Broadcast fertilizer application, with three times higher amount of fertilizer per ha gave the same growth response as spot application.
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.
article id 674, category Research article
Carbon dioxide exchange of Scots pine shoots as estimated by a biochemical model and cuvette field measurements. Silva Fennica vol. 32 no. 4 article id 674. https://doi.org/10.14214/sf.674
A biochemical model was used to calculate CO2 fluxes to Scots pine shoots in two boreal measurement stations, Hyytiälä in southern Finland (61°51’N, 24°17’E) and Värriö in northern Finland (67°46’N, 29°35’E). The results of the model were compared with cuvette measurements performed in field conditions. A differential equation for change in gas concentration inside a closed cuvette was constructed and solved in order to obtain conductances and fluxes. The results were generally in a good agreement, the correlation coefficients varied from 0.74 to 0.95. Some discrepancies were also found. The model followed more intensively changes in temperature. This could be seen in northern Finland measurements at low temperatures (< 18 °C). The modelled temperature response indicated low fluxes at low temperatures, but measurements did not show any decrease. The irradiation response was relatively similar in both measuring sites and according to the model. Cuvette measurements showed slightly smaller quantum yields as a result from shading of the needles. The temperature dependences of the biochemical model parameters Jmax and Vc(max) were re-evaluated from the field measurements. The results for Vc(max) agreed well with earlier estimations, while the results for Jmax indicated relatively high values at low temperatures especially in northern Finland. Exponential fitting produced also substomatal concentrations of CO2, which agreed quite well with the model. The daily minimum of substomatal/ambient concentration ratio varied from 0.4 to 0.8.
article id 673, category Research article
Utilizing a multipoint measuring system of photosynthetically active radiation in photosynthetic studies within canopies. Silva Fennica vol. 32 no. 4 article id 673. https://doi.org/10.14214/sf.673
A novel multipoint measuring system of photosynthetically active radiation (PAR) has been constructed and operated within a Scots pine canopy. A regular grid of 800 measuring points has been incorporated into a cuvette to observe the spatial and temporal distribution of PAR incident on the needles of a twig along with simultaneous measurements of the CO2 exchange in order to determine the dependence of photosynthesis on PAR. It was shown that large errors can result if the photosynthetic rate is estimated using the mean value of PAR instead of the instantaneous values of PAR detected at given points in the region of the needles. The results demonstrate that the obtained regression between the CO2 exchange rate estimated using the multipoint PAR measuring system and the measured CO2 exchange rate is as good within a canopy as in unshaded conditions.
article id 672, category Research article
Spread of Stereum sanguinolentum vegetative compatibility groups within a stand and within stems of Picea abies. Silva Fennica vol. 32 no. 4 article id 672. https://doi.org/10.14214/sf.672
A total of 57 naturally established Stereum sanguinolentum isolates was obtained from artificially wounded Picea abies stems in a forest area of 2 ha in Lithuania. Somatic incompatibility tests revealed 27 vegetative compatibility groups (VCGs) that contained 1–10 isolates. There was no spatial clustering of S. sanguinolentum VCGs within the forest area. The extent of S. sanguinolentum decay was analysed in 48 P. abies stems, 9–26 cm in diameter at breast height. Within 7 years of wounding, the length of S. sanguinolentum decay column in stems was 107–415 cm (291.5 ± 77.3 cm on average), lateral spread of the fungus at the butt was 38–307 cm2 (142.3 ± 66.8 cm2) and decayed proportion of the stem cross-section at the wound site (the butt) was 3–84% (36.8 ± 19.7%). In average, S. sanguinolentum VCG that infected 10 trees exhibited more slow growth inside the stem than VCGs that infected only one tree, and vertical growth varied to a greater extent within this VCG than among different VCGs. Correlation between stem diameter and vertical spread of S. sanguinolentum was not significant (r = –0.103). Despite uniformity of debarked area on all stems 7 years ago (300 cm2), open wound sizes on individual trees at the time of study were between 97–355 cm2 (215.1 ± 59.2 cm2) indicating large differences in wound healing capacity.
article id 686, category Research article
Nursery factors influencing containerized Pinus pinaster seedlings’ initial growth. Silva Fennica vol. 32 no. 3 article id 686. https://doi.org/10.14214/sf.686
Maritime pine (Pinus pinaster) containerized seedlings were raised outdoors at different fertilizer regimes, sowing date or culture duration to assess nursery factors influencing first year growth in the field. Seedling biomass, and N, P and K content before outplanting were affected by these different factors but the one year field growth was more related to N concentration than with morphological traits. The results are discussed in view to improve the plant stock quality in nursery.
article id 685, category Research article
Nursery and field response of sissoo plants (Dalbergia sissoo) to Rhizobium inoculation. Silva Fennica vol. 32 no. 3 article id 685. https://doi.org/10.14214/sf.685
The present research work aims to demonstrate the rehabilitation of a degraded forest land by afforestation of sissoo plants (Dalbergia sissoo Roxb.) inoculated with nitrogen fixing bacteria sp. In this study, effects of the three different Rhizobium isolates from three localities such as i. Kotre-isolate, ii. Pokhara-isolate and iii. Syangaza-isolate were assessed both in nursery and in the field. It was noted that the growth and biomass increment of seedlings in nursery as well as in the field after rhizobial inoculation were significantly high compared to control one. Among these 3-isolates, Kotre-isolate was found to be superior to others. Soil improvement around the root of inoculated seedlings was remarkable high. Nitrogen content of the soil increased in the range of 20–40% compared to control (only 10–20%). Kotre-isolate, in general, caused more soil improvement than the other isolates. The nutrient content in the green foliage, particularly nitrogen, increased in the range of 30–50%, compared to control one. The considerable increase in nutrients content of soil as well as in the foliage indicates the improvement in the quality of site.
article id 684, category Research article
Root electrolyte leakage and root growth potential as indicators of spruce and larch establishment. Silva Fennica vol. 32 no. 3 article id 684. https://doi.org/10.14214/sf.684
The relationship between the condition of bare-rooted 2-year-old seedlings of Sitka spruce and larch at the time of planting and their survival and growth after 2 years was examined. Data were analysed for 2 experiments using seedlings lifted and stored at +1 °C throughout the winter for planting in April and also for 2 experiments using seedlings planted directly on different dates without cold storage. Electrolyte leakage from the fine roots of spruce was closely correlated to survival following direct planting at different times from September to April and fine root leakage was a more accurate indicator of spruce performance than root growth potential. However the pattern of larch survival of directly planted stock was more closely related to root growth potential than to root leakage. When seedlings were cold-stored, root electrolyte leakage and root growth potential were modified during storage and following cold storage, the performance of both species was more closely related to root electrolyte leakage than root growth potential. These results are interpreted as meaning that successful establishment of bare-rooted seedlings requires a functional nursery root system that is capable of both supplying adequate water for a limited period immediately after transplanting and of producing roots to meet the seedling’s increased water demand later in the growing season.
article id 683, category Research article
An analysis of successful natural regeneration of downy and silver birch on abandoned farmland in Sweden. Silva Fennica vol. 32 no. 3 article id 683. https://doi.org/10.14214/sf.683
To improve our understanding of factors influencing the success of natural regeneration with downy birch (Betula pubescens Ehrh.) and silver birch (Betula pendula Roth) on abandoned farmlands, a survey was conducted to analyse the effects of site conditions and site preparation characteristics. The study was based on a sample plot inventory conducted in one northern and one southern district of Sweden, in which 29 successfully established, naturally regenerated stands, about to be cleaned or thinned, were assessed. Radical site preparation increased stand density and uniformity of established regeneration, and gave faster initial development, than establishment without site preparation on former leys or meadows. Large proportions of the total sample area were classified as moist, and soils consisting of sand–fine sand or peat were frequent. The frequency of birch stems was highest in mesic sites, and on soils consisting of sand, sand–fine sand or peat. Distances to seed-trees were generally shorter than 80 m, and downy birch was the dominant species in most stands.
article id 682, category Research article
The use of digitized aerial photographs and local operation for classification of stand development classes. Silva Fennica vol. 32 no. 3 article id 682. https://doi.org/10.14214/sf.682
The increasing capacity of modern computers has created the opportunity to routinely process the very large data sets derived by digitizing aerial photographs. The very fine resolution of such data sets makes them better suited than satellite imagery for some applications; however, there may be problems in implementation resulting from variation in radial distortion and illumination across an aerial photograph. We investigated the feasibility of using local operators (e.g., non-overlapping moving window means and standard deviations) as auxiliary data for generating stand development classes via three steps: (i) derive 6 local operators intended to represent texture for a 16 by 16 m window corresponding to a forest inventory sampling unit, (ii) apply a calibration process (e.g., accounting for location relative to a photo's principal point and solar position) to these local operators, and (iii) apply the calibrated local operators to classify the forest for stand development. Results indicate that calibrated local operators significantly improve the classification compared to what is possible using uncalibrated local operators and satellite images.
