Productivity of Sitka Spruce in Northern Britain 2. Prediction from Site Factors

Productivity and site data from 187 temporary sample plots wereanalysed by multiple regression analysis to derive models inwhich site variables accounted for 78–86 per cent of thevariation in Sitka spruce productivity (General Yield Class,GYC). Climatic variables (accumulated temperature and windiness)extrapolated from meteorological data and tatter flag resultsaccounted for up to 78 per cent of the variation, the contributionof edaphic factors being small. The best regression models wereassociated with confidence limits of about ± 2.5 m³ ha^–1y^–1 and the mean error for predicting GYC for a forestblock (acquisition) was calculated to be ±1 m³ ha^–1y^–1 These figures were confirmed by the results of a validationsurvey and the application to field prediction of productivityis described.     

Canopy Closure in Sitka Spruce - the Relationship between Crown Width and Stem Diameter for Open Grown Trees

Crown width (CW) and breast height diameter (D) were measuredfor 73 open grown Sitka spruce trees. A highly significant linearrelationship was found between these two characteristics, withmore variation at large values of D. After applying weightingto compensate for this and eliminating the largest tree whichdid not follow the main trend, the equation CW=188. 30 + 15.27Dand D = 0.05865 CW - 8.31 were fitted where CW and D are expressedin centimetres. A comparison is made with equations derivedby other workers. The relationship may be used to predict the time of canopy closurefrom a knowledge of the development of D with age for a givenstand, after defining canopy closure in terms of mean crownwidth and spacing, or mean crown area and the available growingspace.     

Some Effects of Lime and Fertiliser on a Sitka Spruce Plantation

The results of the first six years of a factorial experimenttesting the effects of lime and fertilizers on a 20-year-oldSitka spruce crop in Northein Ireland are described. Fertilizer increased basal area increment of poorly growingtrees on a peaty-gley soil but did not affect an already better-growingcrop. Lime did not affect growth but it reduced the trees' foliarP status, especially on plots given fertilizer. Lime increased microbiological activity in the litter layer,which increased its rate of decomposition and changed it toa form closer to a mull type humus. The numbers of bacteria,actinomycetes and the larger soil fauna were increased by liming.Roots were killed and the mycorrhizal association altered inlimed areas. The effect of lime on the plantation has been complex and, aftersix years, the beneficial and harmful effects on the growthof Sitka spruce appear to be evenly balanced.     

Toxicity of Five Granular Herbicides to Sitka Spruce and Lodgepole Pine

Experimental plots in young plantations of Sitka spruce andlodgepole pine were over-dosed with five granular herbicidesto ascertain the margin of crop safety involved in the use ofpropyzamide, chlorthiamid, dichlobenil, dichlobenil/dalaponmix and atrazine. It is concluded that if the five herbicidesare applied according to the standard rates and dates used inthe experiments, tree damage will be kept to an acceptable minimum.Better shoot growth resulted from herbicide treatment than fromhand weeding particularly where atrazine was used.     

The Effects of Clearfelling a Sitka Spruce Stand on the Water Balance of a Peaty Gley Soil at Kershope Forest, Cumbria

From 1981 to 1985 the water balance of four 2 ha plots of aploughed and drained Sitka spruce plantation was monitored.During 1983, three plots were clearfelled and a fourth was leftstanding as a control. A ground level raingauge over-collected during snow, but otherwisecollected 3 per cent more water than standard raingauges. Annualprecipitation (1259–1688 mm) averaged 1439 mm. The forest canopy intercepted 38 per cent and transpired 12per cent of gross precipitation. Fifty per cent of gross precipitationwas evaporated while the other 50 per cent left the site asrunoff. Throughfall and stemfiow fractions of net precipitationwere 0.87 and 0.13 respectively. After clearfelling, annual runoff increased to 68 per cent ofgross precipitation. After adjustment using the before and aftercomparison in the control plot, the decrease in annual evaporativeloss resulting from clearfelling was 290 mm.     

The Development of Stain in Wounded Sitka Spruce Stems

In order to investigate the severity of staining in woundedSitka spruce stems, the vertical extent of two categories ofstain (based on colour and termed ‘light’ and ‘heavy’)was measured in stems at two sites in south Scotland. Data wereobtained from 98 wounds most of which were between 8 and 14years old and most of which had been caused by Red deer. Theupward extent of stain and its rate of upward spread were positivelycorrelated with wound surface area and length. Most stain wasof the light type which, although it was associated with nearlyall wounds, usually constituted an insignificant defect anddid not commonly extend for more than 1 m ahve wounds. Heavystain occurred above less than half of all wounds studied butwas common above wounds exceeding 300 cm² surface area. Forall wounds, the mean value for the upward extent of heavy stainwas 16.1 cm with a mean rate of spread of 1.9 cm y^–1.However, for wounds exceeding 300 cm² surface area, the valueswere 51.7 cm and 5.5 cm y^–1. These results suggest that,although there is an important effect of wound size on the typeand extent of stain, wounds of the type studied are unlikelyto lead to severe stain and decay in Sitka spruce over a periodof 8–14 years. The results are discussed in relation toother studies on wound staining in conifers.     

陕西辛家山林区云杉母树幼林结实特征指标与海拔高度关系研究

本文通过对陕西省辛家山林业局不同海拔高度云杉母树林初始结实特征指标的调查和结果分析,阐明了海拔高度与云杉幼龄母树林初始结实林龄和其初始结实林龄特征指标的关系,为缩短云杉母树林建设时间提供了科学依据。     

The Interaction of Green Spruce Aphid and Fertilizer Applications on the Growth of Sitka Spruce

In an 11-year-old stand of Sitka spruce (Picea sitchensis [Bong.]Carr.) application of nitrogen fertilizers, at a rate of 10kgN ha^–1 month^–1, increased mean diameter incrementby 12 per cent, while the further addition of phosphorus, at5 kg ha^–1 month^–1, resulted in a 23 per cent increase.An attack by the green spruce aphid (Elatobium albietinum Walker)occurred during the period of fertilizer addition. The mostseverely affected trees showed a reduction in diameter growthof 50 to 56 per cent but the severity of the attack betweentrees was unrelated to the treatments applied. However, fertilizerapplication did hasten the recovery of diameter growth afterdefoliation.     

Some Ring-width Patterns in Sitka Spruce Timber from North America

Variations in ring-width pattern of Sitka spruce (Picea sitchensisCarr.) through most of its life in its natural habitat are demonstratedfrom photographs of ten crosssections. It is suggested thatin addition to the annual fluctuations in ring-width due toclimatic variation, the tree in the natural forest is subjectto periodic suppression and release and that it has considerablepowers of recovery; in plantations, therefore, Sitka spruceshould respond to thinnings made even late in the rotation.     

Needle Damage in Sitka Spruce Caused by Early Autumn Frosts

Autumn frosts preceded by warm weather cause distinctive needlebrowning symptoms on young Sitka spruce trees which have completedshoot elongation. Damage is invariably confined to needles ofthe current year and typically consists of pink or reddish-brownpatches in the centres of needles. Needles clustered aroundthe apical buds are usually unaffected but in extreme casesall current year's needles may be entirely reddish-brown. Thesesymptoms were reproduced on young plants by experimentally freezingthem in a programmed chamber. Widespread damage was observed in the field in October 1971,September 1972 and September 1979 and assessments of field trialsshowed that damage was most severe on southerly provenancesand on trees deficient in phosphorus.     

杉木-闽楠混交林林分结构与生产力功能耦合关系研究

为了研究林分结构与生产力功能之间的关系,探讨确定杉木-闽楠混交林的合理林分结构,为维持群落结构稳定和提高林木生产力提供依据。以湖南省永州市金洞林场杉木-闽楠混交林为研究对象,利用获取的调查数据,运用主成分分析方法,分析平均胸径、平均高、郁闭度、混交度等林分结构因子与生产力功能间的耦合作用。建立林分结构与功能的耦合关系模型,对林分结构和生产力功能进行分析,结果表明,林分结构因子与生产力功能密切相关。生产力综合评价指数较高的林分具有的特征为:中等密度(1 500株/hm~2)、郁闭度为0.7左右、林层结构为复层林。这种结构特征有利于保持较好的生产力功能,是金洞林场杉木-闽楠混交林的最佳林分结构。     

Growth Models for Unthinned Stands of Sitka Spruce in Northern Ireland

A model for the net basal area growth of unthinned Sitka spruceis presented in this paper. Additional models express volumeand number of stems as functions of basal area. All models arefound to provide satisfactory fits to the data. It is shownhow such models may be used in the narrow sense of generatingyield tables but in fact possess several advantages over traditionalyield tables.     

Components of Tree Stability in Sitka Spruce on Peaty Gley Soil

The stability of 20 m tall trees was investigated by pullingthem over with a winch. The turning moment at the stem basewas resolved into two components, one due to the applied force,and the other to the horizontally displaced weight of the stemand crown. Vertical displacement of the root-soil system wasmeasured and observations made of the progressive failure ofthe soil around and underneath the root-soil plate. When trees were pulled from the crown region, the soil failedwhen the crown had deflected c. 4 rn horizontally and when theapplied force wasonly about 70% of that required for uprooting.By the time that the maximum turning moment at the stem basedue to the applied force had been reached, many roots had broken,crown deflection was c. 8 m and the deflected weight of thestem and crown made a substantial contribution to the uprootingforces. By repeatedly pulling trees during a sequence of cutting orbreaking the roots and soil, the total resistive turning momentafforded by the anchorage was resolved into the following components:i. soil resistance (the resistance to uprooting afforded bythe soil underneath and at the sides of the root system); ii.the resistance of roots placed under tension on the windwardperimeter; iii. the weight of the root-soil plate; and iv. resistanceto bending at the hinge on the leeside. The importance of these components varied between trees andchanged during the course of uprooting. Soil resistance wasthe largest component in the early stages, but when the turningmoment due to the applied force was maximal, the componentsof anchorage were in the order windward roots < weight <hinge < soil resistance. The major effect of the windwardroots on anchorage in these shallow root systems highlightsthe importance of features which interfere with their lateraldevelopment, such as the furrows produced by spaced ploughing.     

竹材结构的防腐

由于在露天环境中遭遇生物腐蚀,竹秆的持久性差,所以需要采取化学手段增强其耐力.但是它的解剖构造使化学物质难以像木材那样容易进入竹材.竹秆的外部由其表皮保护防水,不像木材那样有径向渗透的途径.而其内部腔隙也有保护性纤维.化学物质的主要渗透途径位于竹秆根部微管束的后生木质部.这些渗透途径分布于横剖面,很不均匀,且少,只占总面积的8～10%,而且在通过竹节时改变方向.由于在采伐时砍伤竹秆,通向导管的细胞腔被堵塞,渗透途径也受影响.周围的薄壁细胞是竹秆组织的主要部分,它们通过微小的纹孔互相连接,只能通过弥散进入.它们所含的淀粉是昆虫和某些真菌的食品.对纤维的保护也有赖于弥散.用化学物质进行保护,对于新鲜的含水量高的竹秆效果最好.就像简单的根部处理,或技术性较强的细胞液改善.新鲜竹秆的薄壁组织和纤维也能通过垂直弥散的方法得到保护.如进行滴渍和浸渍工作,最好在竹材含水分时劈开,因为薄壁组织容易接受弥散.技术措施如竹秆的水分储存和熏蒸的过程,与竹秆的自然结构,尤其是薄壁组织有关.     

Nitrogen Transformations and Decomposition in Litter and Humus from beneath Closed-Canopy Sitka Spruce

Samples of litter and humus from beneath 10 m tall, closed-canopySitka spruce planted on a brown forest soil were incubated underboth field and laboratory conditions to measure mineral nitrogenproduction and carbon dioxide evolution. Mineral nitrogen productionin enclosed samples over 12 months was equivalent to 50 and17 kg N ha^–1 in litter and humus, respectively. Applicationsof fertilizer NPK (200 kg N ha^–1 as ammonium nitrate,100 kg P ha^–1 as unground rock phosphate and 150 kg Kha^–1 as potassium chloride), 18 months previously, decreasedthese values slightly, but stimulated the production of nitratein both litter and humus. Compared with samples kept under laboratoryconditions at 10°C, those incubated in the field at a similarmean temperature released less carbon dioxide and, in the caseof fertilized humus produced smaller amounts of mineral nitrogen.     

Growth Changes in 20-year-old Sitka Spruce Picea sitchensis after Attack by the Green Spruce Aphid Elatobium abietinum

Following a severe attack by Elatobium abietinum (Walker) in1979–80, annual observations were made for 5 years on320 pole-size Sitka spruce in a nitrogen and phosphate experimentlaid out on oligotrophic blanket bog. Leader length was reduced by 25.5 per cent in 1980–81compared with the 3 previous years. This reduction was highlycorrelated with defoliation, being 39.4 per cent for trees thatlost all 1977–79 needles and 8.4 per cent in trees thatlost no needles. There were strong interactions with fertilizertreatment. Defoliated trees continued to grow less well duringthe 5 years of observations and were more likely to go intogrowth check. Early flushing trees suffered significantly less growth reductionfollowing defoliation. The same trees consistently broke budearly over 4 years of observations. Early bud burst was notcorrelated with height, girth or defoliation. No reattack by aphids was observed in the experiment until 1985–86and in this minor infestation the trees previously colonizedwere found to be significantly more likely to be recolonized. A novel measuring-rod for tree height is described.     

Stand Structure in Pine,Spruce and Deciduous Forests: A Comparison Between Finnish and Russian Karelia

This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland.     

Variation of Density and Growth Ring Width in Stems of Sitka and Norway Spruce

The variation with height and radial distance from the pithof basic density and ring width has been determined in stemsof 48-year-old Sitka and Norway spruce planted at two spacingsat Durris, Kincardineshire. The pattern of radial variationof density was broadly similar at all heights: high near thepith, falling to a minimum and then a gradual increase. Themean whole-stem densities were significantly different at thetwo spacings in Sitka but not in Norway spruce. Density at breastheight was inversely correlated with ring width, strongly inSitka but weakly in Norway spruce. The density/ ring width regressionequation for outer wood in Sitka spruce at age 48 differed fromthat at age 31. In Norway spruce a high correlation was foundbetween whole-stem density and the density of rings 16–25at breast height.     

The Growth of Sitka Spruce on Poorly Drained Soils in Northern Ireland

A soil survey of Lisnaskea Forest, Co. Fermanagh, showed thatgrowth of Sitka spruce was far from uniform on areas of apparentlyuniform soil. The relation between soil factors, tree growth,and foliar nutrient status on two blocks of trees growing ongleyed soils was therefore studied. Simple regression showed that tree growth was poor when thelevels of foliar nutrients were low and when there was a matof undecomposed needles on the forest floor. It is thereforeconsidered that lack of organic matter breakdown in the soilis causing poor tree nutrition and growth. Multivariate statistical analysis also showed highly significantregressions between tree growth, level of foliar nutrients,and depth of litter layer. The correlations between soil factorsalone and tree growth were barely significant and the multivariatetechnique did not give an acceptable method of predicting treegrowth from soil measurements. Methods of improving soil conditions are discussed.     

The Use of a Breast-height Core for Estimating Selected Whole-tree Properties of Sitka Spruce

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.