Category: Research article
article id 303, category Research article
Industrial timberland ownership in the USA: arguments based on case studies. Silva Fennica vol. 41 no. 2 article id 303. https://doi.org/10.14214/sf.303
The forest product companies’ ownership of timberland is decreasing in the United States as in many other countries. In aggregate the forest product industry owned 26.5 million hectares (11.6% of the U.S. timberland) in 2002 compared with 28.5 million hectares in 1987 (FIA 2006). Reasons for this decrease of timberland ownership are several and complex. This article presents four case studies of U.S.-based forest product companies. The vertical integration theory and empirical studies about timberland ownership give a base for the study. Four hypotheses are formulated on the basis of the literature. The results give support to two of them. An important reason for timberland ownership is a wish to secure deliveries. Market conditions are important for the need of owning timberland. Two of the companies did not own timberland, the main reason being more profitable alternative uses of capital. The ownership structure of the company, tradition, and culture are other important explanations for timberland ownership. This study did not show the advantage of timberland ownership for information and coordination.
article id 302, category Research article
Effects of some sanding factors on the surface roughness of particleboard. Silva Fennica vol. 41 no. 2 article id 302. https://doi.org/10.14214/sf.302
Effects of the grit sizes of the sand belt, feeding speed and the feed power of the heads of the sander on the surface roughness of the particleboard panels were investigated. Two surface roughness parameters, average roughness (Ra) and mean peak-to-valley height (Rz), obtained from board surfaces were used in the analysis. Sanding factors were found to have a significant effect on the surface roughness of the particleboard. Better results were obtained with 40 m/min of feeding speed, 40-60-80-120 of grit sizes, and 67 kW of the feed power of the heads of the sander.
article id 301, category Research article
FTIR spectroscopic prediction of Klason and acid soluble lignin variation in Norway spruce cutting clones. Silva Fennica vol. 41 no. 2 article id 301. https://doi.org/10.14214/sf.301
Our purpose was to develop a FTIR spectroscopic method to be used to determine the lignin content in a large number of samples and to apply this method studying variation in sapwood and heartwood lignin content between three fast-growing cutting clones grown in three sites. Models were estimated with 18 samples and tested with 6 samples for which the Klason lignin + acid soluble lignin content had been determined. Altogether 272 candidate models were built with all-subset regressions from the principal components estimated from differently treated transmission spectra of the samples; the spectra were recorded on KBr pellets of sieved and unsieved unextracted wood powder and subjected to four different preprocessings and two different wavenumber selection schemes. The final model showed an adequate fit in the estimation data (R2 = 0.74) as well as a good prediction performance in the test data (R2P = 0.90). This model was based on the wavenumber range of 1850–500 cm–1 of the line-subtraction-normalised spectra recorded from sieved samples. The model was used to predict lignin content in 64 samples of the same material. One of the clones had a slightly lower sapwood lignin content than the two other clones. The fertile growing site with fast growing trees showed slightly higher sapwood lignin content compared with the other two sites. The model was also used to predict the lignin content in the earlywood of 45 individual annual rings. Variation between individual stems and between annual rings was found to be large. No correlation was found between the lignin content and density of earlywood.
article id 300, category Research article
Comparing regression estimation techniques when predicting diameter distributions of Scots pine on drained peatlands. Silva Fennica vol. 41 no. 2 article id 300. https://doi.org/10.14214/sf.300
We compared different statistical methods for fitting linear regression models to a longitudinal data of breast height diameter (dbh) distributions of Scots pine dominated stands on drained peatlands. The parameter prediction methods for two parameters of Johnson’s SB distribution, fitted to basal-area dbh distributions, were: 1) a linear model estimated by ordinary least squares (OLS), 2) a multivariate linear model estimated using the seemingly unrelated regression approach (SUR), 3) a linear mixed-effects model with random intercept (MIX), and 4) a multivariate mixed-effects model (MSUR). The aim was to clarify the effect of taking into account the hierarchy of the data, as well as simultaneous estimation of the correlated dependent variables on the model fit and predictions. Instead of the reliability of the predicted parameters, we focused on the reliability of the models in predicting stand conditions. Predicted distributions were validated in terms of bias, RMSE, and error deviation in the generated quantities of the growing stock. The study material consisted of 112 successively measured stands from 12 experimental areas covering the whole of Finland (total of 608 observations). Two independent test data sets were used for model validation. All the advanced regression techniques were superior to OLS, when exactly the same independent stand variables were included. SUR and MSUR were ranked the overall best and second best, respectively. Their ranking was the same in the modeling data, whereas MSUR was superior in the peatland test data and SUR in the mineral soil test data. The ranking of the models was logical, but may not be widely generalized. The SUR and MSUR models were considered to be relevant tools for practical forest management planning purposes over a variety of site types and stand structures.
article id 299, category Research article
Application of ant colony optimization for the risk management of wind damage in forest planning. Silva Fennica vol. 41 no. 2 article id 299. https://doi.org/10.14214/sf.299
Ant colony optimization (ACO) is still quite a new technique and seldom used in the field of forest planning compared to other heuristics such as simulated annealing and genetic algorithms. This work was aimed at evaluating the suitability of ACO for optimizing the clear-cut patterns of a forest landscape when aiming at simultaneously minimizing the risk of wind damage and maintaining sustainable and even flow of periodical harvests. For this purpose, the ACO was first revised and the algorithm was coded using the Visual Basic Application of the ArcGIS software. Thereafter, the performance of the modified ACO was demonstrated in a forest located in central Finland using a 30-year planning period. Its performance was compared to simulated annealing and a genetic algorithm. The revised ACO performed logically since the objective function value was improving and the algorithm was converging during the optimization process. The solutions maintained a quite even periodical harvesting timber while minimizing the risk of wind damage. Implementing the solution would result in smooth landscape in terms of stand height after the 30-year planning period. The algorithm is quite sensitive to the parameters controlling pheromone updating and schedule selecting. It is comparable in solution quality to simulated annealing and genetic algorithms.
article id 298, category Research article
Seedling establishment and growth after direct seeding with Pinus sylvestris: effects of seed type, seed origin, and seeding year. Silva Fennica vol. 41 no. 2 article id 298. https://doi.org/10.14214/sf.298
The early effects of seed type, seed origin, and seeding year on seedling emergence, survival, and growth after one to four years was quantified and examined. Two experimental series of Scots pine located at 61°N and 64°N and six orchard seed lots and six stand seed lots of adequate geographical origins in each series were used. Both series were replicated at five sites for up to five years. On average, orchard seed lots had 16% and 12% higher seedling emergence, in relation to sown germinable seeds, than stand seed lots in the northern and southern series. The survival from year 1 to year 4 was also higher for orchard seedlings than for stand seedlings; there was a 77% and 72% survival rate in the northern series and a 58% and 49% survival rate in the southern series for orchard and stand seedlings respectively. On average, after four years orchard seedlings were 26% taller in the northern series and 13% taller in the southern series. The gain in height growth for the orchard seeds was positive at all seeding years, at all sites, and at all seedling ages. If survival was calculated to the height of a four-year-old seedling, the survival of orchard seedlings increased by 3% in the northern and 1% in the southern series as the result of the higher growth of orchard seedlings. Using orchard seeds resulted in 6 percent units higher growth gain when the clear cuts were regenerated with direct seeding than with plants using the same seed material. Changes in the ranking of seed lots and seed types at different sites and seeding years for seedling emergence is an effect of external factors such as grazing and foraging that cannot be related directly to the tested factors.
article id 297, category Research article
Operational standards and guidelines for biodiversity management in tropical and subtropical forest plantations – How widely do they cover an ecological framework? Silva Fennica vol. 41 no. 2 article id 297. https://doi.org/10.14214/sf.297
The development of standards and guidelines to secure sustainable forest management at different geographical scales has expanded greatly during the past fifteen years. Most of these efforts, however, have been formulated for natural forests only; those designed specifically for forest plantations are relatively few. The global forest plantation area is expanding rapidly, with obvious positive and negative impacts on biodiversity. We characterize the key concepts of biodiversity in tropical and subtropical forest plantations and present an analysis of how these elements are covered in the eight principal operational standards and guidelines for sustainable plantation forestry. We also examine the applicability of standards and guidelines in plantations established and managed under different initial settings. The results indicate that the standards and guidelines address certain key elements of biodiversity comprehensively, meanwhile others are ignored or receive only slight attention. There is also substantial variation between the sets in their nature (performance- vs. process-based), scope, congruity in concepts and hierarchy, and specificity. The standards and guidelines seldom take into account the varying initial settings for plantation establishment and the consequent variation in critical factors in biodiversity conservation and management. We recommend that standards and guidelines should be developed so as to pay more attention to the type and operating environment of plantations, to cover all key factors of biodiversity, and to consider building closer relationships between the social and ecological aspects of biodiversity.
article id 296, category Research article
Influence of ground substrate on establishment of reindeer lichen after artificial dispersal. Silva Fennica vol. 41 no. 2 article id 296. https://doi.org/10.14214/sf.296
Methods to improve the recovery of reindeer lichen after soil disturbance or overgrazing are being sought for areas where reindeer are herded. The effects of four substrates – mineral soil, moss, twigs and pine bark – on the establishment of lichen fragments after total removal of the vegetation were thus studied in a middle-aged pine stand and a clear-cut, both located in a lichen-rich pine-heath. Cladina mitis fragments of two sizes were manually dispersed in 1 m2 quadrats and their movements from their respective dispersal points were registered after one year. The natural re-establishment of lichens in the quadrats was monitored over three years by using digital pictures. In the forest stand, no significant differences were detected in either the fragment movement or the lichen establishment between the different substrates, but the fragment size had positive effects on both parameters. In the clear-cut, the moss substrate was the most suitable not only for the artificially dispersed lichens to fasten to, but also for the natural settlement of lichens from the surrounding lichen mat. More lichen thalli fastened to the bark and twigs substrates than to the mineral soil, but the settlement of lichens from the surrounding was greater on bare mineral soil substrate. The results indicate that artificial dispersal of lichen thalli on an appropriate substrate could be a successful strategy for promoting lichen recovery.
article id 295, category Research article
Experimental evidence for associational resistance against the European pine sawfly in mixed tree stands. Silva Fennica vol. 41 no. 2 article id 295. https://doi.org/10.14214/sf.295
This study examined whether the saplings of Scots pine (Pinus sylvestris) exhibit associational resistance against the European pine sawfly Neodiprion sertifer (Hymenoptera, Diprionidae) when grown in a mixture with 50% silver birch (Betula pendula). The number of sawflies on pine trees in pure and mixed stands was manipulated at two experimental sites during two years. Survival of larvae and eggs was monitored, and the numbers of presumed sawfly predators were counted. A lower proportion of sawfly larvae and eggs survived on pines grown in the mixture with birch as compared with pure pine stands. Lower survival of sawfly larvae in the mixed stands was associated with the higher abundance of ants in these stands. The numbers of other sawfly predators (e.g. spiders and predatory heteropterans) differed between the study sites and were negatively associated with the presence of ants, which suggests possible interference between these groups. Although sawfly survival was lower on pines in the mixed stands, providing evidence of associational resistance, a related study shows the same trees had a higher number of ant-tended aphid colonies as compared with pines in the pure stands. Therefore, instead of considering resistance against individual herbivore species, it seems more practical to use associational resistance as a trait representing the resistance of larger systems, such as whole tree stands, against the total damage caused by herbivores in general.
article id 294, category Research article
Decomposition of fine roots and α-cellulose in a short rotation willow (Salix spp.) plantation on abandoned agricultural land. Silva Fennica vol. 41 no. 2 article id 294. https://doi.org/10.14214/sf.294
Decomposition of fine roots (<1 mm in diameter) of the clones of Salix viminalis, S. dasyclados and α-cellulose sheets (50 x 10 x 1 mm) was studied in a 6-years old Salix spp. plantation established on abandoned agricultural land in Estonia. The substrates were incubated in litterbags (mesh size 0.14 mm) in 5–10 cm topsoil, in non-fertilised plots for one year. Changes in the ash-free weight of the fine roots were best described by negative exponential models (S. viminalis R2 = 0.98, S. dasyclados R2 = 0.96), and by a linear model for α-cellulose (R2 = 0.63). The sheets of α-cellulose decomposed roughly twice as rapidly as the fine roots (S. viminalis k = 0.325, S. dasyclados k = 0.165). The remaining (of the initial) ash-free weights of the fine roots were 73.3 ± 0.8% (mean ± SE) and 85.8 ± 2.2% respectively, and of the α-cellulose 35.9 ± 8.5%, in the end of the one year of decomposition. The amount of acid detergent (AD) lignin in the fine-roots of S. viminalis increased significantly and did not change in S. dasyclados, suggesting higher activity of microbial decomposers in the first substrate. Of the studied quality parameters, the AD lignin was the major factor determining the different rate of decomposition of the fine roots of S. viminalis and S. dasyclados. Nitrogen was recycled in the fine root sub-system in both Salix species. This knowledge can be applied in the management of Salix plantations, aimed at bioenergy production.
article id 293, category Research article
Seed moisture content during chilling and heat stress effects after chilling on the germination of common alder and downy birch seeds. Silva Fennica vol. 41 no. 2 article id 293. https://doi.org/10.14214/sf.293
The effects of seed moisture content (MC) and heat treatment on the germination response of common alder (Alnus glutinosa) and downy birch (Betula pubescens) seeds were examined. Seeds of each species were adjusted to MC of 7% to 50% MC, then chilled for up to 36 weeks, after which they were allowed to germinate at 15°C with 8 hours lighting per day or 20 (dark)/ 30°C (light). Seed lot effects were evident, but treatment effects were consistent in each lot and species. The response to moist chilling treatments was larger at 15°C than at 20/30°C. Chilling had no effect on germination unless seed MC was >15%, but it was low also at 20% MC. The highest germination was achieved following 24–36 weeks chilling at the optimum or target MC (TMC) levels of about 30% in alder and 35% in birch. In a separate experiment, seeds were fully imbibed (FI) (~50% MC; standard method used in operational practice) or adjusted to TMC levels, after which some seeds of each treatment group were chilled to release dormancy. Following this, the seeds were dried back to TMC levels and then subjected to 60°C for up to 4 hours after which they were allowed germinate under the same conditions described above. Heat treatment damaged the prechilled FI seeds, but no damage occurred to the non-chilled seeds. However, heat stress stimulated germination in the non-chilled FI seeds of both species and the TMC seeds of alder.
article id 292, category Research article
Interactions between morphological and physiological drought responses in Eucalyptus microtheca. Silva Fennica vol. 41 no. 2 article id 292. https://doi.org/10.14214/sf.292
We studied the response of Eucalyptus microtheca to drought in a greenhouse experiment. As a result of the drought the growth of the seedlings decreased and allocation patterns changed so that allocation to the roots increased. However, changes in photosynthesis and stomatal conductance under drought were rather modest. We showed, using chlorophyll fluorescence and measurements of photosynthesis under high CO2 that the biochemical capacity of photosynthesis increased under drought. The results suggest that changes in root/shoot ratio are the primary reactions that initiate a series of compensatory reactions that mitigate the effects of drought in Eucalyptus microtheca.
article id 291, category Research article
The impact of over-exploitation on the genetic structure of Turkish red pine (Pinus brutia Ten.) populations determined by RAPD markers. Silva Fennica vol. 41 no. 2 article id 291. https://doi.org/10.14214/sf.291
To determine the possible impact of over-exploitation on the genetic structure of Turkish red pine (Pinus brutia Ten.) populations, three natural and three over-exploited (human degraded) populations of the species in the Mediterranean region of Turkey were investigated with Randomly Amplified Polymorphic DNA (RAPD). With the 80 RAPD primers tested, 12 of them yielded 137 polymorphic RAPD fragments. Four of the studied populations maintained unique fragments. The mean proportion of polymorphic fragments for all populations ranged from 89.8 to 98.9% and there were no significant differences between natural (94.8%) vs. over-exploited populations (92.7%). The estimated heterozygosity values suggested that Turkish red pine maintains high levels of genetic diversity (range 0.24–0.28) though studied populations and grouped ones as natural (He = 0.28) vs. over-exploited (0.27) did not differ significantly. The mean FST value indicated that the large portion of the total genetic diversity was within populations (93%), but this value was lower in the natural populations (92%) than in the over-exploited ones (94%). In over-exploited populations, excess of homozygosity was observed (about 6% higher) as compared to natural populations, indicating impacts of inbreeding in P. brutia.