Category: Research article
article id 1000, category Research article
On the possibility to monitor and assess forest damage within large scale monitoring programmes – a simulation study. Silva Fennica vol. 47 no. 3 article id 1000. https://doi.org/10.14214/sf.1000
There is a growing demand for information on forest health due to fears that climate change may cause new kinds of damage that have not previously been encountered. In many cases, forest damage monitoring is conducted exclusively within sparse large-scale grids of sample plots and it is doubtful whether these are capable of providing relevant information to support mitigation programmes or other actions required to reduce economic losses due to damage outbreaks. In this study, we used simulated sampling to assess the precision of estimators related to forest state and changes in the damage sustained by trees within an area corresponding to the Swedish region Götaland, assuming a sampling design corresponding to that used in the Swedish National Forest Inventory (NFI) under different damage scenarios. Large and uniformly distributed damage outbreaks were well captured by an NFI-type inventory, but scattered damage outbreaks produced estimates with poor precision. As a consequence, we propose that there might be a need to revise current forest damage monitoring programmes to make them more useful for monitoring the kinds of damage that are likely to arise as a consequence of climate change.
article id 899, category Research article
Monitoring the chipping and transportation of wood fuels with a fleet management system. Silva Fennica vol. 47 no. 1 article id 899. https://doi.org/10.14214/sf.899
Controlling and organizing the complex forest-to-consumer supply chain of wood fuels is a challenging task, especially for the chipping and transport processes. Truck mounted chippers and transport trailer-trucks must be scheduled to minimize delay to be profitable. Job management within the supply chain, including machine activity based controlling, offers a new way to increase efficiency and productivity. However, detailed data are required to detect and analyze potential gaps and improve forest fuel supply. Generally, data regarding the wood fuel supply chain process are obtained from extensive time studies that are based on a specific process step. Although time studies can detect details during the production of forest fuels, they only describe certain time frames. Long-term data that are recorded during the entire year could encompass seasonal and short term effects. This study aims to monitor the forest fuel supply processes (semi-automated), specifically regarding time and fuel consumption. Large data sets were automatically and efficiently gathered with little effort by drivers and operators. Data were recorded with fleet management equipment for more than 14 months. Vehicle data, including GPS data, were logged at an interval of one minute. Data management was conducted in a pre-configured database that contained pre-defined reports and were run by the Institute of Forest Engineering, Vienna. Work step assignments were implemented with Structured Query Language (SQL)-routines by using the raw machine activities data and GPS. The chipping and transport activities of more than 240 loads were analyzed by focusing on fuel consumption, time needed and traffic. The average distance between chipping sites and plants was approximately 54 kilometers. Fuel consumption from transport reached 50 l/100 km. The chipping unit reached a productivity of 12.8 odt/PSH15 and had a fuel consumption of 58 liters per operating hour.
article id 185, category Research article
Imputing mean annual change to estimate current forest attributes. Silva Fennica vol. 43 no. 4 article id 185. https://doi.org/10.14214/sf.185
When a temporal trend in forest conditions is present, standard estimates from paneled forest inventories can be biased. Thus methods that use more recent remote sensing data to improve estimates are desired. Paneled inventory data from national forests in Oregon and Washington, U.S.A., were used to explore three nearest neighbor imputation methods to estimate mean annual change of four forest attributes (basal area/ha, stems/ha, volume/ha, biomass/ha). The randomForest imputation method outperformed the other imputation approaches in terms of root mean square error. The imputed mean annual change was used to project all panels to a common point in time by multiplying the mean annual change with the length of the growth period between measurements and adding the change estimate to the previously observed measurements of the four forest attributes. The resulting estimates of the mean of the forest attributes at the current point in time outperformed the estimates obtained from the national standard estimator.
article id 355, category Research article
Geometrically accurate time series of archived aerial images and airborne lidar data in a forest environment. Silva Fennica vol. 40 no. 1 article id 355. https://doi.org/10.14214/sf.355
Reconstructing three-dimensional structural changes in the forest over time is possible using archived aerial photographs and photogrammetric techniques, which have recently been introduced to a larger audience with the advent of digital photogrammetry. This paper explores the feasibility of constructing an accurate time-series of archived aerial photographs spanning 42 years using different types of geometric data and estimation methods for image orientation. A recent airborne laser scanning (lidar) data set was combined with the image block and assessed for geometric match. The results suggest that it is possible to establish the multitemporal geometry of an image block to an accuracy that is better than 0.5 m in 3D and constant over time. Even geodetic ground control points can be omitted from the estimation if the most recent images have accurate direct sensor orientation, which is becoming a standard technique in aerial photography. This greatly reduces the costs and facilitates the work. An accurate multitemporal image block combined with recent lidar scanning for the estimation of topography allows accurate monitoring and retrospective analysis of forest vegetation and management operations.
article id 568, category Research article
Anthropogenic effects on understorey vegetation in Myrtillus type urban forests in southern Finland. Silva Fennica vol. 36 no. 1 article id 568. https://doi.org/10.14214/sf.568
The growth of urban population in Finland has resulted in increased fragmentation of urban forests and consequently increased recreational pressure on these forests. The effects of fragmentation and trampling on the ground and field layer vegetation were studied in mesic Myrtillus type Norway spruce-dominated urban forest stands of varying size in the greater Helsinki area. The number of residents living in the vicinity of the forest stands was an important factor affecting the understorey vegetation in urban forests. The cover of understorey vegetation in urban forests was remarkably lower than in rural areas, especially the ground layer cover, e.g. cover of Pleurozium schreberi, was significantly lower in urban forests than in the reference areas. Thus, the ground layer proved to be most susceptible to trampling. In the field layer, the cover of dwarf shrubs, especially of Vaccinium myrtillus, was lower in deteriorated than in undeteriorated urban forest stands.
Category: Review article
article id 550, category Review article
The role of moose as a disturbance factor in managed boreal forests. Silva Fennica vol. 36 no. 1 article id 550. https://doi.org/10.14214/sf.550
We review the interactions between moose (Alces alces) and native tree species in Fennoscandia. The Fennoscandian boreal forests have been intensively managed for wood production over decades. Moose population density is also relatively high in these northern forests. Forest management affects habitat characteristics and food resources from regeneration to final harvest, with the most significant effects occurring early in the stand development. The plant-animal interactions found in such a situation may be different from what has been observed in natural boreal forests with low densities of moose (e.g. in North America). The strong focus on Scots pine (Pinus sylvestris) in forest regeneration in conjunction with a homogenisation of the landscape structure by clear-cutting has favoured moose. Forest development is controlled by man from regeneration to final harvest, and in relation to human-induced disturbances the disturbance by moose is relatively small, but occurs on different spatial levels. At the landscape level, the most prominent effects of moose seem to be suppression and/or redistribution of preferred browse species. At the forest stand level moose primarily induce spatial heterogeneity by browsing patchily and exploiting existing gaps. At the tree level, moose damage trees and lower timber quality, but also create substrate types (e.g. dead and dying wood) valuable for many organisms. Co-management of moose and forest requires good monitoring programmes for both plants and animals, as well as extensive ecological knowledge on the relations between moose and their food plants on different spatial levels.