article id 681, category Research article
Open-top chamber fumigation system for exposure of field grown Pinus sylvestris to elevated carbon dioxide and ozone concentration. Silva Fennica vol. 32 no. 3 article id 681. https://doi.org/10.14214/sf.681
An open-top chamber fumigation system was built in a young Scots pine stand to study the effects of realistic elevated ozone (O3) and carbon dioxide (CO2) concentrations and their combination on trees in natural conditions. Doubled CO2 concentration compared to present ambient concentration, and O3 concentration between 40 ppb and 70 ppb in the first study year (1994) and doubled O3 concentration in years 1995 and 1996 were the target concentrations in the chambers. The O3 concentration in the chambers was successfully maintained close to the target concentration and differences between chambers were small. The mean CO2 concentration in the CO2 treatment was ca. 100 ppm below the target, but was maintained at this level throughout the growing season. Two degrees higher mean air temperature and slightly lower light intensity compared to open air were measured in the chambers. The operation of the fumigation system was satisfactory during the three study years and repeatability of the gas treatments can be regarded good in this low cost exposure system.
article id 692, category Research article
Use of satellite and field information in a forest damage survey of eastern Finnish Lapland in 1993. Silva Fennica vol. 32 no. 2 article id 692. https://doi.org/10.14214/sf.692
The study area consists of the Finnish part of a Landsat 5 TM image from 1990. Three independent field samples were measured during 1991–93 in the study area. The first sample was used to compile training areas for supervised maximum likelihood classification of the image. Classification accuracy was studied in the second sample. The spectral separability of the forest strata usable in practical forestry was poor. The extent of the damage area was estimated by the principle of stratified sampling. The estimate included considerable bias because the field sample had not been objectively selected from the image classes. The third field sample was measured as part of the National Forest Inventory of Finland. It is wholly objective, and about ten times larger than the two earlier field samples. The poor spectral separability of the forest strata was confirmed by the NFI sample. However, this sample could be used in stratified sampling with little or no bias in the estimation of the damage area estimate. 14 different damage types were separated according to specific damaging agent. A thematic map was produced which presents the spatial distribution of two damage-rich image classes. The study area comprises 18 300 sq.km, of which 38% were damaged. At first sight it would appear that the proportion of damaged forest has tripled in ten years. However, this is not the case because now special attention was paid to forest health in the field work. Despite this, it is possible that some damage caused by unfavourable climatic phenomena in the ’80s was still perceptible in 1993. No damage caused directly by air pollution has yet been verified in the study area.
article id 691, category Research article
Adaptation to changing environment in Scots pine populations across a latitudinal gradient. Silva Fennica vol. 32 no. 2 article id 691. https://doi.org/10.14214/sf.691
In several growth chamber and field experiments we examined the growth response of Scots pine (Pinus sylvestris L.) populations from a wide latitudinal range to temperature and photoperiod. The duration of the shoot elongation period of one-year-old seedlings was affected by temperature and photoperiod. In contrasting temperatures, 23/20 °C, 20/17 °C, and 17/14 °C (day/night), shoot elongation period for all populations was shortest in the high and longest in the low temperature treatments. The northern populations from 61–57°N ceased height growth earlier than the other populations in the southern 50°N photoperiod. The order of growth cessation among populations at 50°N in the chamber experiment and at 52°N in the field experiment was similar and related to observed population differences in terminal leader growth and total tree height. Since the length of growing season is under strong environmentally-mediated genetic control in Scots pine, potential climatic changes such as increasing temperature will probably alter the length and timing of growth in aboveground tree parts, but likely in the opposite direction (a shorter growing season) than has been often hypothesized (a longer growing season). Tree-ring analyses of a provenance experiment established in 1912 indicate that the main climatic factors that limited ring-width growth in Scots pine were air temperatures in the winter months of December through March. Low winter temperatures were followed by the formation of narrow rings over the next summer. Based on responses to temperature, Scots pine populations from the continuous European range can be divided in several geographic groups along a latitudinal gradient. Our results suggest that in developing new models to predict the response of Scots pine to changing environmental conditions, it is necessary to include intraspecific differentiation in acclimation and adaptation to environmental factors.
article id 690, category Research article
Will climate change affect the optimal choice of Pinus sylvestris provenances? Silva Fennica vol. 32 no. 2 article id 690. https://doi.org/10.14214/sf.690
Provenance experiments with Pinus sylvestris (L.) were evaluated in Sweden north of latitude 60°N. Survival and yield were determined as functions of temperature sum of the site and latitudinal origin of the provenance. Altitudinal origin was of negligible importance. The effects of latitudinal transfer were influenced by temperature sum at the growing site. At the harshest situated sites southward transfer longer than 3° was optimal for survival and yield, whereas transfer effects in a mild climate were weak. Climatic warming would reduce demands of hardiness. However, moderate differences in productivity are expected between formerly optimal seed sources and the ones adapted to changed climatic conditions. Since mortality usually was low in plantations older than 20 years or higher than 2 m, established stands are expected to be robust against adverse effects of climate change.
article id 689, category Research article
Phenotypic selection compared to restricted combined index selection for many generations. Silva Fennica vol. 32 no. 2 article id 689. https://doi.org/10.14214/sf.689
A breeding population has been subjected to repeated selection and crossing by simulation. Unrestricted phenotypic selection and restricted combined index selection were compared at the same effective number for five generations. Results show that phenotypic selection often achieves the gain and diversity possible to achieve by combined index selection but the relative efficiency is different for different family sizes and heritabilities. When phenotypic selection was compared with restricted combined index method at low heritabilities, both methods performed almost equally in terms of gain at the same effective number in small family sizes, although in large families, phenotypic selection was less efficient. At high heritabilities phenotypic selection was as efficient as combined index selection. Phenotypic selection was more efficient in conserving additive variance than combined index selection over five generations compared at the same gain and effective number. The introduction of a dominance component to the total variance had little effect. An increased breeding population size by a factor of ten resulted in an increased additive gain by app. 15%. The conclusion is that even though combined index selection is superior in identifying and extracting the potential for breeding achievements, it is generally not performing better than mass selection when compared at the same effective population size in small families.
article id 701, category Research article
The analysis of return and its components of non-industrial private forest ownership by forestry board districts in Finland. Silva Fennica vol. 32 no. 1 article id 701. https://doi.org/10.14214/sf.701
Non-industrial private forest ownership returns and risks in Finland are both estimated and disaggregated to local Forestry Board Districts (FBD) level. Additionally, the FBD level return is divided into price change, felling and change in the growing stock components, which are compared with the inflation rate. The results are based on a complete count of the stumpage prices, silvicultural costs and state subsidies as well as the National Forest Inventory (NFI) data. The influence of taxation is discussed as well. Although this database is excellent for economic studies as well, the estimation methodology is vitiated by a host of problems, the resolution of which is the major contribution of this study. The study period is 1972–1996. The results show that there have been fairly large differences in forest ownership returns and prices depending on the Forestry Board District. Results show that the price change component has been larger in Northern Forestry Board Districts, as much as 0.9% above the inflation rate in Lapland FBD, than in Southern Forestry Board Districts, 1.5% less than the inflation rate in southern Helsinki FBD. The net increase, however, has been larger in Southern Forestry Board Districts than in Northern Forestry Board Districts. Using the average net increment in Finland as a comparison base, the net increment in South Karelia exceeded it by 0.6%, but fell below it by 1.8% in Northeastern Finland. Finally, the return over the whole period is compared to the return on private housing and inflation in the case of North Savo. In all, the estimation methodology developed also serves as spin-off product development for the Forest Statistics Information Service (FSIS).
article id 700, category Research article
Exchange rate changes and the Finnish sawnwood demand and price in the UK market. Silva Fennica vol. 32 no. 1 article id 700. https://doi.org/10.14214/sf.700
This paper examines the long-run influence of exchange rate changes on the Finnish sawnwood price in the United Kingdom (UK) using quarterly data for the period 1978–1994. The degree of influence was measured by a pass-through coefficient (PT) obtained from a markup pricing relation of a system model. The model, which included export demand and price equations, was estimated with the cointegration method of Johansen. The results indicated a large PT, which means that exchange rate changes are reflected almost proportionately in Finnish export price expressed in pounds sterling. Thus, the Finnish price of sawnwood in pounds has lowered as a result of depreciation of the Finnish markka (FIM). This has improved Finnish competitiveness and market share in the UK. Appreciation of the FIM has had the opposite effect. It seems that Finnish exporters have made use of depreciations and devaluations of the FIM to maintain and increase their market shares but not necessarily their markups. For Finland, which is in the process of joining the European economic and monetary union (EMU), knowing the size of the PT is also important in assessing the economic impact of membership.
article id 699, category Research article
Values and objectives of non-industrial private forest owners in Finland. Silva Fennica vol. 32 no. 1 article id 699. https://doi.org/10.14214/sf.699
The purpose of the study was to create an empirical typology of non-industrial private forest owners based on forest values and long-term objectives of forest ownership, to identify these types by owner and holding characteristics, as well as to analyze silvicultural and harvesting behavior in these groups. The analysis was based on survey data on 245 forest owners in southeastern Finland. The results indicated that general forest values and long-term objectives of forest ownership are not strongly correlated. The results further suggested that the sole emphasis on economic benefits of forests does not lead to the most active silvicultural and harvesting behavior. Multiobjective owners, who underlined both monetary and amenity benefits of their forest property, were the most active in their silvicultural and cutting behavior. Non-timber objectives seemed not to exclude wood production: a group called recreationists harvested slightly less than other owners. Recreationists were willing to invest in forestry but were selective with respect to management practices. The results can be used in planning and implementation of public forest policy such as allocation of the resources of forestry extension services. Forest industries should also benefit from a knowledge of the objectives of roundwood sellers.
article id 698, category Research article
Satisfaction and company loyalty as expressed by non-industrial private forest owners towards timber procurement organizations in Finland. Silva Fennica vol. 32 no. 1 article id 698. https://doi.org/10.14214/sf.698
The satisfaction and company loyalty as expressed by non-industrial, private forest (NIPF) owners towards timber procurement organizations were clarified via a mail questionnaire. The results denoted that there is a positive correlation between the levels of forest owners’ expectations (EXP) and perceived performance (PERF). In addition, the lower EXP and the higher PERF were, the greater was the overall satisfaction index (SAT). About two thirds of forest owners were characterized by a negative SAT value or then they were dissatisfied with the performance of the procurement organization in their last timber-sales transaction. Furthermore, the results obtained indicated that the SAT index significantly influences the company loyalty expressed by NIPF owners – their willingness to give favourable reports of the company to the others, and their willingness to engage in future timber-sales transactions with the same company. Nonetheless, the SAT index did not affect the market share of a particular company, and this could be partly accounted for by the similar level of performance among the companies and the lack of competition in the timber trade. Finally, the results revealed several dimensions of timber procurement, and some seller segments to which companies could pay more attention to in order to be able to achieve better satisfaction levels and the loyalty of NIPF owners in the future. One approach to successfully addressing these challenges could be the adopting of a satisfaction decision support system (SatDSS).
article id 697, category Research article
Integrating variation in tree growth into forest planning. Silva Fennica vol. 32 no. 1 article id 697. https://doi.org/10.14214/sf.697
Forest planning is always influenced by uncertain factors. Variations in growth, outcome of regeneration, timber prices, costs and mortality cannot be avoided, whereas the quality of inventory data and the models used for estimation of the state and development of forests can be improved. Methods have been developed for incorporating risk and attitude toward risk in decision analysis, but there has been a lack of good models for dealing with the various sources of risk. The aim of this study was to estimate stochastic models for the variation in growth of Scots pine (Pinus sylvestris), Norway spruce (Picea abies) and birch (Betula pendula and Betula pubescens). The said models had to be capable of generating growth scenarios, and thus correlations between series had to be taken into account. ARMA models were estimated for mean growth index series from Pohjois-Karjala, eastern Finland. Several ARMA models, some of which had seasonal parameters, were found to be adequate for each series. Non-seasonal AR(1) and seasonal AR(1,1) models were used to produce growth scenarios in the case study, in which variation in growth was integrated into forest planning.
article id 696, category Research article
Redistribution of 14C-labelled reserve carbon in Pinus sylvestris seedlings during shoot elongation. Silva Fennica vol. 32 no. 1 article id 696. https://doi.org/10.14214/sf.696
This study examined the later use of 14C reserves formed in previous autumn in Scots pine (Pinus sylvestris L.) seedlings. The seedlings were allowed to photosynthesise 14CO2 in early September when shoot and needle growth was over. The following spring the seedlings were harvested in five samplings during the shoot growth period. The distribution and concentration of 14C were determined and the results were compared with the growth data. It was observed that reserves were not used markedly for the new growth. Most of the 14C was found in one-year-old needles (30–40%) and in the root system (40–50%) which was due to both their high activity as a storage sink and their large sink size. The high initial 14C-activity in the finest roots decreased indicating respiration of reserves. Only a small percent of the reserve carbon was found in the new shoots which indicated that reserves are of minor importance in building a new shoot. An allocation of about 15% of the autumn storage to the stem suggested that in seedlings the stem is of minor importance as a storage organ.
Category: Review article
article id 688, category Review article
Afforestation of marginal agricultural land in the Lower Mississippi River Alluvial Valley, U.S.A. Silva Fennica vol. 32 no. 3 article id 688. https://doi.org/10.14214/sf.688
Afforestation of marginal agricultural land in the Lower Mississippi Alluvial Valley (LMAV) relies on native species, planted mostly in single-species plantations. Hard mast species such as oak and pecan are favored for their value to wildlife, especially on public land. Successful afforestation requires an understanding of site variation within floodplains and matching species preferences and tolerances to site characteristics, in particular to inundation regimes. Soil physical conditions, root aeration, nutrient availability, and moisture availability during the growing season also must be considered in matching species to site. Afforestation methods include planting seedlings or cuttings, and direct-seeding. Both methods can be done by hand or by machine. If good quality seedlings are planted properly and well cared for before planting, the chances for successful establishment are high but complete failures do occur. Mortality and poor growth are caused by many factors: extended post-planting drought or flooding; poor planting or seeding practices; poor quality seed or seedlings; animal depredation; or herbicide drift from aerial application to nearby cropland. More species can be planted, even on continuously flooded sites. Direct-seeding, while limited to heavy-seeded species (oaks and hickories), costs less than 50% of planting seedlings. Growth varies considerably by soil type; most bottomland hardwoods grow best on silt loam and less well on clay soils. Up to 200 000 ha of land in the LMAV subject to spring and early summer backwater flooding could be afforested over the next decade.
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.
article id 695, category Review article
Factors influencing occurrence and impacts of fires in northern European forests. Silva Fennica vol. 32 no. 2 article id 695. https://doi.org/10.14214/sf.695
The return interval and number of fires vary, depending on the geographical location in interaction with climate, topography and amount of fuel. During recent decades, in northern Europe the number and severity of fires have been insignificant compared with Mediterranean region, in which fire return intervals may be 15–35 years, compared to the average of 60–120 years for boreal forests. This is partly due to the efficient system of fire protection in northern Europe, but is mainly due to the less favourable climate for fire and the smaller human impact on ignition of forest fires. The consequences of fire are related to both site and stand characteristics, site being the most important factor controlling the stability of stands. Dry sites being more flammable and likely to ignite are associated with high risk of fire. In northern Europe, due to the interaction between species and site, the role of species difference in risk of fire damage is not clear. In southern Europe, fire risk cannot be explained by differences between tree species. There, other vegetation (shrubs, etc.) is of major importance for the risk of fire. Management of forests can, to some degree, alter the risk and the occurrence of fire. In northern Europe, logging may have compensated for fire occurrence by decreasing the amount of fuel. In addition, forest roads act as fire-breaks and facilitate fire-fighting. On the contrary, in southern Europe the risk of fire has been found to increase because the traditional forest uses and management have decreased, which increases the accumulation of fuel. However, it is not yet possible to quantify and compare the effect of management in absolute terms. Currently, some tools, such as fire-risk indices, remote sensing and GIS-based techniques, are available for prediction of fire risk in some areas. For example, fire-risk indices are most suitable for areas, like northern Europe, which have a low fire risk. In high-risk areas, such as southern Europe, more sophisticated techniques are needed for assessment of the risk. In the future, assuming global warming at northern latitudes (2 x CO2 climate), the risk of fire damage could also increase in northern Europe. Therefore, to allow the various locational and silvicultural factors to be assessed on the European level, an integrated risk model is needed.
article id 694, category Review article
Evolutionary forces influencing variation among populations of Pinus sylvestris. Silva Fennica vol. 32 no. 2 article id 694. https://doi.org/10.14214/sf.694
The evolutionary forces influencing genetic differentiation among populations are identified. Natural selection, random genetic drift, and mutations promote differentiation while phenotypic plasticity and gene flow delay or prevent differentiation. Evolution is a dynamic force which leads to instability and absence of any perfection in the adaptive process. Natural selection acts mainly on phenotypes and only indirectly on the components of important breeding traits. In the northern part of the distribution of Scots pine there is a large among- and within-population variation in survival. The high among-population variation occurs in spite of an assumed high gene flow. Biomass is a product of many components and it also shows a high population variation. Many markers are neutral and such markers will not reveal adaptive variation.
article id 693, category Review article
Changes in wood and stem properties of Pinus sylvestris caused by provenance transfer. Silva Fennica vol. 32 no. 2 article id 693. https://doi.org/10.14214/sf.693
Wood properties focused in forest tree breeding should be of economic importance, have a large total variation and a high heritability. The properties of interest are those that influence the strength and durability of sawn products or the amount and properties of pulp produced. The following wood properties are treated: width of the annual ring, juvenile wood, late wood content, heart wood, tracheid dimensions, basic density, stem straightness and branch diameter. The provenance variation in wood properties can be related to differences in growth phenology. In the northern part of distribution P. sylvestris (L.) provenances transferred a few degrees southwards have a high survival and yield but stem wood production is low. Trees from these provenances will be straight and with few spike knots or other injuries. The shoot elongation period will be short and the temperature sum required for wood formation sufficient. Provenances transferred southwards will form thin annual rings, few and thin branches, little early wood, high basic density and slender tracheids with thick cell walls in comparison to local provenances. An example of the effect of alternative transfers on the yield and wood properties is evaluated. In regions with deviating climatic patterns alternative provenance transfer patterns may be better. The objectives of the land owner should influence the provenance choice. The importance of integrating tree improvement with silvicultural management is discussed with reference to spacing.
Category: Research note
article id 679, category Research note
Respiration in a forest soil 27 years after fertilization with different doses of urea. Silva Fennica vol. 32 no. 4 article id 679. https://doi.org/10.14214/sf.679
A number of previous studies have shown that N fertilization often reduces respiration in forest soils. However, the durability of this effect has not been fully explored. In this study, the response of soil respiration to a single fertilization with urea, applied 27 years earlier, was examined in a field experiment located in a stand of Pinus sylvestris in central Sweden. The doses that had been added were 120, 240 and 600 kg N ha–1. Samples were taken from the humus layer and the upper 7.5 cm of the mineral soil. Sieved samples were incubated in the laboratory. No effect of the previous fertilization on soil respiration was found, thus indicating that the reduction shown in earlier studies is not persistent. There was a tendency that the highest N dose had caused a higher N concentration and a lower C/N-ratio in the humus layer and a higher C concentration in the mineral soil.
article id 678, category Research note
A new forest floor corer for rapid sampling, minimal disturbance and adequate precision. Silva Fennica vol. 32 no. 4 article id 678. https://doi.org/10.14214/sf.678
We describe an effective and inexpensive device for sampling forest floors. It is based on a rechargeable, battery-powered drill that drives a sharpened steel coring tube. The corer is simple to fabricate, is lightweight (3.5 kg) and can be used easily by one person to obtain intact, natural volume cores of the forest floor. It has been used extensively to obtain samples in 114 boreal forest stands of western Canada. We found that coefficients of variation were typically 30% for forest floor organic matter and bulk density, and tended to be higher in Pinus banksiana stands than in Picea glauca and Populus tremuloides. Ten samples per stand gave adequate precision for a study of forest floor dynamics and autocorrelation did not appear to be a problem with five-metre sampling intervals. In addition to sampling forest floors, the corer has proven suitable for sampling moss and lichen layers and mineral soil down to about 20 cm. A similar powered system can also be used for increment boring of trees.
article id 702, category Research note
Short-needle disease of Scots pine: an abnormal needle length distribution. Silva Fennica vol. 32 no. 1 article id 702. https://doi.org/10.14214/sf.702
Short-needle syndrome occurs commonly in southern Finland. The disease is characterized by abnormal length distribution of the needles in shoots. In most cases, affected shoots have needles of normal length as well as very short needles. The short needles are those injured during the needle elongation period; the tissues formed abnormal sclerenchymatic structures and wound periderm. One possible cause could be hemipterous insects feeding on growing needles. Salivary sheaths of such insects were often present in both deformed needle bases and undeformed mature tissues.
Category: Discussion article
article id 680, category Discussion article
ESC-strategy for rational operationalization of forest biodiversity maintenance in Finland. Silva Fennica vol. 32 no. 4 article id 680. https://doi.org/10.14214/sf.680