摘要:

Models for predicting height and diameter of individual trees in youngPicea abies(L.) Karst. stands were developed. Data collected in a large survey of young forest stands in Sweden (the HUGIN young stand survey) were used in the construction of the models. Models were developed both with and without competition indices included. When constructing the competition indices trees within three metres from the subject tree were regarded as competitors. Functions with competition indices included (distance dependent) will be useful in analyses of the development of stands with different stand structure, whereas functions without competition indices (distance independent) will be useful in systems for long‐term forecasts of yield.

ISSN:0282-7581    

DOI:10.1080/02827588809382510

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Numerical data are presented that support the proposal mentioned as early as the mid‐19th century that aspen roots may remain alive for a long period after the disappearance of parent trees. The mechanism that makes this possible is the ability of this species to form suckers continuously. In stands the bulk of the suckers live a few years and are then replaced by new ones. If conditions allow some suckers may develop into big trees even in old stands. The conclusions are based on material obtained in experiments comprising chemical control of aspen, including different application methods, herbicides, doses and in some cases control treatment (cleaning).

ISSN:0282-7581    

DOI:10.1080/02827588809382511

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Results of branch measurings in unthinned stands of Sitka spruce in Denmark are presented. Three different measures of branch thickness are discussed in relation to visual grading of structural timber. On basis of the average thickest branch 5.0 m above ground it is recommended not to let spacing exceed 1.8x1.8 m‐2.0x2.0 m at establishment. Since Sitka spruce branches react profusely when spacing widens, this is the upper limit, presupposing a no‐thinning regime. With reference to the literature, the same recommendation can be given on basis of machine stress gradings.

ISSN:0282-7581    

DOI:10.1080/02827588809382512

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The principle of comparative work studies was tested in grapple loading by a forest machine simulator. The comparison was between loading in clear‐cutting and thinning conditions. The principle seemed to work in the form presented by Harstela (1975), i.e. that the variation of the relative time expenditure between work methods was smaller than the variation within one method when the same subjects worked by both methods.

ISSN:0282-7581    

DOI:10.1080/02827588809382513

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

An annual survey of damages and growth was conducted two and three years after selective mechanical cleaning in two Norway spruce plantations‐7 and 11–16 years old—and one 11‐year‐old lodgepole pine plantation. The base machine was a modified Bruunett Mini with a rotating disc with two short steel flails, mounted at the tip of the crane. The results show that very few damages were caused by the cleaning device. 5–8% of the seedlings were driven over or otherwise damaged by the wheels and these seedlings show high mortality and great growth reduction. In stands with 1.5–4 m high trees, the trees are often damaged when they are straddled by the machine, which causes growth and quality losses. 14–25% of the undamaged seedlings in Norway spruce stands showed a 25 % annual height growth reduction the first two years after cleaning due to soil compaction and to possible root damage.

ISSN:0282-7581    

DOI:10.1080/02827588809382514

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The chemical fixation ofl5N‐ammonia by partly decomposed Scots pine needle litter was studied. The material had been extracted with water using ultra‐sound treatment. This treatment, together with the addition of HgCl2had killed microorganisms and prevented microbial activity. Fixation of15N‐ammonia decreased with increasing accumulated mass loss and was inversely proportional to concentrations of sulfuric‐acid lignin as well as to concentrations of total nitrogen.

ISSN:0282-7581    

DOI:10.1080/02827588809382515

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

In industry, laser equipment is used in order to accurately measure material thicknesses. For ten days, tests were made in a climate chamber to study whether similar equipment (Lasermike, model 183–00) could be used to measure small changes in stem diameter of a growing spruce. The surrounding air temperature was +10°C and the water vapour pressure 10 hPa on average during six hours of darkness. During the light part of the day the temperature was 18°C and the water vapour pressure 15.5 hPa at a measured irradiance of 60 W/m2and 11.4 hPa at an irradiance of 260 W/m2. The total contribution of the laser instrument and other equipment to the variation in stem diameter was ±3.5 μm. By means of the instrument it was possible to register hydrostatic changes in stem diameter, i.e., shrinking and swelling associated with changes in moisture content in the substrate, with smaller but marked changes depending on shifts between light and darkness and down to the changes in stem diameter caused by small and rapid variations in temperature and air humidity conditions. The true stem diameter growth per day could also be obtained from registrations during periods when the moisture content of the substrate in the pot was kept constantly at field capacity. The growth increased considerably when the irradiance increased. Growth also took place during periods when the stem was shrinking in size. The laser equipment could be rapidly and easily set up for use and was also easily operated. A considerable amount of developmental work is necessary before the instrument can be used in all types of weather in the field.

ISSN:0282-7581    

DOI:10.1080/02827588809382516

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

A comparison was made between green needle litter from Scots pine(Pinus sylvestrisL.) and Norway spruce(Picea abies(L.) Karst.) for the mass loss rate and chemical composition after a one‐year soil incubation period in natural forest stands influenced by urban air pollution. The pollution, which consists mainly of SO2, NOXand heavy metals, did not significantly lower the decomposition rate of pine needle litter in pine stands or spruce needle litter in spruce stands. In the pine needle litter a nearly significant (p<0.1) increase in the release of Mn and a significant enrichment of Fe and Pb were detected. In the spruce needle litter there was a significantly higher release of Mn and a significant enrichment of Fe, Cu and Pb. The urban air pollution had no effects on the content of Ca, Mg, K and Zn in the decomposing pine and spruce needles when the polluted sites were compared to the less polluted controls. The results are also compared with one Scots pine and Norway spruce site which was not exposed to urban pollution. In this comparison the higher release of Mn from the decomposing coniferous needle litter and the enrichment of Fe and Pb into the needle litter of the polluted area becomes even more pronounced.

ISSN:0282-7581    

DOI:10.1080/02827588809382517

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Utilizing the isozyme technique, the genotypes of mature germinable embryos and the corresponding macrogametophytes were classified. The proportion of embryos originating from fertilization with a certain pollen parent was studied following pollination with pollen mixtures or pollen applied on different days. The proportion of fertilized mature embryos arising through self‐pollination was considerably lower than the proportion of selfpollen in the mixture used for pollination. In a mixture with an equal representation of two outcrossing pollens, roughly the same share of fertilized embryos was obtained. Pollinating at different occasions demonstrated that pollination is effective immediately after the opening of the first ovuliferous scales, while supplementary pollination after the peak receptivity is not effective.

ISSN:0282-7581    

DOI:10.1080/02827588809382518

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

An attempt is made to quantify the reduction in zero‐plot frequency which is obtained by better spreading of seeds than what is common. There is presented a simple method based on the mixed binomial model to calculate from experimental data zero‐group frequencies for any number of seeds per spot less than the number in the real experiment. A model describing how the zero‐group frequency depends on the number of spots per plot and number of seeds per spot is developed.

ISSN:0282-7581    

DOI:10.1080/02827588809382519

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor