摘要:

The aim of this study was to investigate productivity and wood quality of a typical natural aspen stand(Populus tremulaL.) growing under varying rates of fertilizer addition in South Sweden. The stand developed from root shoots after harvest of a 40‐year‐old aspen stand. Fertilizer was added at rates of 0, 50, 100 and 200 kg N ha−1yr−1. When the experiment started, the trees were 8 years old and until then the mean of annual stem and branch production of the control treatment was 2.8 t d.w. ha−1. During the 3‐year experimental period the production of the control was 3.2 t d.w. ha−1yr−1. Fertilized treatments, however, increased in productivity up to 7.3 t d.w. ha−1yr−1. Growth increase was significant (p<0.05) for all fertilized treatments. Over the whole experimental period, growth could be expressed as a linear function of the N‐fertilization rate. Phosphor‐fertilization did not improve growth. At the end of the experiment the stand had 2.89 trees m−2and then the wood density of stems and branches was 0.35 g cm−3, and the percentage dry matter was 48 %. Wood density and percentage oven‐dry matter were both higher in branches than in stems. The stem biomass averaged 88% of the above‐ground wood biomass.

ISSN:0282-7581    

DOI:10.1080/02827588709382471

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The blister rust of two‐needle pines in Europe is caused by the rust fungus,Cronartium flaccidum(Alb. Schw.) Wint. There are two races of the fungus: One host‐alternating and another pine‐to‐pine race. The latter race is considered to be more common in northern Sweden. The impact of this rust on growth of Scots pine(Pinus sylvestrisL.) was investigated in three selected stands in northern Sweden. Radial stem increment was reduced 40–70% by severe attacks and 20–40% by minor attacks. The reduction of stem volume growth was probably greater. The faster growing trees seemd to be more severely attacked. Trees growing on poor soils appeared to lose almost as much growth capacity from a minor attack as from a severe attack.

ISSN:0282-7581    

DOI:10.1080/02827588709382472

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Barkof Pinus contortaandPinus sylvestrisprovenances, with different attractiveness to voles, were examined with regard to proximate nutrients, certain mineral elements and resin acids.P. contortahad significantly higher concentrations of crude fat (resins), ash, phosphorus and isopimaric acid and less crude fibres. CertainP. contortaprovenances differed significantly in the amounts of resins and nitrogen‐free extractives (soluble carbohydrates). Voles are suggested to preferP. contortagenerally, because of its lower amounts of fibres and certainP. contortaprovenances are assumed to be less preferred due to their high contents of resins.

ISSN:0282-7581    

DOI:10.1080/02827588709382473

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Larvae ofNeodiprion sertiferreared on trees growing in forest soil of low or high values of pH and degree of base saturation developed to adults with dry weights (i.e., fecundity) significantly lower than adults developed on trees growing in soil of intermediate values.

ISSN:0282-7581    

DOI:10.1080/02827588709382474

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Vegetation changes taking place over a period of approximately 30 years in old Scots pine stands growing on dry and subdry heaths(Callunasite type andVacciniumsite type) in southern Finland were examined on 16 permanent sample plots. The coverage ofDicranum polysetumincreased on the average from 11% to 22%, and the frequency from 81% to 97%. The coverage ofPleurozium schreberidecreased from 53% to 41%, and that ofHylocomium splendensfrom 15% to 8%. The coverage of lichens, mainlyCladoniaspecies, decreased on theCallunasite types on the average from 30% to 22%, and the frequency from 91% to 78%. The coverage ofVaccinium vitis‐idaeadecreased on the average from 33% to 20%. The changes inVaccinium myrtillusandCalluna vulgariswere less, and more variable on the different types of site, than those ofVaccinium vitis‐idaea. No marked changes were found in the occurrence of grasses or herbs. The material does not give any definite answers to the question of which factors have brought about the vegetation changes. In additiontonatural succession and annual variation of some species, the effect of air pollution has also been given consideration.

ISSN:0282-7581    

DOI:10.1080/02827588709382475

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A Monte Carlo experiment is carried out on collected data to compare the precision of volume‐ and volume increment estimates. The volume calculation is based on stratification according to diameter. All diameters are known, but only a fraction of the heights. Five different procedures for stratified sampling are compared. To compare the procedures a modified empirical coefficient of variation is calculated. Given sample fraction, there is no difference in CV neither for the volume estimate nor the volume increment estimate between the five sampling procedures. The CV for the volume estimate is varying from 1.7 to 2.0% for 10% sample fraciton, while doubling the fraction gives a CV from 1.2 to 1.5%. Considering the volume increment estimate there is a benefit including sample trees from the previous registration when sampling at the next. When previous sample trees are not retained a CV from 13.2 to 15.4% for 10% sample fraction and from 9.6 to 11.0% for 20% are obtained. The corresponding when previous sample trees are retained are 7.1 to 8.1 % and 4.8 to 5.9%.

ISSN:0282-7581    

DOI:10.1080/02827588709382476

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

After a brief discussion of production functions as models for input/output relations in forest work operations, studies of the cost of machine use are reviewed. It is suggested that the fuel consumption of a forest machine can be used as a parameter for assessing the true, total cost of using a machine, exclusively the wage of the operator. Fuel then is not only an input but also represents all other cost items such as capital (depreciation, interest), repairs and maintenance. This has the advantage that all machines in a system can be aggregated and their costs assessed by an easily quantified parameter. Capital (in the form of machines) in production functions, through which the optimum mix of labour and machines for minimizing the cost per unit of production is determined, can be substituted by fuel. It is also suggested that fuel consumption can be used in management as an aggregate indicator in planning, control, remuneration of work and forecasting.

ISSN:0282-7581    

DOI:10.1080/02827588709382477

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Decomposition of Scots pine needle litter originating from five stands treated with different amounts of nitrogen fertilizer was measured over a 4‐year period in a mature Scots pine forest. The litter types, which differed in initial concentrations of nitrogen, phosphorus, potassium, and sulfur, but not in gross organic composition, were studied with respect to mass loss, ingrowth of total fungal mycelium, and net release of nutrients. During the first year of decomposition, rates of mass loss and ingrowth of fungal mycelium were highest in the nutrient‐rich litter. Phosphorus concentration was found to be the main factor affecting mass‐loss rate, and the rate of fungal ingrowth was positively correlated with initial nitrogen concentration. After this initial period, decomposition rates decreased, and after 4 years, accumulated mass loss and amounts of fungal mycelium were similar in all five litter types. These findings may be due, in part, to a lower rate of lignin decomposition in nitrogen‐enriched litter. Of the elements, potassium and magnesium were most rapidly lost from the litter, and their release was most pronounced during the first year. Calcium release was proportional to the loss in organic matter. Initially, the release of nitrogen and phosphorus was positively related to their concentrations in litter, however, during later stages of decomposition the differences among litter types levelled out. There was a tendency for concentrations of all elements, except nitrogen, in the different litters to approach similar levels as decomposition proceeded. Thus, after 4 years the nutrient composition of the various litter types was very similar, except for higher nitrogen concentrations in the originally most nutrient‐rich litters. The importance of the results in terms of substrate quality in fertilized as well as in non‐fertilized forests is discussed.

ISSN:0282-7581    

DOI:10.1080/02827588709382478

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Two series of experiments withPinus sylvestrisL., 10 and 20 years old, were analysed with regard to genotype‐environment interaction. The series cover a wide range of site conditions with regard to length of growing season, environmental differences within localities and spacing between trees. The genetic material comes from factorial crosses in one of the series and a mixture of full‐sib, half‐sib and provenance material in the other. The origin of the parents is south‐central Sweden, and the trials cover approximately the same geographical range as the parent trees. Despite few replicates and large experimental error, the following conclusions could be drawn:(a)genotype‐environment interaction forPinus sylvestrisin south‐central Sweden seems to be of importance for growth capacity, but the reaction differs between young and old plant stages;(b)the origin of the genetic material, as long as it is restricted to south‐central Sweden, does not seem to have any significant effect on genotype‐environment interaction; (c) a large part of the interaction seems to be explained by a linear relationship between the genotypes and an environmental index.

ISSN:0282-7581    

DOI:10.1080/02827588709382479

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

No differences were found in the frost resistance of the different‐aged (2–7 weeks) germlings of Scots pine. The critical temperature was ‐6°C to —3°C. A temperature of ‐4°C killed half of the germlings and produced damage in one fifth of the surviving seedlings; the needles turned brown and growth ceased. The frost resistance of the previous year's shoots of two‐year‐old seedlings, measured by the impedance method, decreased during the shoot elongation period from — 10°C to — 4°C. Damage to the current shoots during shoot elongation appeared as deformation and discolouration of the needles and abnormal development or death of the apical bud. The results indicate that frost is not the cause of growth disturbances observed in Finnish nurseries.

ISSN:0282-7581    

DOI:10.1080/02827588709382480

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor