Browsing by Subject "soil compaction"

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  • Käld, Tobias (Helsingfors universitet, 2013)
    In Finland thinning quality is assessed on a yearly basis by the Finnish Forest Centre. During recent years the results of these assessments have been a source of concern within the coastal region of operation. Metsäliitto, being one of the largest forest operators within the coastal region and Finland as a whole, is concerned by the high residual stand damage found. Metsäliitto perform follow-ups on the feedback received from the Finnish Forest Centre but also performs thinning quality assessments off their own. The thinning quality method used by the Finnish Forest Centre is time consuming and therefore poorly suitable for use by wood procurement companies. This led to the development of an alternative method by Metsäteho Oy. Metsäliitto was represented in the work group that developed this new method but has chosen to develop a method of its own. The purpose of this master thesis is to clarify whether the results from Metsäliittos thinning quality assessment method correlate in a sufficient manner with those of the method developed by the Forestry Development Centre TAPIO. Furthermore the thesis study how the results of two alternative methods correlate. Focus is placed on residual stand damage but also the possibility of a potential connection between TAPIOs placement of sample plots and residual stand damage results is studied. As Metsäliittos method includes a complete inventory of soil compaction it is studied how TAPIOs and Metsätehos results hold up against those of Metsäliittos method. A study of the correlation between results for forwarder track distance between Metsäliittos and Metsätehos methods is also conducted. The sites of this study were chosen based on the Finnish Forest Centres random sampling for thinning quality assessments performed during 2010 and 2011. From those thinning quality assessments the ones performed in the Swedish speaking parts of Ostrobotnia where thinning actions had been performed by Metsäliittos contractors were sieved and chosen to form the sample of this study. The fieldwork of this study was performed in July 2011. Thinning quality assessments according to Metsäliittos and Metsätehos models were performed on all sites. The results of the thinning quality assessments performed according to TAPIOs method were acquired from the Finnish Forest Centre. This study being a method comparison study where the true values of the objects are not known, methods of analysis based on hypothesis testing was not used. In order to create an overview of the trends in results for the different methods, as well as their correlation to each other, Bland&Altman diagrams were created (Altman & Bland 1983 and Bland & Altman 1999). The main results of this study show that Metsäliittos and TAPIOs results for residual stand damage do not differ in a statistically significant way. Metsäliittos and Metsätehos results on the other hand are not to be compared. Metsätehos and TAPIOs results are not either to be compared which has been stated by Poikela (2003b). TAPIOs and Metsätehos methods estimate the proportion of soil compaction in a sufficient manner compared to Metsäliittos method. Furthermore it was concluded that results for forwarder track distance correlate well between Metsäliittos and Metsätehos methods. Any connection between TAPIOs sample plot placement and results for residual stand damage could not be detected. The conclusions of this study are that Metsäliittos and TAPIOs results for residual stand damage, with reservation for the small sample size of this study, are comparable. Metsäliittos and Metsätehos results are not compatible from which we conclude that Metsäliittos method is not replaceable with the one developed by Metsäteho. Nor shall Metsätehos method be used as a complement to Metsäliittos as one will then acquire two incompatible data sets. Both Metsätehos and TAPIOs results for soil compaction are compatible with those of Metsäliittos method. This could be utilized in order to improve the time effectiveness of Metsäliittos method. For further method improvement Metsäliitto could adopt Metsätehos method for determination of forwarder track distance. As results from Metsäliittos and TAPIOs thinning quality assessments can be compared without a loss of reliability, Metsäliitto could compile the results from their own assessments and TAPIOs assessments in order to get a more statistically representative picture of the quality of their thinnings. This would result in even better future possibilities of monitoring and evaluating how well the company’s goals are met.
  • Gustafsson, Markus (Helsingfors universitet, 2013)
    Soil compaction is a long known phenomenon in agriculture affecting several soil functions, crop yield and environment. Soil compaction is caused e.g. by natural processes and field traffic. In the agriculture soil compaction is often defined as reduced soil air porosity caused by field traffic in wet soil conditions. Ever increasing weight of agricultural machines can cause stress propagation in deep soil layers which increases the risk of subsoil compaction. Subsoil compaction can alter soil pore volume and continuity, deteriorate soil air conditions and air permeability and also increase water surface runoff and gaseous nitrous oxide emissions to the atmosphere due to denitrification. Effects of subsoil compaction on soil properties have been reported to be very long-term and to remain measurable for decades. This work was carried out as a part of the Nordic Poseidon project, investigating the arable soil compaction effects on soil functions and the environment. The objectives of this study were to design and implement a measurement program for soil sample gas diffusion coefficient measurements and secondly to analyze the continuous measurement data of soil moisture and temperature determined in situ (in the defined position) on a long term soil compaction experimental site in Southern Finland, Jokioinen. In the measurement program the accuracy of gas diffusion coefficient calculation process was confirmed by demonstration measurements. The measurement program eased the usage of gas diffusion measurement equipment and also enabled wider studies than in the past. In the Jokioinen experimental site soil temperature and moisture were found to vary from year to year depending on the weather conditions and the amount of rainfall. On the rainy summer 2011 the moisture level was higher in compacted soil than in uncompacted soil. The difference between the compacted and uncompacted soils was possibly caused by weakened hydraulic conductivity in the compacted subsoil. In addition the compaction treatment increased temperature variation during the day in the upper 15 cm layer possibly due to higher thermal diffusivity of the soil.
  • Saarilahti, Martti; Anttila, Tero (1999)
    The increased awareness of environmental issues has created a need for evaluating the usefulness of mobility models for Nordic forestry conditions. A frame of reference based on the WES-method was used for developing empirical rut depth models for moraine forest sites. It was found that the penetration resistance in critical layers alone was an adequate soil input variable, even if the studied soils had very large variations in stoniness. When comparing the results with earlier models developed for organic soils, it was found that the same models apply for both types of soils. The method and models seem reliable enough for avoiding operations on too risky soils.