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The Effect of Forest Practices on Quality of the Harvested Crop 总被引：2，自引：0，他引：2
The paper reviews the effects of forest management practiceson wood quality in softwoods. The forester modifies growth ina variety of ways but most commonly by spacing, either at plantingor in thinning, by pruning, and by fertiliser application. Hisprimary objective is to enhance rates of growth but he shouldbe aware of the consequences of his actions on wood properties.Of special importance are those properties which affect technicalperformance and so commercial acceptance, such as knottiness,density, grain angle and incidence of compression wood, andthe extent to which these are affected by silvicultural operationsforms the main part of the paper. The limited information whichis available is often apparent; there is a need for furtherwork to examine the effects of vigour of growth on most propertiesbut especially on grain inclination and compression wood development,to distinguish response more clearly in terms of types of ringstructure, age, and conditions of growth, and to seek a physiologicalexplanation for observed changes. 相似文献
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The effects of planting distance at establishment on the structuralperformance of timber from unthinned crops of Sitka spruce areexamined. Initial plant spacing is an important factor affectingthe structural performance of timber with loss in performanceparticularly marked as planting distances increase from 1.5to 3.0 m. Factors associated with planting distance that affectstructural performance include log grade, determined mainlyby stem straightness, knot number and knot size, and the proportionof juvenile wood; all are adversely affected and contributeto a lowering in the structural performance of sawn wood asplanting distances widen. It is recormnended that in order toobtain acceptable yields of structural timber meeting StrengthClass 3 from unthinned crops, planting distance should not exceed2 m and it is considered prudent to adopt the same spacing forcrops where line or other systematic methods of thinning areanticipated. However, Strength Class 3 is a minimum requirementfor structural timber and every effort is needed to improveon it by the use of superior stock and by management that favoursthe production of quality logs and timber. 相似文献
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As part of a programme aimed at improving Sitka spruce timber(Picea sitchensis (Bong.) Carr.), a study has been made of thevariation in some wood characteristics of significance in affectingtechnological behaviour, and the effect on these characteristicswhen trees of outstanding form and vigour are selected. It wasfound that:
- There is a similar pattern of within-tree variationin density,tracheid length, and grain inclination for bothselected andaverage, final crop trees.
- There is a very appreciablevariation in these timber characteristicsbetween trees at comparableages, indicating the potential forimprovement by selection.
- There is a reduction in density and some increase in graininclinationbut no difference in tracheid length in vigorouscompared withaverage-growth trees at comparable ages.
- Thereis no evidence that selection for above average densityhasan adverse effect on tracheid length; it tends to favourtreeshaving a high minimum early wood density and, to a limitedextent,wood with narrow cells.
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The use of a breast-height core for estimating wood densityof the whole stem has been examined for British-grown Sitkaspruce. Regression equations have been derived for stem lengthsto 7 cm and 18 cm top diameter over bark and the precision ofthe estimates determined for both between- and within-site comparisons. The breast-height sampling technique is considered to be ofpractical value for demonstrating differences of density of15 kg m–3 or more, depending on the number of samplestaken, when a comparison is made between sites; when a comparisonis made within a site, the results show that the method canbe used to demonstrate differences of 8 kg m–3 or more.It clearly offers scope for the nondestructive examination ofthe effect of silvicultural operations on wood density and yieldsof wood substance. 相似文献
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In seventy years, timber use, at first governed by craft practices,has been transformed to a technology determined by scientificprinciples, made possible by the research on wood undertakenduring the period. The pattern of this research, those undertakingit, the factors determining it and its funding in the UnitedKingdom are considered. Today, forest products research is ata low ebb, compared with that in earlier decades, but it issuggested that with a rapidly expanding UK resource, a continuingnational dependence on timber and timber products and the environmental benefits from growing and using wood, the need for aneffective forest products research capability remains as importantas ever. 相似文献
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A study of the effect of vigour on the within-ring componentsof young, plantation-grown Sitka spruce (Picea sitchensis (Bong.)Carr.) has been made as a contribution to a more effective selectionof timber having superior timber yields and to appraise thelikely effect of forest management practices which, by influencingvigour of growth, affect wood quality. It was found that as ring width in Sitka spruce increases:
- Thereis an increase in early wood width without a correspondingincreasein late wood and so a greater proportion of early wood.
- Thereis a reduction in the average density of the early woodcomponentof the rings.
- Because of the combined effects of 1 and 2,there is a reductionin wood density as vigour of growth increases.
- There is a lower minimum early wood density.
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Eradicating the invasive topmouth gudgeon, Pseudorasbora parva, from a recreational fishery in northern England 总被引：2，自引：0，他引：2
Abstract An established population of the invasive topmouth gudgeon, Pseudorasbora parva (Temminck & Schlegel), was discovered in a recreational fishery in Northwest England in 2002. As the lake was seasonally connected to a river catchment, providing potential for dispersal, a containment and eradication programme was initiated. Containment involved screening of outfalls and preventing fish movements off site. Eradication involved the fishery being treated twice with a rotenone-based piscicide, in March and April 2005. The mean P. parva density prior to rotenone application was 6.1 m−2 ; following the application, none were recorded. Non-target species in the fishery were removed prior to the application; following rotenone degradation, they were re-introduced and subsequently spawned, with recording of young-of-the-year. This contrasts with 2004 when only young-of-the-year of P. parva were recorded. As the eradication appeared to be successful, the method is considered suitable for use on other populations posing a similar threat of dispersal of the species into rivers and on other invasive fish populations in undesirable locations. 相似文献
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