摘要:

Three experimental trials established from 1956 to 1959 on virgin oligotrophic peatland were selected for case studies on net present value, internal rate of return (IRR) and cost effectiveness (CE). Critical analyses of biological parameters showed that site indexes determined by top heights gave serious under‐estimates of actual timber production. The stands obviously represent a subuniverse with higher pole stage stand density and higher diameter/ height ratios than defined by the growth tables. Available models on biomass production were also evaluated.

ISSN:0282-7581    

DOI:10.1080/02827589409382816

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Investigations concerning the drying properties (twist, longitudinal shrinkage, bow and spring) are made on boards from four young Norway spruce(Picea abies)and Sitka spruce(Picea sitchensis)stands grown on fertile soils. Initial spacing has been up to 2.5 × 3 m and thinning intensity has been heavy. Small, average and large trees from each stand were sampled, in total 78 trees sawn into 214 boards. The boards consist mainly of wide‐ringed juvenile wood. Norway spruce and Sitka spruce of this material show only small differences in drying properties and they are accordingly analysed together. The boards are prone to severe twisting causing low‐grade boards and a high percentage of rejection when visually graded. The twist is induced by spiral grain and is most pronounced in small‐dimension boards sawn near the pith. Methods for reducing twist are discussed. Longitudinal shrinkage does not give problems for the use of the boards. Bow and spring give problems only for part of the boards, namely the very small dimensions from near the pith.

ISSN:0282-7581    

DOI:10.1080/02827589409382817

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Temporal patterns of changes in nutrient dynamics were followed in decomposingPicea abiesneedle litter in a long‐term optimum nutrition field experiment using N and P fertilizer. Nutrient‐poor brown and nutrient‐rich green needle litter were incubated in both control plots and fertilized ones.

ISSN:0282-7581    

DOI:10.1080/02827589409382818

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Decomposition of organic matter in forest soils controls mineralization of nutrients. The decomposition is to a large extent controlled by climatic and soil conditions. Four different soil treatments of water and nutrients were applied to a Norway spruce (Picea abies)stand in Denmark, and the relative changes in decomposition rate were quantified by the cotton strip assay. Additions of water and nutrients to the soil increased the decomposition of the cotton strips significantly, especially in the deeper soil layers. Reduced water addition during the summer, thereby creating ‘summer drought’, caused no changes in the decomposition compared to an untreated control situation, but the spatial variability in the decomposition within the treatment plot was strongly increased. The decomposition of the cotton strips decreased linearly with the soil depth (1st order).

ISSN:0282-7581    

DOI:10.1080/02827589409382819

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Path analysis was used to study shoot elongation of Scots pine seedlings grown under six relative mineral nutrient addition rates (Ra). The shoot length is composed of two growth components: number of stem units (NSU) and mean stem unit length (MSUL). Under suboptimal conditions (Ra = 1% and 2%) most variation in shoot length (LEN) was due to variation in MSUL, and the correlation between the two components was negative. Under optimal conditions (Ra = 3% and 4%), NSU and MSUL contributed equally to the total length variation and the correlation between them was positive. Under supraoptimal conditions (Ra = 5% and 6%), the number of stem units had the greatest effect on shoot length variation and the correlation between growth components was negative. A simple allocation model was used to help interpret the changes in sign of correlation coefficient along the nutrient gradient. The model correctly predicted the sign of the correlation but not its magnitude.

