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Udział oraz dokładność szacowania pozostałości zrębowych w ogólnej masie pozyskanego drewna

100%

Gendek A., Wezyk P., Moskalik T.

Sylwan

2018

tom 162

nr 08

Due to the observed impacts of climate change on the natural environment, the demand for energy from renewable sources is growing, especially in the last decades. One of the possibilities in this respect is the use of forest biomass, especially that one which comes from logging residues. This type of wood raw material is obtained primarily in mature forests and during late thinnings. Estimation of the expected volume of logging residues from a particular cutting site is currently carried out in the State Forests, National Forest Holding with an accuracy oscillating at an acceptable level of ±40%. The purpose of this study was to estimate the share of logging residues in the total volume of the harvested biomass and to determine the difference and error between the estimated volume to be sold and actually harvested. The research was carried out at the 164 logging sites located in 10 forest districts of north−eastern part of Poland. The average volume of logging residues was 37.7 ±14.4 m³/ha, and the average error of their estimation was –6.1%.

Dokładność określania świeżej masy strzał jodły na podstawie przeliczników wagowo-objętościowych

84%

Ochal W., Wertz B., Grabczynski S., Orzel S.

Sylwan

2018

tom 162

nr 04

The paper describes the accuracy of estimation of silver fir stem fresh mass on the basis of volume to weight conversion factor, derived from samples, collected from few different places along the stem. The research material contained 13 sample trees selected from homogenous 70−years old stand, situated in mountainous area of the Beskid Sądecki in Polish part of the Carpathians (S Poland). Volume over the bark of sample trees was calculated with section−wise method and the whole stem fresh biomass was directly weighted. For each sample tree three stem discs were collected at ⅙, ½ and ⅚ of tree height, their weight and volume were precisely determined and the biomass conversion factors (equivalent of stem density) were calculated. The assessment of the accuracy of whole fresh stem biomass was conducted according to five variants: for the biomass conversion factors derived from each individual stem disc (lower, middle or upper), from weighted mean density and on the basis of the constructed mixed model, where relative height and diameter were treated as fixed effects and influence of individual trees was included as a random term. The volume of sample fir stems ranged from 0.15 to 2.22 m³, while their fresh biomass varied between 138.1 and 1896.7 kg. Obtained results show that variation of the density was higher within stems than between them (coefficient of variation amounted to 8.4% i 3.3% respectively). The average density increased along stem, from 835.6 kg/m³ for lower part (⅙H) to 986.8 kg/m³ for the upper part (⅚H). Estimating the biomass on the basis of just lower stem disc resulted in the average relative error equal to –5.8%, while for middle stem disc the error was +1.2%, and for upper disc +11.3%. The use of conversion factors derived from weighted average density of all three stem discs resulted in average bias equal to –1,7% with standard error 1,0%. Despite the presence of mean bias of –2.3%, the constructed density model gave the most precise estimation of the stem biomass (standard error 0.7%), which indicates the reasons for its further improvements and usage.

Ograniczanie wyników

2 Sylwan

1 Gendek A.

1 Grabczynski S.

1 Moskalik T.

1 Ochal W.

1 Orzel S.

1 Wertz B.

1 Wezyk P.

2 2018

Wyniki wyszukiwania

Udział oraz dokładność szacowania pozostałości zrębowych w ogólnej masie pozyskanego drewna

Dokładność określania świeżej masy strzał jodły na podstawie przeliczników wagowo-objętościowych