Category: Discussion article
article id 572, category Discussion article
Principles of ecological restoration of boreal forested ecosystems: Finland as an example. Silva Fennica vol. 36 no. 1 article id 572. https://doi.org/10.14214/sf.572
Category: Special section
article id 287, category Special section
Stratification of regional sampling by model-predicted changes of carbon stocks in forested mineral soils. Silva Fennica vol. 41 no. 3 article id 287. https://doi.org/10.14214/sf.287
Monitoring changes in soil C has recently received interest due to reporting under the Kyoto Protocol. Model-based approaches to estimate changes in soil C stocks exist, but they cannot fully replace repeated measurements. Measuring changes in soil C is laborious due to small expected changes and large spatial variation. Stratification of soil sampling allows the reduction of sample size without reducing precision. If there are no previous measurements, the stratification can be made with model-predictions of target variable. Our aim was to present a simulation-based stratification method, and to estimate how much stratification of inventory plots could improve the efficiency of the sampling. The effect of large uncertainties related to soil C change measurements and simulated predictions was targeted since they may considerably decrease the efficiency of stratification. According to our simulations, stratification can be useful with a feasible soil sample number if other uncertainties (simulated predictions and forecasted forest management) can be controlled. For example, the optimal (Neyman) allocation of plots to 4 strata with 10 soil samples from each plot (unpaired repeated sampling) reduced the standard error (SE) of the stratified mean by 9–34% from that of simple random sampling, depending on the assumptions of uncertainties. When the uncertainties of measurements and simulations were not accounted for in the division to strata, the decreases of SEs were 2–9 units less. Stratified sampling scheme that accounts for the uncertainties in measured material and in the correlates (simulated predictions) is recommended for the sampling design of soil C stock changes.
article id 5554, category Article
Calculation and comparison of different permanent sample plot types . Silva Fennica vol. 29 no. 2 article id 5554. https://doi.org/10.14214/sf.a9205
A calculation procedure is presented for calculating and analysing remeasured permanent sample plots. Data for eight different fixed and variable size plot types were simulated on the basis of two stands whose trees were mapped and measured in 1982 and 1986. The accuracy and efficiency of the plot types were assessed and compared.
The calculation procedure is based on tree-wise expansion factors and the division of tree sampled into state/measurement classes. Nine classes were required for variable size plots and six for fixed size plots. A relascope plot with basal-area factor 1 (m2/ha) proved to be most efficient for estimating basal-area at a given time and a fixed size circular plot with radius 10 m for estimating basal-area increment over a given time period.
The main problems were related to the estimation of non-measurable variables, e.g., the initial diameters of ingrowth trees, i.e., trees having passed the threshold size during the measurement period. Most problematic were cut trees belonging to the ingrowth or sample enlargement classes. It is nevertheless thought that the system is appropriate for monitoring forest changes and making sensitivity analyses with permanent sample plots.
article id 5507, category Article
Methods to estimate forest health. Silva Fennica vol. 27 no. 2 article id 5507. https://doi.org/10.14214/sf.a15668
A range of different indices are available for assessing the health of trees in forests. An even larger range can be used for the assessment of the health of forest ecosystems. Most studies made in connection with ”forest decline” and the impact of air pollution and other environmental stresses on forests have concentrated on the assessment of crown transparency and crown discoloration in individual trees. These are non-specific indicators which are now known to be sometimes of relatively little value when determining the health of a forest ecosystem. Numerous problems exist with both, and the standardisation of assessments between and even within countries has not been achieved. Consequently, studies claiming to compare ”defoliation” between different countries cannot be substantiated. The emphasis on crown transparency and crown discoloration has resulted in the neglect of a number of other indices that could be of considerable value. These include a variety of visual measures of crown condition and also several non-visual bioindicators. Some of these techniques are objective, reducing the present reliance on observed standardization. A large number of potential techniques are currently at the research stage and have yet to be adequately tested in field trials. This represent an area where a substantial amount of further research is required.
article id 5405, category Article
A field system for measuring the gas exchange of forest trees. Silva Fennica vol. 24 no. 1 article id 5405. https://doi.org/10.14214/sf.a15557
A third generation of forest tree gas exchange measuring system design for the use in the field is described. The system is designed to produce data for determining the dependence of the rate of tree photosynthesis, respiration and transpiration on environmental factors. The system consists of eight cuvettes, a tubing system, two infrared gas analysers, an air flow controller, a data logger, and a computer. The measuring cuvette is a clap type, i.e. it is mostly open, only closing during measurement. CO2 exchange is measured as the change in the cuvette concentration of CO2, and, transpiration is measured as the increase in water vapour concentration while the cuvette is closed. The environmental factors measured are temperature, irradiance and air pressure. The system was planned in 1987 and constructed in 1988. It worked reliably in late summer 1988 and the quality of data seems to be satisfactory.
The PDF includes an abstract in Finnish.
article id 5343, category Article
Regional and species variations in metal content of two woodland mosses Pleurozium schreberi and Hylocomium splendens in Finland and northern Norway. Silva Fennica vol. 22 no. 1 article id 5343. https://doi.org/10.14214/sf.a15500
The woodland mosses Pleurozia shcreberi (Willd. ex Brid.) Mitt. and Hylocomnium splendens (Hedw.) Schimp. were used in air pollution monitoring. During late summer and autumn 1977, 44 samples of Pleurozia shcreberi were collected in semi-open coniferous forests from Southern Finland (60°N) to Northern Finland and Northern Norway (70°N). Additional 26 samples of Hylocomnium splendens were collected in similar places south of 61°30’N. Analysis of both moss species revealed decreasing concentration gradients from south to north for Cu, Fe, Pb and Zn. Conversely, Mn and Mg levels increased with latitude, while Ca did not change significantly. Some decreasing west to east concentration gradients for Cu, Zn and Pb were measured in P. schreberi and in H. splendends collected from Southern Finland.
A comparison between these two mosses showed significant differences in Cu content (ave. 22% higher in H. splendends) and Zn content (ave. 8% higher in P. schreberi). However, the differences were considered minor in relation to regional differences in Finland.
In local study of emissions from the Koverhar steel works in Southern Finland, Fe and Zn concentrations in P. schreberi and H. splendens were found to decrease significantly with increasing distance up to 6 kilometres north and south of the source.
The PDF includes a summary in Finnish.
article id 5307, category Article
Forest inventory by compartments using satellite imagery. Silva Fennica vol. 21 no. 1 article id 5307. https://doi.org/10.14214/sf.a15464
A method for using satellite data in forest inventories and updating is described and tested. The stand characteristics estimated by the method showed high correlation with the same characteristics measured in the field. The correlation coefficients for volume, age and mean height were about 0.85. It seems that the method is applicable to practical forestry. Extensive work in programming, however, is required.
The PDF includes an abstract in Finnish.
article id 5142, category Article
Responses of transplanted lichens to sulphur dioxide dosages - a new semi-statistical dosage/injury model. Silva Fennica vol. 15 no. 4 article id 5142. https://doi.org/10.14214/sf.a15369
A semi-statistical model is suggested for monitoring injuries of plants for long-time field exposures (months). The model is based on the following assumptions:
1. The concentrations of air pollutants in the atmosphere follow the Johnson SB distribution.
2. The degree of plant injury is proportional to the logarithm of air pollutant dose.
3. No injuries occur below a certain dose level.
4. A dose is defined as the air pollutant concentration multiplied by the duration of exposure raised to an exponent.
Based on the air pollutant frequency distribution a total dose for the exposure period is calculated by integration, and the total dose is related to the observed plant injury by non-linear regression. The model is tested for long-time exposures of sulphur dioxide to transplant lichen in natural environment.
article id 5140, category Article
Monitoring of coniferous forest ecosystems in Sweden. Silva Fennica vol. 15 no. 4 article id 5140. https://doi.org/10.14214/sf.a15367
A monitoring program is planned for the terrestrial environment around industries in Sweden, which emit acid compounds and heavy metals. Directions for the County Government Boards are being prepared. The paper deals with the present pollution situation in Sweden, based on recent scientific results, the justifications for local monitoring, and the organizing of the monitoring including the parameters suggested.
Four examples from a case study at an oil power station illustrate reporting of the data and the difficulties in interpreting the results. The examples are the distribution of a lichen indicator, heavy metal content and phosphatase activity in the moor layer, soil respiration and tree growth.