Publikasjoner
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2018
Sammendrag
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Sammendrag
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Sammendrag
The goal of this study was to assess the long-term effects of partial harvesting and supplementary soil scarification on the frequency of root and butt rot in managed uneven-sized Norway spruce stands. Frequency of rot and the population structure of the rot fungi were assessed on 1353 stumps after clear-cutting 21 years after a selection harvesting experiment. The initial experiment was comprised of three harvest strength (low, intermediate and high) of single-tree selection, removing approximately 25, 45 and 65% of the stand basal area. Uncut control plots were established at the same time. Supplementary soil scarification was applied in subplots within the single-tree selection plots, using a medium-sized excavator. After clear-cutting the stumps were analyzed with respect to rot caused by Heterobasidion parviporum, Armillaria spp., Stereum sanguinolentum as well as other rot fungi. Rot caused by Armillaria spp. was most common (8.6% of the stumps), while infection by H. parviporum (2.9%) or S. sanguinolentum (3.0%) was less frequent. The group “other rot” (5.4%) comprised 21 identified taxa, each occurring in 1–15 stumps. Significantly lower rot frequencies were found for the uncut control (16.3%) and intermediate harvest strength (15.7%), compared with low harvest strength (23.6%). A rot frequency of 21.0% was found in the high harvest strength. In two of three harvest strengths, the rot frequency was higher than for the uncut control. As the observed rot frequencies did not increase consistently with increasing harvest strength, the results do not completely support the initial expectations of increased rot after single-tree selection compared with the uncut control. However, since the probability of rot in individual stumps on plots treated with single-tree selection was significantly affected by the distance to the nearest strip road (H. parviporum) as well as dependent on the size of and distance to the nearest stump of trees cut during the experimental harvest (H. parviporum, S. sanguinolentum and total rot), it is evident that the single-tree selection harvesting was partially responsible for some of the observed rot. One of the selection criteria in the initial harvest was a sanitary removal of trees of poor vitality. Varying degrees of sanitation felling may therefore have offset the effects of new infections in wounds or spread of rot fungi through adjacent stumps. Supplementary soil scarification in small gaps of the residual stand had no significant effect on the frequency of rot, suggesting that such treatment may be used to facilitate regeneration in uneven-sized spruce stands on similar sites.
Forfattere
Klaus Mittenzwei Hugo Storm Thomas HeckeleiSammendrag
Seeking the answer to the question of how farmers allocate their limited labor resources has a long tradition in the agricultural economics literature (Schultz 1990, Benjamin 1992). The role of off-farm income to close the income gap between farm households and non-farm households has been emphasized by various scholars (e.g. Schmitt 1989, Gardner 1992, Mishra et al. 2002). Ahearn et al. (2006) focus on the role of government subsidies on the allocation decision. This chapter contributes to this literature. In particular, we investigate the relationship of farmers’ decisions to combine farm income with off-farm wage income and to what extent this affects their total household income. To this end, we combine taxpayer information and agricultural data at the farm household level to study labor decisions and the income of Norwegian farm households and compare with the income situation of all households. Using data of almost 40 000 farm households for the year 2009, we find that farm households obtain an income that is on average larger than that of all Norwegian households. However, there is a large variation. Descriptive statistical analysis looking at joint distributions of key structural variables, policy support and income at farm level provides unique information.
Sammendrag
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Sammendrag
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Forfattere
Nick Hutchings Seyda Özkan-Gülzari Michel de Haan Daniel L. SandarsSammendrag
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Forfattere
Seyda Özkan-Gülzari Bouda Vosough Ahmadi Alistair W. StottSammendrag
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Forfattere
Bente Føreid Evengy A. Zarov Ilya M. Latysh Ilya V. Filippov Elena D. LapshinaSammendrag
Exposure to sunshine is known to play a role in litter decomposition in some semi-arid areas. The aim of this study was to find out if it also plays a role in higher latitude environments in peat litter decomposition and could contribute to an explanation to the patchy nature of peat litter decomposition. Peat litter from 5 microenvironments (top of slope, bottom of slope, ridge, ryam and hollow) and put out and exposed to the sun or shaded over a summer in Western Siberia, 26 km west of the town of Khanty-Mansiysk. Afterwards the peat litter was incubated in the laboratory - at field capacity or submerged in peat water - and CO2 and methane emission measured. Chemical composition of exposed and control peat litter was also investigated using stepwise extraction. The results indicate that exposure to sunlight does increase subsequent decomposition rate in most peat litters when incubated at field capacity, but the difference between the treatments levelled off at the end of the 2 weeks incubation in most peat litter types. The total extra carbon loss was calculated to be up to about 2 mg C m− 2 over a season. When incubated submerged previous photo-exposure had less effect on CO2 evolution then when incubated at field capacity. No methane emission was recorded in any treatment. Some differences in chemical composition between exposed and shaded peat litters were found that could help explain the differences in subsequent decomposition rate. The results indicate that photodegradation could play a role in peat litter decomposition at higher latitudes when peat is disturbed and exposed to sunshine. However, the effect of photo-exposure in these areas is much smaller than observed in semi-arid areas at lower latitudes.
Sammendrag
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