172,686 research outputs found
Dissociation of phantom limb phenomena from stump tactile spatial acuity and sensory thresholds
No full textMost amputees experience phantom limb sensations and/or phantom limb pain as well as residual limb (stump) pain that are resistant to treatment. Phantom phenomena are not homogeneous; each patient presents with a unique combination of spontaneous or evoked sensations, pain, and/or awareness. In an effort to understand the underlying mechanisms, postamputation pain has been subclassified based on the perceived sensory qualities reported by the individual. However, little is known about the relationship between subjective phantom phenomena and sensory function of the residual stump. The aim of the present study was to determine if sensory processing, as measured psychophysically, reflected subjective reports of specific qualities of phantom and/or stump sensory phenomena. Twelve individuals who had recently (within 6 months) undergone traumatic unilateral upper extremity amputation participated in the study. Limb temperature, thermal thresholds, tactile sensory thresholds and tactile spatial acuity were compared between the residual limb and the intact limb, and related to patient reports of specific stump and phantom sensory phenomena. All but one subject reported phantom sensations and/or phantom pain. The remaining subject reported only stump pain. Mean skin temperature of the residual limb was significantly lower than that of the intact contralateral limb by approximately 0.9°C in the proximal portion of the stump and 1.7°C at the stump tip. However, the temperature of the stump (compared with the intact limb) did not reflect subjective reports of stump or phantom limb thermal characteristics. Thermal threshold abnormalities differed among patients, and did not suggest any pattern of small fibre loss of function or generalized hyperexcitability. Other than within grafted tissue or near the scar area, skin areas that the patient described as abnormally sensitive or tender to touch were not accompanied by corresponding abnormalities in static tactile thresholds or tactile spatial acuity. Tactile spatial acuity was heightened near the scar area only. The proportion of subjects who had decreased two-point discrimination thresholds at the stump did not differ significantly according to the reporting or non-reporting of dual percepts. Thus, despite a common injury, the sensory abnormalities varied within this cohort of subjects. In addition, psychophysical threshold measures of sensory function did not reflect, in any simple way, subjective phantom phenomena. Therefore, classification of phantom phenomena based on peripheral sensory function may be a misleading step in the search for specific mechanisms underlying postamputation sensory phenomena
Establishment of Heterobasidion annosum s.l. infections in young Norway spruce dominated stands
No full textOne of the worst pathogens on Norway spruce, Heterobasidion annosum s.l., can establish in previously healthy trees by spores landing on freshly made stumps from where mycelia can grow via root grafts and contacts to the adjacent tree. The risk of spore infection as well as disease transfer has been considered to be negligible in young stands due to the small target size of stumps and their small root systems. Consequently, small stumps created during precommercial thinning and late precommercial thinning are usually not treated with protective agents against spore infections as is commonly done during commercial thinnings. The objective of this thesis was to increase the knowledge regarding establishment of H. annosum s.l. infections in young Norway spruce dominated stands, in order to provide a renewed knowledge-base for forest management decisions.
The results from field studies showed that although the risk of spore infections increased with increasing stump size more than half of small Norway spruce stumps created during precommercial thinning and late precommercial thinning were infected with H. annosum s.l. (Paper I, II). Of the two Heterobasidion species present in Sweden H. parviporum had a competitive advantage over H. annosum s.s. during colonization of Norway spruce wood (III). Norway spruce stumps as small as 2.5 cm in diameter could transfer infection to trees and the risk of transfer increased with increasing stump size (IV). Stump treatment with the biocontrol agent Phlebiopsis gigantea decreased the amount of spore infections on small stumps (I). The reduction was within the lower range reported from commercial thinning stumps. Simulations of decay development after late precommercial thinning indicated that a substantial amount of the decay at final felling could be attributed to late precommercial thinning. Further, the simulations indicated that stump treatment could reduce the decay at final felling if removal intensities were high. However, the economic outcome of stump treatment varied (II).
In conclusion, there is a risk of new H. annosum s.l. infections establishing during silvicultural operations in young Norway spruce dominated stands. Precautionary measures to reduce the risk such as early precommercial thinnings or, where applicable, winter fellings or stump treatment could be considered
Soil physical disturbance resulting from stump harvesting
No full textThis paper describes a detailed study of stump harvesting in Lamloch Forest in north Dumfries and Galloway from 2010 to 2014. The study explored both the nature and extent of soil disturbance resulting from stump harvesting using a variety of standard and innovative techniques. Stump harvesting disturbance was compared with that of other forestry practices. To complement the two-dimensional and subjective nature of visual assessment techniques, a radiometric approach was adopted, utilising residual Chernobyl 137Cs fallout to determine the degree of soil mixing. To support bulk density measurements, micromorphological analyses of soil thin sections were carried out to investigate the impact of compressive force on pore space. Low-cost tracer devices were deployed in the soil around stumps prior to extraction to permit the monitoring of soil lateral movement during stump extraction. The study showed that stump harvesting followed by restock, when carried out under current guidelines, disturbed around five times the volume of soil compared to that disturbed by trench mounding. Stump harvesting also resulted in a net reduction in soil bulk density. Suggestions for modification of stump harvesting operations are made to reduce soil disturbance, including avoiding raking over the site following stump harvesting which is estimated to add a further 10% to the volume of soil disturbed
Pre-commercial thinning of beech (Fagus sylvatica L.)
No full textThis paper reports early effects of stump height on the growth and natural pruning of potential crop trees after pre-commercial thinning of a young stand of naturally regenerated beech (Fagus sylvatica L.) in Denmark. The experiment comprises five treatments based on combinations of three grades of pre-commercial thinning and three stump heights. Treatments include the unthinned control, thinning only of whips and wolf trees (using low stumps), and thinning for potential crop trees using low, medium or high stumps. All treatments were replicated three times. Stump heights averaged 10, 90 or 230 cm, respectively. Pre-treatment stem number (live trees) varied from 17,500 to 41,000 per ha. In the potential crop tree treatment, post-treatment stem number ranged from 4,750 to 9,500 per ha. Following two growth seasons, the quantity of stump regrowth increased with increasing stump height, the rate of stump regrowth increased with increasing stump height, the diameter growth of potential crop trees increased with decreasing stump height, the increase in stand height did not depend on stump height or post-treatment stem number, and the natural pruning of potential crop trees increased with increasing stump height. It remains to be seen, whether these trends hold in the long run, and whether additional economic return from the increase in wood quality with increasing stump height compensates for the reduction in diameter growth
Long and short term effects of stump harvesting on saproxylic beetles and ground flora
No full textResearch on the effects from forest management on biodiversity has been going on for decades but still there are many questions unanswered. With every introduction of a new forestry method there is risk for increased pressure on biodiversity.
The harvesting of low stumps left after final harvesting is a relatively new method used in forestry. I therefore investigated the importance of low stumps for saproxylic (wood living) species by comparing the species richness, abundance, and species assemblages of beetles in low stumps with the levels in high stumps and logs. Furthermore, I also investigated the long-term effects from stump harvesting on this group of species. I used window traps to collect beetles in young forests that had been stump harvested 25 years prior to the study and compared these stands with stands of the same age that had not been stump harvested. I also wanted to investigate the short-term effects from stump harvesting on the ground flora. This was done by comparing the plot frequency of all bryophytes and vascular plants found on stump harvested clear-cuts with clear-cuts that had not been stump harvested.
Low stumps on clear-cuts were proved to constitute important habitat for wood living beetles and they produced as many species and individuals of saproxylic beetles as logs and high stumps. Individual species showed preference for certain substrates. For example, the saproxylic fungivore Enicmus rugosus, was mostly found on low stumps. The overall impression after comparing the three substrate types was that low stumps might be an underestimated source of habitat for wood living insects. The long-term experiment indicated that effects of stump harvesting may last two and a half decades on certain groups of beetles. However, the effects from the surrounding landscape explained the patterns in beetle occurrence better than stump harvesting did. Results from the study of short-term effects on the ground flora showed that the effects from stump harvesting were limited to common species of bryophytes and vascular plants. The plot frequency of the common dwarf shrub Vaccinium vitis-idaea was, nevertheless 80% lower on the stump harvested clear-cuts, indicating that the early response of stump harvesting may be strong on individual species
Heart rot of spruce and alder in forests of Latvia
No full textHeart rot causes great decrease in timber quality throughout the world. In the conifer forests of Northern Hemisphere the most significant losses are caused by fungi from the Heterobasidion annosum species complex. The spread of the disease is favored by forest management, as the fungus can use freshly cut stumps as an infection court, and so extend through root contacts to infect neighboring trees.
The country-scale inventory revealed that about 22% of Latvian spruce trees contained heart rot, which extended on average 6.6 m within the tree stem; the most commonly associated fungus being H. parviporum. These facts highlight the need to take actions to reduce the level of inoculum in already infested stands. Stump removal and the planting of resistant tree species are two options for that.
Long-term trials carried out in Scandinavia showed that stump removal could significantly decrease the proportion of infected trees in regenerated stands, although the effectiveness of this procedure may eventually decrease with time. In addition, this method is quite drastic and the adverse influence of continuous stump removal on stand biodiversity and productivity should be taken into consideration. The trail conducted in Finland showed that stump removal had a positive impact on seedlings growth, but influenced negatively mycorrhization and species richness.
The other management method which could be employed is the planting of resistant tree species, especially broadleaved trees. In the work undertaken for this thesis heart rot incidence, associated fungi and decay caused yield losses were studied in Latvian grey (Alnus incana) and black alder (A. glutinosa) stands. Despite the high decay incidence and the number of associated fungal species, no single H. annosum s.l. was found. Also, our data showed that the proportion and size of the heart rot column increased with tree age. These data suggest that a short rotation of fast growing broadleaved trees (not only Alnus, but also species of Populus, Betula, and Salix) could be used for clearing up the Heterobasidion inoculum
Stump Puller.
No full textPatent for a simple and effective stump puller that pulls stumps entirely from the ground using a large amount of force. The machine uses a series of pulleys, hooks, levers, and cranks
Stump Puller.
No full textPatent for a stump-puller that "can be quickly assembled and taken apart, to devise a device which will admit of the rope being quickly paid off from the capstan after the stump has been uprooted, and, finally, to provide a machine which can be easily handled and which will perform the required work in a rapid and satisfactory manner and which can be transported from one stump to the other by being dragged upon the ground" (lines 10-19)
Stump Puller.
No full textPatent for a new and improved stump puller. This design's object "is to provide a simple, cheap, and effective stump-puller, readily portable and easily operated by one man and a horse; and to that end the novelty consists in the construction of the same" (lines 10-15)
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