Current issue: 54(2)
Physical soil properties have a marked influence on the quality of forest sites and on the preconditions for forest growth and management. In this study, water retention characteristics (WRC) and related physical soil properties in addition to vegetation coverage and tree stand data were studied at upland forest sites in Finland. Fixed and mixed models between soil and site characteristics were formed to estimate physical and hydrologic soil characteristics and the site quality with indirect co-varying variables. In the present data, the site quality index (H100) shows a high coefficient of determination in respect to the temperature sum. It is also related to soil fine fraction content, topsoil pH and water retention at field capacity. The thickness of the humus layer is predictable from the pH and cover of xeric and mesic plant species. The soil fine fraction content (clay + silt) is closely related to water retention at field capacity, the soil layer and site type, and without WRC to the temperature sum and site index and type, as well as the slope angle. The soil bulk density is related to organic matter, depth (layer) or alternatively to organic matter, slope and field estimated textural class (fine, medium, coarse). Water retention characteristics were found to be best determinable by the fine fraction content, depth and bulk density. Water content and air-filled porosity at field capacity are closely related to the fine fraction. This study provides novel models for further investigations that aim at improved prediction models for forest growth, hydrology and trafficability.
The primary aim of this study was to clarify the chipping productivity and fuel consumption of tractor-powered and truck-mounted drum chippers when chipping pine pulpwood at a terminal. The secondary aim was to evaluate the impact of wood storage time on the chemical and physical technical specifications of wood chips by chipping pulpwood from eight different storage time groups, using Scots pine (Pinus sylvestris) pulpwood stems logged between 2 and 21 months previously at the terminal with the above-mentioned chippers. Thirdly, the impact of sieve mesh size on the particle size distribution of wood chips from different age groups was compared by using an 80 mm × 80 mm sieve for a tractor-powered chipper and a 100 mm × 100 mm sieve for a truck-mounted chipper. With both chippers, the chipping productivity grew as a function of grapple load weight. The average chipping productivity of the tractor-powered chipper unit was 19 508 kg (dry mass) per effective hour (E0h), and for the truck-mounted chipper the average productivity was 31 184 kg E0h–1. The tractor-powered drum chipper’s fuel consumption was 3.1 litres and for the truck-mounted chipper 3.3 litres per chipped 1000 kg (dry mass). The amount of extractives or volatiles did not demonstrate any statistically significant differences between storage time groups. The particle size distributions with both chippers were quite uniform, and the storage time of pulpwood did not have a significant effect on the particle size distribution in any chip size classes. One reason for this might be that the basic density of chipped wood was homogenous and there was no statistical difference between different storage times. The use of new sharp knives is likely to have affected chip quality, as witnessed by the absence of oversized particles and the moderate presence of fines. The use of narrower 80 mm × 80 mm sieves on Scots pine material does not seem to offer any benefit compared to 100 mm × 100 mm from the chip quality point of view.
The role played by the medium and fine silt and clay contents in determining the quartiles and the degree of stratification from a cumulative particle-size curve was studied in order to determine what time savings could be made in the sedimentation phase of soil mechanical analysis. The clay content of the samples was, in general, found to be so small that it did not affect the parameters studied. In contrast to this, the medium and fine silt content affected the lower quartile of the distribution for many soils classified as finer than medium sand. Consequently, only the omission of the determination of the clay fraction can be recommended as a time-saving measure in mechanical analysis.
The PDF includes a summary in Finnish.
The particle size distribution affects several properties of the soil, thus, the ability to define the texture type of the soil as accurately as possible in field conditions is essential. The soil particle size classification devised by Atterberg (1912) is used in Finnish forestry. The study is based on a small laboratory material. The correlation between some characteristics of the soil particle size distribution, field capacity and cation exchange capacity were determined.
The particle size characteristics such as the relative proportion of different particle sizes, average particle size (Md) and parameters depicting the degree of sorting were determined. The relative proportion of soil particles below 0.06 mm correlated best with both field capacity and cation exchange capacity. Similarly, the average particle size and the degree of sorting correlated well with the field capacity and the cation exchange capacity.
The use of sorting characteristics is not well-suited to the type of soil sample material containing a high proportion of particles of varying size as was used in this material. Such characteristics are probably more easily applicable to the fine sand and sand sediments which are predominant in Finnish forest soils. The most useful particle size distribution characteristics in soils having a great variation in particle sizes were the average particle size and the relative proportion of silt and clay. Thus, the nutrient and water status of the soil can be predicted to some extent by examining the percentage of silt and clay, average particle size and the degree of sorting.
The PDF includes a summary in English.