ISSN:0282-7581    

DOI:10.1080/02827589409382820

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Deposition of protons, nitrate and sulphate have caused a decrease in soil pH and base saturation in southern Scandinavia. Floral changes have been suggested to be due to this deposition. This study was made to test if differences in nitrate assimilation capability between plants could be one of the reasons behind reported changes in the flora. Current and maximally induced nitrate reductase activity (C‐NRA and MI‐NRA, respectively) were measured in four beech forest field‐layer species, which have been reported to behave differently with respect to acid rain. The study was conducted at four sites of different soil quality (pH). There were considerable differences between the species as regards both C‐NRA and MI‐NRA. For two of the studied species,Galium odoratumandStellaria nemorum,the gap between C‐ and MI‐NRA was relatively small but forMercurialis perennisandOxalis acetosella,this gap was larger. A small difference between C‐ and MI‐NRA should indicate that a larger portion of the available resources for nitrate reduction is already used. The concentrations of soluble carbohydrates were correlated with the MI‐NRA after leafing of beech, while before leafing no such effect could be detected. It can be concluded that the light environment has a considerable effect on the nitrate nutrition of field‐layer plants. Apparently, some species receive as much nitrate as they can reduce. Fertiliser experiments are needed to test if higher addition rates are harmful to them.

ISSN:0282-7581    

DOI:10.1080/02827589409382821

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Damage induced by wind and snow was examined in an experimental series with thinning and fertilisation established in 34–58 years old Scots pine(Pinus sylvestrisL.) stands in northern Sweden during the period 1969–83. The experiment contained six treatments and 23 replications. The treatments were 25% and 60% thinning from below, 25% thinning from above, 30% thinning from below combined with N and NP fertilisation. Percentages represent basal area harvested at the first thinning. Differences in damage level were examined at the first reinventory, 4–8 years after thinning.

ISSN:0282-7581    

DOI:10.1080/02827589409382822

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Development of growth and stand structure was studied in four spacing experiments with Norway spruce(Picea abies(L.) Karst.) in northern Sweden. The sites were considered as poor for Norway spruce. Height and diameter growth were significantly lower in the densest spacings compared to the most widely spaced stands. In the dense spacings the relative growth rates of both small and large trees were reduced. Height‐diameter ratio was not influenced by spacing. Stand structure (Gini‐cooerficient and skewness) was not significantly affected by spacing. It was concluded that the major limiting factor for growth in the dense spacings was not light but mineral nutrients and/or water. The results also support the hypothesis of unchanged or decreased inequality when competition acts on all trees equally or in proportion to their size.

ISSN:0282-7581    

DOI:10.1080/02827589409382823

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Growth comparisons of different mixtures of Scots pine(Pinus sylvestris)and Norway spruce(Picea abies)were based on spatial individual‐tree growth models in which the competition by pines and spruces was accounted for by separate competition indices. The study material represented growing sites of medium fertility. The models indicated that a spruce competitor decreases the growth rate of another spruce clearly more than a pine competitor. The diameter growth of a pine was affected slightly more by another pine than by a spruce of the same size and at the same proximity. According to growth and thinning simulations conducted, a conifer mixture may have a volume increment 10–15% higher than a pure pine or spruce stand with the same stand age and basal area.

ISSN:0282-7581    

DOI:10.1080/02827589409382824

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The hypothesis tested was that it should be possible to predict maximum attainable level of anatomical maturity ofPinus sylvestrisL. seeds, and thus the germination capacity, using only one x‐ray based sample value of anatomical potential (Ap) in combination with a time function. This sample should be taken after commencement and before cessation of embryo growth. Since this predictive model should be independent of temperature, it was validated by repeatedly collecting seeds from several localities with presumably different temperatures during ripening. Although the temperature sums differed between localities, the rate of increase in Ap was almost identical in August. According to multiple linear regression analysis, the highest coefficient of determination (0.81) was achieved if Ap values from collections made in August were used in the regression. The average absolute deviation for the different localities between actual and predicted maximum Ap was 2%, and the highest deviation 7.2%. Thus, it should be possible to make a good prediction of the maximum germination capacity as early as in August. The practical consequence of this is that cone collection and possible artificial ripening could be started very close to the optimal time. Furthermore, soil scarification could be done in seed tree stands before seedfall when high seed quality is predicted.

ISSN:0282-7581    

DOI:10.1080/02827589409382825

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor